JP2013101173A - Projection display device and image display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type display device able to efficiently reduce speckle noise.SOLUTION: The F value of a rear projection optical system 27 is made smaller than the F value of a front projection optical system 24. Angle transformation means 25 disposed in the position of an intermediate image formed by the front projection optical system 24 has a conjugation relation with a display screen 26. In addition, the means 25 is set so as to widen the angle of light emitted from the front projection optical system 24. The light transmittance distribution of space transmittance transformation means 28 installed in the pupil position of the rear projection optical system 27 or in a space before and behind the pupil position is set to be larger toward the outside form an optical axis center.

Description

  The present invention relates to a projection display apparatus that displays light from a light source as an image on a screen and an image display method thereof.

  The projection display device displays images on a screen using light from a light source as an image. Unlike a CRT (Cathode Ray Tube) or a PDP (Plasma Display Panel), the projection display device is a non-light emitting display device. Such a projection display generally has a light valve that adjusts the amount of light according to an image signal, an illumination optical system that illuminates the light valve with illumination light from a light source, and a small image created by the light valve. And a projection optical system for enlarging and projecting on the screen.

  Projection-type display devices magnify and project small images on a large screen, so even if the original spatial coherence of the light source (which indicates the ease of interference due to the nature of the light) is small, the image light is magnified by the optical system. As it does so, the spatial coherence increases and innumerable light and dark interference patterns are created by fine irregularities larger than the wavelength of light on the projected screen. This bright and dark pattern is called speckle and becomes noise in the image, giving the viewer an unpleasant feeling. In particular, speckle noise is a serious problem for light sources having a small light emitting point such as a laser and a high parallelism, that is, a light source having a large coherence.

  As a method for reducing this speckle noise, there has conventionally been a projection display device disclosed in Patent Document 1, for example. This projection display device is arranged in order from a laser light source, a collimating optical system, a scanning device, a first optical system, a light divergence angle conversion element, and a second optical system. In this configuration, the light from the light source made parallel by the collimating optical system is given an intensity distribution by the scanning device to form an image, and an intermediate image is created via the first optical system. The light diffusion angle conversion element arranged in the vicinity of the intermediate image is constituted by a microlens array, and discretely expands an incident light beam by a diffraction action. The enlarged image light is projected onto the screen by the second optical system. Speckle noise is generated by unevenness on the screen, but the speckle noise is reduced because multiple different speckle patterns formed by light of different diffraction angles are superimposed and observed by the observer. Can do.

JP 2006-53495 A

  However, in the above conventional projection display device, the spread angle of the laser beam is increased by the light diffusion angle conversion element, and a plurality of different diffraction angle lights are projected onto the screen via the second optical system. The intensity distribution with respect to the angle of light is relatively large for light with a small angle and relatively small for light with a large angle. For this reason, even if the speckle pattern is superimposed, the light and dark pattern 2 made with light having a large angle is relatively less than the light and dark pattern 1 made with light having a small angle. Although there is a difference, there is a problem that the effect of canceling each other's light and dark is not sufficient.

  The present invention has been made to solve the above problems, and an object of the present invention is to obtain a projection display device and an image display method capable of efficiently reducing speckle noise.

  A projection display device according to the present invention includes a plurality of modulated light sources that respectively emit at least red, green, and blue light, a combined optical system that combines light from the plurality of modulated light sources, and a plurality of combined combined optical systems. A light valve that modulates light from the modulated light source based on the video signal, a front projection optical system that projects an image formed by the light valve at a predetermined magnification to form an intermediate image, and an intermediate formed by the front projection optical system Angle conversion means arranged at the position of the image, a rear projection optical system that projects light from the intermediate image onto the display surface at a predetermined magnification, and a space installed at the pupil position of the rear projection optical system or in the space before and behind it A transmissivity conversion unit, and the F value of the rear projection optical system is smaller than the F value of the front projection optical system, and the angle conversion unit has a conjugate relationship with the display surface and is emitted from the front projection optical system. To spread the angle While being set obtaining as one in which the transmittance distribution of the light of the spatial transmittance converting means is set to be greater toward the outside from the center of the optical axis.

  In the projection display device of the present invention, the F value of the rear projection optical system is made smaller than the F value of the front projection optical system, and the angle conversion means has a conjugate relationship with the display surface and is emitted from the front projection optical system. Since the light is set to have an angular spread, and the light transmittance distribution of the spatial transmittance conversion means is set to increase from the center of the optical axis to the outside, it is relatively small for light with a small angle. The ratio of light having a large angle can be increased and speckle noise can be efficiently reduced.

It is a block diagram which shows the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the relative intensity | strength of red, green, and blue light with respect to time of the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement when there is no angle conversion means of the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement when there is no space transmittance conversion means of the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement at the time of providing the spatial transmittance | permeability conversion means of the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the relationship of the transmittance | permeability with respect to the angle in the spatial transmittance | permeability conversion means of the supervisory projection type display apparatus by Embodiment 1 of this invention. It is a block diagram at the time of providing three light valves of the projection type display apparatus by Embodiment 1 of this invention. It is explanatory drawing of the interference fringe in case there exists a slit of the space | interval d of the projection type display apparatus by Embodiment 1 of this invention, and an incoherent monochromatic light source of the finite magnitude | size D. FIG. It is a schematic diagram of an optical invariant. It is explanatory drawing of the projection type display apparatus by Embodiment 2 of this invention. It is explanatory drawing of the projection type display apparatus by Embodiment 3 of this invention. It is explanatory drawing of the projection type display apparatus by Embodiment 4 of this invention. It is explanatory drawing of the projection type display apparatus by Embodiment 5 of this invention.

Embodiment 1 FIG.
1 is a block diagram showing a projection display apparatus according to Embodiment 1 of the present invention.
The projection display apparatus (projector) 100 shown in FIG. 1 guides the light source module 112 that emits a plurality of visible light wavelengths (380 to 780 nm) and the illumination light from the light source module 112 to the light valve 22 that is an illuminated surface. An illumination optical system 111, a light valve 22 that adjusts the amount of illumination light guided by the illumination optical system 111 according to a video signal, spatially modulates, and a small image created by the light valve 22 on the display surface 26 A projection optical system 110 that performs enlarged projection is configured. More specifically, the light source module 112 forms a plurality of modulated light sources 20 (20a to 20i) and illumination light from the plurality of modulated light sources 20 into a beam shape, and mixes and combines the combined optical systems 21 ( 21a to 21c).

  Further, in the illumination optical system 111 that guides the illumination light from the light source module 112 to the light valve 22 that is an illuminated surface, for example, the light intensity of the illumination light while propagating in a space represented by a rod integrator or an optical fiber. A homogenizing element 10 is arranged that spatially averages the distribution. The projection optical system 110 includes a front projection optical system 24 and a rear projection optical system 27. An angle conversion represented by a diffusion plate, a microlens array, a diffraction grating, or the like is provided in the middle of the optical path at a position where an intermediate image is formed. A means 25 is arranged. Further, in the rear projection optical system 27, spatial transmittance conversion means 28 in which the transmittance of the image light is different in the space is disposed in the pupil position or in a free space without the front and rear lenses. Furthermore, it has a control device 29 for controlling the lighting of the light source module 112 in order to form an image in accordance with an external signal 31 typified by image input or the like and to create an image with a combination of light of three primary colors of red, green and blue. . The illumination optical system 111 may have a movable stop (not shown) that adjusts the amount of illumination light flux. The external power supply 30 is a power supply for supplying power to the light source module 112.

  Next, the operation of the projection display apparatus 100 shown in FIG. 1 will be described. The projection display device 100 of the present invention forms illumination light from a plurality of modulated light sources 20, guides it to a light valve 22 as an illuminated surface while uniforming the intensity distribution, and displays an image created by the light valve 22 on a display surface. The projection is enlarged to 26. The lights of the plurality of modulated light sources 20 are combined by the combining optical system 21 and combined into one. In the example shown in FIG. 1, an example in which light from the three combining optical systems 21 a to 21 c is guided to one uniformizing element 10 is shown. Specifically, as shown in FIG. The light from the modulated light sources 20a to 20i of the respective colors is guided to the combining optical systems 21a to 21c by optical fibers, but may be guided to the combining optical system by spatial propagation. Although FIG. 1 shows the light source module 112 including nine modulated light sources 20a to 20i, the number is not limited to a specific number.

  In general, CRTs, PDPs, and projection display devices produce colors by combining three or more types of light having different wavelengths. Therefore, three or more types of modulated light sources having different wavelengths are prepared, for example, modulated light sources 20a to 20c. May be configured such that red is used, the modulated light sources 20d to 20f are blue, and the modulated light sources 20g to 20i are green.

  The modulation light source 20 may be a laser light source, for example, a semiconductor laser, a laser light source made of a laser medium and a nonlinear material, or the like. As a laser medium, as a general solid laser material, for example, Nd: YAG, Nd: YLF, Nd: Glass, Nd: YVO4, Nd: GdVO4, Yb: YAG, Yb: YLF, Yb: KGW, Yb: KYW , Er: Glass, Er: YAG, Tm: YAG, Tm: YLF, Ho: YAG, Ho: YLF, Tm, Ho: YAG, Tm, Ho: YLF, Ti: Sapphire, Cr: LiSAF, etc. . As the nonlinear material, a general wavelength conversion material such as KTP, KN, BBO, LBO, CLBO, LiNbO3, LiTaO3, or the like can be used.

  The amount of light is adjusted (current control) by adjusting the peak current of the modulated light source 20, or by adjusting the duty ratio of PWM (Pulse Width Modulation) (PWM control), or the movable diaphragm (see FIG. The amount can be adjusted by opening and closing (not shown) or by deflecting light in the projection optical system direction (ON light) / non-projection optical system direction (OFF light) by the light valve 22. .

  The illumination light beams of the respective colors collected by the synthesis optical system 21 are guided to the uniformizing element 10. While propagating through the uniformizing element 10, the light beams mix in space and are uniformized in the plane. If the uniformizing element 10 has a rectangular shape as shown in FIG. 13, for example, it is formed into a uniform rectangular light on the light exit surface. In addition, although the equalization element 10 is comprised with a lot integrator, a light tunnel, an optical fiber, etc., it does not specify to these.

  The illumination light from the uniformizing element 10 uniformly illuminates the light valve 22 that is the illuminated surface. Since the light exit surface of the uniformizing element 10 is uniform rectangular light, the light valve 22 is also illuminated uniformly when the light exit surface side of the uniformizing element 10 and the light valve 22 are in an optically conjugate relationship. An optical system used to illuminate the light valve 22 from the combining optical system 21 that combines the light from the plurality of modulated light sources 20 is referred to as an illumination optical system 111.

  In the first embodiment, since there is only one light valve 22 that generates an image based on an external signal 31 typified by a video signal, the light source module 112 is generally about 30 Hz as shown in FIG. 2, for example. On the light valve 22 by controlling the lighting of the light source by the control device 29 so as to switch on / off the light of the three primary colors of red, green and blue, or more in time, at a speed higher than the response speed of the eyes. Thus, an image for each color can be generated in time series.

  Further, the image generated by the light valve 22 is enlarged and projected on the arbitrary display surface 26 as the image light 113 by the projection optical system 110. The display surface 26 is generally a white wall or screen. The display surface 26 and the light valve 22 are also optically conjugate to form a uniform and clear image on the display surface.

Next, two points in the present invention will be described with reference to FIGS.
The first point of the present invention is that when projecting the image light of the light valve 22 onto the display surface 26, the image light having a wide angle spread is guided to the rear projection optical system 27, and the spatial distribution on the pupil is made uniform. By doing so, the coherence of the image light that illuminates the unevenness of the surface of the screen arranged on the display surface 26 is reduced, and as a result, speckle noise that is bright and dark spots is reduced. Therefore, here, the operation after the light valve 22 which is a feature of the present invention will be described. The light valve 22 is a transmissive liquid crystal, a reflective liquid crystal, a digital micromirror device (DMD), or the like that forms an image by modulating the spatial distribution of illumination light according to an external input signal, mainly an image signal. However, this is not specific.

  When the image of the light valve 22 is projected by the projection optical system 110, there is an optical system that forms an image once in the middle. This is called intermediate imaging. At this time, the projection optical system 110 includes a front projection optical system 24 that projects the image light of the light valve 22 at a predetermined magnification to form an intermediate image 23, and the intermediate image 23 on the display surface 26 with a predetermined magnification (generally, the front projection optical system). It comprises a rear projection optical system 27 that projects at a magnification larger than that of the system 24. In order for the image of the light valve 22 that is the object plane to be formed on the display surface 26, the light valve 22 and the intermediate image 23, and the intermediate image 23 and the display surface 26 need to be in an optically conjugate relationship. . Although a lens system and a relay lens system for transferring an image from the front projection optical system 24 to the rear projection optical system 27 are required, the illustration thereof is omitted in FIGS. Moreover, in FIGS. 3-5, 200 has shown the observer.

  In the first embodiment, the angle conversion unit 25 is disposed at the position of the intermediate image 23, but FIG. 3 illustrates the case where the angle conversion unit 25 is not provided (the angle conversion unit 25 is indicated by a broken line). In this case, the spread of the image light from the front projection optical system 24 is incident on the rear projection optical system 27 without changing, and reaches the display surface 26, so that the unevenness of the surface of the screen arranged on the display surface 26 is illuminated. The spread of the light flux is determined by the front projection optical system 24.

Here, as shown in FIGS. 4 and 5, when the angle conversion unit 25 is disposed at the position of the intermediate image 23 formed by the front projection optical system 24, the image light from the front projection optical system 24 is converted into the angle conversion unit 25, For example, the emitted light is given a wide angle by a diffusing plate, a microlens array, a diffraction grating, or the like, and enters the rear projection optical system 27.
Furthermore, it is assumed that the F value of the rear projection optical system 27 is smaller than the F value of the front projection optical system 24, that is, the rear projection optical system 27 is a bright lens system that can transmit light at a wide angle. In this case, the light of the front projection optical system 24 is spread by the angle conversion means 25, and the spread light passes through the rear projection optical system 27, so that the image spread more than the spread of the light beam determined by the front projection optical system 24. Irregularities on the surface of the screen arranged on the display surface 26 can be illuminated with light. When the unevenness on the surface can be illuminated with light of different angles, the light and dark patterns formed by the unevenness differ in angle, so the sum of the lightness and darkness and light intensity is averaged, and the difference in lightness and darkness is reduced. This reduces glare, that is, speckle noise.

  However, when the angle conversion means 25 is used, the spread of the angle of the light beam that illuminates the screen is certainly widened. However, as shown in FIG. There are few light beams with a large spread compared with light beams. In other words, if the unevenness on the surface can be illuminated with light of different angles, the light and dark patterns formed by the unevenness will differ depending on the angle, so if the light intensity is summed, it will be averaged. When there are few large luminous fluxes, the patterns cancel each other out by averaging, but the efficiency is poor. For example, in FIG. 4, since the light beam having a small spread is 4 units and the light beam having a wide spread is 2 units, the pattern cancels out at an average of 4: 2, so the reduction effect is not sufficient.

  Therefore, the second point of the present invention is that, as shown in FIG. 5, the spatial transmittance conversion means 28, for example, in the radial direction from the center to the pupil position of the rear projection optical system 27 or the empty space before and after it. A translucent glass plate whose transmittance varies depending on the location is arranged. Note that, as shown in FIG. 6, for example, the spatial distribution of the transmittance is preferably increased from the center of the optical axis toward the outside, but is not limited to such a configuration. What is necessary is to reduce the light flux in the central portion relative to the light flux in the peripheral portion. Specifically, the absorption may be given in the central portion, concentric circle shape, or radial shape to the opening of the transparent glass plate. If the spatial transmittance conversion means 28 is thus arranged at the pupil position of the rear projection optical system 27 or at an empty space before and after the pupil position, the amount of the light beam passing therethrough is absorbed depending on the location, resulting in a phenomenon. . Thereby, a light beam having a relatively small spread compared with a light beam having a large spread is absorbed. For example, in FIG. 5, when passing through the spatial transmittance converting means 28, the light beam having a small spread is 2 units, and the light beam having a wide spread is 2 units. Thereby, speckle noise can be reduced efficiently.

  In the above example, only one light valve 22 is used. However, as shown in the projection display device 100a in FIG. 7, three light valves corresponding to the three primary colors of light, red, green, and blue (light valve) are used. 22a-22c) may be used. Note that there are three equalizing elements 10a to 10c corresponding to the three light valves 22a to 22c. In this case, it is not necessary to switch on / off the light of the three primary colors of red, green, and blue over time, but the brightness can be improved by controlling the lighting of the light source, such as simultaneously lighting the three primary colors to increase the brightness. There are benefits. In addition, since light of different wavelengths can be illuminated on the display surface 26 at the same time, the effect of reducing speckle noise can be further enhanced as compared with the case where one light valve 22 is provided.

Next, the relationship between the spread of the light beam, the coherence of the light wave, and the speckle noise will be described using mathematical expressions and numerical values.
The reason why a phenomenon generally called speckle or scintillation is seen on a transmission screen will be described. When the surface of an object has rough irregularities with respect to the scale of the wavelength of light, it appears in an image of coherent illumination light scattered, transmitted, and reflected by the surface. This is made by superimposing a large number of amplitude distributions (not intensity distributions) generated from different scattering points, and can be explained by interference due to coherence of the light source.

で表される。これは各々の強度の和に加えて干渉項

が付加されていることから、各々の偏光や位相差によって強度が変化することになる。 In order to simplify the explanation, the monochromatic wave E _j (r, t) = Re [E _jk expi (kr−ωt + δ _jk )] (1)
Consider the superposition of Two monochromatic waves overlap at some point, that is,
E = E ₁ + E ₂ (2)
Given the state of, the time average of the intensity is

It is represented by This is an interference term in addition to the sum of each intensity.

Therefore, the intensity changes depending on each polarization and phase difference.

  On the other hand, for example, speckle may be observed when observing light from a distant celestial body from the ground. The difference between the light from the celestial body and the laser light source will be described. The spectrum of the light from the celestial body is continuous and incoherent, and the spectrum of the laser light source is monochromatic and coherent.

This will be described with reference to FIG.
Consider a case where there are slits with a spacing d and an incoherent monochromatic light source having a finite size D, and light is emitted from both ends, the first light source and the second light source. Since the light from the first light source passes through different optical paths, a solid interference fringe is formed, and the light from the second light source also forms a broken interference fringe. If the difference D between the light source positions is small at the origin of each interference fringe, the deviation of the origin of the interference fringe is also small.

  Since the first light source and the second light source have no correlation with each other, the superposition of the solid line interference fringes and the broken line interference fringes is simply an intensity superposition (not amplitude). When the slit interval d considered here is small (the period of the interference fringes becomes conversely large), the deviation of the origin of the interference fringes is small compared to the period, and as a result of the addition of the intensity, Will strengthen each other. On the other hand, when the slit interval d is large (because the period of the interference fringe becomes smaller conversely), the deviation of the origin of the interference fringe is larger than the period, and as a result of the addition of the strength, the peaks and valleys cancel each other out and become uniform Will be.

と考えられる。この干渉性を保つ長さｄは、

となる。ＦはＦ値で光束の広がり（の逆数）Ｆ〜ｚ／Ｄを表す。従って光束の広がりが狭いほど（Ｆ値が大きいほど）干渉性を保つ長さｄが大きくなる。 A wavefront from a light source having a finite size D has an inclination of the expected size D / z. If the optical path length difference is equal to or less than 1λ at a position apart from the slit interval d, the coherence is maintained, that is,

it is conceivable that. The length d that maintains this coherence is:

It becomes. F is an F value, and represents the spread (reciprocal number) of F to z / D. Accordingly, the narrower the beam spread (the larger the F value), the longer the length d that maintains coherence.

Here, the optical invariant will be described. FIG. 9 shows a schematic diagram. It is assumed that an object having a size y _{1 of an} object and a size y ₂ is formed by a lens. At this time, proof of the relationship with the prospective angle θ is omitted,
y ₁ θ ₁ = y ₂ θ ₂ (7)
It becomes. This relational expression indicates that the product of the image size and the prospective angle θ is invariant in the optical system, and is called a Helmholz-Lagrange invariant, and is strictly based on paraxial theory.

For example, looking at Figure 9, the size of the image _<Increasing the y 3 _{<y 4,} yaw angle theta in turn _{θ 2> θ 3> y 2} θ 4 and it is learned. That is, the spread of the light beam (in this case, represented by the prospective angle θ) is the lateral magnification of the optical system β = y ₂ / y ₁ (8)
It turns out that it becomes small in inverse proportion to. Since the magnification of the projector optical system is generally high, such as 50 to 100 times, the spread of the light beam becomes smaller in inverse proportion.

となる。例えば、投写光学系の倍率β＝１００倍、照明光学系のＦ値、Ｆ＝３．５、波長λ＝５３０ｎｍとすると、ｄ＜１８６ミクロンとなる。距離ｄは倍率βやＦ値に比例するため、Ｆ値とβが大きいほど（光束の広がりが狭いほど）ｄも大きくなる。 Next, the relationship between the optical system of the projection display device and the display surface will be described.
Since the image is magnified at the lateral magnification β = y ₂ / y ₁ of the projection optical system 110, the light flux spread θ ₂ becomes 1 / β times, and the length d for maintaining coherence is

It becomes. For example, if the magnification β of the projection optical system is 100 times, the F value of the illumination optical system is F = 3.5, and the wavelength λ is 530 nm, d <186 microns. Since the distance d is proportional to the magnification β and the F value, the larger the F value and β (the narrower the light beam spread), the larger the d.

  The screen arranged on the display surface 26 is, for example, a screen that diffuses light by unevenness on the surface (surface diffusion), or a screen that diffuses light by mixing beads of various particle sizes with different refractive indexes from the medium (volume diffusion). ) Etc. The characteristic length of the irregularities and the beads is larger than the wavelength of visible light (approximately 380 to 780 nm), and the mainstream is 1 to 50 microns at most, in fact, about 5 to 20 microns.

  When the characteristic length of the fluctuation of the surface of the surface to be illuminated (illuminated surface) is sufficiently smaller than the length d that maintains coherence, this light flux is partially coherent due to spatial coherence. Since it becomes light, bright and dark spots, that is, speckle noise occurs.

  Although the proof is omitted, the above description of the monochromatic light is the superposition of the intensity (not the amplitude), so that it can be applied to a light source having a bandwidth such as quasi-monochromatic light. From the above, even for an incoherent light source, the spatial coherence of a light source having a finite size results in partially coherent illumination, and the speckle phenomenon is explained by superposition of intensity (not amplitude) be able to.

  Since the laser light source is a quasi-monochromatic light source having a narrow bandwidth, speckle is observed as described above even if the high coherence of the laser light source is reduced by some means.

  From the above, when the F value is reduced, the length d for maintaining coherence is also reduced. Therefore, the projection optical system 110 is divided into the front projection optical system 24 and the rear projection optical system 27 and the angle conversion means 25 is used. By extending the light flux to the rear projection optical system 27, the length d that maintains coherence can be reduced. Compared with the unevenness of the light diffusing element such as a screen disposed on the display surface 26 and the particle size of the fine particles, the length d that maintains coherence is reduced, thereby reducing speckle noise.

  As described above, according to the projection display apparatus of the first embodiment, the plurality of modulated light sources that respectively emit at least red, green, and blue light, and the combining optical system that combines the light from the plurality of modulated light sources, A light valve that modulates light from a plurality of modulation light sources synthesized by the synthesis optical system based on a video signal, a front projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image, Angle conversion means arranged at the position of the intermediate image formed by the front projection optical system, a rear projection optical system that projects light from the intermediate image to the display surface at a predetermined magnification, and a pupil position of the rear projection optical system or Spatial transmittance conversion means installed in the space before and after that, the F value of the rear projection optical system is smaller than the F value of the front projection optical system, the angle conversion means is in a conjugate relationship with the display surface, and From the front projection optical system Specular noise is efficiently reduced because the light transmission distribution of the spatial transmittance conversion means is set so as to increase from the center of the optical axis to the outside while being set to give an angular spread to the emitted light. be able to.

  Further, according to the image display method of the first embodiment, a plurality of modulated light sources that respectively emit at least red, green, and blue light, a combined optical system that combines light from the plurality of modulated light sources, and a combined optical system A light valve that modulates light from a plurality of modulated light sources based on a video signal, a front projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image, and a front projection optical system An angle conversion means arranged at the position of the intermediate image to be formed, a rear projection optical system that projects light from the intermediate image to the display surface at a predetermined magnification, and a pupil position of the rear projection optical system or a space before and behind it An image display method for a projection display device having a spatial transmittance conversion means installed, wherein the F value of the rear projection optical system is made smaller than the F value of the front projection optical system, and the angle conversion means is displayed. Conjugate relationship with surface At the same time, the angle conversion means gives the angle spread to the light emitted from the preceding projection optical system, and the spatial transmittance conversion means is set so that the light transmittance distribution increases from the center of the optical axis toward the outside. Therefore, speckle noise can be efficiently reduced in the projection display device.

Embodiment 2. FIG.
FIG. 10 is a configuration diagram illustrating the projection display apparatus according to the second embodiment. The projection display apparatus according to the second embodiment replaces the installation position of the spatial transmittance conversion means 28 with the pupil position of the rear projection optical system 27 of the first embodiment or the installation of the space before and after the first projection optical system. It is designed to be installed at or around 24 pupil positions. Since other configurations are the same as those of the first embodiment, the same reference numerals are given to corresponding portions, and descriptions thereof are omitted.

Next, the operation of the projection display apparatus according to the second embodiment will be described.
As described in the first embodiment, it is desirable to arrange the spatial transmittance conversion unit 28 in the rear projection optical system 27 having a large F value. However, it is difficult to arrange the spatial transmittance conversion unit 28 because of the gap between the lens system and other components. In some cases, it can be considered. In this case, as a suboptimal example, the spatial transmittance conversion means 28 is arranged at or near the pupil position of the front projection optical system 24 so that the spatial distribution on the pupil plane of the front projection optical system 24 is made uniform. Since they can be kept close to each other, if there is no angle conversion means 25, the pupil of the rear projection optical system 27 will approach uniformly. However, since it is necessary to spread the light beam incident on the rear projection optical system 27 by the angle conversion means 25, it is desirable to leave some distribution in the spatial distribution on the pupil plane in consideration of the effect.

  As described above, according to the projection display apparatus of the second embodiment, the spatial transmittance conversion means replaces the pupil position of the rear projection optical system or the space before and after it with the pupil of the front projection optical system. Since it is installed at or before and after the position, speckle noise can be efficiently reduced even when it is difficult to arrange in the rear projection optical system.

Embodiment 3 FIG.
In the third embodiment, the distribution of light incident on the light valve 22 is such that the central intensity is small and the peripheral intensity is large with respect to the angle. FIG. 11 shows the projection display of the third embodiment. The structure of an apparatus is shown.
As shown in FIG. 11, in the third embodiment, the light distribution of the light incident on the light valve 22 is set so that the central intensity is small and the peripheral intensity is large with respect to the angle. 2 is omitted. Note that the illumination optical system 111 is used to obtain the light distribution of the light source as shown in the figure. Since other configurations are the same as those of the first and second embodiments, the corresponding parts are denoted by the same reference numerals and description thereof is omitted.

Next, the operation of the projection display apparatus according to the third embodiment will be described.
In the first and second embodiments, the spatial distribution of the light flux on the pupil plane has been made uniform by the spatial transmittance conversion means 28. On the other hand, in the third embodiment, the light distribution of the illumination light from the light source module 112 that is the origin of the illumination light is adjusted in advance so that the center is small and the periphery is large. When adjusted in this way, the amount of peripheral light increases due to the light distribution of the light source of origin, so that the light amount distribution of the light beam that has propagated through the optical system to the pupil of the rear projection optical system 27 also approaches uniformly. Thereby, speckle noise can be reduced efficiently.

  As described above, according to the projection display apparatus of the third embodiment, a plurality of modulated light sources that respectively emit at least red, green, and blue light, and a combining optical system that combines light from the plurality of modulated light sources, A light valve that modulates light from a plurality of modulation light sources synthesized by the synthesis optical system based on a video signal, a front projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image, An angle conversion means disposed at the position of the intermediate image formed by the front projection optical system; and a rear projection optical system that projects light from the intermediate image onto the display surface at a predetermined magnification. The value is smaller than the F value of the front projection optical system, and the angle conversion means has a conjugate relationship with the display surface, and is set so as to give an angle spread to the light emitted from the front projection optical system. Incident on The light distribution, since the center intensity against angle was set to around strength increases small, it is possible to effectively reduce the speckle noise.

Embodiment 4 FIG.
FIG. 12 is a configuration diagram showing a projection display apparatus according to the fourth embodiment.
The projection display device shown in the figure is applied to the first embodiment in which the central intensity is small and the peripheral intensity is large with respect to the angle of the light distribution of light incident on the light valve 22 in the third embodiment. Is. That is, the configuration after the light valve 22 is the same as the configuration of the first embodiment shown in FIG.

  As described above, in the fourth embodiment, the light distribution of the light incident on the light valve 22 is designed such that the central intensity is small and the peripheral intensity is large with respect to the angle, and the spatial transmittance conversion means 28 is provided. Speckle noise can be reduced more efficiently.

  In the fourth embodiment, the case where the configuration of the third embodiment is applied to the first embodiment has been described. However, the configuration may be applied to the second embodiment.

  As described above, according to the projection display device of the fourth embodiment, in the projection display device of the first or second embodiment, the light distribution of the light incident on the light valve is represented by the center intensity with respect to the angle. Since the peripheral strength is small and speckle noise is increased, speckle noise can be further efficiently reduced.

Embodiment 5 FIG.
Embodiment 5 provides a birefringent layer that changes the polarization direction of light from a plurality of modulated light sources, and the combining optical system receives light from the plurality of modulated light sources via the birefringent layer. The light from the plurality of modulated light sources is synthesized with the phases shifted.

FIG. 13 is a configuration diagram showing the projection display apparatus of the fifth embodiment.
In the figure, birefringent layers 120a to 120c change the polarization direction of light from a plurality of modulated light sources 20a to 20i, and the respective outputs are input to the combining optical systems 21a to 21c. . Other configurations are the same as those of the projection display device described in any of Embodiments 1 to 4, and therefore, the same reference numerals are given to corresponding portions and the description thereof is omitted. The uniformizing element 10 is a rectangular uniformizing element 10 as shown in the enlarged portion of the broken-line circle in the figure.

Next, the operation of the projection display apparatus according to the fifth embodiment will be described.
First, light wave coherence will be briefly described. In general, coherence is considered to be a wave with a fixed relationship between phase and amplitude, but the initial phase, frequency (spectrum), and wave number (direction is indicated for vector quantity) are in a similar state. High coherence. Conversely, if these modes are in a disjoint state, the coherence is low. That is, the coherence is high when the light is in phase, the light has the same frequency, or the light is in the same direction. For example, since the laser light has the same initial phase, the frequency width is narrow (light having the same frequency), and the spread is small (the direction is uniform), the coherence is high. On the other hand, white light has a different initial phase, a wide frequency width (for example, a black body radiation spectrum), and a large spread, so that the white light becomes low coherence (incoherent) light.

  Here, light with a uniform direction and polarized light are considered. Light is an electromagnetic wave and is represented by two orthogonal components. In terms of quantum mechanics, light has two degrees of freedom of spin. Coherence is high when the states are the same, and low when they are in different states. Therefore, coherence is low when they have different polarization directions (different spin states), and when the polarization directions are aligned (spin states are aligned). The coherence increases. In terms of energy, the coherence is high when the state falls into the ground state and degenerates, and the coherence decreases when the degeneracy is solved. Therefore, in order to reduce the coherence, the polarization directions can be varied and mixed.

  Although the light source is preferably non-polarized light, it is difficult to do so, and in reality it is expected to have polarized light. Therefore, a case where polarization dependency remains in the modulated light source 20 is considered. When mixing the modulated light source 20 with the combining optical system 21, for example, if the polarization direction is rotated by, for example, 90 degrees by transmitting a half amount of light through the wave plate and then mixed with the remaining half amount of light, individual differences for each light source Since the polarization direction of half the amount of light is orthogonal, the polarization is mixed in various directions when averaged. That is, by mixing light in different states, the coherence of the combined illumination light beam can be reduced.

Here, the birefringent layers 120a to 120c may be wave plates in which the directions of the birefringent optical axes are aligned, for example, quarter wave plates, but are thin sheet-like resins made by simple extrusion. For example, PET (PolyEthylene Terephthalate) may be used. In extrusion molding, the resin is crushed by a roll and stretched thinly. At this time, if the molecular arrangement of the resin (polymer) is not spatially symmetric, the resin is easily arranged in a certain direction due to stress. This direction shifts the phase of light and changes the polarization direction.However, in the case of a thin sheet of resin made simply by extrusion, the direction of the optical axis varies in the plane according to the residual stress. It is suitable. That is, even if a wave plate designed to give a specific phase difference is not used, coherence can be reduced only by using a thin sheet-like resin (residual stress remaining by extrusion molding or the like).
In addition, since the TAC (TriAcetyl Cellulose) film is not made by extrusion molding even with the same sheet-like resin, the above effects are not obtained.

  When the coherence of the illumination light beam is reduced, the coherence of the light beam on the light valve 22 that is the illuminated surface is also reduced. Since the light beam finally propagates through the optical system to the display surface 26, strictly speaking, the coherence increases or decreases depending on the relationship between the optical system and the illumination light beam. However, if the original coherence is reduced, it is arranged on the display surface 26. Therefore, the coherence of the light beam that illuminates the screen is easily reduced. From the above, speckle noise generated on the screen is reduced. Since this method does not use a diffraction grating or a diffusion layer in the middle of the optical path, it is possible to display an image with low wavelength dependency due to diffusion (high color temperature) and high resolving power. Needless to say, the fifth embodiment may be combined with the first to fourth embodiments.

  As described above, according to the projection display apparatus of the fifth embodiment, a plurality of modulated light sources that respectively emit at least red, green, and blue light, and a compound that changes the polarization direction of light from the plurality of modulated light sources. Receiving light from a plurality of modulated light sources through the refraction layer and the birefringent layer, and combining a plurality of light synthesized from the plurality of modulated light sources by shifting the phases of the light from the plurality of modulated light sources Equipped with a light valve that modulates the light from the modulated light source based on the video signal and a projection optical system that projects the image created by the light valve at a predetermined magnification and projects it to the display surface, effectively reducing speckle noise can do.

  Further, according to the projection display device of the fifth embodiment, in the projection display devices of the first to fourth embodiments, the birefringent layer that changes the polarization direction of the light from the plurality of modulated light sources is provided, and the combined optical system Since the light from the plurality of modulated light sources is received through the birefringent layer and synthesized by shifting the phases of the light from the plurality of modulated light sources, speckle noise can be reduced more efficiently. it can.

In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  10, 10a to 10c Uniform element, 20, 20a to 20i Modulated light source, 21, 21a to 21c Composite optical system, 22, 22a to 22c Light valve, 23 Intermediate image, 24 Pre-stage projection optical system, 25 Angle conversion means, 26 Display surface, 27 Rear projection optical system, 28 Spatial transmittance conversion means, 29 Control device, 30 External power supply, 31 External signal, 100, 100a Projection display device, 110 Projection optical system, 111 Illumination optical system, 112 Light source module, 113 image light, 120a-120c birefringent layer, 200 observer,

Claims (7)

A plurality of modulated light sources emitting at least red, green and blue light, respectively;
A synthesis optical system for synthesizing light from the plurality of modulated light sources;
A light valve that modulates light from the plurality of modulation light sources synthesized by the synthesis optical system based on a video signal;
A pre-stage projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image;
Angle conversion means arranged at the position of the intermediate image formed by the preceding projection optical system;
A rear projection optical system that projects light from the intermediate image onto a display surface at a predetermined magnification;
Spatial transmittance conversion means installed in the pupil position of the rear projection optical system or the space before and after the pupil position,
The F value of the rear projection optical system is smaller than the F value of the front projection optical system,
The angle conversion means is in a conjugate relationship with the display surface, and is set to give an angle spread to the light emitted from the front projection optical system, and the light transmittance distribution of the spatial transmittance conversion means A projection type display device characterized in that is set to increase from the center of the optical axis toward the outside.   2. The spatial transmittance converting means is installed in a pupil position of the front projection optical system or a space before and after the pupil position of the rear projection optical system, instead of installing the pupil position of the rear projection optical system or a space before and behind the pupil position. Projection display device. A plurality of modulated light sources emitting at least red, green and blue light, respectively;
A synthesis optical system for synthesizing light from the plurality of modulated light sources;
A light valve that modulates light from the plurality of modulation light sources synthesized by the synthesis optical system based on a video signal;
A pre-stage projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image;
Angle conversion means arranged at the position of the intermediate image formed by the preceding projection optical system;
A rear projection optical system that projects light from the intermediate image onto a display surface at a predetermined magnification;
The F value of the rear projection optical system is smaller than the F value of the front projection optical system,
The angle conversion means is in a conjugate relationship with the display surface, and is set to give an angle spread to the light emitted from the preceding projection optical system, and the light distribution of the light incident on the light valve is changed. A projection display apparatus characterized in that the central intensity is small with respect to the angle and the peripheral intensity is large.   3. A projection display device according to claim 1, wherein the distribution of light incident on the light valve is such that the central intensity is small and the peripheral intensity is large with respect to the angle. A plurality of modulated light sources emitting at least red, green and blue light, respectively;
A birefringent layer that changes the polarization direction of light from a plurality of modulated light sources;
A combining optical system that receives the light from the plurality of modulated light sources via the birefringent layer and synthesizes the phases of the light from the plurality of modulated light sources, and
A light valve that modulates light from the plurality of modulation light sources synthesized by the synthesis optical system based on a video signal;
A projection display apparatus, comprising: a projection optical system that projects an image created by the light valve at a predetermined magnification and projects it to a display surface.   A birefringent layer that changes the polarization direction of light from the plurality of modulated light sources is provided, and the combining optical system receives light from the plurality of modulated light sources through the birefringent layer, thereby receiving the light from the plurality of modulated light sources. 5. The projection display device according to claim 1, wherein the light beams are combined while being shifted in phase. 6. A plurality of modulated light sources emitting at least red, green and blue light, respectively;
A synthesis optical system for synthesizing light from the plurality of modulated light sources;
A light valve that modulates light from the plurality of modulation light sources synthesized by the synthesis optical system based on a video signal;
A pre-stage projection optical system that projects an image created by the light valve at a predetermined magnification to form an intermediate image;
Angle conversion means arranged at the position of the intermediate image formed by the preceding projection optical system;
A rear projection optical system that projects light from the intermediate image onto a display surface at a predetermined magnification;
An image display method for a projection display device, comprising: a pupil position of the rear projection optical system or a spatial transmittance conversion unit installed in a space before and after the pupil position;
The F value of the rear stage projection optical system is made smaller than the F value of the front stage projection optical system, and the angle conversion means is in a conjugate relationship with the display surface. An image display method, wherein the emitted light is given an angular spread, and the spatial transmittance conversion means is set so that the light transmittance distribution increases from the center of the optical axis toward the outside.

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