JP2010243809A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device capable of displaying bright images while securing safety. <P>SOLUTION: The image display device includes: a laser beam source device; a modulator for modulating light emitted from the laser beam source device matched with an effective display period T<SB>1</SB>shorter than a reference display period T<SB>0</SB>determined by a refresh rate of input images; and a scanning optical system for scanning the light modulated by the modulator on a surface to be scanned matched with the effective display period T<SB>1</SB>. The output P<SB>1</SB>of the light emitted from the scanning optical system is set on the basis of the ratio between the reference display period T<SB>0</SB>and the effective display period T<SB>1</SB>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image display device.

  2. Description of the Related Art Conventionally, a scanning projector is known as one of image display apparatuses capable of displaying a large screen (for example, Patent Document 1). A scanning projector displays an image by raster-scanning modulated laser light on a surface to be scanned. According to the scanning projector, complete black can be expressed by stopping the supply of laser light. Therefore, the contrast can be remarkably increased as compared with a projector using a liquid crystal light valve. In addition, since laser light has a single wavelength, it has high color purity and high coherence, so that it is easy to shape the beam. As described above, the scanning projector is expected as an image display device that realizes high contrast, high color reproducibility, and high resolution.

    Further, the scanning projector can be remarkably reduced in size because a projection lens is not required and gradation adjustment can be performed by a modulation circuit instead of a liquid crystal light valve or the like. As a specific application of a small projector, for example, a use of enlarging display by incorporating or externally attaching a small projector in a mobile phone, a personal digital assistant (PDA), or the like can be considered. In a portable electronic device, the display unit is small from the viewpoint of improving portability, but the display can be enlarged by a small projector for easy viewing. This makes it possible to easily view the same image by a plurality of people.

  By the way, a safety standard (class) is provided for an apparatus that emits laser light. In the projector, the output of the laser beam is set so that the light (image) diffused by the screen or the like and indirectly incident on the pupil does not cause a safety problem. Further, the output of the laser light is set in consideration of the case where the laser light is directly incident on the pupil, for example, by looking into the laser light emitting portion. Since small projectors are expected to be used by a wide range of age groups, it is preferable that the output conforms to the safest level class (for example, international standard IEC-60825 Amd.2 Class I). It is done.

  The amount of light of the portable laser light source device can be set to several tens to several hundreds of lumens. However, in the conventional scanning projector, when the laser light output is set so as to satisfy Class I, the upper limit value of the light amount of the laser light is about 10 lumens. In order to display a good image with such a light amount, the diagonal of the screen is about several inches under the outdoor light condition, and the diagonal of the screen is about several ten inches under the outdoor light condition. Thus, it is difficult for a portable projector to make full use of convenience from the viewpoint of safety.

  As a technique for enabling display of a high-luminance image while ensuring safety, a technique disclosed in Patent Document 2 is conceivable. In Patent Document 2, a detection mechanism is provided that detects the presence or absence of an object in the emission light path from the laser light emission part to the screen. When an object is detected by the detection mechanism, the amount of laser light is adjusted.

JP-A-1-245780 Japanese Patent Laying-Open No. 2005-31530

  According to the technique of Patent Document 2, when there is no person in the emission optical path, the output of the laser light can be set to be higher than the safety standard for direct light and lower than the safety standard for indirect light. Seems to be displayable. However, it is difficult to actually perform the light amount adjustment favorably for the following reason.

  Even when a person is present in the emission optical path, it is considered that the light amount adjustment is unnecessary when the person is turning his back to the emission unit or when an object other than a person exists in the emission optical path. If the light amount adjustment is performed when the light amount adjustment is unnecessary, it becomes impossible to display an image satisfactorily. On the other hand, in order to accurately detect the presence of a person, the detection mechanism becomes complicated, and there are disadvantages such as an increase in cost and a decrease in portability. If it is determined with high accuracy whether it is a person or not, the processing time required for the determination becomes long, and there is a possibility that the adjustment of the light amount of the laser light may not be in time.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide an image display device capable of displaying a bright image while ensuring safety.

  An image display device of the present invention includes a laser light source device, and a modulation device that modulates light emitted from the laser light source device in alignment with an effective display period shorter than a reference display period determined by a refresh rate of an input image. A scanning optical system that scans a surface to be scanned in alignment with the light that is modulated by the modulation device, and the output of the light emitted from the scanning optical system is the reference display period It is set based on the ratio of the effective display period to.

  The longer the period during which light enters the human pupil and the higher the output of light incident on the pupil, the more energy the pupil receives per unit time. According to the above, the light emitted from the laser light source is modulated in alignment with the effective display period, and the modulated light is scanned in alignment with the effective display period. Therefore, the period in which an image of one frame is displayed is an effective display period that is shorter than the reference display period, and even when light emitted from the image display device is directly incident on the pupil, The period during which light is directly incident on becomes shorter, and the amount of energy received by the pupil per unit time is reduced. Therefore, the output of light emitted from the scanning optical system can be increased by the amount of energy received by the pupil, and the displayed image is viewed brighter than the physical luminance by the Broca-Sulzer effect. As described above, the image display device of the present invention can display a bright image while ensuring safety.

  In addition, the scanning optical system includes a main scanning mirror that scans light modulated by the modulation device in a main scanning direction in which pixels included in the input image are sequentially displayed and arranged in time. A detection unit that detects a refresh rate of an image; and a setting unit that sets an effective refresh rate that defines the effective display period based on a detection result of the detection unit, wherein the main scanning mirror includes the effective refresh rate. The modulation device may be configured to adjust the output of the light emitted from the laser light source device based on the ratio of the effective refresh rate to the refresh rate.

  In this way, the detection unit detects the refresh rate of the input image, and the setting unit sets the effective refresh rate. Since the modulation device adjusts the output of the light emitted from the laser light source device based on the ratio of the effective refresh rate to the refresh rate, the output of the light emitted from the laser light source device according to the refresh rate of the input image is Adjusted. As a result, the amount of energy received by the pupil per unit time is reduced, and a bright image can be displayed while ensuring safety.

  In addition, the effective display period is less than half of the reference display period, and between the period for displaying the current frame of the input image and the period for displaying the next frame of the input image, It may be configured to include a period for displaying the current frame or the next frame of the input image.

  In this way, the input image of the current frame or the next frame is displayed between the display period of the current frame and the display period of the next frame. Therefore, the physical brightness is increased and a bright image can be displayed.

  In addition, the effective display period is less than half of the reference display period, and between the period for displaying the current frame of the input image and the period for displaying the next frame of the input image, It may be configured to include a period for displaying an intermediate frame image determined by the current frame and the next frame of the input image.

  In this way, an intermediate frame image is displayed between the current frame display period and the next frame display period. Therefore, the physical brightness is increased and a bright image can be displayed. Further, an interpolated image between the current frame and the previous frame can be displayed as an intermediate frame image, and a high-quality image can be displayed.

  The image display system includes a plurality of image display systems including the laser light source device, the modulation device, and the scanning optical system, and the input image is displayed by being divided into a plurality of divided images, and each of the plurality of divided images is displayed. Displayed by each of the plurality of image display systems, and the plurality of lights so that the plurality of lights emitted from the plurality of image display systems do not simultaneously enter an inspection region determined by safety standards. The interval may be adjusted.

  In this way, since a plurality of lights emitted from a plurality of image display systems do not enter the inspection region at the same time, it is only necessary to satisfy safety standards with light emitted from one image display system, thereby ensuring safety. It becomes easy. Further, since the input image is displayed by a plurality of image display systems, it becomes easy to shorten the effective display period with respect to the reference display period, and the effective optical display period is emitted from the scanning optical system by the reduced amount. The light output can be increased.

If the number of the plurality of divided images is n and the scanning frequency of the input image is f, the scanning optical system may be driven at a frequency higher than f / n.
In this way, the amount of light in the entire image display system is increased as compared with the case where the image display system is one system, and a bright image can be displayed.

It is a schematic diagram which shows schematic structure of the projector which concerns on 1st Embodiment. (A) is explanatory drawing of an image display method, (b) is a top view of an example of an image, (c), (d) is explanatory drawing which shows the time change of the output of an emitted light. (A) is explanatory drawing which shows the positional relationship when light injects into a pupil directly, (b), (c) is explanatory drawing which shows the time change of the output of the incident light to a pupil. (A) is a schematic diagram showing an image signal processing system of the second embodiment, (b) is an explanatory diagram showing a temporal change in the output of the emitted light, and (c) shows a temporal change in the output of the incident light to the pupil. It is explanatory drawing. It is a schematic diagram which shows schematic structure of the projector which concerns on 3rd Embodiment. It is a schematic diagram which shows the positional relationship of the emitted light in 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings used for explanation, in order to show characteristic parts in an easy-to-understand manner, dimensions and scales of structures in the drawings may be different from actual structures. In addition, in the embodiment, the same components are illustrated with the same reference numerals, and detailed description thereof may be omitted.

[First Embodiment]
FIG. 1 is a schematic diagram illustrating a schematic configuration of the projector 1 according to the first embodiment of the present invention, FIG. 2A is an explanatory diagram illustrating a mechanism for displaying an image by the projector 1, and FIG. FIGS. 2C and 2D are explanatory views showing temporal changes in the output of light emitted from the projector 1. FIG.

  As shown in FIG. 1, the projector 1 includes an image signal processing system 10, a laser light source device 11, a relay optical system 12, and a scanning optical system 13. The projector 1 generally operates as follows.

  When an electrical signal corresponding to the input image is supplied from a signal source 8 such as a PC, the electrical signal is processed by the image signal processing system 10 and output to the laser light source device 11 and the scanning optical system 13. The laser light source device 11 emits light L whose gradation changes with time in accordance with an electrical signal. The light L enters the scanning optical system 13 via the relay optical system 12. The light L incident on the scanning optical system 13 is emitted by the scanning optical system 13 toward the surface to be scanned 9 such as a wall or a screen.

  The scanning optical system 13 temporally changes the optical axis of the emitted light L in the main scanning direction and the sub-scanning direction according to the electric signal. The main scanning direction is a direction in which pixels are drawn continuously in time, for example, a horizontal direction on the surface 9 to be scanned. The sub-scanning direction is a direction in which a plurality of pixel groups (scanning lines) drawn continuously in time are arranged, for example, a vertical direction orthogonal to the horizontal direction on the scanned surface 9. As the light L scans the scanned surface 9 in this way, an image is drawn (displayed) on the scanned surface 9. The projector 1 can be switched between a normal display mode and a high luminance display mode. Hereinafter, the components of the projector 1 will be described in detail.

  The image signal processing system 10 includes an interface (detection unit) 101, an image signal processing circuit 102, a modulation circuit (modulation device) 103, a timing generation circuit (setting unit) 104, and a mirror drive circuit 105. The interface 101 receives an electrical signal including an image signal and a synchronization signal from the signal source 8 and separates the electrical signal into an image signal and a synchronization signal. The image signal includes gradation data for each pixel of the input image. The synchronization signal includes data such as the number of pixels of the input image and the refresh rate. The separated image signal is output to the image signal processing circuit 102. The separated synchronization signal is output to the timing generation circuit 104.

  The timing generation circuit 104 generates a timing signal indicating the display timing for each pixel according to the number of pixels of the input image, the refresh rate, the scanning method, and the like. With the timing signal, the image signal can be converted into a format that matches the scanning method of the projector 1. The timing generation circuit 104 sets an effective refresh rate that is higher in frequency than the fresh rate of the input image in the high luminance display mode. The timing generation circuit 104 generates a timing signal so that a displayed image is rewritten at an effective refresh rate. The timing signal is output to the image signal processing circuit 102 and the mirror driving circuit 105.

  Here, it is assumed that the input image is in XGA format and the number of pixels is 1024 × 768. The direction in which 1024 pixels are arranged is set as the main scanning direction, and the frame rate is 60 frames per second (60 fps). Further, it is assumed that the scanning method draws an image in both of the scanning in the forward path from one side to the other in the main scanning direction (forward path) and the scanning in the backward path from the other side to the other.

  Under such conditions, the refresh rate is 60 Hz, and the display period (reference display period) of one frame corresponding to the refresh rate is 1/60 second. The timing generation circuit 104 generates a timing signal using, for example, a frequency (120 Hz) twice the refresh rate as an effective refresh rate. The display period (effective display period) for one frame corresponding to the effective refresh rate is 1/120 seconds.

  The image signal processing circuit 102 performs various image processing such as gamma processing on the image signal. Further, the image signal processing circuit 102 adjusts the image signal based on the timing signal so that the gradation data included in the image signal is output to the modulation circuit 103 in a time sequential manner matching the scanning method. For example, gradation data is stored in a frame buffer for a plurality of pixels included in one frame of the input image, and the gradation data is read sequentially in scanning time and output to the modulation circuit 103. As described above, when an image is drawn by forward scanning and backward scanning, for example, the order of reading data from the frame buffer is reversed between the forward scanning and the backward scanning.

  The modulation circuit 103 adjusts the output of the laser light source device 11 based on the image signal so that the light amount of the light L emitted from the laser light source device 11 changes with time according to the gradation for each pixel. In the high luminance display mode, the timing signal is generated so that the displayed image is rewritten at the effective refresh rate, and the modulation circuit 103 performs output adjustment so that one frame is displayed in the effective display period. Here, since the number of pixels is 1024 × 768 and the effective refresh rate is 120 Hz, the frequency of output adjustment is about 94.4 MHz when simply calculated while ignoring the blanking time. The reciprocal of this frequency corresponds to the drawing time per pixel.

  Also, the modulation circuit 103 adjusts the output of the laser light source device 11 as follows according to the ratio N (120/60 = 2 in this case) of the effective refresh rate to the refresh rate. An output when an image is displayed at a refresh rate is referred to as a reference output, and an output when an image is displayed at an effective refresh rate is referred to as an effective output. The modulation circuit 103 adjusts the output of the laser light source device 11 to the effective output by setting the product of the coefficient set within the range of greater than 1 and less than or equal to the ratio N (here 2) and the reference output as the effective output. Here, the coefficient is set to 2, and the output is adjusted so that the effective output is twice the reference output.

  Although the detailed configuration of the laser light source device 11 is not shown, the laser light source device 11 includes a plurality of semiconductor laser elements having different wavelengths of emitted light. The modulation circuit 103 adjusts the output for each of the plurality of semiconductor laser elements. Light emitted from the plurality of semiconductor laser elements is synthesized by a color synthesis element such as a dichroic mirror, and the synthesized light L is emitted from the laser light source device 11.

  The relay optical system 12 includes a collimating optical system 121 and a condensing optical system 122. The light L emitted from the laser light source device 11 is collimated by the collimating optical system 121 and then condensed by the condensing optical system 122. The relay optical system 12 can be changed as appropriate according to the light distribution characteristics of the laser light source device 11 and the like. For example, when the parallelism of the light emitted from the light source device is extremely high, the relay optical system 12 can be simplified or omitted. In addition, the relay optical system 12 may be provided with a function (beam shaping function) for adjusting the cross-sectional shape and size of the light beam in a plane orthogonal to the optical axis of the light emitted from the light source.

  The mirror drive circuit 105 generates drive signals for the first deflection mirror 131 and the second deflection mirror 132 based on the timing signal, and outputs the drive signals to the scanning optical system 13. Here, since the number of scanning lines is 768 and the effective refresh rate is 120 Hz, the scanning time per scanning line is 1/92160 seconds when simply calculated while ignoring the blanking time. Since the forward scanning and the backward scanning correspond to one scanning line, the scanning frequency in the main scanning direction is about 46,080 Hz.

  The scanning optical system 13 includes a first deflection mirror (main scanning mirror) 131 that changes the optical axis of incident light in the main scanning direction, and a second deflection mirror 132 that changes the optical axis of incident light in the sub-scanning direction. It is out. The first deflection mirror 131 is configured by a micro mechanical mirror formed by MEMS technology or the like, and the second deflection mirror 132 is configured by a galvano mirror or the like.

  The first deflection mirror 131 is driven by a mirror driving unit (not shown). The mirror drive unit receives the drive amount from the mirror drive circuit 105, and rotates the first deflection mirror 131 around the predetermined rotation axis at an angular velocity and amplitude corresponding to the drive amount. Here, the mirror driving unit drives the first deflection mirror 131 at a scanning frequency (46080 Hz) in the main scanning direction. As a result, the normal direction of the surface on which light enters in the first deflection mirror 131 changes with respect to the optical axis of the incident light L, and the optical axis of light reflected by this surface changes based on the timing signal. . The second deflection mirror 132 is driven by the mirror driving unit in the same manner as the first deflection mirror 131.

As shown in FIG. 2A, the light emitted from the scanning optical system 13 changes in gradation corresponding to each position from the pixel P (0,0) to the pixel P (i, 0). scanning the screen in the main scanning direction, to draw the first scan line SL _0. When the drawing of the first scan line SL ₀ is completed, after the scanning position in the sub-scanning direction are shifted to a position corresponding to the second scan line SL _1, the second scan lines SL along the main scanning direction ₁ Draw. Similarly, drawing of scanning lines in the main scanning direction and shifting of the position in the sub-scanning direction are alternately repeated, so that addresses 0 to i (here i = 1023) and addresses 0 to j (here j = 767) is drawn, and an image is displayed.

  For example, when an image as shown in FIG. 2B is displayed, the output of the laser light source device 11 is changed over time as shown in FIGS. 2C and 2D. Note that FIG. 2C illustrates an output when an image is displayed in the normal display mode, and FIG. 2D illustrates an output when an image is displayed in the high luminance display mode. .

The image shown in FIG. 2B is a gradation-like image in which the outline is substantially rectangular and the brightness increases from one corner (upper left in the figure) toward the opposite corner (lower right in the figure). To draw an image, to gradually increase the output in the period for drawing the first scan line SL _0. In the period in which the first scanning line SL ₀ and the second scanning line SL ₁ whose drawing direction is reversed are drawn, the output is gradually lowered.

As shown in FIG. 2C, when the image is displayed at the refresh rate (normal display mode), the maximum value of the reference output is P ₀ and the reference display period required for displaying one frame is T ₀ . As shown in FIG. 2D, the maximum value of the effective output when displaying an image at the effective refresh rate (high brightness display mode) is P ₁ , and the effective display period required for displaying one frame is T ₁ . To do. Since the effective refresh rate is set to twice the refresh rate, T ₁ becomes 1/2 of T ₀ . Each effective output corresponding to the scanning lines SL _{0 to} SL _j is twice the reference output, and P ₁ is twice P ₀ .

  An ordinary projector displays an image at a refresh rate, and the output of the laser light source device is set to a predetermined safety reference value. The safety standard value is, for example, the international standard IEC-60825 Amd. 2 Value specified for Class I. The output of the laser light source device set in this way is the reference output in the normal display mode.

  In the projector 1 of the present embodiment, since the effective output is twice the reference output, the displayed image is viewed brighter than the physical luminance due to the Broca-Sulzer effect. In addition, since the image is displayed at an effective refresh rate higher than the refresh rate, the output of light emitted from the projector 1 satisfies the safety standard. Hereinafter, safety when a person enters the scanning range of light emitted from the projector 1 will be described.

  FIG. 3A is an explanatory diagram showing a positional relationship when light is directly incident on the human pupil from the projector, and FIG. 3B is an output time of the direct light incident on the human pupil in the normal display mode. FIG. 3C is an explanatory diagram showing a change in the output of the direct light incident on the human pupil in the high luminance display mode.

  When the image displayed on the scanned surface 9 is viewed, the light incident on the human pupil is indirect light scattered on the scanned surface 9 so that indirect light does not cause a safety problem. The output of the laser light source device 11 is adjusted. As shown in FIG. 3A, when a person enters between the projector 1 and the surface to be scanned 9, light may directly enter the pupil E of the person M. Even in such a case, it is necessary to adjust the output of the laser light source device 11 so as not to cause a safety problem.

  International Standard IEC-60825 Amd. 2 Class I is the class with the highest safety, and is applied to, for example, toys. In order to be classified into class I, the energy of a single pulse does not exceed a predetermined upper limit (condition 1), the average energy of all pulses does not exceed a predetermined upper limit (condition 2), continuous It is necessary to satisfy all three conditions that the energy determined by the number of pulses to be performed does not exceed a predetermined upper limit (condition 3).

The pulse here is a series of light incident on a predetermined inspection region. In the projector 1, the number of pulses becomes 1 when one scanning line passes through the inspection region. The predetermined examination area is an area corresponding to the pupil E of the person M. International Standard IEC-60825 Amd. 2 Class predetermined inspection region in the I, the emitting portion of the laser beam, i.e. the diameter d ₂ distance d ₁ from the second deflecting mirror 132 of the projector 1 is in the plane of 10cm is defined in the region inside the circle of 7mm ing. In the projector 1, the laser light emission portion corresponds to the second deflection mirror 132.

  The number of pulses is determined by the number of scanning lines included in the range R in which the light emitted from the projector 1 scans within the pupil E. The energy of the single pulse is determined by the product of the output of the laser light emitted from the projector 1 and the time for scanning the inspection region with the laser light (the width of the single pulse). Single pulse width is the inverse proportion of the scanning frequency.

  The state in which the amount of energy of the laser light incident on the pupil E of the person M is the largest is when all the scanning lines overlapping the pupil E have the maximum luminance (maximum output). In this case, the temporal change in the output of the light incident on the pupil E becomes a rectangular wave as shown in FIGS. In the high luminance display mode, since the scanning frequency is doubled compared to the normal display mode, the single pulse width is halved, and the output of the single pulse is doubled. Thus, the energy of a single pulse in the high luminance display mode is the same as in the normal display mode. That is, in the high luminance display mode, the condition 1 is satisfied as in the normal display mode. Further, since drawing is performed at a double effective refresh rate, drawing of an image of one frame is completed in a period approximately half of the reference display period. As a result, approximately half of the reference display period becomes extra, but since no image is displayed during this extra period, the number of pulses and average energy are the same as in the normal display mode. Therefore, the conditions 2 and 3 are satisfied, and all the conditions 1 to 3 are satisfied.

  As described above, the projector 1 according to the present embodiment is capable of displaying a bright image while ensuring safety. In addition, a sensor or the like is unnecessary and a simple configuration can be achieved as compared with a method of detecting entry of an object in a scanning range of light emitted from a projector.

[Second Embodiment]
Next, a projector according to a second embodiment of the invention will be described. The second embodiment is different from the first embodiment in that an image is displayed during a period between frames in the high luminance display mode.

  FIG. 4A is a schematic diagram showing a schematic configuration of the image signal processing system 20 in the projector of the second embodiment, and FIG. 4B is a time change of the output of light emitted from the projector in the high luminance display mode. FIG. 4C is an explanatory diagram illustrating a change in the output of the direct light incident on the pupil in the high luminance display mode.

As shown in FIG. 4A, the image signal processing system 20 is different from the image signal processing system 10 of the first embodiment in that an image memory 201 is included. The image signal processing circuit 102 stores an image signal of one frame (current frame) in the image memory 201 in the high luminance display mode. Further, after the current frame of the input image is displayed, the image signal processing circuit 102 reads the image signal of the current frame from the image memory 201 and outputs it again to the modulation circuit 103. For example, when the image shown in FIG. 2B is displayed, the output pattern corresponding to the effective display period (T ₁ ) is included in the reference display period (T ₀ ) as shown in FIG. 4B. Light is emitted twice from the projector. Incidentally, when displaying the current frame twice sets the maximum value P ₂ of the effective output below 2 ^-0.25 times the maximum value P ₀ of the reference output.

As shown in FIG. 4C, when all the scanning lines overlapping the pupil E (see FIG. 3A) have the maximum brightness, the pulse of direct light incident on the pupil E is continuous with the pupil E. Since it is an area, it is concentrated in a part of the effective display period. In each of the two effective display periods, the period in which the pulses are densely coincides with each other in the two effective display periods. That is, the two pulse group are separated by a time interval substantially coincides with T _1. In such a case, in order to satisfy the above condition 3, when the number of continuous pulses is n, the upper limit of the energy of a single pulse may be set to n− ^0.25 . Here, since the number of pulses is doubled, the output of a single pulse may be reduced to ^2-0.25 (0.84) times or less. Thereby, all of conditions 1-3 will be satisfied and safety can be secured. Further, since the current frame is displayed twice, the total amount of light during the display of the current frame is about 1.68 times.
As described above, the projector according to the second embodiment can increase the physical luminance, and thus can display a bright image while ensuring safety.

  In the second embodiment, the current frame of the input image is continuously displayed. However, the next frame may be continuously displayed after the current frame is displayed, for example, by prefetching the input image. Further, an intermediate frame image signal may be generated based on the current frame image signal and the next frame image signal, and the intermediate frame may be displayed between the current frame display period and the next frame display period. In this case, for example, an image signal processing circuit may be provided with a function of performing an interpolation process, and an intermediate frame image signal may be generated by the interpolation process.

[Third Embodiment]
Next, a projector according to a third embodiment of the invention will be described. The third embodiment is different from the first embodiment in that an input image is shared by a plurality of image display systems and an image is displayed.

  FIG. 5 is a schematic diagram illustrating a schematic configuration of the projector 3 according to the third embodiment, and FIG. 6 is a schematic diagram illustrating a positional relationship of light emitted from the projector 3. As shown in FIG. 5, the projector 3 includes an image signal processing system 30, laser light source devices 31a and 31b, and scanning optical systems 33a and 33b. The laser light source devices 31a and 31b are both the same as the laser light source device 11 of the first embodiment.

  Also in the present embodiment, as in the first embodiment, it is assumed that the input image is in XGA format and the refresh rate is 60 Hz. The timing generation circuit 104 sets the refresh rate in the normal display mode to 60 Hz and generates a timing signal. Based on this timing signal, the mirror drive circuit 105 generates a drive signal, and the scanning optical systems 33a and 33b are driven by the drive signal. The timing generation circuit 104 sets the effective refresh rate in the high luminance display mode to 120 Hz and generates a timing signal.

  The modulation circuit 303 of the image signal processing system 30 includes a modulation unit (modulation device) that modulates the light La emitted from the laser light source device 31a and a modulation unit (modulation device) that modulates the light Lb emitted from the laser light source device 31b. ). The modulation circuit 303 adjusts the maximum output of light emitted from the laser light source devices 31a and 31b to ½ of the reference output in the first embodiment in the normal display mode. The modulation circuit 303 adjusts the maximum output of light emitted from the laser light source devices 31a and 31b to twice that in the normal display mode in the high luminance display mode. The laser light source devices 31a and 31b are both the same as the laser light source device 11 of the first embodiment.

  Each of the scanning optical systems 33a and 33b has a biaxial structure. The scanning optical system 33a includes a scanning mirror, a first frame that holds the scanning mirror so as to be rotatable about a first axis, a second frame that holds the frame so as to be rotatable about a second axis, and a second frame. And a third frame for holding the frame. The first axis is orthogonal to the second axis in the axial direction. By rotating the scanning mirror about the first axis, the light incident on the scanning mirror can be scanned in the sub-scanning direction. By rotating the first frame around the second axis, the light incident on the scanning mirror can be scanned in the main scanning direction.

  Lights La and Lb emitted from the laser light source devices 31a and 31b scan the surface 9 to be scanned by the scanning optical systems 33a and 33b. The scanning range of the light La is independent of the scanning range of the light Lb, and the entire image is displayed in a region combining the two scanning ranges. The scanning range of the light La is aligned with the scanning range of the light Lb in the sub-scanning direction.

As shown in FIG. 6, the arrangement of the laser light source devices 31a and 31b and the scanning optics are set so that the scanning ranges of the light La and Lb emitted from the scanning optical systems 33a and 33b are not applied to a predetermined inspection area A. The arrangement of the systems 33a and 33b is adjusted. The inspection area A is an area defined by safety standards. As described above, the international standard IEC-60825 Amd. In 2 Class I, the inspection region A, a scanning optical system 33a, the distance _{d 1} from 33b is a diameter _{d 2} in the plane of 10cm are defined in the region inside the circle of 7 mm.

  In this embodiment, when it is assumed that both the light La and Lb are incident on the portion where the scanning range of the light La is close to the scanning range of the light Lb, the light La and Lb are not incident on the inspection region A at the same time. Yes. In the present embodiment, the direction in which the optical axis of the light La changes in the sub-scanning direction matches the direction in which the optical axis of the light Lb changes in the sub-scanning direction. Therefore, in practice, the light La and Lb are not scanned so as to approach each other, and the interval between the light La and Lb in the plane including the inspection region A has a sufficient margin with respect to the diameter of the inspection region A. Have.

  In the projector 3 as described above, both the scanning ranges of the light La and Lb are not applied to the inspection area A. Therefore, even when a person enters between the projector 3 and the surface 9 to be scanned. Both the light La and Lb do not enter the human pupil. That is, it is only necessary that the light La and Lb emitted from each of the laser light source devices 31a and 31b satisfy the safety standards independently. Focusing on the light La, the output in the high luminance display mode is twice that in the normal display mode, and the display period by the light La is halved. Therefore, for the same reason as in the first embodiment, a bright image can be displayed while ensuring safety.

  In addition, the entire image is displayed by being shared by the two image display systems, and the number of scan lines assigned to each of the two image display systems is halved, so a predetermined number of scan lines are drawn during the reference display period. The scanning frequency to be lowered is lowered. Therefore, it becomes easier to increase the refresh rate in the high luminance display mode than in the normal display mode. In short, if the scanning frequency is the same as that for displaying an image in one image display system, the scanning frequency in the high-brightness display mode can be doubled that in the normal display mode. As described above, in the projector 3 according to the third embodiment, it is possible to display a bright image while ensuring safety, though the apparatus configuration is easy to realize.

  The technical scope of the present invention is not limited to the above embodiment. Various modifications are possible without departing from the gist of the present invention. For example, in the first embodiment, the projector capable of switching between the normal display mode and the high brightness display mode has been described. However, the projector may be operated only in the high brightness display mode.

  In the present embodiment, the effective refresh rate in the high luminance display mode is set to 120 Hz, but it should be higher than 30 Hz, which is 1/2 of 60 Hz. That is, it is only necessary that the scanning frequency of the scanning optical system is greater than f / n, where n is the number of divided images that share the image display and f is the horizontal scanning frequency of the input image. Thus, by emitting light from a plurality of image display systems, the amount of light emitted from the entire image display system can be increased compared to a case where the image display system is one system.

DESCRIPTION OF SYMBOLS 1, 3 ... Projector, 11, 31a, 31b ... Laser light source device, 13, 33a, 33b ... Scanning optical system, 101 ... Interface (detection part), 102 ... Image signal processing circuit , 103,303 ... modulation circuit (modulation unit), 104 ... timing generator (setting unit), 9 ... scanned _{surface, T} 0 ... reference display _{period, T} 1 ... effective display period

Claims (6)

A laser light source device;
A modulation device that modulates light emitted from the laser light source device in alignment with an effective display period shorter than a reference display period determined by a refresh rate of an input image;
A scanning optical system that scans the surface to be scanned in alignment with the light that is modulated by the modulation device in the effective display period,
The image display apparatus characterized in that an output of light emitted from the scanning optical system is set based on a ratio of the effective display period to the reference display period. The scanning optical system includes a main scanning mirror that scans the light modulated by the modulation device in a main scanning direction in which pixels included in the input image are continuously displayed and arranged in time.
A detection unit for detecting a refresh rate of the input image;
A setting unit that sets an effective refresh rate that defines the effective display period based on a detection result of the detection unit;
The main scanning mirror is driven based on the effective refresh rate;
The image display device according to claim 1, wherein the modulation device adjusts an output of light emitted from the laser light source device based on a ratio of the effective refresh rate to the refresh rate.   The effective display period is less than half of the reference display period, and the current frame of the input image is between a period for displaying the current frame of the input image and a period for displaying the next frame of the input image. The image display device according to claim 1, further comprising a period for displaying a next frame of the input image.   The effective display period is less than half of the reference display period, and the current frame of the input image is between a period for displaying the current frame of the input image and a period for displaying the next frame of the input image. 3. The image display device according to claim 1, further comprising a period during which an image of an intermediate frame determined by the next frame of the input image is displayed. A plurality of image display systems including the laser light source device, the modulation device, and the scanning optical system are included, the input image is divided into a plurality of divided images and displayed, and each of the plurality of divided images is the plurality of divided images. Are displayed by each of the image display systems of
The interval between the plurality of lights is adjusted so that the plurality of lights emitted from the plurality of image display systems do not enter the inspection region determined by safety standards at the same time. The image display apparatus as described in any one.   6. The image according to claim 5, wherein the scanning optical system is driven at a frequency higher than f / n, where n is the number of the plurality of divided images and f is the scanning frequency of the input image. Display device.

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