JPH11337897A - Projection liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the loss for reduction of the brightness of projected picture, to improve the use efficiency of light emitted from a light source, and to reduce the noise due to air cooling for suppression of the temperature rise caused by the light source or heat generation due to the loss in a liquid crystal panel. SOLUTION: An adjustment means automatic switching circuit is provided which consists of a brightness control circuit 9 which performs automatic switching to adjustment of the brightness of the projection picture due to a lamp luminance control voltage generation circuit 3a or that due to a contrast control voltage generation circuit 8a based on a threshold prescribing a prescribed brightness of the projection picture, diodes 904 and 906, a threshold generator 907, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the loss of light emitted from a lamp, which is a light source, when passing through a liquid crystal panel, improves the use efficiency of the light, and reduces the heat generated by the loss. The present invention relates to a projection-type liquid crystal display device capable of reducing air-cooling noise that suppresses temperature rise.

[0002]

2. Description of the Related Art FIG. 6 is a circuit block diagram showing a configuration of a conventional projection type liquid crystal display device. 6, reference numeral 1 denotes a lamp as a light source, 2 denotes a lamp driving power supply for driving the lamp 1, and 3 denotes a lamp luminance adjusting voltage for generating a lamp luminance adjusting voltage for controlling a current value of the lamp 1 in the lamp driving power supply 2. It is a generation circuit. Reference numeral 301 denotes an operational amplifier of the lamp luminance adjustment voltage generation circuit 3, reference numerals 302 and 303 denote external resistors of the operational amplifier 301, and reference numeral 304 denotes a lamp luminance controller for generating a DC voltage for lamp luminance control. Reference numeral 4 denotes a liquid crystal panel, and reference numeral 5 denotes an optical system of the projection type liquid crystal display device. 6
Is a projection lens, 7 is a contrast adjustment circuit that adjusts the amplitude of the liquid crystal drive signal by a DC voltage, and 8 is a contrast adjustment voltage generation circuit that outputs the DC voltage that adjusts the amplitude of the liquid crystal drive signal. Reference numeral 801 denotes an operational amplifier of the contrast adjustment voltage generation circuit 8, reference numerals 802 and 803 denote external resistors, and reference numeral 804 denotes a contrast adjuster for generating a DC voltage for contrast adjustment.

Next, the operation will be described. Light emitted from a lamp 1, which is a light source of the projection type liquid crystal display device, passes through an optical system 5, passes through a liquid crystal panel 4, and becomes a display image light by a liquid crystal panel drive signal applied to the liquid crystal panel 4 at this time. The light is projected on the screen by the projection lens 6.

A lamp drive power supply 2 drives the lamp 1 and supplies a constant current to the lamp 1 according to the DC voltage generated by the lamp brightness adjustment voltage generation circuit 3. At this time, the lamp brightness adjustment voltage is adjusted by changing the DC voltage value generated by the lamp brightness controller 304 of the lamp brightness adjustment voltage generation circuit 3, and the lamp brightness adjustment voltage is supplied from the lamp brightness adjustment voltage generation circuit 3 to the lamp driving circuit. The power is supplied to the power supply 2. FIG. 7 is a characteristic diagram showing the output voltage of the lamp brightness adjustment voltage generation circuit 3 versus the lamp brightness.

On the other hand, a display image signal for displaying an image on the liquid crystal panel 4 is input to a contrast adjusting circuit 7, the amplitude of which changes according to the DC voltage output from the contrast adjusting voltage generating circuit 8, and As a drive signal. The contrast adjustment voltage generation circuit 8 adjusts the DC voltage value generated by the contrast adjuster 804 to vary the contrast adjustment voltage.
This contrast adjustment voltage is supplied to the contrast adjustment circuit 7. FIG. 8 shows a contrast adjustment voltage generation circuit 8.
3 is a characteristic diagram of the output versus the amplitude of the display image signal. FIG.

In the conventional projection type liquid crystal display device, the lamp brightness is adjusted by a lamp brightness adjusting voltage generating circuit 3 and a lamp driving power supply 2, and the amplitude of the driving signal is adjusted by a contrast adjusting circuit 7 and a contrast adjusting voltage generating circuit 8. Brightness adjustment is performed independently. The operation of adjusting the brightness of a display image by a user using a remote controller or the like is usually performed by adjusting the amplitude of a drive signal to the liquid crystal panel 4.

[0007]

Since the conventional projection type liquid crystal display device is configured as described above, when lowering the brightness of a displayed image, the luminance of the lamp 1 as a light source is maintained at the current level (generally). The variable range is narrower), the amplitude of the drive signal to the liquid crystal panel 4 is reduced, and the amount of light passing through the liquid crystal panel is reduced, so that the light emitted from the lamp 1 as a light source is There is a problem in that the loss due to passing through the plate 4 becomes heat and the light use efficiency is reduced. Also, there is a problem that a fan for suppressing the heating of the liquid crystal panel and the lamp by the heat needs to have a large capacity and a large noise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and reduces the loss when the brightness of a projected image is reduced, improves the use efficiency of light emitted from a light source, It is another object of the present invention to provide a projection type liquid crystal display device capable of reducing noise caused by air cooling for suppressing a rise in temperature due to loss of heat in the light source and the liquid crystal panel.

[0009]

A projection type liquid crystal display device according to the present invention adjusts the brightness of a projected image by light source brightness adjusting means or adjusts the brightness of the projected image based on a threshold value defining a predetermined brightness of the projected image. An adjusting means automatic switching circuit for automatically switching to the adjustment by the signal amplitude adjusting means is provided.

In the projection type liquid crystal display device according to the present invention, when the brightness of the projected image is adjusted to the brightness equal to or more than the threshold value, the amplitude of the image signal is fixed to the maximum by the image signal amplitude adjusting means. When the brightness of the projected image is adjusted by switching to the adjustment by the light source brightness adjusting unit, and the brightness of the projected image is adjusted to be equal to or less than the threshold value, the brightness of the light source is fixed to the minimum by the light source brightness adjusting unit. And an adjusting means automatic switching circuit for adjusting the brightness of the projected image by switching to the adjustment by the image signal amplitude adjusting means in the state where the image signal amplitude is adjusted.

A projection type liquid crystal display device according to the present invention includes a projection zoom lens, zoom ratio detection means for detecting a zoom ratio of the projection zoom lens, and a zoom ratio detected by the zoom ratio detection means. And a threshold switching means for switching a threshold for defining a predetermined brightness of the projection image.

In the projection type liquid crystal display device according to the present invention, the number of rotations of the cooling fan is varied according to the cooling fan for cooling the light source and the liquid crystal panel and the brightness of the light source adjusted by the light source brightness adjusting means. The cooling fan adjusting means is provided.

According to the projection type liquid crystal display device of the present invention, a light source brightness adjusting means for adjusting the brightness of a projected image by changing the brightness of a light source, and displaying the brightness of the projected image on a liquid crystal panel. Image signal amplitude adjusting means for adjusting by changing the amplitude of the image signal to be applied; a cooling fan for cooling the light source and the liquid crystal panel; and a cooling fan for adjusting the brightness of the light source by the light source brightness adjusting means. Cooling fan adjusting means for varying the rotation speed of the cooling fan.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. Embodiment 1 FIG. FIG. 1 is a circuit block diagram showing a configuration of the projection type liquid crystal display device according to the first embodiment. In FIG. 1, reference numeral 1 denotes a lamp as a light source, 2 denotes a lamp driving power supply for driving the lamp 1, and 3a denotes a lamp luminance adjusting voltage for generating a lamp luminance adjusting voltage for controlling a current value of the lamp 1 in the lamp driving power supply 2. It is a generation circuit (light source luminance adjusting means). Reference numeral 301 denotes a lamp brightness adjustment voltage generation circuit 3a.
, And 302 and 303 are external resistors of the operational amplifier 301. Reference numeral 4 denotes a liquid crystal panel, and reference numeral 5 denotes an optical system of the projection type liquid crystal display device. 6 is a projection lens, 7 is a contrast adjustment circuit (image signal amplitude adjustment means) for adjusting the amplitude of the liquid crystal drive signal by a contrast adjustment voltage, and 8a is a contrast adjustment voltage generation circuit (image signal amplitude adjustment means) for outputting the contrast adjustment voltage. ). 801
Is an operational amplifier of the contrast adjustment voltage generation circuit 8a;
02 and 803 are external resistors of the operational amplifier 801.

9 is a brightness adjustment circuit (adjustment means automatic switching circuit), 901 is a buffer amplifier, 902 is a brightness adjuster, 903 and 905 are resistors inserted into the output of the buffer amplifier 901, and 904 and 906 are diodes ( Reference numeral 907 denotes a threshold generator (adjustment unit automatic switching circuit).

Next, the operation will be described. The brightness controller 902 generates a DC voltage corresponding to the brightness to be adjusted, and outputs it as a brightness adjustment voltage via the buffer amplifier 901 and the resistors 903 and 905. The brightness adjustment voltage supplied via the resistor 905 is sliced by a slice circuit including a diode 906 and a threshold generator 907 with the voltage level generated by the threshold generator 907 as a substantially threshold value, and Until the voltage reaches the voltage level generated by the threshold generator 907, the constant voltage signal of the voltage level generated by the threshold generator 907 and the brightness adjustment voltage exceed the voltage level. The brightness adjustment voltage is supplied to the non-inverting input terminal of the operational amplifier 301 of the lamp brightness adjustment voltage generation circuit 3a. In the lamp brightness adjusting voltage generating circuit 3a, the supplied constant voltage signal or the brightness adjusting voltage is supplied to the operational amplifier 3.
Amplified at an amplification factor defined by an external resistor 302 and an external resistor 303 of No. 01 and supplied to the lamp driving power supply 2, and the lamp driving power supply 2 adjusts the lamp brightness. FIG.
The characteristic indicated by the solid line of FIG.
5 shows the characteristics of the lamp brightness in the lamp driving power supply 2 with respect to the output of FIG. As described above, the adjustment range of the brightness of the lamp 1 is adjusted by the lamp driving power supply 2 to a range equal to or higher than the brightness corresponding to the threshold set by the voltage level generated by the threshold generator 907, and is constant below the threshold. Is maintained.

On the other hand, the brightness adjustment voltage output via the resistor 903 is output by the slice circuit including the diode 904 and the threshold generator 907 until the brightness level reaches the voltage level generated by the threshold generator 907. The adjustment voltage is the operational amplifier 801 of the contrast adjustment voltage generation circuit 8a.
Is supplied to the non-inverting input terminal of the AMP, and when the brightness level becomes equal to or higher than the voltage level generated by the threshold generator 907, the brightness adjustment voltage is fixed to the voltage level generated by the threshold generator 907, and It is supplied to the non-inverting input terminal. When the voltage of the threshold generator 907 is supplied to the contrast adjustment voltage generation circuit 8a, the amplitude of the liquid crystal drive signal adjusted by the contrast adjustment circuit 7 becomes maximum. The characteristic shown by the solid line in FIG. 3 indicates the output amplitude characteristic of the contrast adjustment circuit 7 versus the output of the contrast adjustment voltage generation circuit 8a. Therefore, the drive signal supplied to the liquid crystal panel 4 has the maximum amplitude when the brightness adjustment voltage is equal to or more than the threshold corresponding to the voltage level generated by the threshold generator 907, and the brightness adjustment voltage is When the voltage is equal to or less than the threshold value, the amplitude is adjusted to the amplitude corresponding to the voltage value at that time.

As described above, when the brightness adjustment voltage set by the brightness adjuster 902 adjusts the brightness in a range equal to or higher than the threshold set by the voltage level generated by the threshold generator 907, Is performed by adjusting the brightness of the lamp 1 by the lamp driving power supply 2, and when adjusting the brightness in the range equal to or less than the threshold, the adjustment is performed by the amplitude of the liquid crystal driving signal supplied to the liquid crystal panel 4.

As described above, according to the first embodiment, the adjustment of the brightness of the display image exceeds the predetermined brightness represented by the threshold corresponding to the voltage level generated by threshold generator 907. The adjustment is performed by adjusting the brightness of the lamp 1, and at this time, the amplitude of the liquid crystal drive signal is maximized. In addition, when the adjustment is performed in the range of the predetermined brightness or less, the adjustment is performed by adjusting the amplitude of the liquid crystal driving signal. Therefore, the light source is a light source for adjusting the brightness of the display image beyond the predetermined brightness. It is possible to reduce a loss when light emitted from the lamp passes through the liquid crystal panel.
Therefore, there is an effect that a projection type liquid crystal display device with improved light use efficiency can be obtained.

Embodiment 2 FIG. 4 shows the second embodiment.
1 is a circuit block diagram illustrating a configuration of a projection type liquid crystal display device. 4, the same or corresponding parts as in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In FIG.
Reference numeral 08 denotes a second threshold generator (adjustment unit automatic switching circuit) connected in parallel with the threshold generator 907. The DC voltage value generated by the second threshold generator 908 is a lower voltage value (lower threshold) than the DC voltage value generated by the threshold generator 907. Reference numeral 909 denotes a switch (threshold switching unit), 10 denotes a zoom lens (projection zoom lens), 11 denotes a zoom ratio detection plate (zoom ratio detection unit), and 12 denotes a photo interrupter (zoom ratio detection unit).

The zoom lens 10 rotates in the range indicated by the arrow in FIG. 4 to change the zoom ratio. The photo interrupter 12 is provided corresponding to the range of the zoom ratio from the minimum to a predetermined size, and the zoom ratio detecting plate 11 is located between the photo interrupters 12 in accordance with the rotation of the zoom lens 10, that is, at the time of reduced display. Is to be detected. The output of the photo interrupter 12 is supplied to a switch 909 of the brightness adjustment circuit 9. Switch 909 is a threshold generator 90
7 and the second threshold generator 908 are switched by the output of the photointerrupter 12 to the second threshold generator 908 having a lower (darker) DC voltage value to be generated during reduced display. At the time of reduced display, the display area is smaller than the enlarged display, so that the brightness is increased, so that the brightness of the lamp can be further reduced. 2 and FIG. 3 are the characteristics when the operation is switched to the second threshold generator 908.
For this reason, at the time of reduced display, the threshold value corresponding to the voltage level generated by the threshold value generator can be lowered to reduce the brightness of the lamp, and adjustment is performed in a range of a predetermined brightness or less represented by the threshold value. The light emitted from the lamp 1 as a light source at the time can be reduced in loss when passing through the liquid crystal panel, and there is an effect that a projection type liquid crystal display device with improved light use efficiency can be obtained.

Embodiment 3 FIG. FIG. 5 shows the third embodiment.
1 is a circuit block diagram illustrating a configuration of a projection type liquid crystal display device. In FIG. 5, the same or corresponding parts as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Embodiment 3
Does not include the brightness adjustment circuit 9. In FIG. 5, reference numeral 3 denotes a lamp brightness adjustment voltage generation circuit (light source brightness adjustment means, cooling fan adjustment means) for generating a lamp brightness adjustment voltage for controlling the current value of the lamp 1 in the lamp drive power supply 2. Reference numeral 8 denotes a contrast adjustment voltage generation circuit (image signal amplitude adjustment means) that outputs a DC voltage for adjusting the amplitude of the liquid crystal drive signal to the contrast adjustment circuit 7. Reference numeral 304 denotes a lamp brightness controller for generating a DC voltage for lamp brightness adjustment, and reference numeral 804 denotes a contrast controller for generating a DC voltage for contrast adjustment. Also, 21 and 22 are cooling fans, and 23 is cooling fans 21 and
Drive power supply (drive fan adjusting means for cooling)
It is.

Next, the operation will be described. The cooling fan 21 cools the liquid crystal panel 4, and the cooling fan 22 cools the lamp 1. The fan drive power supply 23 generates a voltage for driving the cooling fans 21 and 22. The output of the lamp brightness adjustment voltage generation circuit 3 is supplied to the fan drive power supply 23, and in accordance with the brightness adjustment of the lamp 1, the voltage level applied to the cooling fans 21 and 22 is reduced as the brightness is reduced. To reduce noise generated by the rotation of the fan.

As described above, according to the third embodiment, when the lamp luminance is reduced, the number of rotations of the cooling fans 21 and 22 is also reduced, so that the projection type liquid crystal display capable of suppressing the noise generated by the rotation of the fans. There is an effect that the device can be obtained.
In the above description, the brightness adjustment circuit 9 is not provided. However, the brightness adjustment circuit 9, the lamp brightness adjustment voltage generation circuit 3, and the contrast adjustment voltage described in FIG. The present invention can be applied to the configuration of the generation circuit 8. In this case, the output of the lamp brightness adjustment voltage generation circuit 3 is supplied to the fan drive power supply 23.

[0025]

As described above, according to the present invention, the brightness of the projected image is adjusted by the light source brightness adjusting means or the image signal amplitude adjusting means is set based on the threshold value which defines the predetermined brightness of the projected image. , An adjustment means automatic switching circuit for automatically switching to the adjustment of the brightness of the projected image by the control means, the adjustment by the light source luminance adjustment means and the image signal amplitude adjustment means, and the switching by the adjustment means automatic switching circuit Is performed so as to reduce the loss when the brightness of the projected image is reduced, so that the loss in the light source and the liquid crystal panel can be reduced, and the utilization efficiency of the light emitted from the light source can be reduced. There is an effect of improving.

According to this invention, when the brightness of the projected image is adjusted to the brightness equal to or higher than the threshold value, the light source brightness adjusting means keeps the amplitude of the image signal fixed to the maximum by the image signal amplitude adjusting means. When the brightness of the projection image is adjusted by switching to adjustment, and the brightness of the projection image is adjusted to a brightness equal to or less than a threshold, the brightness of the light source is fixed to a minimum by the light source brightness adjustment unit, Since it is configured to include an adjustment unit automatic switching circuit that adjusts the brightness of the projection image by switching to adjustment by the image signal amplitude adjustment unit, it is possible to reduce loss in the light source and the liquid crystal panel, There is an effect that the utilization efficiency of the light emitted from is improved.

According to the present invention, the threshold value switching means for switching the threshold value for defining the predetermined brightness of the projection image based on the zoom ratio detected by the zoom ratio detection means is provided. Since the display area is small compared to the enlarged display, the brightness is increased and the brightness of the light source is reduced so that the loss at the light source can be reduced, and the light emitted from the light source can be reduced. This has the effect of improving the efficiency of use.

According to the present invention, the cooling fan for cooling the light source and the liquid crystal panel, and the cooling fan adjusting means for varying the rotation speed of the cooling fan in accordance with the adjustment of the brightness of the light source by the light source brightness adjusting means. When the brightness of the light source is reduced by the light source brightness adjusting means, the rotation speed of the cooling fan is also reduced, so that the loss in the light source and the liquid crystal panel becomes heat. Therefore, there is an effect that noise due to air cooling for suppressing a temperature rise due to the above can be reduced.

According to the present invention, the brightness of the projected image is
Light source luminance adjusting means for adjusting by changing the luminance of the light source; image signal amplitude adjusting means for adjusting the brightness of the projected image by changing the amplitude of an image signal for displaying an image on a liquid crystal panel; Since the cooling fan for cooling the liquid crystal panel and the cooling fan adjusting means for changing the rotation speed of the cooling fan in accordance with the adjustment of the brightness of the light source by the light source brightness adjusting means are provided, When the brightness of the light source is adjusted to lower the brightness by the light source brightness adjusting means, the rotation speed of the cooling fan is also reduced, thereby increasing the temperature due to the loss of heat in the light source and the liquid crystal panel becoming heat. Therefore, there is an effect that noise due to air cooling for suppressing the noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a projection type liquid crystal display device according to Embodiment 1 of the present invention.

FIG. 2 is a characteristic diagram showing an output of a lamp brightness adjustment voltage generation circuit in the projection type liquid crystal display device according to the first embodiment of the present invention and a lamp brightness in a lamp driving power supply.

FIG. 3 is a characteristic diagram showing an output of a contrast adjustment voltage generation circuit and an output amplitude characteristic of the contrast adjustment circuit in the projection type liquid crystal display device according to the first embodiment of the present invention.

FIG. 4 is a circuit block diagram showing a configuration of a projection type liquid crystal display device according to Embodiment 2 of the present invention.

FIG. 5 is a circuit block diagram showing a configuration of a projection type liquid crystal display device according to Embodiment 3 of the present invention.

FIG. 6 is a circuit block diagram showing a configuration of a conventional projection type liquid crystal display device.

FIG. 7 is a characteristic diagram showing output voltage versus lamp luminance of a lamp luminance adjustment voltage generation circuit in a conventional projection type liquid crystal display device.

FIG. 8 is a characteristic diagram of an output of a contrast adjustment voltage generation circuit and an amplitude of a display image signal in a conventional projection type liquid crystal display device.

[Description of Signs] 1 lamp (light source), 3a lamp brightness adjustment voltage generation circuit (light source brightness adjustment means), 3 lamp brightness adjustment voltage generation circuit (light source brightness adjustment means, cooling fan adjustment means), 4
Liquid crystal panel, 7 contrast adjustment circuit (image signal amplitude adjustment means), 8a, 8 contrast adjustment voltage generation circuit (image signal amplitude adjustment means), 9 brightness adjustment circuit (adjustment means automatic switching circuit), 10 zoom lens (for projection) Zoom lens), 11 zoom ratio detection plate (zoom ratio detection means), 12 photo interrupter (zoom ratio detection means), 21, 22 cooling fan, 23 fan drive power supply (cooling fan adjustment means), 904, 906 diode ( An automatic switching circuit for adjusting means), a threshold generator (automatic switching circuit for adjusting means) 907, a second threshold generator (automatic switching circuit for adjusting means), and a switch 909 (threshold switching means).

Claims (5)

[Claims] 1. A projection type liquid crystal display device for transmitting light emitted from a light source through a liquid crystal panel and projecting an output image displayed on the liquid crystal panel as a projection image, wherein the brightness of the projection image is adjusted by the light source. Light source luminance adjusting means for adjusting the brightness of the projected image; image signal amplitude adjusting means for adjusting the brightness of the projected image by changing the amplitude of an image signal for displaying an image on the liquid crystal panel; An adjustment means automatic switching circuit for automatically switching the brightness of the projection image to an adjustment by the light source brightness adjustment means or an adjustment by the image signal amplitude adjustment means based on a threshold value defining a predetermined brightness of the projection image. A projection type liquid crystal display device. An adjusting means for automatically changing a brightness of the light source in a state where the amplitude of the image signal is fixed to a maximum by the image signal amplitude adjusting means when the brightness of the projection image is adjusted to a brightness not less than a threshold value; When the brightness of the projected image is adjusted by switching to the adjustment by the adjusting means, and the brightness of the projected image is adjusted to be equal to or less than the threshold, the brightness of the light source is fixed to the minimum by the light source brightness adjusting means. 2. The projection type liquid crystal display device according to claim 1, wherein the brightness of the projection image is adjusted by switching to adjustment by the image signal amplitude adjustment means. 3. A zoom lens for projection, a zoom ratio detecting means for detecting a zoom ratio of the zoom lens for projection, and a zoom ratio detected by the zoom ratio detecting means.
3. The projection type liquid crystal display device according to claim 1, further comprising a threshold value switching unit that switches a threshold value that defines a predetermined brightness of the projection image. 4. A cooling fan for cooling a light source and a liquid crystal panel, and a cooling fan adjusting means for varying the number of revolutions of the cooling fan in accordance with the adjustment of the light source brightness by the light source brightness adjusting means. 4. The method according to claim 1, wherein
13. The projection type liquid crystal display device according to claim 1. 5. A projection-type liquid crystal display device for transmitting light emitted from a light source through a liquid crystal panel and projecting an output image displayed on the liquid crystal panel as a projection image, wherein the brightness of the projection image is adjusted by the light source. A light source luminance adjusting unit that adjusts by changing the luminance of the image signal; an image signal amplitude adjusting unit that adjusts the brightness of the projected image by changing the amplitude of an image signal that displays an image on the liquid crystal panel; A cooling fan that cools the liquid crystal panel; and a cooling fan adjustment unit that varies a rotation speed of the cooling fan in accordance with adjustment of the brightness of the light source by the light source brightness adjustment unit. The projection type liquid crystal display device according to claim 4.