WO2023112485A1 - Image display device and light source control circuit - Google Patents

Image display device and light source control circuit Download PDF

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Publication number
WO2023112485A1
WO2023112485A1 PCT/JP2022/039381 JP2022039381W WO2023112485A1 WO 2023112485 A1 WO2023112485 A1 WO 2023112485A1 JP 2022039381 W JP2022039381 W JP 2022039381W WO 2023112485 A1 WO2023112485 A1 WO 2023112485A1
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WIPO (PCT)
Prior art keywords
value
brightness
duty
output
normalized
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PCT/JP2022/039381
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French (fr)
Japanese (ja)
Inventor
雄大 山本
章 黒塚
敬史 濱野
光隆 山口
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パナソニックＩｐマネジメント株式会社
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Publication of WO2023112485A1 publication Critical patent/WO2023112485A1/en

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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
    • 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
    • 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
    • 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
    • G09G3/36—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 using liquid crystals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/66—Transforming electric information into light information
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor

Definitions

  • the present invention relates to an image display device that displays an image modulated by a video signal and a light source control circuit suitable for the image display device.
  • An image display device that projects an image onto an indoor wall or a screen installed indoors is known. Further, in an image display device mounted on a vehicle, an image is projected and displayed on the windshield in front of the driver's seat. For example, illumination light is modulated using a reflective liquid crystal panel and projected onto a windshield or the like.
  • the brightness of the displayed image is changed according to the ambient brightness. For example, the brighter the surroundings, the higher the brightness of the displayed image. This makes the displayed image easier to see.
  • the brightness of the displayed image is controlled by changing the amount of light emitted from the light source.
  • Patent Document 1 describes a configuration for controlling the amount of emitted light from a light source by changing the duty of pulsed light emission for the light source and the output of the light source. Specifically, in the range from zero to a predetermined brightness, the duty of pulse emission is linearly increased to 100% while the output of the light source is kept constant. Further, when this range is exceeded, the output of the light source is linearly increased to the maximum output while the duty of pulse emission is maintained at 100%.
  • an object of the present invention to provide an image display device and its light source control circuit capable of controlling the brightness of a displayed image without giving the user a sense of discomfort.
  • a first aspect of the present invention relates to an image display device.
  • An image display device includes a light source, a display element that modulates light emitted from the light source based on a video signal, an illumination optical system that guides the light emitted from the light source to the display element, and a display and a control unit that controls the duty and output of the pulse light emission of the light source according to the brightness of the image.
  • the control unit changes one of the duty and the output in one direction from a minimum value to a maximum value in accordance with the change in brightness, and changes the other of the duty and the output to the corresponding brightness. is changed to obtain a gamma correction value of
  • one of the duty and the output changes in one direction from the minimum value to the maximum value according to changes in brightness.
  • the other of the duty and the output is changed so as to obtain the corresponding brightness gamma correction value. Therefore, the other of duty and output also changes in one direction from the minimum value to the maximum value according to the change in brightness.
  • neither the duty nor the output has an inflection point. Therefore, it is possible to control the brightness of the display image without giving the user a sense of discomfort.
  • the other of the duty and the output changes so as to obtain the corresponding brightness gamma correction value, so it is possible to change the brightness of the display image to suit human vision. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes.
  • a second aspect of the present invention relates to a light source control circuit for controlling a light source of an image display device.
  • the light source control circuit according to this aspect minimizes one of the duty and the output according to the change in brightness in the control processing for controlling the duty and the output of the pulse light emission of the light source according to the brightness of the display image. value to a maximum value, and the other of the duty and the output is varied to obtain the corresponding gamma correction value of the brightness.
  • the same control as in the first aspect is performed. Therefore, an effect similar to that of the first mode is achieved.
  • an image display device and its light source control circuit capable of controlling the brightness of a displayed image without giving the user a sense of discomfort.
  • FIG. 1 is a plan view showing the configuration of an optical system of an image display device according to an embodiment.
  • FIG. 2 is a block diagram showing the configuration of the circuit section of the image display device according to the embodiment.
  • FIG. 3A is a graph showing the relationship between brightness and duty of pulse emission according to a comparative example.
  • FIG. 3B is a graph showing the relationship between brightness and light source output duty, according to a comparative example.
  • FIG. 4A is a graph showing the relationship between brightness and duty of pulsed light emission according to the embodiment.
  • FIG. 4B is a graph showing the relationship between brightness and light source output duty, according to the embodiment.
  • FIG. 5(a) is a diagram showing the configuration of a duty table according to the embodiment.
  • FIG. 5(b) is a diagram showing the configuration of an output table according to the embodiment.
  • FIG. 6A is a graph showing the relationship between brightness input and output when gamma correction is applied, according to an embodiment.
  • FIG. 6(b) is a diagram showing the relationship between the input value and the output value of brightness in each plot on the graph of FIG. 6(a).
  • FIG. 7A is a graph showing an example of the relationship between the drive current of the light source and the light emission output according to the embodiment.
  • FIG. 7B is a diagram showing the relationship between the normalized input value of brightness and the normalized output value of the light source according to the embodiment.
  • FIG. 8 is a diagram showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission according to the embodiment.
  • FIG. 9A is a graph showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission according to the embodiment.
  • FIG. 9B is a graph showing the relationship between the normalized input value of brightness and the normalized output value of the light source according to the embodiment.
  • FIG. 10 is a flow chart showing a method of generating a duty table and an output table according to the embodiment.
  • FIG. 11 is a flowchart illustrating processing for controlling brightness of a displayed image, according to an embodiment.
  • 12 is a plan view showing the configuration of the optical system of the image display device according to Modification 1.
  • FIG. 13 is a flowchart for controlling the brightness of a display image according to Modification 1.
  • FIG. 14 is a plan view showing the configuration of the optical system of the image display device according to Modification 2.
  • FIG. 15 is a graph schematically showing the relationship between the driving current of the light source and the light emission output when the temperature changes, according to Modification 2.
  • FIG. 16 is a flowchart illustrating a process of selecting a duty table and an output table used for light source control according to Modification 2;
  • FIG. 17 is a flowchart showing a method of generating a duty table and an output table according to Modification 3.
  • FIG. 16 is a flowchart illustrating a process of selecting a duty table and an output table used for light source control according to Modification 2;
  • FIG. 17 is a flowchart showing a method of generating a duty table and an output table according to Modification 3.
  • each figure is labeled with mutually orthogonal X, Y, and Z axes.
  • the Y-axis negative direction is the projection direction of laser light modulated by a video signal
  • the X-axis direction is the vertical direction of the optical system.
  • FIG. 1 is a plan view showing the configuration of the optical system of the image display device 1.
  • FIG. 1 the optical axis of the optical system is indicated by a dashed-dotted line, and the optical paths of laser beams of respective colors are schematically indicated by dotted lines.
  • the image display device 1 includes light sources 11 to 13, an illumination optical system 20, a display element 30, and a projection lens unit 40 as an optical system configuration. Furthermore, the image display device 1 includes an actuator 50 that vibrates the cylindrical lens array 25 in the Y-axis direction.
  • the light sources 11, 12, and 13 emit laser light in a red wavelength band, a green wavelength band, and a blue wavelength band, respectively.
  • Light sources 11, 12, and 13 are, for example, semiconductor lasers.
  • the light sources 11 and 12 emit laser light in the positive Z-axis direction, and the light source 13 emits laser light in the positive Y-axis direction.
  • the output optical axes of the light sources 11, 12, 13 are contained in the same plane parallel to the YZ plane.
  • the light sources 11 , 12 , 13 are arranged such that the polarization direction is S-polarized with respect to the plane of polarization of the polarization beam splitter 28 .
  • the illumination optical system 20 guides the laser light of each color emitted from the light sources 11 , 12 and 13 to the display element 30 .
  • the illumination optical system 20 includes collimator lenses 21a to 21c, dichroic mirrors 22a and 22b, a fly-eye lens 23, a collimator lens 24, a cylindrical lens array 25, a diffusion plate 26, a field lens 27, and a polarizing beam splitter. 28.
  • the collimator lenses 21a-21c converge the laser beams emitted from the light sources 11-13 into substantially parallel beams, respectively.
  • the dichroic mirror 22a transmits the laser light in the red wavelength band that has passed through the collimator lens 21a, and reflects the laser light in the green wavelength band that has passed through the collimator lens 21b.
  • the dichroic mirror 22b transmits laser light in the red and green wavelength bands incident from the dichroic mirror 22a side, and reflects laser light in the blue wavelength band that has passed through the collimator lens 21c.
  • the dichroic mirror 22a is arranged at a position where the emission optical axes of the light sources 11 and 12 intersect, and the dichroic mirror 22b is arranged at a position where the emission optical axes of the light sources 11 and 13 intersect.
  • the optical axes of the light sources 11, 12, 13 are aligned with each other by the dichroic mirrors 22a, 22b. Therefore, the laser beams in the respective wavelength bands of red, green, and blue go through the same optical path in the positive Z-axis direction after passing through the dichroic mirror 22b.
  • the fly-eye lens 23 homogenizes the intensity distribution of the incident laser light.
  • the fly-eye lens 23 is composed of a microlens array in which a large number of microlenses are arranged in a matrix.
  • the laser light incident on each microlens of the fly-eye lens 23 is diffused through the collimator lens 24 so as to spread over the same incident area of the cylindrical lens array 25 . Thereby, the intensity distribution of the laser light of each color is made uniform in the incident area of the cylindrical lens array 25 .
  • the collimator lens 24 collimates the laser light incident from the fly-eye lens 23 and guides it to the cylindrical lens array 25 .
  • a large number of cylindrical lenses 25a and 25b are formed on the incident surface and the exit surface of the cylindrical lens array 25, respectively.
  • a large number of cylindrical lenses 25a are formed on the incident surface of the cylindrical lens array 25 so that the generatrix is parallel to the X-axis.
  • a large number of cylindrical lenses 25b are formed on the output surface of the cylindrical lens array 25 so that the generatrix is parallel to the Y-axis.
  • each lens unit converges the laser light in the Y-axis direction by the cylindrical lens 25a on the entrance surface, and converges the laser light in the X-axis direction by the cylindrical lens 25b on the exit surface. Due to this lens action of each lens part and the lens action of the field lens 27 on the rear side, the laser light transmitted through each lens part is guided to the display element 30 so as to spread over the entire display area of the display element 30 .
  • the diffusion plate 26 diffuses the laser light incident from the cylindrical lens array 25 side at a predetermined diffusion angle. A large number of fine lenses are formed on the entrance surface or the exit surface of the diffuser plate 26 with almost no space therebetween. The diffusing action of the diffusing plate 26 further homogenizes the intensity distribution of the laser light.
  • the polarizing beam splitter 28 reflects the S-polarized components of the laser beams incident from the field lens 27 side and guides them to the display element 30, and transmits and projects the P-polarized components of the laser beams incident from the display element 30 side. It leads to the lens unit 40.
  • the display element 30 is a reflective liquid crystal panel.
  • the display element 30 changes the polarization direction of the laser light incident on the display area for each pixel according to the video signal. As a result, the amount of laser light that passes through the polarization beam splitter 28 changes for each pixel. Thus, the laser light of each color is modulated according to the video signal.
  • the projection lens unit 40 projects the modulated laser light of each color incident from the polarization beam splitter 28 side in the Y-axis negative direction.
  • the projection lens unit 40 includes a plurality of projection lenses 41 for projecting laser light of each color, and a lens barrel 42 that holds the projection lenses 41 .
  • the actuator 50 includes a support portion 51 and a drive portion 52, and drives the drive portion 52 to vibrate the support portion 51 in the Y-axis direction.
  • Drive unit 52 is, for example, an electromagnetic actuator that drives support unit 51 by an electromagnetic force generated between a coil and a magnet.
  • the drive unit 52 may be configured to drive the support unit 51 by another method.
  • the projection lens 41 projects the laser light of each color wavelength band modulated by the display element 30 based on the video signal.
  • the light sources 11, 12, and 13 are driven in a time division manner, and the display element 30 displays an image of that color during the driving period of the light source of each color.
  • a color projection image is displayed on the rear stage side of the projection lens unit 40 .
  • the actuator 50 finely vibrates the cylindrical lens array 25 in the Y-axis direction. This suppresses speckle noise that occurs in the projected image due to interference of laser light.
  • FIG. 2 is a block diagram showing the configuration of the circuit section of the image display device 1 according to the embodiment.
  • the image display device 1 includes a control section 101, light source drive sections 102 to 104, a display element drive section 105, and an actuator drive section 106 as the configuration of the circuit section.
  • a light source control circuit 200 is configured by the control unit 101 and the light source driving units 102 to 104 .
  • the control unit 101 includes an arithmetic processing circuit such as a CPU and a memory, and controls each unit according to a program stored in the memory.
  • the light source driving units 102 to 104 drive the light sources 11 to 13 under the control of the control unit 101, respectively.
  • the display element driving section 105 drives the display element 30 under the control of the control section 101 .
  • Actuator driving section 106 drives actuator 50 under the control of control section 101 .
  • the control unit 101 controls the light source driving units 102 to 104 to drive the light sources 11, 12, and 13 in a time division manner, controls the display element driving unit 105, and controls the driving period of each light source.
  • a modulation pattern for modulating the laser light from the light source is displayed on the display element 30 .
  • the control unit 101 drives the display element 30 so as to generate a modulation pattern corresponding to one frame of an image in each time division period. As a result, the images of each color are integrated to display a color image.
  • control is performed to change the brightness of the display image according to the brightness of the surroundings of the display image.
  • the brightness of the displayed image can be controlled by changing the amount of light emitted from the light sources 11-13.
  • control unit 101 causes the light sources 11 to 13 to emit pulsed light at a predetermined duty, and changes the duty and the output of the light sources 11 to 13 to change the amount of light emitted from the light sources 11 to 13.
  • duty means the ratio of the period of pulsed light emission to one cycle of pulsed light emission
  • output means the intensity of pulsed light emission.
  • the maximum duty of the light emission period of each color with respect to one frame period is 1/3 or about 33%.
  • the time division does not necessarily have to be set evenly for the three colors, for example, the maximum duration of red is set to 50% of one frame period, and the maximum duration of green and blue are each set to one frame period. It may be set to 25%. In this case, the maximum duty of the red emission period is 50%, and the maximum duty of the blue and green emission periods is 25%.
  • the control unit 101 sets the duty and output according to the input brightness for each of the light sources 11 to 13 within the range up to the maximum duty and maximum output, and controls the light sources 11 to 13 with the set duty and output. drive each. Thereby, the brightness of the display image is adjusted to a predetermined brightness.
  • FIG. 3(a) is a graph showing the relationship between the brightness and the duty of pulse emission according to the comparative example.
  • FIG. 3B is a graph showing the relationship between brightness and light source output duty, according to a comparative example.
  • the output of the light source in the comparative example, in the range from zero to the predetermined brightness L0, the output of the light source is maintained at a constant value P0, and the pulse emission duty is It is increased linearly up to a maximum value D_max. Further, when this range is exceeded, the output of the light source is linearly increased to the maximum output PW_max while the duty of pulse emission is maintained at D_max.
  • an inflection point occurs at the position of brightness L0 in both duty and output. Therefore, if the brightness of the display image is changed across the brightness L0, which is the point of inflection, as described above, the user may feel uncomfortable.
  • the duty of pulse light emission and the outputs of the light sources 11 to 13 are controlled so that such an inflection point does not occur.
  • the control unit 101 changes one of the duty and the output in one direction from the minimum value to the maximum value according to the change in brightness, and changes the other of the duty and the output to gamma-correct the corresponding brightness. Vary to obtain a value.
  • FIG. 4(a) is a graph showing the relationship between the brightness and the duty of pulse emission according to the embodiment.
  • FIG. 4B is a graph showing the relationship between brightness and light source output duty, according to the embodiment.
  • the duty increases in a curve from the minimum value D_min to the maximum value D_max as the brightness increases over the entire brightness range.
  • the light source output increases in a curve from the minimum value Pw_min to the maximum value Pw_max as the brightness increases over the entire brightness range.
  • the control unit 101 acquires the duty and output corresponding to the input brightness value from the relationships shown in FIGS. 4(a) and 4(b), and drives the light sources 11 to 13 with the acquired duty and output.
  • the relationship between brightness, duty, and output may be defined for each light source.
  • the control unit 101 acquires the duty and the output corresponding to the input brightness value for each light source from the relationship defined for each light source, and controls each light source.
  • the relationship between brightness, duty, and output may be obtained from information that associates brightness values with duty and output in advance.
  • the control unit 101 holds this information in memory in advance. This information may be prepared for each light source. As shown in FIG. 2, this information can be held in the control section 101 as a duty table 101a and an output table 101b.
  • FIG. 5(a) is a diagram showing the configuration of the duty table 101a.
  • FIG. 5B is a diagram showing the configuration of the output table 101b.
  • the duty table 101a brightness values and duty values are associated with each other.
  • the output table 101b brightness values and light source output values are associated with each other.
  • the brightness is set in 100 steps.
  • a duty table 101a and an output table 101b may be held for each of the light sources 11-13.
  • one of the pulse emission duty and the light source output is changed from its minimum value to its maximum value with the same change tendency as the change tendency from the minimum value to the maximum value of the gamma correction value of brightness. More specifically, one of the pulse emission duty and the light source output is changed from its minimum value to its maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value of brightness. Then, the other of the pulse emission duty and the light source output is changed so as to obtain the corresponding brightness gamma correction value.
  • the light source output is varied from its minimum value to its maximum value with the same variation trend as the brightness gamma correction value from its minimum value to its maximum value, and the duty of the pulse emission is adjusted to the corresponding brightness.
  • Gamma correction is a conventionally well-known correction process that corrects the brightness input value to a value suitable for human perception based on the non-linearity of human perception of brightness.
  • gamma correction is defined by the following formula.
  • Equation (1) X is the input brightness value, and Y is the brightness value after gamma correction (gamma correction value).
  • the gamma value ⁇ depends on the illumination optical system 20 and the display element 30. FIG. Generally, in image display devices, the gamma value ⁇ is set to approximately 1.8 to 2.2.
  • FIG. 6(a) is a graph showing the relationship between brightness input and output when gamma correction is applied.
  • FIG. 6(b) is a diagram showing the relationship between the input value and the output value of brightness in each plot on the graph of FIG. 6(a).
  • FIGS. 6A and 6B show broken line graphs showing the relationship between brightness input and output when the gamma value ⁇ is 1.0, that is, when no gamma correction is performed. Output values are shown.
  • the brightness input value is divided into 100 levels from 1 to 100, and the brightness input value is standardized with 1 as the maximum brightness value. Therefore, the gamma correction value of brightness is also normalized with 1 as the maximum value.
  • the gamma correction value graph (solid line) is curved downward in the range other than both ends, compared to the graph (broken line) without gamma correction. That is, the gamma correction value is smaller than the brightness input value in the range between the minimum value and the maximum value.
  • the outputs of the light sources 11 to 13 for each brightness are calculated so as to have the same changing tendency as the gamma correction value.
  • a method of setting the duty and output for the light source 11 that emits laser light in the red wavelength band is shown below.
  • the duties and outputs of the other light sources 12 and 13 are also set by a similar setting method.
  • FIG. 7(a) is a graph showing an example of the relationship between the driving current of the light source 11 and the light emission output.
  • the light source 11 does not emit light until the drive current reaches the light emission threshold, and when the drive current exceeds the light emission threshold, the output increases as the drive current increases. Therefore, the output and driving current of the light source 11 are set within ranges W1 and W2 in which the light source 11 stably emits light exceeding the light emission threshold.
  • the output range W1 of the light source 11 is set within the range of 80 mW to 800 mW. Thus, the minimum and maximum values of the output of the light source 11 are set.
  • the minimum and maximum values are each normalized with the maximum value being 1.
  • the minimum and maximum output values are 80 mW and 800 mW, respectively, so the normalized minimum and maximum values are 0.1 and 1, respectively.
  • normalized output values of the light sources 11 to 13 for each brightness are calculated so as to have the same changing tendency as the gamma correction value.
  • the normalized output value is changed from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value. That is, the normalized output value of the range between the upper limit and the lower limit of the output of the light source 11 is calculated so as to be linear with the normalized gamma correction value (normalized gamma value).
  • Calculation of the normalized output value can be performed by the following formula.
  • L ⁇ is the normalized gamma correction value for each brightness
  • L ⁇ min and L ⁇ max are the minimum and maximum normalized gamma correction values, respectively.
  • Pw is the normalized output value of each brightness
  • Pwmin and Pwmax are the minimum and maximum normalized output values, respectively.
  • FIG. 7(b) is a diagram showing the relationship between the normalized input value of brightness and the normalized output value of the light source 11.
  • the normalized input value of each brightness is calculated by the above formula (2).
  • a normalized output value of the light source 11 is associated.
  • the normalized value of duty (normalized duty value) associated with each normalized input value is Calculated.
  • FIG. 8 is a diagram showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission.
  • the normalized duty value is calculated by dividing the corresponding normalized gamma correction value by the corresponding normalized output value. That is, by multiplying the normalized output value for each brightness by the normalized duty value, the normalized gamma correction value for that brightness is obtained.
  • FIG. 9(a) is a graph showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission.
  • FIG. 9B is a graph showing the relationship between the normalized input value of brightness and the normalized output value of the light source 11. As shown in FIG.
  • the brightness input value The duty and output values increase as the The tendency of change from the minimum value to the maximum value in the graph of FIG. 9(b) is similar to the tendency of change from the minimum value to the maximum value of the graph of FIG. 6(a). That is, the output of the light source 11 changes from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the normalized gamma correction value.
  • the normalized duty value for each normalized input value of brightness is, as described above, the normalized output value of FIG. 9(a) corresponding to the normalized input value.
  • the normalized gamma correction value shown in FIG. 6A corresponding to the normalized input value is obtained.
  • FIG. 10 is a flow chart showing a method of generating the duty table 101a and the output table 101b when the above setting method is used.
  • step S11 the gamma correction of the above formula (1) is applied to each normalized input value of brightness to calculate the normalized gamma correction value of each brightness.
  • the normalized gamma correction value corresponding to each normalized input value of brightness is acquired.
  • step S12 as described with reference to FIG. 7A, the minimum and maximum values of the output of the light source 11 are set, and the set minimum and maximum values are normalized by the maximum value. be.
  • step S13 the normalized output value in the range between the maximum value (upper limit) and the minimum value (lower limit) of the normalized output is linear with the normalized gamma correction value.
  • the normalized output value corresponding to each normalized input value of brightness is acquired.
  • step S14 the normalized duty value corresponding to each normalized output value is calculated so that the multiplied value with the normalized output value becomes the gamma correction value corresponding to the normalized output value. Thereby, as shown in FIG. 8, the normalized duty value corresponding to each normalized input value of brightness is obtained.
  • each normalized duty value is multiplied by the maximum pulse emission duty value (eg, 33%) to generate a duty table.
  • an output table is generated by multiplying the normalized output value by the maximum value of the light emission output of the light source 11 (800 mW, for example).
  • the duty table 101a and the output table 101b configured as shown in FIGS. 5(a) and 5(b) are generated.
  • FIG. 11 is a flow chart showing processing for controlling the brightness of the display image.
  • the brightness of the displayed image is automatically set according to the ambient brightness, for example.
  • an illuminance sensor is used to detect ambient brightness.
  • the system controller acquires the brightness level corresponding to the detection value of the illuminance sensor from a relational expression or table that defines the relationship between the illuminance and the brightness level, and converts the acquired brightness level to the brightness level shown in FIG. Output to the control unit 101 .
  • the brightness of the displayed image may be set by the user via the input interface. In this case, the system controller outputs a default brightness value to the control unit 101 in FIG. Output to the unit 101 .
  • control unit 101 holds a duty table 101a and an output table 101b for each of the light sources 11-13.
  • control unit 101 stores the duty values and output values corresponding to the processing brightness values input at the start of the operation, for each of the light sources 11 to 13, in the duty table 101a and the output table. 101b, and sets the acquired duty value and output value to each light source (S101).
  • the control unit 101 causes each light source to emit pulse light according to the duty value and output value set in step S101 (S103). Then, the control unit 101 determines whether or not the display operation has ended (S104), and if the display operation has not ended (S104: NO), determines whether or not the brightness setting has been changed. (S105).
  • the control unit 101 If the brightness setting has not been changed (S105: NO), the control unit 101 returns the process to step S102 and performs the same process. On the other hand, if the brightness setting has been changed (S105: YES), the control unit 101 returns the process to step S101. Then, the control unit 101 acquires the duty value and the output value corresponding to the new brightness value from the duty table 101a and the output table 101b for each of the light sources 11 to 13, and stores the acquired duty value and output value in each Set the light source. Thus, the brightness of the displayed image is changed.
  • the control unit 101 repeats similar processing until the display operation is completed (S104: NO). After that, when the display operation ends (S104: YES), the control unit 101 ends the processing of FIG.
  • the control unit 101 changes the outputs of the light sources 11 to 13 in one direction from the minimum value to the maximum value according to the change in brightness, and the duty of pulse emission. is varied so as to obtain the gamma correction value for the corresponding brightness.
  • the duty value for each brightness is set so that the gamma correction value for that brightness can be obtained from the duty value and the output value corresponding to that brightness. .
  • the brightness of the display image can be changed so as to be suitable for human vision. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes.
  • the control unit 101 adjusts the outputs of the light sources 11 to 13 with the same change tendency as the change tendency from the minimum value to the maximum value of the gamma correction value. Vary from its minimum value to its maximum value. More specifically, the control unit 101 changes the outputs of the light sources 11 to 13 from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value. That is, the control unit 101 sets the output values of the light sources 11 to 13 so as to be linear with the gamma correction value of each brightness based on the above equation (2). This allows the outputs of the light sources 11 to 13 to follow changes in the gamma correction value. Therefore, the outputs of the light sources 11 to 13 can be changed so as to suit the human vision for brightness.
  • the multiplied value obtained by multiplying the normalized duty value and the normalized output value for each brightness is the normalized gamma correction value for that brightness.
  • the control unit 101 holds a duty table 101a and an output table 101b in which a brightness value is associated with a duty and an output value. Get the duty and output values for a brightness value. As a result, the control unit 101 can easily acquire the duty and output values without performing calculations for acquiring the duty and output values when the brightness is changed.
  • the image display device 1 includes a plurality of light sources 11 to 13 having different emission wavelengths, and as shown in FIG. Control (S101) for setting duty and output is performed.
  • S101 for setting duty and output is performed.
  • inflection points such as those shown in FIGS. 3A and 3B do not occur in any of the light sources 11-13. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes, and to change the brightness of the display image so as to be suitable for human vision.
  • Modification 1 a photodetector for detecting the amount of light emitted from the light sources 11 to 13 is further arranged, and the amount of light emitted from each light source detected via the photodetector and the amount of light corresponding to the brightness to be set are detected. At least one of the duty and the output is corrected so that the difference in is suppressed.
  • the target brightness may not be obtained due to conditions such as the temperature of the light sources 11-13. Therefore, in Modification 1, the actual emitted light amount of each light source is detected by the photodetector when the duty and output are set as described above and the light sources 11 to 13 emit pulsed light, and the detected actual emitted light amount is detected by the photodetector. At least one of the duty and the output is corrected so that the difference between the amount of light and the amount of light corresponding to the brightness to be set is suppressed.
  • FIG. 12 is a plan view showing the configuration of the optical system of the image display device 1 according to Modification 1.
  • a spectral element 29 and a photodetector 60 are added as compared with FIG.
  • the spectroscopic element 29 transmits most of the light of each color incident from the dichroic mirror 22b side, and reflects only part of the light.
  • a flat glass plate is used as the spectral element 29 .
  • the photodetector 60 receives the light of each color reflected by the spectral element 29 and outputs a signal corresponding to the received light intensity.
  • FIG. 13 is a flowchart for controlling the brightness of the display image according to Modification 1.
  • the flowchart of FIG. 13 has steps S111 to S113 added. Processing in steps other than steps S111 to S113 is the same as the corresponding steps in FIG.
  • the control unit 101 integrates the detection value of the photodetector 60 over the pulse emission period, and acquires the integrated value as the received light amount ( S111).
  • the control unit 101 preliminarily holds, for each of the light sources 11 to 13, a table in which each brightness value is associated with a reference value of the amount of received light (integrated value) for realizing the brightness.
  • the control unit 101 acquires the reference value corresponding to the currently set brightness from the table of the light sources to be controlled, and calculates the difference between the acquired reference value and the integrated value acquired in step S111 (S112). . Then, the control unit 101 corrects the output of the light source to be controlled so that this difference is suppressed (S113).
  • the control unit 101 executes steps S111 to S113 each time light of each color is pulsed. As a result, the emitted light amount of each color converges to the light amount corresponding to the brightness setting value. Therefore, even if the temperature of the light sources 11 to 13 changes, the display image can be displayed with the set brightness.
  • step S113 the outputs of the light sources 11 to 13 are corrected, but instead of or together with this, the pulse emission duty of each light source may be corrected so as to suppress the difference value. .
  • a temperature sensor for detecting the temperature near the light sources 11 to 13 is further arranged, and the duty table and the output table used for setting are changed according to the temperature detected by the temperature sensor. That is, the control unit 101 holds a duty table and an output table for a plurality of temperatures, and uses the duty table and the output table corresponding to the temperature detected by the temperature sensor to determine the brightness value to be set. Get duty and output values.
  • FIG. 14 is a plan view showing the configuration of the optical system of the image display device 1 according to Modification 2.
  • a temperature sensor 70 is added compared to FIG. A temperature sensor 70 is placed close to the light sources 11-13 to detect the temperature in the vicinity of the light sources 11-13. In the configuration of FIG. 14, one temperature sensor 70 detects the temperature near the light sources 11-13. Alternatively, a temperature sensor may be arranged for each of the light sources 11-13 and the temperature of each light source may be detected individually.
  • FIG. 15 is a graph schematically showing the relationship between the driving current of the light source 11 and the light emission output when the temperature changes.
  • FIG. 15 shows respective graphs when the temperature of the light source 11 is t1 to t7.
  • the output range W1 of the light source 11 shown in FIG. 7(a) may be changed according to the temperature. It should be changed according to the temperature.
  • the output range of light source 11 can be set to range W11 when the temperature is in the range of t1 to t3.
  • the power range of the light source can be set to range W12.
  • the normalized output value for each brightness is set from the above equation (2) based on the minimum output value Pw_min1 and the maximum output value Pw_max1. Further, when the temperature is t7, the normalized output value for each brightness is set from the above equation (2) based on the minimum output value Pw_min2 and the maximum output value Pw_max2. Similarly, when the temperatures are at t4, t5, and t6, the minimum output value and maximum output value are adjusted, and the normalized output value for each brightness is set from the above equation (2). Therefore, the normalized duty value of each brightness also changes for each temperature. As a result, the duty table and output table of each light source also differ for each temperature.
  • the duty table and output table of each light source are defined for each temperature. That is, the control unit 101 of FIG. 2 holds a plurality of types of duty tables 101a and output tables 101b with different target temperatures for each of the light sources 11-13.
  • FIG. 16 is a flowchart showing selection processing of the duty table and the output table used for controlling the light sources 11 to 13 according to Modification 2.
  • the control unit 101 acquires the temperature from the temperature sensor 70 (S201), and selects the duty table and the output table corresponding to the acquired temperature as tables to be used for control (S202). .
  • the control unit 101 performs the control shown in FIG. 11 or 12 using the selected duty table and output table.
  • the control unit 101 repeatedly executes the process of step S201 until the operation of the image display device 1 is completed (S203: NO).
  • the tables used for control are changed to the duty table and output table corresponding to the new temperature in step S202.
  • the table used for the control in FIG. 11 or 12 can be switched at any time.
  • the duty table and the output table suitable for the temperature of the light source 11 are used for controlling the light sources 11 to 13, so that the light sources 11 to 13 can be controlled more appropriately and smoothly. Therefore, it is possible to appropriately control the brightness of the display image to a predetermined brightness.
  • the normalized output value is calculated by applying the formula (2) to the normalized gamma correction value, A normalized duty value was calculated based on the output value.
  • the normalized duty value is first calculated so as to be linear with the normalized gamma correction value, and then the normalized output value is calculated based on the normalized gamma correction value and the normalized duty value. may be calculated.
  • the normalized duty value of each brightness can be calculated by the following formula.
  • L ⁇ is the normalized gamma correction value for each brightness
  • L ⁇ min and L ⁇ max are the minimum and maximum normalized gamma correction values, respectively.
  • D is the normalized duty value of each brightness
  • Dmin and Dmax are the minimum and maximum normalized duty values, respectively.
  • the normalized output value is calculated so that the multiplied value by the normalized duty value of each brightness becomes the normalized gamma value of that brightness.
  • the product of the minimum normalized output value and the maximum light source output value 800 mW in the example of FIG. 7A
  • the minimum and maximum normalized duty values are set so as to satisfy this condition.
  • FIG. 17 is a flow chart showing a method of generating the duty table 101a and the output table 101b according to the third modification.
  • steps S12-S14 of the flowchart of FIG. 10 are replaced with steps S21-S23.
  • the processes of steps S11, S15, and S16 in FIG. 17 are the same as the corresponding steps in FIG.
  • step S21 the minimum and maximum values of the pulse emission duty are set, and the set minimum and maximum values are normalized by the maximum value.
  • step S22 the normalized duty value in the range between the maximum value (upper limit) and minimum value (lower limit) of the normalized duty is calculated so as to be linear with the normalized gamma correction value. This calculation is performed by the above formula (3). As a result, a normalized duty value corresponding to each normalized input value of brightness is obtained.
  • step S23 the normalized output value corresponding to each normalized duty value is calculated so that the multiplied value with the normalized duty value becomes the normalized gamma correction value corresponding to the normalized duty value. As a result, a normalized output value corresponding to each normalized input value of brightness is obtained.
  • each normalized duty value is multiplied by the maximum value of the pulse emission duty to generate a duty table.
  • the normalized output value is multiplied by the maximum value of the light emission output of the light source 11 to generate an output table.
  • the duty table 101a and the output table 101b may be generated for each of the light sources 11 to 13, as in the above embodiment. Further, as in the second modification, a duty table 101a and an output table 101b may be generated for each temperature of the light sources 11-13.
  • the output value for each brightness is set so as to be linear with respect to the gamma correction value for each brightness. It may not be linear with respect to the brightness gamma correction value, and may be set by other methods as long as it changes in one direction from the minimum value to the maximum value. For example, each brightness output value may change so as to change linearly from the minimum value to the maximum value.
  • the duty value for each brightness should be set so that the output value for that brightness and the gamma correction value for that brightness are obtained. That is, the normalized duty value for each brightness may be set so that the normalized gamma correction value for that brightness is obtained when multiplied by the normalized output value for that brightness. Similarly, in Modification 3, the duty value of each brightness does not have to be linear with respect to the gamma correction value of each brightness. may be set by the method of
  • the duty value and output value of the brightness to be set are obtained from the duty table 101a and the output table 101b. It may be obtained by calculation.
  • the control unit 101 calculates, for example, the normalized gamma correction value from the brightness value to be set by the above formula (1), and the calculated normalized gamma correction value, the normalized minimum value of the light emission output, and the standard By applying the normalized maximum value to the above equation (2), the normalized output value of the brightness to be set is calculated.
  • the control unit 101 sets the normalized duty value of the brightness to be set so that the multiplied value by the calculated normalized output value becomes the normalized gamma correction value calculated from the above equation (1). calculate.
  • the control unit 101 multiplies the calculated normalized output value and normalized duty value by the maximum value of the output value and the maximum value of the duty value, respectively, to calculate the output value and the duty value for the brightness to be set. .
  • the output value and duty value for the brightness to be set may be calculated directly from the brightness setting value by omitting the intermediate steps in the above calculation process. Also in the third modification, the duty value and the output value of the brightness to be set may be similarly calculated.
  • the control unit 101 holds information (table) in which each brightness shown in FIG. 8 is associated with the normalized output value and the normalized duty value.
  • the control unit 101 obtains the normalized output value and the normalized duty value corresponding to the brightness to be set from this information (table), and outputs the normalized output value and the normalized duty value to the obtained normalized output value and the normalized duty value.
  • the output value and duty value corresponding to the brightness to be set are calculated.
  • the three light sources 11 to 13 that respectively emit laser light in the red, green, and blue wavelength bands are used to display images. type is not limited to this.
  • the image display device 1 may include only one of the light sources 11-13.
  • the control section 101 may hold the duty table 101a and the output table 101b only for this light source.
  • a light source that emits laser light in other color wavelength bands may be used for image display. .
  • the duty of pulse emission and the emission output of laser light sources of wavelength bands of other colors may be controlled in the same manner as described above.
  • the configuration of the optical system of the image display device 1 is not limited to the configurations shown in the first embodiment and the first to third modifications.
  • a display element may be arranged individually for each of the light sources 11 to 13, and the laser light of each color modulated by each display element may be integrated by a plurality of dichroic mirrors.
  • a reflective liquid crystal panel is used as a display element for modulating laser light, but the display element for modulating laser light is limited to this. isn't it.
  • a transmissive liquid crystal panel or a display element of another type such as a digital mirror device (DMD) may be used to modulate the laser light.
  • DMD digital mirror device
  • the configuration of the optical system may be changed in accordance with the change in the method of the display element.
  • the image display device 1 is an image display device that projects a laser beam modulated by a display element. It may be an image display device of the system.
  • the light sources 11 to 13 are not necessarily laser light sources, and may be other types of light sources such as LEDs (Light Emitting Diodes).

Abstract

An image display device (1) comprises: light sources (11-13); a display element (30) that modulates light emitted from the light sources (11-13) on the basis of a video signal; an illumination optical system that guides the light emitted from the light sources (11-13) to the display element (30); and a control unit (101) that controls the duty and the output of the pulse light emission from the light sources (11-13) in accordance with the brightness of a displayed image. The control unit (101) changes one of the duty and the output from the minimum value to the maximum value in one direction in accordance with the change of the brightness, and changes the other of the duty and the output so as to obtain a corresponding brightness gamma correction value.

Description

画像表示装置および光源制御回路Image display device and light source control circuit
　本発明は、映像信号により変調された画像を表示する画像表示装置および当該画像表示装置に好適な光源制御回路に関する。 The present invention relates to an image display device that displays an image modulated by a video signal and a light source control circuit suitable for the image display device.
　室内の壁や、室内に設置されたスクリーンに画像を投射する画像表示装置が知られている。また、車両に搭載された画像表示装置では、運転席前方のフロントガラスに画像が投射されて表示される。たとえば、反射型液晶パネルを用いて照明光が変調されてフロントガラス等に投射される。 An image display device that projects an image onto an indoor wall or a screen installed indoors is known. Further, in an image display device mounted on a vehicle, an image is projected and displayed on the windshield in front of the driver's seat. For example, illumination light is modulated using a reflective liquid crystal panel and projected onto a windshield or the like.
　この種の画像表示装置では、たとえば、周囲の明るさに応じて表示画像の明るさが変更される。たとえば、周囲が明るくなるほど、表示画像の明るさが高められる。これにより、表示画像が見やすくなる。この場合、表示画像の明るさは、光源の出射光量を変化させることにより制御される。 In this type of image display device, for example, the brightness of the displayed image is changed according to the ambient brightness. For example, the brighter the surroundings, the higher the brightness of the displayed image. This makes the displayed image easier to see. In this case, the brightness of the displayed image is controlled by changing the amount of light emitted from the light source.
　以下の特許文献１には、光源に対するパルス発光のデューティと、光源の出力とを変化させることにより、光源の出射光量を制御する構成が記載されている。具体的には、ゼロから所定の明るさまでの範囲は、光源の出力を一定に維持した状態で、パルス発光のデューティが１００％までリニアに高められる。また、この範囲を超えると、パルス発光のデューティを１００％に維持した状態で、光源の出力が最大出力までリニアに高められる。 Patent Document 1 below describes a configuration for controlling the amount of emitted light from a light source by changing the duty of pulsed light emission for the light source and the output of the light source. Specifically, in the range from zero to a predetermined brightness, the duty of pulse emission is linearly increased to 100% while the output of the light source is kept constant. Further, when this range is exceeded, the output of the light source is linearly increased to the maximum output while the duty of pulse emission is maintained at 100%.
特許第６１３８２０３号公報Japanese Patent No. 6138203
　しかしながら、上記方法では、所定の明るさにおいて、デューティおよび光源出力に変曲点が生じる。このため、この方法を上記画像表示装置に用いると、変曲点となる明るさを跨いで表示画像の明るさが変更された場合に、ユーザに違和感を与える惧れがある。 However, with the above method, an inflection point occurs in the duty and light source output at a given brightness. Therefore, if this method is used in the image display device, the user may feel uncomfortable when the brightness of the displayed image is changed across the brightness at the point of inflection.
　かかる課題に鑑み、本発明は、ユーザに違和感を与えることなく表示画像の明るさを制御することが可能な画像表示装置およびその光源制御回路を提供することを目的とする。 In view of such problems, it is an object of the present invention to provide an image display device and its light source control circuit capable of controlling the brightness of a displayed image without giving the user a sense of discomfort.
　本発明の第１の態様は、画像表示装置に関する。本態様に係る画像表示装置は、光源と、前記光源から出射された光を映像信号に基づき変調する表示素子と、前記光源から出射された前記光を前記表示素子に導く照明光学系と、表示画像の明るさに応じて前記光源のパルス発光のデューティおよび出力を制御する制御部と、を備える。ここで、前記制御部は、前記デューティおよび前記出力の一方を前記明るさの変化に応じて最小値から最大値まで一方向に変化させ、前記デューティおよび前記出力の他方を、対応する前記明るさのガンマ補正値が得られるように変化させる。 A first aspect of the present invention relates to an image display device. An image display device according to this aspect includes a light source, a display element that modulates light emitted from the light source based on a video signal, an illumination optical system that guides the light emitted from the light source to the display element, and a display and a control unit that controls the duty and output of the pulse light emission of the light source according to the brightness of the image. Here, the control unit changes one of the duty and the output in one direction from a minimum value to a maximum value in accordance with the change in brightness, and changes the other of the duty and the output to the corresponding brightness. is changed to obtain a gamma correction value of
　本態様に係る画像表示装置によれば、デューティおよび出力の一方が明るさの変化に応じて最小値から最大値まで一方向に変化する。また、デューティおよび出力の他方は、対応する明るさのガンマ補正値が得られるように変化する。このため、デューティおよび出力の他方も、明るさの変化に応じて最小値から最大値まで一方向に変化する。これにより、デューティおよび出力の何れにも変曲点が生じることがない。よって、ユーザに違和感を与えることなく表示画像の明るさを制御できる。 According to the image display device according to this aspect, one of the duty and the output changes in one direction from the minimum value to the maximum value according to changes in brightness. Also, the other of the duty and the output is changed so as to obtain the corresponding brightness gamma correction value. Therefore, the other of duty and output also changes in one direction from the minimum value to the maximum value according to the change in brightness. As a result, neither the duty nor the output has an inflection point. Therefore, it is possible to control the brightness of the display image without giving the user a sense of discomfort.
　また、デューティおよび出力の他方は、対応する明るさのガンマ補正値が得られるように変化するため、人の視覚に適するように表示画像の明るさを変化させることができる。よって、表示画像の明るさが変化した場合のユーザの違和感を効果的に抑制できる。 In addition, the other of the duty and the output changes so as to obtain the corresponding brightness gamma correction value, so it is possible to change the brightness of the display image to suit human vision. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes.
　本発明の第２の態様は、画像表示装置の光源を制御する光源制御回路に関する。本態様に係る光源制御回路は、表示画像の明るさに応じて前記光源のパルス発光のデューティおよび出力を制御する制御処理において、前記デューティおよび前記出力の一方を前記明るさの変化に応じて最小値から最大値まで一方向に変化させ、前記デューティおよび前記出力の他方を、対応する前記明るさのガンマ補正値が得られるように変化させる。 A second aspect of the present invention relates to a light source control circuit for controlling a light source of an image display device. The light source control circuit according to this aspect minimizes one of the duty and the output according to the change in brightness in the control processing for controlling the duty and the output of the pulse light emission of the light source according to the brightness of the display image. value to a maximum value, and the other of the duty and the output is varied to obtain the corresponding gamma correction value of the brightness.
　本態様に係る光源制御回路によれば、上記第１の態様と同様の制御が行われる。よって、上記第１の態様と同様の効果が奏される。 According to the light source control circuit according to this aspect, the same control as in the first aspect is performed. Therefore, an effect similar to that of the first mode is achieved.
　以上のとおり、本発明によれば、ユーザに違和感を与えることなく表示画像の明るさを制御することが可能な画像表示装置およびその光源制御回路を提供できる。 As described above, according to the present invention, it is possible to provide an image display device and its light source control circuit capable of controlling the brightness of a displayed image without giving the user a sense of discomfort.
　本発明の効果ないし意義は、以下に示す実施形態の説明により更に明らかとなろう。ただし、以下に示す実施形態は、あくまでも、本発明を実施化する際の一つの例示であって、本発明は、以下の実施形態に記載されたものに何ら制限されるものではない。 The effects and significance of the present invention will become clearer from the description of the embodiments shown below. However, the embodiment shown below is merely one example of the implementation of the present invention, and the present invention is not limited to the embodiments described below.
図１は、実施形態に係る、画像表示装置の光学系の構成を示す平面図である。FIG. 1 is a plan view showing the configuration of an optical system of an image display device according to an embodiment. 図２は、実施形態に係る、画像表示装置の回路部の構成を示すブロック図である。FIG. 2 is a block diagram showing the configuration of the circuit section of the image display device according to the embodiment. 図３（ａ）比較例に係る、明るさとパルス発光のデューティとの関係を示すグラフである。図３（ｂ）は、比較例に係る、明るさと光源出力のデューティとの関係を示すグラフである。FIG. 3A is a graph showing the relationship between brightness and duty of pulse emission according to a comparative example. FIG. 3B is a graph showing the relationship between brightness and light source output duty, according to a comparative example. 図４（ａ）は、実施形態に係る、明るさとパルス発光のデューティとの関係を示すグラフである。図４（ｂ）は、実施形態に係る、明るさと光源出力のデューティとの関係を示すグラフである。FIG. 4A is a graph showing the relationship between brightness and duty of pulsed light emission according to the embodiment. FIG. 4B is a graph showing the relationship between brightness and light source output duty, according to the embodiment. 図５（ａ）は、実施形態に係る、デューティテーブルの構成を示す図である。図５（ｂ）は、実施形態に係る、出力テーブルの構成を示す図である。FIG. 5(a) is a diagram showing the configuration of a duty table according to the embodiment. FIG. 5(b) is a diagram showing the configuration of an output table according to the embodiment. 図６（ａ）は、実施形態に係る、ガンマ補正が適用された場合の明るさの入力と出力との関係を示すグラフである。図６（ｂ）は、図６（ａ）のグラフ上の各プロットにおける明るさの入力値と出力値の関係を示す図である。FIG. 6A is a graph showing the relationship between brightness input and output when gamma correction is applied, according to an embodiment. FIG. 6(b) is a diagram showing the relationship between the input value and the output value of brightness in each plot on the graph of FIG. 6(a). 図７（ａ）は、実施形態に係る、光源の駆動電流と発光出力との関係の一例を示すグラフである。図７（ｂ）は、実施形態に係る、明るさの規格化入力値と光源の規格化出力値との関係を示す図である。FIG. 7A is a graph showing an example of the relationship between the drive current of the light source and the light emission output according to the embodiment. FIG. 7B is a diagram showing the relationship between the normalized input value of brightness and the normalized output value of the light source according to the embodiment. 図８は、実施形態に係る、明るさの規格化入力値とパルス発光の規格化デューティ値との関係を示す図である。FIG. 8 is a diagram showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission according to the embodiment. 図９（ａ）は、実施形態に係る、明るさの規格化入力値とパルス発光の規格化デューティ値との関係を示すグラフである。図９（ｂ）は、実施形態に係る、明るさの規格化入力値と光源の規格化出力値との関係を示すグラフである。FIG. 9A is a graph showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission according to the embodiment. FIG. 9B is a graph showing the relationship between the normalized input value of brightness and the normalized output value of the light source according to the embodiment. 図１０は、実施形態に係る、デューティテーブルおよび出力テーブルの生成方法を示すフローチャートである。FIG. 10 is a flow chart showing a method of generating a duty table and an output table according to the embodiment. 図１１は、実施形態に係る、表示画像の明るさを制御するための処理を示すフローチャートである。FIG. 11 is a flowchart illustrating processing for controlling brightness of a displayed image, according to an embodiment. 図１２は、変更例１に係る、画像表示装置の光学系の構成を示す平面図である。12 is a plan view showing the configuration of the optical system of the image display device according to Modification 1. FIG. 図１３は、変更例１に係る、表示画像の明るさを制御するためのフローチャートである。13 is a flowchart for controlling the brightness of a display image according to Modification 1. FIG. 図１４は、変更例２に係る、画像表示装置の光学系の構成を示す平面図である。14 is a plan view showing the configuration of the optical system of the image display device according to Modification 2. FIG. 図１５は、変更例２に係る、温度が変化した場合の光源の駆動電流と発光出力との関係を模式的に示すグラフである。FIG. 15 is a graph schematically showing the relationship between the driving current of the light source and the light emission output when the temperature changes, according to Modification 2. FIG. 図１６は、変更例２に係る、光源の制御に用いるデューティテーブルおよび出力テーブルの選択処理を示すフローチャートである。FIG. 16 is a flowchart illustrating a process of selecting a duty table and an output table used for light source control according to Modification 2; 図１７は、変更例３に係る、デューティテーブルおよび出力テーブルの生成方法を示すフローチャートである。FIG. 17 is a flowchart showing a method of generating a duty table and an output table according to Modification 3. FIG.
　ただし、図面はもっぱら説明のためのものであって、この発明の範囲を限定するものではない。 However, the drawings are for illustration only and do not limit the scope of the present invention.
　以下、本発明の実施形態について、図面を参照して説明する。便宜上、各図には、互いに直交するＸ、Ｙ、Ｚ軸が付記されている。Ｙ軸負方向は、映像信号により変調されたレーザ光の投射方向であり、Ｘ軸方向は、光学系の上下方向である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each figure is labeled with mutually orthogonal X, Y, and Z axes. The Y-axis negative direction is the projection direction of laser light modulated by a video signal, and the X-axis direction is the vertical direction of the optical system.
　図１は、画像表示装置１の光学系の構成を示す平面図である。図１には、光学系の光軸が一点鎖線で示され、各色のレーザ光の光路が点線で模式的に示されている。 FIG. 1 is a plan view showing the configuration of the optical system of the image display device 1. FIG. In FIG. 1, the optical axis of the optical system is indicated by a dashed-dotted line, and the optical paths of laser beams of respective colors are schematically indicated by dotted lines.
　画像表示装置１は、光学系の構成として、光源１１～１３と、照明光学系２０と、表示素子３０と、投射レンズユニット４０とを備える。さらに、画像表示装置１は、シリンドリカルレンズアレイ２５をＹ軸方向に振動させるアクチュエータ５０を備える。 The image display device 1 includes light sources 11 to 13, an illumination optical system 20, a display element 30, and a projection lens unit 40 as an optical system configuration. Furthermore, the image display device 1 includes an actuator 50 that vibrates the cylindrical lens array 25 in the Y-axis direction.
　光源１１、１２、１３は、それぞれ、赤の波長帯、緑の波長帯および青の波長帯のレーザ光を出射する。光源１１、１２、１３は、たとえば、半導体レーザである。光源１１、１２は、Ｚ軸正方向にレーザ光を出射し、光源１３は、Ｙ軸正方向にレーザ光を出射する。光源１１、１２、１３の出射光軸は、Ｙ－Ｚ平面に平行な同一平面に含まれる。光源１１、１２、１３は、偏光方向が偏光ビームスプリッタ２８の偏光面に対してＳ偏光となるように配置される。 The light sources 11, 12, and 13 emit laser light in a red wavelength band, a green wavelength band, and a blue wavelength band, respectively. Light sources 11, 12, and 13 are, for example, semiconductor lasers. The light sources 11 and 12 emit laser light in the positive Z-axis direction, and the light source 13 emits laser light in the positive Y-axis direction. The output optical axes of the light sources 11, 12, 13 are contained in the same plane parallel to the YZ plane. The light sources 11 , 12 , 13 are arranged such that the polarization direction is S-polarized with respect to the plane of polarization of the polarization beam splitter 28 .
　照明光学系２０は、光源１１、１２、１３から出射された各色のレーザ光を表示素子３０に導く。照明光学系２０は、コリメータレンズ２１ａ～２１ｃと、ダイクロイックミラー２２ａ、２２ｂと、フライアイレンズ２３と、コリメータレンズ２４と、シリンドリカルレンズアレイ２５と、拡散板２６と、フィールドレンズ２７と、偏光ビームスプリッタ２８とを備える。 The illumination optical system 20 guides the laser light of each color emitted from the light sources 11 , 12 and 13 to the display element 30 . The illumination optical system 20 includes collimator lenses 21a to 21c, dichroic mirrors 22a and 22b, a fly-eye lens 23, a collimator lens 24, a cylindrical lens array 25, a diffusion plate 26, a field lens 27, and a polarizing beam splitter. 28.
　コリメータレンズ２１ａ～２１ｃは、光源１１～１３から出射されたレーザ光を、それぞれ、略平行光に収束させる。ダイクロイックミラー２２ａは、コリメータレンズ２１ａを透過した赤の波長帯のレーザ光を透過させ、コリメータレンズ２１ｂを透過した緑の波長帯のレーザ光を反射させる。ダイクロイックミラー２２ｂは、ダイクロイックミラー２２ａ側から入射する赤および緑の波長帯のレーザ光を透過させ、コリメータレンズ２１ｃを透過した青の波長帯のレーザ光を反射させる。 The collimator lenses 21a-21c converge the laser beams emitted from the light sources 11-13 into substantially parallel beams, respectively. The dichroic mirror 22a transmits the laser light in the red wavelength band that has passed through the collimator lens 21a, and reflects the laser light in the green wavelength band that has passed through the collimator lens 21b. The dichroic mirror 22b transmits laser light in the red and green wavelength bands incident from the dichroic mirror 22a side, and reflects laser light in the blue wavelength band that has passed through the collimator lens 21c.
　ダイクロイックミラー２２ａは、光源１１、１２の出射光軸が交差する位置に配置され、ダイクロイックミラー２２ｂは、光源１１、１３の出射光軸が交差する位置に配置される。ダイクロイックミラー２２ａ、２２ｂによって、光源１１、１２、１３の光軸が互いに整合される。したがって、赤、緑および青の各波長帯のレーザ光は、ダイクロイックミラー２２ｂを経由した後、同一の光路をＺ軸正方向に進む。 The dichroic mirror 22a is arranged at a position where the emission optical axes of the light sources 11 and 12 intersect, and the dichroic mirror 22b is arranged at a position where the emission optical axes of the light sources 11 and 13 intersect. The optical axes of the light sources 11, 12, 13 are aligned with each other by the dichroic mirrors 22a, 22b. Therefore, the laser beams in the respective wavelength bands of red, green, and blue go through the same optical path in the positive Z-axis direction after passing through the dichroic mirror 22b.
　フライアイレンズ２３は、入射するレーザ光の強度分布を均一化する。フライアイレンズ２３は、多数のマイクロレンズがマトリクス状に配置されたマイクロレンズアレイによって構成される。フライアイレンズ２３の各マイクロレンズに入射したレーザ光は、コリメータレンズ２４を介して、シリンドリカルレンズアレイ２５の同一の入射領域全体に広がるように拡散される。これにより、シリンドリカルレンズアレイ２５の入射領域において、各色のレーザ光の強度分布が均一化される。 The fly-eye lens 23 homogenizes the intensity distribution of the incident laser light. The fly-eye lens 23 is composed of a microlens array in which a large number of microlenses are arranged in a matrix. The laser light incident on each microlens of the fly-eye lens 23 is diffused through the collimator lens 24 so as to spread over the same incident area of the cylindrical lens array 25 . Thereby, the intensity distribution of the laser light of each color is made uniform in the incident area of the cylindrical lens array 25 .
　コリメータレンズ２４は、フライアイレンズ２３から入射するレーザ光を平行光化して、シリンドリカルレンズアレイ２５に導く。 The collimator lens 24 collimates the laser light incident from the fly-eye lens 23 and guides it to the cylindrical lens array 25 .
　シリンドリカルレンズアレイ２５の入射面および出射面には、それぞれ、多数のシリンドリカルレンズ２５ａ、２５ｂが形成されている。シリンドリカルレンズアレイ２５の入射面には、母線がＸ軸に平行となるように、多数のシリンドリカルレンズ２５ａが形成されている。シリンドリカルレンズアレイ２５の出射面には、母線がＹ軸に平行となるように、多数のシリンドリカルレンズ２５ｂが形成されている。 A large number of cylindrical lenses 25a and 25b are formed on the incident surface and the exit surface of the cylindrical lens array 25, respectively. A large number of cylindrical lenses 25a are formed on the incident surface of the cylindrical lens array 25 so that the generatrix is parallel to the X-axis. A large number of cylindrical lenses 25b are formed on the output surface of the cylindrical lens array 25 so that the generatrix is parallel to the Y-axis.
　シリンドリカルレンズアレイ２５をＺ軸方向に見たとき、入射面のシリンドリカルレンズ２５ａと出射面のシリンドリカルレンズ２５ｂとが交差する領域に、矩形のレンズ部が形成される。各レンズ部は、入射面のシリンドリカルレンズ２５ａによってＹ軸方向にレーザ光を収束させ、出射面のシリンドリカルレンズ２５ｂによってＸ軸方向にレーザ光を収束させる。各レンズ部のこのレンズ作用と、後段側のフィールドレンズ２７によるレンズ作用とによって、各レンズ部を透過したレーザ光は、表示素子３０の表示領域全体に広がるように、表示素子３０に導かれる。 When the cylindrical lens array 25 is viewed in the Z-axis direction, a rectangular lens portion is formed in an area where the cylindrical lens 25a on the entrance surface and the cylindrical lens 25b on the exit surface intersect. Each lens unit converges the laser light in the Y-axis direction by the cylindrical lens 25a on the entrance surface, and converges the laser light in the X-axis direction by the cylindrical lens 25b on the exit surface. Due to this lens action of each lens part and the lens action of the field lens 27 on the rear side, the laser light transmitted through each lens part is guided to the display element 30 so as to spread over the entire display area of the display element 30 .
　拡散板２６は、シリンドリカルレンズアレイ２５側から入射したレーザ光を所定の拡散角で拡散させる。拡散板２６の入射面または出射面には、多数の微細なレンズが略隙間なく形成されている。拡散板２６の拡散作用によって、レーザ光の強度分布がさらに均一化される。 The diffusion plate 26 diffuses the laser light incident from the cylindrical lens array 25 side at a predetermined diffusion angle. A large number of fine lenses are formed on the entrance surface or the exit surface of the diffuser plate 26 with almost no space therebetween. The diffusing action of the diffusing plate 26 further homogenizes the intensity distribution of the laser light.
　偏光ビームスプリッタ２８は、フィールドレンズ２７側からそれぞれ入射したレーザ光のＳ偏光成分を反射して表示素子３０へと導き、表示素子３０側からそれぞれ入射したレーザ光のＰ偏光成分を透過して投射レンズユニット４０へと導く。 The polarizing beam splitter 28 reflects the S-polarized components of the laser beams incident from the field lens 27 side and guides them to the display element 30, and transmits and projects the P-polarized components of the laser beams incident from the display element 30 side. It leads to the lens unit 40.
　表示素子３０は、反射型の液晶パネルである。表示素子３０は、表示領域に入射したレーザ光の偏光方向を、映像信号に応じて、画素ごとに変化させる。これにより、偏光ビームスプリッタ２８を透過するレーザ光の光量が画素ごとに変化する。こうして、各色のレーザ光が、映像信号に応じて変調される。 The display element 30 is a reflective liquid crystal panel. The display element 30 changes the polarization direction of the laser light incident on the display area for each pixel according to the video signal. As a result, the amount of laser light that passes through the polarization beam splitter 28 changes for each pixel. Thus, the laser light of each color is modulated according to the video signal.
　投射レンズユニット４０は、偏光ビームスプリッタ２８側から入射する、変調された各色のレーザ光をＹ軸負方向に投射する。投射レンズユニット４０は、各色のレーザ光を投射するための複数の投射レンズ４１と、これら投射レンズ４１を保持する鏡筒４２とを備える。 The projection lens unit 40 projects the modulated laser light of each color incident from the polarization beam splitter 28 side in the Y-axis negative direction. The projection lens unit 40 includes a plurality of projection lenses 41 for projecting laser light of each color, and a lens barrel 42 that holds the projection lenses 41 .
　アクチュエータ５０は、支持部５１と、駆動部５２とを備え、駆動部５２を駆動することにより支持部５１をＹ軸方向に振動させる。駆動部５２は、たとえば、コイルと磁石との間に生じる電磁力により支持部５１を駆動する電磁アクチュエータである。駆動部５２が、他の方式により支持部５１を駆動する構成であってもよい。 The actuator 50 includes a support portion 51 and a drive portion 52, and drives the drive portion 52 to vibrate the support portion 51 in the Y-axis direction. Drive unit 52 is, for example, an electromagnetic actuator that drives support unit 51 by an electromagnetic force generated between a coil and a magnet. The drive unit 52 may be configured to drive the support unit 51 by another method.
　図１の光学系では、映像信号に基づいて表示素子３０により変調された各色の波長帯のレーザ光が、投射レンズ４１により投射される。光源１１、１２、１３は、時分割で駆動され、表示素子３０には、各色の光源の駆動期間に、その色の画像が表示される。これにより、投射レンズユニット４０の後段側に、カラーの投射画像が表示される。このとき、アクチュエータ５０によってシリンドリカルレンズアレイ２５がＹ軸方向に微細振動される。これにより、レーザ光の干渉によって投射画像に生じるスペックルノイズが抑制される。 In the optical system of FIG. 1, the projection lens 41 projects the laser light of each color wavelength band modulated by the display element 30 based on the video signal. The light sources 11, 12, and 13 are driven in a time division manner, and the display element 30 displays an image of that color during the driving period of the light source of each color. As a result, a color projection image is displayed on the rear stage side of the projection lens unit 40 . At this time, the actuator 50 finely vibrates the cylindrical lens array 25 in the Y-axis direction. This suppresses speckle noise that occurs in the projected image due to interference of laser light.
　図２は、実施形態に係る、画像表示装置１の回路部の構成を示すブロック図である。 FIG. 2 is a block diagram showing the configuration of the circuit section of the image display device 1 according to the embodiment.
　画像表示装置１は、回路部の構成として、制御部１０１と、光源駆動部１０２～１０４と、表示素子駆動部１０５と、アクチュエータ駆動部１０６と、を備える。制御部１０１と光源駆動部１０２～１０４によって、光源制御回路２００が構成される。 The image display device 1 includes a control section 101, light source drive sections 102 to 104, a display element drive section 105, and an actuator drive section 106 as the configuration of the circuit section. A light source control circuit 200 is configured by the control unit 101 and the light source driving units 102 to 104 .
　制御部１０１は、ＣＰＵ等の演算処理回路とメモリとを備え、メモリに記憶されたプログラムに従って各部を制御する。光源駆動部１０２～１０４は、それぞれ、制御部１０１からの制御により、光源１１～１３を駆動する。表示素子駆動部１０５は、制御部１０１からの制御により、表示素子３０を駆動する。アクチュエータ駆動部１０６は、制御部１０１からの制御により、アクチュエータ５０を駆動する。 The control unit 101 includes an arithmetic processing circuit such as a CPU and a memory, and controls each unit according to a program stored in the memory. The light source driving units 102 to 104 drive the light sources 11 to 13 under the control of the control unit 101, respectively. The display element driving section 105 drives the display element 30 under the control of the control section 101 . Actuator driving section 106 drives actuator 50 under the control of control section 101 .
　画像表示時において、制御部１０１は、光源駆動部１０２～１０４を制御して光源１１、１２、１３を時分割で駆動し、表示素子駆動部１０５を制御して、各光源の駆動期間に、その光源からのレーザ光を変調する変調パターンを表示素子３０に表示させる。制御部１０１は、表示対象の映像信号に基づき、各時分割期間に１フレーム分の画像に応じた変調パターンが生じるよう、表示素子３０を駆動する。これにより、各色の画像が統合されて、カラーの画像が表示される。 During image display, the control unit 101 controls the light source driving units 102 to 104 to drive the light sources 11, 12, and 13 in a time division manner, controls the display element driving unit 105, and controls the driving period of each light source. A modulation pattern for modulating the laser light from the light source is displayed on the display element 30 . Based on the video signal to be displayed, the control unit 101 drives the display element 30 so as to generate a modulation pattern corresponding to one frame of an image in each time division period. As a result, the images of each color are integrated to display a color image.
　ところで、上記構成の画像表示装置１では、表示画像の周囲の明るさに応じて、表示画像の明るさを変化させる制御が行われる。たとえば、表示画像の周囲が明るくなるほど、表示画像の明るさが高められる。これにより、表示画像が見やすくなる。表示画像の明るさは、光源１１～１３の出射光量を変化させることにより、制御され得る。 By the way, in the image display device 1 configured as described above, control is performed to change the brightness of the display image according to the brightness of the surroundings of the display image. For example, the brighter the surroundings of the displayed image, the higher the brightness of the displayed image. This makes the displayed image easier to see. The brightness of the displayed image can be controlled by changing the amount of light emitted from the light sources 11-13.
　この場合、制御部１０１は、光源１１～１３を所定のデューティでパルス発光させつつ、このデューティと光源１１～１３の出力とを変化させることで、光源１１～１３の出射光量を変化させ得る。 In this case, the control unit 101 causes the light sources 11 to 13 to emit pulsed light at a predetermined duty, and changes the duty and the output of the light sources 11 to 13 to change the amount of light emitted from the light sources 11 to 13.
　ここで、「デューティ」とは、パルス発光の１周期に対するパルス発光の期間の比率を意味し、「出力」とは、パルス発光の強度を意味する。たとえば、本実施形態のように光源１１～１３の発光が時分割で行われる場合、フレームごとの各色の発光が均等な時分割で行われると、１フレーム期間に対する各色の発光期間の最大のデューティは、１／３すなわち約３３％となる。ただし、時分割は必ずしも３つの色に対して均等に設定されなくてもよく、たとえば、赤の最大期間が１フレーム期間の５０％に設定され、緑と青の最大期間がそれぞれ１フレーム期間の２５％に設定されてもよい。この場合、赤の発光期間の最大デューティは５０％であり、青と緑の発光期間の最大デューティは、２５％である。 Here, "duty" means the ratio of the period of pulsed light emission to one cycle of pulsed light emission, and "output" means the intensity of pulsed light emission. For example, when the light sources 11 to 13 emit light in a time-division manner as in the present embodiment, and the light emission of each color in each frame is performed in an even time-division manner, the maximum duty of the light emission period of each color with respect to one frame period is is 1/3 or about 33%. However, the time division does not necessarily have to be set evenly for the three colors, for example, the maximum duration of red is set to 50% of one frame period, and the maximum duration of green and blue are each set to one frame period. It may be set to 25%. In this case, the maximum duty of the red emission period is 50%, and the maximum duty of the blue and green emission periods is 25%.
　制御部１０１は、入力された明るさに応じたデューティおよび出力を、最大デューティおよび最大出力までの範囲において、光源１１～１３ごとにそれぞれ設定し、設定したデューティおよび出力で、光源１１～１３をそれぞれ駆動する。これにより、表示画像の明るさが所定の明るさに調節される。 The control unit 101 sets the duty and output according to the input brightness for each of the light sources 11 to 13 within the range up to the maximum duty and maximum output, and controls the light sources 11 to 13 with the set duty and output. drive each. Thereby, the brightness of the display image is adjusted to a predetermined brightness.
　しかしながら、このような制御において、明るさとデューティおよび出力との関係に変曲点があると、変曲点となる明るさを跨いで表示画像の明るさが変更された場合に、ユーザに違和感を与える惧れがある。 However, in such control, if there is an inflection point in the relationship between brightness, duty, and output, the user may feel uncomfortable when the brightness of the display image is changed across the brightness at the inflection point. There is a fear of giving
　図３（ａ）は、比較例に係る、明るさとパルス発光のデューティとの関係を示すグラフである。図３（ｂ）は、比較例に係る、明るさと光源出力のデューティとの関係を示すグラフである。 FIG. 3(a) is a graph showing the relationship between the brightness and the duty of pulse emission according to the comparative example. FIG. 3B is a graph showing the relationship between brightness and light source output duty, according to a comparative example.
　図３（ａ）および図３（ｂ）に示すように、比較例では、ゼロから所定の明るさＬ０までの範囲は、光源の出力を一定値Ｐ０に維持した状態で、パルス発光のデューティが最大値Ｄ＿ｍａｘまでリニアに高められる。また、この範囲を超えると、パルス発光のデューティをＤ＿ｍａｘに維持した状態で、光源の出力が最大出力ＰＷ＿ｍａｘまでリニアに高められる。 As shown in FIGS. 3(a) and 3(b), in the comparative example, in the range from zero to the predetermined brightness L0, the output of the light source is maintained at a constant value P0, and the pulse emission duty is It is increased linearly up to a maximum value D_max. Further, when this range is exceeded, the output of the light source is linearly increased to the maximum output PW_max while the duty of pulse emission is maintained at D_max.
　比較例の制御では、デューティおよび出力の両方において、明るさＬ０の位置に変曲点が生じる。このため、上記のように、変曲点となる明るさＬ０を跨いで表示画像の明るさが変更されると、ユーザに違和感を与える惧れがある。 In the control of the comparative example, an inflection point occurs at the position of brightness L0 in both duty and output. Therefore, if the brightness of the display image is changed across the brightness L0, which is the point of inflection, as described above, the user may feel uncomfortable.
　そこで、本実施形態では、このような変曲点が生じないように、パルス発光のデューティと光源１１～１３の出力とが制御される。具体的には、制御部１０１は、デューティおよび出力の一方を、明るさの変化に応じて最小値から最大値まで一方向に変化させ、デューティおよび出力の他方を、対応する明るさのガンマ補正値が得られるように変化させる。 Therefore, in the present embodiment, the duty of pulse light emission and the outputs of the light sources 11 to 13 are controlled so that such an inflection point does not occur. Specifically, the control unit 101 changes one of the duty and the output in one direction from the minimum value to the maximum value according to the change in brightness, and changes the other of the duty and the output to gamma-correct the corresponding brightness. Vary to obtain a value.
　図４（ａ）は、実施形態に係る、明るさとパルス発光のデューティとの関係を示すグラフである。図４（ｂ）は、実施形態に係る、明るさと光源出力のデューティとの関係を示すグラフである。 FIG. 4(a) is a graph showing the relationship between the brightness and the duty of pulse emission according to the embodiment. FIG. 4B is a graph showing the relationship between brightness and light source output duty, according to the embodiment.
　図４（ａ）に示すように、実施形態では、明るさの全範囲において、明るさの増加に伴いデューティが、最小値Ｄ＿ｍｉｎから最大値Ｄ＿ｍａｘまで曲線状に増加する。また、図４（ｂ）に示すように、実施形態では、明るさの全範囲において、明るさの増加に伴い光源出力が、最小値Ｐｗ＿ｍｉｎから最大値Ｐｗ＿ｍａｘまで曲線状に増加する。 As shown in FIG. 4(a), in the embodiment, the duty increases in a curve from the minimum value D_min to the maximum value D_max as the brightness increases over the entire brightness range. Further, as shown in FIG. 4B, in the embodiment, the light source output increases in a curve from the minimum value Pw_min to the maximum value Pw_max as the brightness increases over the entire brightness range.
　制御部１０１は、入力された明るさの値に対応するデューティおよび出力を、図４（ａ）、（ｂ）の関係から取得し、取得したデューティおよび出力で、光源１１～１３を駆動させる。明るさとデューティおよび出力との関係は、光源ごとに規定されてよい。この場合、制御部１０１は、各々の光源について規定された関係から、光源ごとに、入力された明るさの値に対応するデューティおよび出力を取得して、各光源を制御する。 The control unit 101 acquires the duty and output corresponding to the input brightness value from the relationships shown in FIGS. 4(a) and 4(b), and drives the light sources 11 to 13 with the acquired duty and output. The relationship between brightness, duty, and output may be defined for each light source. In this case, the control unit 101 acquires the duty and the output corresponding to the input brightness value for each light source from the relationship defined for each light source, and controls each light source.
　明るさとデューティおよび出力との関係は、明るさの値とデューティおよび出力とを予め対応付けた情報から取得されてよい。この場合、制御部１０１は、予めこの情報をメモリに保持しておく。この情報は、光源ごとに準備されてよい。図２に示すように、この情報は、デューティテーブル１０１ａおよび出力テーブル１０１ｂとして、制御部１０１に保持され得る。 The relationship between brightness, duty, and output may be obtained from information that associates brightness values with duty and output in advance. In this case, the control unit 101 holds this information in memory in advance. This information may be prepared for each light source. As shown in FIG. 2, this information can be held in the control section 101 as a duty table 101a and an output table 101b.
　図５（ａ）は、デューティテーブル１０１ａの構成を示す図である。図５（ｂ）は、出力テーブル１０１ｂの構成を示す図である。 FIG. 5(a) is a diagram showing the configuration of the duty table 101a. FIG. 5B is a diagram showing the configuration of the output table 101b.
　図５（ａ）に示すように、デューティテーブル１０１ａには、明るさの値とデューティの値とが互いに対応付けられている。図５（ｂ）に示すように、出力テーブル１０１ｂには、明るさの値と光源の出力の値とが互いに対応付けられている。ここでは、明るさが、１００段階に設定されている。デューティテーブル１０１ａおよび出力テーブル１０１ｂは、光源１１～１３ごとに保持されてよい。 As shown in FIG. 5(a), in the duty table 101a, brightness values and duty values are associated with each other. As shown in FIG. 5B, in the output table 101b, brightness values and light source output values are associated with each other. Here, the brightness is set in 100 steps. A duty table 101a and an output table 101b may be held for each of the light sources 11-13.
　＜設定方法＞
　以下に、明るさとデューティおよび出力との関係の設定方法の一例について説明する。 <How to set>
An example of a method of setting the relationship between brightness, duty, and output will be described below.
　この設定方法では、明るさのガンマ補正値の最小値から最大値までの変化傾向と同様の変化傾向で、パルス発光のデューティおよび光源出力の一方をその最小値から最大値まで変化させる。より詳細には、明るさのガンマ補正値の最小値から最大値までの変化と相関性を有するように、パルス発光のデューティおよび光源出力の一方をその最小値から最大値まで変化させる。そして、パルス発光のデューティおよび光源出力の他方を、対応する明るさのガンマ補正値が得られるように変化させる。 In this setting method, one of the pulse emission duty and the light source output is changed from its minimum value to its maximum value with the same change tendency as the change tendency from the minimum value to the maximum value of the gamma correction value of brightness. More specifically, one of the pulse emission duty and the light source output is changed from its minimum value to its maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value of brightness. Then, the other of the pulse emission duty and the light source output is changed so as to obtain the corresponding brightness gamma correction value.
　以下には、明るさのガンマ補正値の最小値から最大値までの変化傾向と同様の変化傾向で、光源出力をその最小値から最大値まで変化させ、パルス発光のデューティを、対応する明るさのガンマ補正値が得られるように変化させる場合の設定例を示す。 In the following, the light source output is varied from its minimum value to its maximum value with the same variation trend as the brightness gamma correction value from its minimum value to its maximum value, and the duty of the pulse emission is adjusted to the corresponding brightness. shows a setting example when changing so as to obtain a gamma correction value of .
　ガンマ補正とは、人が明るさを知覚する際の非線形性に基づいて、明るさの入力値を人の知覚に適した値に補正する、従来周知の補正処理のことである。一般に、ガンマ補正は、以下の式により規定される。 Gamma correction is a conventionally well-known correction process that corrects the brightness input value to a value suitable for human perception based on the non-linearity of human perception of brightness. In general, gamma correction is defined by the following formula.
　　Ｙ＝Ｘγ　…（１） Y=X γ (1)
　式（１）において、Ｘは明るさの入力値、Ｙはガンマ補正後の明るさの値（ガンマ補正値）である。ガンマ値γは、照明光学系２０や表示素子３０に依存する。一般的に、画像表示装置では、ガンマ値γは、１．８～２．２程度に設定される。 In Equation (1), X is the input brightness value, and Y is the brightness value after gamma correction (gamma correction value). The gamma value γ depends on the illumination optical system 20 and the display element 30. FIG. Generally, in image display devices, the gamma value γ is set to approximately 1.8 to 2.2.
　図６（ａ）は、ガンマ補正が適用された場合の明るさの入力と出力との関係を示すグラフである。図６（ｂ）は、図６（ａ）のグラフ上の各プロットにおける明るさの入力値と出力値の関係を示す図である。 FIG. 6(a) is a graph showing the relationship between brightness input and output when gamma correction is applied. FIG. 6(b) is a diagram showing the relationship between the input value and the output value of brightness in each plot on the graph of FIG. 6(a).
　ここでは、ガンマ値γが２．２に設定されている。比較のため、図６（ａ）、（ｂ）には、ガンマ値γが１．０の場合、すなわちガンマ補正が行われない場合の明るさの入力と出力の関係を示す破線のグラフとその出力値が示されている。また、明るさの入力値は、１～１００までの１００段階に区分されており、明るさの最大値を１として明るさの入力値が規格化されている。したがって、明るさのガンマ補正値も、最大値を１として規格化されている。 Here, the gamma value γ is set to 2.2. For comparison, FIGS. 6A and 6B show broken line graphs showing the relationship between brightness input and output when the gamma value γ is 1.0, that is, when no gamma correction is performed. Output values are shown. The brightness input value is divided into 100 levels from 1 to 100, and the brightness input value is standardized with 1 as the maximum brightness value. Therefore, the gamma correction value of brightness is also normalized with 1 as the maximum value.
　図６（ａ）に示すように、ガンマ補正値のグラフ（実線）は、ガンマ補正がない場合のグラフ（破線）に比べ、両端以外の範囲において、下方向に湾曲している。すなわち、ガンマ補正値は、最小値と最大値との間の範囲において、明るさの入力値よりも小さくなっている。 As shown in FIG. 6(a), the gamma correction value graph (solid line) is curved downward in the range other than both ends, compared to the graph (broken line) without gamma correction. That is, the gamma correction value is smaller than the brightness input value in the range between the minimum value and the maximum value.
　このようなガンマ補正値の変化傾向と同様の変化傾向となるように、各明るさに対する光源１１～１３の出力が算出される。 The outputs of the light sources 11 to 13 for each brightness are calculated so as to have the same changing tendency as the gamma correction value.
　以下には、赤波長帯のレーザ光を出射する光源１１に対するデューティおよび出力の設定方法が示される。その他の光源１２、１３についても、同様の設定方法により、デューティおよび出力が設定される。 A method of setting the duty and output for the light source 11 that emits laser light in the red wavelength band is shown below. The duties and outputs of the other light sources 12 and 13 are also set by a similar setting method.
　図７（ａ）は、光源１１の駆動電流と発光出力との関係の一例を示すグラフである。 FIG. 7(a) is a graph showing an example of the relationship between the driving current of the light source 11 and the light emission output.
　図７（ａ）に示すように、光源１１は、駆動電流が発光閾値に到達するまでは略発光せず、駆動電流が発光閾値を超えると、駆動電流の増加に応じて出力が増加する。このため、光源１１の出力および駆動電流は、発光閾値を超えて光源１１が安定的に発光する範囲Ｗ１、Ｗ２に設定される。図７（ａ）の例では、光源１１の出力の範囲Ｗ１が、８０ｍＷ～８００ｍＷの範囲に設定される。こうして、光源１１の出力の最小値と最大値が設定される。 As shown in FIG. 7A, the light source 11 does not emit light until the drive current reaches the light emission threshold, and when the drive current exceeds the light emission threshold, the output increases as the drive current increases. Therefore, the output and driving current of the light source 11 are set within ranges W1 and W2 in which the light source 11 stably emits light exceeding the light emission threshold. In the example of FIG. 7A, the output range W1 of the light source 11 is set within the range of 80 mW to 800 mW. Thus, the minimum and maximum values of the output of the light source 11 are set.
　この最小値と最大値が、それぞれ、最大値を１として規格化される。図７（ａ）の例では、出力の最小値および最大値がそれぞれ８０ｍＷおよび８００ｍＷであるため、規格化された最小値および最大値は、それぞれ、０．１および１となる。そして、ガンマ補正値の変化傾向と同様の変化傾向となるように、各明るさに対する光源１１～１３の規格化出力値が算出される。 The minimum and maximum values are each normalized with the maximum value being 1. In the example of FIG. 7A, the minimum and maximum output values are 80 mW and 800 mW, respectively, so the normalized minimum and maximum values are 0.1 and 1, respectively. Then, normalized output values of the light sources 11 to 13 for each brightness are calculated so as to have the same changing tendency as the gamma correction value.
　より詳細には、ガンマ補正値の最小値から最大値までの変化と相関性を有するように、規格化出力値を最小値から最大値まで変化させる。すなわち、光源１１の出力の上限と下限の範囲の規格化出力値が、規格化されたガンマ補正値（規格化ガンマ値）と線形となるように算出される。 More specifically, the normalized output value is changed from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value. That is, the normalized output value of the range between the upper limit and the lower limit of the output of the light source 11 is calculated so as to be linear with the normalized gamma correction value (normalized gamma value).
　規格化出力値の算出は、以下の式により行われ得る。 Calculation of the normalized output value can be performed by the following formula.
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　式（２）において、Ｌγは、各明るさの規格化ガンマ補正値であり、ＬγｍｉｎおよびＬγｍａｘは、それぞれ、規格化ガンマ補正値の最小値および最大値である。また、Ｐｗは、各明るさの規格化出力値であり、ＰｗｍｉｎおよびＰｗｍａｘは、それぞれ、規格化出力値の最小値および最大値である。 In Equation (2), Lγ is the normalized gamma correction value for each brightness, and Lγmin and Lγmax are the minimum and maximum normalized gamma correction values, respectively. Pw is the normalized output value of each brightness, and Pwmin and Pwmax are the minimum and maximum normalized output values, respectively.
　図７（ｂ）は、明るさの規格化入力値と光源１１の規格化出力値との関係を示す図である。 FIG. 7(b) is a diagram showing the relationship between the normalized input value of brightness and the normalized output value of the light source 11. FIG.
　図７（ｂ）に示すように、光源１１の規格化出力値の最小値と最大値との間の範囲において、各々の明るさの規格化入力値に、上記式（２）で算出された光源１１の規格化出力値が対応付けられる。そして、明るさの各規格化入力値に対応付けられた規格化ガンマ補正値および規格化出力値を用いて、各規格化入力値に対応付けられるデューティの規格化値（規格化デューティ値）が算出される。 As shown in FIG. 7(b), in the range between the minimum and maximum normalized output values of the light source 11, the normalized input value of each brightness is calculated by the above formula (2). A normalized output value of the light source 11 is associated. Then, using the normalized gamma correction value and normalized output value associated with each normalized input value of brightness, the normalized value of duty (normalized duty value) associated with each normalized input value is Calculated.
　図８は、明るさの規格化入力値とパルス発光の規格化デューティ値との関係を示す図である。 FIG. 8 is a diagram showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission.
　規格化デューティ値は、対応する規格化ガンマ補正値を、対応する規格化出力値で除することで算出される。すなわち、各明るさの規格化出力値と規格化デューティ値とを乗算すると、その明るさの規格化ガンマ補正値となる。このように、規格化出力値および規格化デューティ値を設定することにより、人の視覚に適するように表示画像の明るさを設定できる。 　The normalized duty value is calculated by dividing the corresponding normalized gamma correction value by the corresponding normalized output value. That is, by multiplying the normalized output value for each brightness by the normalized duty value, the normalized gamma correction value for that brightness is obtained. By setting the normalized output value and the normalized duty value in this way, the brightness of the display image can be set so as to be suitable for human vision.
　図９（ａ）は、明るさの規格化入力値とパルス発光の規格化デューティ値との関係を示すグラフである。図９（ｂ）は、明るさの規格化入力値と光源１１の規格化出力値との関係を示すグラフである。 FIG. 9(a) is a graph showing the relationship between the normalized input value of brightness and the normalized duty value of pulse emission. FIG. 9B is a graph showing the relationship between the normalized input value of brightness and the normalized output value of the light source 11. As shown in FIG.
　図９（ａ）、（ｂ）に示すように、何れのグラフにも明確な変曲点は生じておらず、縦軸の最小値と最大値との間の範囲では、明るさの入力値の増加に応じてデューティおよび出力の値が増加している。図９（ｂ）のグラフの最小値から最大値までの変化傾向は、図６（ａ）のグラフの最小値から最大値までの変化傾向と同様となっている。すなわち、規格化ガンマ補正値の最小値から最大値までの変化と相関性を有するように、光源１１の出力が最小値から最大値まで変化している。また、図９（ａ）のグラフにおいて、明るさの各規格化入力値に対する規格化デューティ値は、上記のように、その規格化入力値に対応する図９（ａ）の規格化出力値が乗算されると、その規格化入力値に対応する図６（ａ）の規格化ガンマ補正値が得られる値となっている。 As shown in FIGS. 9A and 9B, there is no clear inflection point in any of the graphs, and in the range between the minimum and maximum values on the vertical axis, the brightness input value The duty and output values increase as the The tendency of change from the minimum value to the maximum value in the graph of FIG. 9(b) is similar to the tendency of change from the minimum value to the maximum value of the graph of FIG. 6(a). That is, the output of the light source 11 changes from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the normalized gamma correction value. In the graph of FIG. 9(a), the normalized duty value for each normalized input value of brightness is, as described above, the normalized output value of FIG. 9(a) corresponding to the normalized input value. When multiplied, the normalized gamma correction value shown in FIG. 6A corresponding to the normalized input value is obtained.
　図１０は、上記設定方法が用いられる場合のデューティテーブル１０１ａおよび出力テーブル１０１ｂの生成方法を示すフローチャートである。 FIG. 10 is a flow chart showing a method of generating the duty table 101a and the output table 101b when the above setting method is used.
　ステップＳ１１において、明るさの各規格化入力値に上記式（１）のガンマ補正が適用されて、各明るさの規格化ガンマ補正値が算出される。これにより、図６（ｂ）に示すように、明るさの各規格化入力値に対応する規格化ガンマ補正値が取得される。 In step S11, the gamma correction of the above formula (1) is applied to each normalized input value of brightness to calculate the normalized gamma correction value of each brightness. As a result, as shown in FIG. 6B, the normalized gamma correction value corresponding to each normalized input value of brightness is acquired.
　ステップＳ１２において、図７（ａ）を参照して説明したように、光源１１の出力の最小値および最大値が設定され、設定された最小値および最大値が、その最大値によってそれぞれ規格化される。 In step S12, as described with reference to FIG. 7A, the minimum and maximum values of the output of the light source 11 are set, and the set minimum and maximum values are normalized by the maximum value. be.
　ステップＳ１３において、規格化された出力の最大値（上限）と最小値（下限）との間の範囲における規格化出力値が、規格化ガンマ補正値と線形となるように、上記式（２）により算出される。これにより、図７（ｂ）に示すように、明るさの各規格化入力値に対応する規格化出力値が取得される。 In step S13, the normalized output value in the range between the maximum value (upper limit) and the minimum value (lower limit) of the normalized output is linear with the normalized gamma correction value. Calculated by As a result, as shown in FIG. 7B, the normalized output value corresponding to each normalized input value of brightness is acquired.
　ステップＳ１４において、規格化出力値との乗算値がその規格化出力値に対応するガンマ補正値となるように、各規格化出力値に対応する規格化デューティ値が算出される。これにより、図８に示すように、明るさの各規格化入力値に対応する規格化デューティ値が取得される。 In step S14, the normalized duty value corresponding to each normalized output value is calculated so that the multiplied value with the normalized output value becomes the gamma correction value corresponding to the normalized output value. Thereby, as shown in FIG. 8, the normalized duty value corresponding to each normalized input value of brightness is obtained.
　ステップＳ１５において、各々の規格化デューティ値にパルス発光のデューティの最大値（たとえば、３３％）を乗じて、デューティテーブルが生成される。ステップＳ１６において、規格化出力値に光源１１の発光出力の最大値（たとえば、８００ｍＷ）を乗じて、出力テーブルが生成される。こうして、図５（ａ）、（ｂ）に示した構成のデューティテーブル１０１ａおよび出力テーブル１０１ｂが生成される。 In step S15, each normalized duty value is multiplied by the maximum pulse emission duty value (eg, 33%) to generate a duty table. In step S16, an output table is generated by multiplying the normalized output value by the maximum value of the light emission output of the light source 11 (800 mW, for example). Thus, the duty table 101a and the output table 101b configured as shown in FIGS. 5(a) and 5(b) are generated.
　＜明るさ制御＞
　図１１は、表示画像の明るさを制御するための処理を示すフローチャートである。 <Brightness control>
FIG. 11 is a flow chart showing processing for controlling the brightness of the display image.
　表示画像の明るさは、たとえば、周囲の明るさに応じて自動で設定される。この場合、周囲の明るさを検出するための照度センサが用いられる。システムコントローラは、照度と明るさのレベルとの関係を規定する関係式またはテーブルから、照度センサの検出値に対応する明るさのレベルを随時取得し、取得した明るさのレベルを、図２の制御部１０１に出力する。あるいは、表示画像の明るさは、入力インタフェースを介して、ユーザが設定してもよい。この場合、システムコントローラは、画像表示装置１の動作開始時に、明るさのデフォルト値を図２の制御部１０１に出力し、その後、ユーザの入力に応じて、入力された明るさのレベルを制御部１０１に出力する。 The brightness of the displayed image is automatically set according to the ambient brightness, for example. In this case, an illuminance sensor is used to detect ambient brightness. The system controller acquires the brightness level corresponding to the detection value of the illuminance sensor from a relational expression or table that defines the relationship between the illuminance and the brightness level, and converts the acquired brightness level to the brightness level shown in FIG. Output to the control unit 101 . Alternatively, the brightness of the displayed image may be set by the user via the input interface. In this case, the system controller outputs a default brightness value to the control unit 101 in FIG. Output to the unit 101 .
　なお、以下の処理において、制御部１０１は、光源１１～１３ごとに、デューティテーブル１０１ａおよび出力テーブル１０１ｂを保持している。 It should be noted that in the following processing, the control unit 101 holds a duty table 101a and an output table 101b for each of the light sources 11-13.
　画像表示装置１の動作が開始すると、制御部１０１は、動作開始時に入力された処理の明るさの値に対応するデューティ値および出力値を、光源１１～１３ごとに、デューティテーブル１０１ａおよび出力テーブル１０１ｂから取得し、取得したデューティ値および出力値を各光源に設定する（Ｓ１０１）。 When the operation of the image display apparatus 1 is started, the control unit 101 stores the duty values and output values corresponding to the processing brightness values input at the start of the operation, for each of the light sources 11 to 13, in the duty table 101a and the output table. 101b, and sets the acquired duty value and output value to each light source (S101).
　その後、制御部１０１は、時分割で設定された各光源の発光タイミングが到来すると（Ｓ１０２：ＹＥＳ）、ステップＳ１０１で設定されたデューティ値および出力値により、各光源をパルス発光させる（Ｓ１０３）。そして、制御部１０１は、表示動作が終了したか否かを判定し（Ｓ１０４）、表示動作が終了していない場合は（Ｓ１０４：ＮＯ）、明るさの設定が変更されたか否かを判定する（Ｓ１０５）。 After that, when the time-divisionally set light emission timing of each light source arrives (S102: YES), the control unit 101 causes each light source to emit pulse light according to the duty value and output value set in step S101 (S103). Then, the control unit 101 determines whether or not the display operation has ended (S104), and if the display operation has not ended (S104: NO), determines whether or not the brightness setting has been changed. (S105).
　明るさの設定が変更されていない場合（Ｓ１０５：ＮＯ）、制御部１０１は、処理をステップＳ１０２に戻して、同様の処理を実行する。他方、明るさの設定が変更された場合（Ｓ１０５：ＹＥＳ）、制御部１０１は、処理をステップＳ１０１に戻す。そして、制御部１０１は、新たな明るさの値に対応するデューティ値および出力値を、光源１１～１３ごとに、デューティテーブル１０１ａおよび出力テーブル１０１ｂから取得し、取得したデューティ値および出力値を各光源に設定する。こうして、表示画像の明るさが変更される。 If the brightness setting has not been changed (S105: NO), the control unit 101 returns the process to step S102 and performs the same process. On the other hand, if the brightness setting has been changed (S105: YES), the control unit 101 returns the process to step S101. Then, the control unit 101 acquires the duty value and the output value corresponding to the new brightness value from the duty table 101a and the output table 101b for each of the light sources 11 to 13, and stores the acquired duty value and output value in each Set the light source. Thus, the brightness of the displayed image is changed.
　制御部１０１は、表示動作が終了するまで（Ｓ１０４：ＮＯ）、同様の処理を繰り返す。その後、表示動作が終了すると（Ｓ１０４：ＹＥＳ）、制御部１０１は、図１１の処理を終了する。 The control unit 101 repeats similar processing until the display operation is completed (S104: NO). After that, when the display operation ends (S104: YES), the control unit 101 ends the processing of FIG.
　＜実施形態の効果＞
　上記実施形態によれば、以下の効果が奏される。 <Effects of Embodiment>
According to the above embodiment, the following effects are achieved.
　図４（ａ）、（ｂ）に示したように、制御部１０１は、光源１１～１３の出力を明るさの変化に応じて最小値から最大値まで一方向に変化させ、パルス発光のデューティを、対応する明るさのガンマ補正値が得られるように変化させる。これにより、デューティおよび出力の何れにも変曲点が生じることがない。よって、明るさ変更時にユーザに違和感を与えることなく、表示画像の明るさを制御できる。また、図８を参照して説明したように、各明るさのデューティ値は、そのデューティ値とその明るさに対応する出力値とによってその明るさのガンマ補正値が得られるように設定される。これにより、人の視覚に適するように表示画像の明るさを変化させることができる。よって、表示画像の明るさが変化した場合のユーザの違和感を効果的に抑制できる。 As shown in FIGS. 4A and 4B, the control unit 101 changes the outputs of the light sources 11 to 13 in one direction from the minimum value to the maximum value according to the change in brightness, and the duty of pulse emission. is varied so as to obtain the gamma correction value for the corresponding brightness. As a result, neither the duty nor the output has an inflection point. Therefore, the brightness of the displayed image can be controlled without giving the user a sense of discomfort when the brightness is changed. Also, as described with reference to FIG. 8, the duty value for each brightness is set so that the gamma correction value for that brightness can be obtained from the duty value and the output value corresponding to that brightness. . Thereby, the brightness of the display image can be changed so as to be suitable for human vision. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes.
　図７（ａ）、（ｂ）を参照して説明したように、制御部１０１は、ガンマ補正値の最小値から最大値までの変化傾向と同様の変化傾向で、光源１１～１３の出力をその最小値から最大値まで変化させる。より詳細には、制御部１０１は、ガンマ補正値の最小値から最大値までの変化と相関性を有するように、光源１１～１３の出力をその最小値から最大値まで変化させる。すなわち、制御部１０１は、上記式（２）に基づいて、各明るさのガンマ補正値と線形となるように、光源１１～１３の出力値を設定する。これにより、光源１１～１３の出力をガンマ補正値の変化に追従させることができる。よって、明るさに対する人の視覚に適するように、光源１１～１３の出力を変化させることができる。 As described with reference to FIGS. 7A and 7B, the control unit 101 adjusts the outputs of the light sources 11 to 13 with the same change tendency as the change tendency from the minimum value to the maximum value of the gamma correction value. Vary from its minimum value to its maximum value. More specifically, the control unit 101 changes the outputs of the light sources 11 to 13 from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value. That is, the control unit 101 sets the output values of the light sources 11 to 13 so as to be linear with the gamma correction value of each brightness based on the above equation (2). This allows the outputs of the light sources 11 to 13 to follow changes in the gamma correction value. Therefore, the outputs of the light sources 11 to 13 can be changed so as to suit the human vision for brightness.
　図８を参照して説明したとおり、各明るさの規格化デューティ値および規格化出力値を乗算した乗算値は、その明るさの規格化ガンマ補正値となっている。これにより、各明るさのデューティ値および出力値で光源１１～１３を発光させることで、人の視覚に適するように表示画像の明るさを変化させることができる。 As described with reference to FIG. 8, the multiplied value obtained by multiplying the normalized duty value and the normalized output value for each brightness is the normalized gamma correction value for that brightness. Thus, by causing the light sources 11 to 13 to emit light with the duty value and output value of each brightness, it is possible to change the brightness of the display image so as to suit human vision.
　図２および図５に示したように、制御部１０１は、明るさの値にデューティおよび出力の値を対応づけたデューティテーブル１０１ａおよび出力テーブル１０１ｂを保持し、これらテーブルに基づいて、設定対象の明るさの値に対するデューティおよび出力の値を取得する。これにより、制御部１０１は、明るさの変更時に、デューティおよび出力の値を取得するための演算を行うことなく、デューティおよび出力の値を簡易に取得できる。 As shown in FIGS. 2 and 5, the control unit 101 holds a duty table 101a and an output table 101b in which a brightness value is associated with a duty and an output value. Get the duty and output values for a brightness value. As a result, the control unit 101 can easily acquire the duty and output values without performing calculations for acquiring the duty and output values when the brightness is changed.
　図１に示したように、画像表示装置１は、出射波長が互いに異なる複数の光源１１～１３を備え、図１１に示したように、制御部１０１は、光源ごとに、明るさに応じたデューティおよび出力を設定する制御（Ｓ１０１）を行う。これにより、光源１１～１３の何れについても、図３（ａ）、（ｂ）のような変曲点が生じることがない。よって、表示画像の明るさが変化した場合のユーザの違和感を効果的に抑制でき、また、人の視覚に適するように表示画像の明るさを変化させることができる。 As shown in FIG. 1, the image display device 1 includes a plurality of light sources 11 to 13 having different emission wavelengths, and as shown in FIG. Control (S101) for setting duty and output is performed. As a result, inflection points such as those shown in FIGS. 3A and 3B do not occur in any of the light sources 11-13. Therefore, it is possible to effectively suppress the discomfort of the user when the brightness of the display image changes, and to change the brightness of the display image so as to be suitable for human vision.
　＜変更例１＞
　変更例１では、光源１１～１３の出射光量を検出するための光検出器がさらに配置され、光検出器を介して検出した各光源の出射光量と、設定対象の明るさに対応する光量との差分が抑制されるように、デューティおよび出力の少なくとも一方が補正される。 <Modification 1>
In Modification 1, a photodetector for detecting the amount of light emitted from the light sources 11 to 13 is further arranged, and the amount of light emitted from each light source detected via the photodetector and the amount of light corresponding to the brightness to be set are detected. At least one of the duty and the output is corrected so that the difference in is suppressed.
　すなわち、上記実施形態に示した方法により、デューティおよび出力が設定されても、光源１１～１３の温度等の条件により、目標の明るさが得られないことが起こり得る。そこで、変更例１では、上記のようにデューティおよび出力を設定して光源１１～１３をパルス発光させた場合の各光源の実際の出射光量が光検出器により検出され、検出された実際の出射光量と、設定対象の明るさに対応する光量との差分が抑制されるように、デューティおよび出力の少なくとも一方が補正される。 That is, even if the duty and output are set by the method shown in the above embodiment, the target brightness may not be obtained due to conditions such as the temperature of the light sources 11-13. Therefore, in Modification 1, the actual emitted light amount of each light source is detected by the photodetector when the duty and output are set as described above and the light sources 11 to 13 emit pulsed light, and the detected actual emitted light amount is detected by the photodetector. At least one of the duty and the output is corrected so that the difference between the amount of light and the amount of light corresponding to the brightness to be set is suppressed.
　図１２は、変更例１に係る、画像表示装置１の光学系の構成を示す平面図である。 12 is a plan view showing the configuration of the optical system of the image display device 1 according to Modification 1. FIG.
　図１２の光学系では、図１に比べて、分光素子２９と、光検出器６０が追加されている。分光素子２９は、ダイクロイックミラー２２ｂ側から入射する各色の光の大半を透過し、これらの光の一部のみを反射する。分光素子２９として、たとえば、ガラス平板が用いられる。光検出器６０は、分光素子２９によって反射された各色の光を受光して受光強度に応じた信号を出力する。 In the optical system of FIG. 12, a spectral element 29 and a photodetector 60 are added as compared with FIG. The spectroscopic element 29 transmits most of the light of each color incident from the dichroic mirror 22b side, and reflects only part of the light. For example, a flat glass plate is used as the spectral element 29 . The photodetector 60 receives the light of each color reflected by the spectral element 29 and outputs a signal corresponding to the received light intensity.
　図１３は、変更例１に係る、表示画像の明るさを制御するためのフローチャートである。 FIG. 13 is a flowchart for controlling the brightness of the display image according to Modification 1. FIG.
　図１３のフローチャートは、図１１のフローチャートに比べて、ステップＳ１１１～Ｓ１１３が追加されている。ステップＳ１１１～Ｓ１１３以外の各ステップにおける処理は、図１１の対応するステップと同様である。 Compared to the flowchart of FIG. 11, the flowchart of FIG. 13 has steps S111 to S113 added. Processing in steps other than steps S111 to S113 is the same as the corresponding steps in FIG.
　ステップＳ１０３において赤、緑および青の何れかの光を発光させると、制御部１０１は、光検出器６０の検出値をパルス発光期間に亘って積算し、この積算値を受光光量として取得する（Ｓ１１１）。制御部１０１は、各明るさの値と、その明るさを実現するための受光光量（積算値）の基準値とを対応付けたテーブルを、光源１１～１３ごとに予め保持している。制御部１０１は、現在設定されている明るさに対応する基準値を制御対象の光源のテーブルから取得し、取得した基準値と、ステップＳ１１１で取得した積算値との差分を算出する（Ｓ１１２）。そして、制御部１０１は、この差分が抑制されるように、制御対象の光源の出力を補正する（Ｓ１１３）。 When any one of red, green, and blue light is emitted in step S103, the control unit 101 integrates the detection value of the photodetector 60 over the pulse emission period, and acquires the integrated value as the received light amount ( S111). The control unit 101 preliminarily holds, for each of the light sources 11 to 13, a table in which each brightness value is associated with a reference value of the amount of received light (integrated value) for realizing the brightness. The control unit 101 acquires the reference value corresponding to the currently set brightness from the table of the light sources to be controlled, and calculates the difference between the acquired reference value and the integrated value acquired in step S111 (S112). . Then, the control unit 101 corrects the output of the light source to be controlled so that this difference is suppressed (S113).
　制御部１０１は、各色の光をパルス発光させるごとに、ステップＳ１１１～Ｓ１１３を実行する。これにより、各色の発光光量が、明るさの設定値に対応する光量に収束される。よって、光源１１～１３に温度変化等が生じた場合も、設定された明るさで表示画像を表示させることができる。 The control unit 101 executes steps S111 to S113 each time light of each color is pulsed. As a result, the emitted light amount of each color converges to the light amount corresponding to the brightness setting value. Therefore, even if the temperature of the light sources 11 to 13 changes, the display image can be displayed with the set brightness.
　なお、ここでは、ステップＳ１１３において、光源１１～１３の出力が補正されたが、これに代えて、あるいはこれとともに、各光源のパルス発光のデューティが、差分値を抑制するよう補正されてもよい。 Here, in step S113, the outputs of the light sources 11 to 13 are corrected, but instead of or together with this, the pulse emission duty of each light source may be corrected so as to suppress the difference value. .
　＜変更例２＞
　変更例２では、光源１１～１３付近の温度を検出するための温度センサがさらに配置され、温度センサにより検出された温度に応じて、設定に用いるデューティテーブルおよび出力テーブルが変更される。すなわち、制御部１０１は、複数の温度に対してそれぞれデューティテーブルおよび出力テーブルを保持し、温度センサによって検出された温度に対応するデューティテーブルおよび出力テーブルを用いて、設定対象の明るさの値に対するデューティおよび出力の値を取得する。 <Modification 2>
In Modification 2, a temperature sensor for detecting the temperature near the light sources 11 to 13 is further arranged, and the duty table and the output table used for setting are changed according to the temperature detected by the temperature sensor. That is, the control unit 101 holds a duty table and an output table for a plurality of temperatures, and uses the duty table and the output table corresponding to the temperature detected by the temperature sensor to determine the brightness value to be set. Get duty and output values.
　図１４は、変更例２に係る、画像表示装置１の光学系の構成を示す平面図である。 14 is a plan view showing the configuration of the optical system of the image display device 1 according to Modification 2. FIG.
　図１４の光学系では、図１に比べて、温度センサ７０が追加されている。温度センサ７０は、光源１１～１３に接近して配置され、光源１１～１３付近の温度を検出する。図１４の構成では、１つの温度センサ７０で光源１１～１３付近の温度が検出される。これに代えて、光源１１～１３ごとに温度センサが配置され、各光源の温度が個別に検出されてもよい。 In the optical system of FIG. 14, a temperature sensor 70 is added compared to FIG. A temperature sensor 70 is placed close to the light sources 11-13 to detect the temperature in the vicinity of the light sources 11-13. In the configuration of FIG. 14, one temperature sensor 70 detects the temperature near the light sources 11-13. Alternatively, a temperature sensor may be arranged for each of the light sources 11-13 and the temperature of each light source may be detected individually.
　図１５は、温度が変化した場合の光源１１の駆動電流と発光出力との関係を模式的に示すグラフである。図１５では、光源１１の温度がｔ１～ｔ７である場合の各グラフが示されている。 FIG. 15 is a graph schematically showing the relationship between the driving current of the light source 11 and the light emission output when the temperature changes. FIG. 15 shows respective graphs when the temperature of the light source 11 is t1 to t7.
　図１５に示すように、光源１１の温度変化に伴い、発光閾値が変化し、且つ、同一駆動電流に対する発光出力が変化する。このため、図７（ａ）に示した光源１１の出力範囲Ｗ１は、温度に応じて変更するとよく、これに伴い、図７（ｂ）に示した規格化出力値の最小値および最大値も温度に応じて変更するとよい。たとえば、図１５の例では、温度がｔ１～ｔ３の範囲では、光源１１の出力範囲は範囲Ｗ１１に設定され得る。他方、温度がｔ７の場合、光源の出力範囲は範囲Ｗ１２に設定され得る。 As shown in FIG. 15, as the temperature of the light source 11 changes, the light emission threshold changes, and the light emission output for the same drive current also changes. Therefore, the output range W1 of the light source 11 shown in FIG. 7(a) may be changed according to the temperature. It should be changed according to the temperature. For example, in the example of FIG. 15, the output range of light source 11 can be set to range W11 when the temperature is in the range of t1 to t3. On the other hand, if the temperature is t7, the power range of the light source can be set to range W12.
　この場合、温度がｔ１～ｔ３の範囲では、最小出力値Ｐｗ＿ｍｉｎ１および最大出力値Ｐｗ＿ｍａｘ１に基づいて上記式（２）から、各明るさの規格化出力値が設定される。また、温度がｔ７の場合は、最小出力値Ｐｗ＿ｍｉｎ２および最大出力値Ｐｗ＿ｍａｘ２に基づいて上記式（２）から、各明るさの規格化出力値が設定される。温度がｔ４、ｔ５、ｔ６にある場合も、同様に、最小出力値および最大出力値が調整されて、上記式（２）から、各明るさの規格化出力値が設定される。したがって、各明るさの規格化デューティ値も、温度ごとに変化する。その結果、各光源のデューティテーブルおよび出力テーブルも、温度ごとに異なることになる。 In this case, in the temperature range of t1 to t3, the normalized output value for each brightness is set from the above equation (2) based on the minimum output value Pw_min1 and the maximum output value Pw_max1. Further, when the temperature is t7, the normalized output value for each brightness is set from the above equation (2) based on the minimum output value Pw_min2 and the maximum output value Pw_max2. Similarly, when the temperatures are at t4, t5, and t6, the minimum output value and maximum output value are adjusted, and the normalized output value for each brightness is set from the above equation (2). Therefore, the normalized duty value of each brightness also changes for each temperature. As a result, the duty table and output table of each light source also differ for each temperature.
　このように、変更例２では、各光源のデューティテーブルおよび出力テーブルが、温度ごとに規定される。すなわち、図２の制御部１０１は、光源１１～１３の各々に対して、対象温度が互いに異なる複数種類のデューティテーブル１０１ａおよび出力テーブル１０１ｂを保持している。 Thus, in Modification 2, the duty table and output table of each light source are defined for each temperature. That is, the control unit 101 of FIG. 2 holds a plurality of types of duty tables 101a and output tables 101b with different target temperatures for each of the light sources 11-13.
　図１６は、変更例２に係る、光源１１～１３の制御に用いるデューティテーブルおよび出力テーブルの選択処理を示すフローチャートである。 FIG. 16 is a flowchart showing selection processing of the duty table and the output table used for controlling the light sources 11 to 13 according to Modification 2. FIG.
　画像表示装置１の動作が開始すると、制御部１０１は、温度センサ７０から温度を取得し（Ｓ２０１）、取得した温度に対応するデューティテーブルおよび出力テーブルを、制御に用いるテーブルとして選択する（Ｓ２０２）。制御部１０１は、選択したデューティテーブルおよび出力テーブルを用いて、図１１または図１２の制御を行う。制御部１０１は、画像表示装置１の動作が終了するまで（Ｓ２０３：ＮＯ）、ステップＳ２０１の処理を繰り返し実行する。その間に、光源１１～１３付近の温度が各テーブルを変更する程度まで変化すると、ステップＳ２０２において、制御に用いるテーブルが、新たな温度に対応するデューティテーブルおよび出力テーブルに変更される。これにより、図１１または図１２の制御に用いるテーブルが随時切り替えられる。 When the image display device 1 starts operating, the control unit 101 acquires the temperature from the temperature sensor 70 (S201), and selects the duty table and the output table corresponding to the acquired temperature as tables to be used for control (S202). . The control unit 101 performs the control shown in FIG. 11 or 12 using the selected duty table and output table. The control unit 101 repeatedly executes the process of step S201 until the operation of the image display device 1 is completed (S203: NO). In the meantime, when the temperature around the light sources 11 to 13 changes to such an extent that each table is changed, the tables used for control are changed to the duty table and output table corresponding to the new temperature in step S202. As a result, the table used for the control in FIG. 11 or 12 can be switched at any time.
　変更例２の構成によれば、光源１１の温度に適するデューティテーブルおよび出力テーブルが光源１１～１３の制御に用いられるため、光源１１～１３の制御を、より適正かつ円滑に行い得る。よって、表示画像の明るさを所定の明るさに適切に制御できる。 According to the configuration of Modification 2, the duty table and the output table suitable for the temperature of the light source 11 are used for controlling the light sources 11 to 13, so that the light sources 11 to 13 can be controlled more appropriately and smoothly. Therefore, it is possible to appropriately control the brightness of the display image to a predetermined brightness.
　＜変更例３＞
　上記実施形態では、図７（ｂ）を参照して説明したとおり、規格化ガンマ補正値に式（２）を適用して規格化出力値が算出され、その後、規格化ガンマ補正値と規格化出力値とに基づいて規格化デューティ値が算出された。しかしながら、これに限らず、規格化ガンマ補正値と線形となるように、先に、規格化デューティ値が算出され、その後、規格化ガンマ補正値と規格化デューティ値とに基づいて規格化出力値が算出されてもよい。 <Modification 3>
In the above embodiment, as described with reference to FIG. 7B, the normalized output value is calculated by applying the formula (2) to the normalized gamma correction value, A normalized duty value was calculated based on the output value. However, not limited to this, the normalized duty value is first calculated so as to be linear with the normalized gamma correction value, and then the normalized output value is calculated based on the normalized gamma correction value and the normalized duty value. may be calculated.
　この場合、各明るさの規格化デューティ値は、以下の式により算出され得る。 In this case, the normalized duty value of each brightness can be calculated by the following formula.
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
　式（２）において、Ｌγは、各明るさの規格化ガンマ補正値であり、ＬγｍｉｎおよびＬγｍａｘは、それぞれ、規格化ガンマ補正値の最小値および最大値である。また、Ｄは、各明るさの規格化デューティ値であり、ＤｍｉｎおよびＤｍａｘは、それぞれ、規格化デューティ値の最小値および最大値である。 In Equation (2), Lγ is the normalized gamma correction value for each brightness, and Lγmin and Lγmax are the minimum and maximum normalized gamma correction values, respectively. D is the normalized duty value of each brightness, and Dmin and Dmax are the minimum and maximum normalized duty values, respectively.
　規格化出力値は、各明るさの規格化デューティ値との乗算値がその明るさの規格化ガンマ値となるように算出される。ただし、この場合、規格化出力値の最小値に光源出力の最大値（図７（ａ）の例では８００ｍＷ）を乗じた値が、当該光源の発光閾値より大きくなっている必要がある。したがって、変更例３では、この条件が充足されるように、規格化デューティ値の最小値および最大値が設定される。 The normalized output value is calculated so that the multiplied value by the normalized duty value of each brightness becomes the normalized gamma value of that brightness. However, in this case, the product of the minimum normalized output value and the maximum light source output value (800 mW in the example of FIG. 7A) must be greater than the light emission threshold of the light source. Therefore, in Modification 3, the minimum and maximum normalized duty values are set so as to satisfy this condition.
　図１７は、変更例３に係る、デューティテーブル１０１ａおよび出力テーブル１０１ｂの生成方法を示すフローチャートである。 FIG. 17 is a flow chart showing a method of generating the duty table 101a and the output table 101b according to the third modification.
　図１７のフローチャートは、図１０のフローチャートのステップＳ１２～Ｓ１４がステップＳ２１～Ｓ２３に置き換えられている。図１７のステップＳ１１、Ｓ１５、Ｓ１６の処理は、図１０の対応するステップと同様である。 In the flowchart of FIG. 17, steps S12-S14 of the flowchart of FIG. 10 are replaced with steps S21-S23. The processes of steps S11, S15, and S16 in FIG. 17 are the same as the corresponding steps in FIG.
　ステップＳ２１において、パルス発光のデューティの最小値および最大値が設定され、設定された最小値および最大値が、その最大値によって規格化される。 In step S21, the minimum and maximum values of the pulse emission duty are set, and the set minimum and maximum values are normalized by the maximum value.
　ステップＳ２２において、規格化されたデューティの最大値（上限）と最小値（下限）との間の範囲における規格化デューティ値が、規格化ガンマ補正値と線形となるように算出される。この算出は、上記式（３）により行われる。これにより、明るさの各規格化入力値に対応する規格化デューティ値が取得される。 In step S22, the normalized duty value in the range between the maximum value (upper limit) and minimum value (lower limit) of the normalized duty is calculated so as to be linear with the normalized gamma correction value. This calculation is performed by the above formula (3). As a result, a normalized duty value corresponding to each normalized input value of brightness is obtained.
　ステップＳ２３において、規格化デューティ値との乗算値がその規格化デューティ値に対応する規格化ガンマ補正値となるように、各規格化デューティ値に対応する規格化出力値が算出される。これにより、明るさの各規格化入力値に対応する規格化出力値が取得される。 In step S23, the normalized output value corresponding to each normalized duty value is calculated so that the multiplied value with the normalized duty value becomes the normalized gamma correction value corresponding to the normalized duty value. As a result, a normalized output value corresponding to each normalized input value of brightness is obtained.
　その後、ステップＳ１５において、各々の規格化デューティ値にパルス発光のデューティの最大値を乗じて、デューティテーブルが生成される。また、ステップＳ１６において、規格化出力値に光源１１の発光出力の最大値を乗じて、出力テーブルが生成される。こうして、デューティテーブル１０１ａおよび出力テーブル１０１ｂの生成が終了する。 After that, in step S15, each normalized duty value is multiplied by the maximum value of the pulse emission duty to generate a duty table. Further, in step S16, the normalized output value is multiplied by the maximum value of the light emission output of the light source 11 to generate an output table. Thus, the generation of the duty table 101a and the output table 101b is completed.
　この場合も、上記実施形態と同様、光源１１～１３ごとに、デューティテーブル１０１ａおよび出力テーブル１０１ｂが生成されてよい。また、上記変更例２と同様、光源１１～１３の温度ごとに、さらに、デューティテーブル１０１ａおよび出力テーブル１０１ｂが生成されてもよい。 Also in this case, the duty table 101a and the output table 101b may be generated for each of the light sources 11 to 13, as in the above embodiment. Further, as in the second modification, a duty table 101a and an output table 101b may be generated for each temperature of the light sources 11-13.
　＜その他の変更例＞
　上記実施形態および変更例１、２では、各明るさのガンマ補正値に対して線形となるように、各明るさの出力値が設定されたが、各明るさの出力値は、必ずしも、各明るさのガンマ補正値に対して線形となっていなくてもよく、最小値から最大値まで一方向に変化する限りにおいて、他の方法により設定されてもよい。たとえば、最小値から最大値までリニアに変化するように各明るさの出力値が変化してもよい。 <Other modification examples>
In the above embodiment and modification examples 1 and 2, the output value for each brightness is set so as to be linear with respect to the gamma correction value for each brightness. It may not be linear with respect to the brightness gamma correction value, and may be set by other methods as long as it changes in one direction from the minimum value to the maximum value. For example, each brightness output value may change so as to change linearly from the minimum value to the maximum value.
　この場合も、各明るさのデューティ値は、その明るさの出力値とともに、その明るさのガンマ補正値が得られるように設定されればよい。すなわち、各明るさの規格化デューティ値は、その明るさの規格化出力値が乗算されるとその明るさの規格化ガンマ補正値が得られるように、設定されればよい。変更例３においても、同様、各明るさのデューティ値は、各明るさのガンマ補正値に対して線形となっていなくてもよく、最小値から最大値まで一方向に変化する限りにおいて、他の方法により設定されてもよい。 Also in this case, the duty value for each brightness should be set so that the output value for that brightness and the gamma correction value for that brightness are obtained. That is, the normalized duty value for each brightness may be set so that the normalized gamma correction value for that brightness is obtained when multiplied by the normalized output value for that brightness. Similarly, in Modification 3, the duty value of each brightness does not have to be linear with respect to the gamma correction value of each brightness. may be set by the method of
　また、上記実施形態および変更例１、２では、デューティテーブル１０１ａおよび出力テーブル１０１ｂから設定対象の明るさのデューティ値および出力値が取得されたが、設定対象の明るさのデューティ値および出力値が演算により求められてもよい。 Further, in the above-described embodiment and modified examples 1 and 2, the duty value and output value of the brightness to be set are obtained from the duty table 101a and the output table 101b. It may be obtained by calculation.
　この場合、制御部１０１は、たとえば、設定対象の明るさの値から上記式（１）により規格化ガンマ補正値を算出し、算出した規格化ガンマ補正値と発光出力の規格化最小値および規格化最大値とを上記式（２）に適用して、設定対象の明るさの規格化出力値を算出する。次に、制御部１０１は、算出した規格化出力値との乗算値が、上記式（１）から算出した上記規格化ガンマ補正値となるように、設定対象の明るさの規格化デューティ値を算出する。そして、制御部１０１は、算出した規格化出力値および規格化デューティ値にそれぞれ出力値の最大値およびデューティ値の最大値を乗算して、設定対象の明るさに対する出力値およびデューティ値を算出する。 In this case, the control unit 101 calculates, for example, the normalized gamma correction value from the brightness value to be set by the above formula (1), and the calculated normalized gamma correction value, the normalized minimum value of the light emission output, and the standard By applying the normalized maximum value to the above equation (2), the normalized output value of the brightness to be set is calculated. Next, the control unit 101 sets the normalized duty value of the brightness to be set so that the multiplied value by the calculated normalized output value becomes the normalized gamma correction value calculated from the above equation (1). calculate. Then, the control unit 101 multiplies the calculated normalized output value and normalized duty value by the maximum value of the output value and the maximum value of the duty value, respectively, to calculate the output value and the duty value for the brightness to be set. .
　なお、この場合、設定対象の明るさに対する出力値およびデューティ値は、上記算出過程の中間を省略して直接、明るさの設定値から算出されてもよい。また、上記変更例３においても、同様に、設定対象の明るさのデューティ値および出力値が演算により求められてもよい。 In this case, the output value and duty value for the brightness to be set may be calculated directly from the brightness setting value by omitting the intermediate steps in the above calculation process. Also in the third modification, the duty value and the output value of the brightness to be set may be similarly calculated.
　また、図５（ａ）、（ｂ）のテーブルに代えて、図８に示した各明るさと規格化出力値および規格化デューティ値とを対応付けた情報（テーブル）が、制御部１０１に保持されてもよい。この場合、制御部１０１は、設定対象の明るさに対応する規格化出力値および規格化デューティ値をこの情報（テーブル）から取得し、取得した規格化出力値および規格化デューティ値にそれぞれ出力の最大値およびデューティ値の最大値を乗算して、設定対象の明るさに対応する出力値およびデューティ値を算出する。 Instead of the tables in FIGS. 5A and 5B, the control unit 101 holds information (table) in which each brightness shown in FIG. 8 is associated with the normalized output value and the normalized duty value. may be In this case, the control unit 101 obtains the normalized output value and the normalized duty value corresponding to the brightness to be set from this information (table), and outputs the normalized output value and the normalized duty value to the obtained normalized output value and the normalized duty value. By multiplying the maximum value and the maximum value of the duty value, the output value and duty value corresponding to the brightness to be set are calculated.
　また、上記実施形態および変更例１～３では、赤、緑および青の波長帯のレーザ光をそれぞれ出射する３つの光源１１～１３が画像の表示に用いられたが、画像に表示に用いる光源の種類は、これに限られない。たとえば、単色の画像を表示する場合、画像表示装置１は、光源１１～１３の何れか１つのみを備えていてもよい。この場合、制御部１０１は、この光源についてのみデューティテーブル１０１ａおよび出力テーブル１０１ｂを保持しておけばよい。また、赤、緑および青の波長帯のレーザ光をそれぞれ出射する３つの光源１１～１３とともに、さらに他の色の波長帯のレーザ光を出射する光源が、画像の表示に用いられてもよい。この場合、他の色の波長帯のレーザ光源についても、上記と同様、パルス発光のデューティと発光出力とが制御されればよい。 In addition, in the above-described embodiment and modifications 1 to 3, the three light sources 11 to 13 that respectively emit laser light in the red, green, and blue wavelength bands are used to display images. type is not limited to this. For example, when displaying a monochromatic image, the image display device 1 may include only one of the light sources 11-13. In this case, the control section 101 may hold the duty table 101a and the output table 101b only for this light source. Further, in addition to the three light sources 11 to 13 that respectively emit laser light in red, green, and blue wavelength bands, a light source that emits laser light in other color wavelength bands may be used for image display. . In this case, the duty of pulse emission and the emission output of laser light sources of wavelength bands of other colors may be controlled in the same manner as described above.
　また、画像表示装置１の光学系の構成は、上記実施形態１および変更例１～３に示した構成に限られるものではない。たとえば、光源１１～１３ごとに表示素子が個別に配置され、各表示素子で変調された各色のレーザ光が、複数のダイクロイックミラーで統合されてもよい。 Also, the configuration of the optical system of the image display device 1 is not limited to the configurations shown in the first embodiment and the first to third modifications. For example, a display element may be arranged individually for each of the light sources 11 to 13, and the laser light of each color modulated by each display element may be integrated by a plurality of dichroic mirrors.
　また、上記実施形態および変更例１～３では、レーザ光を変調するための表示素子として反射型の液晶パネルが用いられたが、レーザ光を変調するための表示素子は、これに限られるものではない。たとえば、透過型の液晶パネルや、デジタルミラーデバイス（ＤＭＤ）等の他の方式の表示素子が、レーザ光の変調に用いられてもよい。この場合、表示素子の方式の変更に応じて、光学系の構成が変更されればよい。 In addition, in the above embodiment and modification examples 1 to 3, a reflective liquid crystal panel is used as a display element for modulating laser light, but the display element for modulating laser light is limited to this. isn't it. For example, a transmissive liquid crystal panel or a display element of another type such as a digital mirror device (DMD) may be used to modulate the laser light. In this case, the configuration of the optical system may be changed in accordance with the change in the method of the display element.
　また、上記実施形態および変更例１～３では、画像表示装置１が、表示素子により変調されたレーザ光を投射する方式の画像表示装置であったが、表示素子により生成された画像をそのまま見る方式の画像表示装置であってもよい。また、光源１１～１３は、必ずしもレーザ光源でなくてもよい、ＬＥＤ（Light Emitting Diode）等の他の方式の光源であってもよい。 In addition, in the above-described embodiment and modified examples 1 to 3, the image display device 1 is an image display device that projects a laser beam modulated by a display element. It may be an image display device of the system. Also, the light sources 11 to 13 are not necessarily laser light sources, and may be other types of light sources such as LEDs (Light Emitting Diodes).
　この他、本発明の実施形態は、特許請求の範囲に示された技術的思想の範囲内において、適宜、種々の変更が可能である。 In addition, the embodiments of the present invention can be appropriately modified in various ways within the scope of the technical ideas indicated in the claims.
　１　画像表示装置
　１１、１２、１３　光源
　２０　照明光学系
　３０　表示素子
　６０　光検出器
　７０　温度センサ
　１０１　制御部
　１０１ａ　デューティテーブル（情報）
　１０１ｂ　出力テーブル（情報）
　２００　光源制御回路 Reference Signs List 1 image display device 11, 12, 13 light source 20 illumination optical system 30 display element 60 photodetector 70 temperature sensor 101 control unit 101a duty table (information)
101b Output table (information)
200 light source control circuit

Claims (11)

  1. 　光源と、
    　前記光源から出射された光を映像信号に基づき変調する表示素子と、
    　前記光源から出射された前記光を前記表示素子に導く照明光学系と、
    　表示画像の明るさに応じて前記光源のパルス発光のデューティおよび出力を制御する制御部と、を備え、
    　前記制御部は、
    　　前記デューティおよび前記出力の一方を前記明るさの変化に応じて最小値から最大値まで一方向に変化させ、
    　　前記デューティおよび前記出力の他方を、対応する前記明るさのガンマ補正値が得られるように変化させる、
    ことを特徴とする画像表示装置。
          a light source;
    a display element that modulates the light emitted from the light source based on a video signal;
    an illumination optical system that guides the light emitted from the light source to the display element;
    a control unit that controls the duty and output of pulsed light emission of the light source according to the brightness of the display image,
    The control unit
    changing one of the duty and the output in one direction from a minimum value to a maximum value according to the change in brightness;
    Varying the other of the duty and the output so as to obtain a corresponding gamma correction value of the brightness;
    An image display device characterized by:
  2. 　請求項１に記載の画像表示装置において、
    　前記制御部は、前記ガンマ補正値の最小値から最大値までの変化傾向と同様の変化傾向で、前記デューティおよび前記出力の一方をその最小値から最大値まで変化させる、
    ことを特徴とする画像表示装置。
          The image display device according to claim 1,
    The control unit changes one of the duty and the output from the minimum value to the maximum value with the same change tendency as the change tendency from the minimum value to the maximum value of the gamma correction value.
    An image display device characterized by:
  3. 　請求項２に記載の画像表示装置において、
    　前記制御部は、前記ガンマ補正値の最小値から最大値までの変化と相関性を有するように、前記デューティおよび前記出力の一方をその最小値から最大値まで変化させる、
    ことを特徴とする画像表示装置。
          In the image display device according to claim 2,
    The control unit changes one of the duty and the output from the minimum value to the maximum value so as to have correlation with the change from the minimum value to the maximum value of the gamma correction value.
    An image display device characterized by:
  4. 　請求項２または３に記載の画像表示装置において、
    　前記制御部は、前記ガンマ補正値の最大値で前記ガンマ補正値を規格化したときの前記各明るさに対応する規格化ガンマ補正値をＬγとし、規格化ガンマ補正値の最小値および最大値をそれぞれＬγｍｉｎおよびＬγｍａｘとし、前記出力の最大値で前記出力を規格化したときの前記各明るさに対応する規格化出力値をＰｗとし、前記規格化出力値の最小値および最大値をそれぞれＰｗｍｉｎおよびＰｗｍａｘとしたとき、前記各明るさに対応する前記規格化出力値Ｐｗが以下の式を満たす、
    ことを特徴とする画像表示装置。
    Figure JPOXMLDOC01-appb-M000001
         In the image display device according to claim 2 or 3,
    The control unit defines Lγ as a normalized gamma correction value corresponding to each brightness when the gamma correction value is normalized by the maximum value of the gamma correction value, and the minimum and maximum values of the normalized gamma correction value. are respectively Lγmin and Lγmax, the normalized output value corresponding to each brightness when the output is normalized by the maximum value of the output is Pw, and the minimum and maximum values of the normalized output value are Pwmin and Pwmax, the normalized output value Pw corresponding to each brightness satisfies the following formula,
    An image display device characterized by:
    Figure JPOXMLDOC01-appb-M000001
  5. 　請求項２または３に記載の画像表示装置において、
    　前記制御部は、前記ガンマ補正値の最大値で前記ガンマ補正値を規格化したときの前記各明るさに対応する規格化ガンマ補正値をＬγとし、規格化ガンマ補正値の最小値および最大値をそれぞれＬγｍｉｎおよびＬγｍａｘとし、前記デューティの最大値で前記デューティを規格化したときの前記各明るさに対応する規格化デューティ値をＤとし、前記規格化デューティ値の最小値および最大値をそれぞれＤｍｉｎおよびＤｍａｘとしたとき、前記各明るさに対応する前記規格化デューティ値Ｄが以下の式を満たす、
    ことを特徴とする画像表示装置。
    Figure JPOXMLDOC01-appb-M000002
         In the image display device according to claim 2 or 3,
    The control unit defines Lγ as a normalized gamma correction value corresponding to each brightness when the gamma correction value is normalized by the maximum value of the gamma correction value, and the minimum and maximum values of the normalized gamma correction value. are respectively Lγmin and Lγmax, the normalized duty value corresponding to each brightness when the duty is normalized by the maximum value of the duty is D, and the minimum and maximum values of the normalized duty value are Dmin and Dmax, the normalized duty value D corresponding to each brightness satisfies the following formula,
    An image display device characterized by:
    Figure JPOXMLDOC01-appb-M000002
  6. 　請求項１ないし５の何れか一項に記載の画像表示装置において、
    　各明るさの前記デューティの値を前記デューティの最大値で規格化した規格化デューティ値と、各明るさの前記出力の値を前記出力の最大値で規格化した規格化出力値との乗算値が、各明るさの前記ガンマ補正値を前記ガンマ補正値の最大値で規格化した規格化ガンマ補正値となっている、
    ことを特徴とする画像表示装置。
          In the image display device according to any one of claims 1 to 5,
    A product of a normalized duty value obtained by normalizing the duty value of each brightness by the maximum duty value and a normalized output value obtained by normalizing the output value of each brightness by the maximum output value. is a normalized gamma correction value obtained by normalizing the gamma correction value of each brightness by the maximum value of the gamma correction value,
    An image display device characterized by:
  7. 　請求項１ないし６の何れか一項に記載の画像表示装置において、
    　前記制御部は、前記明るさの値に前記デューティおよび前記出力の値を対応づけた情報を保持し、前記情報に基づいて、設定対象の前記明るさの値に対する前記デューティおよび前記出力の値を取得する、
    ことを特徴とする画像表示装置。
          The image display device according to any one of claims 1 to 6,
    The control unit holds information in which the duty and the output value are associated with the brightness value, and based on the information, determines the duty and the output value for the brightness value to be set. get,
    An image display device characterized by:
  8. 　請求項７に記載の画像表示装置において、
    　前記光源付近の温度を検出する温度センサを備え、
    　前記制御部は、複数の温度に対してそれぞれ前記情報を保持し、前記温度センサによって検出された温度に対応する前記情報を用いて、設定対象の前記明るさの値に対する前記デューティおよび前記出力の値を取得する、
    ことを特徴とする画像表示装置。
          In the image display device according to claim 7,
    A temperature sensor that detects the temperature near the light source,
    The control unit holds the information for each of a plurality of temperatures, and uses the information corresponding to the temperature detected by the temperature sensor to determine the duty and the output for the brightness value to be set. get the value,
    An image display device characterized by:
  9. 　請求項１ないし８の何れか一項に記載の画像表示装置において、
    　前記光源の出射光量を検出するための光検出器を備え、
    　前記制御部は、前記光検出器を介して検出した前記出射光量と、設定対象の前記明るさに対応する基準光量との差分が抑制されるように、前記デューティおよび前記出力の少なくとも一方を補正する、
    ことを特徴とする画像表示装置。
          The image display device according to any one of claims 1 to 8,
    A photodetector for detecting the amount of light emitted from the light source,
    The control unit corrects at least one of the duty and the output so that a difference between the emitted light amount detected through the photodetector and a reference light amount corresponding to the brightness to be set is suppressed. do,
    An image display device characterized by:
  10. 　請求項１ないし９の何れか一項に記載の画像表示装置において、
    　出射波長が互いに異なる複数の前記光源を備え、
    　前記制御部は、前記光源ごとに前記制御を行う、
    ことを特徴とする画像表示装置。
          In the image display device according to any one of claims 1 to 9,
    comprising a plurality of light sources having different emission wavelengths;
    The control unit performs the control for each light source,
    An image display device characterized by:
  11. 　画像表示装置の光源を制御する光源制御回路であって、
    　表示画像の明るさに応じて前記光源のパルス発光のデューティおよび出力を制御する制御処理において、
    　　前記デューティおよび前記出力の一方を前記明るさの変化に応じて最小値から最大値まで一方向に変化させ、
    　　前記デューティおよび前記出力の他方を、対応する前記明るさのガンマ補正値が得られるように変化させる、
    ことを特徴とする光源制御回路。

          A light source control circuit for controlling a light source of an image display device,
    In the control process for controlling the duty and output of pulsed light emission of the light source according to the brightness of the display image,
    changing one of the duty and the output in one direction from a minimum value to a maximum value according to the change in brightness;
    Varying the other of the duty and the output so as to obtain a corresponding gamma correction value of the brightness;
    A light source control circuit characterized by:
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