WO2012111698A1 - 走査型画像表示装置及びその画像表示方法 - Google Patents
走査型画像表示装置及びその画像表示方法 Download PDFInfo
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- WO2012111698A1 WO2012111698A1 PCT/JP2012/053513 JP2012053513W WO2012111698A1 WO 2012111698 A1 WO2012111698 A1 WO 2012111698A1 JP 2012053513 W JP2012053513 W JP 2012053513W WO 2012111698 A1 WO2012111698 A1 WO 2012111698A1
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- scanning
- image display
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- pixel
- light
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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
- G03B21/53—Means for automatic focusing, e.g. to compensate thermal effects
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/02—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes by tracing or scanning a light beam on a screen
- G09G3/025—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes by tracing or scanning a light beam on a screen with scanning or deflecting the beams in two directions or dimensions
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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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
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
- G02B26/105—Scanning systems with one or more pivoting mirrors or galvano-mirrors
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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
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0237—Switching ON and OFF the backlight within one frame
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/08—Details of timing specific for flat panels, other than clock recovery
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
Definitions
- the present invention relates to an image display device, and more particularly to a scanning image display device that displays an image on a projection surface by scanning a light beam.
- Incoherent light for example, white light
- a white light source such as a halogen lamp or a high-pressure mercury lamp
- a planar display element such as a liquid crystal light valve
- the emitted light from the display element is emitted by a projection lens.
- a projection-type image display device that displays an image by enlarging and projecting on a screen is known.
- a discharge lamp such as a halogen lamp or a high-pressure mercury lamp used as a light source has a problem that a large amount of power is consumed.
- a projection type image display device provided with a planar display element such as a liquid crystal light valve is inevitably large, it is difficult to reduce the size of the device.
- the image formed by the display element may not be projected within the focal depth of the projection lens, and the projected image may not be in focus.
- the user needs to perform an operation of adjusting the focus of the projection lens according to the distance from the projection lens to the screen. Such a focus adjustment operation impairs convenience for the user.
- a scanning image display device has been proposed in which a laser light source is used as a light source, and laser light emitted from the laser light source is two-dimensionally scanned and projected onto a screen (Patent Documents 1 and 2). reference).
- FIG. 1A shows a configuration of a projection display device described in Patent Document 1.
- the projection display device includes light sources 111, 112, 113, a color synthesizing element 114, a collimator lens 115, and optical scanning elements 116, 117.
- the light source 111 is a red semiconductor laser
- the light source 112 is a blue semiconductor laser
- the light source 113 is a green solid laser.
- the green solid laser uses a nonlinear optical crystal to obtain green light by extracting the second harmonic from the emitted light of the infrared semiconductor laser.
- the color composition element 114 synthesizes light of red, blue, and green colors from the light sources 111 to 113.
- the light beam from the color synthesizing element 114 is incident on the optical scanning element 116 via the collimator lens 115.
- the optical scanning element 116 performs optical scanning in the horizontal direction. Light from the optical scanning element 116 enters the optical scanning element 117. The optical scanning element 117 performs optical scanning in the vertical direction.
- a high-definition image can be displayed by causing the collimator lens 115 to match the beam waist position to the projection surface.
- FIG. 1B shows the configuration of the image display device described in Patent Document 2.
- the image display device has a light source unit 101G, a condensing optical system LN1 that condenses the beam light from the light source unit 101G, and a light beam condensed by the condensing optical system LN1 on the screen 110. And a reflection mirror 202 that reflects toward the screen.
- the condensing optical system LN1 forms a beam waist at a position farther from the reflection mirror 202 than an intermediate position between the reflection mirror 202 and the screen 110.
- the beam diameter on the reflection mirror 202 can be reduced, and the expansion of the beam diameter on the screen 110 can be suppressed. Therefore, the reflection mirror 202 can be reduced in size, and a high-definition image can be achieved. Can be displayed.
- a micromechanical mirror is used as the optical scanning element 116 or the reflection mirror 202.
- the micromechanical mirror includes a mirror surface, a first substrate on which the mirror surface is fixed via a torsion bar, a second substrate disposed to face the first substrate, and a second substrate. And a core made of a magnetic material formed on the surface on the first substrate side.
- the mirror surface is in a rotational resonance state by the electromagnetic force generated in the core.
- An electrostatic actuator or an electromagnetic actuator can be used as means for bringing the mirror surface into a rotational resonance state.
- Patent Documents 1 and 2 have the following problems.
- FIG. 2A shows a main part of a scanning display device in which a beam waist is disposed on or near a projection surface.
- This main part corresponds to the main part of the apparatus described in Patent Documents 1 and 2, and includes a light source 121, a condensing lens 122 arranged in order in the traveling direction of the laser beam emitted from the light source 121, and scanning. And a mirror 123.
- the projection surface 124 is arranged in the vicinity of the position corresponding to the focal length of the condensing lens 122, and the laser beam emitted from the light source 121 is condensed by the condensing lens 122, so that the projection surface 124 or the projection surface 124 is collected.
- a beam waist can be arranged in the vicinity.
- the effective diameter (radius) of the scanning mirror 123 is ⁇
- the propagation distance is z
- the beam waist radius formed at a distance where the amplitude value falls to 1 / e with respect to the maximum value is ⁇ 0
- ⁇ is the wavelength of the laser beam
- ⁇ is the circumference.
- the beam numerical aperture is given by ⁇ / z.
- the beam diameter on the projection surface 124 when the scanning angle ⁇ is 0 and the beam waist is disposed in the optical path length L (0) is ⁇ 0 .
- the optical path length L (0) is the distance from the surface of the scanning mirror 123 to the projection surface 124 in the optical path of the central beam of the laser beam.
- the projection distance f is a distance from the condenser lens 122 to the projection surface 124 and is determined by the focal length of the condenser lens 122. Assuming that the distance from the principal point of the condenser lens 122 to the surface of the scanning mirror 123 is d, the optical path length L (0) is a value obtained by subtracting the distance d from the projection distance f.
- the optical path length L ( ⁇ ) is Is given by Equation 3 below.
- the optical path length L ( ⁇ ) becomes larger than the optical path length L (0), so that the propagation distance z in Equation 1 increases, and as a result, the value of the beam diameter is ⁇ (L ( 0)) to ⁇ (L ( ⁇ )) (first phenomenon).
- the beam diameter on the projection surface 124 increases, and as a result, the screen resolution decreases.
- 3A and 3B are diagrams showing the relationship between the beam shape and the image resolving power.
- the beam shape is defined by the square of the amplitude distribution of the wave on the cross section perpendicular to the optical axis, that is, the intensity distribution.
- FIG. 3A shows the relationship between the beam shape function b (x) when the beam diameter is equal to the pixel pitch P and the convolution function G (x) of the spatial expansion function T (x) of the modulation waveform M (t).
- the modulation waveform M (t) is omitted for convenience.
- the duty ratio is 50% and the laser beam is subjected to rectangular wave modulation under the condition that the light emission time ⁇ t and the extinction time ⁇ t are respectively P / V
- the spatial expansion function T (x) is 2 of the pixel pitch P.
- the resolving power contrast C of the convolution function G (x) serving as a display image is 91%.
- the resolution contrast C of the convolution function G (x) is 71%.
- Patent Documents 1 and 2 have a problem that the resolution at the periphery of the screen is low because the beam diameter on the screen is enlarged as the scanning angle increases.
- the torsion bar (hinge) may break, and it is difficult to ensure the durability and reliability of the apparatus.
- An object of the present invention is to solve the above-described problems and to suppress a decrease in resolving power when the beam diameter on the projection surface is enlarged as the scanning angle is increased and an image thereof. To provide a display method.
- a solid-state light source a scanning unit that scans a light beam emitted from the solid-state light source and displays an image on a projection surface, and a pixel of the image
- a scanning type image display apparatus having control means for controlling the light emission time of the light beam from the solid state light source for each pixel and controlling the light emission time for each pixel according to the scanning angle of the scanning means.
- an image display method performed in a scanning image display device that scans a light beam to display an image on a projection surface, and emits the light beam for each pixel of the image.
- an image display method for controlling time and controlling the light emission time for each pixel according to a scanning angle of the light beam is provided.
- an image performed in a scanning image display device that includes a variable focal length lens having a variable focal length and displays an image on a projection surface by scanning a light beam from the variable focal length lens.
- the light emission time of the light beam is controlled for each pixel of the image, the light emission time for each pixel is controlled according to the scanning angle of the light beam, and the focus of the variable focus lens
- An image display method for controlling the distance according to the scanning angle is provided.
- FIG. FIG. 10 is a schematic diagram illustrating a configuration of an image display device described in Patent Document 2. It is a schematic diagram which shows the principal part of the scanning-type display apparatus by which a beam waist is arrange
- FIG. 1 is a block diagram illustrating a configuration of a scanning image display apparatus according to a first embodiment of the present invention.
- FIG. 5 is a characteristic diagram showing an example of characteristic data indicating a difference in optical path length with respect to a scanning angle and beam spread by oblique projection used in the scanning image display apparatus shown in FIG. 4.
- FIG. 5 is a schematic diagram showing a relationship between a scanning angle and a modulated waveform signal in the scanning image display apparatus shown in FIG. 4.
- FIG. 5 is a characteristic diagram showing a change in duty ratio of a modulated waveform signal used in the scanning image display device shown in FIG. 4.
- FIG. 5 is a waveform diagram showing an example of a modulated waveform signal used in the scanning image display device shown in FIG. 4.
- the beam shape function b (x), the spatial expansion function T (x), and the convolution function G (x) in a state where the beam diameter is expanded to 4/3 times the pixel pitch without modulation control according to the scanning angle. It is a characteristic view which shows a relationship.
- the beam shape function b (x), the spatial expansion function T (x), and the convolution function G (x) in a state where the beam diameter is expanded to 4/3 times the pixel pitch.
- FIG. It is a figure for demonstrating the relationship between the beam shape at the time of scanning at a fixed speed, and a modulation signal.
- FIG. 10 is a schematic diagram showing a change in focal length and a change in beam diameter of the variable focus lens in the scanning image display apparatus shown in FIG. 9.
- FIG. 10 is a schematic diagram showing a change in focal length and a change in beam diameter of the variable focus lens in the scanning image display apparatus shown in FIG. 9.
- FIG. 10 is a schematic diagram illustrating a state of a variable focus lens when the scanning angle ⁇ is increased in the scanning image display apparatus illustrated in FIG. 9.
- FIG. 10 is a schematic diagram illustrating a state of the variable focus lens when the scanning angle ⁇ is 0 in the scanning image display apparatus illustrated in FIG. 9.
- FIG. 4 is a block diagram showing the configuration of the scanning image display apparatus according to the first embodiment of the present invention.
- the scanning image display apparatus is of a rear projection type, and includes a light source 1, a condenser lens 2, a scanning unit 3, a lookup table 6, a control unit 10, and a projection surface 9. .
- the distance from the scanning means 3 to the projection surface 9 is fixed.
- the control means 10 controls the operation of the entire scanning image display apparatus, and has a laser modulation means 4 and a modulation waveform / output calculation means 5.
- the video signal 7 from the external device is supplied to the modulation waveform / output calculation means 5.
- a synchronization signal 8 for achieving vertical synchronization and horizontal synchronization in image display by the video signal 7 is supplied from an external device to the modulation waveform / output calculation means 5 and the scanning means 3.
- the external device is a video supply device such as a personal computer.
- the light source 1 is a solid light source typified by a semiconductor laser.
- the condensing lens 2 and the scanning means 3 are arranged in this order in the traveling direction of the laser beam from the light source 1.
- the condensing lens 2 condenses the laser beam from the light source 1.
- the scanning means 3 is a resonance type scanning mirror represented by a micromechanical mirror.
- the scanning unit 3 scans the laser beam condensed by the condenser lens 2 according to the synchronization signal 8 and displays an image on the projection surface 9.
- the scanning unit 3 performs two-dimensional scanning in the horizontal direction and the vertical direction, the horizontal scanning is performed based on the horizontal synchronizing signal, and the vertical scanning is performed based on the vertical synchronizing signal.
- the look-up table 6 stores characteristic data indicating an optical path length difference with respect to a scanning angle and beam spread (change in beam diameter) due to oblique projection. This characteristic data can be calculated based on the above-described equations 1 to 4.
- the characteristic data is data indicating beam divergence (change in beam diameter) for each scanning angle when the scanning angle ⁇ is changed stepwise in the range from 0 ° to the maximum angle ⁇ max. It is a table.
- the step width of the scanning angle is, for example, 0.5 °, but is not limited thereto.
- the step width of the scanning angle can be set as appropriate.
- the beam divergence data includes the influence of the difference between the optical path length L ( ⁇ ) and the optical path length L (0) shown in FIG. 2A and the influence of the oblique projection shown in FIG. 2B.
- FIG. 5 shows an example of characteristic data based on such beam spread data.
- a curve (2 ⁇ (L ( ⁇ ))) indicated by a solid line indicates a beam spread including the influence of the optical path length difference shown in FIG. 2A.
- a curve (2 ⁇ (L ( ⁇ ) / cos ⁇ )) indicated by a broken line shows a beam spread including the influence of the optical path length difference shown in FIG. 2A and the influence of the oblique projection shown in FIG. 2B.
- the lookup table 6 is created based on the characteristic data corresponding to the curve indicated by the broken line.
- the screen is divided into two with reference to the irradiation position on the projection surface 9 when the scanning angle ⁇ is 0, and the 1/2 screen size is 150 mm, 1 / The number of two pixels is 512, and the pixel pitch is 293 ⁇ m (corresponding to a value obtained by dividing the screen size by the number of pixels).
- the beam diameter ⁇ on the mirror surface of the scanning means 3 is 1 mm
- the wavelength ⁇ of the laser beam is 640 nm
- the optical path length L (0) is 400 mm
- the maximum deflection angle of the scanning angle is 20.5 °.
- the beam diameter on the projection surface 9 (broken line: 2 ⁇ (L ( ⁇ )) / cos ⁇ ) is 348 ⁇ m when the scanning angle ⁇ is 0, which is about 1.2, which is the pixel pitch of 293 ⁇ m. Is double.
- the beam diameter when the scanning angle ⁇ is 20.5 ° is 377 ⁇ m, which is about 1.3 times the pixel pitch of 293 ⁇ m.
- the modulation waveform / output calculation means 5 reads the characteristic data held in the lookup table 6 based on the synchronization signal 8. By synchronizing the readout of the characteristic data and the scanning by the scanning unit 3 with the synchronization signal 8, the modulation waveform / output calculation unit 5 can acquire the scanning angle for each pixel of the image based on the video signal 7.
- the vertical sync signal included in the sync signal 8 starts.
- the point and the end point can be determined, respectively, and the position (irradiation timing) of each pixel can be determined based on the horizontal synchronization signal. Since the scanning angle of each pixel is known in advance, the scanning angle of each pixel can be determined from the position (irradiation timing).
- the modulation waveform / output calculation means 5 acquires the beam diameter corresponding to the scanning angle of the scanning means 3 based on the characteristic data read from the lookup table 6, and calculates the modulation time based on the acquired beam diameter. Then, a modulated waveform signal is generated based on the calculation result. Further, the modulation waveform / output calculation means 5 generates an intensity modulation signal based on the video signal 7.
- FIG. 6A shows the relationship between the scanning angle and the modulated waveform signal.
- This modulation waveform signal has a modulation waveform in which the modulation time T composed of the light emission time t1 and the extinction time t2 changes according to the scanning angle ⁇ .
- the light emission time t1 corresponds to one pixel.
- the modulation time T is shortened as the scanning angle ⁇ increases so that the scanning speed of the laser beam on the projection surface 9 is constant.
- FIG. 6B shows a change in the duty ratio of the modulation waveform signal.
- the vertical axis represents the modulation duty ratio
- the horizontal axis represents the scanning angle ⁇ .
- the modulation duty ratio is a ratio between the light emission time t1 and the extinction time t2. As shown in FIG. 6B, the modulation duty ratio decreases as the scanning angle ⁇ increases.
- the amplitude of the modulation waveform may be changed according to the scanning angle. Specifically, the amplitude of the modulation waveform is increased as the scanning angle increases. Thereby, the energy of the laser beam per pixel becomes constant.
- the modulation waveform signal and the intensity modulation signal generated by the modulation waveform / output calculation means 5 are supplied to the laser modulation means 4.
- the modulation waveform / output calculation means 5 is a modulation signal obtained by adding an intensity modulation signal to the modulation waveform signal (specifically, a signal obtained by changing the amplitude of the modulation waveform shown in FIG. 6C based on the video signal 7). May be supplied to the laser modulation means 4.
- the laser modulation unit 4 controls the emission time of the laser beam emitted from the light source 1 based on the modulation waveform signal from the modulation waveform / output calculation unit 5.
- the laser modulation unit 4 controls the intensity of the laser beam emitted from the light source 1 based on the intensity modulation signal from the modulation waveform / output calculation unit 5.
- the laser modulation means 4 controls current supply (current supply amount and current supply time) to the semiconductor laser based on the modulation waveform signal and the intensity modulation signal.
- the laser modulation means 4 has a modulator that modulates the laser beam from the light source 1, the transmittance of the modulator is controlled based on the modulation waveform signal and the intensity modulation signal.
- the scanning image display apparatus of the present embodiment even when the beam diameter on the projection surface 9 is increased by increasing the scanning angle by controlling the emission time of the laser beam according to the scanning angle, The resolving power can be maintained at the resolution before the scanning angle is increased (that is, the resolution when the scanning angle ⁇ is 0).
- FIG. 7A shows a beam shape function b (x), a spatial expansion function T (x), and a convolution function G (x) in a state where the beam diameter is expanded to 4/3 times the pixel pitch without the control of the laser modulation means 4.
- FIG. 7A The definitions of the beam shape function b (x), the spatial expansion function T (x), and the convolution function G (x) are as described above.
- the resolution contrast C of the convolution function G (x) is 71% due to the expansion of the beam diameter, and the resolution of the image is low.
- FIG. 7B shows the beam shape function b (x), the spatial expansion function T (x), and the convolution function when the beam diameter is expanded to 4/3 times the pixel pitch when the control of the laser modulation means 4 is applied. It is a characteristic view which shows the relationship with G (x).
- the laser modulation means 4 is based on a modulated waveform signal in which the laser beam emission time t1 is set to a value of 1 / 2 ⁇ t and the extinction time t2 is set to a value of 3 / 2 ⁇ t. Controls the emission time of the laser beam.
- the resolving power contrast C of the convolution function G (x) serving as the display image is 91%, and a resolving power equivalent to that when the beam diameter is the same as the pixel pitch (FIG. 3A)) can be obtained.
- the resolution contrast is equal to or greater than that when the beam diameter is equal to the pixel pitch. Can be obtained.
- FIG. 8A is a diagram for explaining the relationship between the beam shape and the modulation signal when scanning is performed at the speed V.
- the convolution function G (x) of the display image is given by the following expression 6 expressed by the convolution integral of the beam shape function b (x) and the spatial expansion function T (x).
- N indicates the number of pixels.
- modulation control is performed so as to shorten the laser beam emission time t1.
- FIG. 8C shows the relationship between the beam shape and the modulation signal when such modulation control is performed.
- the light emission time t1 is a value of P / 2
- the extinction time t2 is a value of (3/4) ⁇ P.
- the resolving power contrast C of the convolution function G (x) of the display image becomes the same value as that shown in FIG. 8A.
- the scanning image display apparatus of the present embodiment it is possible to suppress a decrease in resolving power when the beam diameter on the projection surface increases with an increase in scanning angle.
- the beam diameter on the projection surface can be set to a value corresponding to the pixel pitch.
- the moment of inertia in the direction perpendicular to the rotation axis increases in proportion to the cube of the mirror diameter, and at least 2.2 times the driving force (torque) is required. As a result, power consumption increases.
- the moment of inertia is further increased because the thickness of the mirror is increased to increase the rigidity. For this reason, when the scanning angle is increased, it is necessary to apply a larger driving force. As a result, the moment of inertia exceeds the torsion yield point of the torsion bar, and the torsion bar may break.
- the resolution contrast can be maintained without increasing the effective diameter of the mirror surface of the scanning means 3. Therefore, it is not necessary to produce a scanning mirror having a large moment of inertia, and the durability and reliability of the apparatus can be ensured.
- the scanning angle ⁇ means one or both of a horizontal scanning angle and a vertical scanning angle.
- the light emission time and intensity control according to the scanning angle is performed on the pair in one of the horizontal direction and the vertical direction.
- the light emission time and intensity are controlled according to the scanning angle in each of the horizontal and vertical directions.
- the look-up table 6 includes first characteristic data indicating the correspondence between the beam spread based on the optical path length difference and the scanning angle, and the second characteristic indicating the correspondence between the beam spread due to the oblique projection and the scanning angle. At least one of the data may be stored.
- the first characteristic data is stored in the lookup table 6, it is possible to suppress a decrease in resolution due to the effect of the optical path length difference shown in FIG. 2A.
- the second characteristic data is stored in the lookup table 6, it is possible to suppress a decrease in resolution due to the influence of the oblique projection shown in FIG. 2B.
- FIG. 9 is a block diagram showing the configuration of the scanning image display apparatus according to the second embodiment of the present invention.
- the image display apparatus replaces the condenser lens 2 with a variable focus lens 41, and controls the variable focus lens 41 and adds a focus control means 42, so that the scanning image display according to the first embodiment is added. Different from the device.
- the modulation waveform output calculation unit 5 calculates a focal length corresponding to the scanning angle ⁇ of the scanning unit 3 based on the characteristic data acquired from the lookup table 6 and supplies the focal length calculation result to the focus control unit 42. .
- the relationship between the scanning angle ⁇ of the scanning unit 3 and the focal length of the variable focus lens 41 can be calculated based on the above-described equation 3.
- the calculation of the focal length in the modulation waveform output calculation means 5 and the transmission of the calculation result are performed in synchronization with the synchronization signal 8.
- the focus control unit 42 controls the focal length of the variable focus lens 41 based on the focal length calculation result from the modulation waveform output calculation unit 5.
- FIG. 10A schematically shows a change in the focal length of the variable focus lens 41 and a change in the beam diameter.
- the focus control means 42 controls the focal length of the variable focus lens 41 according to the scanning angle ⁇ .
- FIG. 10B shows the state of the variable focus lens 41 when the scanning angle ⁇ is increased
- FIG. 10C shows the state of the variable focus lens 41 when the scanning angle ⁇ is zero.
- 10B and 10C includes a condensing lens 55 and a diverging lens 56, and an interval ⁇ between the condensing lens 55 and the diverging lens 56 can be adjusted.
- the interval ⁇ is adjusted using, for example, an electromagnetic actuator.
- various actuators such as an electrostatic actuator can be used in addition to the electromagnetic actuator.
- the focus control means 42 sets the interval ⁇ between the condenser lens 55 and the diverging lens 56 to a predetermined value as shown in FIG. 10C.
- the focus control means 42 makes the interval ⁇ between the condenser lens 55 and the diverging lens 56 smaller than a predetermined value according to the change.
- the beam waist is always positioned on the projection surface 9 in the entire scanning angle ⁇ range, so the influence of the optical path length difference (first phenomenon shown in FIG. 2A). Can be reduced. As a result, the spread of the beam diameter includes only the influence of the oblique projection (second phenomenon shown in FIG. 2B).
- variable focus lens 41 may have any configuration as long as the focal length can be changed.
- the look-up table 6 stores characteristic data indicating the relationship between the change in scanning angle and the beam spread due to oblique projection.
- the beam spread data includes the influence of the oblique projection shown in FIG. 2B. This characteristic data can also be calculated based on the equations 1 to 4 described above.
- the characteristic data is a table of beam spread data for each scanning angle when the scanning angle ⁇ is changed stepwise in the range from 0 ° to the maximum angle ⁇ max.
- the step width of the scanning angle is, for example, 0.5 °, but is not limited thereto.
- the modulation waveform / output calculation means 5 reads the characteristic data held in the lookup table 6 in synchronization with the synchronization signal 8.
- the modulation waveform / output calculation means 5 generates a modulation waveform signal based on the characteristic data read from the lookup table 6 and generates an intensity modulation signal based on the video signal 7.
- the laser modulation unit 4 controls the emission time of the laser beam emitted from the light source 1 based on the modulation waveform signal from the modulation waveform / output calculation unit 5.
- the laser modulation unit 4 controls the intensity of the laser beam emitted from the light source 1 based on the intensity modulation signal from the modulation waveform / output calculation unit 5.
- the emission time and intensity of the laser beam emitted from the light source 1 are controlled according to the scanning angle, thereby suppressing the influence of beam spread due to oblique projection, and
- the focal length of the variable focus lens 41 is controlled according to the scanning angle, it is possible to suppress the influence of the beam spread due to the optical path length difference. Therefore, the scanning image display apparatus according to the present embodiment also has the same effects as those of the first embodiment.
- the scanning angle ⁇ means one or both of a horizontal scanning angle and a vertical scanning angle.
- the control of the emission time and intensity of the light beam according to the scanning angle and the control of the focal length according to the scanning angle are performed on one pair in the horizontal direction and the vertical direction, respectively.
- the light emission time and intensity control according to the scanning angle and the focal length control according to the scanning angle are performed in the horizontal direction and the vertical direction, respectively.
- the light source 1 includes a red laser light source, a green laser light source, and a blue laser light source.
- the beam diameter of each color laser light source is 1000 ⁇ m.
- the red laser light source is a semiconductor laser having a wavelength of 640 nm.
- the blue laser light source is a semiconductor laser having a wavelength of 440 nm.
- the red laser light source and the blue laser light source are modulated by current control.
- the green laser light source is a laser light source that uses the second harmonic (532 nm) of an infrared laser having a wavelength of 1064 nm.
- the green laser light source is modulated using an acousto-optic element.
- the focal length of the condenser lens 2 is 400 mm.
- the scanning unit 3 includes a resonant micromechanical scanning element that performs horizontal scanning and an electromagnetically driven galvanometer mirror that performs vertical scanning.
- the resonant micromechanical scanning element is driven based on a drive signal having a frequency of 27 kHz, and the deflection angle is ⁇ 20 °.
- the resonant micromechanical scanning element has a circular mirror having a diameter of 1500 ⁇ m that can withstand driving at a frequency of 27 kHz.
- the electromagnetically driven galvanometer mirror is driven based on a sawtooth wave drive signal having a frequency of 60 Hz, and its deflection angle is ⁇ 15 °.
- the electromagnetically driven galvanometer mirror has a rectangular mirror of 1500 ⁇ m ⁇ 6000 ⁇ m.
- the image definition is 1024 pixels in the horizontal direction and 768 pixels in the vertical direction. However, the image definition is not limited to this number of pixels, and other numbers of pixels may be applied.
- the screen size is 300 cm in the horizontal direction and 200 cm in the vertical direction at a projection distance of 400 mm.
- light emission timing and intensity control are performed in units of 1 ns that is 1/10 or less of the pixel clock (15.4 ns) in synchronization with the scanning element.
- the resolving power could be maintained even when the beam diameter on the projection surface 9 was enlarged as the scanning angle increased. Also, the resolution contrast could be maintained without increasing the effective diameter of the scanning mirror. Furthermore, since it is not necessary to produce a scanning mirror having a large moment of inertia, it is possible to ensure the durability and reliability of the apparatus.
- the green laser light source may be modulated by modulating the infrared semiconductor laser and converting it to the second harmonic.
- a fiber laser or a semiconductor laser may be used as the green laser light source.
- various optical modulators such as a grating type MEMS modulator, a waveguide type modulator, and an electro-optic crystal may be used.
- an acousto-optic element for horizontal scanning and vertical scanning, an acousto-optic element, an electro-optic crystal, or the like may be used, or an optical system that increases the touch angle with a prism using a photonic crystal may be used.
- the beam deflection unit (mirror, etc.) of each element for horizontal scanning and vertical scanning may be of any size and shape as long as it is larger than the collimated beam diameter.
- a scanning image display apparatus includes a solid-state light source, a scanning unit that scans a light beam emitted from the solid-state light source and displays an image on a projection surface, and each pixel of the image.
- Control means for controlling the light emission time of the light beam from the solid-state light source and controlling the light emission time for each pixel in accordance with the scanning angle of the scanning means.
Abstract
Description
2 集光レンズ
3 走査手段
4 レーザー変調手段
5 変調波形・出力算出手段
6 ルックアップテーブル
7 映像信号
8 同期信号
(第一の実施形態)
図4は、本発明の第一の実施形態の走査型画像表示装置の構成を示すブロック図である。
(第二の実施形態)
図9は、本発明の第二の実施形態の走査型画像表示装置の構成を示すブロック図である。
本発明の他の実施形態の走査型画像表示装置は、固体光源と、上記固体光源から出射された光ビームを走査して被投射面上に画像を表示する走査手段と、上記画像の画素毎に上記固体光源からの光ビームの発光時間を制御するとともに、各画素に対する上記発光時間を上記走査手段の走査角に応じて制御する制御手段と、を有する。
Claims (9)
- 固体光源と、
前記固体光源から出射された光ビームを走査して被投射面上に画像を表示する走査手段と、
前記画像の画素毎に前記固体光源からの光ビームの発光時間を制御するとともに、各画素に対する前記発光時間を前記走査手段の走査角に応じて制御する制御手段と、を有する走査型画像表示装置。 - 前記走査角に対する前記被投射面上のビーム径の変化を示すデータが格納されたルックアップテーブルを、さらに有し、
前記制御手段は、前記ルックアップテーブルを参照して、前記走査角に応じた前記ビーム径を取得し、該取得したビーム径に基づいて前記発光時間を算出する、請求項1に記載の走査型画像表示装置。 - 前記制御手段は、
前記ビーム径から算出した前記発光時間に基づいて前記光ビームを変調するための変調波形信号を生成する算出手段と、
前記変調波形信号に基づいて、前記光ビームの変調制御を行う変調手段と、を有する、請求項2に記載の走査型画像表示装置。 - 前記算出手段は、前記変調波形信号の空間展開関数の畳み込み積分値により求まる解像力コントラストが前記各画素において一定となるように前記変調波形信号を生成する、請求項3に記載の走査型画像表示装置。
- 前記算出手段は、前記各画素における前記発光時間内に照射される光エネルギーが一定となるように前記変調波形信号の振幅を決定する、請求項3または4に記載の走査型画像表示装置。
- 前記固体光源からの光ビームを集光する、焦点距離が可変の可変焦点レンズをさらに有し、
前記制御手段は、前記可変焦点レンズの焦点距離を前記走査角に応じて制御する焦点制御手段をさらに備える、請求項1から5のいずれか1項に記載の走査型画像表示装置。 - 前記焦点制御手段は、前記走査手段のいずれの走査角においても、前記可変焦点レンズの焦点が前記被投射面上に位置するように前記焦点距離を制御する、請求項6に記載の走査型画像表示装置。
- 光ビームを走査して被投射面に画像を表示する走査型画像表示装置において行われる画像表示方法であって、
前記画像の画素毎に前記光ビームの発光時間を制御するとともに、各画素に対する前記発光時間を前記光ビームの走査角に応じて制御する、画像表示方法。 - 焦点距離が可変の可変焦点レンズを備え、該可変焦点レンズからの光ビームを走査して被投射面に画像を表示する走査型画像表示装置において行われる画像表示方法であって、
前記画像の画素毎に前記光ビームの発光時間を制御するとともに、各画素に対する前記発光時間を前記光ビームの走査角に応じて制御し、かつ、前記可変焦点レンズの焦点距離を前記走査角に応じて制御する、画像表示方法。
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