JP2004138986A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector which improves the peak luminance of image light and realizes a high contrast ratio. <P>SOLUTION: The projector 1 is constituted to have an illumination optical system 10 for emitting white light, a color switching optical system 20 for dividing the white light emitted from the optical system 10 to color light in a time division manner, a DMD (Digital Micromirror Device (R)) 30 for modulating respective color lights according to image signals, a projection optical system 40 for projecting the luminous fluxes modulated by the DMD, a photosynthesis optical system 50 for making the luminous fluxes not incident on the optical system 40 again on the DMD 30, and a system controller 60 for controlling the operation of the projector 1. Among the luminous fluxes emitted by the DMD 30, the luminous fluxes not incident on the optical system 40 are emitted as the luminous fluxes of a uniform illuminance distribution by the optical system 50, are again guided onto the optical axis of illumination and are made incident on the DMD 30. Accordingly, the peak luminance of the projected images is improved and a high contrast ratio can be achieved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projector that projects and displays an image. In particular, it relates to a projector using a DMD.
[0002]
[Background Art]
2. Related Art There is known a projector that modulates a light beam emitted from a light source using an electro-optical device and enlarges and projects the modulated light beam on a screen using a projection lens.
As a light modulation element constituting the electro-optical device, a DMD (digital micro-mirror) as a reflection-type light modulation element that controls the incident angle of a micromirror to light-modulate a light beam emitted from a light source according to image information. Mirror device: a trademark of TI) is known.
The DMD modulates a light beam from a light source in accordance with image data, and emits the modulated light as image light representing an image. Each pixel arranged two-dimensionally includes a minute mirror, For each pixel, the tilt of the micromirror is controlled by an electrostatic field effect of a memory element disposed immediately below the pixel, and an on / off state is created by changing a reflection angle of reflected light, and the light is reflected in a predetermined direction. Light enters a projection lens and is projected as image light.
Here, when the pixel is off, the light beam reflected by the DMD does not enter the projection lens, is not projected as image light, and is guided to a predetermined place inside the device. I have.
By switching between the on / off state and the two states with such a configuration, the light beam from the light source can be deflected, and optical switching with a good S / N ratio can be performed.
[0003]
[Problems to be solved by the invention]
However, in the above-described configuration, the light beam reflected by the DMD when the pixel is off, that is, the light beam that is not introduced into the projection lens is guided to a predetermined place inside the device, and is emitted from the light source. Of the total luminous flux, the light is disposed as surplus light. Therefore, due to the presence of such extra light, the total amount of light of the projected image projected through the projection lens is greatly reduced with respect to the total amount of light emitted from the light source. There is a problem that the middle peak luminance is insufficient.
Further, when the pixel is off, the light reflected by the DMD does not enter the projection lens as image light, but is guided to a predetermined place inside the device, so that the guided light is reflected inside the device. However, there is a problem that the contrast ratio of a projected image which is captured by the projection lens as stray light and projected on the screen is reduced.
[0004]
An object of the present invention is to provide a projector that improves the peak luminance of image light and realizes a high contrast ratio.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, a projector according to the present invention includes a reflection type light modulation element that controls an incident angle of a micromirror to light-modulate a light beam emitted from a light source in accordance with image information. A projector that magnifies and projects through the projection optical system, the light flux modulated by the reflection-type light modulation element and not incident on the projection optical system is again combined with the light flux emitted from the light source, and the reflection type A light combining path for introducing the light into the light modulation element is provided.
[0006]
According to such an embodiment of the present invention, of the light beams emitted by the reflection-type light modulation element, the light beam that does not enter the projection optical system is provided with a light combining path that causes the light beam to enter the reflection-type light modulation element again. Since a light beam that does not enter the projection optical system, that is, surplus light can be supplied again to the reflection type light modulation element through the photosynthesis path, for example, a white portion is displayed during non-display (black display) in the projection image. In this case, the brightness of the white portion is improved, and the contrast of black and white can be increased.
In addition, the size of the micromirror of the light modulation device is reduced in accordance with high definition, that is, even if the pixel is reduced, the total amount of light incident on the micromirror can be increased, so that sufficient peak luminance is provided. A high contrast ratio can be realized.
Further, since the total amount of light incident on the micromirror can be increased, the amount of light of the projected image increases. Therefore, a sufficient distance can be provided between the projection screen and the projection optical system, and an image having a sufficiently high contrast ratio can be enjoyed even if the projected image is enlarged to correspond to a large-screen display.
Further, by providing the light combining path, when the light flux emitted by the light modulation device and not incident on the projection optical system is guided to a predetermined position in the device, it is reflected on a member in the device and reflected on the projection optical system. Since it is prevented from being captured, it is possible to prevent a decrease in the contrast ratio of the projected image due to stray light, and to maintain a stable projected image.
[0007]
A second light modulation element that is disposed in the light combining path and that switches a light flux that does not enter the projection optical system to the reflection-type light modulation element in synchronization with the image information, and that switches between blocking and interception. Is preferred.
Here, as the second light modulation element, a liquid crystal shutter or a reflection optical element capable of controlling the attitude in a light combining path can be adopted.
When the projected image is not displayed (black display), the light beam emitted from the light source enters the photosynthesis path via the reflection type light modulation element, and the light passing through the photosynthesis path is again emitted. The light enters the reflection type light modulation element. By repeating such a cycle, the light amount of the light beam incident on the reflection-type light modulation element increases, and the light amount of the non-display image may increase.
Here, by providing the second light modulating element in the light combining path, in the non-display state of the projected image, the light beam entering the reflective light modulating element is blocked by the second light modulating element, so that the non-display image An increase in the amount of light can be prevented.
[0008]
Preferably, an optical integrator is provided in the light combining path, and introduces a light beam not incident on the projection optical system into a light beam having a uniform illuminance distribution onto the reflection type light modulation element.
Here, as the light beam splitting optical element used in the optical integrator, a lens array in which several lenses are arranged in rows and columns, a rod integrator using multiple reflection by total internal reflection, and the like can be adopted.
In the light beam that is emitted from the light source and is reflected by the reflection type light modulation element, the image light that enters the projection optical system and is emitted as an image and the light beam that enters the light combining path are in an inverted state. . When passing through the photosynthetic path and re-entering the reflection-type light modulation element, the amount of image light increases even if the light flux that is inverted with respect to the image light enters the reflection-type light modulation element. I will not.
Here, if the optical integrator having the light beam splitting optical element for splitting the light beam into a plurality of partial light beams is provided in the photosynthetic path, the light beam in an inverted state with respect to the image light is converted by the light beam splitting optical element. After being divided into partial light beams, the light beams are superimposed and emitted as a light beam having a uniform illuminance distribution. By re-entering this light beam into the reflection type light modulation element, the amount of image light is increased, and high contrast is achieved. Ratio can be realized.
[0009]
Further, the image information is configured to input an image signal corresponding to the color light to be modulated to the reflective optical element in a time division manner, and the reflective light element is provided between the light source and the reflective optical element. It is preferable that a filter switching unit that switches a color filter in synchronization with an image signal input to the modulation element is provided.
In such a configuration, the light flux from the light source is switched to red, green, and blue in time using a color filter in synchronization with the image signal input to the reflection-type light modulation element, so that one reflection Colorization of the projected image can be realized by the shaped light modulation element.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[1] Structure of projector
FIG. 1 is a diagram schematically illustrating the structure of the projector according to the first embodiment. The projector 1 includes an illumination optical system 10 that emits white light, a color switching optical system 20 that switches white light emitted from the illumination optical system 10 to red, green, and blue light in a time-division manner, according to an image signal. DMD 30 that modulates each color light, a projection optical system 40 that projects a light beam modulated by the DMD 30, a light combining optical system 50 that causes a light beam that does not enter the projection optical system 40 to enter the DMD 30 again, and the operation of the projector 1. And a device control unit 60 for performing control.
[0011]
The illumination optical system 10 is an optical system for illuminating the image forming area of the DMD 30 almost uniformly, and includes a light source device 11, a first lens array 12, a second lens array 13 including a UV filter, and a polarization converter. And an optical element 14.
The light source device 11 includes a light source lamp 11A as a radiation light source that emits a radial light beam, and a reflector 11B that reflects the radiation light emitted from the light source lamp 11A. As the light source lamp 11A, a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is often used. A parabolic mirror is used as the reflector 11B. In addition to a parabolic mirror, an elliptical mirror may be used together with a parallelizing lens (concave lens).
The first lens array 12 has a configuration in which small lenses having a substantially rectangular contour when viewed from the illumination optical axis direction are arranged in a matrix. Each small lens divides the light beam emitted from the light source lamp 11A into a plurality of partial light beams. The outline shape of each small lens is set to be substantially similar to the shape of the image forming area of the DMD 30. For example, if the aspect ratio (the ratio between the horizontal and vertical dimensions) of the image forming area of the DMD 30 is 4: 3, the aspect ratio of each small lens is also set to 4: 3.
[0012]
The second lens array 13 has a configuration substantially similar to that of the first lens array 12, and has a configuration in which small lenses are arranged in a matrix. The second lens array 13 has a function of forming an image of each small lens of the first lens array 12 on the DMD 30 together with the superimposing lens 15 arranged on the illumination optical axis.
The polarization conversion optical element 14 is arranged at the subsequent stage of the second lens array 13 and is unitized integrally with the second lens array 13. Such a polarization conversion optical element 14 converts light from the second lens array 13 into one type of polarized light (P-polarized light). Each partial light converted into one kind of polarized light (P-polarized light) by the polarization conversion optical element 14 is finally superimposed on the DMD 30 by the superimposing lens 15. Incidentally, such a polarization conversion optical element 14 is introduced in, for example, Japanese Patent Application Laid-Open No. 8-304739.
[0013]
The color switching optical system 20 is formed in a disk shape, and rotates by rotating a light beam emitted from the illumination optical system 10 into three color lights of R, G, and B, and emitted from the illumination optical system 10. A first condenser lens 22 for condensing the luminous flux near the color wheel 21 and a second condenser lens 23 for converting divergent light transmitted through the color wheel 21 into substantially parallel light.
As shown in FIG. 2 (a front view of the color wheel 21), the color wheel 21 has three transmission-type color filters 21R, 21G, and 21B formed in four fan-shaped regions separated along the rotation direction. Here, the transmission type color filter 21R transmits only red light by transmitting light in the red wavelength region and reflecting or absorbing light in other wavelength regions. Similarly, the transmissive color filters 21G and 21B transmit light in the green and blue wavelength regions, respectively, and transmit or transmit only green or blue light by reflecting or absorbing light in other wavelength regions. As the transmission type color filters 21R, 21G, and 21B, for example, a dielectric multilayer film, a filter plate formed using a paint, or the like can be used. In the four fan-shaped regions, portions other than the transmission type color filters 21R, 21G, and 21B are light transmission regions 21W, and the light beam emitted from the illumination optical system 10 can pass through as it is. With this translucent area 21W, the brightness in the projected image can be increased, and the brightness of the projected image can be secured.
[0014]
The DMD 30 is a reflection-type light modulation element in which a large number of movable micromirrors are integrated on a semiconductor chip by a micromachine technology based on a CMOS wafer process. The movable micromirrors rotate around a diagonal axis and rotate at two predetermined angles ( Take a bistable state inclined to ± θ). A large light deflection angle of 4θ is obtained between these two states, and optical switching with a good S / N ratio can be performed. Of the light beams incident on the DMD 30, the light beam deflected in the + 2θ direction is projected as image light by the projection optical system 40 as shown in FIG. 1, and the light beam deflected in the −2θ direction is again incident on the DMD 30. Light enters the photosynthetic optical system 50.
Specifically, the DMD 30 is formed by microfabrication using a semiconductor process technology, and as shown in FIG. 3, an address electrode / bias bus layer 32, a hinge layer 33, a yoke layer 34, and a mirror layer are formed on a CMOS substrate 31. 35 are sequentially formed by a sputtering method. An organic polymer or the like is filled as a sacrificial layer between the address electrode 32A and the hinge layer 33 / yoke layer 34 and between the hinge layer 33 / yoke layer 34 and the mirror layer 35. Then, the mirror layer 35 and the yoke layer 34 are opened and rotatable.
The address electrode 32A is electrically connected to the lower CMOS substrate 31. When a predetermined bias voltage is applied to the address electrode 32A, electrostatic attraction is generated between the mirror layer 35 and the address electrode 32A, and the yoke layer 34. The mirror layer 35 and the yoke layer 34 rotate against the restoring force of the hinge layer 33. Here, the mirror layer 35 and the yoke layer 34 rotate until the spring tip 36 lands. When the bias voltage applied to the address electrode 32A is 0, the mirror layer 35 is stable at the horizontal position due to the restoring force of the hinge layer 33. Here, a large light deflection angle of 4θ can be obtained by using the state between the state inclined to the left (+ θ) as shown in FIG. 3 and the state inclined to the right (−θ) not shown. it can.
[0015]
The projection optical system 40 enlarges and projects the image light modulated by the DMD 30 onto the screen 41. In order to prevent the projection image from being blurred due to chromatic aberration or the like in each of the R, G, and B color lights, a plurality of projection optical systems (not shown) are provided. The light collecting element is configured as a group lens in which the light collecting elements are arranged along the optical axis direction.
The photosynthesis optical system 50 causes the light beam modulated by the DMD 30 and not incident on the projection optical system 40 to be incident again on the DMD 30. The light beam is guided on the photosynthesis path 50A to become a light beam having a uniform illumination distribution. Is superimposed on the DMD 30 by the superimposing lens 15 disposed on the illumination optical axis.
The device control unit 60 is electrically connected to the color switching optical system 20, the photosynthetic optical system 50, and the DMD 30, and controls each operation.
[0016]
[2] Structure of photosynthetic optical system
The photosynthesis optical system 50 causes the light flux modulated by the DMD 30 and not entering the projection optical system 40 to again enter the DMD 30. The light flux is guided on the photosynthesis path 50A and enters the DMD 30 again.
On the light combining path 50A, an optical integrator 52 that equalizes the illuminance distribution of the light flux that has been modulated by the DMD 30 and has entered the light combining path 50A, and a light flux that has been made uniform by the optical integrator 52 is again introduced into the DMD 30. A liquid crystal shutter 53 as a second light modulating element capable of switching off, a mirror 54 for guiding a light beam passing through the liquid crystal shutter 53 onto an illumination optical axis, a P-polarized light transmitting, and an S-polarized light A polarization beam splitter 51 for reflecting light.
[0017]
The optical integrator 52 includes a third condenser lens 52A that condenses the light that has entered the photosynthesis path 50A via the DMD 30, and a translucent light that uniforms the illuminance distribution of the light flux condensed by the third condenser lens 52A. The liquid crystal shutter 53 includes a rod 52B and a fourth condenser lens 52C that condenses a light beam emitted from the light-transmitting rod 52B on the liquid crystal shutter 53.
The translucent rod 52B has a columnar shape with a substantially rectangular cross section, the cross-sectional shape is formed with the same aspect ratio as that of the DMD 30, the light beam incident from the incident end face is totally reflected on the side face, and a uniform illuminance distribution is obtained from the exit end face. A light beam that is emitted from the light beam and enters the photosynthetic path 50A via the DMD 30, that is, a light beam (a light beam with an uneven illuminance distribution) that is in an inverted state with respect to the image light that enters the projection optical system 40. Is reflected multiple times inside the translucent rod 52B to make the illuminance distribution uniform.
[0018]
The liquid crystal shutter 53 converts the alignment state of the liquid crystal by applying a voltage, and transmits and blocks the incident linearly polarized light beam. The two polarizing plates are orthogonal in polarization direction to sandwich the liquid crystal layer. Are arranged as follows.
In such a configuration, when the incident light beam passes through the liquid crystal shutter 53, the incident linearly polarized light beam is transmitted with the polarization angle rotated by 90 degrees. That is, when the incident P-polarized light passes through the liquid crystal shutter 53, it is emitted as S-polarized light.
The polarization beam splitter 51 is disposed on the illumination optical axis, transmits a light beam that is emitted from the illumination optical system and is converted into P-polarized light by the polarization conversion optical element 14, and is converted into S-polarized light by the liquid crystal shutter 53. Then, the light flux reflected by the polarization beam splitter 51 via the mirror 54 is reflected, and the two light fluxes are combined and emitted on the illumination optical axis.
[0019]
[3] Control structure of projector
FIG. 4 is a diagram schematically illustrating a control structure of the projector 1 according to the first embodiment.
The device control unit 60 includes a filter switching unit 61 for driving the color wheel 21, a signal processing unit 62 that supplies an image signal to the DMD 30 to convert the on / off state of the movable micromirror, and a signal processing unit 62. A liquid crystal shutter controller 63 for applying a voltage to the liquid crystal shutter 53 based on the output image signal.
The filter switching unit 61 rotates the color wheel 21 at a constant frequency of 240 Hz around the rotation axis 21A, and the luminous flux emitted from the light source lamp 11A is applied to the color wheel 21 in accordance with the rotation of the color wheel 21. The formed transmissive color filters 21R, 21G, 21B and the translucent area 21W are sequentially irradiated, and as a result, after passing through the color wheel 21, cyclically change as red light, green light, blue light, and white light. It is injected while doing.
[0020]
The signal processing unit 62 outputs an image signal to the DMD 30 in synchronization with the constant frequency 240 Hz of the filter switching unit 61, and turns on / off a movable micromirror corresponding to each pixel of red, green, and blue.
The liquid crystal shutter control unit 63 controls the liquid crystal shutter 53 in synchronization with the signal processing unit 62, and includes a peak detection unit 64 that performs arithmetic processing based on an image signal output from the signal processing unit 62, A control unit 65 for controlling the liquid crystal shutter 53 based on an output signal from the peak detection unit 64;
[0021]
From the image signal output from the signal processing unit 62, the peak detection unit 64 displays a display area of a red video, a green video, a blue video, and a white video, and a non-display area where none of red, green, blue, and white is displayed ( (A black image). In the entire image area, two states of the presence or absence of the display area (only the non-display area) are output to the control unit 65.
The control unit 65 controls the liquid crystal shutter 53 based on an output signal from the peak detection unit 64. If the display area calculated by the peak detection unit 64 does not exist in the entire image area, A voltage is applied to the liquid crystal shutter 53, and the incident light flux cannot be transmitted through the liquid crystal shutter 53 and is blocked. On the other hand, when the display area is present in the entire image area, no voltage is applied to the liquid crystal shutter 53. That is, the incident light flux passes through the liquid crystal shutter 53, and then is emitted with the polarization angle rotated by 90 degrees. Is done.
[0022]
[4] Effects of the first embodiment
According to the first embodiment, the following effects can be obtained.
(1) Of the light beams emitted by the DMD 30, the light beam that does not enter the projection optical system is provided with the light combining optical system 50 that causes the light beam that does not enter the projection optical system to enter the DMD 30 again. Can be supplied to the DMD 30 again by the photosynthetic optical system 50, so that when the display area and the non-display area are mixed in the projected image, the brightness of the display area is improved and the contrast ratio is increased. Can be.
(2) In addition, even if the movable micromirror of the DMD 30 is miniaturized in correspondence with high definition, that is, even if the pixel is reduced, the total amount of light incident on the movable micromirror can be increased. And a high contrast ratio can be realized.
(3) Since the total amount of light incident on the movable micromirror of the DMD 30 can be increased as described above, the amount of the projected image increases. Therefore, the distance between the screen 41 to be projected and the projector 1 can be sufficiently set, and even if the projected image is enlarged to correspond to a large screen display, an image having a sufficiently high contrast ratio can be viewed.
[0023]
(4) The provision of the photosynthetic optical system 50 prevents light beams emitted by the DMD 30 and not incident on the projection optical system 40 from being reflected by members in the projector 1 and taken into the projection optical system 40, so that stray light is prevented. This can prevent a decrease in the contrast ratio of the projected image due to, and can maintain a stable projected image.
(5) Since the photosynthetic optical system 50 includes the optical integrator 52, among the light beams emitted from the DMD 30, the illuminance distribution of the light beam that does not enter the projection optical system 40 is made uniform to emit a uniform light beam. , Can be incident on the DMD 30 again. Therefore, a light beam having a uniform illuminance distribution can be made incident on the DMD 30 without causing a light beam in an inverted state with respect to the image light to enter the DMD 30 again, so that the amount of image light increases and a high contrast ratio is obtained. Can be realized.
[0024]
(6) Since the optical integrator 52 condenses the light flux reflected by the DMD 30 and diverging into the photosynthetic path 50A and entering the DMF 30 via the mirror 54 and the polarizing beam splitter 51, the light is again incident on the DMD 30. There is no need to increase the size of the mirror 54 and the polarization beam splitter 51, and the members can be reduced in size.
(7) Since the photosynthesis optical system 50 includes the liquid crystal shutter 53, when the entire image area is a non-display area, the light beam that has entered the photosynthesis path 50A can be blocked, and the photosynthesis path 50A Can be prevented from increasing in the non-display area due to the luminous flux traveling through the DMD 30 entering the DMD 30 many times.
(8) By blocking the light beam of the liquid crystal shutter 53, surplus light is blocked when the entire image area is a non-display area, and heat generation due to light absorption of the DMD 30 and physical deformation such as thermal distortion are prevented. Can be.
[0025]
(9) Since the photosynthesis optical system 50 includes the polarization beam splitter 51, the light beam emitted from the light source lamp 11A and converted into P-polarized light by the polarization conversion optical element 14 is transmitted through the polarization beam splitter 51 and illuminated. The polarization beam splitter 51 can advance on the optical axis, further deviate on the illumination optical axis, enter the photosynthesis path 50 </ b> A, and reflect the S-polarized light by the liquid crystal shutter 53 by the polarization beam splitter 51. The beam can be advanced on the axis, and the two light beams can be combined to increase the total amount of light incident on the DMD 30.
(10) The filter switching unit 61 rotates the color wheel 21 in synchronization with the image signal input to the DMD 30, and switches the luminous flux emitted from the light source lamp 11A to red, green, and blue in time. A single DMD 30 can realize colorization of a projected image.
(11) Since the liquid crystal shutter control unit 63 includes the peak detection unit 64 and the control unit 65, the peak detection unit 64 performs the red image and the green image based on the image signal output from the signal processing unit 62. , The entire display area of the blue image and the white image, and the non-display area that does not display any of the red, green, blue, and white images are calculated and detected. A signal can be sent to the control unit 65 to apply a voltage to the liquid crystal shutter 53 to block a light beam incident on the liquid crystal shutter 53. Therefore, the control of the DMD 30 is synchronized with the image signal output from the signal processing unit 62, so that the transmission and blocking of the light beam by the liquid crystal shutter 53 can be performed in response to the ON / OFF of the movable micro mirror in the DMD 30. You can switch.
[0026]
[Second embodiment]
Next, a second embodiment of the present invention will be described.
In the following description, the same structures and the same members as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted or simplified.
In the projector 1 according to the first embodiment, the light combining optical system 50 includes an optical integrator 52, a liquid crystal shutter 53, a mirror 54, and a polarization beam splitter 51. Then, the liquid crystal shutter control unit 63 controls the liquid crystal shutter 53 based on the image signal output from the signal processing unit 62 to switch between transmitting and blocking the light flux traveling through the light combining path 50A.
[0027]
On the other hand, in the projector 2 according to the second embodiment, the light combining optical system 70 includes, in addition to the polarization beam splitter 71 and the optical integrator 72 described in the first embodiment, a mirror 73, a half-wave plate 74, The light absorbing member 75 is provided. The difference is that the device control unit 80 controls the tilting state of the mirror 73 and switches the deflection angle of the emitted light beam via the mirror 73.
[0028]
FIG. 5 is a diagram schematically illustrating the structure of the projector according to the second embodiment.
The mirror 73 is located on the emission side of the optical integrator 72 and is rotatably installed to change the tilt state. For example, as shown in FIG. 5, the mirror 73 is installed so as to be rotatable about an axis orthogonal to an optical path surface formed by the photosynthetic path 70A. As shown in FIG. 5, under the direction of the apparatus control unit 80, the tilt state of the mirror 73 is such that the light beam emitted from the optical integrator 72 is deflected in the direction of the polarization beam splitter 71. It is changed in two states of the inclined state in which the emitted light beam is deflected in the direction of the light absorbing member 75.
[0029]
The half-wave plate 74 is provided on the emission side of the light-transmitting rod 72B that forms the optical integrator 72. The light beam incident on the optical integrator 72 passes through the half-wave plate 74, and is emitted with its phase shifted by π.
The light absorbing member 75 absorbs the light beam deflected by the mirror 73. For example, the light absorbing member 75 is textured on its surface, and further coated with a multilayer antireflection film. With such a surface, reflection of an incident light beam can be prevented by the microscopic shape effect and the principle of interference.
[0030]
FIG. 6 is a block diagram illustrating a control structure of the projector according to the second embodiment.
The device control unit 80 includes a mirror control unit 83 in addition to the filter switching unit 81 and the signal processing unit 82 described in the first embodiment.
The mirror control unit 83 controls the tilt of the mirror 73 based on the image signal output from the signal processing unit 82. The mirror controller 83 includes a controller 85 in addition to the peak detector 84 described in the first embodiment.
The control unit 85 acquires two states of presence or absence of the display area detected by the peak detection unit 84, and changes the tilt state of the mirror 73 according to the two states.
[0031]
In the above configuration, the light beam emitted from the illumination optical system 10 passes through the polarization beam splitter 71 and enters the DMD 30. Of the light beams emitted from the DMD 30, the light beams that do not enter the projection optical system 40 enter the photosynthetic optical system 70, and are radiated via the optical integrator 72 to the mirror 73 as light beams having a uniform illuminance distribution. Here, the P-polarized light that has entered the optical integrator 72 passes through the half-wave plate 74, is shifted in phase by π, and is emitted as S-polarized light.
When the display area exists in the entire image area as a result of the calculation in the peak detection section 84, the control section 85 deflects the S-polarized light passing through the optical integrator 72 toward the polarization beam splitter 71. The tilt state of the mirror 73 is changed. Thereafter, the S-polarized light enters the DMD 30 again via the polarization beam splitter 71.
On the other hand, as a result of the calculation in the peak detecting section 84, when all the image areas are non-display areas, the control section 85 absorbs the S-polarized light passing through the optical integrator 72 as shown in FIG. The tilt state of the mirror 73 is changed so as to be deflected in the direction of the member 75. Thereafter, the S-polarized light enters the light absorbing member 75, is absorbed by the light absorbing member 75, and is converted into heat.
[0032]
According to the second embodiment, in addition to the effects similar to the above (1) to (6),
(12) Since the photosynthetic optical system 70 includes the mirror 73 and the light absorbing member 75 that can control the posture, when the entire image area is only the non-display area, the mirror 73 is tilted at a predetermined angle. In addition, it is possible to prevent the light flux that has entered the photosynthetic path 70A from being incident on the light absorbing member 75, and to prevent the light flux of the non-display image from increasing due to the light flux traveling in the photosynthetic path 70A being incident on the DMD 30 many times.
(13) Further, when the entire image area is a non-display area, it is prevented from entering the DMD 30 many times, so that heat generation due to light absorption of the DMD 30 and physical deformation such as thermal distortion can be prevented.
(14) Since the surface of the light absorbing member 75 is textured and further coated with a multilayer antireflection film, reflection of the light beam incident on the light absorbing member 75 is prevented, and the reflected light is projected onto the projection optical system. Thus, the contrast ratio of the projected image due to stray light can be prevented from lowering.
[0033]
(15) Since the half-wave plate 74 is provided on the emission side of the light-transmitting rod 72B, of the light flux emitted from the DMD 30, the light flux that does not enter the projection optical system 40 can be transmitted. When emitted as a light beam having a uniform illuminance distribution by 72B, the phase is shifted by π, and the P-polarized light is emitted as S-polarized light. Therefore, the S-polarized light that has passed through the half-wave plate 74 is reflected by the polarization beam splitter 71, travels again on the illumination optical axis, and is synthesized on the illumination optical axis together with the P-polarized light emitted from the illumination optical system 10. As a result, the total amount of light incident on the DMD 30 increases.
(16) Since the mirror control unit 83 includes the peak detection unit 84 and the control unit 85, the peak detection unit 84 performs a red image, a green image, and a green image based on the image signal output from the signal processing unit 82. When the entire display area of the blue image and the white image and the non-display area that does not display any of the red, green, blue, and white images are calculated and detected, and when the display area does not exist in the entire image area, A signal is sent to the control unit 85, the mirror 73 is tilted at a predetermined angle, the incident light beam is guided to the light absorbing member 75, and the light beam can be removed from the light combining path 70A. Therefore, in order to control the DMD 30, the inclination angle of the mirror 73 is changed in accordance with the ON / OFF of the movable micro mirror in the DMD 30 by being synchronized with the image signal output from the signal processing unit 82, and the DMD 30 It is possible to switch between re-entering and blocking the light beam to the light source.
[0034]
[5] Modification of the embodiment
Note that the present invention is not limited to the above-described embodiment, but includes other configurations that can achieve the object of the present invention, and also includes the following modifications and the like.
For example, in each of the above embodiments, the single-panel projectors 1 and 2 using only one DMD 30 are shown, but the present invention is also applied to a three-panel projector using three DMDs corresponding to R, G, and B. it can. In this case, three photosynthetic paths are required for each DMD.
Further, in each of the above embodiments, the optical integrators 52 and 72 including the translucent rods 52B and 72B are used for the light combining optical systems 50 and 70, but the illuminance distribution of the light beam entering the light combining paths 50A and 70A is changed. Other optical integrators may be used as long as they can be made uniform. For example, an optical integrator having the first lens array 12 and the second lens array 13 constituting the illumination optical system 10 of each of the above embodiments may be used.
[0035]
Further, for the purpose of making the illuminance distribution uniform, the first lens array 12 and the second lens array 13 arranged on the illumination optical axis and the translucent rods 52B, 72B arranged in the light combining paths 50A, 70A. Although two optical systems are used, a form used by only one optical system may be adopted. That is, a lens array type optical system such as a first lens array and a second lens array is disposed on the illumination optical axis between the polarization beam splitters 51 and 71 and the DMD 30, or a light transmitting rod is provided. A configuration in which such an optical system is arranged may be adopted.
Further, in each of the above embodiments, the color switching optical system 20 is used for the purpose of time-division of white light. However, the light flux from the light source is temporally switched to red, green, and blue using an LED light source or the like. The color display may be realized by turning on the light and displaying an image of the corresponding color component on the DMD in synchronization therewith.
[0036]
【The invention's effect】
As described above, according to the present invention, among the light beams modulated by the DMD, the light beam that does not function as the image light can be incident again on the DMD by the photosynthetic optical system, thereby improving the peak luminance and improving the high contrast. In addition to realizing the ratio, the brightness of the projected image can be ensured.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a structure of a projector according to the first embodiment.
FIG. 2 is a front view illustrating a structure of a color wheel in each of the embodiments.
FIG. 3 is a side view illustrating a structure of a DMD in each of the embodiments.
FIG. 4 is a block diagram illustrating a control structure of the projector according to the first embodiment.
FIG. 5 is a schematic view illustrating a structure of a projector according to the second embodiment.
FIG. 6 is a block diagram illustrating a control structure of a projector according to the second embodiment.
[Explanation of symbols]
1,2 projector
10. Illumination optical system
21 color wheel (color filter)
30 DMD (optical modulator)
40 Projection optical system
50A, 70A photosynthetic path
52,72 Optical integrator
53 liquid crystal shutter (second light modulation element)
61, 81 Filter switching unit
73 mirror (reflective optical element)

Claims (6)

A projector that includes a reflective light modulation element that modulates a light beam emitted from a light source according to image information by controlling an incident angle of a micromirror, and enlarges and projects the modulated light beam through a projection optical system. ,
A light combining path for combining a light flux modulated by the reflection type light modulation element and not entering the projection optical system again with a light flux emitted from the light source and introducing the light flux to the reflection type light modulation element is provided. Projector. The projector according to claim 1,
A second light modulation element that is arranged in the light combining path and switches between introduction and cutoff of a light flux that does not enter the projection optical system to the reflection type light modulation element in synchronization with the image information; A projector characterized by the following. The projector according to claim 2,
2. The projector according to claim 1, wherein the second light modulation element includes a liquid crystal shutter. The projector according to claim 2,
A reflective optical element is disposed in the light combining path, and reflects a light flux that does not enter the projection optical system and guides the light to the reflective light modulation element.
The projector according to claim 1, wherein the second light modulation element is configured to control an attitude of the reflection optical element in a light combining path. In the projector according to any one of claims 1 to 4,
A projector, comprising: an optical integrator that is arranged in the light combining path and that introduces a light beam that does not enter the projection optical system into a light beam having a uniform illuminance distribution onto a reflective light modulation element. The projector according to any one of claims 1 to 5,
The image information is configured to input an image signal corresponding to the color light to be modulated to the reflection type light modulation element in a time division manner,
A projector, wherein a filter switching unit that switches a color filter in synchronization with an image signal input to the reflection type light modulation element is provided between the light source and the reflection type light modulation element.

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