JP5213761B2 - Illumination optical system and image projection apparatus having the same - Google Patents

Description

  The present invention relates to an illumination optical system and an image projection apparatus having the illumination optical system, and is suitable, for example, for a liquid crystal projector that enlarges and projects a projected image original image based on a liquid crystal panel (image display element) on a screen surface.

  Conventionally, various image projection apparatuses (liquid crystal projectors) have been proposed in which a projected image original image based on an image display element such as a liquid crystal display element (liquid crystal panel) is enlarged and projected on a screen surface. As an illumination optical system for use in an image projection apparatus, an illumination optical system configured to uniformly illuminate an image display element by arranging a lens array in which a plurality of microlenses are two-dimensionally arranged in an optical path is known. (Patent Documents 1 and 2).

  FIG. 9 is a schematic view of a main part of a conventional image projection apparatus. In FIG. 9, light emitted from a light source 101 such as a lamp is radiated by a reflector 102 in a predetermined direction. Thereafter, the light is separated into a plurality of light beams by the lens arrays 103 and 108, the light beams are condensed by the condenser lens 104 via the polarization separation element 107, and the image display element 105 is superimposed on the light beams for illumination. doing. The image light modulated by the image display element 105 is projected onto the screen S by the projection optical system 106 to generate an enlarged image.

Japanese Patent Laid-Open No. 06-075200 Japanese Unexamined Patent Publication No. 07-181392 Japanese Patent Laid-Open No. 08-304739

  In a general image projection apparatus, the light intensity distribution on the exit pupil EP in the projection optical system depends on the conjugate image of the light source image generated by the lens arrays 103 and 108. In the image projection apparatus shown in FIG. 9, the light source image by the lens arrays 103 and 108 is formed in the vicinity of the polarization conversion element 107, and the conjugate image is formed on the exit pupil plane EP of the projection lens 106. FIG. 13 is a schematic diagram of a plurality of light source images 101 a formed in the vicinity of the polarization conversion element 107.

  In the image projection apparatus, when the image projected on the screen S is completely formed as an image of the image display element (in focus), the influence of the intensity distribution of the pupil of the projection optical system is completely problematic. It will not be. However, when the imaging position deviates from the screen surface, the quality of the projected image decreases. At this time, in the case of an image having a sharp edge, for example, a line image such as a grid, if the image formation position is shifted, the image formation is not blurred so that the sharpness of the image edge is lost. Come out of focus to separate.

  Hereinafter, the reason will be described. The image forming relationship is a point-to-point conjugate relationship. For this reason, for example, as shown in FIG. 10, when one point O of the object plane OB is imaged on the image plane Sa by the optical system L, the light flux Φ is condensed at one point i. As shown in FIG. 11, when the image formation position (focus) at one point O deviates from the image plane Sa, the light flux Φ is not condensed at one point on the image plane Sa, and the light intensity distribution of the light flux becomes the image plane. Can be on Sa. This light intensity distribution is similar to the pupil distribution of the projection optical system. Consider the light intensity distribution on the image plane Sa when the line image LN is displayed on the image display element (object plane) as shown in FIG.

  Here, since the line image LN has a certain narrow width and can be considered as a rectangle that is much longer than the width in a predetermined direction, the light intensity distribution in the narrow-width direction LNA becomes a problem when blurred. The light intensity distribution in the width direction of the line is a distribution obtained by integrating the two-dimensional conjugate light source image of the pupil in the direction of the long side of the line. An example of the light intensity distribution on the pupil plane of the cross section of the line image in the width direction LNA is shown in FIG. The displayed line image can be considered as a set of points. The distribution of the line image of the line A in FIG. 12 on the image plane Sa is as shown in FIG. On the image plane Sa, a distribution in which the intensity distribution Q blurred by the light beam P from one point on A is continuously superimposed in the range of the conjugate image of the line image (dotted line).

  FIG. 16 is a cross-sectional view of a blurred image of a line image due to this distribution. In FIG. 16, the dotted line is a projected image in a focused state, whereas the solid line is a projected image when the subject is not in focus. As shown by points D1, D2, and D3, nonuniform light intensity changes occur in the edge portion D of the image corresponding to the blur width D of the solid line projection image. At this time, since the observer's vision is sensitive to the brightness of the brightness, the portions D1 and D3 where the intensity changes abruptly and the portion D2 where the intensity changes slowly are distinguished and recognized, and between the parts D1 and D3 Observe that there is a dark part. Therefore, the edge portion D in FIG. 16 is observed as a plurality of thin lines being scattered, so that the quality of the observed image is lowered and the quality of the blur is significantly lowered. In addition, when such a dark portion is formed, the quality of the observation image is deteriorated, and it is difficult to accurately adjust the focus on the image plane Sa.

  The present invention makes it possible to easily adjust the focus of a projected image on the screen surface by smoothly blurring the projected image even when the projected image by the projection optical system is projected off the screen surface. An object is to provide an illumination optical system and an image projection apparatus having the illumination optical system.

The illumination optical system of the present invention is an illumination optical system for illuminating an image display element, the light of the light source or separated into a plurality of luminous fluxes, a first lens array for forming a plurality of light source images, the first A second lens array disposed closer to the image display element than the one lens array; a polarization conversion element that aligns the polarization direction of the light emitted from the second lens array; and the plurality of light beams superimposed on the irradiated surface. a condensing unit, a light source image moving means for moving the position of the multiple light source image formed on the pupil of the projection optical system for projecting the light modulated by the image display device onto a predetermined surface possess the The light source image moving means holds the first lens array, the second lens array, and the polarization conversion element, and is capable of moving in a direction perpendicular to the optical axis. have a driving means for moving in a direction perpendicular to the optical axis It is characterized in Rukoto.

  According to the present invention, even when the projection image by the projection optical system is projected off the screen surface, the blur of the projection image is smoothly blurred, the quality of the projection image on the screen surface is good, and focus adjustment is performed. An illumination optical system and an image projection apparatus having the same can be obtained.

Sectional drawing of the principal part of Example 1 of this invention Cross section of the main part of Reference Example 1 Cross section of the main part of Reference Example 2 Cross section of the main part of Reference Example 3 The principal part front view of the 1st lens array which concerns on this invention The principal part front view of the 1st lens array which concerns on this invention Cross-sectional view of main parts of Reference Example 4 Sectional view of main parts of Reference Example 5 Cross-sectional view of main parts of a conventional image projection apparatus Explanatory drawing of conjugate relationship between object surface and projection surface Explanatory drawing of conjugate relationship between object surface and projection surface Schematic diagram of projected object Explanatory drawing of the light intensity distribution on the pupil plane of the projection optical system of the image projection apparatus Explanatory drawing of the light intensity distribution of the line image of the pupil plane of the projection optical system of the image projection apparatus Illustration of light intensity distribution on object plane and projection plane Explanatory drawing of blurred line image on projection surface Explanatory drawing of a blurred image of a projection surface in the present invention Explanatory drawing of the polarization conversion element concerning the illumination optical system of this invention

  Hereinafter, the best mode of an illumination optical system of the present invention and an image projection apparatus having the illumination optical system will be described in detail with reference to the drawings. The illumination optical system for illuminating the illuminated surface of the present invention separates the light from the light source means into a plurality of light beams by the light beam separation means, condenses the light flux based on the separated light source images by the light collecting means, It is superimposed on the irradiated surface. At this time, a light source in which an imaging position of a plurality of light source images formed on a pupil (exit pupil) of a projection optical system (projection lens) that projects an image display element provided on an irradiated surface onto a predetermined surface is provided in an optical path It is displaced (moved) in the direction perpendicular to the optical axis by the image moving means. Preferably, the image is displaced while the image is projected. Here, the predetermined surface is a screen surface (projected surface) or the like, and the imaging position of the light source image substantially corresponds to the pupil position (substantially the position of the aperture) of the projection optical system. The light source image moving means described above can continuously displace (change or move) the imaging position of the light source image. The light source image moving means accommodates, for example, a light beam separating means, and a first or second housing that vibrates around an axis perpendicular to the optical axis and perpendicular to the optical axis, which is movable in a direction orthogonal to the optical axis. It has a parallel flat plate or a rotatable parallel flat plate inclined with respect to the optical axis.

[Example 1]
FIG. 1 is a schematic diagram of a main part in a cross section including a central axis (optical axis) O of an image projection apparatus having an illumination optical system according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a light source means, which is a light source that emits white light from a high-pressure mercury lamp (which may be a metal halide lamp or the like). Reference numeral 2 denotes a reflector, which is composed of a spheroid mirror or a rotating paraboloid (concave mirror) that efficiently reflects the light beam from the light source means 1. Reference numeral 3 denotes a first lens array (first fly-eye lens) as a light beam separating unit, which divides (separates) a light beam from the light source unit 1 side into a plurality of light beams. Reference numeral 4 denotes a second lens array (second fly-eye lens), which is arranged corresponding to the first lens array 3.

  Reference numeral 5 denotes a polarization conversion element (polarization beam splitter), which has a polarization separation surface for aligning non-polarized light in a specific polarization direction, thereby reflecting light of a predetermined polarization state and having a polarization state orthogonal to the polarization state. Light is transmitted. A plurality of light source images by the light beams that have passed through the first and second lens arrays 3 and 4 are formed in the vicinity of the polarization conversion element 5. Reference numeral 6a denotes a first condenser lens. Reference numeral 6b denotes a second condenser lens. The first and second condenser lenses 6 a and 6 b constitute a condensing lens (condensing means) 6. The condenser lens 6 superimposes the light beams emitted from the plurality of light source images on the surface of the image display element 7 for illumination. Reference numeral 7 denotes a liquid crystal panel (light valve, hereinafter also referred to as “panel”) as an irradiated object (image display element). The first lens array 3 and the panel 7 are in a conjugate relationship. A projection optical system (projection lens) 8 projects image information based on the panel 7 onto a screen (on a predetermined surface) S.

  In this embodiment, a plurality of light source images formed in the vicinity of the polarization conversion element 5 are formed on the pupil EP of the projection lens 8. That is, the positions of the plurality of light source images and the pupil EP of the projection lens 8 are in a conjugate relationship. FIG. 5 is a plan view of the main part of the first lens array 3. The first lens array 3 has a configuration in which a plurality of microlenses 3a are two-dimensionally arranged. The configuration of the second lens array 4 is the same as that of the first lens array 3 shown in FIG.

  FIG. 18 is an explanatory diagram of a part of the polarization conversion element 5. The polarization conversion element 5 includes a plurality of polarization separation surfaces 5a, a plurality of reflection surfaces 5b, and a plurality of half-wave plates 5c. Specifically, the polarization conversion element 5 here includes a polarization separation surface 5a, a reflection surface (or polarization separation surface) 5b, and a half-wave plate 5c as one set, and a plurality of such sets are arranged (light An optical element (polarization conversion element) in the form of an array in a direction substantially orthogonal to the axis. In this polarization conversion element 5, out of the light incident on each polarization separation surface 5 a, a polarization component having a predetermined polarization direction is transmitted through and emitted from the polarization conversion element 5.

  On the other hand, of the light incident on each polarization separation surface 5a, a polarization component having a polarization direction orthogonal to the predetermined polarization direction is reflected by the polarization separation surface 5a and further reflected by the reflection surface 5b. Then, the polarization direction is converted by 90 degrees by the half-wave plate 5 c and emitted from the polarization conversion element 5. Thus, the polarization conversion element 5 converts the incident non-polarized light into linearly polarized light having a predetermined polarization direction and emits it.

  In this embodiment, an illumination optical system is constituted by the optical elements from the reflector 2 to the condenser lens 6. Here, the first lens array 3 to the polarization conversion element 4 are housed and fixed in an independent lens array section housing K1. The lens array unit housing K1 and driving means 11 described later constitute light source image moving means. The lens array unit casing K1 includes an optical element holding unit 9 that holds optical elements such as the first and second lens arrays 3 and 4 and a polarization conversion element, and a casing unit 10 that holds the optical element holding unit 9. ing.

  The optical element holding unit 9 and the housing unit 10 are held by connection so that the optical element can move in a direction (vertical direction) orthogonal to the optical axis O. When the projection lens 8 projects an image based on the image display element 7 onto the screen S, the optical element holding unit 9 is moved in the direction perpendicular to the optical axis O of the condenser lens 6 by the driving unit 11. Thereby, the light source image formed in the vicinity of the second lens array 4 by the first lens array 3 is moved in time, and the light intensity distribution in the pupil plane EP in the projection lens 8 conjugate with the light source image. Is moving.

  FIG. 17 is an explanatory diagram of the effects obtained in this embodiment. By periodically moving the intensity distribution on the pupil plane as shown in FIG. 14 between intensity peaks, the intensity distribution of the blurred part shown in FIG. 16 becomes a blur part that changes smoothly as shown in FIG. Can be converted. In FIG. 17, a dotted line indicates a blurred portion in FIG. As a result, the light intensity distribution of the light on the pupil EP surface of the projection lens 8 becomes smoother in time, so that the quality of the projected image is improved by moving the optical element holding unit 9 at a high speed to the extent that the observer does not feel it. The quality of the blurred image can be improved. Here, when moving the lens array unit housing K1, the illumination area of the image display element 7 can be kept constant by always moving the sides of the first and second lens arrays 3 and 4 in parallel. it can. Further, the movement may be continuously performed while the image is projected, or may be temporarily interrupted when the focus is achieved.

[ Reference Example 1 ]
FIG. 2 is a cross-sectional view of the main part including the central axis O of Reference Example 1 as an image projection apparatus having an illumination optical system . Compared with the first embodiment, the present reference example has a first parallel plate 21 and a second parallel plate 21 that constitute the light source image moving means K2 between the polarization conversion element 5 and the condenser lens 6 instead of the lens array unit housing K1. The difference is that the parallel plate 22 is provided, and the other configurations are the same. The same optical elements as those of the first embodiment shown in FIG.

In this reference example , when image information based on the panel 7 is projected onto the screen S by the projection optical system 8, the first parallel plate 21 is driven by the driving means 23 in the first direction perpendicular to the optical axis O of the condenser lens 6. Are continuously driven within a predetermined angle range around the axis a1. Further, the second parallel flat plate 22 is continuously vibrated within a predetermined angle range around the second axis a2 in a direction orthogonal to the first axis a1 by the driving means. Thereby, the light source images by the lens arrays 3 and 4 are averaged temporally. Thereby, the light intensity distribution of the pupil EP in the projection optical system 8 is smoothed, and the quality of the blurred image of the projection image is improved.

[ Reference Example 2 ]
FIG. 3 is a cross-sectional view of the main part including the central axis O of Reference Example 2 as an image projection apparatus having an illumination optical system . Compared with the first embodiment, the present reference example is a rotatable parallel tilted with respect to the optical axis O of the condensing lens 6 between the polarization conversion element 5 and the condensing lens 6 instead of the lens array housing K1. The difference is that the flat plate 31 is provided as the light source image moving means K3, and the other configurations are the same. The same optical elements as those of the first embodiment shown in FIG. The parallel plate 31 is fixed to a cylindrical casing 32, and the casing 32 is rotated about the optical axis O of the condenser lens 6 by a driving means 33 such as a motor.

In this reference example , when the image information based on the panel 7 is projected onto the screen S by the projection optical system 8, the parallel flat plate 31 is continuously centered around the axis parallel to the optical axis O of the condenser lens 6. The light source image by the lens arrays 3 and 4 is temporally moved and averaged. Thereby, the light intensity distribution of the pupil EP in the projection optical system 8 is also smoothed, and the quality of the blurred image of the projection image is improved.

[ Reference Example 3 ]
FIG. 4 is a cross-sectional view of the main part including the central axis O of Reference Example 3 as an image projection apparatus having an illumination optical system . Compared with the reference example 1 , this reference example has a birefringent optical element (low-pass filter) 24 and a second parallel plate (parallel) that constitute the light source image moving means K4 between the polarization conversion element 5 and the condenser lens 6. Flat plate) 22 is provided, and the other configurations are the same. The same optical elements as those in the second embodiment shown in FIG.

In the present reference example , when image information based on the panel 7 is projected onto the screen S by the projection optical system 8, the second parallel plate 22 is driven by the driving means with the second axis a2 in the direction orthogonal to the optical axis O as the center. Vibrates continuously within a predetermined angle range. Thereby, the light source images by the lens arrays 3 and 4 are averaged temporally. Thereby, the light intensity distribution of the pupil EP in the projection optical system 8 is smoothed, and the quality of the blurred image of the projection image is improved. Example 1 As a configuration of the first lens array 3 in which a plurality of microlenses 3a used in Reference Example 1 to Reference Example 3 are arranged in a lattice shape, a part of the microlens 3b is polarization-converted as shown in FIG. The elements 5 may be appropriately shifted in the column direction. If such a first lens array 3 is used, it becomes easier to average the light intensity distribution on the pupil EP plane of the projection optical system 8. At this time, the second lens array 4 may be configured similarly to the first lens array 3. The image display element used in each reference example may be a transmissive type or a reflective type.

[ Reference Example 4 ]
FIG. 7 is a cross-sectional view of the main part including the central axis O of Reference Example 4 as an image projection apparatus having an illumination optical system . In FIG. 7, reference numeral 41 denotes a light source means, which is a light source that emits white light from a high-pressure mercury lamp (which may be a metal halide lamp or the like). Reference numeral 42 denotes a reflector, which is composed of a spheroid mirror (concave mirror) that efficiently reflects the light beam from the light source means 41.

  Denoted by 43 is a light beam separating means, which is made of a solid or hollow lot member, guides the light flux from the light source means 41 and forms a plurality of light source images. 43in is an incident surface of the light beam separating means 43, and 43out is an exit surface of the light beam separating means 43, both of which have a rectangular shape. Reference numeral 45 denotes a first condenser lens that condenses the light flux from the light flux separation means 43. Reference numeral 46 denotes a second condensing lens that condenses the light beam that has passed through the first condensing lens 46 and a rotatable parallel plate 49, which will be described later, and illuminates the image display element 47 by superimposing a plurality of light beams. ing. Reference numeral 48 denotes a projection optical system that projects image light on the screen S based on the image display element 47.

In this reference example , a plurality of light source images formed by a plurality of light beams separated by the light beam separation unit 43 are formed between the first condenser lens 45 and the second condenser lens 46 by the first condenser lens 45. Then, a conjugate image is formed on the exit pupil plane EP of the projection lens 48. Between the first condenser lens 45 and the second condenser lens 46, a parallel plate 49 having the same configuration as that of the reference example 2 inclined in advance with respect to the optical axis O of the condenser lens 6 is provided as the light source image moving means K3. Yes. In order to keep the illumination area in the image display element 47 constant, the central ray of the light beam emitted from the light beam separation means 43 is parallel to the optical axis O between the first condenser lens 5 and the second condenser lens 46. A so-called telecentric optical system is preferable. In FIG. 7, the first condenser lens 45 and the second condenser lens 46 are one lens, but the present invention is not limited to this.

[ Reference Example 5 ]
FIG. 8 is a cross-sectional view of the main part including the central axis O of Reference Example 5 as an image projection apparatus having an illumination optical system . The image projection apparatus of this reference example color-separates the light beam emitted from the light source means 1 and guides it to a plurality of image display elements for R, G, and B, and color-synthesizes the light from the plurality of image display elements. This is a color projector that projects with a projection optical system.

In FIG. 8, 51 is a light source (light source means) that emits white light in a continuous spectrum. A reflector 52 condenses light from the light source 51 in a predetermined direction. 53 is a first lens array, and 54 is a second lens array, each of which consists of a fly-eye lens array or a cylindrical lens array having a plurality of fine optical elements (lenses). It is divided into luminous fluxes. Reference numeral 55 denotes a polarization conversion element that emits incident non-polarized light in alignment with predetermined polarized light. K2 is a light source image moving means. The light source image moving means K2 of this reference example has the same configuration as that of the reference example 1 .

  Reference numeral 56 denotes a condensing lens, which includes a first condenser lens 56 a and a second condenser lens 56. A dichroic mirror 57 transmits green light (G) and reflects blue (B) and red (R) light. A color selective phase plate 58 converts the polarization state of red light by 90 degrees and does not convert the polarization state of blue light. 59 is a first polarizing beep splitter, and 60 is a second polarizing beep splitter, both of which are made of a prism body. Reference numerals 61, 62, and 63 denote phase plates for G, R, and B, respectively. Reference numerals 64, 65, and 66 denote G, R, and B reflective liquid crystal display elements, respectively. Reference numeral 67 denotes a color synthesis prism (color synthesis system) that synthesizes the G projection light and the B and R projection lights. Reference numeral 68 denotes a projection lens. S is a screen.

  Next, the optical action will be described. The light emitted from the light source 51 is condensed in a predetermined direction by the reflector 52. The condensed light flux from these reflectors 52 enters the first lens array 53, passes through the second lens array 54, and forms a plurality of light source images (first light emission point images) in the vicinity of the polarization conversion element 55. Form. The plurality of light beams that have undergone polarization conversion are condensed in the vicinity of the polarization conversion element 55 and then reach the condensing lens 56 through the light source image moving means K2. A plurality of light beams overlap each other at a position where a rectangular image of the first and second lens arrays 53 and 54 can be formed by the condenser lens 56 to form three rectangular illumination areas having a uniform illuminance distribution. Reflective liquid crystal display elements 64, 65, and 66 are arranged in these three illumination areas, respectively. The reflective liquid crystal display elements 64, 65 and 66 are illuminated with corresponding color lights by the color separation systems 59 and 60, respectively. Then, R, G, and B light projections based on the image information synthesized by the color synthesis system 67 are projected onto the screen S or the like by the projection lens 68 to form image information there.

Also in the present reference example , as in the first reference example , the first and second parallel plates 21 and 22 are vibrated by the light source image moving means K2. As a result, the blur when the projection lens is out of focus becomes smooth, and the image quality during focus adjustment can be greatly improved.

DESCRIPTION OF SYMBOLS 1 Light source means, 2 Reflector, 3 1st lens array, 4 2nd lens array, 5 Polarization conversion element, 6 Condensing lens, 6a 1st condenser lens, 6b 2nd condenser lens, 7 Image display element, 8 Projection optical system , K1 to K4 Light source image moving means, EP pupil, O optical axis (center axis)

Claims (2)

An illumination optical system for illuminating an image display element ,
The light of the light source or we separated into a plurality of luminous fluxes, a first lens array for forming a plurality of light source images,
A second lens array disposed closer to the image display element than the first lens array;
A polarization conversion element that aligns the polarization direction of the light emitted from the second lens array;
A focusing means for superimposing the plurality of light beams on the surface to be illuminated,
Have a light source image moving means for moving the position of the multiple light source image formed on the pupil of a projection optical system that projects the image display light modulated by the element onto a predetermined surface,
The light source image moving means includes
An optical element holding unit that holds the first lens array, the second lens array, and the polarization conversion element, and is movable in a direction perpendicular to an optical axis;
An illumination optical system characterized in that it have a driving means for moving the optical element holding portion in a direction perpendicular to the optical axis. The image display element;
The illumination optical system according to claim 1 , which illuminates the image display element;
Image projection apparatus characterized by having a projection optical system for elevation projecting the light modulated by the image display device.