WO2011037039A1 - レーザー投射装置 - Google Patents
レーザー投射装置 Download PDFInfo
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- WO2011037039A1 WO2011037039A1 PCT/JP2010/065801 JP2010065801W WO2011037039A1 WO 2011037039 A1 WO2011037039 A1 WO 2011037039A1 JP 2010065801 W JP2010065801 W JP 2010065801W WO 2011037039 A1 WO2011037039 A1 WO 2011037039A1
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- laser
- liquid crystal
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/48—Laser speckle optics
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0136—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
- G02F1/13362—Illuminating devices providing polarized light, e.g. by converting a polarisation component into another one
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/14—Details
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/14—Details
- G03B21/20—Lamp housings
- G03B21/2006—Lamp housings characterised by the light source
- G03B21/2033—LED or laser light sources
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/14—Details
- G03B21/20—Lamp housings
- G03B21/2073—Polarisers in the lamp house
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N9/00—Details of colour television systems
- H04N9/12—Picture reproducers
- H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
- H04N9/3129—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM] scanning a light beam on the display screen
Definitions
- the present invention relates to a laser projection apparatus for projecting an image by deflecting and scanning laser light in two dimensions.
- Speckle is caused by the coherence of the laser as described above.
- the speckle can be reduced by reducing the coherence of the laser beam or by projecting speckle states that are temporally different. There is a way to average.
- Patent Document 1 As a method for changing the polarization state of laser light as described above, for example, in Patent Document 1, a polarization control unit is arranged in an optical path between a laser light source and a scanning mirror, and a wave plate provided in the polarization control unit is rotated. Thus, the polarization state of the projected image is changed over time. And the technique of aiming at the reduction of a speckle by multiplexing the changed polarization state is disclosed.
- Patent Document 2 a region through which a laser beam is transmitted is partitioned in a matrix, and in each partition, different polarization states of the laser beam are generated, and speckles are generated by changing the polarization state over time. We are trying to reduce it.
- Patent Documents 1 and 2 when reducing speckles by changing the polarization state of laser light for image projection, it is very important that the entire image projection surface is projected in a uniform polarization state. . That is, as shown in FIG. 5 of Patent Document 1, when the polarization state is changed while projecting an image on the projection surface, that is, while forming a frame, as in Patent Document 1 above, The polarization state varies depending on the location. Therefore, when an image is projected on a projection surface having a polarization dependency such as a metal or a polarization maintaining screen in the image projection apparatus of Patent Document 1, a luminance distribution is generated in the projection surface, and an image is displayed. The problem that quality deteriorates occurs. Furthermore, since a mechanism for rotating the wave plate is required, there are problems of vibration, impact, noise, and durability.
- a plurality of polarization states are generated from a plurality of sections formed in one region through which the laser beam is transmitted, so that beam diffusibility occurs. That is, since the straightness of the beam is lost, the spot diameter of the beam becomes large, resulting in a problem that the resolution is deteriorated and the focus-free characteristic is lost.
- the present invention has been made to solve the above-described problems, and in a configuration for reducing speckles by changing the polarization state of light, it is possible to obtain better image quality compared to the conventional art.
- An object is to provide a laser projection device.
- the present invention is configured as follows.
- the laser projection apparatus includes a laser light source that generates and modulates laser light, and two-dimensionally scans the laser light emitted from the laser light source to form one frame.
- a laser projection device having a scanning mechanism for projecting an image on a screen with a blanking period, and a polarization conversion unit that emits light to the screen while changing the polarization state of light emitted from the laser light source,
- a drive control device is further provided that changes the polarization state by operating the polarization converter during the blanking period without changing the polarization state during the formation of one frame.
- the polarization converter can be configured to have a liquid crystal element that forms a single polarization state in the transmission region of the laser light.
- the liquid crystal in the liquid crystal element may be a smectic liquid crystal or a ferroelectric liquid crystal.
- a laser projection apparatus that satisfies the following conditional expression may be used.
- the polarization conversion unit may be disposed between the laser light source and the scanning mechanism.
- the polarization conversion unit may be configured to be provided in a light exit window disposed between the scanning mechanism and the screen.
- the polarization states that are different in the polarization conversion unit may be orthogonal to each other.
- the laser projection apparatus may further include a plurality of laser light sources that emit laser beams having different wavelengths as the laser light source, and an optical system that combines the laser beams from the plurality of laser light sources.
- each of the plurality of laser light sources generates three laser lights of blue light, green light, and red light
- the polarization conversion unit has polarization states orthogonal to each other with respect to the green light or red light laser light.
- the polarization may be converted so that
- the polarization conversion unit may be disposed between the optical system and the scanning mechanism.
- the laser projection device includes a polarization conversion unit that changes a polarization state of light, a laser projection device that projects an image with a blanking period between frames, a drive control device, and a blanking period.
- the polarization conversion unit was activated. Since the blanking period corresponds to the switching time of the screen, that is, one frame, projection is performed in the same polarization state within one frame by changing the polarization state in the polarization conversion unit during the blanking period. Therefore, according to the laser projection apparatus in the first aspect, the polarization state changes and the speckle state is different in each frame, and these are multiplexed, so the speckle can be reduced. In addition, since there is no change in luminance within one frame, it is possible to perform good image projection. Therefore, it is possible to obtain a better image quality than before.
- the laser projection apparatus of the first aspect is a scanning type, there is an effect that it is possible to achieve downsizing and low power consumption.
- FIG. 1 shows the structure of the laser projection apparatus in embodiment of this invention. It is a timing chart which shows an example of the operation control with respect to the scanning mechanism with which the laser projection apparatus shown in FIG. 1 is equipped. 2 is a timing chart showing an example of control performed by a drive control device provided in the laser projection apparatus shown in FIG. 1 and a graph showing an operation state of a liquid crystal element driven by the control. It is a top view of the liquid crystal element with which the laser projection apparatus shown in FIG. In the laser projection apparatus shown in FIG. 1, it is a figure for demonstrating the example of a change of the polarization state of the laser beam before and behind a liquid crystal element. (A) In the laser projection apparatus shown in FIG.
- Laser scanning projectors that are attracting attention as ultra-compact projectors have a laser light source and scanning means for two-dimensionally scanning the laser light on the screen, and scan the modulated laser light that contains video information. It is a laser projection device that scans an image and projects an image.
- a two-dimensional spatial modulation element such as a liquid crystal panel or DMD (Digital Micromirror Device) is illuminated and a modulated image is projected by a projection lens.
- the laser scanning projector does not require a projection lens, and thus can be reduced in size, and by directly modulating the laser light source, for example, there is no laser emission on a black screen. There is an advantage that low power consumption can be achieved.
- a laser projection apparatus 101 of the present embodiment shown in FIG. 1 corresponds to such a laser scanning projector, and adopts a configuration in which speckles are reduced by generating the above-described speckle states that are different in time. Yes.
- the outline of the speckle reduction effect in the laser projection apparatus 101 having such a configuration will be described below.
- the laser projection apparatus 101 of this embodiment employs a raster scanning method when projecting laser light onto a screen.
- the raster method combines the first direction (main scanning direction) that scans at a high speed and the second direction (sub-scanning direction) that scans at a low speed in comparison with this, or This is a method of drawing scanning lines in the opposite direction. That is, the raster method is a method in which main scanning is performed a plurality of times while sub-scanning is performed once. Accordingly, there is a time called blanking in which the laser does not emit light and the screen is not displayed corresponding to the change of the scanning direction.
- the blanking time includes a period during which the frame moves from one horizontal direction (corresponding to the first direction) to the next horizontal direction and a period during which the frame moves from one frame to the next frame. However, in the present embodiment, it refers to the blanking time that occurs between the latter frames. Therefore, this blanking time corresponds to a screen switching time, and there is a blanking time for each drawing of one frame.
- the polarization state of the laser light is changed during the blanking time.
- the screen in one frame is projected with the same polarization state, while the polarization state is changed and the speckle state is different in each frame. Therefore, by multiplexing these, it is possible to reduce speckles, and since there is no change in luminance within one frame, it is possible to perform good image projection.
- the laser projection apparatus 101 will be specifically described below.
- the laser projection device 101 includes, as basic components, a laser light source 110, an optical system 120 that synthesizes laser light from the laser light source 110, a polarization conversion unit 130, and a reflection unit that reflects the laser light emitted from the optical system 120. 141 and a scanning mechanism 140 that two-dimensionally scans the screen 201 after being reflected at 141.
- an image processing circuit 108 that controls the operation of the laser projection apparatus 101 is connected to the laser projection apparatus 101 in order to display an image on the screen 201 by the laser projection apparatus 101.
- the laser projection apparatus 101 may include the image processing circuit 108.
- the laser light source 110 includes a laser element 111G that generates G (green) light, a laser element 111R that generates R (red) light, and a laser element 111B that generates B (blue) light.
- the laser element 111G is configured by, for example, a semiconductor-excited solid-state laser that generates light having a wavelength of 532 nm using second harmonic generation by a PPLN waveguide.
- the laser element 111R is configured by, for example, a semiconductor laser that generates light having a wavelength of 630 nm.
- the laser element 111B is configured by, for example, a semiconductor laser that generates light having a wavelength of 445 nm.
- the laser element 111R and the laser element 111B may directly modulate the injection current to the laser chip, or an optical modulator such as an AO (acoustic optical) element may be separately provided.
- the laser element 111G may directly modulate the current injected into the excitation laser chip, or an optical modulator such as an AO element may be separately provided. Further, when laser modulation is performed by direct current modulation, high frequency superposition is preferably performed.
- the laser projection apparatus 101 has a configuration in which a laser drive circuit 107 is separately provided as shown in FIG.
- the optical system 120 includes collimating lenses 121G, 121R, and 121B provided corresponding to the laser elements 111G, 111R, and 111B, and dichroic mirrors 122-1, 122- provided corresponding to the collimating lenses 121G, 121R, and 121B. 2 and 122-3.
- the collimating lenses 121G, 121R, and 121B are lenses having an NA (numerical aperture) of 0.4 and a focal length of 4 mm.
- the beam diameter of the collimated laser beam that has passed through is 3.2 mm in diameter. It becomes.
- the dichroic mirror 122-3 is a mirror that reflects the B (blue) laser light generated by the laser element 111B and passing through the collimating lens 121B.
- the dichroic mirror 122-2 is a mirror that transmits the B (blue) laser light and reflects the R (red) laser light generated by the laser element 111R and passing through the collimating lens 121R. . In other words, the dichroic mirror 122-2 synthesizes and emits the B (blue) laser light and the R (red) laser light.
- the dichroic mirror 122-1 combines the B (blue) and R (red) laser lights with the G (green) laser light generated by the laser element 111 G and collimated through the collimating lens 121 G. Thus, the laser beam is emitted as a single white laser beam 123.
- the single white laser beam 123 synthesized is linearly polarized light.
- the laser element 111G, the laser element 111R, and the laser element 111B, the collimating lenses 121G, 121R, and 121B, and the dichroic mirrors 122-1, 122-2, and 122-3 are configured separately. Alternatively, it may be configured integrally as a laser light source unit.
- the scanning mechanism 140 includes a reflecting unit 141 configured by a mirror that reflects the laser light 123 emitted from the optical system 120 as the scanning light 214, and the reflecting unit 141 so that the scanning light 214 scans the screen 201.
- Such a scanning mechanism 140 may have a configuration in which a main scanning mirror and a sub-scanning mirror are separately provided, or may have a configuration in which a main scanning driving mechanism and a sub-scanning driving mechanism are provided in a single mirror.
- the scanning mechanism 140 is configured by a MEMS mirror mechanism including a scanning mirror that vibrates in the horizontal direction and the vertical direction by a piezoelectric element.
- the drive unit 142 of the scanning mechanism 140 will be described in more detail.
- the driving unit 142 drives the reflecting unit 141 so that the scanning light 214 is scanned on the screen 201 by a so-called raster method.
- the reflective portion 141 is inclined between +6 degrees and ⁇ 6 degrees as an example in the vertical direction (sub-scanning direction) perpendicular to the horizontal direction (main scanning direction) on the screen 201, and is inclined with time. The angle is changed.
- the scanning light 214 is sequentially scanned from the upper left end on the screen 201 to the lower right end by repeating the scanning in the horizontal direction and the scanning in the vertical direction, and then returns to the upper left end again.
- the temporal change of the tilt angle of the reflecting portion 141 in the vertical direction is graphed, it is represented by a sawtooth waveform 143 in FIG.
- the time per frame is about 16.7 ms. That is, one period T of the sawtooth waveform 143 shown in FIG. 2 is 16.7 ms.
- 70% of one cycle T is the screen display period 144, that is, the scanning period from the upper left end to the lower right end, and the remaining 30% corresponds to a so-called blanking period 145. In the example, it is 5 ms.
- the blanking period 145 includes a predetermined period including a period during which the scanning light 214 is returned from the lower right end to the upper left end, and an inclination driving start time and an end time. It corresponds to a period.
- the operation of the driving unit 142 with respect to the reflecting unit 141 is not limited to the operation according to the sawtooth waveform 143 described above, and may be an operation having a blanking period 145.
- the screen 201 may be scanned from the upper left end to the lower right end and then returned from the lower right end to the upper left end.
- the screen display period 144 and the blanking period 145 are as shown in the figure.
- the polarization conversion unit 130 is one of the characteristic configurations of the laser projection apparatus 101 of the present embodiment.
- the polarization conversion unit 130 is disposed between the optical system 120 and the scanning mechanism 140, and is optical. This is a component that emits the laser beam 123 emitted from the system 120 to the scanning mechanism 140 with different polarization states.
- Such a polarization conversion unit 130 includes a drive control device 132 as a basic component. In this embodiment, the laser light 123 emitted from the optical system 120 is transmitted and the operation is controlled by the drive control device 132.
- the liquid crystal element 131 is included.
- the liquid crystal element 131 has a structure in which a transparent liquid crystal material is sandwiched between two transparent substrates as a basic structure, and a voltage is applied to the liquid crystal material on the surface on the liquid crystal material side of each of the substrates. Transparent electrodes are provided, and an alignment film is also provided inside each transparent electrode.
- the liquid crystal element 131 configured as described above allows the laser beam 123 emitted from the optical system 120 to pass therethrough and changes the polarization state of the laser beam 123 passing therethrough by changing the alignment state of the liquid crystal material by the drive control device 132. To act.
- the liquid crystal element 131 has a structure that forms a single pixel. Specifically, for example, as shown in FIG. 4, if the liquid crystal element 131 has a square shape, the transparent electrode is formed in a square shape. According to the liquid crystal element 131 having such a configuration, in the transmission region 131a (FIG. 4) of the laser beam 123 in the liquid crystal element 131, the polarization state of the laser beam 123 that passes therethrough is one regardless of where it passes. Like, only one. In other words, the liquid crystal element 131 generates only one polarization state in the passage region 131a of the laser beam 123, and does not generate a plurality of polarization states as disclosed in Patent Document 2.
- the projection image is affected by the influence of diffraction by the electrodes and the deterioration of the straightness of the light beam described above. While the problem of a decrease in resolution occurs, the quality of the light beam is not affected and the resolution in the projected image does not decrease.
- the liquid crystal material provided in the liquid crystal element 131 is a smectic liquid crystal or a ferroelectric material having a relatively short voltage response time compared to a commonly used TN liquid crystal because of the relationship with the operation control by the drive control device 132 described below. LCD is good.
- these liquid crystal materials change the polarization state by birefringence rather than optical rotation like TN liquid crystal materials.
- a ferroelectric liquid crystal is used as the liquid crystal material, the molecular alignment is slightly changed in the direction perpendicular to the voltage application direction depending on whether or not voltage is applied to the liquid crystal element, and a phase difference is generated by the change in birefringence generated thereby.
- the polarization state of the incident beam can be changed.
- the polarization direction can be changed by 90 degrees.
- the amount of birefringence to be changed can be controlled by accurately determining the thickness of the liquid crystal element, the liquid crystal material, and the orientation of the molecular arrangement. Therefore, in the case of the liquid crystal element 131 used in the present embodiment, various parameters of the liquid crystal element 131 may be set so that the incident polarization is switched to two polarization states depending on whether a voltage is applied. As a result, the adjustment of the incident polarization state of the laser beam and the axis of the liquid crystal material can be performed more roughly than in the case of the TN liquid crystal, which is also preferable from this point.
- polarization conversion having birefringence can be used even in the case of incidence of circularly polarized light. In this case, the axial direction of the liquid crystal material can be arbitrarily set, which is preferable.
- an optical crystal that can change the magnitude of birefringence with an applied voltage for example, PLZT (lead lanthanum zirconate titanate) can be used as an element that changes the polarization state.
- PLZT lead lanthanum zirconate titanate
- the drive control device 132 that drives the liquid crystal element 131 configured as described above will be described.
- the drive control device 132 is a device that operates the liquid crystal element 131 during the blanking period 145 to change the polarization state of the laser light 123 emitted from the optical system 120.
- the laser beam 123 is linearly polarized
- the drive control device 132 applies a voltage to the liquid crystal element 131 to change the orientation direction of the liquid crystal material to change the birefringence, thereby changing the linearly polarized light.
- It is converted into a polarization state of 90 degrees different direction, that is, an orthogonal direction.
- the orthogonal means two states opposite to each other when the polarization state is expressed on the Poincare sphere.
- the conversion of the polarization state of the laser beam 123 by the drive control device 132 is not limited to the above-described orthogonal direction, and may be, for example, a direction different by 45 degrees.
- the polarization conversion characteristics can be changed by controlling the drive voltage and the direction of the liquid crystal.
- the correlation of the speckle pattern can be made the most different, and the speckle can be reduced most effectively, which is preferable.
- the drive control device 132 applies a voltage to the liquid crystal element 131 to change the alignment of the liquid crystal material. Specifically, as shown in FIG. 3A, the drive control device 132 changes the voltage applied to the liquid crystal element 131 simultaneously with the start of the blanking period 145 to start the next blanking period 145. Until the same voltage is maintained. In this embodiment, the period for maintaining the voltage corresponds to one period T of the sawtooth waveform 143. Therefore, the polarization state of the scanning light 214 does not change within the screen display period 144.
- a voltage of plus, 0, minus, 0, plus,... To the liquid crystal element 131 as shown in FIG. For example, vertical (horizontal), horizontal (vertical), vertical (horizontal),...
- the positive and negative voltages are alternately applied in order to average the polarization caused by the liquid crystal drive.
- the driving effect is the same for both plus and minus.
- FIG. 3B is a graph showing an outline of the temporal change in the response state of the liquid crystal material with respect to the drive voltage change shown in FIG. 3A when the liquid crystal material in the liquid crystal element 131 is a smectic liquid crystal. It is. As described above, in the present embodiment, it is necessary to change the birefringence magnitude in the blanking period 145 by changing the orientation of the liquid crystal material of the liquid crystal element 131. That is, in this embodiment, the liquid crystal material is required to have a response within 5 ms. On the other hand, the liquid crystal material generally takes more time for response when returning to 0V voltage (falling) than when applying voltage positively or negatively (falling).
- the liquid crystal material in the liquid crystal element 131 is within the blanking period 145, that is, within the above 5 ms, not only at the rising edge but also at the falling edge.
- the orientation state can be converted.
- the direction of the linearly polarized light of the scanning light 214 can be changed by 90 degrees during the blanking period 145 when no screen display is performed, and the polarization of the scanning light 214 is changed within the screen display period 144. Do not change state. Therefore, in the laser projection apparatus 101 of the present embodiment, even when laser light is projected onto a polarization-dependent screen, the screen brightness becomes uniform and resolution in the projected image does not decrease.
- the polarization conversion unit 130 includes the liquid crystal element 131 as described above, but a phase plate, an optical rotator, or the like may be used instead of the liquid crystal element 131. In any case, it is sufficient that the operation is controlled by the drive control device 132 so that the polarization state is changed in the blanking period 145.
- the liquid crystal element 131 having no mechanical drive mechanism is advantageous.
- a slight diffusion due to the liquid crystal structure itself contributes to the reduction of speckle and has an effect other than the polarization multiplexing.
- the modulated laser beams generated and modulated by the respective laser elements 111G, 111R, and 111B are collimated by the respective collimating lenses 121G, 121R, and 121B, and are then transmitted by the respective dichroic mirrors 122-1, 122-2, and 122-3.
- the combined laser beam 123 is incident on the liquid crystal element 131 of the polarization converter 130.
- the polarization state of the laser beam 123 is, for example, the vertical direction (FIG. 1).
- the laser beam 123 incident on the liquid crystal element 131 passes through the liquid crystal element 131 and is irradiated on the reflection unit 141 of the scanning mechanism 140 via the mirror 151.
- the polarization state of the laser beam 123 is converted into the vertical direction or the horizontal direction perpendicular thereto depending on the orientation of the liquid crystal material.
- the laser beam 123 is linearly polarized before and after passing through the liquid crystal element 131.
- the direction of linearly polarized light changes as described above.
- the mirror 151 is a mirror for adjusting the optical path in order to guide the laser beam 123 that has passed through the liquid crystal element 131 to the scanning mechanism 140, and may be unnecessary depending on the device configuration.
- the laser light applied to the reflection unit 141 is scanned in the horizontal direction and the vertical direction with respect to the screen 201 by driving the reflection unit 141 by the drive unit 142 of the scanning mechanism 140. As a result, an image for one frame is projected on the screen 201.
- the image display on the screen 201 displays the input image by the image processing circuit 108 driving the laser driving circuit 107 and the driving unit 142 of the scanning mechanism 140 in synchronization with each other based on the input image data.
- the drive control device 132 of the polarization converter 130 applies a voltage or a voltage of 0 V, and thereby the laser beam 123 transmitted through the liquid crystal element 131 is transmitted.
- the direction of linearly polarized light is linearly polarized light that is changed by 90 degrees from the case of the previous frame.
- the laser light source 110 does not generate laser light.
- the blanking period 145 ends, the laser light source 110 again generates laser light, and scanning of the next frame is started.
- the polarization state of the laser beam 123 transmitted through the liquid crystal element 131 is orthogonal to the polarization state in the previous frame due to the change in the alignment of the liquid crystal material of the liquid crystal element 131. Therefore, scanning for the next frame is performed with the scanning light 214 whose polarization state has changed to the orthogonal state.
- the polarization state is changed in the blanking period 145 in which screen display is not performed, and scanning is performed with the scanning light 214 in which the polarization state changes for each frame.
- the polarization state of the scanning light 214 does not change within the screen display period 144 of one frame.
- the polarization state changes and the speckle state is different. Therefore, by multiplexing these, it is possible to reduce speckles and to perform good image projection since there is no change in luminance within one frame. Therefore, it is possible to obtain a better image quality than before.
- the blanking time is 5 ms and the frame frequency is 60 Hz
- the blanking period (seconds) ⁇ the frame frequency (Hz) is 0.3, which satisfies the above conditional expression.
- the blanking time becomes too short, and depending on the type of liquid crystal element, the response of the polarization conversion unit 130 cannot catch up, and polarization conversion cannot be performed during the blanking time.
- the polarization state changes within the screen due to the change in polarization during the scanning time, resulting in uneven brightness depending on the type of screen.
- drive control in the sub-scanning direction sawtooth wave or triangular wave folding speed
- the screen is distorted due to the speed difference in the sub-scanning direction of the screen, so that a good image projection cannot be performed. From the above points, it is not preferable to exceed the lower limit of the above conditional expression.
- the light incident on the reflection unit 141 of the scanning mechanism 140 is linearly polarized light.
- the present invention is not limited to this.
- a wave plate 162 is provided between the liquid crystal element 131 and the reflecting portion 141, and linearly polarized light emitted from the liquid crystal element 131 is converted into circularly polarized light by the wave plate 162 and reflected. It may enter the portion 141.
- a wave plate 161 is provided between the optical system 120 and the liquid crystal element 131, and the laser beam 123 emitted from the optical system 120 and linearly polarized is circled by the wave plate 161.
- the liquid crystal element 131 It may be polarized and incident on the liquid crystal element 131.
- the light emitted from the liquid crystal element 131 is converted into right circularly polarized light and left circularly polarized light and is incident on the reflecting portion 141.
- a wave plate 161 ′ is provided between the optical system 120 and the liquid crystal element 131, and the linearly polarized laser beam 123 is converted into elliptically polarized light by the wave plate 161 ′.
- the light may enter the element 131.
- the light emitted from the liquid crystal element 131 is converted into right elliptical polarized light and left elliptical polarized light and is incident on the reflecting unit 141. Furthermore, as shown in FIGS. 7 (a) and 7 (b), the right circularly polarized light, the left circularly polarized light, and the right right generated by the configuration in FIGS. 6 (a) and 6 (b).
- the elliptically polarized light and the left elliptically polarized light may be converted to linearly polarized light through the wavelength plate 162 and incident on the reflecting unit 141.
- the liquid crystal element 131 is disposed between the optical system 120 and the scanning mechanism 140.
- the liquid crystal element 131 may be disposed on the light emission side of the reflection unit 141 of the scanning mechanism 140. More specifically, a protective glass is generally attached to the scanning light exit window of the laser projector for the purpose of preventing dust from being reflected on the reflecting portion 141 of the scanning mechanism 140 and preventing the air from swinging. . Therefore, the laser projection device 102 has a configuration in which the protective glass for the scanning light exit window 105 is also used as the liquid crystal element 131. Other configurations in the laser projection apparatus 102 are the same as those in the laser projection apparatus 101 described above.
- Such a laser projection apparatus 102 has an advantage that the number of parts can be reduced as compared with the laser projection apparatus 101 since the protective glass is also used in the liquid crystal element 131.
- the beam passage area is relatively small between the optical system 120 and the scanning mechanism 140 as compared with the light emission side of the reflecting portion 141 of the scanning mechanism 140. Therefore, by disposing the liquid crystal element 131 between the optical system 120 and the scanning mechanism 140 as in the laser projection apparatus 101 shown in FIG. 1, only a relatively small liquid crystal element 131 is required. Compared to the projection device 102, the size can be reduced, and one liquid crystal is combined with the laser beam 123 obtained by synthesizing the three laser beams of B (blue), R (red), and G (green). It is preferable because the element 131 can perform polarization conversion.
- the liquid crystal element 131 since the wavelengths of the laser beams of the three colors are different, it is theoretically difficult to obtain the maximum polarization conversion effect for all the laser beams of the respective colors. Therefore, it is preferable to design the liquid crystal element 131 so that the maximum polarization conversion effect can be obtained with respect to green or red laser light having high human eye sensitivity.
- scanning is performed so that the incident beam incident on the scanning mechanism 140 and the reflected beam reflected by the scanning mechanism 140 are spatially separated.
- a structure in which a beam is incident on the mechanism 140 from an oblique direction, that is, a so-called angle separation system is employed.
- an element for example, a quarter-wave plate that rotates the polarization of the beam by 90 degrees in the reciprocating optical path and a polarizing beam splitter are arranged from the scanning mechanism 140 side.
- a so-called polarization separation system configuration in which the beam incident direction and the reflection direction are substantially the same.
- the liquid crystal element 131 if the liquid crystal element 131 is disposed in the optical path toward the scanning mechanism 140, the polarization state of the beam incident on the polarization beam splitter changes, and the amount of light toward the scanning mechanism 140 changes, which is not preferable. .
- the liquid crystal element 131 needs to be disposed in the optical path after the reflected beam from the scanning mechanism 140 exits the polarization beam splitter.
- the present invention can be applied to a laser projection device that projects an image by deflecting and scanning laser light in two dimensions.
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Abstract
Description
1フレームを形成している間は前記偏光状態を変化させず、前記ブランキング期間に前記偏光変換部を作動させて前記偏光状態を異ならせる駆動制御装置をさらに備えたことを特徴とする。
又、前記偏光変換部は、前記レーザー光源と前記走査機構との間に配置されてもよい。
上記式は良好なスペックル低減と画像投射を両立させるための条件式である。
105 走査光出射窓
110 レーザー光源
120 光学系
130 偏光変換部
131 液晶素子
131a 透過領域
132 駆動制御装置
140 走査機構
141 反射部
142 駆動部
145 ブランキング期間
201 スクリーン
214 走査光
Claims (10)
- レーザー光を発生し変調するレーザー光源と、該レーザー光源から出射されたレーザー光を2次元的に走査して1フレームを形成し各フレーム間にブランキング期間を有してスクリーンに画像投影する走査機構と、前記レーザー光源が出射する光の偏光状態を異ならせて前記スクリーンへ出射する偏光変換部とを有するレーザー投射装置であって、
1フレームを形成している間は前記偏光状態を変化させず、前記ブランキング期間に前記偏光変換部を作動させて前記偏光状態を異ならせる駆動制御装置をさらに備えたことを特徴とするレーザー投射装置。 - 前記偏光変換部は、前記レーザー光の透過領域において単一の偏光状態を形成する液晶素子を有することを特徴とする請求項1記載のレーザー投射装置。
- 前記液晶素子における液晶は、スメクティック液晶又は強誘電液晶であることを特徴とする請求項2記載のレーザー投射装置。
- 以下の条件式を満足することを特徴とする請求項1から3のいずれかに記載のレーザー投射装置。
0.1<ブランキング期間(秒)×フレーム周波数(Hz)<0.4 - 前記偏光変換部は、前記レーザー光源と前記走査機構との間に配置されることを特徴とする請求項1から4のいずれかに記載のレーザー投射装置。
- 前記偏光変換部は、前記走査機構と前記スクリーンとの間に配置される光出射窓に備わることを特徴とする請求項1から4のいずれかに記載のレーザー投射装置。
- 前記偏光変換部にて異ならせる前記偏光状態は、互いに直交する状態であることを特徴とする請求項1から6のいずれかに記載のレーザー投射装置。
- 前記レーザー光源として波長の異なるレーザー光を射出する複数のレーザー光源と、前記複数のレーザー光源からのレーザー光を合成する光学系と、をさらに備えることを特徴とする請求項1から7のいずれかに記載のレーザー投射装置。
- 前記複数のレーザー光源はそれぞれ、青色光、緑色光、赤色光の3つのレーザー光を発生し、前記偏光変換部は、緑色光又は赤色光のレーザー光に対して互いに直交する偏光状態となるように偏光を変換することを特徴とする請求項8記載のレーザー投射装置。
- 前記偏光変換部は、前記光学系と前記走査機構との間に配置されることを特徴とする請求項1から4のいずれかに記載のレーザー投射装置。
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US13/498,319 US8960914B2 (en) | 2009-09-28 | 2010-09-14 | Laser projection apparatus with speckle reduction |
JP2011532968A JP5673544B2 (ja) | 2009-09-28 | 2010-09-14 | レーザー投射装置 |
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JP2009222172 | 2009-09-28 |
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JP2011215172A (ja) * | 2010-03-31 | 2011-10-27 | Hitachi Consumer Electronics Co Ltd | レーザープロジェクタ |
WO2013009536A2 (en) * | 2011-07-11 | 2013-01-17 | Microvision, Inc. | Active polarization switch for speckle reduction in laser projection sources |
JP2013015632A (ja) * | 2011-07-01 | 2013-01-24 | Canon Inc | 偏光変換素子およびそれを用いた画像表示装置 |
JP2013047704A (ja) * | 2011-08-27 | 2013-03-07 | Denso Corp | ヘッドアップディスプレイ装置 |
JP2017076044A (ja) * | 2015-10-14 | 2017-04-20 | ホシデン株式会社 | レーザ光を用いた投射型表示装置及び該投射型表示装置を用いた車載用ヘッドアップディスプレイ |
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JP5609369B2 (ja) * | 2010-07-23 | 2014-10-22 | 船井電機株式会社 | 画像表示装置 |
JP2013041236A (ja) * | 2011-07-01 | 2013-02-28 | Hitachi Media Electoronics Co Ltd | 走査型画像表示装置及び走査型投影装置 |
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US8960914B2 (en) | 2015-02-24 |
US20120182487A1 (en) | 2012-07-19 |
JP5673544B2 (ja) | 2015-02-18 |
JPWO2011037039A1 (ja) | 2013-02-21 |
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