JP2003005146A - Optical modulation device and picture projection device, and cooling method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical modulation device and a picture projection device which are very quiet, and are capable of being reduced in power consumption and also being surely cooled, and to provide a cooling method therefor. SOLUTION: Among the light emitted from a liquid crystal panel 14, an analyzer 15 absorbs the light other than linearly polarized light in the specified direction of polarization. The absorbed light turns into thermal energy. An air-cooling fan 18 cools mainly an polarizer 13, the liquid crystal panel 14, and the analyzer 15. The same picture signal 20 as inputted to the liquid crystal panel 14 is inputted to an air-cooling fan control circuit 19. The air-cooling fan control circuit 19 controls the voltage Vf to be applied to the air-cooling fan based on the brightness level of the picture signal 20, to control the rotating speed of the air-cooling fan, and adjusts the cooling airflow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical modulator including an optical modulator for modulating light emitted from a light source based on an image signal or the like and having a cooling function for cooling heat generated in the apparatus, The present invention relates to an image projection device and a cooling method thereof.

[0002]

2. Description of the Related Art A liquid crystal display element (hereinafter referred to as a liquid crystal panel) that controls the polarization of light by utilizing the birefringence of liquid crystal and performs optical modulation is widely used. In recent years, using this liquid crystal panel, the light from the light source is modulated based on the image signal,
2. Description of the Related Art Liquid crystal projectors (projection type liquid crystal display devices) that display an image by projecting modulated light on a screen have become widespread. Here, the configuration of the liquid crystal projector will be briefly described.

FIG. 10 shows a configuration example of a conventional liquid crystal projector. In this liquid crystal projector, unpolarized light emitted from a light source 101 such as a discharge lamp passes through an illumination optical system 102 and enters a polarizer 103. The polarizer 103 is designed to pass only linearly polarized light having a specific polarization direction. The linearly polarized light that has passed through the polarizer 103 enters the liquid crystal panel 104. The liquid crystal panel 104 modulates incident light based on the supplied image signal 120. Of the modulated light emitted from the liquid crystal panel 104, only linearly polarized light in a specific polarization direction passes through the analyzer 105, is projected onto the screen 107 by the projection lens 106, and is displayed as an image. .

The image display method of the liquid crystal projector will be described in more detail with reference to FIG. FIG. 11 shows
Liquid crystal panel 1 in the liquid crystal projector shown in FIG.
The cross-sectional configuration example of the peripheral portion of 04 is shown. LCD panel 1
Reference numeral 04 denotes a transmissive type using TN (twisted nematic) liquid crystal, and is configured by enclosing nematic liquid crystal in a twisted state between two substrates (not shown) inside. The polarizer 103 and the analyzer 105 are arranged so that the transmission axes of light are orthogonal to each other, that is, in a so-called orthogonal Nicol relationship. The transmission axis of the polarizer 103 is set to be in the same direction as the alignment direction of liquid crystal molecules at the interface between the incident side substrate of the liquid crystal panel 104 and the liquid crystal layer. On the other hand, the transmission axis of the analyzer 105 is the liquid crystal panel 104.
It is set so as to be in the same direction as the alignment direction of the liquid crystal molecules at the interface between the substrate on the output side and the liquid crystal layer.

In such a structure, when the irradiation light L0 from the light source 101 enters the polarizer 103, the polarizer 10
Only the linearly polarized light component 111 having the same vibration direction as the transmission axis of 3 passes through the polarizer 103. On the other hand, the light component 112 in the vibration direction orthogonal to the transmission axis of the polarizer 103 is
It is absorbed by 3 and does not penetrate. The light component 111 transmitted through the polarizer 103 then enters the liquid crystal panel 104.

Here, in a normal state in which a voltage is not applied to the liquid crystal layer in the liquid crystal panel 104, optical twisting occurs due to the twist of the liquid crystal, and the vibration direction of light is rotated by 90 ° along the twist of the liquid crystal. . As a result, the light emitted from the liquid crystal panel 104 has its vibration direction in the same direction as the transmission axis of the analyzer 105 and is transmitted through the analyzer 105. The light transmitted through the analyzer 105 is projected by the projection lens 106.
It is projected on the screen 107 via. At this time, the display state of the image is a so-called white level display. On the other hand, when the liquid crystal panel 104 is in an energized state in which a voltage is applied to the liquid crystal layer, the alignment state of the liquid crystal molecules is changed so that the long axis of the molecule is in the same direction as the optical axis 113.
The optical activity is lost. Therefore, the linearly polarized light component 111 that has passed through the polarizer 103 exits the liquid crystal panel 104 while maintaining its vibration direction, as shown in FIG. The light emitted in the state where the vibration direction is maintained is analyzed by the analyzer 105.
Absorbed by and not transmitted. At this time, the display state of the image is a so-called black level display. As described above, in the liquid crystal panel 104, a display method in which light is transmitted in a normal state in which a voltage is not applied to the liquid crystal layer and white level display is performed is generally called “normally white”.

In order to realize a high brightness liquid crystal projector, a light source 101 having a large light output is used, so that light of large energy is input to an absorption type polarizing plate used as a polarizer 103 and an analyzer 105. However, the absorption of light will increase and the temperature will rise. If the temperature of the polarizing plate rises and exceeds a certain heat resistant temperature for a long time, it may be denatured, and it becomes impossible to function as the polarizer 103 and the analyzer 105. As a result, for example, a phenomenon such as a deterioration in brightness, a decrease in contrast, a brightness unevenness in the screen, or a damage to the polarizing plate may occur. In order to prevent these, in the liquid crystal projector, the air cooling fan 108 is used in order to keep the optical members such as the polarizer 103, which is a polarizing plate, the analyzer 105, and the liquid crystal panel 104, below a certain temperature.
Is used.

[0008]

By the way, the air-cooling fan 108 includes the polarizer 103, which is a polarizing plate, and the analyzer 10.
5. While the liquid crystal panel 104 and the like can be cooled by a simple mechanism, a large amount of air must be supplied in order to remove a large amount of heat from the liquid crystal projector. In particular, as described above, during black level display, all light that has passed through the liquid crystal panel 104 is absorbed by the analyzer 105 and becomes heat. Therefore, it is necessary to cool the analyzer 105 and the like by continuing to send the air volume of the air cooling fan 108, which is based on the black level display when the maximum amount of heat is absorbed by the analyzer 105. However, if such a large-capacity wind is continuously sent by the air-cooling fan 108, there is a problem that the noise due to the wind noise of the fan, the rotation noise of the motor, and the like increase, and the power consumption increases.

There is also a liquid crystal projector in which a temperature sensor is attached to the analyzer 105 and the air volume of the air cooling fan 108 is controlled according to the measured temperature. However, in the case of this method, since the temperature sensor needs to be mounted near the peripheral portion of the analyzer 105 so as not to block the passage of light, the temperature of the part that is actually the highest temperature in the analyzer 105 is measured. However, it was difficult to accurately cool the analyzer 105.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical modulator and an image projection apparatus that can realize an appropriate and reliable cooling function according to a heat generation state, and cooling them. To provide a method.

[0011]

An optical modulator according to the present invention is provided with a light source, an optical modulator for modulating light emitted from the light source based on a modulation signal, and light emitted from the optical modulator. An optical member, a cooling unit that cools at least the optical unit, and a cooling control unit that controls the cooling unit based on a modulation signal are provided.

Here, the light modulation means all processes for changing various physical quantities related to light, such as the polarization direction of light, the intensity of light, the wavelength of light, the traveling direction of light, and the like. The cooling means means all means capable of cooling an object regardless of mechanical means, electrical means, physical means, chemical means, and a combination thereof. Also,
The optical member means all things having a property of converting a part or all of energy of incident light into heat energy. Hereinafter, the terms have the same meaning in this specification.

An image projection apparatus according to the present invention includes a light source, a light modulator for modulating light emitted from the light source based on an image signal, an optical member on which light emitted from the light modulator is incident, and a light modulator. A projection lens that projects an image formed by the involvement of elements on a screen, a cooling unit that cools at least the optical member, and a cooling control unit that controls the cooling unit according to the brightness level of the image signal. is there.

A method of cooling an optical modulator according to the present invention comprises an optical modulator for modulating light emitted from a light source based on a modulation signal, an optical member on which light emitted from the optical modulator is incident, and at least an optical element. A method for cooling an optical modulator, comprising: a cooling means for cooling a member, comprising: a step of obtaining a predetermined signal level from a modulation signal; and a step of controlling the cooling means based on the obtained signal level. It is the one.

The cooling method of the image projection apparatus according to the present invention is
A light modulation element that modulates the light emitted from a light source based on an image signal, an optical member on which the light emitted from the light modulation element enters, and a projection that projects an image formed by the involvement of the light modulation element onto a screen. A method for cooling an image projection apparatus comprising a lens and a cooling means for cooling at least an optical member, the step of obtaining a luminance level of an image from an image signal, and controlling the cooling means based on the obtained luminance level. It includes steps and.

In the light modulating device or the cooling method thereof according to the present invention, the light emitted from the light source and modulated by the light modulating element is incident on the optical member, and part or all of it is converted into heat energy. The light incident on the optical member is modulated according to the modulation signal supplied to the light modulation element, and the amount of heat energy generated in the optical member depends on the content of the modulation. The cooling means is controlled by the cooling control means so as to change the degree of cooling the optical member based on the degree of modulation received by the light incident on the optical member or the intensity of the light incident on the optical member. .

In the image projection apparatus or the cooling method thereof according to the present invention, the light emitted from the light source and modulated by the light modulation element is projected onto the screen by the projection lens through the optical member or as it is, and is displayed as an image. To be done. All or part of the light emitted from the light modulation element is incident on the optical member. In the optical member, a part or all of the incident light is converted into heat energy. The light incident on the optical member is modulated according to the image signal supplied to the light modulation element, and the amount of heat energy generated in the optical member depends on the content of the modulation. The cooling means is controlled by the cooling control means so as to change the degree of cooling the optical member based on the degree of modulation received by the light incident on the optical member or the intensity of the light incident on the optical member. .

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
2 shows an overall configuration of the image projection apparatus according to the embodiment. This device is a so-called single-plate type color liquid crystal projector that projects and displays a color image using one liquid crystal panel. This liquid crystal projector includes a light source 11 such as a discharge lamp that emits unpolarized light, and a light source 11
The illumination optical system 12 is composed of a condenser lens or the like for condensing the light from the liquid crystal panel 14 which will be described later, and the absorption type polarization plate that limits the light incident on the liquid crystal panel 14 to only linearly polarized light. And a polarizer 13.

This liquid crystal projector also has a liquid crystal panel 14 as a light modulation element for performing modulation by rotating the polarization direction of incident light based on a given image signal 20.
Of the light emitted from the liquid crystal panel 14, an analyzer 15 formed of an absorption type polarizing plate that absorbs a certain linearly polarized light and transmits a linearly polarized light component perpendicular to the linearly polarized light, and the light transmitted through the analyzer 15 will be described later. And a projection lens 16 for projecting on a screen 17. The above optical elements are all optical axes Ax
Are coaxially arranged along the.

This liquid crystal projector further includes an air cooling fan 18 for cooling the analyzer 15, the polarizer 13 and the liquid crystal panel 14 which are optical members, and an air cooling fan control circuit 19 for controlling the air cooling fan 18. I have it. The polarizer 13 and the analyzer 15 are composed of, for example, a polarizing film.

Although not shown, the liquid crystal panel 14 is
It is a transmissive type in which a nematic liquid crystal is enclosed in a twisted state between two substrates. Polarizer 13 and analyzer 15
Are arranged so that the transmission axes of light are orthogonal to each other, that is, in a so-called orthogonal Nicol relationship. The transmission axis of the polarizer 13 is set to be in the same direction as the alignment direction of liquid crystal molecules at the interface between the incident side substrate of the liquid crystal panel 14 and the liquid crystal layer. On the other hand, the transmission axis of the analyzer 15 is set to be in the same direction as the alignment direction of the liquid crystal molecules at the interface between the substrate on the emission side of the liquid crystal panel 14 and the liquid crystal layer.

The liquid crystal panel 14 has a large number of liquid crystal cells (not shown) arranged in a matrix, and a black matrix portion (not shown) as a wiring region for supplying an image signal to each liquid crystal cell. It consists of One liquid crystal cell is composed of three cells, an R cell for red color, a G cell for green color, and a B cell for blue color. Each cell is provided with an electrode (not shown) for applying an image signal. Has been. A pixel signal for each color that constitutes an image signal is supplied to each of these electrodes, and light modulation (change in polarization direction) based on the pixel signal is performed for each cell.

As described above, the liquid crystal projector according to the present embodiment is characterized by the air cooling fan control circuit 19 as a cooling control means for controlling the air cooling fan 18 according to the content of the display image on the liquid crystal panel 14. I have it. The air-cooling fan control circuit 19 includes a liquid crystal panel 1
The same image signal 20 that is input to 4 is supplied simultaneously in parallel. Air cooling fan control circuit 19
Controls the control voltage Vf supplied to the air cooling fan 18 based on the image signal 20.
It has a function of controlling the number of revolutions of 8 and adjusting the air volume.

Next, the operation and action of the liquid crystal projector thus constructed will be described. First, the overall operation will be described.

Irradiation light L0 emitted from the light source 11 enters the polarizer 13. Of the irradiation light L0 from the light source 11, the polarizer 13 transmits only the linearly polarized light component in the same vibration direction as the transmission axis, while absorbing and not transmitting the light component in the vibration direction orthogonal to the transmission axis. The light transmitted through the polarizer 13 enters the liquid crystal panel 14.

The operation of the liquid crystal panel 14 will be described in more detail. In the state where no voltage is applied to the liquid crystal layer of the liquid crystal panel 14, the twisting of the liquid crystal molecules causes optical rotatory power, and the vibration direction of light is 90 degrees along the twisting of the liquid crystal molecules.
° rotate. As a result, the light emitted from the liquid crystal panel 14 has its vibration direction in the same direction as the transmission axis of the analyzer 15, and passes through the analyzer 15. The light transmitted through the analyzer 15 is projected onto the screen 17 via the projection lens 16. On the other hand, when a voltage is applied to the liquid crystal layer of the liquid crystal panel 14, the alignment state of the liquid crystal molecules is changed so that the long axes of the liquid crystal molecules are in the same direction as the optical axis, and the optical activity is lost. Therefore, the linearly polarized light component that has passed through the polarizer 13 passes through the liquid crystal panel 14 while maintaining its vibration direction. The light transmitted through the liquid crystal panel 14 while maintaining the vibration direction in this way is absorbed by the analyzer 15 and does not pass through. Such a phenomenon occurs in each liquid crystal cell.

Next, the operations of the air-cooling fan control circuit 19 and the air-cooling fan 18 will be described in detail with reference to FIGS.

In order to realize a high brightness liquid crystal projector, a light source 11 having a particularly large light output is used. Therefore, the polarizer 1 which is an absorption type polarizing plate
Light of large energy is input to 3 and the analyzer 15, and the temperature rises due to selective absorption of light. The air cooling fan 18 is controlled by the air cooling fan control circuit 19,
An appropriate amount of air is sent to the optical members such as the polarizer 13, the analyzer 15, and the liquid crystal panel 14 which are polarizing plates, and functions to suppress the temperature rise of these optical members.

The amount of light absorbed by the analyzer 15 depends on the brightness level of the entire screen of the image signal at a certain moment. When the entire screen is black (when the black level is displayed), that is, when the brightness level is the lowest, the maximum amount of light flux (Lmax) is absorbed by the analyzer 15. Further, when the entire screen is white (when the white level is displayed), that is, when the brightness level is the highest, the minimum amount of light flux (Lmin) is absorbed by the analyzer 15. Let L be the luminous flux absorbed by the analyzer 15 at each moment according to the brightness level of the entire screen of the image signal.
n ≦ L ≦ Lmax.

FIG. 2 shows an example of the relationship between the amount of absorbed light in the analyzer 15 of the liquid crystal projector and the content of the image signal. The vertical axis in the figure represents the absorbed light amount and the horizontal axis represents time. As shown in this figure, when the whitish screen continues (when an image signal with a higher brightness level is input), the light flux L absorbed by the analyzer 15 is from time t1 to t2.
become that way. In this case, since the amount of light absorbed by the analyzer 15 is small and the heat generation is small, the air-cooling fan control circuit 19
Drives the air cooling fan 18 with a lower control voltage Vf, for example. On the other hand, when the blackish screen continues (when an image signal having a low luminance level is input), the light flux L absorbed by the analyzer 15 becomes as from time t2 to t3. In this case, since the amount of light absorbed by the analyzer 15 is large and a large amount of heat is generated, the air-cooling fan control circuit 19 uses the air-cooling fan 18 for example.
Is driven with a higher control voltage Vf.

FIG. 3 shows an example of the relationship between the control voltage of the air-cooling fan 18 and the brightness level of the entire screen of the image signal 20. The vertical axis of the figure represents the control voltage Vf of the air-cooling fan 18, and the horizontal axis. Represents the brightness of the entire screen. As shown in this figure, when there are many white parts on the entire screen and the brightness level is high,
That is, in the analyzer 15, when the light absorption is small, the control voltage Vf supplied to the air cooling fan 18 is lowered. In addition, when there are many black parts on the entire screen and the brightness level is low, that is, when there is a lot of light absorption, the air cooling fan 1
The control voltage Vf supplied to 8 is increased. Then, when the brightness level is the highest, that is, when the light flux absorbed by the analyzer 15 is the minimum amount Lmin, the control voltage Vf of the air-cooling fan 18 is set to the minimum Vmin, and when the brightness level is the lowest,
That is, the light flux absorbed by the analyzer 15 has the maximum amount Lmax.
, The control voltage Vf of the air-cooling fan 18 is set to the maximum Vm.
Let it be ax. In this way, the control voltage Vf supplied to the air cooling fan 18 is controlled so that Vmax ≧ Vf ≧ Vmin.

As described above, since the degree of absorption of the light flux L in the analyzer 15 corresponds to the brightness of the entire screen,
The air-cooling fan control circuit 19 calculates the total brightness of the entire screen (total value in the image) by adding the brightness levels of the image signals for all the pixels of the screen, and the control given to the air-cooling fan 18 based on the calculation result. The voltage Vf is determined. However, instead of the total brightness of the entire screen, the average brightness in the image (in-image average value) may be calculated, and the air volume of the air-cooling fan 18 may be controlled based on the calculation result.

Next, the control process of the air cooling fan 18 by the air cooling fan control circuit 19 will be specifically described with reference to FIG.

FIG. 4 shows a flow of control processing of the air-cooling fan control circuit 19. In this example, the brightness levels of image signals for a certain fixed time are cumulatively added, and the control voltage Vf of the air-cooling fan 18 is determined based on the addition result. Specifically, the following control is performed.

The air-cooling fan control circuit 19 first resets the counter Li for integrating the image signal brightness level and the counter Ti for integrating time, and clears the respective values (step S101). Next, the brightness level of the current image signal is added to the counter Li (step S102). It is determined whether or not the integration processing of the brightness level of the image signal is repeatedly performed for a certain integration time Tt while increasing the value of the counter Ti (step S103). Thus, the counter Ti has the integration time T
It is used to manage t.

In this way, after the luminance level of the image signal is integrated for a certain integration time Tt, the air cooling fan control circuit 1
Reference numeral 9 is a control voltage V of the air-cooling fan 18 based on the value of the counter Li, that is, the integrated value of the brightness level of the image signal.
f is determined (step S105), the rotation speed of the air cooling fan 18 is controlled, and the air volume is adjusted (step S106).
Then, the counters Li and Ti are reset again, the luminance levels of the image signals are integrated, and the air-cooling fan 18 is controlled based on the integrated value.
The process of determining the control voltage Vf of the air-cooling fan 18 based on the integrated value of the brightness level of the image signal is performed by creating a table with the contents shown in FIG. 3 in advance and referring to it. Alternatively, it may be performed using a predetermined arithmetic expression.

As described above, according to the present embodiment, by controlling the air cooling fan 18 based on the brightness level of the image signal, when the light absorption in the analyzer 15 is small, the air cooling fan 18 is rotated at low speed. The air-cooling fan 18 is operated at a high rotation speed when the light absorption in the analyzer 15 is large. Therefore, the air cooling fan 18
It is possible to cool the analyzer 15 to a necessary and sufficient level without constantly continuing to rotate at high speed. As a result, it is possible to avoid the constant generation of large fan wind noise and motor drive noise, and it is possible to reduce the noise of the liquid crystal projector as a whole. Further, since the air-cooling fan 18 only needs to supply a necessary amount of air, power consumption can be reduced. Therefore, it is possible to realize a liquid crystal projector that is highly quiet and consumes less power.

Moreover, since the amount of air blown by the air-cooling fan 18 is determined based on the brightness level of the entire screen, which reflects the degree of absorption of the light flux L in the analyzer 15, the light absorption in the analyzer 15 is large. Air cooling fan 18
When the required cooling amount due to is large, it is possible to reliably detect this state and rotate the air-cooling fan 18 at high speed to sufficiently cool the analyzer 15. As a result, deterioration of functions of the polarizer 13, the analyzer 15, the liquid crystal panel 14 and the like due to an increase in temperature, for example, deterioration of brightness, deterioration of contrast, uneven brightness on the screen, damage to the polarizing plate, etc. It can be effectively prevented.

In the present embodiment, the image projection apparatus has been described as a single-plate type color liquid crystal projector, but it goes without saying that it can be applied to a monochrome type liquid crystal projector.

<Modification> FIG. 5 shows a simpler control method than the case of FIG. In this control method, the brightness level (for example, the total value in the image) of the image signal of the entire screen is sampled at every constant time Ts, and the control voltage Vf of the air-cooling fan 18 is determined. More specifically, the air-cooling fan control circuit 19 first
The control voltage Vf of the air-cooling fan 18 is determined from the brightness level of the current image signal (step S201). The control voltage Vf controls the rotation speed of the air-cooling fan 18 to adjust the air volume (step S202). Then, after the elapse of a certain sampling time Ts (step S203), the control voltage Vf of the air cooling fan 18 is determined again from the brightness level of the image signal, and the air cooling fan 18 is controlled. Hereinafter, such processing is repeated.

As described above, the sampling method shown in FIG. 5 is easier to control than the method shown in FIG. 4, and the circuit configuration of the air-cooling fan control circuit 19 can be simplified. On the other hand, the method based on the integration shown in FIG. 4 is more reliable than the method shown in FIG. 5 because the control can follow this even when the brightness level of the image signal changes greatly in a short time. The photon 15 can be cooled. However, also in the method of FIG. 5, it is possible to increase the reliability of control by shortening the sampling time.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The embodiment will be described.

FIG. 6 shows the overall structure of an image projection apparatus according to the second embodiment of the present invention. This device
This is a so-called three-panel type color liquid crystal projector using three liquid crystal panels. In FIG. 6, the first
The same parts as those in the embodiment (FIG. 1) are designated by the same reference numerals, and the description thereof will be appropriately omitted.

The liquid crystal projector of this embodiment has a light source 11 for emitting red, blue, and green (hereinafter, referred to as RGB) color lights.
R, 11G, 11B, and illumination optical systems 12R, 12G, 12B provided corresponding to the respective light sources,
3 provided for each of these illumination optical systems
The liquid crystal panels 14R, 14G, and 14B are provided. Light source 11R, illumination optical system 12R, and liquid crystal panel 1
The 4Rs are coaxially arranged in this order along the optical axis Ax1. The light source 11G, the illumination optical system 12G, and the liquid crystal panel 14G are coaxially arranged in this order along the optical axis Ax2. The light source 11B, the illumination optical system 12B, and the liquid crystal panel 14B are coaxially arranged in this order along the optical axis Ax1.

A polarizer 13R and an analyzer 15R are provided on the light source side and the opposite side of the liquid crystal panel 14R for red light, respectively. A polarizer 13G and an analyzer 15G are provided on the light source side and the opposite side of the liquid crystal panel 14G for green light, respectively. A polarizer 13B and an analyzer 15B are provided on the light source side and the opposite side of the liquid crystal panel 14B for blue light, respectively. Here, the liquid crystal panel 14R,
14G and 14B respectively correspond to the "individual image display device" of the present invention, and the analyzers 15R, 15G and 15B
Respectively correspond to specific examples of the "individual optical member" in the present invention.

This liquid crystal projector also has RGB 3
A color synthesizing prism 21 for synthesizing color light and a projection lens 1 for projecting the synthesized light on the screen 17.
6 and. The color synthesizing prism 21 is arranged so that its center is located at the intersection of the optical axis Ax1 and the optical axis Ax2, and the projection lens 16 is arranged on the opposite side of the illumination optical system 12G with the color synthesizing prism 21 as a reference. It is located along Ax2. The three analyzers 15R, 15G and 15B are
Each of the color combining prisms 21 has a substantially cubic shape.
The projection lens 16 is arranged so as to face each of the incident surfaces of, and the projection lens 16 is arranged so as to face the exit surface of the color combining prism 21.

The liquid crystal projector further includes a polarizer 13R, 13G, 13B and an analyzer 15R, 15G, 1 mainly.
5B and the liquid crystal panels 14R, 14G, 14B, an air cooling fan 18, an air cooling fan control circuit 19 for controlling the air cooling fan 18, and an input image signal 2
And an RGB separation circuit 22 for separating 0 into RGB color image signals 20R, 20G, and 20B. The air-cooling fan 18 is installed above or below the color combining prism 21. The RGB separation circuit 22 separates the separated image signals 20 of the respective colors.
R, 20G and 20B are respectively connected to liquid crystal panels 14R and
It is supplied to 14G and 14B. The image signal 20 input to the RGB decomposition circuit 22 is also supplied to the air-cooling fan control circuit 19.

Next, the operation and action of the liquid crystal projector thus constructed will be described.

The light from the light sources 11R, 11G and 11B is
Each of the liquid crystal panels 14R, 14G and 14B is linearly polarized in a predetermined direction via the illumination optical systems 12R, 12G and 12B and the polarizers 13R, 13G and 13B.
Is incident on. The respective color lights incident on the respective liquid crystal panels 14R, 14G, 14B are respectively subjected to optical modulation based on the respective color signals decomposed from the image signal 20, and are emitted. The emitted lights of the respective colors from the liquid crystal panel panels 14R, 14G and 14B are selectively transmitted through the analyzers 15R, 15G and 15B and are combined by the color combining prism 21. The combined light is projected onto the screen 17 by the projection lens 16 and an image is displayed.

The air-cooling fan control circuit 19 controls the image signal 20.
The air-cooling fan 18 is controlled based on the brightness level of. Specifically, the air-cooling fan control circuit 19 controls the air volume by changing the control voltage Vf of the air-cooling fan 18 based on the sum of the brightness levels of the image signals of RGB colors in the entire screen, and the analyzers 15R, 15G, 15B, liquid crystal panel 14
R, 14G, 14B, and polarizers 13R, 13G, 1
The optical member such as 3B is cooled. Thereby, high quietness and low power consumption can be realized as in the case of the first embodiment.

By the way, in general, the polarizing plates (polarizer 13B, analyzer 15B) provided for blue light (B) are deteriorated even when kept at the same temperature as compared with the polarizing plates for other color lights. early. This is because the wavelength of light is short, the energy of photons is high, and ultraviolet rays are included. Therefore, of the analyzers 15R, 15G and 15B,
It is preferable to allocate a larger air volume than the other two colors to the light absorption generated in the analyzer 15B for blue light. More generally, for the same brightness level in the image signal for each color light of RGB,
The cooling air volumes different from each other are set.

For example, in a certain image signal S1, the light absorption at the analyzer 15R is 50% and the light absorption at the analyzers 15G and 15B is 0%, and the air cooling fan 18 at this time is assumed.
Let VR be the voltage for controlling. In addition, in another image signal S2, the light absorption in the analyzers 15R and 15G is 0.
%, And the light absorption by the analyzer 15B is 50%, and the voltage for controlling the air-cooling fan at this time is VB. The absolute amount of light absorption in the analyzer 15R for the image signal S1 and the absolute amount of light absorption in the analyzer 15B for the image signal S2 are equal to each other. In this case, air cooling fan 1
It is preferable to set the voltage for controlling 8 so that VB> VR. That is, the analyzers 15R, 1 for each color light
The control voltage Vf that determines the air volume of the air-cooling fan 18 is set in consideration of the light resistance and heat resistance of the 5G and 15B. By doing so, the analyzer 15R for each color light,
The balance of life of 15G and 15B is maintained, and as a result,
The life of the entire device will be extended.

Thus, the analyzers 15R, 15G, 15
The method for providing a difference in the cooling air flow rate for each of B is
For example, it is realized as follows.

Now, let the brightness levels of the RGB image signals be LR, LG, and LB, respectively, and the three analyzers 15R, 1
The coefficients for allocating the air volume to 5G and 15B are kR, kG, and kB, respectively. Then, by performing weighted addition as in the following expression (1), the brightness level L
To decide.

[0056] L = kR × LR + kG × LG + kB × LB (1)

Next, the brightness level L determined by the equation (1)
Is used to determine the control voltage Vf of the air-cooling fan 18.
Here, for example, when it is desired to cool the analyzer 15B for blue light particularly intensively, the value of kB may be set larger than the values of kR and kG.

As described above, according to the present embodiment, one air cooling fan 18 is provided at a position where all three analyzers 15R, 15G, and 15B can be cooled, and is included in the input image signal 20. Since the air volume of the air-cooling fan 18 is controlled based on the sum of the brightness levels of the image signals of all colors, it is possible to efficiently cool the optical members of the three-plate type liquid crystal projector collectively by one cooling fan. You can

In particular, in the case where the brightness levels of the image signals for the respective colors of RGB are set to have different cooling air flow levels, the analyzers 15R for the respective color lights,
The life balance of 15G and 15B is maintained, and the durability of the entire device is improved.

<Modification> In the present embodiment, only one air cooling fan 18 is provided for the three analyzers 15R, 15G, 15B, but the present invention is not limited to this.
For example, as shown in FIG. 7, the analyzers 15R, 15G, 1
Air cooling fans 18R, 18G, 1 for each of 5B
8B may be installed, and the air-cooling fan control circuit 19 may individually control these air-cooling fans 18R, 18G, and 18B. Here, the air cooling fans 18R, 18
G and 18B respectively correspond to a specific example of "individual cooling means" in the present invention.

In this modification, the RGB color image signals 20R, 20 separated by the RGB separation circuit 22 and output.
G and 20B are liquid crystal panels 14R, 14G, and
Not only 14B but also the air-cooling fan control circuit 19 is supplied. The air-cooling fan control circuit 19 generates control voltages VfR, VfG, VfB based on the input color image signals 20R, 20G, 20B, and supplies these to the air-cooling fans 18R, 18G, 18B, respectively. The air-cooling fans 18R, 18G, 18B are connected to the analyzers 15R, 1
Control voltage Vf R, V for each of 5G and 15B
The air volume corresponding to each of f G and Vf B is sent to cool.

As described above, according to this modification, the air-cooling fan control circuit 19 obtains the brightness level of the entire screen for each of the RGB color image signals output from the RGB decomposition circuit 22, and the obtained brightness levels are obtained. Depending on the brightness level,
Since the control voltages Vf R, Vf G, and Vf B of the corresponding air-cooling fans 18R, 18G, and 18B are set, the light absorption amount (and thus the heat generation amount) in each of the analyzers 15R, 15G, and 15B can be accurately measured. The analyzers 15R, 15G, and 15B can be individually cooled with a cooling capacity corresponding to.

Also in this modification, as in the case of the above-described second embodiment, the cooling air flow levels corresponding to the brightness levels of the image signals for the RGB colors are made different. It is preferable that the balance of the life of the analyzers 15R, 15G, and 15B for each color light is maintained, and the durability of the entire apparatus is improved.

[Third Embodiment] Next, the third embodiment of the present invention will be described.
The embodiment will be described.

FIG. 8 shows the overall structure of the liquid crystal projector according to the third embodiment. In this figure,
The same components as those shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted as appropriate. This liquid crystal projector is a color liquid crystal projector that uses three liquid crystal panels 14R, 14G, and 14B, as in the second embodiment. In the above-described second embodiment, the light sources 11R, 11G, and 11B that emit the RGB color lights are used, but in the present embodiment, one white light source 11W is used as the light source. Then, the white light emitted from the white light source 11W is RG by the color separation mirrors 31R and 31G.
Each color light of B is decomposed, and each color light is guided to the color combining prism 21 by the total reflection mirrors 32, 33, and 34. Other configurations and operations are similar to those of the second embodiment.

According to the present embodiment, unlike the second embodiment, only one light source is required, which is advantageous in that the power consumption can be reduced and the installation space of the light source can be reduced. The advantage of cooling the optical member is the second.
This is the same as the case of the embodiment.

Also in the present embodiment, the second
Similarly to the modification of the embodiment, the analyzer 15R,
Air cooling fans 18R, 15G, 15B
Of course, 18G and 18B can be installed and cooling control can be individually performed.

[Fourth Embodiment] Next, the fourth embodiment of the present invention will be described.
The embodiment will be described.

FIG. 9 shows the overall structure of the image projection apparatus according to the fourth embodiment. This image projection apparatus uses a DMD (Digital Micromirror Decoder) as a light modulation element.
vice: A projector using a device (trademark of Texas Instruments, Inc. in the United States). In the following description, the same parts as those in the first embodiment will be designated by the same reference numerals, and the description thereof will not be repeated.

This image projector includes a light source 11, an illumination optical system 12, a DMD element 41, and a projection lens 16.
A light absorbing member 42, an air cooling fan 18, and an air cooling fan control circuit 19. Light source 11, illumination optical system 1
2 and the DMD element 41 are arranged in this order along the optical axis Ax3. The projection lens 16 is arranged along an optical axis Ax4 extending in a direction different from the optical axis Ax3. The light absorbing member 42 is arranged in a direction different from both the optical axis Ax3 and the optical axis Ax4.

The light absorbing member 42 is for absorbing unnecessary light reflected by the DMD element 41, and is constituted by using a heat sink, for example. An air cooling fan 18 controlled by an air cooling fan control circuit 19 is arranged near the light absorbing member 42. Air cooling fan control circuit 1
9 is an air-cooling fan 1 based on the brightness level of the image signal 20.
The cooling air volume of 8 is controlled.

The DMD element 41 is, for example, 14 μm × 14.
A minute movable mirror (not shown) of μm is arranged so as to correspond to each pixel so as to be spread over several hundred thousand to one million sheets or more, and the direction angle of each movable mirror is set in accordance with an image signal. It is an element for projecting and displaying an image by changing the light reflection direction.

The operation and action of this projector device are as follows.

The light from the light source 11 enters the DMDMS 41 through the illumination optical system 12. The DMD element 41 performs optical modulation by changing the angle of each movable mirror and changing the traveling direction of the reflected light based on the image signal 20. Specifically, for example, in the case of white level display, the angle of the variable mirror is changed so that all the reflected light is directed to the screen 17. On the other hand, in the case of black level display, the angle of the variable mirror is changed so that all the reflected light goes toward the light absorbing member 42. In the case of black level display, light is absorbed by the light absorbing portion 42 and becomes heat. Air cooling fan 18
Serves to cool the inside of the device by removing the heat generated in the light absorbing section 42.

The amount of light absorbed by the light absorbing section 42 is
The lower the brightness level of the image signal 20, the larger the amount, and the higher the brightness level, the smaller the amount. The air-cooling fan control circuit 19 controls the air volume of the air-cooling fan 18 based on the brightness level of the image signal 20. As a result, it is possible to realize a projector with low noise, high quietness, and low power consumption. Moreover, D
When an MD element is used, unlike a liquid crystal panel that uses polarized light, the MD element can be effectively used without substantially reducing the intensity of incident light, and thus a high-luminance projector can be realized.

Although the present invention has been described with reference to some embodiments, the present invention is not limited to these embodiments and various modifications can be made. For example, in the above-described first to third embodiments, the liquid crystal projector using the transmissive liquid crystal panel has been described, but the present invention is also applicable to the case of using the reflective liquid crystal panel.

Further, in the first to third embodiments, the liquid crystal element has been described as an example of the light modulating element utilizing polarization, but the present invention is not limited to the light modulating element utilizing polarization according to another principle. Can also be applied. For example, it can be applied to a polarization modulation element using an electro-optical effect such as Kerr effect or Pockels effect or a magneto-optical effect such as Zeeman effect or Faraday effect.

In the fourth embodiment, the DMD element is described as an example of the light modulation element that uses the light deflection (changing the direction of light), but the present invention is not limited to this. The present invention can also be applied to a light modulator. For example, it can be applied to an acousto-optic effect element using ultrasonic waves and an optical deflection element using an electrostrictive effect or a magnetostrictive effect.

Further, in each of the above-mentioned embodiments, the image projection apparatus for enlarging and projecting the spatial image formed by using the liquid crystal panel or the DMD element on the screen by the projection lens has been described, but the present invention is not limited to this. In addition, it can be applied to a system that does not use a projection lens for magnifying projection. For example, the present invention can be applied to a semiconductor exposure apparatus in which a light modulation element such as a liquid crystal element is used to form a reticle, and the reticle is used for exposure.

Further, in each of the above-described embodiments, an example in which the cooling fan 18 is used as the cooling means has been described, but other cooling means such as a Peltier element may be used instead of the cooling fan. Alternatively, a cooling fan and other cooling means can be used together.

Further, in each of the above embodiments, the cooling amount is controlled based on the brightness level of the image signal in the entire screen, but it is based on the brightness level of the image signal in a part of the screen instead of the entire screen. You may make it control by.

[0082]

As described above, the optical modulator according to any one of claims 1 to 11, claim 12
According to the image projection device of claim 1, the cooling method of the light modulation device according to claim 13, or the cooling method of the image projection device according to claim 14, the light modulated by the light modulation element based on the modulation signal. Is cooled by the cooling means, and the cooling control means controls the cooling operation of the cooling means based on the modulation signal, so that the degree of modulation of the light incident on the optical member is reflected. Therefore, it is possible to perform appropriate cooling according to the amount of heat generation.

In particular, according to the optical modulator of the second aspect, the cooling capacity is increased as the amount of light captured by the optical member out of the light emitted from the optical modulator based on the modulation signal is larger. Since the cooling means is controlled as described above, it is possible to perform necessary and sufficient cooling without waste. Therefore, it is possible to perform reliable cooling of the optical member while effectively reducing noise generation due to cooling of the cooling unit and power consumption by the cooling unit.

According to the third aspect of the light modulator, the cooling means is controlled based on the average value or the total value in the image of the brightness level of each pixel in the image signal. The entire display state can be reflected in the cooling control.

Further, according to the optical modulator of the present invention, the average value in the image or the total value in the image of the brightness level of the image signal is accumulated over a certain period, and the cooling means is controlled based on the accumulated value. Therefore, even if the content of the image signal fluctuates significantly with time, it is possible to perform the gradual cooling control.

Further, according to the optical modulator of the fifth aspect, the average value in the image or the total value in the image of the brightness level is sampled at regular intervals, and the cooling means is controlled based on the sampled value. Therefore, the control can be simplified.

According to the sixth aspect of the optical modulator, a liquid crystal display element that changes the polarization direction of light according to an image signal is used as the image display element, and the optical member is
Since the analyzer composed of the polarizing plate that absorbs only the linearly polarized light component of the specific polarization direction of the light emitted from the liquid crystal display element is used, the light modulation device configured by combining the liquid crystal display element and the analyzer. In the above, the light modulation can be performed while appropriately cooling the analyzer which generates heat by absorbing light.

According to the seventh aspect of the present invention, there is provided a light modulating device as a digital micromirror device in which a plurality of minute reflecting mirrors whose tilt angles change according to an image signal are arranged as an image display element ( DMD) is used as the optical member, and a light absorbing member that absorbs the light reflected by the digital micromirror device and traveling in the direction not used for image formation is used.
In the light modulation device configured by combining the light absorbing member and the light absorbing member, it is possible to perform the light modulation while appropriately cooling the light absorbing member that generates heat by absorbing light.

According to the ninth aspect of the present invention, there are provided a plurality of individual image display elements arranged corresponding to each of the plurality of color lights and individually driven by the image signals of the respective color lights, and a plurality of individual image display elements. And a plurality of individual optical members arranged so that the light emitted from each of the individual image display elements is incident respectively, and the only cooling that can collectively cool the plurality of individual optical members. Since the means is provided, the plurality of individual optical members can be collectively cooled by one cooling means, which is efficient.
Furthermore, since the cooling capacity of a single cooling means is determined by performing a predetermined calculation with weighting on the brightness level of the image signal for each color light, the brightness level of the image signal for each color light is determined. It is also possible to provide a difference in the corresponding cooling air volume levels. In this case, it is possible to maintain the balance of the lives of the individual optical members for the respective color lights and improve the durability of the entire device.

According to the optical modulator of the tenth aspect, a plurality of individual cooling means are provided corresponding to each of the plurality of individual optical members, and based on the brightness level of the image signal for each color light, Since the cooling capacity of the corresponding individual cooling means is determined, the light absorption amount (and thus the heat generation amount) of each individual optical member can be accurately reflected to individually cool the individual optical member.

According to the eleventh aspect of the light modulation device, the plurality of individual cooling means exert different cooling capacities with respect to the same brightness level in the image signal for each color light. In addition, since the cooling capacity of each individual cooling means is determined, the life of the individual optical members for each color light is balanced, and the durability of the entire apparatus is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a liquid crystal projector according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of the relationship between the content of an image signal and the amount of absorbed light in an analyzer.

FIG. 3 is a diagram showing an example of the relationship between the brightness level of the entire screen in the image signal and the control voltage of the air-cooling fan.

FIG. 4 is a flowchart for explaining the processing of the air-cooling fan control circuit in the method of integrating the brightness level of the image signal.

FIG. 5 is a flow chart for explaining the processing of the air-cooling fan control circuit in the method of sampling the brightness level of the image signal.

FIG. 6 is a configuration diagram showing an overall configuration of a liquid crystal projector according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing an overall configuration of a liquid crystal projector according to a modification of the second embodiment.

FIG. 8 is a configuration diagram showing an overall configuration of a liquid crystal projector according to a third embodiment of the present invention.

FIG. 9 is a configuration diagram showing an overall configuration of a projector according to a fourth embodiment of the invention.

FIG. 10 is a configuration diagram showing an overall configuration of a conventional liquid crystal projector.

FIG. 11 is a diagram for explaining the behavior of light in the peripheral portion of the liquid crystal panel of the liquid crystal projector shown in FIG.

[Explanation of symbols]

11 ... Light source, 12 ... Illumination optical system, 13, 13R, 13
G, 13B ... Polarizer, 14, 14R, 14G, 14B ...
Liquid crystal panel, 15, 15R, 15G, 15B ... Analyzer,
16 ... Projection lens, 17 ... Screen, 18, 18R,
18G, 18B ... Air cooling fan, 19 ... Air cooling fan control circuit, 20 ... Image signal, 20R, 20G, 20B ... Each color image signal, 21 ... Color combining prism, 22 ... RGB separation circuit, 31R, 31G ... Color separation mirror, 32 , 33, 34
... total reflection mirror, 41 ... DMD element, 42 ... light absorbing member.

Claims (14)

[Claims] 1. A light source, a light modulation element that modulates light emitted from the light source based on a modulation signal, an optical member on which light emitted from the light modulation element is incident, and at least the optical member is cooled. An optical modulator comprising: cooling means; and cooling control means for controlling the cooling means based on the modulation signal. 2. The cooling control means, based on the modulation signal, increases the cooling capacity as the amount of light captured by the optical member out of the light emitted from the light modulation element increases. The light modulator according to claim 1, wherein the light modulator controls the means. 3. The light modulation element is an image display element configured by arranging a plurality of element units corresponding to a plurality of pixels forming an image, and the modulation signal is an image signal representing an image. 2. The cooling control means controls the cooling means based on an in-image average value or an in-image total value of the brightness levels of the respective pixels in the image signal.
The optical modulator according to. 4. The cooling control means accumulates an in-image average value or an in-image total value of the brightness levels over a certain period, and controls the cooling means based on the accumulated value. 3. The light modulation device according to item 3. 5. The cooling control means samples the in-image average value or in-image total value of the brightness levels at regular intervals, and controls the cooling means based on the sampled value. Item 3. The light modulator according to item 3. 6. The image display element is a liquid crystal display element that changes the polarization direction of light according to the image signal, and the optical member is a specific polarization direction of light emitted from the liquid crystal display element. The optical modulator according to claim 3, which is an analyzer including a polarizing plate that absorbs only the linearly polarized light component. 7. The digital micromirror device (DM), wherein the image display element is formed by arranging a plurality of minute reflecting mirrors whose tilt angle changes in accordance with the image signal.
D), wherein the optical member is a light absorbing member that absorbs light reflected by the digital micromirror device and traveling in a direction not used for image formation. The optical modulator described in 8. The plurality of individual image displays, wherein the image display element is arranged corresponding to each of the plurality of color lights emitted or generated from the light source and is individually driven by an image signal for each color light. An element is included, The optical member includes a plurality of individual optical members arranged so that the light emitted from each of the plurality of individual image display elements is incident, respectively. The light modulator described. 9. The single cooling unit is provided so as to cool the plurality of individual optical members at a time, and the cooling control unit sets a predetermined value with weighting to a brightness level of an image signal for each color light. 9. The optical modulator according to claim 8, wherein the cooling capacity of the cooling unit is determined by performing the calculation of. 10. The cooling means includes a plurality of individual cooling means provided corresponding to each of the plurality of individual optical members, and the cooling control means is based on a brightness level of an image signal for each color light. 9. The light modulation device according to claim 8, wherein the cooling capacity of the corresponding individual cooling means is determined. 11. The cooling control unit controls the individual cooling units so that the plurality of individual cooling units exhibit different cooling capacities with respect to the same luminance level in the image signal for each color light. The light modulation device according to claim 10, wherein a cooling capacity is determined. 12. A device for projecting and displaying an image on a screen, comprising: a light source, a light modulation element that modulates light emitted from the light source based on an image signal, and the light is emitted from the light modulation element. An optical member on which light is incident, a projection lens that projects an image formed by the involvement of the light modulation element on the screen, a cooling unit that cools at least the optical member, and a brightness level of the image signal according to the brightness level. An image projection apparatus comprising: a cooling control unit that controls the cooling unit. 13. A light modulation element for modulating light emitted from a light source based on a modulation signal, an optical member on which light emitted from the light modulation element is incident, and a cooling means for cooling at least the optical member. A method for cooling an optical modulation device, comprising: a step of obtaining a predetermined signal level from the modulated signal; and a step of controlling the cooling means based on the obtained signal level. Modulator cooling method. 14. A light modulation element that modulates light emitted from a light source based on an image signal, an optical member on which light emitted from the light modulation element is incident, and an image formed by the involvement of the light modulation element. A projection lens for projecting on a screen and a cooling means for cooling at least the optical member, wherein a step of obtaining a brightness level of an image from the image signal, A step of controlling the cooling means based on a brightness level.