JP2015055819A - Scanning projection display optical system and scanning projection display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scanning projection display optical system that is a simple optical system and has high resolving power, high use efficiency of a light source and a wide color reproduction range.SOLUTION: The scanning projection display optical system includes: a light source having a white light source 1; a spatial optical modulation element 5 that receives white light, spatially and temporally modulates the incident white light on the basis of an image signal in accordance with an image to be displayed, and outputs the modulated light; a planar reflective diffraction grating 7 that allows the modulated light to exit in different directions depending on wavelengths; an illumination optical system 4 that condenses the light from the planar reflective diffraction grating 7; a slit member 9 that is disposed at a conjugate position of the illumination optical system to the planar reflective diffraction grating 7 and projects a one-dimensional image of an incident image formed by superposing light in different wavelength regions spectrally separated at different positions on the spatial optical modulation element; a scanning mirror 11 that is synchronously operated with modulation of the spatial optical modulation element 5 to scan the exiting light from the slit to form a scanned image as a two-dimensional image; and a projection optical imaging lens 12 for projecting the scanned image from the scanning element onto a projection screen.

Description

  The present invention relates to a scanning projection display optical system that includes a white light source, a spectroscopic element, and a two-dimensional modulation element to generate a hyperspectral image, and a scanning projection display apparatus that projects this image.

  A technique has been proposed in which a hyperspectral image, that is, an image of a large number of wavelength channels (for example, 30 channels or more) is combined to display an image in a wide color region. Conventionally, the following have been proposed as scanning projection display optical systems and scanning projection display apparatuses for displaying hyperspectral images. In Patent Document 1 and Patent Document 2, a linear white light source or a secondary light source is spectrally dispersed with a spectroscopic element, imaged on the spatial modulation element, spatially modulated, and then spatially modulated using the spectroscopic element. There is described a technique for recombining light to create a slit-like image.

  Patent Document 3 describes a technique in which a white light source or a secondary light source is dispersed with a spectroscopic element, and a two-dimensional spatial modulator is illuminated with a light beam scanned with a galvanometer mirror to obtain a two-dimensional hyperspectral image. Has been.

  Non-Patent Document 1 is from the United States NIST (National Institute of Standards and Technology), and changes the wavelength sequentially using a so-called programmable light source, which is a light source whose spectral distribution can be freely controlled, as an illumination light source. Illuminates a two-dimensional modulation element and projects it. This replaces the color wheel of a single-plate DMD projector with a programmable light source.

Japanese Patent Laid-Open No. 2011-90061 JP-2011-90261 A JP-2012-123061 A

SPIE Proceeding Vol. 6297 629701

  However, those described in Patent Document 1 and Patent Document 2 have a problem in that efficiency decreases because the spectroscopic element is used twice. In addition, in order to recombine and create an image at the same position, the optical system is complicated, and high-precision manufacturing and assembly are required.

  The one described in Patent Document 3 is advantageous in terms of transmittance with a single spectroscopic element, but compared with scanning a one-dimensional hyperspectral image when scanning the entire image in the entire wavelength region. Thus, it takes more than twice as much time, and the time average brightness is less than half.

  Furthermore, the thing of a nonpatent literature 1 needs to synchronize two two-dimensional modulation elements, and has the following problems. Since the number of times of switching is frame rate × number of wavelengths × number of gradation generation frames, in a hyperspectral display with a large number of wavelengths, a practical two-dimensional modulation element can only use DMD at present. In a normal DMD projector, the gradation of one primary color is determined by the time during which the DMD (registered trademark: Digital Micromirror Device) is on. However, in the case of a hyperspectral display having one digit number of wavelength channels, the switch speed becomes insufficient even with DMD.

  For this reason, the device described in Non-Patent Document 1 is synchronized with the DMD for creating an image by sequentially reducing the light amount by 1/2 for each primary color. As a result, the number of times of switching for gradation expression is reduced. For example, in order to express 1024 gradations, the normal method switches to 1024 times, but decreases to 10 times. However, as a result, the maximum amount of light decreases. For example, it becomes about 1/4 for 1024 gradations. The synchronization accuracy of the DMD for illumination and image creation needs to be sufficiently high with respect to the switching time. In addition, the amount of light is wasted in order to illuminate the DMD twice.

  In order to create a two-dimensional hyperspectral image by scanning the slit image, it is desirable to use a DMD that is a high-speed spatial modulator. This element is switched when the mirror creates a state of ± 10 degrees or ± 12 degrees. Further, the rotation axis of the mirror is usually deviated by 45 degrees from the horizontal or vertical of the DMD. When used in a projector, illumination light is incident from the direction of 45 degrees with azimuth and the direction of 70 degrees or 66 degrees with elevation, and the imaging optical system is arranged in the vertical direction. However, it is difficult to create a spectral image that is incident in this direction and is split in the X or Y direction on the DMD, and it is more difficult to re-synthesize with the imaging optical system, and an optical system with high resolving power is difficult. It is.

  As described above, in the creation of a hyperspectral image, the wavelength half-value width of each primary color is narrow, so that the amount of light that can be used is reduced in principle compared to a three-primary color image creation device. In order to obtain a sufficiently bright image with a practically sized image, the efficiency is low in the conventional method.

  Accordingly, an object of the present invention is to provide a scanning projection display optical system and a scanning projection display apparatus that have a simple optical system, high resolution, high light source utilization efficiency, and a wide color reproduction range. And

  The invention according to claim 1, which solves the above-mentioned problem, spatially and irradiates the white light incident on the basis of an image signal based on an image signal based on an image to be displayed, and a light source that emits white light. Spatial light modulation element that outputs temporally modulated light, a spectroscopic element that emits the modulated light in different directions for each wavelength, an illumination optical system that collects light from the spectroscopic element, and the illumination optics A slit member that is arranged at a conjugate position with respect to the spectroscopic element of the system, and emits a one-dimensional image of the image that is incident by superimposing the light of different wavelength regions dispersed at different positions of the spatial light modulator; A scanning element that operates in synchronization with the modulation of the spatial light modulation element, scans the light emitted from the slit to generate a scanned image forming a two-dimensional image, and the scanned image from the scanning element is projected onto the projection surface. Project Is a scanning projection display optical system comprising: the projection optical element.

  Similarly, the invention according to claim 2 is the scanning projection display optical system according to claim 1, wherein the spatial light modulation element includes a plurality of micromirrors, and performs light modulation by changing the direction of the micromirrors. It is a reflective element.

  Similarly, the invention according to claim 3 is the scanning projection display optical system according to claim 1 or 2, wherein the scanning element is a plane reflection type diffraction grating, and a condensing optical element is provided in the lower stage. It is characterized by.

  Similarly, the invention according to claim 4 is the scanning projection display optical system according to claim 1 or 2, wherein the scanning element is a concave reflection type diffraction grating.

  Similarly, the invention according to claim 5 drives the spatial light modulator based on the scanning projection display optical system according to any one of claims 1 to 4 and the input image data. A modulation signal and a scanning signal for driving the scanning element are generated, and the modulation signal and the scanning signal are synchronously output so that a two-dimensional image is output to the spatial light modulation element and the scanning element based on the image data. And a projection control unit.

  The scanning projection display optical system and the scanning projection display apparatus according to the present invention have a simple structure, high resolution, high use efficiency of the light source, and a wide color reproduction range.

It is an optical path diagram which shows the scanning projection display optical system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the control system of the scanning projection display apparatus. It is an optical path diagram which shows the scanning projection display optical system which concerns on Embodiment 2 of this invention.

  A scanning projection display optical system and a scanning projection display apparatus according to embodiments for carrying out the present invention will be described. The scanning projection display apparatus according to the present embodiment generates a hyperspectral projection image by superimposing color images of, for example, 30 wavelength regions (primary colors).

<Embodiment 1>
First, the scanning projection display optical system will be described. A scanning projection display optical system according to Embodiment 1 of the present invention includes a white light source 1, which is a light source, an elliptical mirror 2, a light pipe 3, an illumination optical system 4, a reflective spatial light modulation element 5, Is provided. The scanning projection display optical system includes a spectroscopic optical system collimator lens 6, a plane reflection type diffraction grating 7 that is a spectroscopic element, a spectroscopic optical system imaging lens 8 that is a condensing optical element arranged in the lower stage, A slit member 9, a projection optical system collimator lens 10, a scanning mirror 11, and a projection optical system imaging lens 12 are provided. Reference numeral 13 in FIG. 1 denotes a screen which is a projection plane.

  The white light source 1 is a xenon lamp, for example, and is disposed at one focal point of the elliptical mirror 2. The incident end of the light pipe 3 is disposed at the other focal point of the elliptical mirror 2, and the light from the white light source 1 is incident on the incident end of the light pipe 3 with high efficiency. If the light pipe 3 is appropriately designed, the light becomes uniform at the exit end due to the mixing effect. The exit end of the light pipe 3 and the spatial light modulation element 5 are arranged at a conjugate position of the illumination optical system 4. Thereby, the spatial light modulation element 5 can be illuminated uniformly. The illumination optical system 4 is composed of a lens having a positive power, and collects light from the light pipe 3.

  The spatial light modulator 5 outputs modulated light obtained by spatially and temporally modulating the incident white light based on an image signal based on an image to be displayed. As the spatial light modulator 5, DMD (registered trademark: Digital Micromirror Device) can be used. The DMD is a reflective element that performs spatial light modulation by arranging a large number of micromirror surfaces (micromirrors) on a plane and independently controlling the angle state of each micromirror. The angle of each micromirror can be changed to ± 10 degrees or ± 12 degrees from the non-tilt state. When the micromirror is tilted by 12 degrees, the illumination optical system 4 is incident from a direction of 24 degrees from the normal line of the spatial light modulator 5. Thereby, the light is reflected in the normal direction in the on state, and is reflected in the direction of 48 degrees from the normal in the off state.

  The spatial light modulator 5 corresponds to a micromirror in which one pixel of an image to be projected has, for example, “8 × 3” as one unit. The gradation of the display pixel is controlled by controlling the number of micromirrors for one pixel that are turned on. The spatial light modulator 5 is arranged in the number corresponding to the number of units of micromirrors for displaying gradation for one pixel. Here, the unit row of the micromirrors arranged at the position along the horizontal direction in FIG. 1 of the spatial light modulator 5 corresponds to one of the 30 primary colors. Therefore, the number of units in the direction perpendicular to the paper surface corresponds to the number of horizontal pixels of the projected image. The number of vertical pixels is determined by the time modulation frequency of the input modulation data and the scanning frequency of the scanning mirror 11.

  The spectroscopic optical system collimator lens 6 converts the ON light beam emitted from the spatial light modulator 5 into a parallel light beam, and irradiates the plane reflection diffraction grating 7. The plane reflection type diffraction grating 7 is formed with a large number of gratings along the direction perpendicular to the paper surface in FIG. Therefore, the incident modulated light is emitted at different angles along the paper surface in FIG. 1 according to the wavelength. The diffracted light diffracted by the plane reflection diffraction grating 7 forms an image on the slit member 9 by the spectroscopic optical system imaging lens 8. The slit member 9 includes a slit groove perpendicular to the paper surface in FIG. 1 and is disposed at a conjugate position of the plane reflection type diffraction grating 7 in the spectroscopic optical system imaging lens 8. As a result, diffracted light from all different positions of the spatial light modulator 5, that is, light in different wavelength regions (color channels) from different positions of the spatial light modulator 5 enters the slit member 9. The wavelength of light incident on the slit member 9 differs depending on the position of the spatial light modulator 5. The gap width of the slit member 9 is preferably set to a size that allows the visible spectrum width from the plane reflection type diffraction grating 7 to be emitted in 30 wavelength regions.

A specification example of each optical element of the scanning projection display optical system according to the embodiment is as follows.
White light source 1 wavelength region: 430 to 730 nm
Number of micromirrors of the spatial light modulator 5: 1024 × 768 (SXGA)
Lattice constant of the plane reflection type diffraction grating 7: 300 L / mm 2, size □ 50
The numerical aperture and length of the slit member 9: 0.11 mm × 11 mm
Prediction angle of scanning mirror 11: ± 2 degrees, speed 60 Hz

  With such a configuration, when the micromirror unit of the spatial light modulator 5 at a position corresponding to the wavelength region is turned on, diffracted light for the desired wavelength region can be incident on the slit member 9, and A one-dimensional hyperspectral image can be created. The plane reflection type diffraction grating 7 has a lattice constant determined so as to emit the first-order diffracted light toward the slit member 9.

  The projection optical system collimator lens 10 which is a projection optical element is configured as a lens having a positive power for converting the light emitted from the slit member 9 into parallel light. The scanning mirror 11 is composed of, for example, a galvanometer mirror, and performs a scanning operation in synchronization with the modulation of the spatial light modulation element. As a result, the one-dimensional hyperspectral image is scanned into a two-dimensional image. The projection optical system imaging lens 12 projects this two-dimensional image onto the screen 13, and a two-dimensional hyperspectral image is projected onto the screen 13.

  Next, the scanning projection display apparatus according to the first embodiment will be described. The scanning projection display apparatus drives and controls the spatial light modulation element 5 and the scanning mirror 11 of the scanning projection display optical system shown in FIG. 1 with a control system. FIG. 2 is a block diagram showing a control system of the scanning projection display apparatus according to Embodiment 1 of the present invention.

  The control system of the scanning projection display apparatus includes an image processing unit 21, a synchronization control unit 22, a modulation driving unit 23, and a scanning driving unit 24 as a projection control unit. The image processing unit 21 generates a modulation signal input to the spatial light modulator 5 and a drive signal input to the scanning mirror 11 based on image data of an image to be displayed. The modulation signal and the scanning signal are synchronized by the synchronization control unit 22 and output to the modulation driving unit 23 and the scanning driving unit 24 in synchronization. The input image data is an image acquired by a hyperspectral camera or an artificially created image. For example, the number of pixels is 120 × 96. The size of the projected image is 50 mm × 40 mm, 30 primary colors, 512 gradations, 60 FPS.

  The control system includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The microcomputer implements each processing unit by executing an image processing program and a control program by the CPU.

  As described above, according to the scanning projection display optical system and the scanning projection display apparatus according to Embodiment 1, a hyperspectral image can be projected with a simple configuration. In the scanning projection display optical system and the scanning projection display apparatus according to the embodiment, the spectroscopic optical system includes one diffraction grating, a slit is provided, and a one-dimensional image in each wavelength region is overlaid. Therefore, there is no image shift due to element displacement. Further, since the DMD is used as the spatial light modulation element 5, it can be configured as a coaxial optical system and has a structure that is easy to design, manufacture, and assemble. As a result, a high-resolution one-dimensional image can be created. Since the scanning projection display optical system and the scanning projection display apparatus according to the first embodiment use only one optical modulation element, the light use efficiency is high, and compared with the case where a plurality of optical modulation elements are used. Thus, it is not necessary to increase the synchronization accuracy and can be easily realized.

<Embodiment 2>
Next, a scanning projection display optical system and a scanning projection display apparatus according to Embodiment 2 of the present invention will be described. FIG. 3 is an optical path diagram showing a scanning projection display optical system according to Embodiment 2 of the present invention. The scanning projection display optical system according to the second embodiment includes a concave reflection type diffraction grating 7A in place of the spectroscopic optical system collimator lens 6, the plane reflection type diffraction grating 7, and the spectroscopic optical system imaging lens 8. Other configurations are the same as those of the scanning projection display optical system according to the first embodiment. The scanning projection display optical system according to the second embodiment has the same effects as the scanning projection display apparatus according to the first embodiment with a simpler configuration.

  In the first and second embodiments, as the white light source, a metal halide lamp can be used in addition to a xenon lamp as long as the light source has a high luminance and a flat spectral distribution. In addition, a white light emitting diode (LED), a halogen lamp, or an ultrahigh pressure mercury lamp can be used as long as the required wavelength range, luminance, and dynamic range are satisfied.

  Further, instead of the light pipe used to uniformly illuminate the spatial light modulation element 5, fly eye, Koehler illumination, or the like can be used. A diffuser plate may be used if there is a margin in the amount of light. Further, as the spatial light modulator, transmissive liquid crystal or reflective liquid crystal can be used instead of DMD. Further, as the spectroscopic element, a transmission type diffraction grating or prism, a grism combining a diffraction grating and a prism, or the like can be used. In the scanning projection display apparatus according to each embodiment, the optical system of a polychromator or a multichannel spectrometer can be used in reverse.

  Furthermore, by replacing the screen 13 with an eyepiece that focuses on the position of the screen 13, a hyperspectral image can be observed with the naked eye. In this case, observation is possible even when the luminance of the white light source is low.

1: White light source (light source)
2: Elliptical mirror 3: Light pipe 4: Illumination optical system 5: Spatial light modulation element 6: Spectral optical system collimator lens 7: Diffraction grating (spectral element)
7A: Concave reflection type diffraction grating 8: Spectroscopic optical system imaging lens 9: Slit member 10: Projection optical system collimator lens 11: Scanning mirror (scanning element)
12: Projection optical system imaging lens (projection optical element)
13: Screen (projection surface)
21: Image processing unit 22: Synchronization control unit 23: Modulation drive unit 24: Scanning drive unit

Claims (5)

A light source that emits white light;
A spatial light modulation element that outputs the modulated light obtained by spatially and temporally modulating the white light incident on the basis of an image signal based on an image signal based on the image to be displayed;
A spectroscopic element that emits the modulated light in different directions for each wavelength;
An illumination optical system for condensing light from the spectroscopic element;
A slit member that is arranged at a conjugate position with respect to the spectroscopic element of the illumination optical system, and emits a one-dimensional image of the image that is incident upon superimposing light of different wavelength regions that are spectrally separated at different positions of the spatial light modulator When,
A scanning element that operates in synchronization with the modulation of the spatial light modulator, scans the light emitted from the slit, and generates a scanned image forming a two-dimensional image;
A projection optical element that projects the scanned image from the scanning element onto a projection plane;
A scanning projection display optical system comprising:   The scanning projection display optical system according to claim 1, wherein the spatial light modulation element is a reflective element that includes a plurality of micromirrors and performs light modulation by changing the direction of the micromirrors.   The scanning projection display optical system according to claim 1, wherein the scanning element is a plane reflection type diffraction grating, and includes a condensing optical element in a lower stage.   The scanning projection display optical system according to claim 1, wherein the scanning element is a concave reflection type diffraction grating. A scanning projection display optical system according to any one of claims 1 to 4,
Based on the input image data, a modulation signal for driving the spatial light modulation element and a scanning signal for driving the scanning element are generated, and the modulation signal and the scanning signal are transmitted to the spatial light modulation element and the scanning element. A projection control unit that outputs a two-dimensional image synchronously based on the image data;
A scanning projection display apparatus comprising: