JP2010164645A - Image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projection device using a white light source, which suppresses lowering of color reproducibility of a projection image caused by deviation of emission spectrum with simple constitution. <P>SOLUTION: The image projection device includes: a white LED 101; an LED controller 2 controlling the white LED 101; a color wheel 103 having a red filter, a green filter and a blue filter that respectively transmit light of a red wavelength band, a green wavelength band and a blue wavelength band, out of white light emitted from the white LED 101; a motor controller 3 rotating the color wheel 103; an LCD 106 modulating the light of the respective wavelength bands transmitted through the color wheel 103; and an LCD controller 1 controlling the LCD 106 based on an image signal. Since the white LED 101 is controlled so that emission intensity may be higher when the white light is incident on the red filter and the green filter than when the white light is incident on the blue filter, the color reproducibility of the projection image is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image projection apparatus (hereinafter referred to as “projector”) that enlarges and projects an image on a projection surface, and is particularly suitable for a single-plate projector using a color wheel.

  Conventionally, in a single-plate projector using a color wheel, a lamp or an InGaN-based white LED is used as a light source. The light emitted from the light source passes through red, green, and blue filters disposed on the color wheel, is modulated by a light modulator such as an LCD (Liquid Crystal Display), and is projected onto the projection surface. In this way, red, green, and blue images are projected on the projection surface in a time-sharing manner, and each color image is synthesized with a color image by the eyes of the viewer.

Patent Document 1 below describes a light source control method in a three-plate projector. Here, a light source is arranged for each color, and the emission intensity of the light source of each color is adjusted according to the video signal so that the brightness of the projected image is appropriate.
JP2007-272114A

  In the single-plate projector, when a white LED is used as a light source, there arises a problem that the color reproducibility of a projected image is deteriorated due to the spectral characteristics of the white LED. That is, in the white LED, the emission intensity of the light in the blue wavelength band is considerably higher than the emission intensity of the light in the red wavelength band and the green wavelength band. Therefore, when the white LED is used as a light source, the projected image is totally displayed. There is a problem of becoming pale.

  Since the technique of the above-mentioned Patent Document 1 is to adjust the intensity of the light source arranged for each color, a single-plate projector that separates white light from a white LED into each color light by a color wheel in a time-sharing manner is used. It cannot be used.

  The present invention has been made in view of such problems, and an image that can improve the color reproducibility of a projected image with a simple configuration even when the emission spectrum of a white light source is biased toward the blue wavelength band. An object is to provide a projection apparatus.

  An image projection apparatus according to the present invention includes a light source that emits white light, a light source control unit that controls the light source, and light in a red wavelength band, a green wavelength band, and a blue wavelength band among white light emitted from the light source. A color wheel having a red filter, a green filter, and a blue filter that respectively transmit light, a rotation control unit that rotates the color wheel, an optical modulator that modulates light in each wavelength band transmitted through the color wheel, and a video signal And a modulation control unit for controlling the optical modulator based on the above. Here, the modulation control unit drives the light modulator in synchronization with the rotation of the color wheel so that the corresponding light modulation is performed on the light of each wavelength band. The light source control unit controls the light source so that an emission intensity is higher when the white light is incident on the red filter and the green filter than when the white light is incident on the blue filter.

  According to the image projection device of the present invention, the image projected by the light in the red wavelength band and the green wavelength band is emphasized, so that even when the emission spectrum of the light source is biased to the blue wavelength band, the projected image is displayed. The bluish-white appearance is suppressed, and the color reproducibility of the projected image is improved.

  Further, in the image projection apparatus according to the present invention, the light source control unit is configured so that the intensity ratio of the light in each wavelength band transmitted through the color wheel approaches the intensity ratio of the light in each wavelength band in sunlight. It can be configured to control the emission intensity of the light source. This further brings the projected image closer to natural colors.

  The image projection apparatus according to the present invention further includes a temperature sensor for detecting a temperature of the light source, and the light source control unit is configured to output the white light to the red filter based on the temperature detected by the temperature sensor. The emission intensity of the light source when entering the green filter and the blue filter may be controlled. In this way, the color reproducibility of the projected image can be properly maintained even when the emission spectrum of the light source changes due to temperature change.

  In this case, the image projection apparatus includes a memory that stores a table in which the temperature is associated with information on the emission intensity of the light source when the white light is incident on the red filter, the green filter, and the blue filter. The light source control unit may be configured to control the emission intensity of the light source based on information in the table corresponding to the temperature detected by the temperature sensor.

  As described above, according to the image projection apparatus of the present invention, even when the emission spectrum of the white light source is biased toward the blue wavelength band, the color reproducibility of the projected image can be improved with a simple configuration.

The effects and significance of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely an example when the present invention is put into practice, and the present invention is not limited to what is described in the following embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

<Example>
FIG. 1 is a diagram illustrating a configuration of a projector according to an embodiment. FIG. 6A is a diagram showing a configuration of a main circuit related to driving of the projector, FIG. 6B is an internal perspective view of the white LED 101, and FIG. FIG.

  Referring to FIG. 2A, the projector includes a white LED 101, a condenser lens 102, a color wheel 103, a motor 104, a rod integrator 105, an LCD 106, a projection lens 107, a magnetic sensor 108, An LCD control circuit 1, an LED control circuit 2, and a motor control circuit 3 are provided.

  The white LED 101 is a commercially available InGaN (indium gallium nitride) white LED. The white LED 101 emits pseudo white light by the drive current supplied from the LED control circuit 2.

  Referring to FIG. 2B, the white LED 101 includes an electrode terminal 101a, a blue LED 101b, a base 101c, and a yellow phosphor layer 101d.

  The electrode terminal 101a supplies the drive current supplied from the LED control circuit 2 to the blue LED 101b. The blue LED 101b is fixed on the base 101c and emits blue light by the supplied drive current. The blue LED 101b is made of InGaN (indium gallium nitride). The yellow phosphor layer 101d is formed of a yellow phosphor and a resin, and is disposed on the emission direction side of the blue LED 101b.

  In the configuration of FIG. 5B, when the blue LED 101b emits light according to the drive current supplied from the LED control circuit 2, the yellow phosphor forming the yellow phosphor layer 101d is excited and pseudo white light is emitted from the white LED 101. Emitted.

  Returning to FIG. 2A, the pseudo white light emitted from the white LED 101 is condensed by the condenser lens 102 and is incident on the color wheel 103.

  Referring to FIG. 3C, the color wheel 103 is a disk having a rotation hole 103a at the center and red, blue, and green filters centered on the rotation hole 103a on a plane perpendicular to the optical axis. . The red, blue, and green filters are evenly arranged in the circumferential direction of the color wheel 103, and each of the incident light, the light in the red wavelength band, the light in the blue wavelength band, and the light in the green wavelength band (hereinafter referred to as “light”). , “R light, G light, B light”), and light in other wavelength bands is cut. On the peripheral surface of the color wheel 103, a magnet 103b is embedded at the boundary position between the red filter and the green filter.

  Returning to FIG. 2A, the motor 104 has a rotation support shaft 104 a, and a rotation hole 103 a is fitted into the rotation support shaft 104 a, and the color wheel 103 is mounted on the rotation support shaft 104. The motor 104 rotates the rotation support shaft 104 a by the drive current supplied from the motor control circuit 3. Accordingly, the color wheel 103 is rotated around the rotation hole 103a, and the pseudo white light incident on the color wheel 103 is sequentially passed through the red, green, and blue filters. As a result, the light emitted from the color wheel 103 changes in the order of R light, G light, and B light according to the rotational speed of the motor 104.

  A magnetic sensor 108 is disposed in the vicinity of the peripheral surface of the color wheel 103, and a pulse signal is output from the magnetic sensor 108 at a timing when the magnet 103b faces the magnetic sensor 108. This pulse signal is output to the LCD control circuit 1, the LED control circuit 2 and the motor control circuit 3.

  R light, G light, and B light sequentially emitted from the color wheel 103 enter the rod integrator 105. The rod integrator 105 makes the intensity distribution of the incident R light, G light, and B light uniform. The R light, G light, and B light emitted from the rod integrator 105 enter the LCD 106.

  The LCD 106 modulates R light, G light, and B light, respectively, in accordance with the drive signal from the LCD control circuit 1. The projection lens 107 is a lens that projects R light, G light, and B light emitted from the LCD 106 onto a projection surface.

  The LCD control circuit 1 supplies a drive current to the LCD 106 according to the input video signal. The LCD control circuit 1 switches driving of the LCD 106 based on the pulse signal input from the magnetic sensor 108. That is, at the timing when the pseudo white light emitted from the white LED 101 is incident on the red filter on the color wheel 103, the LCD 106 is driven so that the modulation pattern according to the red image is obtained, and the pseudo white light is At the timing when the light enters the blue filter, the LCD 106 is driven so that the modulation patterns corresponding to the green image and the blue image are obtained.

  The LED control circuit 2 and the motor control circuit 3 control the white LED 101 and the motor 104, respectively, based on the pulse signal input from the magnetic sensor 108. That is, the LED control circuit 2 sets based on the pulse signal whether the pseudo white light is incident on the red, green, or blue filter. Then, as described later, the emission intensity of the white LED 101 is changed according to which filter the pseudo white light is incident on. The motor control circuit 3 controls the motor 104 so that the pulse signal input from the magnetic sensor 108 has a predetermined cycle.

  With the above control, the light emission intensity of the white LED 101 changes in synchronization with switching of the filter on which the pseudo white light is incident. Further, in synchronization with the change of the light incident on the LCD 106 between the R light, the G light, and the B light, the modulation pattern by the LCD 106 changes to a modulation pattern corresponding to each color light. Thereby, images of R light, G light, and B light (hereinafter referred to as “R image”, “G image”, and “B image”) are projected on the projection surface at predetermined time intervals, and a color image is projected by the viewer. Is synthesized.

  FIG. 2 is a diagram illustrating a method for adjusting the light emission intensity of the white LED 101 in the LED control circuit 2. FIGS. 4A and 4B are diagrams showing the white LED 101 and the emission spectrum of sunlight, respectively.

  The horizontal axes of FIGS. 4A and 4B represent wavelengths, and the central wavelengths of the R light, G light, and B light extracted by the filter of the color wheel 103 are shown on the horizontal axis. Moreover, the vertical axis | shaft of the same figure (a) and (b) represents the intensity | strength of the light in each wavelength.

  The emission spectrum of the white LED 101 is several steps lower than the B light in the intensity of the G light and the R light compared to the emission spectrum of sunlight that is natural white light. For this reason, if the emission intensity of the white LED 101 is constant over the image projection period, the projected color image looks entirely pale by the viewer.

  In order to eliminate this, the LED control circuit 2 controls the emission intensity of the white LED 101 as shown in FIG. The horizontal axis of the figure (c) represents elapsed time, and a vertical axis | shaft is the emitted light intensity of white LED101. As shown in the figure, the LED control circuit 2 emits the white LED 101 in one frame section of the projected image (the section in which R image, G image, and B image are projected one by one in order to construct one color image). Change the intensity stepwise. That is, here, the emission intensity (P2) of the white LED 101 in the projection interval of the R image and the G image is higher than the emission intensity (P1) of the projection interval of the B image.

  By adjusting the emission intensity of the white LED 101 in this way, the R image and the G image are enhanced, and the color image is suppressed from appearing pale. As a result, the color reproducibility of the color image is improved.

  The emission intensities P1 and P2 may be set so that the color image has a desired image quality. Here, the emission intensity of the white LED 101 in the projection interval of the R image and the G image is the same, but the emission intensity of the white LED 101 is changed stepwise in the projection interval of the R image and the projection interval of the G image. You may let them. For example, the emission intensity of the white LED 101 in the R image projection section may be increased stepwise compared to the G image projection section.

  If the ratio of the intensity of R light, G light, and B light emitted from the color wheel 103 is substantially equal to the ratio of the intensity of R light, G light, and B light in sunlight, the projected image is a natural color. It looks like an image and can improve the color reproducibility of a color image. In this case, the emission intensity of the white LED 101 in the projection interval of the R image, the G image, and the B image can be adjusted as follows, for example.

  The light intensity (light intensity at the central wavelength) of sunlight R light, G light, and B light is R0, G0, and B0, and the light intensity of the white LED 101 R light, G light, and B light (light intensity at the central wavelength). ) Is set to R1, G1, and B1, the light intensity of the R light, G light, and B light by the white LED 101 is set by setting the magnifications α, β, and γ such that R0: G0: B0 = αR1: βG1: γB1. Can be made substantially the same as the ratio of R0, G0, and B0 in sunlight. Therefore, by setting the ratio of the emission intensity of the white LED 101 in the projection interval of the R image, G image, and B image to α: β: γ, the intensity of the R light, G light, and B light transmitted through the color wheel 103 can be increased. The ratio can be close to the intensity ratio in the case of sunlight.

  FIG. 4D is a diagram showing the emission intensity of the white LED 101 controlled by the LED control circuit 2. The horizontal axis of the figure (c) represents elapsed time, and the vertical axis represents the emission intensity of the white LED 101 as a ratio. As shown in the figure, the output of the white LED 101 is changed stepwise in one frame section of the projected image. That is, the output of the white LED 101 is adjusted so that the ratio of the emission intensity in the projection interval of the R image, G image, and B image is α: β: γ. Thus, in each frame section, the ratio of the intensity of the R light, G light, and B light irradiated on the LCD 106 approaches the intensity ratio in the case of sunlight as described above, and the color reproducibility of the color image is improved. Can be improved.

  As described above, according to the present embodiment, since the output intensity of the white LED 101 in the R image and G image projection section is higher than that in the B image projection section, the color image is suppressed from appearing pale, and the color image is reproduced. Sexuality is enhanced. Further, by controlling the emission intensity of the white LED 101 as shown in FIG. 4D, the ratio of the intensity of R light, G light, and B light irradiated on the LCD 106 can be brought close to the intensity ratio in sunlight. The projected image can be brought close to a natural color image.

<Modification 1>
In the above embodiment, the R light, G light, and B light emitted from the rod integrator 105 are modulated by the LCD 106 and projected onto the projection surface. In this modification, a DMD (Digital Mirror Device) and a DMD control circuit are used instead of the LCD 106 and the LCD control circuit 1.

  FIG. 3 is a diagram showing the configuration of the projector according to this modification. FIG. 4A is a view of the projector as viewed from above, and FIG. 4B is a view of the projector as viewed from the side.

  Referring to FIGS. 2A and 2B, the projector includes DMD 201 and DMD control circuit 4 instead of LCD 106 and LCD control circuit 1 of the above embodiment. The light source unit 100 includes a white LED 101, a condenser lens 102, a color wheel 103, a motor 104, a rod integrator 105, and a magnetic sensor 108.

  Referring to FIG. 5A, R light, G light, and B light emitted from rod integrator 105 are incident on DMD 201 in a time division manner. The DMD 201 has a micromirror surface driven by a drive signal from the DMD control circuit 4, and only necessary light out of incident R light, G light, and B light is reflected toward the projection lens 107.

  The magnetic sensor 108 supplies a pulse signal to the LED control circuit 2, the motor control circuit 3 and the DMD control circuit 4 as in the above embodiment. By this pulse signal, synchronous control of the DMD 201, the white LED 101, and the color wheel 103 is performed as described above. The DMD control circuit 4 drives the DMD 201 with a modulation pattern for generating the R image, the G image, and the B image, respectively, in the projection interval of the R image, the G image, and the B image.

  Even in such a configuration, the output intensity of the white LED 101 is changed stepwise at the timing when the R light, G light, and B light are switched by the color wheel 103 as in the above-described embodiment. The color reproducibility of the color image to be generated can be improved.

<Modification 2>
In this modified example, a configuration for dealing with the power fluctuation of the white LED 101 is further added to the above embodiment.

  The white LED 101 has a characteristic that even if the magnitude of the drive signal is the same, the emission spectrum changes when the temperature of the light emitting unit changes. Therefore, in order to properly maintain the color reproducibility of the color image, it is necessary to change the light emission intensity of the white LED 101 in the projection interval of the R image, the G image, and the B image according to the temperature change of the white LED 101. .

  Below, even if the temperature of the white LED 101 changes, the ratio of the intensity of R light, G light, and B light after passing through the color wheel 103 is the ratio of the intensity of R light, G light, and B light in sunlight. The case where the emission intensity of the white LED 101 is changed will be described as an example.

  FIG. 4 is a diagram showing the configuration of the projector according to this modification. A temperature sensor 109 and a table 5 are added to the above embodiment.

  The temperature sensor 109 is disposed in the vicinity of the white LED 101, monitors the temperature of the white LED 101, and outputs the monitor temperature to the LED control circuit 2. The table 5 is a table in which the monitor temperature detected by the temperature sensor 109 and the emission intensity of the white LED 101 in the projection interval of the R image, the G image, and the B image are recorded, and is referenced by the LED control circuit 2. The table 5 is stored in a memory (not shown).

  In Table 5, the temperature is set so as to cover the range from the assumed minimum temperature to the maximum temperature, and each temperature has a certain width (for example, 20 ° C. to 30 ° C.). Yes. The emission intensity of the white LED 101 in the projection interval of the R image, G image, and B image associated with each temperature is the intensity of the R light, G light, and B light after passing through the color wheel 103 before and after the temperature change. The ratio of the intensity of the R light, G light, and B light is set to be approximately the same as the ratio of the intensity of R light, G light, and B light in sunlight.

  The LED control circuit 2 sequentially obtains the emission intensity of the white LED 101 in the projection interval of the R image, the G image, and the B image corresponding to the monitor temperature input from the temperature sensor 109 at the time of color image transcribing operation. The white LED 101 is caused to emit light with the obtained emission intensity.

  This maintains the image quality of the projected R, G, and B images even when the emission spectrum of the white LED 101 changes due to a temperature change, and as a result maintains the color reproducibility of the color image appropriately. be able to.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. Further, the embodiment of the present invention can be variously modified in addition to the above.

  For example, in the above embodiment, LCOS (Liquid Crystal On Silicon) may be used instead of the LCD 106.

  In the above-described embodiment and modification, the white LED 101, the color wheel 103, and the LCD 106 are synchronously controlled based on the pulse signal output from the magnetic sensor 108. However, according to other configurations, these synchronous controls are performed. May be performed.

  Further, in the above-described embodiments and modifications, the color wheel 103 is provided with three filters of red, green, and blue. Further, four or more filters are added such as a filter that transmits light in the yellow wavelength band. These filters may be arranged on the color wheel 103. In this case, for example, the emission intensity of the white LED 101 in the yellow image projection section may be set so that the color image has a desired image quality.

  Furthermore, in the above modification 2, the emission intensity of the white LED 101 is changed according to the temperature change by using the table 5, but the calculation process is performed by an arithmetic expression that defines the relationship between the temperature and the emission intensity, etc. According to another configuration, the emission intensity of the white LED 101 may be changed when the temperature changes.

  In addition, in the said Example and modification, it was made to improve the color reproducibility of a color image by changing the emitted intensity of white LED101, However, as an alternative method, without changing the emitted intensity of white LED101, A method of increasing the intensities of R light and G light by changing the transmittance of the red, green, and blue filters of the color wheel 103 can also be used. However, in this case, it is necessary to replace the red, green, and blue filters in accordance with changes in the characteristics of the white LED 101, and there is a demerit that if the emission spectrum of the white LED 101 changes due to a temperature change, this cannot be handled. is there. Therefore, when adjusting the transmittance of each color filter of the color wheel 103 as described above, the emission intensity of the white LED 101 is also adjusted in the R image, G image, and B image projection sections as described above. It is desirable to make it change.

  In addition, the embodiment of the present invention can be variously modified as appropriate within the scope of the technical idea shown in the claims.

The figure which shows the structure of the projector which concerns on an Example The figure which shows the adjustment method of the emitted light intensity of the white LED which concerns on an Example The figure which shows the structure of the projector which concerns on the example 1 of a change. The figure which shows the structure of the projector which concerns on the example 2 of a change.

1 ... LCD control circuit (modulation control unit)
2 ... LED control circuit (light source controller)
3 ... Motor control circuit (rotation controller)
4 ... DMD control circuit (modulation control unit)
5 ... Table 101 ... White LED (light source)
103 ... Color wheel 106 ... LCD (light modulator)
109 ... temperature sensor 201 ... DMD (optical modulator)

Claims (4)

A light source that emits white light;
A light source control unit for controlling the light source;
A color wheel having a red filter, a green filter, and a blue filter that respectively transmit light in a red wavelength band, a green wavelength band, and a blue wavelength band among white light emitted from the light source;
A rotation control unit for rotating the color wheel;
An optical modulator that modulates light of each wavelength band transmitted through the color wheel;
A modulation control unit for controlling the optical modulator based on a video signal,
The modulation control unit drives the light modulator in synchronization with rotation of the color wheel so that corresponding light modulation is performed on the light of each wavelength band,
The light source control unit controls the light source so that an emission intensity when the white light is incident on the red filter and the green filter is higher than when the white light is incident on the blue filter.
An image projection apparatus characterized by that. The image projection apparatus according to claim 1,
The light source control unit controls the emission intensity of the light source so that the intensity ratio of the light of each wavelength band transmitted through the color wheel approaches the intensity ratio of the light of each wavelength band in sunlight.
An image projection apparatus characterized by that. In the image projection device according to claim 1 or 2,
A temperature sensor for detecting the temperature of the light source;
The light source control unit controls the emission intensity of the light source when the white light is incident on the red filter, the green filter and the blue filter based on the temperature detected by the temperature sensor.
An image projection apparatus characterized by that. In the image projection device according to claim 3,
A memory for storing a table associating temperature with information on the emission intensity of the light source when the white light is incident on the red filter, the green filter, and the blue filter;
The light source control unit controls the emission intensity of the light source based on information in the table corresponding to the temperature detected by the temperature sensor;
An image projection apparatus characterized by that.

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