JP2012141574A - Polarization convertible relay optical system and image projection device provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization convertible relay optical system capable of reducing degradation of imaging performance associated with polarization separation in a polarization convertible optical system, and an image projection device provided therewith.SOLUTION: A polarization convertible relay optical system 52 that is arranged between a projection lens system 51 and a DMD 4, performs conversion into linearly polarized light with one polarization direction and forms an intermediate image M from an image displayed on the DMD 4 comprises: a front group lens system 53; a rear group lens system 54; and a polarization convertible optical system 55 that is arranged on a pupil surface P. The polarization convertible optical system 55 includes: a PBS prism array 56 for separating light from multiple light source images into two forms of linearly polarized light with different polarization directions; and a phase plate 57 for emitting the two forms of linearly polarized light after converting them into one form of linearly polarized light with one polarization direction. In all beams of light focused within an effective image domain, the front group lens system 53 satisfies a conditional expression of (1) Δf<40×k×p, and the rear group lens system 54 satisfies a conditional expression of (2) Δr<40×p.

Description

  The present invention relates to a polarization conversion relay optical system used in an image projection apparatus that projects an image displayed on a display element onto a projection surface, and an image projection apparatus including the polarization conversion relay optical system.

  In a projector that projects an image displayed on a display element onto a projection surface such as a screen, a projector using a digital micromirror device (hereinafter referred to as DMD) as a display element has been put into practical use because of its high switching speed. ing. Recently, a movie that can be viewed as a stereoscopic image (hereinafter referred to as a 3D image) has been produced, and a movie theater for viewing the movie has begun to be created. Also, a projection television for home use that supports 3D images has been released. It is coming. A projector using DMD displays a right-eye image and a left-eye image in a time-sharing manner, and a viewer can view a 3D image by wearing polarized glasses or shutter glasses. Therefore, the projector is used as a 3D projector. Yes.

  Since any of the above glasses transmits circularly polarized light or linearly polarized light and guides it to the left and right eyes of the viewer, when an image is projected with random polarization by a projector using a DMD, more than half of the glasses are used. The amount of light will be lost. For this reason, it is desired to obtain a projection image using light having a uniform polarization direction. In this respect, for example, in the projector disclosed in Patent Document 1, a polarization conversion optical system is disposed in the vicinity of the pupil position of the relay optical system in the projection optical system, and the light from the display element is converted into two linearly polarized light by the polarization conversion optical system. After the separation, one light is converted into light having the same polarization direction as the other, and an image of the display element is projected.

WO 2008/141247

  However, in the above-described prior art, the light beam before passing through the polarization conversion optical system and the light beam after passing through the polarization conversion optical system are separated into two linearly polarized lights by the polarization conversion optical system and pass through different optical paths. Produces rays decentered parallel to each other. Usually, an aberration proportional to the square of the pupil diameter, such as coma aberration, acts on the entire optical system so as to cancel the aberration of each lens group, so that the front group lens system and the rear group lens sandwiching the pupil position Also in the system, the front group lens system and the rear group lens system cancel each other's coma aberration, and the coma aberration can be suppressed as a relay optical system. However, in the relay optical system in which the polarization conversion optical system is arranged in the vicinity of the pupil position, the front group lens system and the rear group lens system are decentered due to the polarization conversion optical system. Is decentered, the front group lens system and the rear group lens system do not cancel each other's coma aberration, so that coma appears remarkably and image formation performance deteriorates.

  The present invention has been made in order to solve the above-described problems, and a polarization conversion relay optical system capable of suppressing deterioration in imaging performance due to polarization separation of the polarization conversion optical system and an image including the same An object is to provide a projection device.

The polarization conversion relay optical system of the present invention includes a display element composed of a digital micromirror device that displays an image by rotating a mirror that constitutes each pixel, and an integrator optical system that forms a plurality of light source images from light from the light source And an illumination optical system that guides light from the light source to the display element, and a projection lens system that projects an image of the display element onto a projection surface. A polarization conversion relay optical system that is disposed between the display element and forms an intermediate image of a display image of the display element in a state in which the polarization direction is aligned in one direction, the polarization conversion relay optical system comprising: A front group lens system disposed on the intermediate image side, a rear group lens system disposed on the display element side with respect to the pupil plane, and a polarization conversion optical system disposed on the pupil plane, The polarization conversion optical system An effective image having a polarization separating element that separates light from the plurality of light source images into two linearly polarized light having different polarization directions and a phase plate that emits the two linearly polarized light in a single polarization direction. In all the light bundles condensed in the region, the front group lens system satisfies the following conditional expression (1), and the rear group lens system satisfies the following conditional expression (2).
Δf <40 × k × p (1)
Δr <40 × p (2)
However,
Δf: a ray passing through the center of the pupil plane from an intermediate point between the coordinates of the ray passing through the upper end of the pupil plane and the coordinate of the ray passing through the lower end of the pupil plane in the image plane of the front group lens system The absolute value Δr of the coma aberration amount defined as the distance to the coordinates of: The coordinates of the light ray passing through the upper end of the pupil plane and the coordinates of the light ray passing through the lower end of the pupil plane in the image plane of the rear lens group system The absolute value of the coma aberration amount defined as the distance from the intermediate point to the coordinates of the light ray passing through the center of the pupil plane k: the magnification of the polarization conversion relay optical system p: the pixel pitch of the display element

In the polarization conversion relay optical system of the present invention, it is preferable that the front group lens system satisfies the following conditional expression (1A), and the rear group lens system satisfies the following conditional expression (2A).
Δf <20 × k × p (1A)
Δr <20 × p (2A)

In the polarization conversion relay optical system of the present invention, it is preferable that the front group lens system satisfies the following conditional expression (1B), and the rear group lens system satisfies the following conditional expression (2B).
Δf <k × p (1B)
Δr <p (2B)

  In the polarization conversion relay optical system of the present invention, it is desirable that the front group lens system and the rear group lens system are arranged symmetrically with respect to the pupil plane.

  In the polarization conversion relay optical system according to the aspect of the invention, it is preferable that the rear group lens system converts a light beam emitted from a position of the display element corresponding to the optical axis of the rear group lens system into parallel light on the pupil side.

  The image projection apparatus includes the polarization conversion relay optical system.

  In the image projection apparatus of the present invention, it is preferable that the light source is a laser beam.

  In the image projection apparatus according to the aspect of the invention, it is preferable that the image projection apparatus further includes a polarization switching element that alternately switches the light emitted from the polarization conversion optical system into two types of polarized light.

  According to the present invention, when the front group lens system satisfies the conditional expression (1), the maximum coma aberration amount of the front group lens system can be suppressed to 40 times or less of the pixel pitch of the display element. Further, when the rear group lens system satisfies the conditional expression (2), the maximum coma aberration amount of the rear group lens system can be suppressed to 40 times or less of the pixel pitch of the display element. As described above, when the maximum coma aberration amount in each of the front group lens system and the rear group lens system is suppressed to 40 times or less of the pixel pitch of the display element, the front group lens system and the rear group are caused by the polarization conversion optical system. Even if the lens system is decentered, the coma aberration amount of the polarization conversion relay optical system can be suppressed to approximately one pixel or less of the display element, and good imaging performance can be obtained.

Sectional drawing which shows schematic structure of the image projector which concerns on one Embodiment of this invention Plan view of DMD of the image projection apparatus Sectional view of polarization conversion optical system of image projection apparatus Sectional drawing of the polarization conversion relay optical system which concerns on one Embodiment of this invention The figure which shows the coma aberration of the said polarization conversion relay optical system and a front group lens system (rear group lens system) Sectional view of the front group lens system (rear group lens system) of the polarization conversion relay optical system The figure explaining the amount of coma of the front group lens system (rear group lens system) The figure which shows the correlation of the coma aberration of the said polarization conversion relay optical system and a front group lens system (rear group lens system) Sectional drawing which shows the modification of the said polarization conversion optical system Sectional drawing which shows another modification of the said polarization conversion optical system Sectional drawing which shows another modification of the said polarization conversion optical system Sectional drawing which shows the structure of the image projector which concerns on another embodiment of this invention. Sectional view of the color prism of the image projection apparatus Aberration diagram of the front group lens system (rear group lens system) of Example 1 relating to the polarization conversion relay optical system Aberration diagram in the case where there is decentration of Example 1 related to the polarization conversion relay optical system. Aberration diagram in the case where there is no decentration of the first embodiment related to the polarization conversion relay optical system Aberration diagram of the front group lens system (rear group lens system) of Example 2 according to the polarization conversion relay optical system. Aberration diagram in the case where there is decentration of Example 2 related to the polarization conversion relay optical system. Aberration diagram in the case where there is no decentration of Example 2 according to the polarization conversion relay optical system. Aberration diagram of the front group lens system (rear group lens system) of Example 3 according to the polarization conversion relay optical system. Aberration diagram in the case where there is decentration of Example 3 related to the polarization conversion relay optical system Aberration diagram in the case where there is no decentration of the third embodiment according to the polarization conversion relay optical system

  Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Further, the use of the invention and the terms shown here are not limited thereto.

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of an image projection apparatus according to the present embodiment. The image projection apparatus 100 includes a light source 1, an illumination optical system 2, a TIR prism 3, a DMD 4, and a projection optical system 5. The long side direction of the rod integrator 22 is actually in a twisted relationship inclined by 45 degrees with respect to an incident surface described later of the TIR prism 3, but in FIG. The plane and the polarization separation direction are shown in the same plane.

  In the above configuration, the light emitted from the light source 1 enters the TIR prism 3 through the illumination optical system 2, is totally reflected there, and then enters the DMD 4. The light that has entered the DMD 4 is modulated there, then emitted as image light, transmitted through the TIR prism 3, and guided through the projection optical system 5 to a screen (not shown) that is a projection surface. The projection optical system 5 enlarges and projects the image displayed on the DMD 4 on the screen. The projected surface may be a wall.

  In the case of projecting a 3D image, image light obtained by sequentially time-dividing a right-eye image and a left-eye image by the DMD 4 is converted into random polarized light by a polarization conversion optical system 55 (to be described later) of the projection optical system 5 into linearly polarized light. Convert and project on screen. In this case, the viewer can appreciate the 3D image by viewing the projected image through shutter glasses that alternately transmit linearly polarized light in synchronism with the timing of time-division display. Details of each component will be described below.

  Incidentally, when the central ray of the light bundle directed from the light source 1 toward the center of the rectangular image display area of the DMD 4 is incident on an arbitrary surface in the optical path, the central ray incident on the surface and the normal of the surface at the incident point And a plane including Then, linearly polarized light whose polarization direction is parallel to the incident surface is P-polarized light, and linearly polarized light whose polarization direction is perpendicular to the incident surface is S-polarized light. Further, a surface on the light incident side when light passes through the optical member is used as a light incident surface to distinguish it from the above incident surface, and a surface on the light output side is defined as a light emitting surface.

  The light source 1 emits light for illuminating the DMD 4 and includes a light emitting unit 11 and a reflector 12. The light emitting unit 11 is constituted by, for example, a discharge lamp that emits white light. The reflector 12 is a reflecting plate that reflects the light emitted from the light emitting unit 11 and guides it to the illumination optical system 2. The reflector 12 has a spheroidal reflection surface, and the light emitting unit 11 is disposed at one focal position of the reflector 12. Therefore, the light from the light emitting unit 11 is reflected by the reflector 12 and collected at the other focal position, and enters the rod integrator 22 via the color wheel 21 described later of the illumination optical system 2.

  The illumination optical system 2 is an optical system that guides light from the light source 1 to the DMD 4, and includes a color wheel 21, a rod integrator 22, and an illumination relay system 23.

  The color wheel 21 is composed of a color filter that sequentially transmits light of each color of R (red), G (green), and B (blue). By rotating the color wheel 21, it is possible to illuminate the DMD 4 by sequentially switching the color light to illuminate. Therefore, by displaying image information corresponding to each color on the DMD 4, the projected image can be colored.

  The rod integrator 22 emits light with a uniform light quantity distribution from the light source 1. The cross-sectional shape of the rod integrator 22 is substantially similar to the rectangular image display area of the DMD 4. Thus, the rod integrator 22 constitutes an integrator optical system that forms an illumination light beam that is substantially similar to the rectangular image display area of the DMD 4.

  On the pupil plane of the illumination relay system 23, a plurality of light source images are formed at positions corresponding to the number of reflections in the rod integrator 22. The pupil plane of the illumination relay system 23 and the pupil plane P of the polarization conversion relay optical system 52 described later are substantially conjugate. Further, the light exit surface of the rod integrator 22 and the image display area of the DMD 4 are substantially conjugated by the illumination relay system 23.

  The illumination relay system 23 is an optical system that uniformly illuminates the DMD 4 by relaying and projecting the image of the light exit surface of the rod integrator 22 onto the DMD 4. The illumination relay system 23 includes a first lens 23a, a second lens 23b, a mirror 23c that bends the optical path by 90 degrees, and a third lens 23d. The light utilization efficiency can be improved by condensing the light from the rod integrator 22 by the illumination relay system 23.

  According to the above-described configuration of the illumination optical system 2, each color light incident on the rod integrator 22 from the light source 1 via the color wheel 21 in a time-sharing manner is repeatedly mixed by internal reflection, thereby obtaining a uniform light amount distribution. The light exits from the light exit surface. A plurality of light source images are formed in the illumination relay system 23 (the pupil plane of the illumination relay system) according to the number of reflections at the rod integrator 22, and by superimposing these, illumination light with a uniform light quantity distribution is formed. Can be realized. The light emitted from the rod integrator 22 is guided to the DMD 4 via the illumination relay system 23 and the TIR prism 3. At this time, since the cross section of the rod integrator 22 is substantially similar to the image display area of the DMD 4, light is uniformly and efficiently guided to the DMD 4. By illuminating the DMD 4 with light having a uniform light amount distribution, unevenness in light amount (luminance unevenness) in the projected image can be eliminated.

  The TIR prism 3 is a total reflection prism (critical angle prism) that totally reflects illumination light to the DMD 4 and transmits image light (projection light) from the DMD 4. By bending the optical path of the illumination light by the TIR prism 3, the image projector 100 can be configured compactly.

  The TIR prism 3 is configured by bonding two prisms 31 and 32 through an air gap layer. The prism 31 has a first light incident surface 31a, a critical surface 31b, and a first light emitting surface 31c, and the prism 32 has a second light incident surface 32a and a second light emitting surface 32b. The critical surface 31b of the prism 31 and the second light incident surface 32a of the prism 32 are arranged to face each other with an air gap layer interposed therebetween.

  The illumination light from the illumination optical system 2 enters the prism 31 of the TIR prism 3 from the first light incident surface 31a. The critical surface 31b of the prism 31 is arranged so that the illumination light is totally reflected. The illumination light is reflected by the critical surface 31b and emitted from the first light emission surface 31c of the prism 31 to illuminate the DMD 4.

  Of the reflected light from the DMD 4, the on-light again enters the projection optical system 5 through the TIR prism 3 and is guided to the screen. More specifically, the light beam (projection light) reflected by each pixel (mirror) in the image display state of the DMD 4 enters the prism 31 again from the first light exit surface 31c of the prism 31 and reaches the critical surface 31b. . At this time, since the projection light is incident on the critical surface 31b at an angle that does not satisfy the total reflection condition, it passes through the critical surface 31b, enters the prism 32 from the second light incident surface 32a through the air gap layer. Then, the light is guided to the screen via the second light emitting surface 32 b and the projection optical system 5.

The DMD 4 is a digital micromirror device (manufactured by Texas Instruments, USA) having a plurality of micromirrors corresponding to each pixel in a matrix, and is a display element that modulates incident light and displays an image. Here, FIG. 2 is a plan view of the DMD 4. DMD4 has a rectangular image display area 4a, rotation shaft 4c of the mirror 4b constituting each pixel has an angle of the long side 4a ₁ and the short side 4a ₂ and 45 degrees of the image display area 4a.

  Each mirror 4b of the DMD 4 reflects the illumination light in a state tilted by 12 degrees toward the illumination optical axis, thereby emitting on-light as projection light in a direction perpendicular to the image display area 4a of the DMD 4. On the other hand, off-light is emitted with an emission angle of 48 degrees by reflecting the illumination light with each mirror 4b tilted by 12 degrees in the opposite direction. The on-light is guided to the screen through the TIR prism 3 and the projection optical system 5 in order, but the off-light is emitted from the mirror 4b at a large emission angle, and thus does not enter the projection optical system 5 and enters the screen. Will not reach. In this way, by controlling the inclination of each mirror 4b with the binary value of ON / OFF, an image can be displayed on the DMD 4 and the displayed image can be projected on the screen.

  In addition, since the DMD 4 expresses ON / OFF by rotating ± 12 degrees around the axis of the rotating shaft 4c, the incident surface of the critical surface 31b and the incident surface of the mirror 4b of the DMD 4 are parallel to each other. Further, a TIR prism 3 and a DMD 4 are arranged. Due to this positional relationship, while the projection light and the illumination light are efficiently separated by the TIR prism 3, only the ON light among the light reflected by each mirror 4b of the DMD 4 is transmitted through the critical surface 31b to the screen. Can lead.

  Returning to FIG. 1, the projection optical system 5 is an optical system that projects an image of the DMD 4 on a screen, and includes a projection lens system 51 and a polarization conversion relay optical system 52.

  The polarization conversion relay optical system 52 is an optical system that forms an intermediate image M of the image of the DMD 4 in the vicinity of the projection lens system 51. The intermediate image M formed by the polarization conversion relay optical system 52 is projected on the screen by the projection lens system 51. The polarization conversion relay optical system 52 includes a front group lens system 53, a rear group lens system 54, and a polarization conversion optical system 55.

  The polarization conversion optical system 55 converts light (random polarization) from a plurality of light source images formed on the pupil plane of the illumination relay system 23 into linearly polarized light whose polarization direction is aligned in one direction and emits the light. It is. Here, FIG. 3 is a cross-sectional view of the polarization conversion optical system 55. The polarization conversion optical system 55 includes a PBS prism array 56 and a phase plate 57.

  The PBS prism array 56 is disposed on the pupil plane P (see FIG. 1) of the polarization conversion relay optical system 52, and the light from the light source image on the illumination relay system pupil plane is converted into two linearly polarized lights (P It is a polarization separation element that separates into polarized light and S-polarized light. The PBS prism array 56 is configured such that a plurality of PBS films 56a and a plurality of prisms 56b are alternately arranged. Each PBS film 56a is a strip-shaped optical thin film that transmits P-polarized light among incident light and reflects S-polarized light, and is arranged in parallel to each other at equal intervals. Each prism 56b is made of, for example, glass, and the cross-sectional shape of the prism 56b sandwiched between the two PBS films 56a is a parallelogram.

  The phase plate 57 is a phase plate that is disposed in one optical path of two linearly polarized light beams that have been polarized and separated by the PBS prism array 56. The phase plate 57 is composed of, for example, a ½ wavelength plate, and is an intermediate image of the PBS prism array 56. It is bonded to every other prism 56b so as to face every other PBS film 56a on the M side (left side in FIG. 3). The phase plate 57 converts one linearly polarized light (for example, P-polarized light) transmitted through the PBS film 56a into linearly polarized light (for example, S-polarized light) having the same polarization direction as the other.

  With the above-described configuration of the polarization conversion optical system 55, light beams of a plurality of light source images formed on the pupil plane of the illumination relay system 23 are imaged on the PBS prism array 56, and P-polarized light and S-polarized light by the PBS film 56a. And separated. Among these, the P-polarized light is transmitted through the PBS film 56a, enters the phase plate 57, and is transmitted therethrough to be converted into S-polarized light.

  On the other hand, the S-polarized light that has been polarized and separated by the PBS film 56a is reflected by the PBS film 56a, then reflected again by the adjacent PBS film 56a, and is emitted through a region where the phase plate 57 is not bonded.

  According to the configuration of the polarization conversion optical system 55, when a stereoscopically viewable image is projected, the polarization conversion optical system 55 converts random polarization into linear polarization with the polarization direction aligned in one direction. It is possible to obtain a visually bright projected image with less light loss compared to a configuration in which only linearly polarized light in a predetermined polarization direction is taken out (blocking off linearly polarized light in other polarization directions) and projected. it can.

  FIG. 4 is a cross-sectional view showing the polarization conversion relay optical system 52. The polarization conversion relay optical system 52 includes a polarization conversion optical system 55 disposed on the pupil plane P, a front group lens system 53 disposed on the intermediate image M side with respect to the pupil plane P, and the pupil plane P. And a rear group lens system 54 disposed on the DMD 4 side.

  The rear group lens system 54 is an optical system that converts light emitted from the DMD 4 into substantially parallel light on the pupil P side, and includes lenses L1 to L8 in order from the pupil plane P side to the DMD 4 side.

  The lens L1 is a biconcave lens, the lens L2 is a positive meniscus lens bonded to the lens L1, the lens L3 is a positive meniscus lens, the lens L4 is a negative meniscus lens, and the lens L5 is a biconvex lens. The lens L6 is a biconcave lens, the lens L7 is a biconvex lens, and the lens L8 is a positive meniscus lens.

  The front lens system 53 is an optical system that forms parallel light incident from the pupil plane P on the optical axis AX of the intermediate image M plane (the optical axis of the polarization conversion relay optical system 52), and from the pupil plane P side. The lenses L1 to L8 are sequentially arranged toward the intermediate image M side.

  The lenses L1 to L8 of the front group lens system 53 have the same configuration as the lenses L1 to L8 of the rear group lens system 54, respectively, and are arranged so as to have the same lens spacing as the lenses L1 to L8 of the rear group lens system 54. Has been. That is, the front lens group 53 and the rear lens system 54 are arranged symmetrically with respect to the pupil plane P.

  According to the above configuration of the front group lens system 53 and the rear group lens system 54, the lenses of the front group lens system 53 and the rear group lens system 54 can be made of the same glass material, and the polarization conversion relay optical system 52 Since the cost can be reduced and a relay optical system with the same magnification can be easily configured, the projection optical system 5 is used as an image forming apparatus with the same handling as when only the projection lens system 51 is configured. be able to.

  Further, according to the above configuration of the front group lens system 53 and the rear group lens system 54, the polarization conversion relay optical system 52 is an optical system that becomes parallel light near the pupil P. Even if a difference in optical path length or a deviation of the optical axis occurs with respect to the group lens system 54, an optical system in which the deterioration of the lens performance is extremely small can be obtained.

  Since the polarization conversion relay optical system 52 performs polarization conversion by the polarization conversion optical system 55, two linearly polarized light (P-polarized light and S-polarized light) having different polarization directions are separated on the pupil plane P. When the polarized light is separated, one polarized light (for example, S-polarized light) is reflected twice by the PBS film 56a (see FIG. 3) of the PBS prism array 56, so that the optical path with respect to the other polarized light (for example, P-polarized light). Is shifting. That is, the light beam before passing through the polarization conversion optical system 55 and the light beam after passing through the polarization conversion optical system 55 are light beams that are decentered in parallel with each other.

  Normally, even if there is a large coma aberration in the single optical system of the front group lens system 53 and the rear group lens system 54, the front group lens system 53 and the rear group lens system 54 cancel each other out of the coma aberration. As a relay optical system including the group lens system 53 and the rear group lens system 54, coma aberration can be suppressed. However, in the polarization conversion relay optical system 52 in which the polarization conversion optical system 55 is disposed in the vicinity of the pupil position, parallel decentration occurs between the front group lens system 53 and the rear group lens system 54 due to the polarization conversion optical system 55. Thus, when each lens system is decentered, the front group lens system 53 and the rear group lens system 54 do not cancel each other as described above, and the coma aberration appears remarkably. This coma will be described in detail with reference to FIGS.

  FIG. 5 is a diagram showing coma aberration of the polarization conversion relay optical system 52 and each of the front group lens system 53 and the rear group lens system 54. FIG. 6 is a cross-sectional view of the front group lens system 53 and the rear group lens system 54 of the polarization conversion relay optical system 52. The horizontal axis in FIG. 5 indicates the position of the incident light with reference to the principal ray passing through the optical axis on the pupil plane (origin 0), and the vertical axis indicates the amount of coma aberration at the position of each incident light. . Further, “front lens group coma” in FIG. 5 indicates coma on the image plane when parallel light enters from the pupil plane P of the front lens system 53 shown in FIG. The “rear group lens system coma” indicates coma aberration in the image plane when parallel light is incident from the pupil plane P of the rear group lens system 54 in FIG. 6. Further, “total optical system coma” in FIG. 5 indicates coma of a lens system (all optical system) including the front group lens system 53 and the rear group lens system 54, and “decentration system” in FIG. The coma aberration of a lens system decentered in parallel is shown.

  As shown in FIG. 5, the “front group lens system coma aberration” and the “rear group lens system coma aberration” have coma appear substantially symmetrically in opposite directions with respect to the horizontal axis including the origin 0. Therefore, in the “all-optical system coma aberration”, the front-group lens system coma aberration and the rear-group lens system coma aberration cancel each other, and the entire optical system coma aberration is suppressed.

  In the lens system (all optical systems) including the front group lens system 53 and the rear group lens system 54, for example, when the rear group lens system 54 is decentered parallel to the front group lens system 53, the “rear group” in FIG. As shown in “Lens system coma aberration (eccentric system)”, the coma aberration rotates clockwise with respect to the origin 0 with respect to the “rear group lens system coma aberration” (when there is no decentering) in FIG. So biased. For this reason, the front group lens system 53 and the rear group lens system 54 cannot cancel each other's coma aberration in the entire optical system, and as shown in “all optical system coma aberration (eccentric system)” in FIG. Large coma remains and deteriorates lens performance.

  Therefore, in the present embodiment, the amount of single coma aberration in each of the front group lens system 53 and the rear group lens system 54 is suppressed to be small. Thereby, even if parallel decentration occurs in the front group lens system 53 and the rear group lens system 54 due to the arrangement of the polarization conversion optical system 55 at the pupil position, deterioration of the lens performance is suppressed. Here, FIG. 7 is a diagram schematically showing a condensing state at an arbitrary point on the image plane I, that is, a diagram showing individual coma amounts of the front group lens system 53 and the rear group lens system 54. It is. The amount of single coma aberration is the coordinate Ah on the image plane I of the light ray A passing through the upper end of the pupil plane P (see FIG. 6) of each lens system and the pupil in the bundle of rays collected at one point on the image plane I. A light ray C (chief ray) passing through the center (on the optical axis) of the pupil plane P from the intermediate point Dh of the light ray B passing through the lower end of the surface P with the coordinate Bh on the image surface I on the image surface I. It is defined as the distance to the coordinate Ch. Here, the image plane I is a plane perpendicular to the optical axis including the point where the light bundle parallel to the optical axis incident from the pupil side of each lens system converges in the front group lens system 53 or the rear group lens system 54. is there. In this embodiment, the principal ray on the image plane side of the front group lens system 53 and the rear group lens system 54 is a telecentric optical system in which both are substantially parallel.

  When the decentering amount of one lens system in the front group lens system 53 and the rear group lens system 54 is set to 1/10 of the pupil diameter of one lens system and the pixel pitch of the DMD 4 is set to 8 μm, The correlation shown in FIG. 8 is obtained between the amount of single coma in the effective image region and the amount of coma in the effective image region of the entire optical system. Here, the effective image area is an area on the image plane I, which corresponds to the image display area of the DMD 4 in the rear group lens system 54, and the image display of the DMD 4 in the front group lens system 53. This is an area similar to the image display area of DMD 4 having an area obtained by multiplying the area by the magnification of the polarization conversion relay optical system.

  FIG. 8 is a graph showing the amount of single coma and the amount of coma in the entire optical system at the above-mentioned decentering amount. The horizontal axis shows the amount of single coma and the vertical axis shows the amount of coma in the entire optical system. . The broken line in FIG. 8 shows the correlation between the amount of single coma and the amount of coma in the entire optical system. As is apparent from this graph, when the single coma aberration amount is 300 μm or less, the coma aberration amount of the entire optical system is approximately 8 μm, and can be suppressed to about one pixel of DMD4. For this reason, in order to suppress the coma aberration amount of the entire optical system to about one pixel of DMD4, the single coma aberration amount should be contained within a coma aberration amount of approximately 37 times or less of the pixel pitch.

Accordingly, the absolute value of the single coma aberration amount of the front group lens system 53 is represented by Δf (unit: nm), the absolute value of the single coma aberration amount of the rear group lens system 54 is represented by Δr (unit: nm), and the pixel pitch of the DMD 4 P (unit: nm), and the magnification of the polarization conversion relay optical system 52 is represented by k, in all light bundles focused in the effective image area,
Δf <40 × k × p (1)
Δr <40 × p (2)
By satisfying the conditional expressions (1) and (2), even if the front lens group 53 and the rear lens system 54 are decentered due to the polarization conversion optical system 55, the polarization conversion relay optical system 52 The amount of coma aberration can be suppressed to be approximately equal to or less than the pixel pitch of DMD4, and good imaging performance can be obtained.

  Further, as shown in FIG. 8, when the amount of single coma is 200 μm or less, the amount of coma in the entire optical system is approximately 4 μm, and can be suppressed to about half of the DMD4 pixels. For this reason, in order to suppress the coma aberration amount of the entire optical system to about a half pixel of the DMD4 pixel, the single coma aberration amount should be contained within a coma aberration amount of approximately 25 times or less of the pixel pitch.

Therefore, by satisfying the following conditional expressions (1A) and (2A), even if the front group lens system 53 and the rear group lens system 54 are decentered due to the polarization conversion optical system 55, the polarization conversion relay optical system The coma aberration amount of the system 52 can be suppressed to about half a pixel or less of the DMD4 pixel, and a better imaging performance can be obtained.
Δf <20 × k × p (1A)
Δr <20 × p (2A)

Further, when the following conditional expressions (1B) and (2B) are satisfied, the single coma aberration amount is reduced to about the pixel of DMD4 (about 8 μm), and the lens performance further deteriorates due to the polarization conversion optical system 55. The image forming performance can be further suppressed and the imaging performance can be improved to the extent of an optical system without decentration.
Δf <k × p (1B)
Δr <p (2B)

  In addition, even if the polarization conversion optical system 55 is disposed as shown in FIG. 9, the present embodiment can be applied. FIG. 9 is a cross-sectional view showing a modification of the polarization conversion optical system. This polarization conversion optical system 55 has the same configuration as that of the polarization conversion optical system 55 shown in FIG. 3, but the light of the rear group lens system 54 with respect to the optical axis AX1 of the front group lens system 53 and the polarization conversion optical system 55. The axis AX2 is decentered in parallel.

  The rear group lens system 54 is parallel decentered by ½ with respect to the pitch separated into P-polarized light and S-polarized light by the polarization conversion optical system 55. When the parallel decentering amount of the rear lens group 54 is set in this way, the amount of deviation between the separated P-polarized light and S-polarized light becomes equal to the optical axis AX1. By equalizing the amount of deviation between P-polarized light and S-polarized light, the amount of deviation between P-polarized light and S-polarized light with respect to the optical axis AX1 can be halved compared to the configuration of the polarization conversion optical system 55 shown in FIG. it can. Thus, by decentering the front group lens system 53 and the rear group lens system 54 in parallel, it is possible to suppress deterioration in lens performance due to the polarization conversion optical system 55.

  Further, the polarization conversion optical system 55 may be configured as shown in FIG. FIG. 10 is a cross-sectional view showing another modification of the polarization conversion optical system. The polarization conversion optical system 55 includes a PBS prism array 56 and a phase plate 57.

  The PBS prism array 56 is disposed on the pupil plane P (see FIG. 1) of the polarization conversion relay optical system 52, and two linearly polarized lights (P-polarized light and S-polarized light) having different polarization directions are emitted from a plurality of light source images. ). The PBS prism array 56 is bonded to the prism 56d formed with the PBS film 56c and the reflective film 56h, the prism 56g formed with the PBS film 56f and the reflective film 56i, the PBS film 56c of the prism 56d, and the PBS film 56f of the prism 56g. The branching prism 56e is composed of the reflecting film 56h of the prism 56d and the reflecting prism 56j bonded to the reflecting film 56i of the prism 56g. The cross-sectional shapes of the branching prism 56e and the reflecting prism 56j are right-angled isosceles triangles, and the cross-sectional shapes of the prism 56d sandwiched between the PBS film 56c and the reflecting film 56h and the prism 56g sandwiched between the PBS film 56f and the reflecting film 56i are parallel. It is a quadrilateral. The PBS films 56c and 56f transmit P-polarized light while reflecting S-polarized light. Note that the reflection films 56h and 56i may be formed of a PBS film.

  The phase plate 57 is a phase plate that is disposed in one optical path of two linearly polarized light beams that are polarized and separated by the PBS prism array 56. The phase plate 57 is composed of, for example, a half-wave plate, and the one surface of the branching prism 56e. It is pasted face to face. The phase plate 57 converts one linearly polarized light (for example, P-polarized light) transmitted through the PBS films 56c and 56f into linearly polarized light (for example, S-polarized light) having the same polarization direction as the other.

  With the above-described configuration of the polarization conversion optical system 55, the P-polarized light and the S-polarized light are separated by the PBS films 56c and 56f. Among these, the P-polarized light is transmitted through the PBS film 56c, is incident on the phase plate 57 via the branching prism 56e, and is converted into S-polarized light by passing through this. The P-polarized light is transmitted through the PBS film 56f, enters the phase plate 57 via the branching prism 56e, and is transmitted therethrough, thereby being converted into S-polarized light at a position different from the S-polarized light.

  On the other hand, the S-polarized light that has been polarized and separated by the PBS film 56c is reflected by the PBS film 56c, then reflected again by the adjacent reflecting film 56h, and exits through the side of the branching prism 56e (upper side in FIG. 10). . The S-polarized light separated by the PBS film 56f is reflected by the PBS film 56f, then reflected again by the adjacent reflecting film 56i, and emitted through the side of the branching prism 56e (lower side in FIG. 10). To do.

  According to the configuration of the polarization conversion optical system 55, in order to divide the optical paths of the plurality of light source images into two optical paths by the branching prism 56e, the front group lens system 53 and the rear group lens system 54 are not decentered in parallel. The amount of deviation between P-polarized light and S-polarized light can be halved with respect to the configuration of the polarization conversion optical system 55 shown in FIG. As a result, it is possible to suppress deterioration of lens performance caused by the polarization conversion optical system 55.

  Furthermore, the polarization conversion optical system 55 may be configured as shown in FIG. FIG. 11 is a cross-sectional view showing still another modification of the polarization conversion optical system. The polarization conversion optical system 55 includes a triangular prism 58 formed with a PBS film 58a, a parallel plate 59 bonded to the PBS film 58a, and a phase plate 57 disposed near the pupil position. . The PBS film 58a is formed of an optical thin film that transmits P-polarized light while reflecting S-polarized light. The phase plate 57 is a phase plate disposed in one optical path of two linearly polarized light separated by the PBS film 58a. The phase plate 57 is composed of, for example, a half-wave plate and corresponds to the thickness of the parallel plate 59. Every other one is bonded to the light emitting surface of the triangular prism 58 bent 90 degrees.

  With the above-described configuration of the polarization conversion optical system 55, the light beams of the plurality of light source images are incident on the triangular prism 58 via the rear group lens system 54 and separated into P-polarized light and S-polarized light by the PBS film 58a. The S-polarized light is reflected by the PBS film 58 a, passes through the light emitting surface of the triangular prism 58, and exits between the adjacent phase plates 57 and 57.

  On the other hand, the P-polarized light separated by the PBS film 58a is transmitted through the PBS film 58a, reflected by the reflecting surface of the parallel flat plate 59, and again transmitted through the PBS film 58a. The P-polarized light transmitted through the PBS film 58a is incident on the phase plate 57 and is transmitted therethrough to be converted into S-polarized light.

  According to the above configuration of the polarization conversion optical system 55, it is not necessary to provide prisms in an array, and the PBS film 58a may be formed only on one surface of the triangular prism 58, and thus there is a possibility that the PBS may be generated in the prism array. Mutual positional shift and angular shift of the film 58a can be suppressed, and the polarization conversion optical system 55 can perform polarization conversion with high accuracy.

(Second Embodiment)
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation below, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 12 is a cross-sectional view showing a schematic configuration of the image projection apparatus of the present embodiment. The image projection apparatus 100 according to the present embodiment includes a point where a laser unit 61 is used as the light source 1, a point where a color prism 63 is disposed in the optical path between the TIR prism 3 and the DMD 4, and polarization on the screen side of the projection optical system 5. The configuration is the same as that of the first embodiment except that the switching element 68 is disposed and the DMD 4 is provided corresponding to each color light of red, green, and blue.

  The laser unit 61 has red (R), green (G), and blue (B) laser light sources, and synthesizes a white light beam from each color light of RGB. Compared with a light source such as a discharge lamp, the light source size is small, and a light beam that forms a light source image of a small size is emitted from the laser unit 61, and the polarization conversion optical system 55 can efficiently perform polarization conversion.

  The light source beam of the laser unit 61 is incident on the rod integrator 22. A diffusion plate wheel 62 is provided on the light exit surface of the rod integrator 22. The diffusion plate wheel 62 rotates at a high speed to further reduce speckles of the light beam emitted from the rod integrator 22, but the light beam emitted from the rod integrator 22 is in a random polarization state.

  In the above configuration, the light emitted from the light source 1 enters the TIR prism 3 through the illumination optical system 2, is totally reflected there, and then enters the DMD 4 through the color prism 63. The light that has entered the DMD 4 is modulated there and then emitted as image light, passes through the TIR prism 3 through the color prism 63, and further projects into the projection optical system 5 (polarization conversion relay optical system 52, projection lens system 51. ) And the polarization switching element 68.

  FIG. 13 shows a cross-sectional view of the color prism 63. The color prism 63 is color separation / combination means disposed in the optical path between the TIR prism 3 (see FIG. 12) and the DMD 4. In the present embodiment, the DMD 4 includes DMDs 4R, 4G, and 4B that are provided corresponding to three different color lights (red, green, and blue color lights), and the color prism 63 receives the light from the TIR prism 3. The light is separated into the three color lights and guided to the DMDs 4R, 4G, and 4B, and the reflected lights from the DMDs 4R, 4G, and 4B are combined in the same optical path.

  The color prism 63 is a combination of a triangular prismatic first color prism 64 and a second color prism 65, a substantially square prismatic third color prism 66, and a triangular prismatic fourth color prism 67. A surface of the first color prism 64 facing the second color prism 65 functions as a dichroic surface, and a dichroic film 64R that reflects red light and transmits blue light and green light is formed on this surface. An air gap layer is provided between the first color prism 64 and the second color prism 65. The surface of the second color prism 65 facing the third color prism 66 functions as a dichroic surface, and a dichroic film 65B that reflects blue light and transmits green light is provided on this surface. Air gap layers are also provided between the second color prism 65 and the third color prism 66 and between the first color prism 64 and the fourth color prism 67, respectively.

  The illumination light incident from the light incident / exit surface of the fourth color prism 67 is reflected by the dichroic film 64R, and the blue light and the green light are transmitted. The red light reflected by the dichroic film 64R is totally reflected by the side surface of the first color prism 64 and is emitted from the light incident / exit surface of the first color prism 64 to illuminate the DMD 4R. On the other hand, of the blue light and green light transmitted through the dichroic film 64R, the blue light is reflected by the dichroic film 65B of the second color prism 65, and the green light is transmitted. The blue light reflected by the dichroic film 65B is totally reflected by the side surface of the second color prism 65 and is emitted from the light incident / exit surface of the second color prism 65 to illuminate the DMD 4B. The green light transmitted through the dichroic film 65B is emitted from the light incident / exit surface of the third color prism 66 to illuminate the DMD 4G.

  The light incident on each DMD 4R, 4G, 4B is modulated there and then emitted as image light. The red image light reflected by the DMD 4R is incident on the light incident / exit surface of the first color prism 64, totally reflected by the side surface of the first color prism 64, and further reflected by the dichroic film 64R. The blue image light reflected by the DMD 4B is incident on the light incident / exit surface of the second color prism 65, is totally reflected by the side surface of the second color prism 65, and is further reflected by the dichroic film 65B. Further, the light passes through the dichroic film 64R of the first color prism 64. On the other hand, the green image light reflected by the DMD 4G enters the light incident / exit surface of the third color prism 66 and passes through the dichroic film 65B and the dichroic film 64R. The red, blue, and green image lights are combined on the same optical axis, emitted from the light incident / exit surface of the fourth color prism 67, and incident on the TIR prism 3 (see FIG. 12).

  Returning to FIG. 12, the polarization switching element 68 is disposed on the screen side of the projection optical system 5. The polarization switching element 68 may be disposed between the projection lens system 51 and the polarization conversion relay optical system 52 as long as it is closer to the screen than the polarization conversion optical system 55. You may arrange. As the polarization switching element 68, for example, a polarization switching element called Z-Screen manufactured by Real D can be used. The polarization switching element 68 emits an incident linearly polarized light beam by alternately switching the right circularly polarized light and the left circularly polarized light in a time division manner at high speed. Therefore, when projecting a stereoscopically viewable image, the left-eye image and the right-eye image are alternately displayed on the DMD 4, and the right circular polarization and the left circular polarization are synchronized by the polarization switching element 68 in synchronization therewith. What is necessary is just to switch alternately and to radiate | emit. In this case, the viewer wears the right eye by wearing polarizing glasses (for example, the right eye portion having a polarizing plate that transmits only the right circularly polarized light and the left eye portion having a polarizing plate that transmits only the left circularly polarized light). It is possible to view the projected image for the right eye and the projected image for the left eye with the left eye in a time-sharing manner, and the projected image can be viewed three-dimensionally by one image projecting device 100.

  According to the first and second embodiments described above, by using the polarization conversion relay optical system 52 in the image projection apparatus 100, it is possible to project an image with a single linearly polarized light whose polarization state is not disturbed. Therefore, it is possible to avoid a reduction in the amount of light of the projected image, and even when projected onto a polarizing screen, it is possible to appreciate a good 3D image without reducing the brightness and contrast of the projected image. . In addition, since it is possible to project two images with a single projection optical system for viewing a 3D image, each image is projected with two projection optical systems, and the two images are superimposed on the screen. Adjustment work is not necessary, and projection conditions such as the projection distance can be easily set as in the case of viewing a planar image.

  In the first and second embodiments, the configuration using the rod integrator 22 in the integrator optical system is shown. However, the present invention is not limited to this, and a lens array including a plurality of lenses is provided as the integrator optical system. A light beam from a light source may be divided into a plurality of light beams by an array to form a plurality of light source images.

  Further, the arrangement and configuration of the polarization conversion optical system 55 shown in FIGS. 9 to 11 may be applied to the image forming apparatus 100 of the second embodiment.

  The configuration of one of the optical systems (the front group lens system 53 and the rear group lens system 54) in the polarization conversion relay optical system 52 according to the present invention will be described more specifically with reference to lens configuration data and aberration diagrams of Examples. . The present invention is not limited to these examples. In the first to third embodiments, the surface number s of each lens is described corresponding to the optical system of FIG.

  For the lens configuration of the example, the surface data includes the surface number s, the radius of curvature r (unit: mm), the surface interval t (unit: mm) on the axis, the refractive index nd at a wavelength of 546.00 nm, in order from the left column. Abbe number vd and effective diameter d (unit: mm) are shown. Surface numbers s1 and s2 indicate the polarization conversion optical system 55, and s18 indicates an image surface.

Symbols shown in various data are as follows.
F: Pupil diameter (unit: mm)
Y'max: Maximum image height (unit: mm)

Example 1
Unit mm
[Surface data]
srt nd vd d
1 inf 2.00 1.51680 64.20 20.84
2 inf 6.73 20.85
3 -71.429 11.24 1.51680 64.20 20.88
4 46.676 7.02 1.80611 40.73 23.18
5 92.076 9.36 23.18
6 -126.287 14.13 1.83400 37.35 24.10
7 -54.652 6.15 26.18
8 -40.663 12.15 1.67270 32.17 25.99
9 -73.756 2.22 30.29
10 122.193 15.35 1.49700 81.61 32.79
11 -86.155 5.03 32.93
12 -100.159 4.94 1.78590 43.93 31.85
13 106.254 10.02 32.76
14 175.342 18.96 1.49700 81.61 36.45
15 -72.215 14.52 37.33
16 106.690 22.42 1.49700 81.61 37.01
17 3585.545 145.00 35.00
18 inf 8.59 18.50

[Various data]
F: 20.84
Y'max: 18.50

(Example 2)
Unit mm
[Surface data]
srt nd vd d
1 inf 2.00 1.51680 64.20 21.19
2 inf 13.06 21.19
3 -72.934 4.20 1.51680 64.20 21.26
4 46.386 7.12 1.80611 40.73 22.78
5 90.848 10.62 22.79
6 -122.750 14.72 1.83400 37.35 24.04
7 -53.921 6.20 26.30
8 -40.627 12.03 1.67270 32.17 26.12
9 -73.676 2.49 30.49
10 119.966 15.88 1.49700 81.61 33.13
11 -84.324 5.06 33.25
12 -96.301 4.27 1.78590 43.93 32.09
13 106.243 10.01 33.00
14 175.375 18.92 1.49700 81.61 36.77
15 -71.832 6.65 37.62
16 107.636 27.96 1.49700 81.61 37.58
17 3644.289 145.00 35.00
18 inf 3.74 17.96

[Various data]
F: 21.19
Y'max: 17.96

(Example 3)
Unit mm
[Surface data]
srt nd vd d
1 inf 2.00 1.51680 64.20 21.36
2 inf 11.03 21.37
3 -74.746 5.03 1.51680 64.20 21.42
4 46.005 7.12 1.80611 40.73 23.02
5 89.269 9.53 23.01
6 -117.534 14.29 1.83400 37.35 23.95
7 -52.926 5.85 26.15
8 -40.676 12.16 1.67270 32.17 25.97
9 -73.704 2.10 30.29
10 117.059 15.58 1.49700 81.61 32.86
11 -85.659 4.87 32.97
12 -96.140 4.40 1.78590 43.93 31.91
13 105.818 10.01 32.86
14 174.322 18.91 1.49700 81.61 36.69
15 -72.532 4.23 37.56
16 105.704 27.28 1.49700 81.61 37.53
17 3147.328 145.00 35.00
18 inf 5.01 18.08

[Various data]
F: 21.36
Y'max: 18.08

  14 to 22 show coma aberration (lateral aberration) at each image height at a wavelength of 546.00 nm. (A) of each figure is coma aberration of the light beam reaching the maximum image height, (b) of each figure is coma aberration of the light beam reaching 0.87 times the maximum image height, and (c) of each figure is The coma aberration of the light beam reaching a position 0.71 times the maximum image height, and (d) in each figure shows the coma aberration of the light beam reaching the axis. The horizontal axis indicates the position of the incident light beam on the pupil plane, and the vertical axis indicates the coma aberration amount at the position of each incident light beam.

  14 to 16 show the coma aberration of Example 1. FIG. FIG. 14 shows coma aberration of one optical system (front group lens system 53, rear group lens system 54, see FIG. 6), and FIGS. 15 and 16 show all optical systems (see FIG. 4) each having a magnification of 1 ×. ) Coma aberration. FIG. 15 shows coma aberration when the front group lens system 53 and the rear group lens system 54 are decentered by 2 mm from each other, and FIG. 16 shows coma aberration when there is no parallel decentering. In Example 1, the coma aberration amount of one optical system (the front group lens system 53 and the rear group lens system 54) is designed to be about the pixel of DMD4 (about 8 μm), and there is parallel decentration. The amount of coma in the entire optical system is suppressed to the same level as the coma aberration in the entire optical system without parallel decentering (see FIG. 16).

  17 to 19 show the coma aberration of the second embodiment. FIG. 17 shows coma aberration of one optical system (front group lens system 53, rear group lens system 54, see FIG. 6), and FIGS. 18 and 19 show all optical systems (see FIG. 4) each having a magnification of 1 ×. ) Coma aberration. FIG. 18 shows coma aberration when the front lens group 53 and the rear lens system 54 are decentered by 2 mm from each other, and FIG. 19 shows coma aberration when there is no parallel decentering. In Example 2, the coma aberration amount of one optical system (the front group lens system 53 and the rear group lens system 54) is designed to be 200 μm or less, and the coma aberration amount of all the optical systems decentered in parallel. Is suppressed to about a half pixel (4 μm) of the DMD4 pixel.

  20 to 22 show the coma aberration of Example 3. FIG. 20 shows coma aberration of one optical system (front group lens system 53, rear group lens system 54, see FIG. 6), and FIGS. 21 and 22 show all optical systems (see FIG. 4) each having a magnification of 1 ×. ) Coma aberration. FIG. 21 shows coma aberration when the front group lens system 53 and the rear group lens system 54 are decentered by 2 mm from each other, and FIG. 22 shows coma aberration when there is no parallel decentering. In Example 3, the coma aberration amount of one optical system (the front group lens system 53 and the rear group lens system 54) is designed to be 300 μm or less, and the coma aberration amount of all the optical systems decentered in parallel. Is suppressed to about 1 pixel (8 μm) of DMD4.

  INDUSTRIAL APPLICABILITY The present invention can be used for a polarization conversion relay optical system used in an image projection apparatus that projects an image displayed on a display element onto a projection surface and an image projection apparatus including the polarization conversion relay optical system.

DESCRIPTION OF SYMBOLS 1 Light source 2 Illumination optical system 4 DMD (display element)
4B DMD (display element)
4G DMD (display element)
4R DMD (display element)
5 Projection optical system 22 Rod integrator (integrator optical system)
23 Illumination Relay System 51 Projection Lens System 52 Polarization Conversion Relay Optical System 53 Front Group Lens System 54 Rear Group Lens System 55 Polarization Conversion Optical System 56 PBS Prism Array (Polarization Separation Element)
56c PBS film 56d prism 56e branching prism 56f PBS film 56g prism 56h reflection film 56i reflection film 56j reflection prism 57 phase plate 58 triangular prism 58a PBS film
59 Parallel plate 61 Laser unit 63 Color prism 68 Polarization switching element 100 Image projection device M Intermediate image P Pupil plane

Claims (8)

A display element composed of a digital micromirror device that displays an image by rotating a mirror constituting each pixel;
An illumination optical system that has an integrator optical system that forms a plurality of light source images from the light of the light source and guides the light from the light source to the display element;
An image projection apparatus comprising: a projection lens system that projects an image of the display element onto a projection surface; and an intermediate image of a display image of the display element that is disposed between the projection lens system and the display element. A polarization conversion relay optical system formed with the polarization direction aligned in one direction,
The polarization conversion relay optical system includes a front group lens system disposed on the intermediate image side with respect to the pupil plane, a rear group lens system disposed on the display element side with respect to the pupil plane, and the pupil plane. A polarization conversion optical system,
The polarization conversion optical system includes: a polarization separation element that separates light from the plurality of light source images into two linearly polarized light having different polarization directions; and a phase plate that emits the two linearly polarized light in a single polarization direction. Have
In all light bundles condensed in an effective image area, the front group lens system satisfies the following conditional expression (1), and the rear group lens system satisfies the following conditional expression (2): Polarization conversion relay optical system.
Δf <40 × k × p (1)
Δr <40 × p (2)
However,
Δf: a ray passing through the center of the pupil plane from an intermediate point between the coordinates of the ray passing through the upper end of the pupil plane and the coordinate of the ray passing through the lower end of the pupil plane in the image plane of the front group lens system The absolute value Δr of the coma aberration amount defined as the distance to the coordinates of: The coordinates of the light ray passing through the upper end of the pupil plane and the coordinates of the light ray passing through the lower end of the pupil plane in the image plane of the rear lens group The absolute value of the coma aberration amount defined as the distance from the intermediate point to the coordinates of the light ray passing through the center of the pupil plane k: the magnification of the polarization conversion relay optical system p: the pixel pitch of the display element The polarization conversion relay optical system according to claim 1, wherein the front group lens system satisfies the following conditional expression (1A), and the rear group lens system satisfies the following conditional expression (2A).
Δf <20 × k × p (1A)
Δr <20 × p (2A) The polarization conversion relay optical system according to claim 2, wherein the front group lens system satisfies the following conditional expression (1B), and the rear group lens system satisfies the following conditional expression (2B).
Δf <k × p (1B)
Δr <p (2B)   4. The polarization conversion relay optical system according to claim 1, wherein the front group lens system and the rear group lens system are arranged symmetrically with respect to the pupil plane.   5. The rear group lens system according to claim 1, wherein a light beam emitted from a position of the display element corresponding to the optical axis of the rear group lens system is converted into parallel light on the pupil side. The polarization conversion relay optical system according to claim 1.   An image projection apparatus comprising the polarization conversion relay optical system according to claim 1.   The image projection apparatus according to claim 6, wherein the light source is a laser beam.   The image projection apparatus according to claim 6, further comprising a polarization switching element that alternately switches light beams emitted from the polarization conversion optical system to two types of polarized light beams.

Images