JPH10222131A - Projection type picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a picture display suitable for an input video source by controlling a light emitting characteristic in accordance with picture information of picture light to be written in a spatial optical modulation element. SOLUTION: The device is composed of a light emitting characteristic control part 1 for controlling the light emitting characteristic, a driving waveform generating part 2 for driving the spatial optical modulation element 101, a cathode ray tube 108 as a picture light source, a write lens 110, the spatial optical modulation element 101, a light source 111, visualizing means 114 and a projecting lens 115. Since different display performance is required for the time of a computer display of characters and graphics and for the time of a video display of a motion picture, etc., respectively, the light emitting characteristic control part 1 and the driving waveform generating part 2 are controlled in response to this required performance so that an optimum light emitting characteristic is selected to perform an optimum picture display. A control signal is inputted to an input terminal of the light emitting characteristic control part 1 for the purpose of performing two-dimensional gamma correction, and the light emitting characteristic is corrected in each area. In addition, by controlling a driving waveform as well as the light emitting characteristic, the light emitting characteristic is controlled with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a projection type image display apparatus using an optical writing type liquid crystal light valve for displaying a large screen of high quality.

[0002]

2. Description of the Related Art Conventionally, since it is difficult to increase the size of a direct-view display, a projection type image display using a liquid crystal display such as a CRT or a liquid crystal panel driven by a thin film transistor has been proposed. It is difficult to achieve both high resolution and high resolution.

Therefore, a projection type image display apparatus using a light-writing type spatial light modulation element in which a photoconductive layer and a light modulation layer are combined is disclosed in JP-A-4-338924. .

FIG. 41 shows a general structure of a conventional spatial light modulator. A spatial light modulator 101 is composed of glass substrates 102, 10 'having conductive transparent electrodes 103, 103'.
2 ′ has a structure in which the photoconductive layer 104, the light reflecting layer 105, and the light modulating layer 106 are sandwiched. The photoconductive layer 104 between the light reflecting layers 105 is etched to form a light absorbing layer 107.

In the conventional spatial light modulation element 101, when writing light is input to the photoconductive layer 104, the voltage applied to the light modulation layer 106 changes according to the two-dimensional light intensity distribution, and the light modulation Layer 106 switches. As a result, the read light is modulated and is output after being reflected by the light reflection layer 105. The light-absorbing layer 107 has a strong read light,
This is to prevent input to the photoconductive layer 104 during the period from 05.

FIG. 42 shows a conventional projection type image display device using this spatial light modulator. As the image source 108, a CRT, a TFT-LCD, or the like is used. The output image is formed as writing light on the photoconductive layer 104 by the writing lens 110, so that the spatial light modulator 101 is formed.
Perform image input to Readout light 11 from light source 111
2 is incident from the light modulation layer 106 side of the spatial light modulation element 1011, is modulated by the light modulation layer 106,
After being reflected by 5, the light passes through the light modulation layer 106 again and is output. The output light 113 is visualized through a visualizing means 114 and is enlarged and projected on a screen 116 by a projection lens 115.

The photoconductive layer 10 of the spatial light modulator 101
4 is made of amorphous silicon having a nip structure, and a liquid crystal material such as a nematic liquid crystal or a ferroelectric liquid crystal is used for the light modulation layer 106. A polarizing beam splitter is used as the visualizing unit 114, and a metal halide lamp, a xenon lamp, or the like is used as a light source.

In such a projection type image display device, it is possible to display a high-intensity and high-resolution image by increasing the brightness of the light source and increasing the resolution of the image input means to the spatial light modulator. Become.

Next, a conventional driving method of the spatial light modulator will be described. FIG. 43 shows a general driving voltage waveform of the spatial light modulator. The drive voltage includes an erase period and a write period, and is applied to the entire surface of the spatial light modulator in synchronization with the vertical synchronization signal of the input video signal. The spatial light modulator modulates the readout light according to the light intensity input during the writing period and outputs the light. During the erasing period, initialization is forcibly performed regardless of the presence or absence of writing light, and the output becomes zero.

[0010]

However, in the above-mentioned conventional configuration, it is required to improve the uniformity, gradation, and the moving image display performance with little afterimage, in addition to the brightness and resolution.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention provides a projection type image display device using a light-writing type liquid crystal light valve and the like, which greatly improves moving image display performance such as uniformity and gradation, as well as high brightness and high resolution. It is an object of the present invention to provide a projection type image display device such as a light-writing type liquid crystal light valve that can be used.

[0012]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention controls an emission characteristic according to image information of image light written to a spatial light modulator, and displays an image suitable for an input video source. Is provided.

Further, according to the present invention, a driving voltage is generated in accordance with the vertical scanning frequency of image light written to a spatial light modulation element, and the light emission characteristics always having the black level as the origin even when the vertical scanning frequency changes. It is provided for realizing.

Further, according to the present invention, a vertical scanning frequency of an input signal is converted to a specific scanning frequency by scanning conversion, image light writing is performed on a spatial light modulation element, and a driving waveform to the spatial light modulation element is changed to the image light. And applying a driving voltage synchronized with the vertical scanning frequency of

Further, according to the present invention, the pixel of the spatial light modulator
It is intended to remove moire generated due to interference between the scanning lines of the RT.

The present invention also relates to a CRT for a spatial light modulator.
It is intended to control the Gaussian distribution of the writing image light to improve the sharpness.

The present invention further comprises calculating a conversion coefficient for gamma correction according to the vertical scanning frequency of the image light, and controlling the light emission characteristics of the image light with the conversion coefficient.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides an image light generating means for generating image light to be written on a spatial light modulator, a driving waveform applied to the spatial light modulator in accordance with image information of the image light, and an image. It is characterized by having light emission characteristic control means for controlling light emission characteristics by controlling light, and by performing image display suitable for an input video source, high brightness and high resolution as well as uniformity and This has the effect of realizing a projection-type image display device capable of greatly improving display performance such as gradation.

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram of a projection type image display device according to the present invention. In FIG. 1, reference numeral 1 denotes a light emission characteristic control unit for controlling light emission characteristics, and 2 denotes a spatial light modulator. For driving the image, a cathode ray tube 108 (hereinafter abbreviated as CRT) as an image light source, a writing lens 110, a spatial light modulator 101, and a light source 111
, A visualization unit 114, and a projection lens 115, such as a light-writing type liquid crystal light valve.

The operation of the projection type image display apparatus of the present embodiment configured as described above will be described below with reference to the emission characteristic diagram of FIG.

In general, the required display performance differs between when a computer displays characters and graphics and when a video such as a moving image is displayed.
And the drive waveform generator 2 to select the optimum light emission characteristics and perform the optimum image display. In the case of displaying an image in which gradation and color reproducibility are required, the emission characteristics are as shown by the broken line in FIG. , And realizes an optimal image display.

Next, in order to explain the necessity of controlling the light emission characteristics (hereinafter abbreviated as γ characteristics) in a projection type image display device such as a liquid crystal light valve, the operation characteristic diagram of FIG. 3 will be used.

(1) γ characteristics of liquid crystal and its unevenness (2) Unevenness of time aperture ratio (3) Peripheral light amount ratio of writing lens and CRT (writing system) (4) Peripheral light ratio and projection angle of projection system For example, shading by means of such a method can be considered. Hereinafter, each of them will be described.

(1) γ Characteristics of Liquid Crystal and Its Unevenness The γ characteristics of the liquid crystal will be described with reference to FIG.

In FIG. 3, the horizontal axis represents the level of the video signal input to the system shown in FIG. 1, and the vertical axis represents the output of the system when no uniformity correction is performed, that is, the illuminance on the screen in this case. The reference numeral 180 indicates the γ characteristic of a normal pixel. Generally, liquid crystal has the same tendency irrespective of the material, but here, ferroelectric liquid crystal will be described. The distribution of the reflectance (transmittance) caused by the liquid crystal alignment unevenness or other factors is eventually recognized as luminance unevenness or color unevenness, but it can be interpreted that the γ characteristic has a spatial distribution.

The causes of this spatial distribution include uneven alignment of liquid crystal molecules and insufficient application of writing and reset voltages. The γ characteristics of pixels recognized as uneven are roughly divided into those shown in FIG. 181 and 182
become that way. As is clear from the figure, 181 is obtained by parallel movement and scaling in the input signal direction (horizontal direction), and 182 is obtained by parallel movement and scaling in the screen illuminance direction (vertical direction). Regarding the unevenness of the liquid crystal, it can be interpreted that the pixels having the characteristics such as 181 and 182 are arbitrarily distributed.

(2) Unevenness of Time Aperture Ratio The display system shown in FIG. 1 requires a concept of a time aperture ratio unlike a general direct-view type liquid crystal display or the like. This time aperture ratio will be described with reference to FIG.

In the case of the ferroelectric liquid crystal used in the embodiment of the present invention, the liquid crystal rotates at the same time as being written by light,
Although white display is performed, the state of the liquid crystal is maintained until reset is applied even when the writing light is lost. This characteristic is generally called the ferroelectric liquid crystal memory effect.
Due to this characteristic, the time aperture ratio is spatially different due to the difference between the reset and write timings, and appears as uneven brightness. Further, the rotation angle and the rotation speed of the liquid crystal change depending on the intensity of the light intensity of the CRT, and the gradation can be expressed.

FIG. 4 explains the system of the gradation expression. 185 is 1 in 1 field period
The reset pulse 186 applied once is the light emission characteristic of the CRT. The horizontal axis represents time, the vertical direction represents light intensity, and decreases exponentially with time. Reference numerals 187 to 189 denote light intensities on the screen, which correspond to the case where the light intensity of the CRT is weak, the case where it is intermediate, and the case where it is strong, respectively.

FIGS. 5 (a), (b) and (c) show the upper part (when writing immediately after the reset pulse) and the middle part (about half of one vertical period from the reset pulse to writing) on the screen, respectively. Time) and bottom (when reset immediately after being written). Regarding the upper part (a) of the screen, 190 is a reset pulse, 191 is a light emission characteristic of a CRT, and the vertical direction shows light intensity, which decreases exponentially with time.
Reference numeral 192 denotes the light intensity on the screen. Since the light is written by the light from the CRT immediately after the reset pulse, the light continues to light for almost one field period.
In this case, the time aperture ratio is almost 100%. What is actually perceived as brightness by human eyes is not the peak value of the light intensity but the time average, and the area of the hatched portion in FIG. This area ratio can also be called a time aperture ratio.

The middle part (b) of the screen will be described. 193
Is a reset pulse, 194 is the light emission characteristic of the CRT, 195
Is the light intensity on the screen, which is written almost in the middle of one field. In this case, the liquid crystal performs white display simultaneously with writing as in the case of (a), but the period until the reset pulse is about half as compared with the case of (a). That is, the time aperture ratio decreases and the image becomes darker.

Next, in the state of the lower part (c) of the screen, a reset pulse is applied immediately after optical writing by the CRT. In such a case, even if the liquid crystal is reset, C
Due to the afterglow characteristic of the RT, the state is written in the next field, and the liquid crystal slightly rotates. Of course, CR
Since the intensity of the afterglow of the next field differs depending on the light intensity of T, the light intensity on the screen changes.

For the reasons described above, the time aperture ratio becomes uneven at the period of the vertical frequency, and the γ characteristic changes. FIG. 6 shows the resulting γ characteristic, in which the horizontal axis represents the level of the input signal and the vertical axis represents the time aperture ratio. . Top 1 from top of screen
99, the region 200 from the top to the middle, the middle 20
1. γ characteristics for the lower part 202. As a result, the γ characteristics of 199, 201, and 202 can be approximated by parallel movement and enlargement / reduction in the screen illuminance direction (vertical direction). On the other hand, γ from the top to the middle of the screen
The characteristics can be approximated by parallel movement and scaling in the input signal direction (lateral direction).

(3) Peripheral Light Amount Ratio of Writing Lens and CRT (Writing System) Generally, the periphery of a lens or CRT becomes darker than the center of the screen. Here, γ caused by the peripheral light amount ratio of the writing system.
Think about characteristics. FIG. 7 shows the center 110 and the periphery 1 of the screen.
11 is a γ characteristic curve for No. 11, which assumes that there is unevenness only in the writing system and that there is no unevenness in other liquid crystal devices and the projection optical system. How to read FIG. 25 is FIG.
1, but the intensity of the writing light itself is uneven, and consequently the light intensity on the screen can be approximated by scaling in the input signal direction (lateral direction).

(4) Shading by the Peripheral Light Ratio of the Projection System and the Variation of the Projection Angle Next, consider the unevenness and shading of the projection optical system. FIG. 8 is a γ characteristic curve for the center 212 and the periphery 213 of the screen, assuming that there is unevenness only in the projection system and no unevenness in the other liquid crystal devices and writing systems. In this case, contrary to the above (3), since the light intensity of the writing light has no unevenness and the unevenness of the projection system after the device, it can be approximated by scaling in the screen illuminance direction (vertical direction).

Here, supplementarily, the γ characteristic on the screen is a combination of the γ characteristic of the liquid crystal itself described above and the γ characteristic caused by the time aperture ratio. Will be affected.

As described above, the spatial distribution of the light emission characteristics and the cause of the uneven brightness have been described.

Next, in order to describe the operation of the light emission characteristic control in detail, a circuit configuration diagram of the light emission characteristic control section 1 of FIG. 9 and operation characteristic diagrams of FIGS. 10 and 11 will be used.

FIG. 9 shows an example of a gamma correction circuit. When the input signal level rises, the diodes D1 to D2 are sequentially turned on, the load resistances of the transistors are connected in parallel in the order of R1 to R3, and the load resistance is reduced according to the input level. In this way, a polygonal line approximation of the gamma characteristic is performed. Further, a control signal for performing two-dimensional gamma correction is input to the input terminal 3, and the light emission characteristics of each region are corrected. As shown in FIG. 10, the input / output characteristics of the gamma correction circuit at this time are the characteristics before correction, and the solid lines in FIG. 10 are the characteristics after correction, and the gamma characteristics are dynamically controlled as shown in FIG. The pre-correction light emission characteristic shown by the broken line is aligned with the characteristic shown by the solid line in FIG.

Therefore, before the correction shown by the broken line in FIG. 11, the light emission characteristics at the time of computer display such as the characters and figures of the solid line in FIG.
After the correction shown by the solid line in FIG. 11, the light emission characteristics at the time of displaying the image shown by the broken line in FIG. 2 are obtained, and the light emission characteristics can be easily controlled only by controlling the gamma correction.

Further, correction data corresponding to the two-dimensional spatial position is created by a digital method, and the gamma characteristic is dynamically changed by controlling the polygonal line set value of the polygonal line gamma correction circuit using the correction data. Needless to say, highly accurate gamma correction can be realized.

Next, in order to describe a method of generating a drive waveform, a detailed block diagram of the drive waveform generator 2 in FIG. 12 and an operation waveform diagram in FIG. 13 will be used.

The vertical synchronization signals shown in FIGS. 13A and 13D are supplied to the deflection circuit 4, and the deflection yoke of the CRT is supplied to the deflection yoke of FIG.
A deflection current synchronized with the vertical synchronization signal shown in 3 (b) and (e) flows. The vertical synchronizing signal synchronized with the deflection current is supplied to a write / erase voltage setting circuit 47 for setting a write / erase voltage, then amplified by an amplifier circuit 48 and applied to a spatial light modulator for each color. Therefore, FIG.
At the time of the vertical scanning frequency (fv = 60 Hz) shown in FIG.
The driving waveform shown in FIG. 13C has the vertical scanning frequency (fv = 120 Hz) shown in FIG. 13D, and the driving waveform shown in FIG. 13F, that is, the driving waveform synchronized with the vertical synchronizing signal is the spatial light modulator 111. Is applied to FIG. 13G shows FIG.
As shown in the enlarged view of the drive waveform in (f), the drive waveform has three parameters: pulse width, erase voltage, and write voltage. When the pulse width is wide, when the erase voltage is high, and when the write voltage is high, the brightness is dark.

Therefore, by controlling the driving waveform together with the light emission characteristics, it is possible to control the light emission characteristics with higher precision especially when multi-scan is supported.

Next, a light emission characteristic diagram shown in FIG. 14 will be used to describe in detail a method for realizing the optimum display performance at the time of various video sources.

At the time of displaying an image such as a high-definition television or a current TV moving image, faithful display performance such as contrast, resolution, gradation, and color reproducibility is required. Therefore, as shown by the broken line in FIG. 14, the black light level of the spatial light modulation element is set so that a faithful gradation and color reproducibility from white to black can be expressed. The use state uses a high temporal aperture ratio to express a sharp and sharp image.

On the other hand, when displaying characters and figures on a computer, the sharpness of the characters over the entire screen is required. Therefore, as shown by the solid line in FIG. 14, the light emission characteristics in a narrow range are set so as to be set to be the black level of the image light on the CRT and to compress the black to improve the average luminance. Uses a low temporal aperture to express images with greatly improved sharpness of characters.

As described above, according to the present embodiment, the light emission characteristics are controlled in accordance with the image information of the image light written to the spatial light modulator, and the optimum display performance (corresponding to various signal sources) is obtained. Brightness / gradation / sharpness).

(Embodiment 2) Next, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 15 is a block diagram of a projection type image display device according to the second embodiment. In FIG. 15, the same portions as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted.

In FIG. 15, reference numeral 8 denotes a CRT driving unit which comprises the video circuit 7 and the deflection circuit 4 and drives the CRT 108 to generate image light. 9 denotes an erasing period in synchronization with a vertical synchronizing signal from the deflection circuit 4. This is a drive waveform generator for generating a drive voltage having a write period.

First, in a projection type image display device such as a liquid crystal light valve, an operation characteristic diagram of FIG. 16 will be used to explain a change in gamma characteristic.

FIG. 16 shows the gamma characteristics of the illuminance on the screen when the vertical scanning frequency of the drive waveform generator 9 is changed. As shown in the figure, it can be seen that the illuminance decreases in inverse proportion to the vertical scanning frequency. It can also be seen that the higher the vertical scanning frequency, the more linear the gamma characteristic. This factor is, as described in the first embodiment, due to the use of a CRT phosphor having a long afterglow characteristic in order to ensure uniformity.

Next, in order to describe a method of generating a drive waveform, a detailed block diagram of the drive waveform generator of FIG. 17 and an operation waveform diagram of FIG. 18 will be used.

The vertical synchronizing signals shown in FIGS. 18A and 18D are supplied to the deflection circuit 4, and the deflection yoke of the CRT shown in FIG.
A deflection current synchronized with the vertical synchronization signal shown in 8 (b) (e) flows. A vertical synchronizing signal is also input to the CPU 10, a vertical scanning frequency is detected, and this detection signal is supplied to the 周 frequency dividing circuit 11. In the 1/2 frequency dividing circuit 11, the driving frequency for driving the spatial light modulator 101 is determined based on the vertical synchronizing signal synchronized with the input and the detection signal from the CPU 10. The vertical scanning frequency shown in FIG.
At 0 Hz, the frequency as it is without performing 1/2 frequency division is
When the vertical scanning frequency shown in FIG.
The frequency obtained by performing the 1/2 frequency division is output. The signal from the 1/2 frequency dividing circuit 11 is supplied to a write / erase voltage setting circuit 5 for setting a write / erase voltage, then amplified by an amplifier circuit 6 and applied to a spatial light modulator for each color. You. for that reason,. When the vertical scanning frequency shown in FIG. 18A is 60 Hz, the driving waveform shown in FIG.
When the vertical scanning frequency shown in (d) is 120 Hz, FIG.
The drive waveform shown in (f) is applied to the spatial light modulator 101.

By performing the above driving method,
A high-brightness projection-type image display device can be realized by changing the light emission characteristic shown by the dashed line at 120 Hz in FIG.

When importance is placed on gradation and uniformity using the characteristics shown in FIG. 16, this can be easily realized by setting a high vertical scanning frequency and driving the spatial light modulator.

Next, in order to describe in detail a method of realizing the light emission characteristic with the black level as the origin even when the vertical scanning frequency changes, the characteristic diagram of FIG. 17 is used. When the image writing is 60 Hz and the driving waveform to the spatial light modulator is also 60 Hz in the solid line in FIG. 17, the image writing is 120 Hz and the driving waveform is 60 Hz in a half cycle in the broken line in FIG.
In particular, as shown in FIG.
Blackening occurs due to the periodicity. Therefore, as shown in an enlarged view of the driving waveform in FIG. 18 (g), by changing the conventional write voltage VW1 to VW2,
The light emission characteristic indicated by the broken line in FIG. 19 coincides with the light emission characteristic at 60 Hz indicated by the solid line.

As described above, by always realizing the emission characteristics with the black level as the origin, gamma and uniformity correction based on the pedestal potential in the video signal can be realized, so that a system with good chromaticity tracking can be easily realized. Can be realized.

Further, according to the present invention, a driving voltage is generated in accordance with the vertical scanning frequency of image light to be written into the spatial light modulator, and even when the vertical scanning frequency changes, the light emission characteristics always having the black level as the origin even when the vertical scanning frequency changes. It is provided for realizing.

As described above, according to the present embodiment, the drive voltage is generated by changing the frequency of the drive waveform applied to the spatial light modulator in accordance with the vertical scanning frequency of the image light, so that the black level is always maintained. By setting the light emission characteristics to the origin, good gradation and color reproducibility can be realized.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to the drawings.

FIG. 20 is a block diagram of an image correction device of a projection type image display device according to the third embodiment.

In FIG. 20, the same portions as those in the first and second embodiments are denoted by the same reference numerals, and detailed description is omitted.
In FIG. 20, reference numeral 12 denotes a scan converter for converting a vertical scanning frequency of an input signal into a specific scanning frequency, reference numeral 19 denotes a drive waveform generator for generating a drive waveform applied to a spatial light modulator, and reference numeral 13 denotes a short afterglow. CRT.

Next, in order to describe the scan conversion operation in detail, a detailed block diagram of the scan conversion unit 12 in FIG. 21 and an operation characteristic diagram in FIG. 22 will be used.

The input signal is supplied to an A / D converter 14 and a clock generation circuit 15 and is A / D-converted by a clock signal from the clock generation circuit 15. The CPU 17 is also supplied with a synchronization signal, and stores parameters for performing signal discrimination and scan conversion at the same time. The digital signal from the A / D converter 14 is supplied to a scan conversion circuit 16 and converted into a signal having a specific vertical scanning frequency based on a control signal from the CPU 17. The scan-converted signal from the scan conversion circuit 16 is D / A converted by a D / A converter 18 to be converted into an analog signal, and is converted into an analog signal.
0).

FIG. 22 shows a high vision signal (fh = 33.75 kHz).
(z, fv = 60Hz) The gamma characteristic when the input signal is converted to each vertical scanning frequency of 40 to 150Hz is shown, so that high brightness can be easily realized at low frequency and uniform image display can be easily realized at high frequency. You can see what you can do.

Therefore, the required display performance is different between the display of a computer such as a character or a figure and the display of a video such as a moving image. Therefore, only selecting the vertical scanning frequency in accordance with the required performance will optimize the image display. It can be carried out.

Next, in order to describe in detail the method of reducing the afterimage, a CRT afterglow characteristic diagram of FIG. 23 and a characteristic diagram of FIG. 24 will be used. In the first and second embodiments, the long afterglow CRT shown in FIG. 23 is employed in order to ensure uniformity. However, in the present invention, the scan conversion is performed by converting the signal into a signal having a high vertical scanning frequency. , It is possible to use a short afterglow CRT whose afterglow is short enough for the field period,
The afterimage can be reduced. FIG. 24 shows a characteristic diagram of the unevenness of the time aperture ratio. The vertical axis represents the time aperture ratio, and the horizontal axis represents the position on the screen in the vertical direction (up to center to down), with the signal APL changed. is there. FIG. 24A shows a case where the long afterglow CRT shown in FIG. 23 is used as in the first and second embodiments, and FIG. 24B shows a case where the medium afterglow CRT is used. Is the unevenness of the time aperture ratio when a short afterglow CRT is used. Conventionally, a long afterglow CRT is used in terms of gradation and uniformity.
Was adopted. FIGS. 24A to 24C show the case where the vertical scanning frequency is 60 Hz.

In the present invention, the vertical scanning frequency is set to, for example, 1
By performing scan conversion to a signal of 20 Hz and driving the spatial light modulator with a drive waveform synchronized with the vertical scanning frequency, even when a medium to short afterglow CRT is used, FIG.
As shown in FIG. 23 (d), it is possible to realize the same gradation property as that of FIG. 24 (a), and to greatly reduce the afterimage from several tens of ms to several ms as shown in the afterglow characteristic of FIG.

As described above, according to the present embodiment, image light to be written to the spatial light modulator is generated by a converted signal obtained by scan-converting the vertical scanning frequency of an input signal to a specific scanning frequency, and By applying a drive voltage synchronized with the vertical scanning frequency to the spatial light modulator, it is possible to realize image display with good uniformity for various signal sources.

(Embodiment 4) Next, a fourth embodiment of the present invention will be described with reference to the drawings.

FIG. 25 is a block diagram of a projection type image display device according to the fourth embodiment. In FIG. 25, first to third
The same reference numerals are given to the same portions as those of the embodiment, and the detailed description is omitted. In FIG. 25, 23 is a spatial light modulator having a pixel structure, 22 is a moiré removal signal generator for generating a signal for removing moiré, and 21 is a vertical deflection of a moiré removal signal from the moiré removal generator 22. A deflecting circuit 20 for supplying a circuit to control the scanning line interval is a CRT driving unit 20 including the moiré removal signal generating unit 22, the deflecting circuit 21, and the video circuit 7.

First, the spatial light modulator 2 having a pixel structure
In order to describe the operation of removing the moire generated in the pixels of the spatial light modulation element and the scanning line interval of the CRT in a projection type image display device such as a liquid crystal light valve using the liquid crystal light valve 3 shown in FIG.
6 and the scanning line diagram of FIG. 27 are used. FIG.
(A) is an enlarged view showing a structure of a spatial light modulation element composed of, for example, 3000 pixels in the horizontal direction and 2000 pixels in the vertical direction,
FIG. 26B is an enlarged view of the writing image light constituted by the scanning lines on the CRT tube surface. When writing is performed on the spatial light modulation element 23 having the pixel structure with the image light composed of the equally-spaced scanning lines shown in FIG. 27A, higher-order moiré due to interference between the pixels and the scanning line interval. Will occur. Therefore, as shown in FIG. 27B, by superimposing the moire removing signal on the vertical deflection circuit and the vertical convergence circuit to change the scanning line interval, the scanning line pitch is particularly widened (the number of scanning lines is small). It is also to remove moire at the time of signal source.

Next, in order to explain the operation of the moiré removal, the moiré removal signal generator 22 and the deflection circuit 2 shown in FIG.
1 and the operation waveform diagram of FIG. 29 and the operation diagram of FIG.

The horizontal synchronizing signal shown in FIG.
The vertical synchronizing signal (b) is supplied to the CPU 25 and the flip-flop circuit (FF) 24, and the CPU 25 detects the scanning frequency of each synchronizing signal and performs signal discrimination.
In FIG. 29, a signal having a duty ratio of 50% shown in FIG. The output from the FF 24 is switched by the switching circuit 26 in accordance with the result of the signal discrimination from the CPU 25.
At the time, the waveform shown in FIG. Switching circuit 2
6 is supplied to a gain control circuit 27, and the CP
From the detection data of the scanning line interval from U25, FIG.
The gain is controlled in the direction of the arrow shown in FIG. 3 to determine the amount of change for controlling the scanning line interval. The moiré removal signal from the gain control circuit 27 and the convergence correction waveform from the vertical convergence waveform creation circuit 28 are added by an adder 29,
This addition signal drives the convergence yoke 31 through the vertical convergence output circuit 30. By performing the moiré removal in this manner, as shown in FIG. 29 (f), the scanning line spacing on the screen is equal to P3 before the moiré removal, whereas after the moiré removal. In this case, the scanning line interval changes from P1 to P2, and moire is removed.

FIG. 30 shows the relationship between the number of scanning lines and the scanning line interval of each signal source and the moiré operation. As shown in FIG. The moire is removed by wobbling the scanning line interval by an amount that minimizes high-order moiré.

Also, because of the pixel structure, the vertical deflection circuit S
A change in luminance occurs due to the movement of the scanning line in terms of stability such as / N degradation. However, if the amount of change in the vertical deflection current is detected, and the amount of change is added to the moire removal signal, correction is performed. Further, more stable image display can be performed.

As described above, according to the present embodiment, the moire generated by the interference between the scanning line and the pixel at the time of light writing on the CRT by the spatial light modulator having the pixel structure is controlled by controlling the scanning line interval. By removing the moiré, it is possible to eliminate a screen disturbance and realize a stable image display.

(Embodiment 5) Next, a fifth embodiment of the present invention will be described with reference to the drawings.

FIG. 31 is a block diagram of a projection type image display device according to the fifth embodiment. In FIG. 31, first to fourth
The same reference numerals are given to the same portions as those of the embodiment, and the detailed description is omitted. In FIG. 31, reference numeral 33 denotes a CRT capable of improving the spot characteristics of the electron beam, 32 denotes a spot characteristic control unit for controlling the spot characteristics of the CRT, and 34 denotes the spot characteristic control unit 35, the deflection circuit 4, and the video circuit 7. It is a configured CRT drive unit.

First, in order to explain the control operation of the spot characteristics, a light emission characteristic diagram of FIG. 32 and a spot characteristic diagram of FIG. 33 will be used. In FIG. 33, the horizontal axis represents the input signal level, and the vertical axis represents the gamma characteristic of the spatial light modulator 101 for luminance. The lower half of the figure shows the case where a halftone spot from a black level and a halftone spot from a white level are input. The output brightness is shown on the left.
As shown in FIG. 32, since the gamma characteristic is a saturation characteristic in a high luminance region, a spot becomes narrower, that is, a so-called sharpness deterioration at the time of character display occurs. Also, the output luminance when the gamma characteristic is linear is significantly deteriorated as shown by the broken line. Therefore, in the spot characteristic control unit 32,
The spot characteristic of the Gaussian distribution shown by the solid line in FIG. 33 is controlled by scanning speed modulation, astigmatism correction, and the like to make the spot characteristic shown by the broken line in FIG. 33 to greatly improve the sharpness.

Next, in order to describe the spot characteristic control operation in detail, a detailed block diagram of the spot characteristic control section 35 shown in FIG. 34 and an operation waveform diagram shown in FIG. 35 will be used.

The video signal shown in FIG. 35A is supplied to a CRT 33 having a Gaussian distribution spot characteristic.
As shown in FIG. 35 (b), the response on the RT screen is
The response of the high-frequency component decreases, and the sharpness deteriorates as shown by the broken line in FIG. Further, the video signal shown in FIG.
The differential signal of (c) is created, and this signal is
By driving the auxiliary deflection yoke 37 to perform the scanning linear velocity, the spot characteristic is improved and the response on the CRT tube surface of FIG. 35D is obtained. As a result, FIG.
(E) The conventional response indicated by the broken line is improved to the response indicated by the solid line in FIG. As shown in the waveform response characteristics before and after the correction in FIG. 36, the sharpness particularly at the time of displaying characters is greatly improved.

As described above, according to the present embodiment, the spatial light modulator is controlled to reduce sharpness due to the gamma saturation characteristic generated at the time of optical writing on the CRT and to control fine spot characters by controlling the spot characteristic of the CRT. By improving the sharpness at the time of display, it is possible to achieve both high luminance and high resolution.

Embodiment 6 Next, a sixth embodiment of the present invention will be described with reference to the drawings.

FIG. 37 is a block diagram of a projection type image display device according to the sixth embodiment. In FIG. 31, first to fifth
The same reference numerals are given to the same portions as those of the embodiment, and the detailed description is omitted. In FIG. 37, 38 is a gamma correction unit for correcting gamma characteristics on the screen, 39 is a conversion coefficient calculation unit for calculating a conversion coefficient for gamma correction for each vertical scanning frequency from an input synchronization signal, and 40 is a conversion coefficient calculation unit. This is a CRT drive unit including the gamma correction unit 38, the conversion coefficient calculation unit 39, and the deflection circuit 4.

First, the gamma correction operation when the vertical scanning frequency changes will be described with reference to the emission characteristic diagram of FIG. FIG. 38 shows that the vertical scanning frequency is 40 to 150.
This is a light emission characteristic when the frequency is changed in Hz, and the gamma characteristic changes according to the vertical scanning frequency as described in the third embodiment. Therefore, the conversion coefficient calculation unit 39 detects the vertical scanning frequency, calculates a conversion coefficient for obtaining a reference gamma characteristic of 60 Hz, for example, and supplies the calculated conversion coefficient to the gamma correction unit 38 to perform vertical scanning. The gamma characteristic is controlled so that a gamma curve of 60 Hz is always obtained even when the frequency changes, thereby realizing good gradation and color reproducibility.

Next, a detailed block diagram of the transform coefficient calculating section 39 in FIG. 39 and a characteristic diagram in FIG.

The video signal is supplied to a gamma correction circuit 38, which performs gamma correction of several-point broken line approximation in which the gamma characteristic near low luminance and near middle luminance can be changed, and this correction signal is applied to a CRT. On the other hand, the vertical synchronizing signal is supplied to a vertical scanning frequency detecting circuit 43 to detect a vertical scanning frequency.
Is supplied to the intermediate luminance conversion coefficient calculation circuit 42 to calculate the conversion coefficient. FIG. 40 shows the characteristics of the conversion coefficient, where the horizontal axis represents the vertical scanning frequency and the vertical axis represents the conversion coefficient. According to the vertical scanning frequency detection result, for example, linear approximation is performed at low luminance in FIG. 40A, and curve approximation is performed at medium luminance in FIG. By performing the conversion, a constant gamma characteristic can be always realized even when the vertical scanning frequency changes.

This can be realized with a simple circuit configuration because the uniformity correction data can be shared as described in the first embodiment.

Note that the frequency of the drive waveform to the spatial light modulator is a frequency synchronized with the input vertical synchronization signal.

As described above, according to this embodiment, the conversion coefficient of the gamma characteristic is calculated by detecting the vertical scanning frequency.
By performing gamma correction according to the conversion coefficient, good gradation and color reproduction performance can be realized.

In this embodiment, a projection type image display device using a light-writing type liquid crystal light valve or the like has been described for easy understanding. However, other projection type display devices are also effective. Needless to say.

[0095]

According to the projection type image display device of the present invention,
By controlling the light emission characteristics according to the image information of the image light written in the spatial light modulator, optimal display performance (brightness, gradation, sharpness) can be realized corresponding to various signal sources.

Further, according to the projection type image display device of another invention, the drive voltage is generated by changing the frequency of the drive waveform applied to the spatial light modulator in accordance with the vertical scanning frequency of the image light. By always setting the light emission characteristics with the black level as the origin, good gradation and color reproducibility can be realized.

Further, according to the projection type image display device of another invention, image light to be written to the spatial light modulator is generated by a conversion signal obtained by scan-converting the vertical scanning frequency of the input signal to a specific scanning frequency. By applying a drive voltage synchronized with the vertical scanning frequency of the image light to the spatial light modulator,
Image display with good uniformity can be realized for various signal sources.

Further, according to the projection type image display apparatus of another invention, the moire generated by the interference between the scanning line and the pixel at the time of light writing on the CRT by the spatial light modulator having the pixel structure is reduced by the scanning line interval. By controlling and removing moiré, it is possible to eliminate screen disturbance and realize stable image display.

Further, according to the projection type image display apparatus of another invention, the spatial light modulator is controlled to reduce sharpness by the gamma saturation characteristic generated at the time of optical writing of the CRT and to control the spot characteristic of the CRT. By improving the sharpness at the time of displaying fine characters, it is possible to achieve both high luminance and high resolution.

Further, according to the projection type image display apparatus of another aspect of the present invention, the conversion factor of the gamma characteristic is calculated by detecting the vertical scanning frequency, and the gamma correction is performed in accordance with the conversion factor, so that a good image quality can be obtained. Tonality and color reproduction performance can be realized, and support for multi-scan can be easily realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a projection type image display device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram for explaining a light emission characteristic control operation according to the first embodiment;

FIG. 3 is a gamma characteristic diagram for explaining the operation of the first embodiment.

FIG. 4 is a diagram showing a time aperture ratio for explaining the operation of the first embodiment;

FIG. 5 is a spatial distribution characteristic diagram of a gamma characteristic for explaining the operation of the first embodiment.

FIG. 6 is a spatial distribution characteristic diagram of a gamma characteristic according to a difference in a time aperture ratio for explaining an operation of the first embodiment.

FIG. 7 is a spatial distribution characteristic diagram of a gamma characteristic by a writing system for explaining an operation of the first embodiment;

FIG. 8 is a spatial distribution characteristic diagram of a gamma characteristic by a projection system for explaining the operation of the first embodiment.

FIG. 9 is a block diagram for explaining a gamma correction operation according to the first embodiment;

FIG. 10 is a gamma characteristic diagram for explaining the operation of the first embodiment.

FIG. 11 is a gamma characteristic diagram for explaining the operation of the first embodiment.

FIG. 12 is a block diagram for explaining a drive waveform generation operation according to the first embodiment;

FIG. 13 is an operation waveform diagram for explaining the operation of the first embodiment.

FIG. 14 is a gamma characteristic diagram for explaining the operation of the first embodiment.

FIG. 15 is a block diagram of a projection type image display device according to a second embodiment of the present invention.

FIG. 16 is a gamma characteristic diagram for explaining the operation of the second embodiment.

FIG. 17 is a block diagram for explaining a drive waveform generation operation according to the second embodiment;

FIG. 18 is an operation waveform diagram for explaining the operation of the second embodiment.

FIG. 19 is a gamma characteristic diagram for explaining the operation of the second embodiment.

FIG. 20 is a block diagram of a projection type image display device according to a third embodiment of the present invention.

FIG. 21 is a block diagram for explaining a scan conversion operation according to the third embodiment;

FIG. 22 is a gamma characteristic diagram for explaining the operation of the third embodiment.

FIG. 23 is a diagram illustrating C for explaining the operation of the third embodiment;
RT afterglow characteristic diagram

FIG. 24 is a spatial distribution characteristic diagram of a gamma characteristic for explaining the operation of the third embodiment.

FIG. 25 is a block diagram of a projection type image display device according to a fourth embodiment of the present invention.

FIG. 26 is a diagram showing a pixel structure and scan lines for explaining the operation of the fourth embodiment;

FIG. 27 is a diagram showing scanning lines for explaining the operation of the fourth embodiment;

FIG. 28 is a block diagram for explaining a moire removal signal generation operation according to the fourth embodiment;

FIG. 29 is an operation waveform diagram for explaining the operation of the fourth embodiment and a diagram showing scanning lines;

FIG. 30 is an operation diagram for explaining the operation of the fourth embodiment;

FIG. 31 is a block diagram of a projection type image display device according to a fifth embodiment of the present invention.

FIG. 32 is a gamma characteristic diagram for explaining the operation of the fifth embodiment, and a principle diagram of sharpness reduction.

FIG. 33 is a spot characteristic diagram for explaining the operation of the fifth embodiment.

FIG. 34 is a block diagram for explaining a spot characteristic control operation according to the fifth embodiment;

FIG. 35 is an operation waveform diagram for describing a spot characteristic control operation according to the fifth embodiment.

FIG. 36 is a gamma characteristic diagram for explaining the operation of the fifth embodiment and a principle diagram of a sharpness improvement effect;

FIG. 37 is a block diagram of a projection-type image display device according to a sixth embodiment of the present invention.

FIG. 38 is a gamma characteristic diagram for explaining the operation of the sixth embodiment.

FIG. 39 is a block diagram for explaining a conversion coefficient calculation operation according to the sixth embodiment;

FIG. 40 is a characteristic diagram for explaining a conversion coefficient calculation operation according to the sixth embodiment;

FIG. 41 is a sectional view of a conventional spatial light modulator.

FIG. 42 is a configuration diagram of a projection-type image display device configured using a conventional spatial light modulation element.

FIG. 43 is a drive voltage waveform diagram of a conventional spatial light modulator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Emission characteristic control part 2, 9, 19 Drive waveform generation part 8 CRT drive part 12 Scan conversion part 13 CRT (short afterglow) 21 Deflection circuit 22 Moire removal signal generation part 23, 101 Spatial light modulation element 32 Spot characteristic control part 38 gamma correction unit 39 conversion coefficient calculation unit 100 projection image display device 108 CRT 110 writing lens 111 light source 114 visualization unit 115 projection lens

Claims (15)

[Claims] 1. A spatial light modulator, at least an image light generator for generating image light to be written on the spatial light modulator, and a drive waveform applied to the spatial light modulator in accordance with image information of the image light And a light emission characteristic control unit that controls light emission characteristics by controlling image light, and performs image display suitable for an input video source. 2. The light emission characteristic means according to gamma characteristics determined by image light and a spatial light modulation element, a wide range for a moving image,
2. The projection type image display device according to claim 1, wherein the setting is such that a still image such as a character has a narrow range. 3. The light emission characteristic control means sets the spatial light modulator to a black level and sets a high temporal aperture ratio for a moving image, and sets the image light to a black level for a still image such as a character or figure. 2. The projection type image display device according to claim 1, wherein the projection image display device is set to have a low time aperture ratio. 4. At least a spatial light modulator, image light generating means for generating image light to be written on the spatial light modulator, and a driving waveform applied to the spatial light modulator, a vertical scanning frequency of the image light. And a driving waveform generating means for generating a driving voltage in accordance with the above, and realizing the light emission characteristic with the black level as the origin even when the vertical scanning frequency changes. 5. A driving waveform generator generates a driving voltage having an erasing period and a writing period in synchronization with a half frequency only when a vertical scanning frequency of image light is equal to or higher than a specific frequency. 5. The projection type image display device according to claim 4, wherein even when the scanning frequency changes, the light emission characteristics are set to have the black level as the origin. 6. At least a spatial light modulator, conversion means for scan-converting a vertical scanning frequency of an input signal to a specific scanning frequency, and image light for writing the converted signal to the spatial light modulator to generate image light. A projection-type image display device comprising: a generating unit; and a driving waveform generating unit that generates a driving voltage that synchronizes a driving waveform applied to the spatial light modulator with a vertical scanning frequency of the image light. 7. The projection type image display device according to claim 6, wherein the conversion means converts the input signal into a scanning frequency that is n times the vertical scanning frequency of the input signal. 8. The projection type image display apparatus according to claim 10, wherein the image light generating means generates an image using a CRT having a short afterglow time as the optical writing means. 9. A spatial light modulator having at least a pixel structure, and an image light to be written on the spatial light modulator,
A projection-type image display device comprising: an image light generating unit that generates light using T; and a removing unit that removes moiré between a pixel of the spatial light modulator and a scanning line interval of a CRT. 10. The projection-type image display device according to claim 9, wherein said removing means removes moire by wobbling the scanning line interval only for a signal source having a wide scanning line interval. 11. Controlling at least a spatial light modulator, image light generating means for generating image light to be written to the spatial light modulator using a CRT, and a spot characteristic determined by a CRT Gaussian distribution of the image light. A projection-type image display device comprising a spot characteristic control means for improving the sharpness. 12. The projection type image display device according to claim 11, wherein the spot characteristic control stage modulates the scanning speed of the electron beam of the CRT. 13. At least a spatial light modulator, image light generating means for generating image light to be written on the spatial light modulator, and a conversion coefficient for gamma correction according to a vertical scanning frequency of the image light. And a light emission characteristic control means for controlling light emission characteristics of image light with the conversion coefficient. 14. The projection-type image display device according to claim 13, wherein said conversion coefficient calculating means calculates a low-luminance linear approximation and a medium luminance curve-like conversion coefficient. 15. The projection type image display according to claim 13, wherein the light emission characteristic control means controls the light emission characteristic by controlling a basic gamma characteristic based on an approximation coefficient of low luminance and medium luminance. apparatus.