JP5401977B2 - Image display device and light source device - Google Patents

Description

  The present invention relates to an image display device and a light source device.

  In recent years, projectors using a laser light source have been developed with the increase in output of semiconductor lasers and the appearance of blue semiconductor lasers. Since this type of projector has a narrow wavelength range of the laser light source, the color reproduction range can be sufficiently widened, and the size and the number of components can be reduced. This has great potential as a next-generation projector. However, when displaying on a projector using a laser light source, light interference occurs in a scatterer such as a screen, so that bright and dark spots are distributed in a striped pattern or a spotted pattern, so-called “speckle noise”. The phenomenon may occur.

  Speckle noise causes an adverse effect such as giving an observer a glare and giving an uncomfortable feeling when viewing an image. In particular, since laser light is highly coherent, speckle noise is likely to occur. However, not only a laser light source but also a lamp light source, in recent years, the coherence of light has been increased by shortening the arc, and a technique for removing speckle noise has become important. Therefore, a technique for reducing speckle noise as described below has been proposed (see, for example, Patent Document 1).

Patent Document 1 discloses a laser beam condensing irradiation apparatus in which a random phase plate for controlling condensing characteristics is arranged between a laser oscillator and a condensing lens. In this apparatus, a condensing pattern, which is an aggregate of a large number of minute spots formed by the phase plate and the condensing lens, overlaps with a small positional deviation. Thereby, the speckle pattern is averaged, speckle noise is removed, and a smoothed light collection pattern is obtained.
JP 11-295649 A

  However, in the case of the apparatus described in Patent Document 1, speckle noise is reduced and a uniform light intensity distribution can be obtained. On the other hand, by using a random phase plate, the light from the laser oscillator can be transmitted only by a condenser lens. Compared with the case of condensing, the condensing spot becomes larger. If such a laser light source device is used for, for example, a scanning image display device, there is a problem that the resolution is remarkably lowered as the condensed spot is enlarged, and a high-quality image display device cannot be realized.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to provide an image display device capable of sufficiently suppressing speckle noise and ensuring high resolution, and a light source device used therefor. To do.

In order to achieve the above object, a first image display device of the present invention includes a light source that emits laser light, an optical scanning unit that scans the laser light on a projection surface and draws an image, and a predetermined A light transmissive member that transmits the laser light incident from the light source in the transmissive region and emits the laser light toward the light scanning unit, and a light transmissive member driving unit that causes movement of the light transmissive member, By causing the light transmissive member to move by driving the light transmissive member driving means, the phase of the laser light is not temporally changed at the center of the laser light transmissive region, and the peripheral portion of the transmissive region. Then, the phase of the laser beam is temporally changed.
The first image display device of the present invention includes a light source that emits laser light, a light scanning unit that draws an image by scanning the laser light on a projection surface, and the light source in a predetermined transmission region. A light transmissive member made of a disk-shaped member that transmits the incident laser light and emits the laser light toward the light scanning unit; and a light transmissive member driving unit that rotates the light transmissive member around a predetermined rotation center. The light transmissive member has a first refractive index region made of a material having a first refractive index at the center of the transmissive region, and the peripheral portion of the transmissive region has the first refractive index region. A first refractive index region made of a material having a refractive index, and a second refractive index region made of a material having a second refractive index different from the first refractive index, and a central portion of the transmission region Then, the optical path length of the laser beam is constant, The optical path length of the laser beam at a predetermined position is changed temporally by rotating the light transmitting member at the periphery of the transmitting region without changing the phase of the laser beam with time, and the laser beam It is characterized in that the phase of is changed with time.

The “peripheral part of the laser beam (transmission region)” here means that the intensity on the intensity distribution curve in the cross section passing through the maximum intensity is 1 / e, assuming that the intensity distribution of the laser light follows a Gaussian distribution. ^It is a point that becomes ² and an area in the vicinity thereof. The “center portion of the laser beam (transmission region)” is a region excluding the above “peripheral portion”, and is a region closer to the central axis than the point where the intensity on the intensity distribution curve is 1 / e ^2. That is.

  Although the inventor of the present application generates speckle noise in the central portion and the peripheral portion of the laser beam as defined above, the speckle noise generated in the central portion of the laser beam is high because the intensity of the original laser beam is high. Is difficult to see, and speckle noise generated at the periphery of the laser beam is relatively high due to the low intensity of the original laser beam, and is generated in a wide range, so it is easy for the observer to see I found that there is a tendency to become. Therefore, when thinking about measures to reduce speckle noise, I would like to make a configuration that only measures speckle noise that occurs at the edge of the laser beam, but does not take measures against speckle noise that occurs at the center of the laser beam. It came.

  According to the first image display device of the present invention, when the laser light emitted from the light source passes through the light transmitting member, the phase of the laser light is changed at the peripheral portion of the laser light transmitting region by the movement of the light transmitting member. Since it changes over time, different speckle patterns are averaged over time, and speckle noise can be reduced. On the other hand, since the phase of the laser beam does not change with time at the center of the transmission region, speckle noise is not reduced. However, since it is difficult for the observer to visually recognize the image, it does not particularly hinder the visual recognition of the image. Further, according to the configuration of the present invention, the phase is not changed with respect to the entire laser beam as in the configuration of the conventional patent document 1, but the phase is not changed at the center portion, so that the expansion of the beam diameter is suppressed. The image resolution can be sufficiently maintained.

In the first image display device of the present invention, the light transmission member has a constant optical path length of the laser light at a central portion of the transmission region, and the light transmission member driving means at a peripheral portion of the transmission region. The optical path length of the laser beam at a predetermined position can be changed with time by driving of.
According to this configuration, it is possible to relatively easily realize a configuration in which the phase of the laser beam is temporally changed only at the peripheral portion of the laser beam transmission region.

In the first image display device of the present invention, the light transmission member is rotatable around a predetermined rotation center, and a first refractive index region made of a material having a first refractive index and the first refraction. A disc-shaped member including a second refractive index region made of a material having a second refractive index different from the refractive index, and the disc-shaped member has a central portion of the transmission region corresponding to the first refractive index region. And it is good also as a structure where the said 1st refractive index area | region and the said 2nd refractive index area | region are mixed in the peripheral part of the said transmissive area | region.
There are two ways to change the optical path length: a method of changing the refractive index and a method of changing the physical distance of the portion through which light passes. According to this configuration, by rotating the disk-shaped member in which the first refractive index region and the second refractive index region are mixed at the peripheral portion of the laser light transmission region, there is a peripheral portion of the transmission region. When attention is paid to a point, the refractive index at that point changes with time. In this way, it is possible to realize a configuration in which the optical path length of the laser light is changed with time.

Alternatively, in the first image display device of the present invention, the light transmissive member is rotatable around a predetermined rotation center, and has a plurality of phase modulation regions having different plate thicknesses in the circumferential direction at the peripheral edge. It can be set as the structure which consists of a plate-shaped member.
According to this configuration, when a disk-shaped member having a plurality of phase modulation regions having different thicknesses in the circumferential direction is rotated, when attention is paid to one point at the peripheral edge of the transmission region, the laser beam is transmitted at that point. The physical distance of the part will change over time. In this way, it is possible to realize a configuration in which the optical path length of the laser light is changed with time.

The second image display device of the present invention includes a light source that emits laser light, a light scanning unit that draws an image by scanning the laser light on a projection surface, and an incident light from the light source in a predetermined transmission region. A light transmissive member that transmits the laser light and emits the light toward the light scanning unit, and a light transmissive member driving unit that causes the light transmissive member to move, and is driven by the light transmissive member driving unit. By causing the light transmitting member to move, the amplitude of the laser light is not temporally changed at the center of the transmission region of the laser light, and the amplitude of the laser light is temporally changed at the peripheral portion of the transmission region. It is characterized by changing to.
Further, the second image display device of the present invention includes a light source that emits laser light, a light scanning unit that draws an image by scanning the laser light on a projection surface, and the light source in a predetermined transmission region. A light transmissive member made of a disk-shaped member that transmits the incident laser light and emits the laser light toward the light scanning unit; and a light transmissive member driving unit that rotates the light transmissive member around a predetermined rotation center. The light transmission member has an opening in which a central portion of the transmission region and a part of the peripheral portion are opened, and the opening has a shape other than a circle centering on the rotation center. The laser beam is always transmitted through the central portion of the transmission region, and the amplitude of the laser beam is not changed with time, and the light transmission member is rotated at the peripheral portion of the transmission region. , Of the periphery of the transmission region By switching transmission and interruption of the laser light at a constant position in time, and wherein changing the amplitude of the laser light in time.

  According to the second image display device of the present invention, when the laser light emitted from the light source is transmitted through the light transmitting member, the amplitude of the laser light is increased at the peripheral portion of the laser light transmitting region by the movement of the light transmitting member. Since it changes over time, different speckle patterns are averaged over time, and speckle noise can be reduced. On the other hand, since the amplitude of the laser beam does not change in the central portion of the transmission region, speckle noise is not reduced, but it is difficult for the observer to visually recognize the image, so that the image is not particularly disturbed. Further, according to the configuration of the present invention, the entire laser beam is not modulated as in the configuration of the conventional patent document 1, but the amplitude is not modulated in the central portion, so that the expansion of the beam diameter can be suppressed. The image resolution can be maintained sufficiently.

In the second image display device of the present invention, the laser beam transmittance is changed temporally at a predetermined position in the peripheral portion of the transmission region by causing the light transmission member to move. Can do.
According to this configuration, the laser light transmittance at a predetermined position on the periphery of the transmission region changes with time, so that the amplitude of the laser light passing through that position changes with time, reducing speckle noise. can do. A configuration in which the transmittance of the laser light changes with time can be realized relatively easily.

In the second image display device of the present invention, the light transmissive member always transmits the laser light in the central portion of the transmissive region, and the light transmissive member driving means drives the peripheral portion of the transmissive region. It can be set as the structure which switches in time whether the said laser beam is permeate | transmitted or interrupted | blocked in a predetermined position.
According to this configuration, a configuration in which the amplitude of the laser beam is temporally changed at the peripheral portion of the laser beam transmission region can be realized relatively easily. In addition, since the laser light is transmitted or blocked at a predetermined position on the peripheral portion, in other words, the transmittance is changed over time between 100% and 0%, the amplitude is changed most greatly. The effect of reducing speckle noise can be maximized.

In the second image display device of the present invention, the light transmission member is rotatable about a predetermined center of rotation, and has an opening that opens the center of the transmission region and a part of the peripheral edge. The opening may be configured to have a shape other than a circle centered on the rotation center.
According to this configuration, the light transmitting member can be configured by a rotatable disk-shaped member having an opening, and a relatively simple configuration can be achieved. If the shape of the opening is a circle centered on the rotation center, the laser beam is always transmitted or blocked at a predetermined position on the peripheral edge even when the disk-like member is rotated. End up. If the opening has a shape other than a circle centered on the center of rotation, it is possible to realize a configuration that temporally switches whether laser light is transmitted or blocked at a predetermined position on the peripheral edge.

In the second image display device of the present invention, the shape of the edge of the opening may be irregular in the circumferential direction of the disk-shaped member.
According to this configuration, the time for transmitting the laser light, the length of time for which the laser light is blocked, the timing thereof, and the like are irregular, so that the effect of reducing speckle noise can be further increased.

In the first and second image display devices of the present invention, a condenser lens may be provided between the light source and the light transmission member.
According to this configuration, the laser beam can be appropriately condensed according to the size of the opening of the light transmitting member, and an efficient apparatus can be obtained.

A first light source device of the present invention includes a light source that emits laser light, a light transmissive member that transmits and emits the laser light incident from the light source in a predetermined transmission region, and moves the light transmissive member. A light transmitting member driving means for generating, and by causing the light transmitting member to move by driving the light transmitting member driving means, the phase of the laser light is set to a time at the center of the laser light transmitting region. The phase of the laser beam is temporally changed at the peripheral part of the transmission region without being changed.
The first light source device of the present invention includes a light source that emits laser light, and a light transmissive member that includes a disk-shaped member that transmits and emits the laser light incident from the light source in a predetermined transmission region. A light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center, and the light transmissive member is formed of a material having a first refractive index at the center of the transmissive region. A first refractive index region made of a material having the first refractive index and a second refractive index different from the first refractive index at a peripheral portion of the transmission region. A second refractive index region made of a material having a constant optical path length of the laser beam at the center of the transmission region, and without changing the phase of the laser beam with time, At the periphery of the region, the light transmitting member is Said optical path length of the laser beam at a predetermined position of the peripheral portion of the transmission region is changed temporally by rolling, characterized in that to change the phase of the laser light in time.

  According to the first light source device of the present invention, when the laser light incident from the light source is transmitted through the light transmitting member, the phase of the laser light is timed at the peripheral portion of the laser light transmitting region by the movement of the light transmitting member. Therefore, different speckle patterns are temporally averaged, and speckle noise can be reduced. On the other hand, since the phase of the laser beam does not change at the center of the transmission region, speckle noise is not reduced, but it is difficult for the observer to visually recognize it, so that no particular problem occurs.

The second light source device of the present invention includes a light source that emits laser light, a light transmissive member that transmits and emits the laser light incident from the light source in a predetermined transmissive region, and moves the light transmissive member. A light transmitting member driving means for generating the light transmitting member, and by causing the light transmitting member to move by driving the light transmitting member driving means, the amplitude of the laser light is set to a time at the center of the laser light transmitting region. The amplitude of the laser beam is temporally changed at the peripheral portion of the transmission region without being changed in a timely manner.
The second light source device of the present invention includes a light source that emits laser light, and a light transmissive member that includes a disk-like member that transmits and emits the laser light incident from the light source in a predetermined transmission region. And a light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center, and the light transmissive member has an opening in which a central portion of the transmissive region and a part of a peripheral edge are opened. The opening has a shape other than a circle centered on the rotation center, and the laser beam is always transmitted at the center of the transmission region, and the amplitude of the laser beam is temporally changed. Without changing, by rotating the light transmitting member at the peripheral portion of the transmissive region, the laser light is transmitted and blocked at a predetermined position on the peripheral portion of the transmissive region in time, and the laser light is switched. of And wherein varying the width temporally.

  According to the second light source device of the present invention, when the laser light incident from the light source is transmitted through the light transmitting member, the amplitude of the laser light is time-dependent at the peripheral portion of the laser light transmitting region due to the movement of the light transmitting member. Therefore, different speckle patterns are temporally averaged, and speckle noise can be reduced. On the other hand, since the amplitude of the laser beam does not change at the center of the transmission region, speckle noise is not reduced, but it is difficult for an observer to visually recognize, so no particular problem occurs.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
The image display device of the present embodiment is an image display device that draws an image on a screen using laser light sources that respectively emit red light, green light, and blue light, and is an example that uses a single-stage scanning unit. .
FIG. 1 is a perspective view showing a schematic configuration of the image display apparatus of the present embodiment. FIG. 2 is a front view showing a light transmission plate used in the image display apparatus. FIG. 3 is a diagram showing the intensity distribution of the laser light transmitted through the light transmission plate. In the following drawings, the dimensional ratio and scale may be changed for each component in order to make each component easy to see.

  As shown in FIG. 1, the image display device 1 according to the present embodiment includes a light source device 2 and a MEMS mirror 3 (light scanning unit). An image is displayed by two-dimensionally scanning the laser light emitted from the light source device 2 on the screen 4 (projected surface) by the MEMS mirror 3. The light source device 2 includes a red laser light source 5R that emits red laser light (center wavelength: 620 nm), a green laser light source 5G that emits green laser light (center wavelength: 530 nm), and blue laser light (center wavelength: 460 nm). A blue laser light source 5B, a cross dichroic prism 6, a condenser lens 7, and a light transmission plate 8 (light transmission member). Note that the wavelengths of the laser beams of the above colors are merely examples. The cross dichroic prism 6 combines the laser beams of the respective colors emitted from the laser light sources 5R, 5G, and 5B.

  The MEMS mirror 3 is a resonance-type mirror including a mirror part 11, a first frame part 12, a second frame part 13, a first beam part 14, and a second beam part 15. The mirror part 11 is supported on the first frame part 12 by a first beam part 14 extending in the horizontal direction, and the first frame part 12 including the mirror part 11 is secondly supported by a second beam part 15 extending in the vertical direction. It is supported by the frame part 13. With this configuration, the first frame part 12 including the mirror part 11 rotates and reciprocates around the second beam part 15 as a central axis (indicated by an arrow E), and scans the laser beam in the horizontal direction H on the screen 4 (low speed). scanning). Further, the mirror part 11 rotates and reciprocates with respect to the first frame part 12 with the first beam part 14 as the central axis (indicated by an arrow F), and scans the laser beam in the vertical direction V on the screen 4 (high-speed scanning). ). Thus, the MEMS mirror 3 scans the laser beam two-dimensionally in both the horizontal direction and the vertical direction of the screen 4 to draw an image.

  As shown in FIG. 2, the light transmission plate 8 includes a first refractive index region 17 made of a light transmissive material having a first refractive index, and a light transmission having a second refractive index different from the first refractive index. It is comprised with the disk-shaped member containing the 2nd refractive index area | region 18 which consists of a property material. As the light transmissive material, any material such as resin and glass can be used. The light transmission plate 8 has a constant plate thickness at all locations. As will be described later, the laser light passes through the entire region of the first refractive index region 17 and a part of the second refractive index region 18. In the present embodiment, the first refractive index region 17 is located inside the light transmission plate 8, and the second refractive index region 18 is located outside the light transmission plate 8, and the first refractive index region 17 and the second refractive index region are located. A boundary line K with respect to 18 has an irregularly curved shape along the circumferential direction of the light transmission plate 8.

  The light transmission plate 8 is configured to be rotatable about the center of the circle of the disk-shaped member. However, a physical rotation axis does not exist at the center of the light transmission plate 8, and light transmission is performed by an arbitrary rotation transmission mechanism 20 (light transmission member driving means) shown in FIG. 1 such as a rotation roller or a belt. The plate 8 is configured to rotate while being supported by the edge portion.

As shown in FIG. 3, the laser light has an intensity distribution curve G that follows a Gaussian distribution, and a position where the intensity is 1 / e ² is generally called a beam diameter D2 of the laser light. A position where an arbitrary strength higher than 1 / e ² is taken is defined as a diameter D1. Here, the boundary line K between the first refractive index region 17 and the second refractive index region 18 shown in FIG. 2 passes through the point P1 closest to the center of the disk-shaped member, and the outer diameter of the disk-shaped member. It is assumed that the radius of the circle indicated by the concentric two-dot chain line is the diameter D1. In FIG. 2, a circle indicated by a one-dot chain line having a beam diameter D <b> 2 as a radius intersects with a boundary line K between the first refractive index region 17 and the second refractive index region 18. In the following description, in the light transmitting plate 8 shown in FIG. 2, the inner side of the circle having the diameter D1 is referred to as “the central portion of the transmitting region” and the outer side of the circle having the diameter D1 is referred to as “the peripheral portion of the transmitting region”. That is, in the light transmission plate 8, all of the central portion of the transmission region corresponds to the first refractive index region 17, while the first refractive index region 17 and the second refractive index region 18 are mixed in the peripheral portion of the transmission region. ing.

  The condensing lens 7 in the subsequent stage of the cross dichroic prism 6 condenses the combined light emitted from the cross dichroic prism 6 to a beam diameter that satisfies the above-described condition in relation to the light transmission plate 8.

Here, the operation of the light transmission plate 8 will be described.
In the image forming apparatus 1 configured as described above, the light emitted from each of the laser light sources 5R, 5G, and 5B is combined by the cross dichroic prism 6, and the combined light is condensed by the condenser lens 7, and then rotated at high speed. Is incident on the light transmitting plate 8. At this time, of the laser light, the partial light flux that passes through the center of the transmission region corresponding to the inside of the circle having the diameter D <b> 1 shown in FIG. 2 is always transmitted through the first refractive index region 17. On the other hand, for the partial light flux that passes through the periphery of the transmission region corresponding to the outside of the circle of diameter D1 shown in FIG. 2, the boundary line K between the first refractive index region 17 and the second refractive index region 18 shown in FIG. Moves in the direction indicated by the arrow J, and the time for transmitting through the first refractive index region 17 and the time for transmitting through the second refractive index region 18 are irregularly switched.

  According to the image display device 1 of the present embodiment, when the laser light emitted from the light source device 2 passes through the light transmission plate 8, it is refracted at the peripheral portion of the laser light transmission region by the rotational movement of the light transmission plate 8. The rate varies irregularly. In this embodiment, since the plate thickness of the light transmission plate 8 is constant regardless of the location, the physical distance through which the laser light passes is constant, but the refractive index changes with time, so the optical path length is time. As a result, the phase of the laser beam changes with time. Then, since different speckle patterns are temporally averaged at the peripheral edge of the laser beam, speckle noise can be reduced. On the other hand, since the refractive index, that is, the optical path length is always constant at the center of the laser beam and the phase of the laser beam does not change, the speckle noise is not reduced. However, the speckle noise in this portion is not easily visually recognized by an observer from the beginning, so that even if the speckle noise is not reduced, it does not particularly hinder the visual recognition of the image. Further, since the phase is not changed with respect to the entire laser beam as in the configuration of the conventional patent document 1, the expansion of the beam diameter can be suppressed and the resolution of the image can be sufficiently maintained. Furthermore, in this embodiment, since the light is not shielded only by changing the phase of the peripheral portion of the laser light, the brightness of the image can be sufficiently ensured.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The overall configuration of the image display device of the following embodiment is the same as that of the first embodiment, and only the form of the light transmission plate is different. Therefore, in the following embodiment, description of the whole structure of an image display apparatus is abbreviate | omitted, and only a light transmissive board is demonstrated.
FIG. 4A is a front view of the light transmission plate of the present embodiment, and FIG. 4B is a cross-sectional view taken along the line BB ′ of FIG.

  The light transmissive plate of the first embodiment has two refractive index regions having different refractive indexes, whereas the light transmissive plate 22 of the present embodiment shown in FIGS. The whole is made of a light-transmitting material having a uniform refractive index. In the front view of the light transmission plate 22 shown in FIG. 4A, the inner side of the innermost circle (circle having a diameter D1) is an area corresponding to the center of the transmission area of the first embodiment, and the innermost circle. The outside is an area corresponding to the peripheral edge of the transmission area of the first embodiment. In the present embodiment, since the central portion of the transmission region of the light transmission plate 22 has a constant thickness and a constant refractive index, the optical path length is constant.

  On the other hand, the peripheral portion of the transmission region of the light transmission plate 22 has an annular portion 23, and the annular portion 23 has a plurality of phase modulation regions 23 divided in the circumferential direction. A sectional view of the annular portion 23 is as shown in FIG. 4B, and the plurality of phase modulation regions 24 have different plate thicknesses. The plate thickness may change in a constant pattern along the circumferential direction, but it is preferable that the plate thickness change irregularly as shown in FIG. With this configuration, the plurality of phase modulation regions 24 at the peripheral portion of the transmission region have different plate thicknesses, that is, physical distances through which laser light passes, even if the refractive index is constant along the circumferential direction. The lengths are different from each other.

The operation of the light transmission plate 22 of this embodiment will be described.
When the light emitted from each of the laser light sources 5R, 5G, and 5B enters the light transmitting plate 22 that rotates at high speed via the cross dichroic prism 6 and the condenser lens 7, the laser light is shown in FIG. The phase of the partial light flux that passes through the center of the transmission region corresponding to the inside of the circle having the diameter D1 does not change because the optical path length is always constant. On the other hand, for the partial light flux (see FIG. 4B) that passes through the periphery of the transmission region corresponding to the outside of the circle having the diameter D1, the optical path length changes irregularly in time, so that the phase of the laser light is It changes irregularly in time.

  According to the image display device of the present embodiment, the phase changes temporally at the peripheral portion of the laser beam, but the phase does not change at the central portion of the laser beam, so that the resolution of the image is sufficiently reduced while reducing speckle noise. The same effect as that of the first embodiment can be obtained. Further, since the light is not shielded at the peripheral edge of the laser beam, the point that the brightness of the image can be sufficiently secured is the same as in the first embodiment. In the case of this embodiment, the light transmissive plate 22 is relatively easy to manufacture because only one type of constituent material is required for the light transmissive plate 22.

[Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
The light transmission plates of the first and second embodiments are of the phase modulation type that modulates the phase of the laser light at the peripheral edge of the transmission region, whereas in the third and fourth embodiments, the light transmission plate of the transmission region An example of an amplitude modulation type light transmission plate that modulates the amplitude of laser light at the peripheral edge will be described.
FIG. 5 is a front view of the light transmission plate of the present embodiment.

  The light transmissive plate of the first and second embodiments is entirely made of a light transmissive material including the peripheral portion of the transmissive region, whereas the light transmissive plate 32 of the present embodiment is as shown in FIG. Furthermore, it is a disk-shaped member formed of a light-shielding material such as a metal having heat resistance, for example, and an opening 33 is formed. The edge of the opening 33 has an irregularly curved shape along the circumferential direction of the light transmission plate 32. As in the first and second embodiments, the light transmission plate 32 does not have a physical rotation axis, but rotates around the center of the light transmission plate 32 while being supported by an arbitrary rotation transmission mechanism. It has become.

  In the front view of the light transmission plate 32 shown in FIG. 5, a circle indicated by a two-dot chain line concentrically with the outer diameter of the light transmission plate 32 through the point P1 where the edge of the opening 33 is closest to the center of the light transmission plate 32. The inside of (circle of diameter D1) is a region corresponding to the center of the laser light transmission region, and the outside of the circle is a region corresponding to the peripheral portion of the transmission region. In the present embodiment, when the laser beam is incident while the light transmission plate 32 is rotating, the laser beam is always transmitted through the central portion of the transmission region corresponding to the inside of the circle having the diameter D1. On the other hand, at the peripheral portion of the transmission region corresponding to the outside of the circle having the diameter D1, whether the laser light is transmitted or blocked by the light transmission plate 32 is switched irregularly in time. In other words, the amplitude of the laser light changes irregularly in time at the periphery of the transmission region.

  According to the image display device of the present embodiment, the amplitude changes temporally at the peripheral portion of the laser beam, while the amplitude does not change at the central portion of the laser beam, so that the resolution of the image is sufficiently reduced while reducing speckle noise. The same effect as the first and second embodiments can be obtained. Further, the light transmission plate 32 can be easily manufactured only by forming the opening 33 in the disk-shaped member.

[Fourth Embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a plan view of the light transmission plate of the present embodiment.

  The light transmissive plate of the third embodiment has an opening having an irregularly curved shape. On the other hand, as shown in FIG. 6, the light transmissive plate 42 of the present embodiment has a circular (perfect circular) opening 43 concentric with the outer shape of the light transmissive plate 42. If the light transmission plate of this shape is rotated with its center as the center of rotation, it is impossible to realize the effect of changing the amplitude with time at the peripheral edge of the laser beam. However, in this embodiment, the light transmission plate 42 is not rotated about the center of the light transmission plate 42, but the light transmission plate 42 is rotated about the point P2 shifted from the center of the light transmission plate 42. Yes. In other words, the light transmission plate 42 is configured to rotate eccentrically. Thereby, the laser beam is always transmitted near the center of the opening 43. On the other hand, in the region close to the edge of the opening 43, whether the laser beam is transmitted or blocked by the light transmission plate is switched over time.

Also in the image display device of the present embodiment, the amplitude changes temporally at the peripheral portion of the laser beam, while the amplitude does not change at the central portion of the laser beam, so that the resolution of the image is sufficiently reduced while reducing speckle noise. The same effect as the first to third embodiments can be obtained.
In the third and fourth embodiments, whether the laser beam is transmitted or blocked at the peripheral portion of the transmission region of the light transmission plate, in other words, whether the transmittance is 100% or 0% is temporal. It was the composition which switches to. Instead of this configuration, for example, the peripheral portion of the light transmission plate may be formed by combining two kinds of materials having different transmittances, and may be switched temporally with an intermediate transmittance other than 100% and 0%.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, examples of the phase modulation type light transmission plate are shown in the first and second embodiments, and examples of the amplitude modulation type light transmission plate are shown in the third and fourth embodiments. An example in which feature points such as the refractive index region, the shape of the opening, and the position of the rotation center are combined is shown. However, the combination of these feature points can be changed as appropriate. For example, instead of the concentric opening as shown in FIG. 6, a phase modulation type light transmission plate having concentric first refractive index regions and second refractive index regions is prepared and rotated eccentrically. Similar effects can be obtained with the configuration.

  As shown in FIG. 2 of the first embodiment and FIG. 5 of the third embodiment, if the boundary line between the two refractive index regions and the edge of the opening have an irregular shape, the phase and amplitude of the laser light are Since it changes irregularly, speckle noise can be reduced more effectively. However, speckle noise can be reduced even if the boundary line between the two refractive index regions and the edge of the opening are not necessarily irregular shapes, and may be a regular shape such as a polygonal shape or an elliptical shape. In these cases, a configuration in which the center of the light transmission plate is rotated about the center of rotation may be employed, or a configuration in which the light transmission plate is rotated eccentrically may be employed. As described above, the boundary line between the two refractive index regions and the edge of the opening may be circular, but in that case, the light transmission plate needs to be eccentrically rotated.

  In all the embodiments described above, examples of the configuration in which the light transmission plate is rotated have been described. However, instead of the rotation, the light transmission plate may be translated in a plane perpendicular to the optical axis of the incident light. . In that case, the feature of the present invention is that the phase and amplitude are not changed at the center of the laser beam, so that the distance of translational movement of the light transmitting plate may be very small. The light transmission plate may be finely oscillated by a sufficiently small distance with respect to the beam diameter D2. In addition, as an example of the basic configuration of the image display device, an example in which one MEMS mirror that performs both horizontal scanning and vertical scanning is provided has been described. However, two optical scanning elements that perform horizontal scanning and vertical scanning are provided. The structure may be different. In addition, the specific configuration of each part of the image display device can be changed as appropriate.

1 is a schematic configuration diagram of an image display device according to a first embodiment of the present invention. It is a front view which shows the light transmissive board used for an image display apparatus. It is a figure which shows intensity distribution of the laser beam which permeate | transmits a light transmissive board. It is a front view of the light transmissive plate of 2nd Embodiment of this invention. It is a front view of the light transmissive plate of 3rd Embodiment of this invention. It is a front view of the light transmissive plate of 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 2 ... Light source apparatus, 3 ... MEMS mirror (light scanning part), 4 ... Screen (light transmissive member), 5R, 5G, 5B ... Laser light source (light source), 8, 22, 32, 42 ... Light transmitting plate (light transmitting member), 17 ... first refractive index region, 18 ... second refractive index region, 20 ... rotation transmission mechanism (light transmitting member driving means), 24 ... phase modulation region, 33, 43 ... opening .

Claims (6)

A light source that emits laser light;
An optical scanning unit that draws an image by scanning the laser beam on a projection surface;
A light transmissive member made of a disk-shaped member that transmits the laser light incident from the light source in a predetermined transmission region and emits the laser light toward the optical scanning unit;
A light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center ,
The light transmissive member has a first refractive index region made of a material having a first refractive index at a central portion of the transmissive region, and has a first refractive index at a peripheral portion of the transmissive region. The first refractive index region made of a material and the second refractive index region made of a material having a second refractive index different from the first refractive index;
In the central part of the transmission region, the optical path length of the laser light is constant, without changing the phase of the laser light in time,
In the peripheral portion of the transmission region, the optical path length of the laser light at a predetermined position is temporally changed by rotating the light transmission member, and the phase of the laser light is temporally changed. An image display device. A light source that emits laser light;
An optical scanning unit that draws an image by scanning the laser beam on a projection surface;
A light transmissive member made of a disk-shaped member that transmits the laser light incident from the light source in a predetermined transmission region and emits the laser light toward the optical scanning unit;
A light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center ,
The light transmissive member has an opening in which a central portion of the transmissive region and a part of a peripheral portion are opened.
The opening has a shape other than a circle centered on the rotation center,
In the central part of the transmission region, the laser beam is always transmitted, and the amplitude of the laser beam is not changed with time,
By rotating the light transmitting member at the peripheral portion of the transmission region, the transmission and blocking of the laser light at a predetermined position on the peripheral portion of the transmission region is switched over time, and the amplitude of the laser light is changed over time. Image display apparatus characterized by being changed in a moving manner. The image display device according to claim 2 , wherein a shape of an edge of the opening is irregular in a circumferential direction of the disk-shaped member. The image display apparatus according to any one of claims 1 to 3, characterized in that the converging lens is provided between the light transmitting member and the light source. A light source that emits laser light;
A light transmitting member made of a disk-shaped member that transmits and emits the laser light incident from the light source in a predetermined transmission region;
A light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center ,
The light transmissive member has a first refractive index region made of a material having a first refractive index at a central portion of the transmissive region, and has a first refractive index at a peripheral portion of the transmissive region. The first refractive index region made of a material and the second refractive index region made of a material having a second refractive index different from the first refractive index;
In the central part of the transmission region, the optical path length of the laser light is constant, without changing the phase of the laser light in time,
At the periphery of the transmission region, the optical path length of the laser light at a predetermined position on the periphery of the transmission region is changed temporally by rotating the light transmission member, and the phase of the laser light is temporally changed. A light source device characterized by being changed to A light source that emits laser light;
A light transmitting member made of a disk-shaped member that transmits and emits the laser light incident from the light source in a predetermined transmission region;
A light transmissive member driving means for rotating the light transmissive member around a predetermined rotation center ,
The light transmissive member has an opening in which a central portion of the transmissive region and a part of a peripheral portion are opened.
The opening has a shape other than a circle centered on the rotation center,
In the central part of the transmission region, the laser beam is always transmitted, and the amplitude of the laser beam is not changed with time,
By rotating the light transmitting member at the peripheral portion of the transmission region, the transmission and blocking of the laser light at a predetermined position on the peripheral portion of the transmission region is switched over time, and the amplitude of the laser light is changed over time. The light source device is characterized by being changed.

Images