JP2015022294A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized and highly-efficient image projection device.SOLUTION: The image projection device includes: a light source; a reflective image display element; a first optical element and a second optical element that are provided so as to lead light from the light source to the reflective image display element; optical path separation means that is provided between the first optical element and the second optical element and separates an optical path of light entering the reflective image display element from that of light reflected by the reflective image display element; and a projection optical system that projects image light modulated by the reflective image display element. A normal line passing through a center of the reflective image display element is eccentric to an optical axis passing through the light source and the projection optical system, in a parallel fashion, and the first optical element is eccentric to the optical axis in a direction identical to the eccentric direction of the normal line.

Description

  The present invention relates to an image projection apparatus provided with a reflective image display element.

  In recent years, an image projection apparatus using a reflective image display element such as a reflective liquid crystal panel or a DMD (digital micromirror device) is known. In an image projection apparatus using a reflective image display element, incident light and reflected light with respect to the reflective image display element are separated and guided to a projection optical system, and therefore an optical path separation means such as a polarization beam splitter or a total reflection prism is required. To do. For this reason, the back focus of the projection optical system becomes long and the total length of the projection optical system increases, leading to an increase in size and cost of the image projection apparatus.

  On the other hand, by disposing the optical path separating means between the illumination optical system and the projection optical system, the back focus of the projection optical system is reduced, and the illumination optical system and a part of the lenses of the projection optical system are made common. A configuration for reducing the size and cost is known.

  In Patent Document 1, a lens that is shared by the illumination optical system and the projection optical system has a decentered aspherical shape, so that sufficient imaging performance can be obtained even if the projection optical system is a decentered system. A configuration is disclosed. Patent Document 2 discloses a configuration in which the optical axis of the illumination optical system is arranged obliquely with respect to the normal line of the image display element surface in order to efficiently illuminate the image display element.

JP 2000-009992 A JP 2003-149559 A

  However, the eccentric aspherical lens as in Patent Document 1 requires higher processing accuracy than the spherical lens. On the other hand, when the lens shared by the illumination optical system and the projection optical system is decentered parallel to the optical axis of the projection optical system, the projection optical system becomes a coaxial system, so that sufficient imaging performance is obtained. Becomes relatively easy. However, the common lens is decentered parallel to the optical axis of the illumination optical system. For this reason, illumination light cannot be efficiently illuminated on the image display element.

  Further, as in Patent Document 2, when the illumination light is incident on the image display element obliquely, the entrance pupil of the illumination optical system becomes asymmetric, and an optical path difference between the incident light and the reflected light occurs in the image display element. For this reason, the optical path separating means such as the polarization beam splitter and the total reflection prism is increased in size. Further, since the pupil is asymmetrically arranged with respect to the center of the stop of the projection optical system, the diameter of the projection optical system is increased.

  In particular, when a reflective liquid crystal panel is used as the image display element, if the entrance pupil is asymmetric, the contrast is lowered due to the deterioration of viewing angle characteristics. In order to prevent a decrease in contrast, it is necessary to reduce the incident angle of illumination light. However, if the F value of the illumination optical system is increased in order to reduce the incident angle of the illumination light, the illumination efficiency decreases.

  Therefore, the present invention provides a small and highly efficient image projection apparatus.

  An image projection apparatus according to an aspect of the present invention includes a light source, a reflective image display element, a first optical element provided to guide light from the light source to the reflective image display element, and a second optical element. An optical element is provided between the first optical element and the second optical element, and separates an optical path between incident light to the reflective image display element and reflected light from the reflective image display element. And a projection optical system that projects the image light modulated by the reflective image display element, and the normal passing through the center of the reflective image display element is the light source and the projection optical system. The first optical element is decentered in the same direction as the decentering direction of the normal line with respect to the optical axis.

  Other objects and features of the present invention are illustrated in the following examples.

  According to the present invention, a small and highly efficient image projection apparatus can be provided.

1 is a configuration diagram of an image projection apparatus in Embodiment 1. FIG. It is a block diagram of the image projection apparatus as a comparative example. In Example 1, it is a figure which shows the illumination distribution with respect to various eccentric amounts of a condenser lens. FIG. 6 is a configuration diagram of an image projection apparatus in Embodiment 2. It is a figure which shows the magnitude | size of the color separation means with respect to the entrance pupil of the symmetrical and asymmetrical illumination light. FIG. 6 is a configuration diagram of an image projection apparatus in Embodiment 3.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and redundant description is omitted.

  First, the configuration of the image projection apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of an image projection apparatus 100 according to the present embodiment. FIGS. 1A and 1B show a first cross section (XZ cross section) and a second cross section including the optical axis and orthogonal to each other. Each section (YZ section) is shown. In addition, in order to clarify the structure of a present Example, the block diagram (FIG.1 (b)) of a YZ cross section has described the incident optical path and the reflected optical path separately. This also applies to other examples (FIGS. 4B and 6B).

  1A and 1B, 1 is a light source, and 2 is a parabolic reflector. Reference numeral 3 denotes an integrator optical system that uniformizes light from the light source 1. The integrator optical system 3 includes a first fly-eye lens 3a (first lens array) and a second fly-eye lens 3b (second lens array). The integrator optical system 3 is disposed between the light source 1 and a condenser lens 5a described later. A polarization conversion element 4 aligns non-polarized light from the light source 1 in a predetermined polarization direction. Reference numerals 5a and 5b denote condenser lenses. Reference numeral 6 denotes a wire grid polarization beam splitter (optical path separating means) disposed between the condenser lenses 5a and 5b. Reference numeral 7 denotes a reflective liquid crystal panel (reflective image display element), and reference numeral 8 denotes a projection optical system (projection lens).

  The condenser lenses 5 a and 5 b are a first optical element and a second optical element that are provided so as to guide light from the light source 1 to the reflective liquid crystal panel 7. The condenser lens 5 a (first optical element) and the condenser lens 5 b (second optical element) are disposed between the light source 1 and the reflective liquid crystal panel 7. The condenser lens 5a is disposed on the light source 1 side, and the condenser lens 5b is disposed on the reflective liquid crystal panel 7 side. In the present embodiment, the condenser lens 5 b is one element constituting the projection optical system 8.

  The wire grid polarization beam splitter 6 is provided between the condenser lens 5 a and the condenser lens 5 b, and separates the optical path between the incident light to the reflective liquid crystal panel 7 and the reflected light from the reflective liquid crystal panel 7. The projection optical system 8 projects the image light modulated by the reflective liquid crystal panel 7 onto a projection surface (not shown) such as a screen.

  The light emitted from the light source 1 is reflected by the paraboloid reflector 2 and enters the integrator optical system 3 as a substantially parallel light beam. The integrator optical system 3 splits a substantially parallel light beam from the light source 1. The light beams divided by the integrator optical system 3 are each aligned with the P-polarized light by the polarization conversion element 4. The split light beam emitted from the polarization conversion element 4 passes through the wire grid polarization beam splitter 6 through the condenser lens 5a. The light transmitted through the wire grid polarization beam splitter 6 passes through the condenser lens 5b and is superimposed on the reflective liquid crystal panel 7.

  The reflective liquid crystal panel 7 independently changes the polarization state of light incident on each pixel of the reflective liquid crystal panel 7 in accordance with a video signal input to the image projection apparatus 100 from an image supply device (not shown) such as a personal computer. Modulate to Of the reflected light from the reflective liquid crystal panel 7, the P-polarized light component passes through the condenser lens 5b, passes through the wire grid polarization beam splitter 6, and returns to the light source 1 side. On the other hand, the S-polarized component passes through the condenser lens 5 b, is reflected by the wire grid polarization beam splitter 6, and is guided to the projection optical system 8.

  C in FIG. 1B is an optical axis common to the light source 1, the integrator optical system 3, and the projection optical system 8 (an optical axis passing through the light source 1 and the projection optical system 8). A normal L passing through the center of the reflective liquid crystal panel 7 is decentered (displaced) in parallel with the direction D with respect to the optical axis C. Accordingly, the projection optical system 8 including the condenser lens 5b is decentered relatively parallel to the reflective liquid crystal panel 7, and is in a state of projection optical system shift (projection lens shift). In this embodiment, the projection optical system 8 is constituted by a coaxial system that does not include a decentered lens.

  Here, a problem of a projection optical system including a decentered lens will be described. When a lens that is decentered in the projection optical system is included, various aberrations having asymmetry derived from the decentering of the lens, such as decentering coma, decentering astigmatism, and decentering field curvature, are newly generated. In order to reduce various aberrations derived from decentration, it is necessary to cancel the asymmetry by newly using a decentered lens. However, the combination of these decentered lenses increases normal aberrations having symmetry, such as spherical aberration. If the number of spherical lenses is increased in order to reduce such aberration and obtain sufficient imaging performance, the projection optical system becomes large.

  In addition, there is a method using a decentered aspherical lens in order to cancel the asymmetry of various aberrations due to decentration and also to cancel normal aberration having symmetry with a small number of lenses. However, the eccentric aspheric lens requires higher processing accuracy than the spherical lens. Therefore, as compared with a projection optical system including a decentered lens, the projection optical system 8 configured by a common axis system as in the present embodiment can easily obtain sufficient imaging performance.

  Next, the optical path from which the illumination light from the light source 1 reaches the reflective liquid crystal panel 7 will be described. Here, a case where the condenser lens 50a corresponding to the condenser lens 5a of the present embodiment is not decentered (displaced) in parallel with the direction D with respect to the optical axis will be described with reference to FIG. 2 as a comparative example. FIG. 2 is a configuration diagram of an image projection apparatus 200 as a comparative example.

  As shown in FIG. 2, the optical axes of the condenser lenses 50 a and 50 b coincide with the optical axis C of the light source 1 and the projection optical system 8. For this reason, the split luminous flux emitted from the integrator optical system 3 is superimposed and illuminated in the vicinity of the optical axis C through the polarization conversion element 4 and the condenser lenses 50a and 50b. However, the reflective liquid crystal panel 7 is eccentric in parallel to the direction D with respect to the optical axis C. Therefore, the illumination light is illuminated at a position that is biased with respect to the effective area of the reflective liquid crystal panel 7, and the illumination efficiency is reduced.

On the other hand, in the image projection apparatus 100 of the present embodiment, the condenser lens 5a disposed on the light source 1 side is decentered (displaced) in the same direction as the eccentric direction (direction D) with respect to the optical axis C of the reflective liquid crystal panel 7. Are arranged. At this time, the illumination light R ₁ incident on the condenser lens 5 a from the vicinity of the optical axis C is refracted in the eccentric direction (direction D) of the reflective liquid crystal panel 7. Further, on the condenser lens 5b, the illumination light reaches a light beam height that is refracted in a direction opposite to the refraction direction (eccentric direction). For this reason, the illumination light is refracted so as to approach an incident angle parallel to the normal L passing through the center of the reflective liquid crystal panel 7.

Therefore, compared with the image projection apparatus 200 as a comparative example shown in FIG. 2, the image projection apparatus 100 of the present embodiment can cause more illumination light to reach the effective area of the reflective liquid crystal panel 7. High illumination efficiency can be realized. Further, the illumination light R ₁ incident on the condenser lens 5 a from the vicinity of the optical axis C is refracted in the eccentric direction (direction D) of the reflective liquid crystal panel 7, and the center of the reflective liquid crystal panel 7 is refracted on the condenser lens 5 b. Is incident at an incident angle close to (substantially parallel to) the normal L passing through. For this reason, the illumination lights R ₂ and R ₃ incident on the condenser lenses 5 a and 5 b from the off-axis are incident on the reflective liquid crystal panel 7 at a substantially symmetrical incident angle.

  Accordingly, the entrance pupil of the illumination light is substantially symmetrical with respect to the center. As a result, in order to efficiently illuminate the effective area of the reflective liquid crystal panel as in the conventional example, the adverse effect that occurs when the configuration in which the optical axis of the illumination optical system is arranged obliquely with respect to the reflective liquid crystal panel is adopted. Can be avoided. Specifically, since the pupil is arranged symmetrically with respect to the center of the stop of the projection optical system, it is possible to avoid the disadvantage that the aperture of the projection optical system becomes large. In addition, it is possible to avoid an extreme decrease in contrast due to deterioration of the viewing angle characteristics of the reflective liquid crystal panel. For this reason, it is not necessary to make the F value of the illumination optical system larger than a predetermined value, and high illumination efficiency can be maintained.

  As described above, according to the present embodiment, a compact image projection apparatus capable of efficiently illuminating the reflective image display element (reflective liquid crystal panel 7) while easily obtaining sufficient imaging performance of the projection optical system 8. 100 can be realized.

In this embodiment, the power of the condenser lens 5 a is φ ₁ , the power of the condenser lens 5 b is φ ₂ , the distance (in the main plane) between the condenser lenses 5 a and 5 b is d, and the normal L passing through the center of the reflective liquid crystal panel 7. Let D be the amount of eccentricity relative to the optical axis C (parallel eccentricity). At this time, the condenser lens 5a is decentered in parallel with the optical axis C by the amount of decentering D ′ (parallel decentering amount) in the same direction as the reflective liquid crystal panel 7 (normal line L passing through the center thereof). In the present embodiment, the eccentric amount D ′ is preferably set so as to satisfy the following expression (1).

0.9 {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁ <D ′ / D <1.1 {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁ . 1)
Here, the technical meaning of the formula (1) will be described. When paraxial ray tracing is performed on the condenser lens 5 a from the optical axis C to the center of the reflective liquid crystal panel 7 with respect to the light rays incident on the optical axis C in parallel to the optical axis C, The incident angle α of the light beam is expressed as the following formula (2).

α = (D−D ′) φ ₁ / (1−φ ₁ d) + φ ₂ D (2)
When formula (2) is modified in consideration of α = 0, which is a condition in which illumination light incident from above the optical axis C enters in parallel to the normal L passing through the center of the reflective liquid crystal panel 7, the following formula is obtained. (3) is obtained.

D ′ / D = {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁ (3)
In this embodiment, the eccentric amount D ′ of the condenser lens 5a is set so as to satisfy the expression (3) with respect to the eccentric amount D of the normal L passing through the center of the reflective liquid crystal panel 7 with respect to the optical axis C. Is more preferable. By satisfying the expression (3), the illumination light incident on the condenser lens 5a from the optical axis C is refracted in the eccentric direction (direction D) of the reflective liquid crystal panel 7, and with respect to the normal L by the condenser lens 5b. The light is refracted so as to enter the reflective liquid crystal panel 7 substantially in parallel. Here, “substantially parallel” is not limited to the case of being strictly parallel, but also includes a state of being substantially parallel or nearly parallel. For this reason, the effective area of the reflective liquid crystal panel 7 is efficiently illuminated in a state where the entrance pupil of the illumination light is held substantially symmetrical.

  On the other hand, when the decentering amount D ′ of the condenser lens 5a is excessive or insufficient with respect to the expression (3), the illumination light is illuminated at a position biased with respect to the effective area of the reflective liquid crystal panel 7. Decreases.

  The coefficients 0.9 and 1.1 on the left and right sides of the equation (1) are within ± 10% from the decentering amount of the condenser lens 5a that can illuminate the effective area of the reflective liquid crystal panel 7 most efficiently. A range is specified so that the amount of eccentricity is within the range.

Next, the illuminance distribution that illuminates the effective area of the reflective liquid crystal panel 7 will be described with reference to FIG. FIG. 3 shows an example of an illuminance distribution that illuminates the effective area of the reflective liquid crystal panel 7 at various eccentric amounts D ′. Here, the power arrangement of the condenser lens 5a is φ ₁ = 0.01229, φ ₂ = 0.01537, d = 35 mm, and S = 3.0 mm, respectively. Further, when D ′ / D = A {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁ , the amount of eccentricity D ′ is defined by a coefficient A.

  When the coefficient A (the eccentric amount D ′) is 0.8 or 1.2, the eccentric amount D ′ is insufficient or excessive. For this reason, the location deviated from the effective area of the reflective liquid crystal panel 7 is illuminated, and in particular, the illuminance at the upper and lower peripheral portions of the effective area is reduced. Therefore, in this case, the illumination efficiency decreases. On the other hand, when the coefficient A is 0.9 to 1.1, the eccentricity amount D ′ is appropriate. For this reason, the illuminance reduction in the upper and lower peripheral portions of the effective area does not occur, and the effective area of the reflective liquid crystal panel 7 is efficiently illuminated. Therefore, it is preferable that the amount of eccentricity D ′ is set within a range that satisfies the expression (1).

  Next, the configuration of the image projection apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram of the image projection apparatus 100a according to the present embodiment. FIGS. 4A and 4B show a first cross section (XZ cross section) and a second cross section including the optical axis and orthogonal to each other. Each section (YZ section) is shown. In addition, the same code | symbol is attached | subjected about the element same as FIG.

  The image projection apparatus 100a of the present embodiment is disposed between the condenser lens 5b and the reflective liquid crystal panel 7 (7R, 7G, 7B) with respect to the image projection apparatus 100 (FIG. 1) of the first embodiment. A cross dichroic prism 9 (color separation means) is provided. The cross dichroic prism 9 separates the light from the light source 1 into at least two color lights (in this embodiment, three colors of R, G, and B). In the image projection apparatus 100a, the light from the light source 1 is separated into red light (R), green light (G), and blue light (B), and reflective liquid crystal panels 7R, 7G, and 7B corresponding to the respective color lights are used. In order to form a video (image), a full-color video can be projected.

  Light from the light source 1 is converted to P-polarized light by the polarization conversion element 4 and passes through the wire grid polarization beam splitter 6. Thereafter, the light transmitted through the wire grid polarization beam splitter 6 is separated into red light, green light, and blue light by the cross dichroic prism 9, and enters the reflective liquid crystal panels 7R, 7G, and 7B corresponding to the respective colors. . The red light, the green light, and the blue light whose polarization states are modulated according to the video signal by the reflective liquid crystal panels 7R, 7G, and 7B are combined by the cross dichroic prism 9. The S-polarized component of the combined color lights passes through the condenser lens 5b, is reflected by the wire grid polarization beam splitter 6, and is guided to the projection optical system 8.

  As shown in FIG. 4B, the normal L passing through the center of the reflective liquid crystal panel 7 is decentered in parallel with the direction D with respect to the optical axis C, as in the first embodiment. For this reason, the projection optical system 8 including the condenser lens 5b is decentered relatively parallel to the reflective liquid crystal panel 7 (7R, 7G, 7B) and is in a state of shifting the projection optical system. However, since the projection optical system 8 is configured as a coaxial system, sufficient imaging performance can be obtained relatively easily as compared with a case where a decentered lens is included.

  In the present embodiment, similarly to the first embodiment, the condenser lens 5a disposed on the light source 1 side is connected to the optical axis C of the normal L passing through the center of the reflective liquid crystal panel 7 (7R, 7G, 7B). It is eccentric in the same direction as the eccentric direction (direction D). Therefore, the illumination light is efficiently illuminated on the effective area of the reflective liquid crystal panel 7 (7R, 7G, 7B).

  The condenser lens 5b is given an appropriate amount of eccentricity D 'expressed by the equation (1). For this reason, as in the first embodiment, the illumination light incident on the condenser lens 5b from the vicinity of the optical axis C approaches parallel to the reflective liquid crystal panel 7 (7R, 7G, 7B) (substantially parallel). The entrance pupil of the illumination light with respect to the reflective liquid crystal panel 7 is substantially symmetric.

  Next, with reference to FIG. 5, an advantage that the entrance pupil of the illumination light with respect to the reflective liquid crystal panel 7 is symmetrical will be described. FIG. 5 is a conceptual diagram showing a path when incident light and outgoing light pass through the color separation means with respect to a light ray incident on the cross dichroic prism 9 (color separation means) and reflected by the reflective liquid crystal panel 7. This is a comparison of the size of the color separation means. In FIG. 5, a solid line indicates a light ray incident on the cross dichroic prism 9 (incident light), and a broken line indicates a light ray reflected by the reflective liquid crystal panel 7 (emitted light). FIG. 5A shows a case where the incoming and outgoing light is symmetric with respect to the reflective liquid crystal panel 7 (when incident light and outgoing light pass through the same path). FIG. 5B shows a case where the incoming / outgoing light is asymmetric with respect to the reflective liquid crystal panel 7 (when incident light and outgoing light pass through different paths).

  5A and 5B, when the entrance pupil of the illumination light of the illumination light is asymmetric (FIG. 5B), both the emitted light and the reflected light are converted into the cross dichroic prism 9. In order to pass through, the cross dichroic prism 9 is enlarged. Further, since the back focus of the projection optical system 8 becomes long, it is difficult to downsize the entire image projection apparatus 100a.

  In the present embodiment, a cross dichroic prism 9 (color separation means) is disposed between the condenser lens 5 b and the reflective liquid crystal panel 7. On the other hand, when the optical axis of the illumination optical system is arranged obliquely with respect to the reflective liquid crystal panel as in the conventional configuration, the incident / exit light with respect to the reflective liquid crystal panel is asymmetric. For this reason, if it is going to pass both inside the color separation means without omission, a color separation means will enlarge as shown in FIG.5 (b).

  According to the configuration of the present embodiment, the entrance pupil of the illumination light with respect to the reflective liquid crystal panel is symmetrical, so that the color separation means can be reduced in size. For this reason, it is possible to realize a small-sized image projection apparatus capable of efficiently illuminating the reflective liquid crystal panel while easily obtaining sufficient imaging performance using the projection optical system as a coaxial system.

  Next, with reference to FIG. 6, the structure of the image projector in Example 3 of this invention is demonstrated. FIG. 6 is a configuration diagram of the image projection apparatus 100b in the present embodiment. FIGS. 6A and 6B are a first cross section (XZ cross section) and a second cross section including the optical axis and orthogonal to each other. Each section (YZ section) is shown. 6 (a) and 6 (b), 10 is a condenser lens, 11 is a color wheel, 12 is a rod integrator, 13 is a total reflection prism, and 14 is a DMD (digital micromirror device) as a reflective image display element. ). In addition, the same code | symbol is attached | subjected about the element same as FIG.

  The light emitted from the light source 1 is reflected by the parabolic reflector 2 and becomes a substantially parallel light beam. Then, this light beam is most condensed by the condenser lens 10 in the vicinity of the incident surface 12 a of the rod integrator 12 and enters the inside of the rod integrator 12. Similar to the fly-eye lens, the rod integrator 12 is an element (integrator optical system) for making the illuminance distribution uniform to illuminate the reflective image display element (DMD 14). The light beam incident on the rod integrator 12 is repeatedly reflected inside the rod integrator 12. A uniform illuminance distribution can be obtained on the exit surface 12 b of the rod integrator 12.

  The exit surface 12b of the rod integrator 12 is conjugated with the DMD 14 via the condenser lenses 5a and 5b, and has a similar shape to the DMD 14. The luminous flux diverging from the exit surface 12b is critically illuminated on the DMD 14 by total reflection at the boundary surface of the total reflection prism 13 by the condenser lenses 5a and 5b. The optical path of the light beam incident on the DMD 14 is switched by a movable micromirror that constitutes the DMD 14. Since the light beam whose optical path has been switched exceeds the critical angle at the boundary surface of the total reflection prism 13, it passes through without causing total reflection and is guided to the projection optical system 8.

  In general, the color wheel 11 includes three color filters that transmit red light, green light, and blue light. Light from the light source 1 is applied to the color filter of the color wheel 11 by the condenser lens 10. When the color wheel 11 rotates, the color filter of the light irradiating unit is sequentially switched to red transmission, green transmission, or blue transmission.

  With such a configuration, light incident on the rod integrator 12 is sequentially switched to red light, green light, and blue light, and light that illuminates the DMD 14 is switched in the order of red, green, blue, and red. By sequentially driving the DMD 14 so that images corresponding to the respective colors are projected in accordance with the switching timing, the red, green, and blue images are switched in time series. By repeating this operation at a high speed, the viewer of the video can view the full-color video.

  As shown in FIG. 6B, the normal L passing through the center of the DMD 14 is eccentric in parallel with the direction D with respect to the optical axis C, as in the first embodiment. For this reason, the projection optical system 8 including the condenser lens 5b is decentered relatively parallel to the DMD 14, and is in a state of shifting the projection optical system. Since the projection optical system 8 is configured as a coaxial system, sufficient imaging performance can be obtained relatively easily as compared with the case where a decentered lens is included.

  In the present embodiment, similarly to the first embodiment, the condenser lens 5a arranged on the light source 1 side is deviated in the same direction as the eccentric direction (direction D) of the normal L passing through the center of the DMD 14 with respect to the optical axis C. I have a heart. For this reason, the illumination light is efficiently illuminated on the effective area of the DMD 14. Further, an appropriate amount of eccentricity D ′ expressed by the expression (1) is given to the condenser lens 5b. Therefore, as in the first embodiment, the illumination light incident on the condenser lens 5b from the vicinity of the optical axis C approaches parallel to the DMD 14 (reflection type image display element), and the entrance pupil of the illumination light with respect to the DMD 14 is substantially symmetric. It becomes a shape. Therefore, it is not necessary to increase the size of the total reflection prism 13 in order to pass incident light and reflected light through the total reflection prism 13 without leakage. For this reason, size reduction of the image projection apparatus 100b can be achieved.

  According to the present embodiment, in an image projection apparatus using a DMD, a small image projection apparatus capable of efficiently illuminating the DMD while easily obtaining sufficient imaging performance of the projection optical system is realized. Can do.

  Thus, according to each embodiment, a small and highly efficient image projection apparatus can be provided.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation, a change, and the combination of a structure are possible within the range of the summary.

  For example, in the configuration of the first embodiment, instead of the wire grid polarization beam splitter 6, as an optical path separation unit, other polarization such as a cube-shaped polarization beam splitter (dielectric multilayer film polarization beam splitter) using a dielectric multilayer film is used. A beam splitter may be used. Further, in the configuration of the second embodiment, instead of the cross dichroic prism 9, another prism such as a Philips dichroic prism may be used. Further, as the light source 1, a solid light emitting element such as an LED light source or a laser light source may be used in addition to the ultrahigh pressure mercury lamp.

  Further, although the condenser lens (refractive optical element) is used as the first optical element and the second optical element, the present invention is not limited to this, and a mirror (reflection optical element) can also be used. Further, the eccentric amount D of the normal L passing through the center of the reflective image display element with respect to the optical axis C can be configured to be variable. By making the shift amount of the projection optical system shift variable, it is possible to provide an image projection apparatus with an increased degree of freedom in adjusting the projection direction. In order to realize this, for example, a movable mechanism (first movable means) can be provided in the reflective image display element. Alternatively, a movable mechanism may be provided in a unit in which the light source 1, the integrator optical system, the condenser lens 5 b, and the projection optical system 8 are integrated with the reflective image display element fixed. At this time, the condenser lens 5a is also provided with a movable mechanism (second movable means) so that the amount of eccentricity D ′ can be made variable, and the condenser lens 5a can satisfy Equation (1) in conjunction with the change in the amount of eccentricity D. The eccentricity D ′ with respect to the optical axis C can be changed. With such a configuration, the reflective image display element can be illuminated more efficiently.

1: Light source 5a, 5b: Condenser lens 6: Wire grid polarization beam splitter 7: Reflective liquid crystal panel 8: Projection optical system 13: Total reflection prism 14: DMD

Claims (17)

A reflective image display element;
A first optical element and a second optical element provided to guide light from a light source to the reflective image display element;
Optical path separation means provided between the first optical element and the second optical element, for separating an optical path between incident light to the reflective image display element and reflected light from the reflective image display element When,
A projection optical system for projecting image light modulated by the reflective image display element,
The normal passing through the center of the reflective image display element is decentered parallel to the optical axis passing through the light source and the projection optical system,
The image projection apparatus, wherein the first optical element is decentered with respect to the optical axis in the same direction as an eccentric direction of the normal line. The first optical element and the second optical element are disposed between the light source and the reflective image display element,
The image projection apparatus according to claim 1, wherein the first optical element is disposed on the light source side, and the second optical element is disposed on the reflective image display element side.   The image projecting apparatus according to claim 1, wherein the second optical element is one element constituting the projection optical system. The power of the first optical element is φ ₁ , the power of the second optical element is φ ₂ , the distance between the first optical element and the second optical element is d, and the reflection type image display element When the amount of eccentricity of the normal line passing through the center with respect to the optical axis of the projection optical system is D, the amount of eccentricity D ′ with respect to the optical axis of the first optical element is:
0.9 {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁ <D ′ / D <1.1 {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁
4. The image projection apparatus according to claim 1, wherein the image projection apparatus is set to satisfy the following. The eccentric amount D ′ is
D ′ / D = {φ ₁ + (1−φ ₁ d) · φ ₂ } / φ ₁
The image projection apparatus according to claim 4, wherein the image projection apparatus is set so as to satisfy. First movable means for varying the amount of eccentricity with respect to the optical axis of the normal passing through the center of the reflective image display element;
6. The image projection apparatus according to claim 1, further comprising: a second movable unit configured to vary an amount of eccentricity of the first optical element with respect to the optical axis.   The image projection apparatus according to claim 1, wherein the reflective image display element is a reflective liquid crystal panel or a DMD.   The image projection apparatus according to claim 1, wherein the optical path separation unit is a wire grid polarization beam splitter or a dielectric multilayer polarization beam splitter.   The image projection apparatus according to claim 1, wherein the optical path separating unit is a total reflection prism.   The image projection apparatus according to claim 1, further comprising an integrator optical system disposed between the light source and the first optical element.   The image projector according to claim 10, wherein the integrator optical system includes a first lens array and a second lens array.   The image projection apparatus according to claim 10, wherein the integrator optical system is a rod integrator.   2. The apparatus according to claim 1, further comprising color separation means arranged between the second optical element and the reflective image display element for separating light from the light source into at least two color lights. The image projection apparatus of any one of thru | or 12.   The image projection apparatus according to claim 1, wherein the first optical element and the second optical element are a refractive optical element or a reflective optical element.   The image projection apparatus according to claim 14, wherein the first optical element and the second optical element are condenser lenses.   The image projection apparatus according to claim 1, wherein the projection optical system includes a coaxial system that does not include a decentered lens.   Light incident on the first optical element on the optical axis is refracted in the decentered direction of the reflective image display element, and the reflective type is parallel to the normal line by the second optical element. The image projection apparatus according to claim 1, wherein the image projection apparatus is refracted so as to be incident on the image display element.