JP2008033339A - Image display device - Google Patents

Abstract

The present invention reduces contrast stray light due to specular reflection components and improves contrast.
An incident side lens group that creates a Fourier transform surface 12A in which positional information on a reflecting surface of a DMD 11 is converted into spread angle information formed by a light beam reflected by a micromirror 11B in an ON state and the optical axis of the DMD 11, and a Fourier A deformed stop 12B disposed near the conversion surface 12A and configured to shield and remove rays other than the reflected light from the micromirror 11B in the ON state according to the spread angle information, and an output for emitting the light transmitted through the deformed stop 12B to the screen 13 The projection lens includes a side lens group.
[Selection] Figure 1

Description

The present invention relates to an image display device that displays an image by irradiating light to a digital micromirror device (DMD ^™ , an abbreviation of Digital Micro-mirror Device, hereinafter DMD) that is a reflective spatial light modulator.

  The DMD is a reflective semiconductor element that is applied to, for example, an image display device including a projection screen and spatially modulates light intensity based on digital image information. Unlike a transmissive liquid crystal system that receives light from the condensing optical system at the rear surface and emits intensity-modulated light from the front surface to the projection optical system, an image display device using DMD is a condensing optical system. A projection optical system is provided on the reflection surface side of the DMD to constitute a reflection optical system.

  On the reflective surface of the DMD, 16 μm square-angle micromirrors are arranged corresponding to the number of pixels constituting a screen in a two-dimensional matrix at a pitch of 17 μm, specifically several hundred thousand or more. This micro mirror has a one-to-one correspondence with one pixel of the image. When the DMD receives light from the lamp light source via the condenser lens on the reflecting surface, each micro mirror modulates the light intensity according to the digital image information. To do. The intensity-modulated light is emitted from the reflecting surface as image information light by temporal ON / OFF control.

FIG. 22 is an enlarged view of a part of the reflection surface of the DMD.
In FIG. 22, reference numeral 101 denotes a DMD reflecting surface, 102 denotes a square micromirror provided on the reflecting surface 101, and O denotes a rotation axis for controlling the tilt of the micromirror 102. The micromirror 102 has a rotation axis O on its diagonal, and the incident direction of the principal ray incident on the micromirror 102 is parallel to the other diagonal with respect to the reflective surface 101 and the reflective surface. The incident angle is set to 20 ° with respect to the normal of 101.

  Each micromirror 102 can perform ON / OFF binary control around the rotation axis O by a control voltage based on the digital image information in the memory. Each inclination angle is set to ± 10 ° to switch the reflection direction of incident light. Next, the tilt control operation of the micromirror 102 will be described.

FIG. 23 is a diagram for explaining the operation of tilt control of the micromirror.
In FIG. 23, reference numeral 101 denotes a DMD reflecting surface. Here, the reflecting surface 101 is horizontal. 102A is a micromirror when the tilt angle with the reflecting surface 101 is + 10 °, 102B is a micromirror when the tilt angle with the reflecting surface 101 is −10 °, and O is the rotation axis of the micromirrors 102A and 102B. is there. In FIG. 23, the clockwise direction around the rotation axis O is a positive inclination angle, and the counterclockwise direction is a negative inclination angle.

  Reference numeral 103 denotes an incident principal ray incident on the micromirrors 102A and 102B from a condensing optical system (not shown), 104A denotes an emission principal ray from the micromirror 102A, 104B denotes an emission principal ray from the micromirror 102B, 105 denotes a screen, and 105A. Is one picture element of the screen 105 corresponding to the micromirrors 102A and 102B, 106 is a projection lens of the projection optical system provided between the reflective surface 101 of the DMD and the screen 105, and the projection lens 106 is an outgoing principal ray. 104A is projected onto one picture element 105A.

The incident principal ray 103 is incident on the micromirror 102A or 102B at an angle of 20 ° with the normal line n of the reflecting surface 101.
When light is projected onto one picture element 105A of the screen 105, the tilt angle is controlled to + 10 ° by the control voltage. At this time, the incident principal ray 103 is incident on the micromirror 102A at an angle of 10 ° with the normal line nA of the micromirror 102A. Therefore, according to the law of reflection, the incident principal ray 103 is reflected as a reflected principal ray 104A in the direction of the normal line n of the reflecting surface 101, and the picture element 105A of the screen 105 is brightened through the projection lens 106 (ON state).

  When light is not projected onto one picture element 105A of the screen 105, the tilt angle is controlled to −10 ° by the control voltage. At this time, the incident principal ray 103 is incident on the micromirror 102B at an angle of 30 ° with the normal line nB of the micromirror 102B. Therefore, according to the law of reflection, the incident principal ray 103 is reflected as a reflected principal ray 104B in a direction that forms an angle of 40 ° with the normal line n of the reflecting surface 101. Since the reflected principal ray 104B is directed in a direction away from the opening of the projection lens 106, one picture element 105A of the screen 105 is not brightened (OFF state).

  Thus, in the DMD, the micromirrors 102A and 102B are normally ON / OFF controlled at an inclination angle of ± 10 °. The time required for changing from the tilt angle + 10 ° (−10 °) to the tilt angle −10 ° (+ 10 °) is 10 μsec or less, and the DMD can modulate light at high speed.

  As can be seen from FIG. 23, since the micromirrors 102A and 102B are controlled to be inclined at an inclination angle of ± 10 °, the incident principal ray 103 and the outgoing principal ray 104B in the OFF state form an angle of 60 °. On the other hand, the incident principal ray 103 and the outgoing principal ray 104A in the ON state are closest to each other at an angle of 20 °. In light of this, it can be seen that the F value of the light beam that can be incident on the DMD is limited by the tilt angle ± 10 ° of the micromirror.

FIG. 24 is a diagram illustrating a state in which a conical light beam of F = 3 is incident on the micromirror in the ON state. The same reference numerals are given to the same or corresponding components as those in FIG.
In FIG. 24, reference numerals 107 and 108 denote conical incident light fluxes and outgoing light fluxes with F = 3 (spreading angle 10 °, solid angle) with the center of the micromirror as the apex. The incident light beam 107 and the outgoing light beam 108 represent how the light on the incident side and the outgoing side spread when observed from the center of the micromirror.

  107A and 107B are incident light beams included in the incident light beam 107, and 108A and 108B are output light beams included in the output light beam 108. The incident ray 107A is closest to the outgoing principal ray 104A, and the incident ray 107B is farthest from the outgoing principal ray 104A. Further, the outgoing light beam 108 A is closest to the incident principal light beam 103, and the outgoing light beam 108 B is farthest from the incident principal light beam 103.

  In other words, the incident light beams 107A and 107B are the outermost incident light beams, respectively, enter the micromirror 102A at a divergence angle θ = 10 ° with the incident principal light beam 103, reflected by the micromirror 102A, and output light beams 108A. , 108B. 109A is a plane orthogonal to the optical axis nA, and FIG. 24B shows the incident light beam 107 and the outgoing light beam 108 of FIG. 24A when cut by the plane 109A. FIG. 24B shows an incident light beam 107 and an outgoing light beam 108 when the light beams 103 and 104A are regarded as parallel for convenience.

  In the micromirror 102A in the ON state in FIG. 24A, the incident chief ray 103 and the outgoing chief ray 104A form an angle of 20 °, and therefore the spread angle θ of the incident light beam 107 with the incident chief ray 103 as the center. Is set to be a constant amount in any direction, the incident light beam 107A and the outgoing light beam 108A coincide on the same normal line nA when the angle θ = 10 ° (FIG. 24B).

  Therefore, when the angle θ exceeds 10 °, a part of the incident light beam 107 including the incident light beam 107A interferes with a part of the output light beam 108 including the output light beam 108A. That is, the illumination optical system that provides the incident light beam and the projection optical system that captures the outgoing light beam are structurally overlapped. For this reason, the angle θ is set to 10 ° while avoiding interference between the incident light beam 107 and the outgoing light beam 108.

  At this time, when the refractive index in the air is set to 1 and the F value is obtained from F = 1 / [2 sin (θ)], it is found that the minimum value of the F value is about 3. In general, the F value represents the brightness of the optical system, and the smaller the F value (the larger the θ), the brighter the optical system. Therefore, the light is collected to the micromirror 102A controlled to tilt at an inclination angle of ± 10 °. In the conventional condensing optical system that emits light, the brightest optical system can be formed when a conical light beam of F = 3, that is, θ = 10 ° is incident.

Next, an image display apparatus using a condensing optical system for DMD will be described. FIG. 25 is a diagram showing a configuration of an image display apparatus using a conventional condensing optical system.
In FIG. 25, 111 is a light emitter that emits light, and 112 is a parabolic reflector having a paraboloid shape that has the light emitter 111 as a focal point. The light emitter 111 and the parabolic reflector 112 constitute a lamp light source. A condensing lens 113 condenses the light reflected by the parabolic reflector 112, and a color wheel 114 separates the light from the condensing lens 113 into three primary colors. In the following, the explanation will be given with a single-plate method capable of irradiating the RGB three primary colors in a time-sharing manner using a single color wheel to reproduce the color space of the three primary colors. In some cases.

  115 is a quadrangular prism-shaped rod integrator that receives light from the color wheel 114 at the incident end face and emits light having a uniform luminance distribution from the exit end face; 116 is a relay lens that relays light from the rod integrator 115; A folding mirror 119 that bends the optical path is a field lens that aligns the principal ray direction of each point in the incident light beam.

  Reference numeral 120 denotes a TIR prism. In order to prevent the incident light beam from being vignetted by the incident portion of the projection optical system, only the incident light beam is totally reflected, and the emitted light beam is allowed to travel straight and pass as it is. It functions to structurally separate the projection optical system. Reference numeral 121 denotes the DMD described above, 122 denotes a projection lens that forms an image of the intensity-modulated light of the DMD 121, 123 denotes a rear projection screen that receives the light imaged by the projection lens 122 from the back and displays an image, and 124 denotes an image display. This is an optical axis shared by each component of the apparatus.

Next, the operation will be described.
Since the light emitter 111 aiming at a point light source as much as possible is installed at the focal point of the parabolic reflector 112, the light emitted from the light emitter 111 is reflected by the parabolic reflector 112 and emitted as almost parallel light. The condensing lens 113 condenses the parallel light from the parabolic reflector 112 at the focal point as a conical light beam having F1 = 1 (a spread angle θ1 = 30 ° formed with the optical axis 124). When the color wheel 114 is used, it is necessary to reduce the light collection diameter, so F = 1 is generally selected as the optimum F value.

  The incident end face of the rod integrator 115 is installed at the focal point of the condenser lens 113, and light having only a color designated by the color wheel 114 enters the rod integrator 115 from the rectangular incident end face. The light that has entered the rod integrator 115 is averaged by reflecting the side surface of the rod integrator 115 a plurality of times, and has a substantially uniform light intensity distribution within the surface at the exit end surface.

  The light emitted from the exit end face of the rod integrator 115 is emitted at F1 = 1, like the incident light on the entrance end face, and enters the TIR prism 120 via the relay lens 116, the folding mirror 118, and the field lens 119. Incident light to the TIR prism 120 is reflected inside the TIR prism 120 and irradiated to the DMD 121. The DMD 121 gives image information to the light flux by digital image information and emits intensity-modulated light. At this time, F = 3 is selected as the optimum value for the light toward the DMD 121. The image information light emitted from the DMD 121 passes through the TIR prism 120 again and is projected from the projection lens 122 onto the screen 123.

  In the image display device described above, the incident end surface and the output end surface of the rod integrator 115 and the reflecting surface of the DMD 121 are determined by the F value of the incident light beam on the incident end surface of the rod integrator 115 and the F value of the incident light beam on the reflecting surface of the DMD 121. The size ratio is determined.

  FIG. 26 is a diagram for explaining the relationship between the rod integrator and the DMD. The same or corresponding components as those in FIG. 25 are denoted by the same reference numerals. The folding mirror 118, the field lens 119, the TIR prism 120, etc. are not shown, and the characteristics of the field lens 119 are included in the relay lens 116. It is shown. Originally, the incident light on the DMD is incident from a direction of 20 ° with respect to the DMD optical axis, but only the incident condition on the DMD will be discussed below, so that the figure in the case where the incident principal ray is incident perpendicularly on the DMD is also convenient. I will use it.

  In FIG. 26, w is the length of one side of the incident end face and the exit end face of the rod integrator 115, a is the length of the optical axis 124 from the rod integrator 115 to the relay lens 116, and b is the optical axis 124 from the relay lens 116 to the DMD 121. , W is the length of one side of the reflecting surface of the DMD 121.

  Θ1 is an opening angle formed by the light beam from the exit end face of the rod integrator 115 and the optical axis 124, and θ2 is an opening angle formed by the light beam incident on the reflecting surface of the DMD 121 and the optical axis 124. In general, when the angles θ1 and θ2 are not so large, the relational expression of w / W = a / b = θ2 / θ1 = F1 / F2 holds approximately.

  Since θ1 = 30 ° (F = 1) in order to use the color wheel 114, and θ2 = 10 ° (F2 = 3) based on the use conditions of the DMD 121 controlled to tilt at an inclination angle of ± 10 °, w A relational expression of / W = a / b = F1 / F2 = 1/3 is obtained. That is, in the optical system of FIG. 26, the light from the rod integrator 115 with one side length w is irradiated to the DMD 121 with one side length W at a magnification W / w = 3 through the relay lens 116. Thus, when the reflecting surface size and the angles θ1 and θ2 of the DMD 121 are determined, the exit end surface (incident end surface) size of the rod integrator 115 is also automatically determined.

  Since the conventional condensing optical system is configured as described above, the F value of the incident light beam on the DMD is restricted by the tilt angle, and the incident end face of the rod integrator can be enlarged to reduce the loss. However, there is a problem that the brightness of the optical system is limited.

The above problem will be described specifically.
In the condensing optical system applied to the image display apparatus of FIG. 25, light emitted in all directions from the light emitter 111 aiming at a point light source as much as possible is reflected by the parabolic reflector 112 and the condensing lens 113 at F1 = 1 (light A light beam having an opening angle of 30 ° with the shaft 124 is converted and condensed onto the incident surface of the rod integrator 115. As shown in FIG. 27B, the light collection distribution 125 on the incident surface 115 </ b> A of the rod integrator 115 at this time is a rotating object with respect to the optical axis 124.

  Here, if the size of the lamp light source is infinitely small, the light condensing area on the rod integrator 115 becomes zero, and all light is taken into the rod integrator 115. However, in reality, the light emitter 111 has a finite size, and reducing the light emitted in all directions to an opening angle of 30 ° is based on the same principle as that of a relay lens. The projected image is enlarged and irradiated onto the incident surface of the rod integrator 115 as a projected image.

  The projected image 125A of the lamp light source is larger than the incident surface 115A of the rod integrator 115 (FIG. 27 (c)), and not all the light from the lamp light source is taken into the incident surface 115A. It is vignetting and wasted, leading to a reduction in overall light utilization efficiency.

  If the incident end face of the rod integrator 115 is increased in order to reduce the vignetting of the light, as described above, the F value (F1 = 1) of the light from the condenser lens 113 and the F value of the light to the DMD 121 are obtained. Since (F2 = 3) is determined, the size of the DMD 121 must be increased so as to satisfy the relationship of the magnification W / w = 3, leading to an increase in cost.

  Further, since the conventional image display apparatus picks up light in a wide angle range with the projection lens, the angle of the specular reflection component generated in the DMD or TIR prism is partially included as stray light, and the contrast is deteriorated. There was a problem.

  The present invention has been made to solve the above-described problems, and reduces the loss by increasing the incident end face of the rod integrator without being restricted by the F value of the incident light beam on the DMD due to the inclination angle. An object of the present invention is to construct an image display device for DMD that can improve the brightness of an optical system.

  Another object of the present invention is to construct an image display device capable of reducing stray light due to specular reflection components and improving contrast.

  In the image display device according to the present invention, the projection optical system includes a light beam reflected on the reflection surface of the reflective spatial light modulator by the micromirror in the ON state and the reflective spatial light modulator. An incident-side lens group that creates a Fourier transform surface converted into divergence angle information formed by the optical axis, and a light beam other than the reflected light from the micromirror in the ON state is arranged in the divergence angle information. Therefore, the light source includes a first deformed diaphragm that shields and removes, and an exit-side lens group that emits light transmitted through the first deformed diaphragm to the screen, and the condensing optical system transmits light emitted from the lamp light source. A condensing lens that condenses the first F-number light flux, a light intensity distribution uniformizing element that emits the first F-value light flux with a uniform intensity distribution on the exit end face thereof, and the first A relay system that relays an F-value light beam as a second F-value light beam to the reflective spatial light modulator, and reflects the width in the first coordinate axis direction perpendicular to the optical axis of the condenser lens to reflect the light beam. And the width of the light in the second coordinate axis direction perpendicular to the optical axis of the condenser lens and the first coordinate axis is set based on the F value determined by the inclination angle of the type spatial light modulator. A light converting means for emitting the light with a width larger than the width of the light in the coordinate axis direction is provided between the lamp light source and the condenser lens, and the relay system includes a rotating shaft of the reflective spatial light modulator and the first light source. The light flux is relayed with the direction of the coordinate axis of 2 in parallel.

  In the image display device according to the present invention, the light conversion means includes a cylindrical lens group having an optical axis that coincides with the optical axis of the condenser lens and having a lens action only in the first coordinate axis direction. .

  In the image display device according to the present invention, the light converting means parallels the light from the lamp light source emitted obliquely with respect to the optical axis of the condenser lens in parallel with the optical axis of the condenser lens only in the first coordinate axis direction. The prism is refracted in any direction.

  In the image display device according to the present invention, the lamp light source is composed of a light emitter that emits light and a parabolic reflector provided with the light emitter at a focal point, and the light conversion means is an aperture plate provided at the opening of the parabolic reflector. It is a thing.

  In the image display device according to the present invention, the optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, and θx When the direction orthogonal to the direction is defined as the θy direction, the first deformed diaphragm has a substantially D-shaped opening that shields and removes light having an angle of θc or more in the θx direction from the optical axis in the ON state. It is what I did.

  In the image display device according to the present invention, when the switching angle between the ON state and the OFF state of the micromirror is ± θDMD, and the angle at which transmission is allowed by the first deformation diaphragm is θp, The deformation diaphragm has an opening that satisfies 0.5θDMD ≦ θc ≦ θp.

  In the image display device according to the present invention, the first deformation stop has an opening satisfying θc≈θDMD.

  In the image display device according to the present invention, the optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, and θx When the direction orthogonal to the direction is defined as the θy direction, the first deformed aperture is a substantially oval aperture that shields and removes light having an angle of ± θc ′ or more in the ± θx direction from the optical axis in the ON state. It is made to have.

  In the image display device according to the present invention, the switching angle between the ON state and the OFF state of the micromirror on the reflective spatial light modulation element surface is ± θDMD, and the angle at which transmission is allowed by the first deformed diaphragm is θp. In this case, the first deformed diaphragm has an opening that satisfies 0.5θDMD ≦ θc ′ ≦ θp.

  In the image display device according to the present invention, the first deformation stop has an opening satisfying θc′≈θDMD.

  According to the present invention, the projection optical system includes the light beam reflected by the micromirror in the ON state, the optical axis of the reflective spatial light modulator, and the positional information on the reflective surface of the reflective spatial light modulator. An incident-side lens group that creates a Fourier transform surface converted into divergence angle information formed by the light source, and is arranged in the vicinity of the Fourier transform surface, and shields and removes light rays other than the reflected light from the micromirror in the ON state according to the divergence angle information And a light-exiting lens group that emits light that has passed through the first deformed stop to the screen, and the condensing optical system transmits light emitted from the lamp light source to the first light source. A condensing lens that collects light as an F-value light beam, a light intensity distribution uniformizing element that emits the first F-value light beam with a uniform intensity distribution at its exit end surface, and the first F-value light beam A relay system that relays to the reflective spatial light modulator as the second F-number light beam, and the width of the reflective spatial light modulator in the first coordinate axis direction orthogonal to the optical axis of the condenser lens And the width of the light in the second coordinate axis direction orthogonal to the optical axis of the condenser lens and the first coordinate axis, respectively, and the light in the first coordinate axis direction. A light converting means for emitting light with a width larger than the width of the light source and the condenser lens, wherein the relay system includes a rotation axis of the reflective spatial light modulator and the second coordinate axis direction. Since the light flux is relayed in parallel with each other, stray light due to the specular reflection component can be reduced, and an effect can be obtained in which an image with clearer and brighter contrast can be displayed. In addition, the brightness of the optical system can be improved without restricting the F value of the incident light beam by the tilt angle of the digital micromirror device.

  According to the present invention, the light converting means is a cylindrical lens group having an optical axis that coincides with the optical axis of the condensing lens and having a lens function only in the first coordinate axis direction. There is an effect that the brightness of the optical system can be improved without restricting the F value of the incident light beam by the inclination angle.

  According to the present invention, the light converting means is configured to emit light from the lamp light source that is emitted obliquely with respect to the optical axis of the condenser lens in a direction parallel to the optical axis of the condenser lens only in the first coordinate axis direction. Since the refracting prism is used, the brightness of the optical system can be improved without restricting the F value of the incident light beam by the inclination angle of the digital micromirror device.

  According to the present invention, the lamp light source is composed of a light emitter that emits light and a parabolic reflector provided with a light emitter at the focal point, and the light conversion means is an aperture plate provided at the opening of the parabolic reflector. In addition, there is an effect that the brightness of the optical system can be improved without restricting the F value of the incident light beam by the tilt angle of the digital micromirror device.

  According to the present invention, the optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, and is orthogonal to the θx direction. When the direction to be operated is defined as the θy direction, the first deformed diaphragm has a substantially D-shaped opening that shields and removes light having an angle of θc or more in the θx direction from the optical axis in the ON state. Therefore, the stray light due to the specular reflection component can be reduced, and an effect of displaying an image with clearer and brighter and higher contrast can be obtained.

  According to this invention, when the switching angle between the ON state and the OFF state of the micromirror is ± θDMD and the angle at which transmission is allowed by the first deformation aperture is θp, the first deformation aperture is , 0.5θDMD ≦ θc ≦ θp is provided, so that stray light due to the specular reflection component can be reduced, and an effect that a brighter and clearer and higher contrast image can be displayed can be obtained.

  According to the present invention, since the first deformed diaphragm has an opening satisfying θc≈θDMD, stray light due to the specular reflection component can be reduced, and a brighter and clearer and higher contrast image can be displayed. The effect is obtained.

  According to the present invention, the optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, and is orthogonal to the θx direction. When the direction to be operated is defined as the θy direction, the first deformed diaphragm has a substantially elliptical opening that shields and removes light having an angle of ± θc ′ or more in the ± θx direction from the optical axis in the ON state. As a result, stray light due to the specular reflection component can be reduced, and an effect can be obtained in which a brighter and clearer and higher contrast image can be displayed.

  According to this invention, when the switching angle between the ON state and the OFF state of the micromirror on the reflective spatial light modulation element surface is ± θDMD, and the angle at which transmission is allowed by the first deformed diaphragm is θp. Since the first deformed aperture has an opening that satisfies 0.5θDMD ≦ θc ′ ≦ θp, stray light due to the specular reflection component can be reduced, and a brighter and clearer and higher contrast image can be displayed. The effect is obtained.

  According to the present invention, since the first deformed diaphragm has an opening satisfying θc′≈θDMD, stray light due to the specular reflection component can be reduced, and a brighter and clearer and higher contrast image is displayed. The effect that it can be obtained.

An embodiment of the present invention will be described below.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an image display apparatus using a condensing optical system according to Embodiment 1 of the present invention.
In FIG. 1, reference numeral 1 denotes a light emitter (condenser optical system, lamp light source) that emits light, and 2 denotes a parabolic reflector (condenser optical system, concentrator) having a light emitter 1 at the focal point. Lamp light source), and the light source 1 and the parabolic reflector 2 constitute a lamp light source. The lamp light source of the condensing optical system may be a type that directly converts a point light source to a point light source using an elliptical reflector. 3 is a condensing lens (condensing optical system) that condenses the light reflected by the parabolic reflector 2, and 4 is a color wheel that separates the light from the condensing lens 3 into three primary colors. In the following, the explanation will be given with a single-plate method capable of irradiating the RGB three primary colors in a time-sharing manner using a single color wheel to reproduce the color space of the three primary colors. In some cases.

  5 is a quadrangular prism-shaped rod integrator (condensing optical system, light intensity distribution uniformizing element) that receives light from the color wheel 4 at the incident end face and emits light with uniform luminance distribution from the exit end face; A first lens group for collimating the light from the rod integrator 5 (condensing optical system system, relay system, shown as a single lens in FIG. 1), 7 is a deformed stop (condensing light) for shaping the emitted light beam from the rod integrator 5 An optical system, a relay system, and a second deformation stop; 8 is a folding mirror that bends the optical path; and 9 is a second lens group that aligns the principal ray directions of each point in the incident light beam (condensing optical system, relay system, In FIG. 1, a single lens is shown). The first lens group 6, the deformed diaphragm 7, and the second lens group 9 are components that characterize the first embodiment, and generate an asymmetric light beam to be described later. Further, the light intensity distribution uniformizing element is not limited to the rod integrator 5, and the light intensity distribution can be uniformized by using a light pipe or a fly-eye lens instead.

  Reference numeral 10 denotes a TIR prism. In order to prevent the incident light beam from being vignetted by the incident portion of the projection optical system, only the incident light beam is totally reflected, and the emitted light beam is allowed to travel straight and pass through as it is. It functions to optically separate the projection optical system. Note that the TIR prism 10 is not an essential component of the present invention, and an image display apparatus can be configured without using the TIR prism 10. Reference numeral 11 denotes a DMD (reflection type spatial light modulation element) that spatially modulates light by a large number of micromirrors whose inclination is controlled at an inclination angle of ± 10 °. Optical system), 12A is a Fourier transform plane (projection optical system) by the first lens group in the projection lens 12, 12B is a modified diaphragm (projection optical system, first modified diaphragm) in the projection lens 12, and 13B. Is a rear projection screen that receives the light imaged by the projection lens 12 from the back and displays an image, and 14 is an optical axis shared by each component of the image display device.

Next, the operation will be described.
Since the light emitter 1 having a short arc length and close to a point light source is installed at the focal point of the parabolic reflector 2, the light emitted from the light emitter 1 is reflected by the parabolic reflector 2 and emitted as almost parallel light. The condensing lens 3 condenses the parallel light from the parabolic reflector 2 at the focal point as a conical light beam of F1 = 1 (a spread angle θ1 = 30 ° with the optical axis 14). When the color wheel 4 is used, it is necessary to reduce the condensing diameter, and therefore F1 = 1 (first F value) is generally selected as the optimum F value.

  The incident end face of the rod integrator 5 is installed at the focal point of the condenser lens 3, and the light of which only the color designated by the color wheel 4 is selected enters the rod integrator 5 from the rectangular incident end face. In the first embodiment, the incident end face (outgoing end face) size w of the rod integrator 5 is set to W / 2 with respect to the reflecting face size W of the DMD 11, and the magnification W / w = 2. Compared with the prior art, the incident end face size of the rod integrator 5 is set larger, so that the light receiving efficiency from the condenser lens 3 is improved.

  The light incident on the rod integrator 5 is averaged by reflecting the wall surface of the rod integrator 5 a plurality of times, and the light intensity distribution is substantially uniform within the surface at the exit end face. The light emitted from the exit end face of the rod integrator 5 is emitted at F1 = 1, similarly to the incident light on the entrance end face, and passes through the first lens group 6, the deformed stop 7, the folding mirror 8, and the second lens group 9. It is converted into an asymmetrical light beam and enters the TIR prism 10.

  The asymmetric light beam incident on the TIR prism 10 is reflected inside the TIR prism 10 and irradiates the DMD 11. The DMD 11 emits intensity-modulated light in which image information is given to an asymmetric light beam by digital image information. The intensity-modulated light emitted from the DMD 11 passes through the TIR prism 10 again and is projected from the projection lens 12 onto the screen 13.

  Now, in order to improve the light receiving efficiency as compared with the conventional case (W / w = 3), the magnification W / w = 2 is set in the first embodiment, so w / W = θ2 / θ1 = F1. From the relationship of / F2, the F value of the light irradiating the DMD 11 is F2 = 2 (second F value, spread angle θ2 = 15 °). In the case of F2 = 2, the following problem occurs according to the conventional configuration.

FIG. 2 is a diagram illustrating a state where a conical light beam of F2 = 2 is incident on the micromirror in the ON state.
In FIG. 2, 15 is a horizontally installed DMD reflection surface, n is a normal line of the DMD reflection surface 15, 16 is a DMD micromirror, and nA is a normal line of the micromirror 16. The micromirror 16 is controlled to be tilted to the ON state, and forms a tilt angle of + 10 ° with respect to the DMD reflecting surface 15. At this time, the normal line nA and the normal line n form an angle of θ = 10 °.

  Reference numeral 17 denotes an incident principal ray incident on the center of the micromirror 16, reference numeral 18 denotes an incident luminous flux with F2 = 2 (spreading angle 15 °, solid angle) centered on the incident principal ray 17, and reference numerals 18A and 18B respectively include the incident luminous flux 18. 19 is an outgoing chief ray reflected from the incident principal ray 17 by the micromirror 16, 20 is an outgoing flux of F2 = 2 centered on the outgoing principal ray 19, and 20A and 20B are included in the outgoing luminous flux 20, respectively. It is an outgoing ray.

  The incident light beam 18 and the outgoing light beam 20 represent how the light on the incident side and the outgoing side spread when observed from the micromirror 16. The incident ray 18A is closest to the outgoing principal ray 19 and the incident ray 18B is farthest from the outgoing principal ray 19. Further, the outgoing light ray 20A is closest to the incident principal ray 17, and the outgoing light ray 20B is farthest from the incident principal ray 17.

  That is, the incident light beams 18A and 18B are light beams in the outermost incident light beam, respectively, enter the micromirror 16 at an angle θ2 = 15 ° with the incident principal light beam 17, reflected by the micromirror 16, and output light beams, respectively. 20A and 20B.

  21 is an interference component between the incident light beam 18 and the outgoing light beam 20, 22A is a plane perpendicular to the incident principal ray 17, 22B is a plane perpendicular to the outgoing principal ray 19, and the incident light beam 18 cut by the plane 22A is a plane 22B. A cross section of the cut outgoing light beam 20 is shown in FIG. In FIG. 2B, the incident principal ray 17 and the outgoing principal ray 19 are regarded as parallel for convenience. For comparison, FIG. 12B is repeated in FIG.

  In the micromirror 16 controlled to tilt at an inclination angle of ± 10 °, the incident principal ray 17 has an angle θ = 10 ° with the normal nA, and the outgoing principal ray 19 has an angle θ with the normal nA according to the law of reflection. = 10 °, the incident principal ray 17 and the outgoing principal ray 19 form an angle of 20 °. In such a case, when an incident light beam 18 having a spread angle θ2 = 15 ° is incident on the micromirror 16, an interference component 21 (shaded portion in FIG. 2) is generated between the incident light beam 18 and the outgoing light beam 20.

  Comparing FIG. 2 (b) and FIG. 2 (c), the light flux in FIG. 2 (b) with the divergence angle θ2 = 15 ° is larger than that in the conventional FIG. 2 (c) with the divergence angle set to 10 °. The cross-sectional area of the light source can be increased to improve the illumination efficiency of light utilization, but since the interference component 21 is generated, it has been considered that an incident light beam having an F value smaller than F2 = 3 cannot enter the DMD. It was a design standard.

  The idea that the design of the optical system must be constrained so as to avoid the generation of the interference component 21 is a conventional basic design. In an optical system constructed based on this idea, F determined by the tilt angle of the DMD. The value is restricted and the brightness of the image display device cannot be improved.

  On the other hand, in the first embodiment, the brightness of the optical system is improved by making a light beam having an F value of F2 = 2 incident on the DMD, in accordance with the conventional basic design. At this time, in order to generate an asymmetrical light beam obtained by removing the interference component 21 from the incident light beam of F2 = 2, the first lens group 6, the modified diaphragm 7, and the second lens group 9 are provided as a relay system. Hereinafter, specific operations of the first lens group 6, the deformed diaphragm 7, and the second lens group 9 will be described in detail.

  FIG. 3 is a diagram for explaining the function of the first lens group 6 and the second lens group 9. 1 are assigned the same reference numerals, and for convenience of explanation, the folding mirror 8 and the TIR prism 10 are not shown, and the incident principal ray is perpendicular to the reflecting surface of the DMD 11. Incident.

  In FIG. 3, reference numerals 23 denote F = 1 light beams respectively emitted from the three points A, B, and C on the emission end face of the rod integrator 5. Here, the light beam 23 from points A, B, and C is considered as a representative. The light beam 23 emitted from the point A (one dotted line), the light beam 23 emitted from the point B (solid line), and the light beam 23 emitted from the point C (broken line) are all emitted from the emission end face of the rod integrator 5 with F1 = 1. ing.

  The chief rays of each luminous flux 23 are marked with ◯, and the X rays and △ marks are given to each of the parallel rays emitted with a divergence angle of θ1 = 30 ° with each chief ray of ○ mark. It is attached. Of these, the light beam marked with x and the light beam in the vicinity thereof become the interference component 21 in FIG.

  Each light beam 23 emitted from the points A to C on the emission end face of the rod integrator 5 at a spread angle θ1 = 30 ° is incident on the first lens group 6. Since the first lens group 6 acts to collimate all the light rays contained in each light beam 23, the light beams emitted from the points A to C are marked with the optical axis 14. They are collected at points D, E, and F on the orthogonal Fourier transform plane 7A.

  That is, the first lens group 6 performs two-dimensional Fourier transform on the position information of the exit end face of the rod integrator 5 to spread angle information. Therefore, at the points D to F on the Fourier transform plane 7A, all the light beams having the same spread angle θ1 are collected at the same one point, and the light beam with x mark, the light beam with ○ mark, and the light beam with Δ mark are point D. , E, F.

  Each light beam transmitted through the points D to F enters the second lens group 9. The second lens group 9 functions to make a light flux of F2 = 2 incident on each point G, H, I of the DMD 11 reflecting surface. In the light flux incident on each of the points G to I, the light beam of the X mark and the light beam of the Δ mark form a spread angle θ2 = 15 ° with respect to each principal ray marked with a circle.

  FIG. 4 is a diagram showing the cross-sectional shapes of the light beam emitted from the rod integrator, the deformed stop, and the asymmetric light beam. 4A is a cross-sectional shape of the emitted light beam 23 of F = 1 emitted from the rod integrator, FIG. 4B is a cross-sectional shape of the deformed stop 7, and FIG. 4C is a cross-sectional shape of the asymmetric light beam incident on the DMD 11. It is. 1 and 3 are denoted by the same reference numerals. From the characteristics of the DMD and TIR prism, the cross-sectional shape of the deformed diaphragm is optimally a D-shape that is slightly curved, as shown in FIG.

  In FIG. 4, 7Z is a shielding part provided in the deformed stop 7, which shields and removes light rays that generate interference components. The part other than the shielding part 7Z is a D-shaped opening of the deformation stop 7. Reference numeral 24 denotes an asymmetrical light beam formed by the deformed stop 7, 24Z denotes a partial light beam shielded and removed by the shielding portion 7Z of the deformed stop 7, and the partial light beam 24Z generates the interference component 21 of FIG.

  FIG. 5 is a diagram for explaining the function of the deformation diaphragm 9. 1 and 3 are denoted by the same reference numerals. 5, in the optical system of FIG. 3 comprising the first group lens 6 and the second group lens 9, the deformed diaphragm 7 of FIG. 4B is placed in the vicinity of the Fourier transform plane 7A with the aperture orthogonal to the optical axis. It is installed.

  The deformed stop 7 installed on the Fourier transform plane 7A shields and removes the light beam indicated by x and the light beam in the vicinity thereof (partial light beam 24Z generating the interference component 21) included in the interference component 21 by the shielding portion 7Z. . Therefore, in FIG. 5, a light beam of □ (a spread angle of 20 °) that forms an angle of 20 ° with the chief ray of ○ mark, a light beam of a △ mark that forms an angle of 30 ° with the chief light beam of ○, The chief ray passes through the aperture of the deformed stop 7 and enters the second lens group 9. In the above description, the deformed diaphragm has been described as having an obvious opening. However, when the circular portion is limited on the incident side, the same action can be obtained only by the shielding portion 7Z in FIG.

  The second lens group 9 irradiates points G to I of the DMD 11. Since the broken line, the solid line, and the one-point broken line are condensed on the points G to I, and the light beam marked with x is shielded and removed by the deformation stop 7, it enters the points G to H. Each asymmetrical light beam 24 including a light beam of Δ mark having a divergence angle of 15 ° and a light beam of □ mark having a divergence angle of 20 ° is incident on the DMD 11 with respect to the chief ray of the mark ○. As described above, the first lens group 6, the deformed stop 7, and the second lens group 9 produce an asymmetric light beam 24.

FIG. 6 is a diagram illustrating a state in which the asymmetric light beam is incident on the micromirror in the ON state. The same or corresponding components as those in FIG. 2 are denoted by the same reference numerals. The relay system here may have the same configuration as the conventional one.
The asymmetrical incident light beam 18Z incident on the DMD micromirror 16 includes an incident light beam 18B and an incident light beam 18C. The incident light beam 18B corresponds to the light beam marked with Δ in FIGS. Further, the incident light ray 18C is a light ray that comes into contact with the interference component 21 in FIG. 2 that has been shielded and removed by the shielding portion 7Z of the deformed diaphragm 7, and corresponds to the light beam marked with a square in FIG. It becomes the light ray 20C.

  The asymmetric light beam 18Z can illuminate more micromirrors 16 of the DMD 11 than the conventional light beams 107 and 108 shown in FIG. Therefore, the light is reflected by the micromirror 16 without interfering with the asymmetrical emitted light beam 20Z. The hatched portion in FIG. 6B is the effect of the first embodiment and corresponds to the improvement result of the illumination efficiency.

  The shape of the shielding portion 7Z is designed so that the interference component 21 does not occur according to the F value and the incident angle of the light beam incident on the DMD 11.

  By applying the asymmetric optical system described above, the brightness of the optical system can be improved. By the way, compared with the conventional optical system, the angle range to be irradiated is particularly wide in the asymmetric optical system, and a projection lens having a small F value is used in order to pick up all the light rays in the wide angle range. If the projection lens picks up light in such a wide angle range, the angle of the specular reflection component is partially included (light rays other than ON, that is, stray light enters the aperture of the projection lens), the contrast deteriorates, and black and white An unclear image will appear on the screen.

First, the first cause of contrast deterioration will be described.
FIG. 7 is a diagram for explaining a first cause of contrast deterioration in an asymmetric optical system. As shown in FIG. 7, the stray light that deteriorates the contrast is caused by the reflected light C1 from the DMD facing surface 10A of the TIR prism 10 and the reflected lights C2 and C3 from the cover glass 11A of the DMD chip 11. There is a reflectivity of about 4% without an antireflection film, and even if an antireflection film is applied, the spectrum of illumination light is very wide, white, and its incident angle range is wide, so at most 0.5 to 1% The reflectance can be suppressed only to a certain extent, causing stray light.

The second cause of contrast deterioration is scattered light from the surface of DMD 11.
8 and 9 are diagrams for explaining a second cause of contrast deterioration in the asymmetric optical system. The illumination beam bundle for the DMD 11 is as shown by the arrows in FIG. That is, assuming that the normal to the chip substrate of the DMD 11 is n, the direction of −20 ° from the normal n is the optical axis Z of the irradiated light bundle, and the light beam from within an angular range of about ± 15 ° around the optical axis Z. Is incident. Here, the tilt angle of the optical axis Z is −20 °, and the switching angle of the micromirror 11B of the DMD 11 is ± 10 °. When the micromirror 11B is tilted at the tilt angle of −10 °, the reflected light is in the vertical direction. It is an angle to go. An angle value of the irradiation light bundle of about ± 15 ° corresponds to a projection lens having an F value of 2.0.

  Here, a case where all the micromirrors 11B are inclined in the + 10 ° direction and are in the OFF state is considered. Most of the reflected light Coff with respect to the illumination light as shown in FIG. 2 falls within a range of ± 15 ° with respect to the + 40 ° direction that is the reflection direction in the OFF state.

  However, as shown in FIG. 9, there are not a few rays Cx that are deflected to other angles by scattering or diffraction, and in particular, there are many components that are deflected in the direction of regular reflection with respect to the chip substrate of the DMD 11. As a cause of this, a component reflected from the bottom surface of the micromirror 11B and a reflection component from a column existing in the center of the micromirror 11B can be considered.

  Anyway, among the light rays that are specularly reflected with respect to the chip substrate of the DMD 11, when there is a light ray that is incident within −15 ° from the normal line n, the specular reflection direction is the aperture of the projection lens of F / 2.0 (see FIG. 9 passes through the shaded area indicated by the symbol R in FIG. 9 and becomes stray light. This is the second cause of contrast deterioration. FIG. 10 is a diagram showing the reflection of light rays incident on the DMD 11 from a direction of −10 ° with respect to the normal line n in FIGS. The regular reflection light Cr is in the + 10 ° direction and falls within the expected angle range R of the projection lens of F / 1.7.

  Due to the presence of the specular reflection component due to the above two origins, the angular distribution of stray light entering the expected angle range R of the projection lens is not uniform, and is often in a region where the + angle from the normal n is large. FIG. 11 is a diagram showing an example of the light quantity distribution of stray light entering the expected angle range R of the projection lens. In FIG. 11 (a), the dark and light portions represent regions where the intensity of light is strong, and the vignetting of the light beam by the deformed stop 7 provided on the Fourier transform plane of the relay system is not shown in FIG.

  In DLP, it is common to use a high-pressure mercury lamp with a parabolic reflector. In this case, the intensity distribution with respect to the angle has a weak light intensity in the vicinity of 0 ° in the center, and often has a donut-shaped angle distribution having a peak intensity around it, for example, in the vicinity of 3 ° (cross section AA in FIG. 'See intensity distribution). FIG. 12 is a diagram schematically showing the angle distribution of the reflected light from the ON-state micromirror 11B illuminated with the light of the donut-shaped angle distribution, and the 15 ° perfect circle indicated by the symbol LEN is F / 2.0. Represents a projection lens. Since the shaded portion DEL in FIG. 12 has a light intensity distribution in the regular reflection direction, it represents an angular region where the light enters the entrance pupil of the projection lens.

  Therefore, if a deformed stop 12B that prevents light rays in the angle region of the shaded portion DEL is provided in the projection lens 12 of FIG. 1, stray light due to regular reflection can be reduced, and there is a higher contrast with clearer and brighter contrast. An image can be displayed. FIG. 13 is a view showing an example of a modified diaphragm 12B provided in the projection lens 12. As shown in FIG. The same reference numerals as those in FIG. The deformed stop 12B has a Fourier transform surface 12A (position information on the reflection surface of the DMD 11 reflected by the micromirror 11B in the ON state and the DMD 11 generated by the incident side lens group in the projection lens 12 provided on the TIR prism side. The surface is converted into divergence angle information formed by the optical axis of The light that has passed through the deformed stop 12B passes through the exit side lens group in the projection lens 12 on the screen 13 side and is projected onto the screen 13. In FIG. 13, the right side of the deformation stop 12B is cut in a straight line, but it does not have to be a straight line.

  If the angle area to be scraped off by the deformed stop 12B increases, the stray light component due to specular reflection is removed and the contrast increases. However, if the shaving is excessively cut, the brightness of the ON light is also reduced. Therefore, it is preferable to determine the shape of the deformed stop 12B so as to remove the stray light component due to regular reflection within a range in which the decrease in brightness is allowable.

  As described above, according to the first embodiment, the Fourier transform surface obtained by converting the position information on the reflecting surface of the DMD 11 into the spread angle information formed by the light beam reflected by the micromirror 11B in the ON state and the optical axis of the DMD 11. An entrance-side lens group that creates 12A, a deformed stop 12B that is disposed in the vicinity of the Fourier transform plane 12A, and that shields and removes rays other than the reflected light from the micromirror 11B in the ON state according to spread angle information, and a deformed stop 12B Since the projection lens is provided with the exit side lens group that emits the transmitted light to the screen 13, the stray light due to the specular reflection component can be reduced, and an image with clearer and clearer and higher contrast can be displayed. Is obtained.

  Further, according to the first embodiment, the incident end face size w of the rod integrator 5 that receives the light flux of F1 = 1 is set to ½ times the reflection face size W of the DMD 11, and the outgoing light flux of the rod integrator 5 is set. The partial light flux 24Z that generates the interference component 21 is collectively shielded and removed by the deformed diaphragm 7 having the D-shaped opening, and the position information of the first lens group 6 is Fourier-transformed into divergence angle information. Since the asymmetric light beam 24 is generated by the second lens group 9 and applied to the DMD 11, the brightness of the optical system can be improved without restricting the F value of the incident light beam by the tilt angle of the DMD 11. The effect is obtained.

Embodiment 2. FIG.
In the first embodiment, an example using an asymmetric light beam obtained by shielding and removing a light beam that becomes an interference component has been described. In the second embodiment, a light beam having an elliptical cross-sectional shape will be described.

  FIG. 14 is a diagram showing a configuration of an image display apparatus using a condensing optical system according to Embodiment 2 of the present invention. In FIG. 14, the z-axis is set in the direction of the optical axis 14, and the x-axis (first coordinate axis) and the y-axis (second coordinate axis) are set perpendicularly to the z-axis, respectively, and FIG. FIG. 14B is a cross-sectional view in the yz plane, and FIG. 14B is a cross-sectional view in the yz plane. The same or corresponding components as those in FIG. 1 are denoted by the same reference numerals.

  In FIG. 14, reference numerals 25 and 26 denote cylindrical lenses (a condensing optical system, a light converting unit, and a cylindrical lens group) provided between the lamp light source and the condensing lens 3, respectively. The cylindrical lenses 25 and 26 have a lens action only in the x-axis direction. The cylindrical lens 25 functions as a positive lens and the cylindrical lens 26 functions as a negative lens. In the x-axis direction of FIG. 14A, the parallel light from the lamp light source is converted into parallel light having a width Ax through the cylindrical lenses 25 and 26.

  On the other hand, in the y-axis direction of FIG. 14B, since the cylindrical lenses 25 and 26 do not have a lens action, the parallel light having the width Ay from the parabolic reflector 2 passes through the cylindrical lenses 25 and 26 in parallel as they are. .

  At this time, if the lens action of the cylindrical lenses 25 and 26 is designed so that the ratio of Ax: Ay = 2: 3, the parallel light having the widths Ax and Ay transmitted through the condenser lens 3 is x The light is condensed with an expansion angle of 20 ° in the axial direction and a expansion angle of 30 ° in the y-axis direction.

  Thus, on the incident end face side of the rod integrator 5, by generating light beams having different angular distributions in two orthogonal x and y axis directions, an incident light beam having an elliptical angular distribution is generated. .

  When the vertical and horizontal axis sizes of the output end surface of the rod integrator 5 are Wx / 2 and Wy / 2 (Wx and Wy are the vertical axis size of the DMD 11 and the reflection surface size in the horizontal axis direction), respectively, the x and y axis directions Are respectively emitted from the rod integrator 5, and light beams having angular distributions of 10 ° and 15 ° in the x and y axis directions are incident on the DMD 11. At this time, the light beam to the DMD 11 becomes an incident light beam 27 having an elliptical cross-sectional shape of FIG. 14C having 3 major axes in the y-axis direction and 2 minor axes in the x-axis direction.

  As in the first embodiment, the principal ray of the outgoing light beam 28 reflected from the incident light beam 27 by the micromirror of the DMD 11 is emitted in the normal direction of the reflecting surface of the DMD 11, and the principal ray of the light beam 27 with respect to this normal direction. Is incident on the micromirror so that the rotation axis of the micromirror and the major axis (y-axis) of the incident light beam 27 and the outgoing light beam 28 are parallel to each other at an angle of 20 °. As shown in FIG. 3, it is possible to prevent an interference component between the incident light beam 27 and the outgoing light beam 28, and the incident light beam 27 and the outgoing light beam are compared with the conventional light beams 107 and 108 having a perfect circular cross section. Since the sectional area of 28 is larger, the effect that the illumination efficiency can be improved is obtained.

  The elliptical cross-sectional shapes of the incident light beam 27 and the outgoing light beam 28 are determined according to the light receiving ability 29 of the projection lens 9. The number of cylindrical lenses 25 and 26 is not particularly limited.

In addition to the configuration shown in FIG. 14, a light beam having an elliptical cross-sectional shape can be generated.
FIG. 15 is a diagram showing a configuration of an image display apparatus using a condensing optical system according to Embodiment 2 of the present invention. FIG. 15 (a) is a side view (xz plane), and FIG. 15 (b). Is a top view (yz plane). The same or corresponding components as those in FIG. 1 are denoted by the same reference numerals, and the components subsequent to the rod integrator are not shown.

  In FIG. 15, reference numeral 30 denotes a prism (a condensing optical system system, a light converting unit) provided between the lamp light source and the condensing lens 3. In the xz plane of FIG. 15A, parallel light from a lamp light source composed of the light emitter 1 and the parabolic reflector 2 is refracted obliquely with respect to the optical axis 14, and this parallel light is reflected by the prism 30 on the optical axis. 14 and parallel. The width in the x-axis direction of the parallel light emitted from the prism 30 becomes Ax and enters the condenser lens 3, and is not emitted from the condenser lens 3 as a light flux having a divergence angle of 20 ° with the optical axis 14 in the x-axis direction. It enters the rod integrator shown.

  On the other hand, in the yz plane of FIG. 15B, the parallel light from the lamp light source passes through the prism 30 while maintaining the width Ay in the y-axis direction, and the spread angle formed with the optical axis 14 is 30 °. The light enters the rod integrator 5 (not shown) from the condenser lens 3 as a light beam. As in FIG. 14, the prism 30 is designed so that Ax: Ay = 2: 3. Therefore, the following operations are the same as those of the cylindrical lenses 25 and 26.

  In this way, by using the prism 30, as in the case of FIG. 5, light beams having different angular distributions in the x and y axis directions are incident on the rod integrator. There is an effect that the brightness of the optical system can be improved without generating a component.

  FIG. 16 is a diagram showing a configuration of an image display device using a condensing optical system according to Embodiment 2 of the present invention, in which FIG. 16 (a) is a side view (xz plane) and FIG. 16 (b). Is a top view (yz plane). The same or corresponding components as those in FIG. 1 are denoted by the same reference numerals, and the components subsequent to the rod integrator are not shown.

  In FIG. 16, reference numeral 31 denotes an aperture plate (a condensing optical system system, light conversion means) that limits the aperture of the parabolic reflector 2. The aperture plate 31 emits parallel light having a width Ay from the aperture plate 31 in the yz plane of FIG. 16B, and in the x-axis direction by the aperture plate 31 having a width Ax in the xz plane of FIG. The parallel light is emitted to the condenser lens 3 by limiting the width of the light to Ax. Also in this case, Ax: Ay = 2: 3. Thus, the parallel light emitted from the aperture plate 31 has a spread angle in the x-axis direction formed with the optical axis 14 in accordance with the parallel light width Ax in the x-axis direction and the parallel light width Ay in the y-axis direction. The light is incident on a rod integrator (not shown) from the condenser lens 3 as a light beam having a 20 ° spread angle in the y-axis direction formed by the optical axis 14 and 30 °.

  Even in this case, similarly to FIG. 14 and FIG. 15, since light beams having different angular distributions in the x and y axis directions are incident on the rod integrator, a light beam having an elliptical cross section is generated to generate an interference component. Thus, the effect of improving the brightness of the optical system can be obtained.

  The cylindrical lenses 25 and 26 shown in FIG. 14 and the prism 30 shown in FIG. 15 transmit all the parallel light from the lamp light source and can be used without waste of the parallel light.

  In addition, compared to the cylindrical lenses 25 and 26 in FIG. 14 and the prism 30 in FIG. 15, the aperture plate 31 in FIG. 16 has a simple configuration and can more easily generate a light beam having an elliptical cross section.

  Further, the aperture plate 31 of FIG. 16 is configured to transmit light in a wide angle region from 20 ° to 30 ° from the light emitter 1 blocked by the back surface of the aperture plate 31 facing the parabolic reflector. Since the light reflected from the reflector 2 is reflected a plurality of times and light in a narrow region having a spread angle of 20 ° or less is emitted from the aperture plate 31, the efficiency of the lamp light source can be improved.

  Similarly to the first embodiment, stray light is generated by the TIR prism or DMD even when each of the asymmetric optical systems shown in FIGS. 14 to 16 is used. Therefore, the deformed stop 12B as shown in FIG. (See FIG. 14), the contrast can be improved.

Embodiment 3 FIG.
The modified diaphragm (first modified diaphragm) 12B provided in the projection lens 12 of the first and second embodiments is formed in a D shape. In the third embodiment, the D-shape of the modified diaphragm 12B, that is, the directionality of the opening of the modified diaphragm 12B will be described first.
17 and 18 are diagrams for explaining a substantially D-shape of the deformed diaphragm, and the same reference numerals as those in FIGS. 1 and 12 correspond to the corresponding configurations. The optical axis direction of the reflected beam bundle of the micromirror on the DMD reflecting surface in the ON state is the origin of the angle space, and the optical axis direction of the reflected beam bundle in the OFF state of the micromirror on the DMD reflecting surface is orthogonal to the θx direction and the θx direction. The direction is defined as the θy direction. At this time, the deformed stop 12B in the projection lens 12 has a substantially D shape that shields and removes a light beam having an angle equal to or larger than θc in the θx direction from the optical axis in the ON state. A hatched portion DEL in FIG. 18 represents an angle region that is shielded and removed by the substantially D-shaped deformed diaphragm 12B shown in FIG. 17, where θc = 10 °.

Embodiment 4 FIG.
In addition to the case of the third embodiment, a more preferable substantially D-shape of the in-projection lens deformation stop (first deformation stop) will be described below. The switching angle (deflection angle) between the ON state and the OFF state of the micromirror on the DMD reflecting surface is ± θDMD, and the angle at which transmission is allowed by the deformation aperture of the projection lens is θp (that is, the F value of the projection lens is Fp). When θp = Arctan (0.5 / Fp), the deformed diaphragm satisfies 0.5θDMD ≦ θc ≦ θp.

  Assuming that Fp = 2 and θDMD = 10 °, θp = 14 ° and 0.5θDMD = 5 °. Therefore, the lower limit value θc of the θx direction angle cut by the substantially D-shaped deformed diaphragm is 5 That is, ° ≦ θc ≦ 14 °.

Specifically, in the case of Fp = 2, θDMD = 10 °, when the value of θc is lowered, an example of calculating the decrease amount of ON light brightness and the decrease amount of OFF stray light amount is as follows. It shows in FIG.
FIG. 19 is a diagram showing how the brightness is reduced by the D-shaped deformed diaphragm in the projection lens. As already shown in FIG. 11, since there is an intensity distribution in the angle region, the decrease in the OFF stray light amount (broken line) is more rapid than the decrease in the brightness of the ON light (solid line). I understand. Therefore, when the light blocking area of the deformed diaphragm is expanded (when θc is increased), it is expected that the contrast will be increased or improved by reducing the amount of stray light. An example of calculating the contrast is shown in FIG.

  FIG. 20 is a diagram showing how the contrast is increased by the D-shaped deformed diaphragm in the projection lens, and also shows the amount of ON light. From FIG. 20, it can be seen that when the angle θc is about 5 ° to 14 °, the brightness of the ON light (solid line) decreases slightly and the increase in contrast (dashed line) is large. Further, since the contrast is maximized in the vicinity of θc = 10 °, it can be seen from FIG. 20 that θc≈θDMD = 10 ° is more desirable.

Embodiment 5. FIG.
When the light beam having the elliptical cross-sectional shape of the second embodiment is used, as shown in FIG. 21, the angular distribution of the ON light beam passing through the projection lens pupil is in the ON state on both sides of the −θx direction and the + θx direction. There is a region through which the light does not pass. It is more desirable to remove such an angular region that does not contribute to image display by removing the stray light as much as possible by using the deformation stop (first deformation stop) in the projection lens. In this case, in order to remove the angle regions DEL and DEL ′ in FIG. 21, the aperture of the deformed diaphragm has a substantially oval shape. The consideration for removing the specularly reflected light is the same as described above.

It is a figure which shows the structure of the image display apparatus using the condensing optical system system by Embodiment 1 of this invention. It is a figure showing the state in which the cone-shaped light beam of F2 = 2 injects into the micromirror of an ON state. It is a figure for demonstrating the function of a 1st lens group and a 2nd lens group. It is a figure which shows the cross-sectional shape of the emitted light beam from a rod integrator, a deformation | transformation aperture_diaphragm | restriction, and an asymmetrical light beam. It is a figure for demonstrating the effect | action of a deformation | transformation aperture_diaphragm | restriction. It is a figure showing the state in which an asymmetrical light beam injects into the micromirror of an ON state. It is a figure for demonstrating the 1st cause of the contrast deterioration in an asymmetrical optical system. It is a figure for demonstrating the 2nd cause of the contrast deterioration in an asymmetrical optical system. It is a figure for demonstrating the 2nd cause of the contrast deterioration in an asymmetrical optical system. FIG. 10 is a diagram showing a way of reflection of light rays incident on the DMD from a direction of −10 ° with respect to the normal line of FIGS. 8 and 9. It is a figure which shows an example of the light quantity distribution of the stray light which enters into the prospective angle range of a projection lens. It is a figure which shows typically the angle distribution of the reflected light by the micromirror of the ON state which illuminated the light of the donut-shaped angle distribution. It is a figure which shows an example of the deformation | transformation stop provided in the projection lens. It is a figure which shows the structure of the image display apparatus using the condensing optical system system by Embodiment 2 of this invention. It is a figure which shows the structure of the image display apparatus using the condensing optical system system by Embodiment 2 of this invention. It is a figure which shows the structure of the image display apparatus using the condensing optical system system by Embodiment 2 of this invention. It is a figure for demonstrating the substantially D-shape of a deformation | transformation aperture_diaphragm | restriction. It is a figure for demonstrating the substantially D-shape of a deformation | transformation aperture_diaphragm | restriction. It is a figure which shows the mode of the brightness | luminance reduction by the D-shaped deformation | transformation aperture_diaphragm | restriction in a projection lens. It is a figure which shows the mode of the increase in contrast by the D-shaped deformation | transformation aperture_diaphragm | restriction in a projection lens. It is a figure for demonstrating the substantially D-shape of a deformation | transformation aperture_diaphragm | restriction. It is the figure which expanded a part of reflective surface of DMD. It is a figure for demonstrating the operation | movement of the inclination control of a micromirror. It is a figure showing the state which the conical light beam of F = 3 injects into the micro mirror of an ON state. It is a figure which shows the structure of the image display apparatus using the conventional condensing optical system system. It is a figure for demonstrating the relationship between a rod integrator and DMD. It is a figure for demonstrating the condensing distribution with respect to a rod integrator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Light-emitting body, 2 Parabolic reflector, 3 Condensing lens, 4 Color wheel, 5 Rod integrator, 6 1st lens group, 7 Deformation diaphragm, 7Z shielding part, 8 Folding mirror, 9 2nd lens group, 10 TIR prism, 10A DMD opposing surface, 11 digital micromirror device, 11A cover glass, 11B, 16 micromirror, 12 projection lens, 12A Fourier transform surface, 12B modified aperture, 13 screen, 14 optical axis, 15 DMD reflecting surface, 17 incident principal ray, 18 incident light beam, 18A, 18B, 18C incident light beam, 19 outgoing main light beam, 20 outgoing light beam, 20A, 20B, 20C outgoing light beam, 21 interference component, 22A, 22B plane, 23 light beam, 24 asymmetric light beam, 24Z partial light beam, 25 , 26 Cylindrical lens, 30 Rhythm, 31 aperture plate, n, nA normal.

Claims (10)

A condensing optical system that collects light; and
A condensing lens that condenses the light emitted from the lamp light source as a first F-number light beam, and a light intensity distribution uniformizing element that emits the first F-value light beam with a uniform intensity distribution on its exit end face A relay system that relays the first F-number light beam as the second F-value light beam to the reflective spatial light modulator;
A screen for displaying an image, a reflective light spatial modulation element that reflects light by switching an ON / OFF state of a micromirror, and a projection optical system that projects light reflected by the reflective light spatial modulation element onto the screen In an image display device that irradiates the light from the condensing optical system to the reflective spatial light modulator,
In the projection optical system, position information on the reflection surface of the reflective spatial light modulator is converted to spread angle information formed by the light beam reflected by the micromirror in the ON state and the optical axis of the reflective spatial light modulator. An incident-side lens group that creates a transformed Fourier transform surface, and a first deformed diaphragm that is disposed in the vicinity of the Fourier transform surface and shields and removes light rays other than the reflected light from the micromirror in the ON state according to spread angle information And an exit side lens group for emitting the light transmitted through the first deformed stop to the screen,
The condensing optical system sets a width in a first coordinate axis direction orthogonal to the optical axis of the condensing lens based on an F value determined by an inclination angle of the reflective spatial light modulator, and the condensing lens A light conversion means for emitting the light beam in the second coordinate axis direction orthogonal to the optical axis and the first coordinate axis larger than the light width in the first coordinate axis direction, and the lamp light source. In preparation for the condenser lens,
The relay system relays the light flux with the rotation axis of the reflective spatial light modulator and the second coordinate axis direction parallel to each other.   2. The image display device according to claim 1, wherein the light converting means is a cylindrical lens group having an optical axis that coincides with the optical axis of the condenser lens and having a lens function only in the first coordinate axis direction.   The light converting means is a prism that refracts light from the lamp light source emitted obliquely with respect to the optical axis of the condenser lens in a direction parallel to the optical axis of the condenser lens only in the first coordinate axis direction. The image display device according to claim 1. The lamp light source is composed of a light emitter that emits light and a parabolic reflector provided with the light emitter at a focal point,
2. The image display device according to claim 1, wherein the light conversion means is an aperture plate provided at an aperture of the parabolic reflector.   When the optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, and the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, the first deformation stop is 2. The image display apparatus according to claim 1, further comprising a substantially D-shaped opening for shielding and removing a light beam having an angle of θc or more in the θx direction from the optical axis in the ON state.   When the switching angle between the ON state and the OFF state of the micromirror is ± θDMD and the angle at which transmission is allowed by the first deformation aperture is θp, the first deformation aperture is 0.5θDMD ≦ The image display device according to claim 5, further comprising an opening that satisfies θc ≦ θp.   7. The image display device according to claim 5, wherein the first deformed diaphragm has an opening that satisfies θc≈θDMD.   The optical axis direction of the reflected light bundle of the micromirror in the ON state is the origin of the angle space, the optical axis direction of the reflected light bundle of the micromirror in the OFF state is the θx direction, and the direction orthogonal to the θx direction is θy. When determining the direction, the first deformed aperture has a substantially oval opening that shields and removes light having an angle of ± θc ′ or more in the ± θx direction from the optical axis in the ON state. The image display device according to any one of claims 1 to 4.   When the switching angle between the ON state and the OFF state of the micromirror on the reflective spatial light modulation element surface is ± θDMD, and the angle at which transmission is allowed by the first deformation stop is θp, the first deformation is performed. The image display apparatus according to claim 8, wherein the diaphragm has an opening that satisfies 0.5θDMD ≦ θc ′ ≦ θp.   10. The image display device according to claim 8, wherein the first deformation stop has an opening that satisfies θc′≈θDMD.

Images