JP5271463B1 - Polarization modulation element, optical member, and projector - Google Patents

Abstract

There is a problem that uneven color occurs.
The polarization modulation element is a polarization modulation element that receives a plurality of primary color images constituting a color, modulates and outputs a polarization state of the image, and has a wavelength width of at least one of the primary colors When one polarization state is input, the light is modulated and output in different polarization states for each wavelength.

Description

  The present invention relates to a polarization modulation element, an optical member, and a projector.

A display device that projects an image including polarized light on a screen and displays the image by reflected light from the screen is known (see, for example, Patent Document 1). There is also known a display device that projects an image from an inclined direction with respect to the normal line of the screen and enables projection onto the screen at a short distance.
[Patent Document 1] JP 2011-221303 A

  However, when an image is projected in an inclined direction, the incident angle of the image is different between one end and the other end of the screen, and each region of the screen is reached in a state of polarization, for example, an ellipticity of elliptically polarized light is different. As a result, there is a problem that the reflectance of the image is different in each area of the screen and color unevenness occurs.

  According to a first aspect of the present invention, there is provided a polarization modulation element that receives a plurality of primary color images constituting a color and modulates and outputs a polarization state of the image, and includes at least one of the plurality of primary colors Provided is a polarization modulation element that modulates and outputs different polarization states for each wavelength when one polarization state is input for the wavelength width of the primary color.

  In the second aspect of the present invention, the polarized light beam that is arranged on the input side of the polarization modulation element and that combines the images of the plurality of primary colors and outputs the combined image to the polarization modulation element. An optical member comprising a splitter is provided.

  In the third aspect of the present invention, the polarized light beam that is arranged on the input side of the polarization modulation element and that combines the images of the plurality of primary colors and outputs the combined image to the polarization modulation element. A projector is provided that includes a splitter, an image generation unit that generates the image with the plurality of primary color lights, and a light source that supplies the plurality of primary color lights to the image generation unit.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

1 is an overall configuration diagram of a projector 10. FIG. 4 is a graph showing the relationship between the wavelength and light intensity of a UHP lamp that is an example of the light source 20. 4 is a graph showing the relationship between the wavelength of an LED lamp, which is an example of the light source 20, and the light intensity. FIG. 6 is a diagram for explaining an example of the polarization direction modulation by the polarization modulation element. It is the schematic of the experimental apparatus used for the measuring method of a polarization direction. It is the graph which measured the intensity | strength of the light modulated by the polarization modulation element 42 which has the phase difference film 46 whose phase difference with respect to the light of a wavelength of 580 nm is 3100 nm. It is the graph which measured the intensity | strength of the light modulated by the polarization modulation element 42 which has the phase difference film 46 whose phase difference with respect to the light of a wavelength of 580 nm is 4100 nm. It is the graph which measured the intensity | strength of the light modulated by the polarization modulation element 42 which has the phase difference film 46 whose phase difference with respect to the light of a wavelength of 580 nm is 5100 nm. It is the graph which measured the intensity | strength of the light modulated by the polarization modulation element 42 which has the phase difference film 46 whose phase difference with respect to the light of a wavelength of 580 nm is 7200 nm. It is the graph which measured the intensity | strength of the light modulated by the polarization modulation element 42 which has the phase difference film 46 whose phase difference with respect to the light of a wavelength of 580 nm is 9300 nm. It is a front view explaining the point of the screen 12 which measured illuminance. It is a table | surface of the numerical value of the illumination intensity measured by experiment. It is the illuminance at points P1 to P3 at the top of the screen 12. Illuminance at points P4 to P6 in the middle of the screen 12. The illuminance at points P7 to P9 at the bottom of the screen 12. 2 is an overall configuration diagram of a projector 210 provided with different polarization modulation elements 242. FIG. 3 is an overall configuration diagram of a projector 310 including different polarization modulation elements 342. FIG. 3 is a schematic diagram of a polarization modulation element 342. FIG. It is a figure explaining the relationship between the 1st position of the pixel projected by the output control part 366, and a 2nd position. It is the graph which investigated the relationship between the wavelength and the intensity | strength of light when the retardation film of a polarization modulation element is comprised with the polycarbonate. It is the graph which investigated the relationship between the wavelength and the intensity | strength at the time of comprising the retardation film of a polarization modulation element with polyolefin resin.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is an overall configuration diagram of the projector 10. As shown in FIG. 1, the projector 10 projects an image on a screen 12 and displays the image by reflected light from the screen. An example of the projector 10 is a short focus type that projects from a position inclined upward or downward with respect to the screen 12. The projector 10 includes a light source 20, dichroic mirrors 22, 24, reflection mirrors 26, 28, 30, a condenser lens 32, a blue liquid crystal panel 34, a green liquid crystal panel 36, and a red liquid crystal panel 38. A polarization beam splitter 40, a polarization modulation element 42, and a projection lens 44. The blue liquid crystal panel 34, the green liquid crystal panel 36, and the red liquid crystal panel 38 are examples of an image generation unit.

  The light source 20 outputs light including three primary colors that are non-polarized light or polarized light, and provides light of the three primary colors to the blue liquid crystal panel 34, the green liquid crystal panel 36, and the red liquid crystal panel 38. An example of the light source 20 is an unpolarized UHP (Ultra High Power) lamp and LED lamp, a polarized laser, and the like.

  The dichroic mirror 22 is disposed on the downstream side in the light output direction of the light source 20. Of the three primary colors output from the light source 20, the dichroic mirror 22 transmits the blue light BL and reflects the green and red light RL toward the dichroic mirror 24.

  The dichroic mirror 24 is arranged in the light reflection direction of the dichroic mirror 22. The dichroic mirror 24 transmits the red light RL and reflects the green light GL to the green liquid crystal panel 36 and the polarization beam splitter 40.

  The reflection mirror 26 is arranged on the downstream side of the dichroic mirror 22 in the light output direction of the light source 20. The reflection mirror 26 reflects the blue light BL transmitted through the dichroic mirror 22 to the blue liquid crystal panel 34.

  The reflection mirror 28 is arranged in the light reflection direction of the dichroic mirror 22 and on the downstream side of the dichroic mirror 24. The reflection mirror 28 reflects the red light RL that has passed through the dichroic mirror 24 to the reflection mirror 30.

  The reflection mirror 30 is disposed in the light reflection direction of the reflection mirror 28. The reflection mirror 30 reflects the red light RL reflected by the reflection mirror 28 toward the red liquid crystal panel 38.

  The condenser lens 32 is disposed between the reflection mirror 28 and the reflection mirror 30. The condensing lens 32 condenses the red light RL reflected by the reflecting mirror 28 onto the reflecting mirror 30.

  The blue liquid crystal panel 34 has a plurality of pixels arranged in a two-dimensional matrix. Each pixel controls the polarization direction of light and transmits or blocks light having a specific polarization direction. As indicated by an arrow in the polarization beam splitter 40 of FIG. 1, the polarized light transmitted through each pixel of the blue liquid crystal panel 34 is an s wave. The blue liquid crystal panel 34 transmits a part of the light BL out of the blue light BL reflected by the reflection mirror 26 and proceeds to the polarization beam splitter 40 in a polarized state based on the image to be displayed. The remaining light BL is blocked.

  The green liquid crystal panel 36 has the same pixels as the blue liquid crystal panel 34. The green liquid crystal panel 36 transmits a part of the light GL out of the green light GL reflected by the dichroic mirror 24 and proceeds to the polarization beam splitter 40 in a polarized state based on the image to be displayed. The remaining light GL is blocked. The polarization direction of the light output from the green liquid crystal panel 36 is orthogonal to the polarization direction of the light output from the blue liquid crystal panel 34. As indicated by an arrow in the polarizing beam splitter 40 of FIG. 1, the polarized light transmitted through each pixel of the green liquid crystal panel 36 is p-wave.

  The red liquid crystal panel 38 has the same pixels as the blue liquid crystal panel 34. The red liquid crystal panel 38 transmits a part of the light RL out of the red light RL reflected by the reflection mirror 30 based on the image to be displayed and proceeds to the polarization beam splitter 40 in a polarized state. The remaining light RL is blocked. The polarization direction of the light output from the red liquid crystal panel 38 is parallel to the polarization direction of the light output from the blue liquid crystal panel 34.

  The polarization beam splitter 40 is an example of a beam splitter. The polarization beam splitter 40 is formed in a rectangular parallelepiped shape in which triangular prisms are combined. On one surface of the polarization beam splitter 40, a blue liquid crystal panel 34 is disposed so as to face. On the other surface of the polarizing beam splitter 40, a green liquid crystal panel 36 is disposed to face the surface. A red liquid crystal panel 38 is disposed opposite to one surface of the polarizing beam splitter 40 that is disposed opposite to the blue liquid crystal panel 34. The polarization beam splitter 40 is disposed on the input side of the polarization modulation element 42.

  The polarization beam splitter 40 reflects light in one polarization direction and transmits light in another polarization direction. Specifically, the polarization beam splitter 40 reflects the blue light BL and the red light RL, and transmits the green light GL whose polarization direction is orthogonal to these lights. As a result, the polarization beam splitter 40 reflects the image composed of the blue light BL transmitted through the blue liquid crystal panel 34 to the polarization modulation element 42. The polarization beam splitter 40 transmits an image composed of the green light GL that has passed through the green liquid crystal panel 36 and advances the image to the polarization modulation element 42. The polarization beam splitter 40 reflects an image composed of the red light RL transmitted through the red liquid crystal panel 38 to the polarization modulation element 42.

  That is, the polarization beam splitter 40 outputs the three primary color images input from the three directions in the direction of the polarization modulation element 42. Accordingly, the polarization beam splitter 40 outputs an image obtained by combining the three primary color images to the polarization modulation element 42. Instead of the polarizing beam splitter 40, a cross dichroic prism that reflects or transmits light for each wavelength may be applied as the beam splitter.

  The polarization modulation element 42 is disposed on the output side of the polarization beam splitter 40. The polarization modulator 42 receives images of the three primary colors blue, green and red from the polarization beam splitter 40, and modulates and outputs the polarization direction which is an example of the polarization state of the image. The polarization modulation element 42 includes a material having birefringence that causes a phase difference in polarized light having different polarization directions to change the polarization direction of the polarized light. As a result, the polarization modulation element 42 modulates and outputs light having different polarization directions for each wavelength when light having one polarization direction is input in the wavelength width of each primary color input in the polarization state. . The polarization modulation element 42 periodically modulates the polarization directions of the three primary colors with respect to the wavelength.

  An optical film such as a retardation film, artificial crystal, or optical crystal can be applied to the polarization modulation element 42. Examples of the optical film that can be applied to the polarization modulation element 42 include polyolefin resins and polycarbonate. In particular, when the polarization modulation element 42 is made of polyolefin resin, the wavelength dependency of modulation can be reduced. As an optical crystal applicable to the polarization modulator 42, silicon crystal, quartz crystal, KTP crystal, YAG crystal, sapphire crystal, calcite crystal, germanium crystal, YVO4 crystal, zinc selenium crystal, calcium fluoride, magnesium fluoride, lithium niobate ( For example, LiNbO3, lithium niobate, lithium niobium oxide) can be used.

  The projection lens 44 enlarges and projects an image of the light modulated by the polarization modulation element 42 onto the screen 12.

  Next, the operation of the projector 10 described above will be described. When the light source 20 outputs light including light of a plurality of primary colors, the light source 20 is divided into three primary colors by the dichroic mirrors 22 and 24. The divided blue light BL, green light GL, and red light RL are reflected by the reflection mirrors 26, 28, and 30, and the blue liquid crystal panel 34, the green liquid crystal panel 36, and the red liquid crystal panel 38 are reflected. Is input. The liquid crystal panel for blue 34, the liquid crystal panel for green 36, and the liquid crystal panel for red 38 transmit a part of the light of the three primary colors inputted to each polarized light based on the image to be displayed, and transmit the polarized beam splitter. Enter 40. The polarization beam splitter 40 combines the light images of the three primary colors input from the three directions and inputs them to the polarization modulation element 42. The polarization modulation element 42 is input to the projection lens 44 by changing the polarization direction of the light of each primary color of the combined image for each wavelength. The projection lens 44 projects the input image onto the screen 12. The light projected on the screen 12 is reflected by the screen 12 and provided to the observer as an image. Here, the light projected on the screen 12 has a different polarization direction for each wavelength. In other words, light having a plurality of polarization directions is projected on the screen 12. Thereby, the reflectance of light is made uniform irrespective of the projected area. As a result, the color unevenness of the image due to the different reflectance for each region can be reduced, so that the image quality can be improved.

  Next, a specific example of the light source 20 will be described. FIG. 2 is a graph showing the relationship between the wavelength and light intensity of a UHP lamp which is an example of the light source 20. FIG. 3 is a graph showing the relationship between the wavelength and light intensity of an LED lamp which is an example of the light source 20. 2 and 3, the vertical axis represents the light intensity, and the horizontal axis represents the light wavelength.

  As shown in FIG. 2, in the UHP lamp, the blue and green intensity peaks are 439 nm and 548 nm, respectively. In the UHP lamp, the blue wavelength range used for image generation is 430 nm to 480 nm. In the UHP lamp, the green wavelength range used for image generation is 520 nm to 580 nm. In the UHP lamp, the red wavelength width used for image generation is 620 nm to 680 nm. The wavelength width of each of these colors is an example of a wavelength width that the observer recognizes as one color.

  As shown in FIG. 3, in the LED lamp as an example of the LED light source, the intensity peaks of blue, green, and red are 450 nm, 520 nm, and 630 nm, respectively. In the LED lamp, the blue wavelength range used for image generation is 440 nm to 475 nm. In the LED lamp, the green wavelength width used for image generation is 500 nm to 540 nm. In the LED lamp, the red wavelength width used for image generation is 620 nm to 635 nm. The wavelength width of each of these colors is an example of a wavelength width that the observer recognizes as one color.

  When a laser is applied as the light source 20, the blue, green, and red intensity peaks are 440 nm, 532 nm, and 638 nm, respectively. In the laser, the blue wavelength range used for image generation is 420 nm to 460 nm. In the laser, the green wavelength range used for image generation is 525 nm to 537 nm. In the laser, the red wavelength range used for image generation is 618 nm to 680 nm. The wavelength width of each of these colors is an example of a wavelength width that the observer recognizes as one color.

  FIG. 4 is a diagram for explaining an example of the polarization direction modulation by the polarization modulation element 42. In FIG. 4, the horizontal axis illustrated on the lower side indicates the wavelength, and each arrow illustrated on the upper side indicates the polarization direction of the light transmitted through the polarization modulation element 42. As shown in FIG. 4, the polarized light whose polarization direction is transmitted through the polarization modulation element 42 is modulated by the polarization modulation element 42 into different polarization directions for each wavelength. For example, in the drawing, the light with the shortest wavelength is modulated into linearly polarized light that vibrates in the vertical direction, and the light with the next shortest wavelength is modulated into elliptical polarized light that is long in the vertical direction and is clockwise. In the figure, depending on the wavelength, the light is modulated by the polarization modulator 42 into clockwise and counterclockwise circularly polarized light, counterclockwise elliptically polarized light, horizontally elongated elliptically polarized light, and horizontally polarized linearly polarized light. Is done. Thereby, the light reaching the screen 12 via the polarization modulation element 42 includes a plurality of polarization directions for each primary color. Therefore, the polarization modulation element 42 of the projector 10 can reduce the variation in reflectance due to the screen 12 depending on the polarization direction. Thereby, the polarization modulation element 42 of the projector 10 is displayed on the screen 12 while bringing the x chromaticity coordinate and the y chromaticity coordinate of the xy chromaticity diagram determined by the CIE (= International Illumination Commission) close to 0.33. Color unevenness of the image can be reduced.

  Next, an experiment for examining the relationship between the retardation of the retardation film and the polarization direction will be described. First, a method for measuring the polarization direction modulated by the polarization modulation element will be described. FIG. 5 is a schematic view of an experimental apparatus used in the method for measuring the polarization direction.

  In this measurement method, the light source 120, the polarizing plate 152, the polarization modulation element 42, the polarizing plate 154, and the luminance meter 156 described above were used. The light source 120 is configured to sequentially output light of 400 nm to 700 nm. The polarizing plate 152 has a vertical transmission axis. Accordingly, the polarizing plate 152 transmits only the vibration component in the vertical direction and the vicinity thereof among the vibration components of the light output from the light source 120. The polarizing plate 152 has a horizontal transmission axis. That is, the polarizing plate 152 and the polarizing plate 154 have transmission axes in directions orthogonal to each other. The polarizing plate 154 transmits only the vibration component in the horizontal direction and the vicinity thereof among the vibration components of the light modulated by the polarization modulator 42. The luminance meter 156 measures the intensity of light transmitted through the polarizing plate 154 for each wavelength.

  In the measurement of the polarization direction, the light source 120 outputs light of 400 nm to 700 nm. The light is transmitted by the polarizing plate 152 as polarized light whose vertical direction is the polarization direction, and then the polarization direction is modulated by the polarization modulation element 42. Thereafter, of the modulated polarized light, polarized light oscillating in the horizontal direction is transmitted through the polarizing plate 154, and the intensity is measured by the luminance meter 156.

  Here, as described above, the polarization modulation element 42 modulates the input light into polarized light having a different polarization direction for each wavelength and outputs it. Therefore, even if the light output from the light source 120 is constant regardless of the wavelength, the intensity of the light transmitted through the polarizing plate 154 differs for each wavelength. Therefore, the light measured by the luminance meter 156 has a different intensity for each wavelength. Hereinafter, a specific description will be given with reference to experimental results.

  FIG. 6 is a graph obtained by measuring the intensity of light modulated by the polarization modulation element 42 having a phase difference film having a phase difference of 3100 nm with respect to light having a wavelength of 580 nm. The retardation film is made of polycarbonate. The widths B, G, and R shown in FIG. 6 indicate the wavelength widths of blue, green, and red in the UHP lamp described above, respectively. As shown in FIG. 6, in the measurement result, the intensity of light differs for each wavelength. This means that the polarization direction differs for each wavelength. That is, the linearly polarized light whose vertical polarization direction is changed by the polarizing plate 152 is modulated in a different polarization direction for each wavelength by the polarization modulation element 42, and the light transmission amount of the polarizing plate 152 is different for each wavelength. I understand. It can also be seen that the shorter the wavelength, the shorter the modulation period. This indicates that color unevenness due to a short wavelength color, that is, blue light can be further reduced.

  FIG. 7 is a graph obtained by measuring the intensity of light modulated by the polarization modulation element 42 having a phase difference film having a phase difference of 4100 nm with respect to light having a wavelength of 580 nm. FIG. 8 is a graph obtained by measuring the intensity of light modulated by the polarization modulation element 42 having a phase difference film having a phase difference of 5100 nm with respect to light having a wavelength of 580 nm. FIG. 9 is a graph obtained by measuring the intensity of light modulated by the polarization modulation element 42 having a retardation film having a retardation of 7200 nm with respect to light having a wavelength of 580 nm. FIG. 10 is a graph obtained by measuring the intensity of light modulated by the polarization modulator 42 having a retardation film having a retardation of 9300 nm with respect to light having a wavelength of 580 nm. 7 to 10, the retardation film is made of polycarbonate.

  The widths of B, G, and R shown in FIGS. 7 to 10 are the same as those in FIG. 7 to 10, it can be seen that the linearly polarized light whose vertical polarization direction is changed by the polarizing plate 152 is modulated by the polarization modulation element 42 in different polarization directions for each wavelength. Accordingly, it can be seen that at least the polarization modulation element 42 having a phase difference of 3100 nm or more with respect to light having a wavelength of 580 nm can be modulated and output in different polarization directions for each wavelength. Further, comparing FIG. 6 to FIG. 10, it can be seen that the period becomes shorter as the phase difference of the polarization modulation element 42 becomes larger. This indicates that the color unevenness can be reduced as the phase difference of the polarization modulation element 42 increases.

  More specifically, in FIG. 6, the modulation period is less than 1.5 periods in all the wavelength widths of the three primary colors. In FIG. 6, it can be seen that the difference in period is at most less than one period. Similarly in FIG. 7, it can be seen that the difference in period is at most less than one period. In FIG. 8, FIG. 9, and FIG. 10, the difference in period included in the wavelength width between blue and red is about 1.0 period, about 1.3 period, and about 2.0 period, respectively. Thereby, when the phase difference of a phase difference film is small, it turns out that the wavelength dependence of the polarization modulation element 42 can be reduced.

  Next, an experiment that proves that the projector 10 of the above-described embodiment can reduce color unevenness will be described. FIG. 11 is a front view for explaining points of the screen 12 on which the illuminance is measured. As shown in FIG. 11, in the color unevenness measurement experiment, the illuminance was measured at nine points P1 to P9 on the screen 12. Point P5 is the approximate center of screen 12. The other points P1 to P4 and points P6 to P9 are arranged at equal intervals in the vertical and horizontal directions around the point P5. The illuminance at each point on the screen 12 was measured with a color illuminometer manufactured by Konica Minolta. In the projector 10 of the experimental embodiment, a 5100 nm retardation film was applied as the polarization modulation element 42. In addition, as a projector to be compared with the projector 10 of the above-described embodiment, the illuminance was similarly measured for a comparative example without the polarization modulation element 42. The projector 10 and the comparative example of the embodiment are arranged below the screen 12. A straight line connecting the projector 10 and the comparative example and the upper end of the screen 12 is inclined downward by about 60 ° from the horizontal direction. In the horizontal direction, the distance between the projector 10 of the embodiment and the comparative example and the screen 12 is about 50 cm. In this state, the projector 10 and the comparative example of the embodiment irradiate the entire surface of the screen 12 with white light.

  FIG. 12 is a table of numerical values of illuminance measured by experiments. Moreover, the graph which plotted these experimental results is FIG. 13, FIG. 14, FIG. FIG. 13 shows the illuminance at points P1 to P3 at the top of the screen 12. FIG. FIG. 14 shows the illuminance at points P4 to P6 in the middle of the screen 12. FIG. 15 shows the illuminance at points P 7 to P 9 at the bottom of the screen 12. 13 to 15, the horizontal axis x and the vertical axis y correspond to the x chromaticity coordinates and the y chromaticity coordinates of the xy chromaticity diagram defined by the CIE. In the description of FIGS. 12 to 15, “horizontal” and “upper and lower” are horizontal and vertical directions or positions on the screen 12.

  As shown in FIGS. 12 to 15, in both the projector 10 of the embodiment and the comparative example, the difference between the maximum illuminance in the horizontal direction and the minimum illuminance at the same vertical position is the x chromaticity coordinate and the y chromaticity coordinate. Regardless, all are 0.01 or less. Thereby, it can be seen that in the horizontal direction, the difference in illuminance, that is, the color unevenness does not appear so much.

  As shown in FIGS. 12 to 15, in the comparative example, the maximum difference between the maximum illuminance in the vertical direction and the minimum illuminance of the y chromaticity coordinate at the same horizontal position is as large as 0.024. This is the difference between the point P1 and the point P7 at the left position in the y chromaticity coordinate of the comparative example.

  On the other hand, in the projector 10 according to the embodiment, the maximum difference between the maximum illuminance in the vertical direction and the minimum illuminance of the y chromaticity coordinate at the same horizontal position is 0.011. This is the difference between the point P2 and the point P5 in the y chromaticity coordinates of the projector 10 of the embodiment.

  In the comparative example, the minimum difference between the maximum illuminance and the minimum illuminance in the vertical direction of the y chromaticity coordinate at the same horizontal position is 0.014 at the right position. This is larger than the maximum difference 0.011 of the projector 10 of the above-described embodiment. Thereby, it can be seen that the projector 10 having the polarization modulation element 42 can extremely reduce color unevenness.

  Furthermore, as shown in FIGS. 12 to 15, in the projector 10 having the polarization modulation element 42, the x chromaticity coordinate is smaller than the comparative example, but the y chromaticity coordinate is closer to 0.33 than the comparative example. Thus, it can be seen that the chromaticity can be improved to white.

  FIG. 16 is an overall configuration diagram of a projector 210 that includes another polarization modulation element 242. The polarization modulation element 242 includes a retardation film 46, an input side glass plate 262, and an output side glass plate 264. The retardation film 46 has the same configuration as the retardation film of the polarization modulation element 42.

  The input side glass plate 262 is provided on one surface of the retardation film 46 on the image input side, that is, on the upstream side of the optical path. The input side surface of the input side glass plate 262 has higher flatness than the input side surface of the retardation film 46. The output side glass plate 264 is provided on the image output side of the retardation film 46, that is, on one surface on the downstream side of the optical path. The output side surface of the output side glass plate 264 has higher flatness than the output side surface of the retardation film 46. The input side glass plate 262 and the output side glass plate 264 are made of an isotropic material that does not have birefringence with respect to the three primary colors.

  Since the projector 210 is provided with the input side glass plate 262 and the output side glass plate 264 on the input side and the output side of the retardation film 46, it is possible to suppress variations in the wavefront of the light output from the polarization modulation element 242.

  In the projector 210, the example in which the glass plates are provided on both sides of the input / output surface of the retardation film 46 has been described, but the glass plate may be provided only on one surface. In this case, it is preferable to provide the output side glass plate 264 on the output side of the retardation film 46.

  In the projector 210, the example in which the glass plate is provided on the surface of the retardation film 46 has been described. However, at least one of the input / output surfaces of the retardation film 46, preferably the surface on the output side, is more surface than the retardation film 46. A resin film with high flatness may be provided. Furthermore, at least one of the input / output surfaces of the retardation film 46, preferably the output side surface, may be polished to improve flatness. These also suppress variations in the wavefront of the light output from the polarization modulator 242.

  FIG. 17 is an overall configuration diagram of a projector 310 provided with still another polarization modulation element 342. The polarization modulation element 342 includes a retardation film 46 and an output control unit 366. The output control unit 366 is disposed on the output side of the polarization beam splitter 40 and on the input side of the retardation film 46. The output control unit 366 outputs an image to a plurality of different positions by changing the polarization direction of the light output from the polarization beam splitter 40.

  FIG. 18 is a schematic diagram of the polarization modulation element 342. The output control unit 366 of the polarization modulation element 342 includes a polarization control unit 370 and a position changing unit 372. As the polarization controller 370, a liquid crystal panel or the like can be applied. The polarization controller 370 controls the polarization direction of the light output from the polarization beam splitter 40. Specifically, the polarization controller 370 outputs the input light while maintaining the polarization direction of the input light, and outputs the input light after rotating the polarization direction of the light by 90 °. The position changing unit 372 includes a material having birefringence. Thereby, the position change part 372 outputs the light of a different polarization direction to a different position.

  As shown in FIG. 18, it is assumed that light having a polarization direction in the vertical direction of the paper is output from the polarization beam splitter 40. In this case, when the polarization control unit 370 outputs light while maintaining the vertical polarization direction, the position changing unit 372 causes the light to travel straight. The position of the image output in this state is set as the first position.

  On the other hand, when the polarization control unit 370 rotates the polarization direction in the vertical direction and outputs light as the paper front and back direction, the position changing unit 372 refracts the light on both sides and changes the position while changing the position. Light is output in a substantially parallel state. Thereby, light is output in a state where the position is changed from the first position. The position of the image output in this state is set as the second position.

  FIG. 19 is a diagram for explaining the relationship between the first position and the second position of the pixels projected by the output control unit 366. In FIG. 19, each circle represents one pixel included in the image projected on the screen 12. A circle with dot hatching is designated as a pixel PX1 at the first position, and a circle without dot hatching is designated as a pixel PX2 at a second position.

  As shown in FIG. 19, the pitch of the pixels PX1 at the first position is “Pt”. The pitch of the pixels at the first position is the same as the pitch of the pixels at the second position. The pixel PX2 at the second position whose position has been changed by the output control unit 366 is projected at a position shifted by 1/2 pitch Pt in the horizontal direction with respect to the pixel PX1 at the first position. Accordingly, each pixel PX2 at the second position is projected between the pixel PX1 and the pixel PX1 at the first position. In other words, the pixel at the second position complements the pixel at the first position. Here, when the output control unit 366 changes the polarization direction every 1/30 seconds, the pixels are alternately projected onto the first position and the second position every 1/30 seconds. Thereby, the projector 10 can provide an observer with a high-quality image having twice the number of pixels.

  Next, wavelength dependency will be described. FIG. 20 is a graph showing the relationship between the wavelength and the light intensity when a retardation film of a polarization modulation element is formed of polycarbonate. FIG. 21 is a graph showing the relationship between the wavelength and the light intensity when a retardation film of a polarization modulation element is formed of a polyolefin-based resin. 20 and 21 show the results of simulations under the same conditions except for the material of the retardation film. In the simulations of FIGS. 20 and 21, a retardation film having a retardation of 5100 nm is applied.

  As shown in FIG. 20, in the polarization modulation element using polycarbonate, the modulation periods included in the blue, green, and red wavelength widths are about 1.9 periods, about 1.2 periods, and about 0.8 periods, respectively. is there. On the other hand, as shown in FIG. 21, in the polarization modulation element made of polyolefin resin, the modulation periods included in the wavelength widths of blue, green, and red are about 1.2 periods, about 1 period, and about 0.2 mm, respectively. 8 periods. Thus, it is understood that the difference in the modulation period within the wavelength widths of the three primary colors is within one period in both the polycarbonate and polyolefin resins.

  Further, the rate of change of the period of the blue wavelength width with respect to the period of the red wavelength width is about 2.375 (= 1.9 / 0.8) in the polycarbonate, but about 1 in the polyolefin resin. 0.5 (1.2 / 0.8). Thereby, it turns out that wavelength dependency can be reduced in polyolefin resin. As a result, it can be seen that the polyolefin resin can reduce the color unevenness more uniformly for all colors.

  In the embodiment described above, an example in which the polarization modulation element has only one retardation film has been described. However, a plurality of retardation films having different characteristics may be provided in the polarization modulation element. As an example having different characteristics, a polarizing film is provided with a retardation film in which the modulation period in the polarization direction becomes longer as the wavelength becomes longer, and a retardation film in which the modulation period in the polarization direction becomes shorter as the wavelength becomes longer. Can be proposed. Thereby, the wavelength dependency of the polarization modulation element can be reduced.

  In addition to the embodiments described above, other optical components may be arranged on the optical path. For example, a λ / 4 wavelength plate may be provided between the polarization modulation element 42 and the polarization beam splitter 40. In this case, the light input to the polarization modulation element 42 is circularly polarized light, and the polarization modulation element 42 modulates this circularly polarized light into polarized light having a different polarization direction.

  In the above-described embodiment, a projector that forms a color image with three primary colors has been described. However, the polarization modulation element described above may be applied to a projector that forms a color image with two primary colors or four or more primary colors.

  In the above-described embodiment, an example in which the wavelength width of one primary color or two primary colors includes one or more modulation periods of each primary color has been shown. However, for all wavelength widths of a plurality of primary colors, for example, three primary colors, Each of the three primary color modulation periods may include one or more periods.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  The execution order of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior”. It should be noted that they can be implemented in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for the sake of convenience, it means that it is essential to carry out in this order. is not.

DESCRIPTION OF SYMBOLS 10 Projector 12 Screen 20 Light source 22 Dichroic mirror 24 Dichroic mirror 26 Reflecting mirror 28 Reflecting mirror 30 Reflecting mirror 32 Condensing lens 34 Blue liquid crystal panel 36 Green liquid crystal panel 38 Red liquid crystal panel 40 Polarizing beam splitter 42 Polarization modulation element 44 Projection Lens 46 Retardation film 120 Light source 152 Polarizing plate 154 Polarizing plate 156 Luminance meter 210 Projector 242 Polarization modulation element 262 Input side glass plate 264 Output side glass plate 310 Projector 342 Polarization modulation element 366 Output control unit 370 Polarization control unit 372 Position change unit

Claims (13)

A polarization modulation element that receives a plurality of primary color images constituting a color and modulates and outputs the polarization state of the image,
A polarization modulation element that modulates and outputs a different polarization state for each wavelength when one polarization state is input for a wavelength width of at least one of the plurality of primary colors. The polarization modulation element according to claim 1, wherein the polarization state is periodically modulated with respect to the wavelength, and one or more modulation periods are included in a wavelength width of at least one of the plurality of primary colors. The polarization modulation element according to claim 1, wherein one or more modulation periods are included in a green wavelength width of the primary colors. 4. The polarization modulation element according to claim 1, wherein in all of the plurality of primary colors, one or more modulation periods are included in each wavelength width. 5. 4. The polarization modulation element according to claim 1, wherein a difference in period within each wavelength width is within one period between the plurality of primary colors. 5. The polarization modulation element according to any one of claims 1 to 5, wherein the polarization modulation element has a phase difference of 3100 nm or more with respect to light having a wavelength of 580 nm. 7. The polarization modulation element according to claim 1, wherein the polarization modulation element includes a polyolefin resin retardation film that changes a polarization state of polarized light. The polarization modulator is
A retardation film that changes the polarization state of polarized light;
2. An isotropic glass plate provided on at least one of the input side and output side surfaces of the image of the retardation film and having a surface flatness higher than that of the retardation film. The polarization modulation element according to claim 7. The polarization modulation element includes a retardation film that changes the polarization state of polarized light,
The polarization modulation element according to claim 1, wherein a surface of the retardation film is polished. The polarization modulator is a retardation film that changes the polarization state of polarized light, and
The polarization modulation element according to claim 1, further comprising: an output control unit that is disposed on an input side of the retardation film and outputs the image to a plurality of different positions. 11. The polarization modulation element according to claim 1, wherein the period of polarization modulation based on the wavelength is included in one or more periods within a wavelength width that the observer recognizes as one color. The polarization modulator according to any one of claims 1 to 11,
An optical member comprising: a beam splitter disposed on the input side of the polarization modulation element and combining the images of the plurality of primary colors and outputting the combined image to the polarization modulation element. The polarization modulator according to any one of claims 1 to 11,
A polarization beam splitter disposed on the input side of the polarization modulation element, combining the images of the plurality of primary colors and outputting the combined image to the polarization modulation element;
An image generation unit that generates the image with the light of the plurality of primary colors;
A projector comprising: a light source that supplies light of a plurality of primary colors to the image generation unit.

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