JPH10148807A - Mount-on-head type display device and its backlight driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mount-on-head type backlight driving method which is highly visually recognizable, is capable of minimized fatigue and wide dimming, and is low in power consumption by inputting the imaginal stimulation which passes an image display element formed by a liquid crystal panel and backlight into the eyes of a user at a definite level. SOLUTION: The effective potential of an image signal 103 and the reference potential (A) 3 are compared by a comparison means (A) 4 to enhance the luminance of the backlight when the effective potential is higher. And the ambient illuminance is measured by an electric light dell 5 and the result and the reference potential (B) 7 are compared by a comparison means (B) 8 to enhance the luminance of the backlight 12 when the ambience is dark.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head mounted display device and a backlight driving method for visually recognizing an image formed by an image display device by enlarging a virtual image, and to a method of driving the backlight with high visibility and a wide range of backlight brightness. Drive for realizing light is realized.

[0002]

2. Description of the Related Art In recent years, head-mounted display devices have been proposed in order to meet the demand for enhancing portability of video and data displays. Since the display mainly uses a transmissive liquid crystal panel, it is necessary to irradiate the panel with a backlight from behind. Then, as a backlight driving method, (1) Japanese Patent Application Laid-Open No. H6-70268 and (2) Japanese Patent Application Laid-Open No. H6-335007 are listed.

FIGS. 1 and 2 describe a general head-mounted display device. FIG. 1 is a side view of a mounted state, and FIG. 2 is a cross-sectional view of a virtual image forming optical system. FIG. 3A is a diagram illustrating a closed type, and FIG. 3B is a diagram illustrating a see-through type.

In FIG. 1A, an apparatus main body (60) comprises:
A virtual image forming optical system (62) is provided in front of the user (61), and a forehead pad (64), a slider (65), and an arm (6) are provided via a hinge (63).
6), is attached to a mounting means (68) composed of an ear pad (67), and the mounting means (68) is mounted on the head of the user (61), whereby the apparatus body (60), The system (62) is held in front of the user (61).

In FIG. 2A, a virtual image forming optical system (6
2) is an image display element (71) composed of at least a liquid crystal panel (70) and a backlight (12) for irradiating the liquid crystal panel (70) from behind, a reflection mirror (72), and magnifying optical means. It is composed of a lens (73). The optical path of the image light emitted from the image display element (71) is changed by the reflection mirror (72), the image light is formed in the eye by the lens (73), and the user (61) expands ahead of the line of sight. A virtual image (74) can be visually recognized.

(B) is a see-through compatible mechanism that allows the user to view the outside scenery information while the apparatus main body (60) is hung, and a see-through optical system using a concave mirror (80) and a half mirror (81) that are magnifying optical means. It is. The optical path of the image light emitted from the image display element (71) is once changed by the half mirror (81), and is reflected by the concave mirror (80) in an enlarged manner.
An image is formed in the eye through (81).

In both cases, a visor (82) arranged in front of the virtual image forming optical system (62) is arranged to secure the contrast of the image light and improve the visibility.

[0008]

In the head mounted display (HMD) as described above, the space between and around the virtual image forming optical system (62) and the eyes is open. When used in a place where the peripheral illuminance is high, the contrast has been reduced due to an increase in the amount of sneaking light and the amount of light directly incident through see-through. In order to solve the above problem, the above-mentioned conventional example has a sensor for measuring the amount of light in the surroundings, and adjusts the brightness of the backlight and the brightness of the video signal based on the measurement result.

However, only the brightness of the backlight is controlled or the brightness of the video signal is adjusted according to the peripheral illuminance, and the characteristics of the video signal itself, that is, the state of the display screen are not considered at all. In other words, if the surrounding illuminance is bright, the backlight or the brightness is simply raised to increase the brightness. Therefore, when the display is the positive display, the stimulus entering the eyes becomes stronger, and the user feels fatigue.

Further, in the case of a see-through mechanism in which the outside scene information can be visually recognized while the HMD is mounted, the parameter of the adjustment element is incident on the peripheral illuminance, particularly the eye, although the appearance of the display varies depending on the use environment. It is determined only by the illuminance in the optical axis direction. In the structure most frequently used in the see-through mechanism, the light incident on the eye is reduced to 1/4 as compared with the contrast when the light is emitted from the panel.
Since the contrast in the case where the peripheral illuminance is high is further reduced, the HM having excellent visibility can be obtained only by the above-described adjustment method.
D cannot be realized.

The adjustment for ensuring the visibility according to the peripheral illuminance is performed only by controlling the backlight luminance or adjusting the brightness of the video signal, and the characteristics of the video signal itself, that is, the state of the display screen are not changed at all. Was not taken into account. In other words, if the surrounding illuminance is bright, the backlight or the brightness is simply raised to increase the brightness. Therefore, when the display is the positive display, the stimulus entering the eyes becomes stronger, and the user feels fatigue.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object the first object is to maintain a constant image stimulus input to the user's eyes to prevent fatigue and to enhance visibility. Second, it is an object of the present invention to provide a magnified virtual image screen, and to realize a backlight driving method of a head mounted display device capable of dimming a wide range with low power with a simple configuration.

[0013]

Means for Solving the Problems To solve the above problems, (Means 1) An image display device comprising a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an image display device comprising: In a backlight driving method for a head-mounted display device in which a magnifying optical unit for enlarging a formed image is housed in a device main body, a backlight driving circuit for driving the backlight displays an image on the image display element. The brightness of the backlight is changed according to the effective voltage (or the bright voltage) of the image signal to be output.

According to the above method, the brightness of the backlight can be changed according to the effective voltage or the bright voltage of the image signal to be displayed.

(Means 2) An image display device provided with a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an enlargement optical device for enlarging an image formed by the image display device. In the backlight driving method for a head-mounted display device housed in a main body, the backlight driving circuit for driving the backlight compares an output of illuminance detecting means for detecting ambient illuminance with a first reference voltage. The luminance of the backlight is determined based on a first comparison result and a second comparison result obtained by comparing an effective voltage (or a bright voltage) of an image signal to be displayed on the image display element with a second reference voltage. Is determined.

According to the above method, the backlight brightness determined by the brightness of the surrounding environment is compared with the backlight brightness determined by the effective voltage or the brightness voltage of the image signal, and the backlight taking both into consideration is considered. Can be set.

(Means 3) In addition to the means (1) or (2), the backlight drive circuit includes a voltage detecting means for detecting an effective voltage or a bright voltage of the image signal, a reference voltage and an output of the voltage detecting means. Comparison means for comparing the effective voltage (or the bright voltage) with the backlight when the effective voltage (or the bright voltage) is lower than the reference voltage than when the effective voltage (or the bright voltage) is higher than the reference voltage. It is characterized by increasing the brightness.

According to the above method, when the effective voltage level of the image signal is high, that is, when the content of the display screen is mainly white, if the brightness of the backlight is high, the irritation to the user's eyes is too strong. Are more likely to complain of eye fatigue. Also,
When the effective voltage level is low and the display screen is mainly black, the visibility is deteriorated unless the brightness of the backlight is bright, which also causes the user to be tired. Therefore, by changing the brightness of the backlight to the optimum level according to the state of the effective voltage level of the screen, the stimulus input to the eyes is kept constant, the burden on the eyes is minimized, and the display is rich in visibility Can be provided.

(Means 4) In the method according to the means 1 to 3, the detection period of the effective voltage (or the bright voltage) is further matched with one field period of the image signal.

According to the above method, for example, the brightness of the backlight can be adjusted even when a moving image is displayed.

(Means 5) The method of any of the means 1 to 3 is further characterized in that the detection period of the effective voltage (or the bright voltage) is made to coincide with one frame period of the image signal.

According to the above method, for example, when displaying a still image, the brightness of the backlight can be adjusted more easily than in the means 4.

(Means 6) In the method of any of the means 1 to 5, the reference voltage is a plurality of voltages.

According to the above method, the adjustment can be made fine.

(Means 7) In the method of the means 2, the first and second reference voltages are each a plurality of voltages.

According to the above method, the adjustment can be made fine.

(Means 8) An image display device provided with a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an enlargement optical device for enlarging an image formed by the image display device. In a backlight driving method for a head-mounted display device housed in a main body, a backlight driving circuit for driving the backlight increases luminance of the backlight when ambient illuminance is lower than when it is high. And

According to the above method, the brightness of the backlight can be reduced when the surrounding environment is bright, and the brightness of the backlight can be increased when the surrounding is bright, so that the amount of light that can be seen by the user is not excessively changed. can do.

(Means 9) An image display device provided with a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an enlargement optical device for enlarging an image formed by the image display device. In a backlight driving method for a head-mounted display device housed in a main body, a backlight driving circuit for driving the backlight includes a plurality of pixels having different periods based on a horizontal synchronization signal of image information to be displayed on the image display element. A backlight pulse is generated, and the luminance of the backlight is adjusted by driving the backlight based on the backlight pulse selected from the plurality of backlight pulses.

According to the above method, the brightness of the backlight can be easily adjusted by using the horizontal synchronization signal.

(Means 10) The backlight drive circuit includes pulse width modulation means for modulating a pulse width of the selected backlight pulse, and voltage modulation means for modulating a backlight power supply voltage applied to the backlight. And driving the backlight by selecting the pulse width modulation means and the output of the voltage modulation means so that the backlight is stably lit.

According to the above method, the pulse width of the backlight pulse and the applied voltage can be set in the linear region where the luminous efficiency of the backlight tube is always linear, that is, in the region where the luminous efficiency is stable, so that unnecessary power is not consumed. And fine-tuning of the brightness becomes possible. Further, even when the dimming of the backlight by the pulse width is at a limit, by adjusting the applied voltage, more stable and fine adjustment of luminance can be performed over a wide range.

(Means 11) In any one of the means 1 to 10, the backlight drive circuit operates in synchronization with a clock that defines timing for displaying data on the pixels of the liquid crystal panel. I do.

According to the above method, the backlight pulse synchronized with the horizontal synchronization signal of an intelligent device having a CPU such as a personal computer or a portable device has a short synchronization period (pulse width) of the horizontal synchronization signal. If the pulse width of the backlight pulse is set too long to increase the backlight pulse, the backlight pulse will be applied to the display area beyond the retrace period, and the effect of spike noise, which is likely to occur at the rising and falling portions of the backlight pulse, will occur. It will be easier.

Therefore, for example, the falling edge of the backlight pulse is synchronized with the falling edge of DXCLK which determines the horizontal display writing of the liquid crystal panel.
The backlight pulse can completely cover the front and back porch before and after the display area and can prevent the backlight pulse from being over in the display area, so that there is no influence of spike noise on the display screen and visibility is improved. A rich display can be provided. Further, fine adjustment of the luminance can be performed over a wider range.

(Means 12) In addition to the means 6, it is possible to reduce power consumption by providing means for restricting power supply to the comparison means and the like when the voltage detection means is not operating. .

(Means 13) An image display device provided with a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an enlargement optical device for enlarging an image formed by the image display device. In a head-mounted display device housed in a main body, a backlight driving circuit for driving the backlight is configured to control the luminance of the backlight according to an effective voltage (or a bright voltage) of an image signal to be displayed on the image display element. Is changed.

According to the above method, the luminance of the backlight can be changed according to the effective voltage or the bright voltage of the image signal to be displayed.

[0039]

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

(First Embodiment) FIGS. 3 to 6 show a backlight driving method of a head mounted display according to a first embodiment of the present invention, and FIG. 3 explains a backlight pulse generating means. FIG. 4 is a diagram for explaining a method of dimming the backlight luminance with an effective voltage of an image signal, FIG. 5 is a diagram for dimming the luminance by peripheral illuminance, and FIG. 6 is a block diagram of a backlight driving circuit. As in the above-described embodiment, the same portions are denoted by the same reference numerals, and description thereof is omitted.

FIG. 3 shows a backlight pulse generating means (1).
A block diagram showing how the BLP (102) is created in
This is a timing chart.

First, an image information source is an intelligent device having a CPU such as a personal computer or a portable terminal device and a TV.
And video devices that conform to the NTSC standard, such as
The frequency of the YNC (101) is different. In the following embodiment, a backlight pulse (BLP) (102) is created using a horizontal synchronization signal (HSYNC) (101) input from an intelligent device. The intelligent device displays a screen by non-interlace driving, but the NTSC video device performs interlacing driving, so the HSYNC (101) of the intelligent device is used.
Is the HSYNC (1) of the NTSC video device (14).
It becomes about twice the frequency of 12).

HSYNC input from the image information source (13)
(101) is input to the counter (21). The counter (21)
Outputs Q1, Q2, and Q3 synchronized with the 2 ×, 4 ×, and 8 × periods of the HSYNC (101), respectively, and the pulse almost coincides with the synchronization period of the HSYNC (101) by the multivibrator (MB) (22). A pulse (M1, M2, M3) of 1 / n cycle of HSYNC (101) set to a width or an arbitrary pulse width and synchronized with Q1 to Q3 is created. M mentioned above
The four signals including the three outputs of the B (22) and the original HSYNC (101) are arbitrarily selected by the switch SW (23), and the BLP (10
Output as 2). Also, NTSC video equipment (14)
In the case of the HSYNC (112) input from, the sync signal is separated from the composite video signal by the sync separation circuit (20) at the input stage, and then the same backlight pulse generation processing is performed.

FIG. 4 is a diagram for explaining a circuit for dimming the luminance in accordance with the effective voltage level (Vrms) of the image signal (103). Vrms is high (that is, the entire display screen is mainly white). Image display element (7
Since the absolute amount of light emitted from (1) is large and the light stimulus that enters the user's eyes becomes strong and causes fatigue, the backlight (1)
2) Reduce the brightness. However, if the luminance is lowered too much, the contrast is lowered and the visibility of the image is lowered. Therefore, it is desirable to set the contrast within a certain range. According to experiments by the inventors, it has been found that when the contrast is about 20: 1 to 25: 1, the user of the head-mounted display device has less fatigue.

The image signal (1) input from the image information source (13)
03) Vrms (or bright voltage: Vb) is detected by the voltage detection means (2), and the voltage level between the Vrms and Vref1-3 set to a desired value by the reference voltage source A (3) is compared with the comparison means A. Compare in (4).

The Vrms detection period is determined by a period selection means (32).
Can be set to one field, one frame, or an arbitrary period. When an arbitrary period is selected by the period selecting means (32), the period can be arbitrarily set by a counter or a timer. In the case of a still image, since there is almost no change in the screen state, it is sufficient to detect the image once for each frame (or more). In the case of a moving image, the state of the screen can always be detected by detecting it for each field.

Further, the period selection signal (106) output from the period selection unit (32) is input to the power supply voltage control unit (33), and the output of the power supply voltage control unit is connected to the reference voltage source A (3). If input to the comparing means A (4) and the arithmetic processing means (10), the supply of the power supply voltage can be controlled during the non-selection period, leading to a reduction in power consumption.

In (b), the state of the image signal (103) in one horizontal period is shown as an example. As a comparison result corresponding to Vref1-3, Ha1 = Vrms-Vref
1 <0, Ha2 = Vrms−Vref2> 0, Ha3 =
Vrms-Vref3> 0, and when Han> 0, a High voltage (Vcc) is output to the B / L luminance dimming means (11) when Han <0, and a Low voltage (GND) is output. Therefore, the output Ho = L, H, H of the comparing means (4).

The Ho input to the B / L luminance dimming means (11)
Is a digital SW1 provided in the B / L luminance dimming means (11).
Is input to The output (D1) of the digital SW is the resistance value of the VR (31) for adjusting the pulse width of the multivibrator (22) in the pulse width modulation according to the second embodiment described later, and the power supply voltage in the voltage modulation. VR connected to
The BLP (102) is formed by changing the set value of (31) and sent to the backlight (12) as a backlight control pulse (BLDOUT) (104). As described above, the luminance of the backlight 12 can be set to the Ho level intermittently according to the signal content (screen state: Vrms) of the image signal 103. As described above, more accurate detection can be performed by comparing with a plurality of Vrefs.

Further, the state of the display image may be fed back to the backlight luminance dimming means using a bright voltage (Vb: pedestal level voltage) instead of the effective voltage of the image signal (103). In this case, if direct feedback is made from the voltage source that determines Vb, the voltage detection means
(2) becomes unnecessary, and the circuit configuration is simplified, so that power consumption can be suppressed. Further, the state of the display image may be fed back to the backlight luminance dimming unit using both Vrms and Vb.

In FIG. 5, as for the illuminance of the surrounding environment measured by the lightning cell (5), a voltage corresponding to the illuminance is amplified by the buffer amplifier (6) and output as a voltage (Vs). The lightning cell (5) exhibits linearity up to a point where the peripheral illuminance is present (point L), but saturates and shows a constant value above the point L.

Vs is a comparison between the reference voltage (VrefB) generated by the reference voltage source B (7) and the voltage level of the reference voltage (VrefB).
(8), and the comparison result Hb = Vs−Vre
When fB> 0, the High voltage is changed to the B / L luminance dimming means.
Output to (11). In the B / L luminance dimming means (11), the result of comparison with a plurality of VrefB is input to the digital SW2. As described above, the BLDOUT (104) controlled by the output (D2) of the digital SW2 outputs the backlight (1).
The backlight brightness can be adjusted according to the Vs level of the lightning cell (5) sent to (2).

FIG. 5B illustrates a method of dimming the luminance of the backlight 12 by using the outputs D1 and D2 of the digital SW. As a result, the user can realize the optimal backlight luminance according to the use environment and condition.

In the comparing means C (9), the resistance value or the voltage value determined by the digital SW1 and the digital SW2 is compared with the resistance value or the voltage value previously set to the initial set value (S) shown in the first embodiment. The voltage values are compared with each other. D1 and S
The result of comparison with H3 (= D1-S), and the result of comparison between D2 and S H4 (= D2-S),
Enter in (10). The arithmetic processing means (10) outputs an output Ho which is an intermediate value between H3 and H4, that is, H = (H3 + H4) / 2. In the case of H3 <0 and H4 <0, SS is set in the direction of increasing the backlight luminance and at an intermediate level between H3 and H4.
Is set, there is no excessive change in the light intensity of each of H3 and H4. The output H of the arithmetic processing means (10) may be a desired value in which one of the outputs is weighted, instead of an intermediate value between H3 and H4. That is V
Since s greatly varies depending on the indoor environment used, it is often desirable to assign weights to H4 in a sense suitable for the environment. On the other hand, in the case of Vrms, it is not so important if it is considered that there is only a positive / negative display in the case of a still image, but in the case of a moving image, since Vrms changes for each field, the weighting is given. Becomes important.

Ho output from the arithmetic processing means (10) is:
The resistance value or the voltage value is changed in such a direction that the initial setting value S that determines the backlight luminance is corrected to SS by the digital SW3 in the B / L luminance dimming means (11). By changing the set value from S to SS as described above, the BLP (102) is formed, and the backlight (12) is used as the BLDOUT (104).
Vrms of the image signal (103) and Vrms of the lightning cell (5)
The backlight brightness according to s can be set.

FIG. 6 is a block diagram for explaining the content of the above (b).

According to this embodiment, by setting the pulse width of the backlight tube having the highest luminous efficiency to be the same as the pulse width of the synchronization period of the input horizontal synchronization signal, the efficiency can be improved with a simple circuit configuration. A backlight with high and low loss can be realized, and luminance dimming can be performed over a wide range by arbitrarily selecting a thinning backlight pulse.

Further, since it is possible to change the luminance of the backlight to a desired level with less fatigue according to the effective voltage level of the image signal and the peripheral illuminance level, it is possible to keep the stimulus / burst input to the eyes constant. And the burden on the eyes can be minimized. In other words, the user can realize the optimal backlight luminance according to the use environment and use condition.

Further, even if the backlight brightness is adjusted at the brightness voltage level instead of the effective voltage of the image signal, the stimulation to the user's eyes can be kept constant as described above. Further, since the circuit is simpler than in the case of the effective potential, power consumption can be suppressed.

In addition, since the detection period of the effective voltage can be arbitrarily selected, the speed of change of the screen state is slow in the case of a still image, so that it is sufficient to detect once every one frame or more (arbitrary period). In the case of a moving image, the state of the screen can be always detected by detecting each field, and the backlight luminance that matches the information of the display image can be set. Fatigue can be minimized.
Further, by controlling the supply of the power supply voltage in the non-selection period, power consumption in the non-selection period can be reduced.

(Second Embodiment) FIG. 7 is a diagram showing a dimming means in a backlight driving method of a head mounted display according to a second embodiment of the present invention. As in the above-described embodiment, the same portions are denoted by the same reference numerals, and description thereof is omitted.

Here, as a method of dimming the luminance of the backlight (12), a pulse width modulation means (50) for modulating the pulse width of the BLP (102) and a voltage applied to the backlight (12) are modulated. FIG. 9 is a block diagram for explaining a method of selecting one of the voltage modulating means (51) to be performed by a switching means (52) and outputting a BLDOUT (104) which is a control signal of the backlight (12).

The pulse width modulation means (50) and the voltage modulation means (51)
In either of the methods, since the detection means (pulse width detection means (53) and voltage detection means (54)) for detecting the modulation amount are provided, the backlight (12) operates stably. Dimming can be performed within the region (b) (stable region). Here, is a non-lighting region in which electrons cannot be sufficiently discharged in the backlight tube (12), and represents a saturation region where the discharge characteristics of the backlight tube (12) are saturated and power is wasted.

(C) is a diagram for explaining a detection method of the pulse width detection means (53). In this embodiment, the BLP (102) for operating the backlight tube (12) in the stable region is illustrated. The pulse width is set to 10 μs to 4 μs, and each limit point is set to 1
0 μs is defined as the reference pulse A and 4 μs is defined as the reference pulse B.

The BLP (102) and the inverted signal of the reference pulse A are input to the AND circuit (55), and the inverted signal of the BLP (102) and the reference pulse B are input to the AND circuit (56). For example, when BLP (102) becomes 10 μs or more, AND
Since the output of the circuit (55) becomes High and it can be determined that the reference pulse A has been exceeded, an instruction to switch the dimming method from the pulse width modulation means (50) to the voltage modulation means (51) is sent to the switching means (52). Output to the switching means (52).
The light control means is switched to the voltage modulation means (51).

According to the present embodiment, by setting the pulse width of the backlight pulse and the applied voltage within a region where the luminous efficiency of the backlight tube is always linear and stable, unnecessary power is consumed. It is not necessary to do so, and the brightness can be finely adjusted. Further, even when the dimming of the backlight by the pulse width is at a limit, by adjusting the applied voltage, more stable and fine adjustment of the luminance over a wide range can be automatically realized.

(Third Embodiment) FIG. 8 is a diagram showing a backlight pulse generating means in a backlight driving method of a head mounted display according to a third embodiment of the present invention. As in the above-described embodiment, the same portions are denoted by the same reference numerals, and description thereof is omitted.

In (a), the horizontal synchronizing signal (101) and the vertical synchronizing signal (VSYN) output from the image information source (13)
C) (111) is input to the panel drive CLK generating means (90). The panel drive CLK generating means (90) includes a liquid crystal panel
(70) Alternatively, a clock for driving a display element such as an LED array display is created. In particular, it is the signal DXCLK (108) that determines the writing position (timing) of the image information in the horizontal direction on the liquid crystal panel (70), and the image information is synchronized with the falling edge of the DXCLK (108). Is written out.

The DXCLK (108) created by the panel drive CLK creating means (90) is twice as large as the DXCLK (108) by the counter (21), as in the case described in the second embodiment. Q1, Q2, and Q3 synchronized with the quadruple and octuple cycles are output, respectively. Next, multivibrator (MB)
In (22), the falling positions of four signals obtained by combining the Q1 to Q3 and the original DXCLK (108), and the DXCLK (108)
Pulse (M1, M2, M3, M4) of 1 / n cycle of DXCLK (108) set in synchronization with the falling position of DXCLK (108). M
The outputs M1 to M4 of B (22) are arbitrarily selected by the user (61) by the switching SW (23) and sent to the backlight (12) as BLPP (105).

(B) shows an example of a cycle twice as long as DXCLK (108).

Horizontal blanking period (K) of image signal (103)
Is composed of a front porch (FP), an HSYNC (101), and a back porch (BP). On the contrary,
DXCLK (108) has a phase relationship such that the falling position of DXCLK (108) overlaps the end of the BP period (the position where the display area starts). This DXCLK (108)
BLPP (105) synchronized with the falling edge of BL
As compared with P (104), the pulse width of the backlight pulse can be made wider by BP, and a wider adjustment range can be secured.

According to the present embodiment, the backlight pulse synchronized with the horizontal synchronizing signal of an intelligent device having a CPU such as a personal computer or a portable device has a short synchronizing period (pulse width) of the horizontal synchronizing signal. If the pulse width of the backlight pulse is too long to increase the brightness, the backlight pulse will be applied to the display area over the retrace period, and the effect of spike noise, which is likely to occur at the rising and falling parts of the backlight pulse More easily.

Therefore, the falling edge of the backlight pulse is synchronized with the falling edge of DXCLK which determines the horizontal display writing in the liquid crystal panel. The backlight pulse can completely cover the front and back porch before and after the display area and can prevent the backlight pulse from being over in the display area, so that there is no influence of spike noise on the display screen and visibility is improved. A rich display can be provided. Further, fine adjustment of the luminance can be performed over a wider range.

[Brief description of the drawings]

FIG. 1 is a side view illustrating a mounted state of a head-mounted display device.

2A and 2B are diagrams illustrating a virtual image forming optical system of the head mounted display device, wherein FIG. 2A is a cross-sectional view of a closed type, and FIG. 2B is a cross-sectional view of a see-through type.

FIG. 3 is a diagram showing a backlight pulse generating means according to the first embodiment of the present invention, wherein (a) is a block diagram,
(B) is a timing chart.

4A and 4B are diagrams illustrating a method of dimming a backlight using an effective voltage of an image signal according to the first embodiment of the present invention. FIG. 4A is a block diagram, and FIG. 4B is a diagram illustrating a relationship between an effective voltage and a reference voltage. FIG. 3C is a diagram for explaining the relationship between the effective voltage and the backlight luminance.

FIGS. 5A and 5B are diagrams illustrating a method of dimming the backlight luminance based on the effective voltage and the peripheral illuminance according to the first embodiment of the present invention. FIG. 5A is a diagram illustrating an output of an electric light cell, and FIG. FIG. 6 is a diagram for explaining a method of dimming backlight luminance from a state of peripheral illuminance to an intermediate point between the two.

FIG. 6 is a block diagram illustrating a method for dimming backlight luminance based on an effective voltage and ambient illuminance according to the first embodiment of the present invention.

FIGS. 7A and 7B are diagrams illustrating a dimming method according to a second embodiment of the present invention, wherein FIG. 7A is a block diagram, FIG. 7B is a diagram illustrating the light emission characteristics of a backlight tube, and FIG. The figure explaining a means.

FIG. 8 is a diagram showing a backlight pulse generating means according to a third embodiment of the present invention, wherein (a) is a block diagram,
(B) is a timing chart.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 backlight pulse creating means 2 voltage detecting means 3 reference voltage source A 4 comparing means A 5 lightning cell 6 buffer amplifier 7 reference voltage source B 8 comparing means B 9 comparing means C 10 arithmetic processing means 11 B / L brightness dimming means REFERENCE SIGNS LIST 12 backlight 13 image information source of intelligent device 14 image information source of NTSC video device 20 synchronization separation circuit 21 counter 22 multivibrator 23 switching SW 31 VR 32 period selection means 33 power supply voltage control means 50 pulse width modulation means 51 voltage Modulation means 52 Switching means 53 Pulse width detection means 54 Voltage detection means 55 AND circuit 56 AND circuit 60 Device main body 61 User 62 Virtual image forming optical system 63 Hinge part 64 Forehead pad 65 Arm 66 Slider 67 Ear pad 68 Mounting means 70 Liquid crystal panel 71 Image display element 72 Reflecting mirror 73 Lens 74 Magnified virtual image 80 Concave mirror 81 Half mirror 82 Visor 90 Panel drive CLK generating means 101 HSYNC of intelligent device 102 BLP 103 Image signal 104 BLDOUT 105 BLPP 106 Period selection signal 108 DXCLK 111 VSYNC 112 NTSC system HSYNC for video equipment

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/64 511 H04N 5/64 511A 5/66 102 5/66 102A

Claims (13)

[Claims] An image display device comprising a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind, and an optical device for enlarging an image formed by the image display device, are provided in the apparatus body. In the backlight driving method for the stored head mounted display device, a backlight driving circuit for driving the backlight comprises:
A backlight driving method for a head-mounted display device, wherein the luminance of the backlight is changed according to an effective voltage (or a bright voltage) of an image signal to be displayed on the image display element. 2. An apparatus main body comprising: an image display element having a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind; and an enlargement optical unit for enlarging an image formed by the image display element. In the backlight driving method for the stored head mounted display device, a backlight driving circuit for driving the backlight comprises:
A first comparison result of comparing the output of the illuminance detecting means for detecting the ambient illuminance with the first reference voltage, an effective voltage (or bright voltage) of an image signal to be displayed on the image display element, and a second A backlight driving method for a head-mounted display device, wherein the luminance of the backlight is determined based on a second comparison result obtained by comparing with a reference voltage. 3. The backlight driving circuit includes voltage detecting means for detecting an effective voltage or a bright voltage of the image signal, and comparing means for comparing a reference voltage with an output of the voltage detecting means. When the effective voltage (or the bright voltage) is lower than the reference voltage, the brightness of the backlight is lower than the first luminance of the backlight when the effective voltage (or the bright voltage) is higher than the reference voltage. The backlight driving method for a head-mounted display device according to claim 1, wherein the luminance is set to a high second luminance. 4. The effective voltage (or the bright voltage).
4. The backlight driving method for a head-mounted display device according to claim 1, wherein the detection period is set to coincide with one field period of the image signal. 5. The effective voltage (or the bright voltage).
4. The backlight driving method for a head mounted display according to claim 1, wherein the detection period is set to coincide with one frame period of the image signal. 6. The backlight driving method for a head-mounted display device according to claim 3, wherein said reference voltage is a plurality of voltages. 7. The backlight driving method for a head mounted display according to claim 2, wherein each of said first and second reference voltages is a plurality of voltages. 8. An apparatus main body comprising: an image display device having a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind; and an enlargement optical unit for enlarging an image formed by the image display device. In the backlight driving method for the stored head mounted display device, a backlight driving circuit for driving the backlight comprises:
When the surrounding illuminance is high, the backlight is driven so as to have a first brightness, and when the surrounding illuminance is low, the backlight is driven so as to have a second brightness lower than the first brightness. A backlight driving method for a head-mounted display device. 9. An apparatus main body comprising: an image display device having a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind; and an enlargement optical unit for enlarging an image formed by the image display device. In the backlight driving method for the stored head mounted display device, a backlight driving circuit for driving the backlight comprises:
A plurality of backlight pulses having different periods are created based on a horizontal synchronization signal of image information to be displayed on the image display element, and the backlight is driven based on the backlight pulse selected from the plurality of backlight pulses. A backlight driving method for a head-mounted display device, comprising: adjusting a luminance of the backlight. 10. The backlight driving circuit includes pulse width modulation means for modulating a pulse width of the selected backlight pulse, and voltage modulation means for modulating a backlight power supply voltage applied to the backlight. 10. The head mounted device according to claim 9, wherein the backlight is driven by selecting the pulse width modulation means and the output of the voltage modulation means so that the backlight is stably turned on. Backlight driving method for a display device. 11. The backlight driving circuit according to claim 1, wherein the backlight driving circuit operates in synchronization with a clock that defines a timing at which data is displayed on the pixels of the liquid crystal panel. A backlight driving method for a head-mounted display device. 12. The head-mounted type according to claim 6, wherein power supplied to at least one of said reference voltage and said comparing means is cut off when said voltage detecting means is not operating. A backlight driving method for a display device. 13. An image display device comprising a liquid crystal panel and a backlight for irradiating the liquid crystal panel from behind,
In a head-mounted display device in which a magnifying optical unit for enlarging an image formed by the image display element is housed in a device main body, a backlight drive circuit for driving the backlight displays the image on the image display element. A head mounted display device, wherein brightness of the backlight is changed according to an effective voltage (or a bright voltage) of an image signal to be outputted.