JP2007079003A - Image projecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid such a trouble to the utmost that light other than light from an image projecting area is made incident on a light receiving element. <P>SOLUTION: The image projecting apparatus includes: a projection system for projecting an image 5 to a projection screen 9; and a light receiving system 4 for receiving the light from the projection screen side. The light receiving system comprises: the light receiving element 3; a light condensation optical system 2 for condensing the incident light on the light receiving element; and a light limiting member 1 for limiting the light incident on the light receiving element to only the light from the image projecting area on the projection screen. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image projection apparatus such as a liquid crystal projector, and more particularly to an image projection apparatus having a light receiving system for performing color adjustment and brightness adjustment of a projection image.

  Recent image projection apparatuses such as liquid crystal projectors are equipped with an autofocus function, an auto keystone distortion (trapezoid distortion) correction function, and the like. In addition, when the projection surface such as a wall has a color other than white, a function to perform color correction and brightness correction is also installed so that an image with the same color and brightness as that projected onto the white projection surface can be projected. It is becoming. In order to perform such color correction and brightness correction, a light receiving system (photometric system) for receiving reflected light from the image projection area on the projection surface and obtaining information on the color and brightness of the projected image is provided. Necessary.

  A conventional light receiving system includes a light receiving element that is a photoelectric conversion element and a lens that collects light from the projection surface side on the light receiving element. In many cases, the light capturing range of the light receiving system is set to be wide so as to cover the entire image projection area. FIG. 13 shows the configuration of a conventional light receiving system.

  In FIG. 13, 203 is a light receiving element, and 202 is a lens. Reference numeral 205 denotes a projected image (image projection area). Light from a range 206 wider than the projection image 205 is incident on the lens 202, and the light reaches the light receiving element 203.

Such a photometric technique is used in an imaging apparatus such as a camera unless it is limited to the field of liquid crystal projectors (for example, Patent Document 1).
Japanese Patent Laid-Open No. 06-258691

  However, the conventional light receiving system is not provided with a diaphragm for limiting the light incident on the lens 202. For this reason, as shown in FIG. 13, when a light emitter 207 such as an electric lamp exists in the vicinity of the projection image 205 on the projection surface, the light from the light emitter 207 also passes through the lens 202 to the light receiving element 203. Incident. In this case, a noise component corresponding to the light from the light emitter 207 is included in the output from the light receiving element 203. Therefore, even if the color and brightness of the projected image are controlled based on the output, the output is appropriate. Control is not possible. The same applies not only to the light emitter 203 but also when a non-light-shielded window exists near the projection surface.

  One object of the present invention is to provide an image projecting apparatus having a light receiving system capable of avoiding light other than light from an image projecting region from entering a light receiving element as much as possible.

  An image projection apparatus according to one aspect of the present invention includes a projection system that projects an image on a projection surface and a light receiving system that receives light from the projection surface side. The light receiving system includes a light receiving element, a condensing optical system that condenses incident light on the light receiving element, and a light limiting member that restricts light incident on the light receiving element to light from the image projection area of the projection surface. It is configured.

  According to the present invention, it is possible to block light from a light emitter, a window, or the like existing near the image projection area by the light limiting member, and to allow only light from the image projection area to enter the light receiving element. Therefore, appropriate color correction and brightness correction of the projected image can be performed based on the output from the light receiving element.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows the configuration of a liquid crystal projector that is Embodiment 1 of the present invention. The projector of this embodiment includes a light source unit 100, an illumination optical system α, a color separation / synthesis optical system β, reflective liquid crystal display elements (liquid crystal panels) 111r, 111g, and 111b as image forming elements, and a projection lens 113. It consists of. The light source unit 100, the illumination optical system α, the color separation / synthesis optical system β, the reflective liquid crystal display elements 111r, 111g, 111b, and the projection lens 113 constitute an image projection system.

  An arc tube 101 emits white light with a continuous spectrum, and a reflector 102 condenses light from the arc tube 101 in a predetermined direction. A light source unit 100 is configured by the arc tube 101 and the reflector 102. AXL is an optical axis of the illumination optical system α, the color separation / synthesis optical system β, and the projection lens 150, and indicates the traveling direction of light from the light source unit 100.

  103 is a first cylindrical lens array constituted by a plurality of cylindrical lenses having refractive power in a direction parallel to the paper surface of FIG. 1, and 104 is a plurality of cylindrical lenses corresponding to the individual lenses of the first cylindrical lens array 103. Is a second cylindrical lens array.

  Reference numeral 105 denotes a polarization conversion element that aligns non-polarized light with predetermined polarized light, 115 denotes a mirror, and 116 denotes a condenser lens.

  A dichroic mirror 106 reflects blue (B: 430 to 495 nm) and red (R: 590 to 650 nm) light, and reflects green (G: 505 to 580 nm) light. Reference numeral 107 denotes a color filter that partially cuts light in the intermediate wavelength region between G light and R light. Reference numerals 108a and 108b denote a first color selective phase difference plate and a second color selective phase difference plate that convert the polarization direction of the B light by 90 degrees and do not convert the polarization direction of the R light.

  109a and 109b are a first half-wave plate and a second half-wave plate. Reference numerals 110a, 110b, and 110c denote a first polarization beam splitter, a second polarization beam splitter, and a third polarization beam splitter that transmit P-polarized light and reflect S-polarized light.

  Reference numerals 111r, 111g, and 111b denote a red reflective liquid crystal panel, a green reflective liquid crystal panel, and a blue reflective liquid crystal panel that form an original image, reflect incident light, and modulate the image. Here, a drive circuit 120 is connected to the liquid crystal panels 111r, 111g, and 111b, and an image from an image information supply device 130 such as a personal computer, a camera, a DVD player, a video deck, or a broadcast receiver is connected to the drive circuit 120. Information is supplied. The drive circuit 120 drives the liquid crystal panels 111r, 111g, and 111b based on the input image information, and forms an original image for each color corresponding to the image information.

  112r, 112g, and 112b are a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue, respectively. The optical system constituting the optical path from the dichroic mirror 106 to the third polarizing beam splitter 110c is a color separation / synthesis optical system β that performs color separation and color synthesis of light. Reference numeral 113 denotes a projection lens.

  Next, the optical action will be described. Light emitted from the arc tube 101 is collected in a predetermined direction by the reflector 102. The reflector 102 has a paraboloid shape, and light from the focal position of the paraboloid becomes a light beam parallel to the symmetry axis of the paraboloid. The parallel light flux is divided into a plurality of light fluxes by the first lens array 103 and condensed, and a plurality of light source images are formed in the vicinity of the second lens array 104 to reach the polarization conversion element 105.

  The polarization conversion element 105 includes a polarization separation surface, a reflection surface, and a half-wave plate in order from the incident side. The condensed light flux of each column of the matrix that has entered the polarization conversion element 105 is incident on the polarization separation surface of the column corresponding to that column, and is divided into a P-polarized component that transmits this and a S-polarized component that reflects. The reflected S-polarized component is reflected by the reflecting surface and is emitted in the same direction as the P-polarized component. On the other hand, the transmitted P-polarized light component is converted to the same polarized light component as the S-polarized light component when passing through the half-wave plate, and is emitted as light having the same polarization direction (here, S-polarized light). The plurality of light beams that have undergone polarization conversion are condensed in the vicinity of the polarization conversion element, and then reach the condenser lens 116 via the mirror 115 as divergent light beams.

  Due to the condensing action of the condenser lens 116, the plurality of light beams overlap at positions where images corresponding to the shapes of the individual cylindrical lenses in the first and second cylindrical lens arrays 103 and 104 are formed, and a rectangular uniform illumination area Form. The light beam emitted from the condenser lens 116 enters the dichroic mirror 106. The dichroic mirror 106 transmits B and R light and reflects G light.

  In FIG. 1, S-polarized light emitted from the polarization conversion element 104 is also S-polarized light with respect to the dichroic mirror 106.

  In the optical path of G light, the light reflected from the dichroic mirror 106 enters the color filter 107. The color filter 107 is a dichroic filter that reflects yellow light in an intermediate wavelength region between G and R, thereby removing yellow light. If there are many yellow components in green, it will become yellowish green, so it is desirable for color reproduction to remove the yellow components by the color filter 107. The color filter 107 may have a characteristic of absorbing yellow light.

  The G light whose color has been adjusted in this way enters the first polarization beam splitter 110a as S-polarized light, is reflected by the polarization separation surface, and reaches the G-use reflective liquid crystal panel 111g. In the G reflective liquid crystal panel 111g, the G light is image-modulated and reflected. Of the modulated and reflected G light, the S polarization component is reflected again by the polarization separation surface of the first polarization beam splitter 110a, returned to the light source side, and removed from the projection light.

  On the other hand, the P-polarized component of the modulated and reflected G light is transmitted through the polarization separation surface of the first polarization beam splitter 110a to become projection light. At this time, in a state where all the polarization components are converted to S-polarized light (in a state where black is displayed), the quarter-wave plate 112g provided between the first polarizing beam splitter 110a and the G-use reflective liquid crystal panel 111g A slow axis that is one of the birefringent main axes is adjusted in a predetermined direction. Thereby, the influence of the disturbance of the polarization state generated in the first polarizing beam splitter 110a and the G-use reflective liquid crystal panel 111g can be reduced.

  The G light as P-polarized light that has passed through the first polarizing beam splitter 110a is rotated by 90 degrees in the polarization direction by the first half-wave plate 109a and is incident on the third polarizing beam splitter 110c as S-polarized light. . Thus, the G light incident on the third polarization beam splitter 110 c is reflected by the polarization separation surface and reaches the projection lens 113.

  On the other hand, the R and B lights transmitted through the dichroic mirror 106 are incident on the first color-selective phase difference plate 108a. The first color-selective retardation plate 108a has an action of rotating the polarization direction by 90 degrees only for B light. Thus, the B light is incident on the second polarization beam splitter 110b as P-polarized light and the R light is incident on S-polarized light. Then, the B light passes through the polarization separation surface of the second polarization beam splitter 110b, and reaches the B reflection type liquid crystal panel 111b via the quarter wavelength plate 112b. The R light is reflected by the polarization splitting surface and reaches the R reflective liquid crystal panel 111r via the quarter-wave plate 112r.

  In the reflective liquid crystal panel 111b for B, the B light is image-modulated and reflected. Of the modulated B light, the P-polarized light component is again transmitted through the polarization separation surface, returned to the light source side, and removed from the projection light. Of the modulated B light, the S-polarized light component is reflected by the polarization separation surface and becomes projection light.

  Similarly, R light is image-modulated and reflected by the R reflective liquid crystal panel 111r. Of the modulated R light, the S polarization component is reflected again by the polarization separation surface, returned to the light source side, and removed from the projection light. In addition, the P-polarized component of the modulated R light is transmitted through the polarization separation surface and becomes projection light. Thereby, the projection light of B and R is combined into one light beam.

  The combined B and R projection light is incident on the second color selective phase difference plate 108b. The second color selective phase difference plate 108b is the same as the first color selective phase difference plate 108a and rotates only the polarization direction of the B light by 90 degrees. As a result, both the R light and the B light are incident on the third polarization beam splitter 110c as P-polarized light, pass through the polarization separation surface, and are combined with the G projection light to reach the projection lens 113. Then, the light is projected onto a projection surface such as a screen by the projection lens 113.

  The drive circuit 120 is connected with a correction circuit 140 as adjustment means, and the correction circuit 140 is connected with a light receiving unit 4 constituting a light receiving system.

  The light receiving unit 4 includes, in order from the image projection side indicated by an arrow A in the drawing, a diaphragm 1 as a light limiting member, a condensing lens 2 constituting a condensing optical system, and a light receiving element (hereinafter referred to as a photoelectric conversion element). , Referred to as a sensor) 3. Light that has entered the light receiving unit 4 through the light passage opening 1 a of the diaphragm 1 from the image projection side is condensed by the condenser lens 2 and reaches the sensor 3. The photoelectric conversion output from the sensor 3 is input to the correction circuit 140.

  The correction circuit 140 controls the reflective liquid crystal display elements 111r, 111g, and 111b through the driving circuit 120 so as to correct (adjust) the color and brightness of the image projected on the projection surface based on the output from the sensor 3. To do. Specifically, when the projection surface has a color other than white, the color and brightness of the projected image are corrected so that an image with the same color and brightness as that projected onto the white projection surface is displayed. To do.

  Hereinafter, the light receiving unit 4 will be described in detail with reference to FIG. In this figure, 113 is the projection lens described above, and 111 is a reflective liquid crystal panel. Reference numeral 5 denotes an image (projected image) projected onto the projection surface 9 (here, in particular, a wall surface having a color other than white) by the projection lens 113.

  The light receiving unit 4 takes in light emitted from the projection lens 113 and reflected by the projection surface 9. The light receiving unit 4 includes a diaphragm 1, a condenser lens 2, and a sensor 3 arranged in this order from the image projection side (projection surface 9 side). The optical axis 7 of the condenser lens 2 faces the center 8 of the projection image 5 on the projection surface 9.

  A diaphragm aperture 1a is formed in the diaphragm 1 as a light passage aperture. When viewed from the projection surface side, the aperture opening 1a has an opening width of L1 in the horizontal direction (first direction) and an opening width of L2 shorter than L1 in the vertical direction (second direction). It is formed in a rectangle.

  As shown in FIG. 2, the aperture 1 a has a size that allows only the reflected light from the predetermined range 6 in the area (image projection area) of the projection surface 9 on which the image 5 is projected to pass toward the sensor 3. Is formed. That is, the diaphragm 1 has a function of limiting light incident on the sensor 3 to only light from the image projection area.

  3 and 4 show a horizontal section and a vertical section of the light receiving unit 4, respectively. The horizontal direction is a direction corresponding to the long side direction of the projection image 5 and is parallel to the long side of the projection image 5 (for example, front projection shown in the figure or oblique projection from the vertical direction) The in-plane direction of the surface including the long side of the projection image 5 (for example, in the case of oblique projection from the side) is included. The horizontal direction can also be said to be a direction corresponding to the long side direction of the reflective liquid crystal panel 111, that is, a direction parallel to the long side of the liquid crystal panel 111 or an in-plane direction of a plane including the long side.

  Further, the vertical direction is a direction corresponding to the short side direction of the projection image 5 and includes a direction parallel to the short side of the projection image 5 and an in-plane direction of the plane including the short side of the projection image 5. It can be said that the vertical direction is a direction corresponding to the short side direction of the reflective liquid crystal panel 111, that is, a direction parallel to the short side of the liquid crystal panel 111 or an in-plane direction of a plane including the short side.

  As described above, since the aperture opening 1a is formed in a rectangle having a long side in the horizontal direction, the light capturing range of the sensor 3 (the angle of view indicated by a solid line in FIGS. It is wide in the long side direction and narrow in the short side direction.

  FIG. 5 shows the light capturing range 6 of the sensor 3 in the image projection area in more detail. The sensor 3 captures light from as wide a range as possible without protruding the image projection area (indicated by reference numeral 5 in FIG. 5). The capture range 6 is preferably a range having an area of 1/3 or more of the area of the image projection area. This is because it is difficult to detect the overall brightness and color of the projected image even if light from a narrower range is captured.

  In other words, it is possible to appropriately control the overall brightness and color of the projected image by capturing light from a range having an area of 1/3 or more of the area of the image projection region.

  In the present embodiment, light from a range 6 having an area of 1/3 or more of the image projection area when the maximum image is projected with the projection lens 113 at the wide end (Wide) by the zoom function at a predetermined projection distance is captured. The size of the aperture 1a is set so that

  However, the size of the aperture 1a is set so that light from a range having an area of 1/3 or more of the image projection area when the minimum image is projected with the projection lens 113 as the telephoto end (Tele) can be captured. May be. The reason for this will be described in Example 4 described later.

  The predetermined projection distance is set to the most general distance in which the projector is used. Further, in this embodiment, the position of the diaphragm 1 is fixed, but the diaphragm 1 can be moved in the optical axis direction of the light receiving unit 4 so that it does not protrude from the image projection area according to the size of the projected image. It may be possible to select a light capturing range as wide as possible.

  Furthermore, FIG. 6 shows the configuration of the sensor 3 in the present embodiment. On the sensor 3, an R light receiving portion 3r, a G light receiving portion 3g, and a B light receiving portion 3b are arranged in the horizontal direction. By using such a sensor 3, the brightness of each of the R light component, the G light component, and the B light component contained in the reflected light from the image projection area (that is, the color of the entire image) is detected. be able to.

  Here, as shown in FIGS. 3 and 4, the sensor 3 is disposed at a position closer to the condenser lens 2 than the focal position 2 a of the condenser lens 2. That is, an image that is out of focus is formed on the sensor 3. Therefore, the light capturing ranges (R, G, B) of the R light receiving unit 3r, the G light receiving unit 3g, and the B light receiving unit 3b on the image projection area overlap each other as shown in FIG. The range is slightly shifted in the horizontal direction. Thereby, the brightness of R, G, and B in the common range C within the image projection area can be detected. In FIG. 6, for the sake of explanation, the light capturing ranges of the respective light receiving units are illustrated as being largely shifted, but in reality, most of them overlap each other.

  If the sensor 3 is disposed on the focal position 2a of the condensing lens 2, the light receiving ranges of the R light receiving unit 3r, the G light receiving unit 3g, and the B light receiving unit 3b on the image projection area are over each other. The range is adjacent in the horizontal direction without wrapping. For this reason, it is possible to detect only the brightness of R, G, and B in different ranges within the image projection area.

  Specifically, it is desirable to satisfy the condition shown by the following formula (1).

1.0 ≦ La / Ls ≦ 3.0 (1)
Here, Ls is a distance from the sensor 3 to the condenser lens 2 (in the third embodiment described later, a concave mirror 12). La is the distance from the condenser lens 2 to the stop 1.

  When La / Ls falls below the lower limit value of the expression (1), the diaphragm 1 becomes too close to the lens 2 and the function of the diaphragm 1 that restricts the light incident on the sensor 3 to only the light from the image projection area is sufficient. Can't be done. On the other hand, if La / Ls exceeds the upper limit of the expression (1), the light receiving unit 4 is undesirably enlarged.

  Here, the light from the image projection area (reflected light) includes a projection surface of image light emitted from the projection lens 113 to display the projection image 5 and light from a room lamp or window in which the projector is used. 9 reflected light (external light). The light receiving unit 4 (sensor 3) takes in light from the image projection area including these image light and external light. For this reason, when it is desired to detect only image light, external light is measured by the light receiving unit 4 without projecting an image, and the measurement result is subtracted from the measurement result of (image light + external light). That's fine.

  The correction circuit 140 described above controls the brightness of the image light so that the value of (brightness of image light) / (image light + brightness of external light) falls within a predetermined range, that is, the liquid crystal panels 111r and 111g. , 111b are controlled. Thereby, it is possible to display a projection image having appropriate brightness with respect to the original brightness of the projection surface 9.

  In addition, the correction circuit 140 controls the liquid crystal panels 111r, 111g, and 111b so that the color of the image light + external light is equivalent to that when the projection surface 9 is white. Thereby, it is possible to obtain a projection image of a natural color regardless of the color of the projection surface 9.

  In the present embodiment, the case where the diaphragm 1 has the rectangular diaphragm opening 1a has been described, but the shape of the diaphragm opening 1a is not limited to this. For example, as shown in FIGS. 7 and 8, it may be an ellipse or a polygon such as an octagon. However, in any shape, it is desirable that the horizontal opening width L1 is larger than the vertical opening width L2.

  In the first embodiment, the case where the R light receiving unit 3r, the G light receiving unit 3g, and the B light receiving unit 3b are arranged in the horizontal direction (the direction corresponding to the long side direction of the projection image 5) in the sensor 3 has been described. . However, as shown in FIG. 9, the R light receiving unit 3r, the G light receiving unit 3g, and the B light receiving unit 3b may be arranged in a vertical direction (a direction corresponding to the short side direction of the projection image 5).

  More specifically, since each light receiving portion has a rectangular shape that is long in the horizontal direction, the light receiving portions 3r and G for R are used after the long side direction is matched with the direction corresponding to the long side direction of the projection image 5. The light receiving unit 3g and the B light receiving unit 3b are arranged in the vertical direction. Accordingly, the common light capturing range C in which the light capturing ranges of the R light receiving unit 3r, the G light receiving unit 3g, and the B light receiving unit 3b overlap each other is made longer in the horizontal direction than in the first embodiment. be able to. That is, it is possible to ensure a common light capturing range C that is wider in the horizontal direction within the horizontally long image projection region.

  In FIG. 9, the light capturing ranges of the respective light receiving units are shown to be greatly shifted for the sake of explanation, but in reality, most of them overlap each other.

  FIG. 10 shows the configuration of a light receiving unit 4 ′ in a liquid crystal projector that is Embodiment 3 of the present invention. The overall configuration of the liquid crystal projector of this embodiment is the same as that of the first embodiment.

  The light receiving unit 4 ′ of the present embodiment is configured by arranging a diaphragm 1, a concave mirror 12, and a sensor 3 in order from the image projection side (projection surface 9 side). The optical axis 7 on the incident side of the concave mirror 12 faces the center 8 of the projection image 5 on the projection surface 9.

  In the present embodiment, the concave mirror 12 is used as the condensing optical system of the light receiving unit 4 ′, and the optical path toward the sensor 3 is bent. Thereby, compared with the case where a lens is used like Example 1, light-receiving unit 4 'can be reduced in size.

  In this embodiment, the optical path is bent in the direction corresponding to the short side direction of the projection image 5 by the concave mirror 12, but it may be bent in the direction corresponding to the long side direction of the projection image 5.

  As in the first embodiment, the diaphragm 1 is formed with a diaphragm opening 1a as a light passage opening. When viewed from the projection surface side, the aperture opening 1a has an opening width of L1 in the horizontal direction corresponding to the long side direction of the projection image 5, and is larger than L1 in the vertical direction corresponding to the short side direction of the projection image. It is formed in a rectangle having a short opening width of L2. Further, as shown in FIG. 10, the aperture 1 a is large enough to allow only reflected light from the predetermined range 6 in the area (image projection area) of the projection surface 9 on which the image 5 is projected to pass toward the sensor 3. Is formed. That is, the diaphragm 1 has a function of limiting light incident on the sensor 3 to only light from the image projection area.

  In this embodiment, as shown in FIG. 11, the light capturing range 6 of the sensor 3 is set to the size of the projection image 14 in the middle area between the wide end and the tele end of the projection lens 113. It is matched. Although not shown, the arrangement direction of the R, G, B light receiving parts on the sensor 3 is the same as the arrangement direction shown in FIG. However, the arrangement direction shown in FIG.

  FIG. 11 shows the light capturing range of the light receiving unit (sensor) in the liquid crystal projector that is Embodiment 4 of the present invention. The configuration of the liquid crystal projector and the configuration of the light receiving unit in the present embodiment are the same as those in the first and second embodiments. However, in this embodiment, the light capturing range of the sensor 3 is matched with the size of the minimum image 11 when the projection lens 70 is zoomed to the telephoto end.

  By zooming the projection lens 113 to the telephoto end, the projection image 5 becomes brighter and the amount of image light incident on the sensor 3 can be increased as compared to zooming to the wide end or middle range.

  Further, by matching the light capture range to the minimum image 11 at the tele end, the unnecessary light component around the projection image is compared with the case where the light capture range is matched to the maximum image at the wide end and the intermediate image in the middle range. The influence can be reduced.

  In each of the above embodiments, the case where the diaphragm 1 is disposed on the image projection side with respect to the condensing optical system has been described. However, the diaphragm 1 may be disposed between the condensing optical system and the sensor 3.

1 is a cross-sectional view illustrating a configuration of a liquid crystal projector that is Embodiment 1 of the present invention. FIG. 2 is a schematic diagram illustrating a configuration of a light receiving unit provided in the liquid crystal projector of Embodiment 1 and a shape of a diaphragm that forms the light receiving unit. FIG. 3 is a horizontal sectional view of the light receiving unit according to the first embodiment. FIG. 3 is a vertical sectional view of the light receiving unit according to the first embodiment. FIG. 3 is a diagram illustrating a light capturing range of the light receiving unit according to the first embodiment. FIG. 3 is a diagram illustrating a configuration of a sensor provided in the light receiving unit according to the first embodiment and a light capturing range of each color light receiving unit. FIG. 6 is a diagram illustrating a modification of the diaphragm provided in the light receiving unit according to the first embodiment. FIG. 6 is a diagram illustrating a modification of the diaphragm provided in the light receiving unit according to the first embodiment. FIG. 6 is a diagram illustrating a sensor configuration of a light receiving unit provided in a liquid crystal projector that is Embodiment 2 of the present invention and a light capturing range of each color light receiving unit. FIG. 6 is a schematic diagram illustrating a configuration of a light receiving unit provided in a liquid crystal projector that is Embodiment 3 of the present invention and a shape of a diaphragm that forms the light receiving unit. FIG. 10 is a diagram illustrating a light capturing range of the light receiving unit according to the third embodiment. FIG. 10 is a diagram illustrating a light capturing range of a light receiving unit provided in a liquid crystal projector that is Embodiment 4 of the present invention. The figure which shows the structure of the light-receiving unit provided in the conventional liquid crystal projector, and the light taking-in range.

Explanation of symbols

1 Aperture 2 Condensing Lens 3 Light Receiving Element (Sensor)
4 Light receiving unit 5 Projected image (image projection area)
6 Light capture range (of sensor) 9 Projection surface 12 Concave mirror 100 Light source unit 111r, 111g, 111b Reflective liquid crystal panel 113 Projection lens α Illumination optical system β Color separation / synthesis optical system

Claims (9)

An image projection system for projecting an image onto the image projection area of the projection surface;
A light receiving system for receiving light from the projection surface side,
The light receiving system includes a light receiving element, a condensing optical system that condenses incident light on the light receiving element, and a light limiting member that restricts light incident on the light receiving element to light from the image projection region. An image projection apparatus characterized by that.   The image projection apparatus according to claim 1, wherein the light limiting member is provided at a position farther to the image projection side than the condensing optical system.   The image projection apparatus according to claim 1, wherein the light receiving element is disposed at a position closer to the condensing optical system than a focal position of the condensing optical system. The image projection apparatus according to claim 2, wherein the following condition is satisfied.
1.0 ≦ La / Ls ≦ 3.0
However, Ls is a distance from the light receiving element to the condensing optical system, and La is a distance from the condensing optical system to the light limiting member. The light limiting member has a light passage opening whose opening width in the first direction is larger than the opening width in the second direction orthogonal to the first direction;
5. The image projection apparatus according to claim 1, wherein the first direction is set to correspond to a long side direction of a projection image.   The said light limiting member allows the light from the part which has an area more than 1/3 of the area of the said image projection area | region to pass through, The any one of Claim 1 to 5 characterized by the above-mentioned. Image projection device. The projection system has a zoom function,
The image projection apparatus according to claim 1, wherein the light limiting member allows light from the image projection area minimized by the zoom function to pass therethrough. The light receiving element has light receiving areas for red, green and blue,
8. The image projection apparatus according to claim 1, wherein the light receiving areas are arranged in a direction corresponding to a short side direction of the projection image.   The image projection apparatus according to claim 1, further comprising an adjustment unit that performs color adjustment or brightness adjustment of a projection image based on an output from the light receiving element.