JP2011075958A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device in which a low gradation level is accurately and easily reproduced even when a laser having a kink area in its input/output characteristic is used. <P>SOLUTION: The image display device 1 includes: a light source part 2 which emits laser light having an intensity corresponding to a driving signal 7 including an image signal; a scanning part 3 in which two-dimensional scanning is performed with the laser light emitted from the light source part 2; and a light detection part 10 which is disposed at the position where the laser light for detecting timing and emitted from the light source part 2, when the scanning timing of the scanning part 3 is detected and scanned with the scanning part 3, is made incident. The light source part 2 includes a signal producing part 6 which produces a driving signal 7 and a signal adjustment part 8 which superimposes a high frequency signal 9 upon the driving signal 7 input to the laser 5. When the signal production part 6 outputs the driving signal 7 for emitting the laser light for detecting timing, the signal adjustment part 8 stops the superimposing of the high frequency signal 9 upon the driving signal 7. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image display device. Specifically, the present invention relates to an image display device including a laser that emits laser light having an intensity corresponding to a drive signal including an image signal.

  2. Description of the Related Art Conventionally, there is known a scanning type image display device that emits laser light whose intensity is modulated according to an image signal, scans the laser light in a two-dimensional direction by a scanning unit, and projects the image onto a projection target to display an image. It has been. As this type of image display device, for example, a retinal scanning image display device in which a projection target is a user's retina and a screen scanning image display device in which a projection target is a screen are known.

  In this type of scanning image display apparatus, it is necessary to perform scanning by the scanning unit at a high speed. For example, a deflecting element that changes the direction of laser light such as a galvanometer mirror is used. The deflecting element is operated by inputting a driving signal. However, if the deflecting element is to be deflected at a high speed, the response to the driving signal is deteriorated and the deflection operation is delayed. Since this delay varies depending on individual differences of deflection elements, the scanning position by the scanning unit cannot be accurately grasped. Further, there may be a case where it cannot be accurately grasped due to the noise of the drive signal or the operation noise of the deflection element.

  Therefore, in the conventional scanning image display device, the light detection unit is disposed at the position where the laser beam scanned by the scanning unit is incident, and the light detection unit is a light source unit based on the detection of the laser beam by the light detection unit. The emission timing of laser light from the laser is adjusted (see, for example, Patent Document 1).

  When an image displayed by the scanning image display device is a color image, a plurality of lasers having different wavelengths are required. In general, a scanning image display apparatus uses a red laser, a green laser, and a blue laser. By combining laser beams emitted from these lasers on the same optical path, the laser beams are synthesized to have various colors. Laser light is generated (see, for example, Patent Document 2).

JP 2008-233562 A JP 2003-295108 A

  However, some semiconductor lasers have regions where the input / output characteristics (current-light output characteristics) change sharply to cause bending and the linearity is lost. That is, it is desirable that the light output intensity increase / decrease with respect to the current increase / decrease is continuous from the first area to the second area where the light output intensity increase / decrease is steep, but between the first area and the second area. In some cases, there is a third region in which the increase or decrease in the light output intensity is more steep than the second region. This region is called a kink. This kink region appears particularly prominently in green lasers and blue lasers.

  Due to such a kink region, if a pixel signal assigned a gradation level on the premise of linearity is output to the semiconductor laser, gradation collapse occurs at a low gradation level.

  For this reason, when a semiconductor laser is used, it is necessary to assign pixel signals of each gradation level according to the kink region, and it is difficult to perform the assignment process, and a low gradation level cannot be accurately reproduced.

  The present invention has been made in view of the above-described problems, and it is easy to accurately reproduce a low gradation level even when a laser having a kink region in input / output characteristics is used. An object is to provide an image display device.

  To achieve the above object, the invention according to claim 1 is a two-dimensional scan of a light source unit that emits laser light having an intensity corresponding to a drive signal including an image signal, and a laser beam emitted from the light source unit. A scanning unit; a projection unit that projects laser light emitted from the light source unit during image formation and scanned in an effective scanning range by the scanning unit; and the light source unit that detects scanning timing of the scanning unit. From the light source unit based on the detection timing of the timing detection laser beam by the light detection unit, and the light detection unit arranged at the position where the timing detection laser beam emitted from and scanned by the scanning unit is incident A control unit that controls the emission timing of the laser beam, and the light source unit generates a signal generating unit that generates the drive signal, and a laser beam having an intensity corresponding to the drive signal. And a signal adjustment unit that superimposes a high-frequency signal having a frequency equal to or higher than the reciprocal of the period of the drive signal on the drive signal input to the laser, and the signal adjustment unit includes: When the signal generation unit outputs a drive signal for emitting the timing detection laser beam, the image display apparatus is characterized in that the superposition of the high-frequency signal on the drive signal is stopped.

  According to a second aspect of the present invention, in the image display device according to the first aspect, when the signal adjustment unit shifts the scanning range of the scanning unit from the effective scanning range to outside the effective scanning range, The superposition of the high-frequency signal on the drive signal is stopped, and the superposition of the high-frequency signal on the drive signal is started after the detection of the timing detection laser beam by the light detection unit.

  According to a third aspect of the present invention, in the image display device according to the first or second aspect, the scanning unit includes a first scanning unit that scans the laser light at a relatively high speed in the first direction. A second scanning unit that scans the laser light relatively slowly in a second direction orthogonal to the first direction, and the light detection unit emits from the light source unit during image formation. Immediately after the laser beam to be scanned is scanned in the first direction and is outside the effective scanning range in the first direction, the laser beam for timing detection emitted from the light source unit is disposed at a position where the laser beam is incident. It is characterized by that.

  According to a fourth aspect of the present invention, in the image display device according to the first or second aspect, the scanning unit includes a first scanning unit that scans the laser light at a relatively high speed in the first direction. A second scanning unit that scans the laser light relatively slowly in a second direction orthogonal to the first direction, and the light detection unit emits from the light source unit during image formation. Immediately after the laser beam to be scanned is scanned in the second direction and is outside the effective scanning range in the second direction, the timing detection laser beam emitted from the light source unit is disposed at a position where the laser beam is incident. It is characterized by that.

  The invention according to claim 5 is the image display device according to any one of claims 1 to 4, wherein the signal adjustment unit includes a high-frequency signal generation unit that generates the high-frequency signal, and the signal adjustment unit. And a switch that controls the superposition of the high-frequency signal from the signal adjustment unit to the signal generation unit, and controls the switch to control the high-frequency signal. It is characterized by controlling the stop and start of superimposition of.

  According to the present invention, since the high frequency signal is superimposed on the drive signal, the steep change occurring in the kink region can be changed into a gentle change. Therefore, even with a laser having a kink region in the input / output characteristics, it becomes easy to accurately reproduce a low gradation level. In addition, when the scanning timing of the scanning unit is detected, the superposition of the high-frequency signal on the drive signal is stopped, so that the scanning timing of the scanning unit can be reliably detected.

It is a figure which shows schematic structure of the image display apparatus in one Embodiment of this invention. It is a figure of the scanning range by the scanning part shown in FIG. It is a figure which shows the input / output characteristic of a semiconductor laser. It is a figure for demonstrating the input-output characteristic at the time of superimposing a high frequency signal on a drive signal. It is a figure for demonstrating the input-output characteristic at the time of superimposing a high frequency signal on a drive signal. It is a figure for demonstrating the output from the photon detection part at the time of superimposing a high frequency signal on a drive signal. It is a figure which shows the superimposition timing to the drive signal of a high frequency signal. It is a figure for demonstrating the output from the photon detection part at the time of superimposing a high frequency signal on a drive signal. It is a figure which shows the electrical structure and optical structure of a retinal scanning-type image display apparatus. It is a figure of the scanning range by the scanning part shown in FIG. It is a figure which shows the structure of the light source part shown in FIG. It is a figure which shows the flow of a process of the retinal scanning image display apparatus shown in FIG. It is a figure which shows the data structure of a gradation table. It is explanatory drawing of arrangement | positioning of another photon detection part. It is a figure which shows the superimposition timing to the drive signal of a high frequency signal when a photon detection part is arrange | positioned in the position shown in FIG. It is explanatory drawing of arrangement | positioning of another photon detection part. It is a figure which shows the superimposition timing to the drive signal of a high frequency signal when a photon detection part is arrange | positioned in the position shown in FIG. It is a figure which shows the structure of another light source part. It is a figure for demonstrating the input-output characteristic at the time of superimposing a high frequency signal on a drive signal.

  Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[1. Outline Configuration of Image Display Device 1]
As shown in FIG. 1, the image display device 1 includes a light source unit 2 that emits laser light having an intensity according to a drive signal including an image signal, and scanning that two-dimensionally scans the laser light emitted from the light source unit 2. A unit 3, a projection unit 4 that projects laser light scanned by the scanning unit 3 onto a projection target, a light detection unit 10, and a control unit 11 are provided.

  The light source unit 2 includes a signal generation unit 6 that generates a drive signal 7 and a laser 5 that emits laser light having an intensity corresponding to the drive signal 7 input from the signal generation unit 6. The signal generation unit 6 generates a drive signal 7 such as a pixel signal 7 a which is a pixel unit signal and a timing detection signal 7 b described later, and inputs the drive signal 7 to the laser 5. As a result, laser light whose intensity is modulated in accordance with the drive signal 7 is sequentially emitted from the laser 5. This laser 5 is a semiconductor laser such as a laser diode. Note that the image display device 1 uses a red laser, a green laser, and a blue laser, and is provided with a signal generation unit 6. However, in FIG. 1, only the green laser is illustrated for convenience of explanation. The laser 5 will be described.

  The scanning unit 3 performs two-dimensional scanning with the laser light emitted from the light source unit 2. FIG. 2 shows the relationship between the maximum scanning range G and the effective scanning range Z by the light source unit 2. Here, the “maximum scanning range G” means the maximum range in which the scanning unit 3 can scan the laser beam. In the maximum scanning range G, laser light whose intensity is modulated according to the pixel signal 7a is emitted from the light source unit 2 at a timing when the scanning position of the scanning unit 3 is in the effective scanning range Z. As a result, the laser light whose intensity is modulated according to the pixel signal 7a is scanned in the effective scanning range Z by the scanning unit 3, and the laser light for one frame is scanned. This scanning is repeated for each frame image. FIG. 2 virtually shows the locus γ of the laser beam scanned by the scanning unit 3 when it is assumed that the laser beam is always emitted from the light source unit 2. In FIG. 2, the X direction is the main scanning direction, and the Y direction is the sub-scanning direction. In the present embodiment, the main scanning direction is the horizontal direction and the sub-scanning direction is the vertical scanning direction, but the reverse is also possible.

  In the image display device 1 according to the present embodiment, a light detection unit 10 is provided to detect the scanning position of the scanning unit 3. The control unit 11 emits laser light for timing detection (hereinafter referred to as “timing detection laser light”) from the light source unit 2, and detects the laser light by the light detection unit 10, thereby causing the laser from the light source unit 2 to emit laser light. The timing for emitting light is adjusted. This is because if the scanning position of the scanning unit 3 is not known, it is impossible to emit laser light having an intensity corresponding to the pixel signal 7a in the effective scanning range Z in order to form an image. The control unit 11 controls the signal generation unit 6 of the light source unit 2 and outputs a timing detection signal 7b as a drive signal 7 from the signal generation unit 6 at a predetermined timing. This drive signal 7 is input to the laser 5, and a laser beam for timing detection is emitted from the laser 5.

  By the way, in the image display device 1, as shown in FIG. 3, as the laser 5, the input / output characteristics (current-light output characteristics) change sharply to cause bending and the kink region (kink) W where linearity is lost. A semiconductor laser is used. That is, the laser 5 includes the first region and the second region in addition to the first region in which the increase or decrease in the light output intensity is gradual and the second region in which the increase or decrease in the light output intensity is abrupt. Between the regions, there is a kink region W that is a third region in which the increase or decrease of the light output intensity is more steep than in the second region. Therefore, a low gradation level cannot be accurately reproduced with the pixel signal output from the signal generation unit 6 with a current value corresponding to the gradation level.

  Therefore, the light source unit 2 is provided with a signal adjustment unit 8 that superimposes the high-frequency signal 9 on the drive signal 7 input to the laser 5. When the high frequency signal 9 is superimposed on the drive signal 7 input to the laser 5, the intensity of the laser light emitted from the laser 5 varies according to the change in the amplitude of the high frequency signal 9. For example, it is assumed that a high frequency signal 9 having a current amplitude Ia is superimposed on a drive signal 7 having a current value Ib as shown in FIG. At this time, the current value of the current input to the laser 5 periodically increases and decreases between the current value I1 (= Ib−Ia / 2) and the current value I2 (= Ib + Ia / 2). Therefore, the intensity of the light emitted from the laser 5 also changes between the intensity values Y1 and Y2.

  The frequency of the high-frequency signal 9 to be superimposed on the drive signal 7 is a frequency (≧ 1 / T) that is equal to or greater than the reciprocal 1 / T of the generation period T of the drive signal 7 generated as a pixel signal 7a by the signal adjustment unit 8 as a pixel signal. ). The reciprocal 1 / T of the generation period T of the drive signal 7 corresponds to the frequency of a read clock signal for reading image data from a memory (not shown).

  As described above, when the high frequency signal 9 is superimposed on the drive signal 7, the intensity of the laser light emitted from the laser 5 varies according to the change in the amplitude of the high frequency signal 9. The brightness is a brightness corresponding to the intensity obtained by averaging the fluctuating intensity.

  Therefore, when the high-frequency signal 9 is superimposed on the drive signal 7, the input / output characteristics of the laser 5 can be regarded as characteristics whose intensity changes as shown by the solid line in FIG. Hereinafter, such input / output characteristics are referred to as apparent input / output characteristics. 5 indicates the input / output characteristics of the laser 5 when the high-frequency signal 9 is not superimposed on the drive signal 7.

  In the image display device 1 according to the present embodiment, the influence of the kink region W is suppressed by superimposing the high-frequency signal 9 on the drive signal 7, and the current value of the drive signal 7 and the intensity of the laser light approach a proportional relationship. I am doing so. By doing so, it becomes easy to assign the current value of the pixel signal to the low gradation level.

  However, when the high-frequency signal 9 is superimposed on the drive signal 7, the intensity of the timing detection laser light also varies depending on the frequency of the high-frequency signal 9, so that when the timing detection laser light is incident, the light detection unit 10. The detection signal output from may not be output. For example, as shown in FIG. 6, a detection signal is output when the timing detection laser beam is incident on the light detection unit 10 during the time t1 to t2, but the timing detection laser beam is output during the time t3 to t4. When the light enters the light detection unit 10, no detection signal is output. In addition, the light detection unit 10 can detect light with a time delay within a desired accuracy within a range of an appropriate amount of incident light. However, when the amount of incident light exceeds the range, the detection timing is shifted due to the influence of noise and the like. Therefore, when the amount of light incident on the light detection unit 10 is not appropriate as described above, if the detection signal output from the light detection unit 10 is used, a deviation occurs in the image formation timing, and the quality of the image to be formed is reduced. It will deteriorate. In particular, when reciprocating scanning is performed in the main scanning direction, the image formation timing during the forward pass and the image formation timing during the backward pass are shifted, resulting in double image formation.

  Therefore, when the timing detection signal 7 b is output from the signal generator 6 as the drive signal 7, the generation of the high-frequency signal 9 in the signal adjustment unit 8 is stopped so that the high-frequency signal 9 is not superimposed on the drive signal 7. ing. In this way, a detection signal is surely output from the light detection unit 10 on which the timing detection laser light is incident.

  Further, as shown in FIG. 7, the signal adjustment unit 8 stops the generation of the high-frequency signal 9 when the scanning range of the scanning unit 3 shifts from the effective scanning range Z to outside the effective scanning range Z (timing t11). Then, the superposition of the high frequency signal 9 on the drive signal 7 is stopped. Furthermore, after the detection of the timing detection laser beam by the light detection unit 10 (timing t13), the signal adjustment unit 8 resumes the generation of the high-frequency signal 9 and starts superimposing the high-frequency signal 9 on the drive signal 7. I have to. In this way, while reducing the power consumption due to the superposition of the high-frequency signal 9 on the drive signal 7, the drive signal 7 is reliably generated until the scanning range of the scanning unit 3 falls within the effective scanning range Z. The drive signal 7 can be superimposed on the high-frequency signal 9.

  As described above, in the image display apparatus 1 according to the present embodiment, the influence of the kink region W is suppressed by superimposing the high-frequency signal 9 on the drive signal 7, and the current value of the drive signal 7, the intensity of the laser light, Is approaching a proportional relationship. Therefore, it becomes easy to assign the current value of the drive signal 7 to the low gradation level. Therefore, it is easy to accurately reproduce a low gradation level even with a laser in which the kink region W exists in the input / output characteristics.

  In addition, when the scanning timing of the scanning unit 3 is detected, the superposition of the high-frequency signal 9 on the drive signal 7 is stopped, so that the scanning timing of the scanning unit 3 can be reliably detected. Therefore, the accuracy of the emission timing of the laser light from the light source unit 2 at the time of image formation can be improved, and deterioration in image quality such as jitter appearing in the image visually recognized by the user can be suppressed.

  In the image display device 1, the current amplitude of the high-frequency signal 9 to be superimposed on the drive signal 7 is equal to or greater than the width Ic of the kink region W. That is, it is necessary that the current range of the pixel signal 7 in which the high-frequency signal 9 is superimposed and the current value changes covers the range of the kink region W. This is because if the width of the high frequency signal is smaller than the width Ic of the kink region, a region W1 in which the influence of the kink region cannot be suppressed occurs as shown in FIG.

[2. Application example to retinal scanning image display device]
Hereinafter, a specific configuration and a specific operation when the image display device 1 is applied to a retinal scanning image display device (hereinafter referred to as “RSD”) will be described.

[2.1. Electrical configuration and optical configuration of RSD 100]
First, the electrical configuration and optical configuration of the RSD 100 will be described with reference to FIG.

  As illustrated in FIG. 9, the RSD 100 according to the present embodiment includes a light source unit 110, an optical fiber 120, a scanning unit 130, and a projection unit 140.

  The light source unit 110 includes a drive signal supply circuit 111, laser units 115r, 115g, and 115b, collimating optical systems 116r, 116g, and 116b, dichroic mirrors 117r, 117g, and 117b, and a coupling optical system 118.

  Based on the input image signal S, the drive signal supply circuit 111 generates pixel signals corresponding to the colors of the three primary colors that are elements for forming an image in units of pixels. That is, the drive signal supply circuit 111 generates and outputs R (red) drive signal 112r, G (green) drive signal 112g, and B (blue) drive signal 112b as image signals for each color. The drive signal supply circuit 111 generates and outputs a G (green) drive signal 112g as a timing detection signal. Further, the drive signal supply circuit 111 outputs a high-speed drive signal 116 used by the high-speed scanning unit 132 and a low-speed drive signal 117 used by the low-speed scanning unit 134, respectively. The drive signal supply circuit 111 outputs control signals 113g and 113b for controlling the amplitude of a high-frequency signal to be described later superimposed on the drive signals 112g and 112b.

  The R laser unit 115r, the G laser unit 115g, and the B laser unit 115b are laser beams whose intensity is modulated in accordance with the R drive signal 112r, the G drive signal 112g, and the B drive signal 112b output from the drive signal supply circuit 111, respectively. (Also referred to as “light flux”).

  The R (red) laser light Lr, G (green) laser light Lg, and B (blue) laser light Lb emitted from the laser units 115r, 115g, and 115b are collimated by collimating optical systems 116r, 116g, and 116b, respectively. Then, the light enters the dichroic mirrors 117r, 117g, and 117b. Thereafter, these dichroic mirrors 117r, 117g, and 117b reflect and transmit the laser beams of the three primary colors in a wavelength selective manner, reach the coupling optical system 118, and are combined and emitted to the optical fiber 120. Thus, the laser light emitted to the optical fiber 120 is the image light Lc, which is a combination of intensity-modulated laser light of each color.

  The scanning unit 130 includes a collimating optical system 131, a high-speed scanning unit 132, a first relay optical system 133, and a low-speed scanning unit 134.

  The collimating optical system 131 converts the laser light generated by the light source unit 110 and emitted through the optical fiber 120 into parallel light.

  The high-speed scanning unit 132 and the low-speed scanning unit 134 scan in the main scanning direction and the sub-scanning direction so that the laser light incident from the optical fiber 120 can be projected as an image onto the user's retina 101b. The high-speed scanning unit 132 reciprocally scans the incident laser light that has been collimated by the collimating optical system 131 in the main scanning direction for image display. The low-speed scanning unit 134 scans in the main scanning direction by the high-speed scanning unit 132, and scans the laser light incident via the first relay optical system 133 in the sub-scanning direction substantially orthogonal to the main scanning direction.

  The high-speed scanning unit 132 swings the reflection mirror 132b of the deflection element 132a by resonating the deflection element 132a having a reflection mirror 132b that scans laser light in the main scanning direction by swinging. A high-speed scanning drive circuit 132 c that generates a drive signal based on the high-speed drive signal 116 is provided. On the other hand, the low-speed scanning unit 134 forces the non-resonant deflecting element 134a having the reflecting mirror 134b that scans the laser beam in the sub-scanning direction by swinging, and the reflecting mirror 134b of the deflecting element 134a in a non-resonant state. And a low-speed scanning drive circuit 134c that generates a drive signal to be oscillated based on the low-speed drive signal 117. The low-speed scanning unit 134 scans laser light for forming an image in the sub-scanning direction from the first scanning line toward the last scanning line for each frame of the image to be displayed. Here, “scanning line” means one scanning in the main scanning direction by the high-speed scanning unit 132. Here, galvanometer mirrors are used as the deflecting elements 132a and 134a. However, as long as the reflecting mirrors 132b and 134b can be swung or rotated so as to scan the laser beam, piezoelectric driving and electromagnetic driving are possible. Any driving method such as electrostatic driving may be used.

  The first relay optical system 133 relays the laser light between the high-speed scanning unit 132 and the low-speed scanning unit 134, and reflects the laser light scanned in the main scanning direction by the reflection mirror 132b of the deflection element 132a to the reflection of the deflection element 134a. It converges on the mirror 134b. Then, this laser beam is scanned in the sub-scanning direction by the reflection mirror 134b of the deflection element 134a. Here, the horizontal direction of the image to be displayed is the main scanning direction and the vertical direction of the image to be displayed is the sub-scanning direction, but the main scanning direction may be the vertical direction and the sub-scanning direction may be the horizontal direction.

  The projection unit 140 includes a second relay optical system 135 and a half mirror 136. Laser light scanned by the deflecting element 134a is transmitted by a half mirror 136 positioned in front of the eye 101 via a second relay optical system 135 in which two lenses 135a and 135b having positive refractive power are arranged in series. It is reflected and enters the user's pupil 101a. Thereby, an image corresponding to the image signal S is projected on the retina 101b, and the user recognizes the laser light (image light Lc) incident on the pupil 101a as an image. Further, the half mirror 136 transmits the external light La so as to enter the user's pupil 101a, so that the user can visually recognize an image in which an image based on the image light Lc is superimposed on an external scene based on the external light La. Can do.

  In the second relay optical system 135, the respective laser beams are made substantially parallel to each other and converted into convergent laser beams by the lens 135a. The laser beams are converted into substantially parallel laser beams by the lens 135b, and the center lines of these laser beams are converted so as to converge on the user's pupil 101a.

  Further, the RSD 1 according to the present embodiment includes a light detection unit 141 in order to adjust the emission timing of the laser light from the light source unit 110. The light detection unit 141 includes a photodiode and an IV converter, and outputs a detection signal 143 when laser light is incident.

  FIG. 10 is a diagram similar to FIG. 2, and shows the relationship between the maximum scanning range G and the effective scanning range Z by the deflection elements 132 a and 134 a of the high-speed scanning unit 132 and the low-speed scanning unit 134. Here, the “maximum scanning range G” means the maximum range in which the deflecting elements 132a and 134a can scan the laser beam. In the maximum scanning range G, image light Lc, which is laser light whose intensity is modulated in accordance with the image signal S, is emitted from the light source unit 110 at a timing when the scanning position by the deflecting elements 132a and 134a is within the effective scanning range Z. 10 virtually shows a locus γ of the laser beam scanned by the deflection elements 132a and 134a when it is assumed that the laser beam is always emitted from the light source unit 110. However, the number of scanning lines in the main scanning direction by the deflecting element 132a is about several hundreds or thousands per frame. In FIG. 10, the locus γ of the laser beam is simply shown.

  The high-speed scanning drive circuit 132c amplifies the high-speed drive signal 116 to generate a drive signal, and the reflection mirror 132b of the deflection element 132a is swung by this drive signal. The low-speed scanning drive circuit 134c amplifies the low-speed drive signal 117 to generate a drive signal, and the reflection mirror 134b of the deflection element 134a is swung by this drive signal. However, the swing trajectories γ1 and γ2 (see FIG. 10) of the reflection mirrors 132b and 134b do not completely coincide with the signal waveforms of the drive signals 116 and 117, and a phase difference or the like occurs. In particular, the deflection element 132a needs to swing the reflection mirror 132b at a high speed, and since it is a resonance type deflection element, the phase difference from the signal waveform of the high-speed drive signal 116 becomes large.

  Therefore, in the RSD 1 according to the present embodiment, as shown in FIGS. 9 and 10, the light detection unit 141 is arranged to detect the scanning timing of the laser light by the reflection mirrors 132 b and 134 b. The drive signal supply circuit 111 adjusts the emission timing of the laser light from the light source unit 110 by causing the light detection unit 141 to detect the laser light emitted from the light source unit 110.

  The light detection unit 141 is disposed at a position where the timing detection laser beam scanned in the invalid scanning range N outside the effective scanning range Z in the maximum scanning range G is incident. A light blocking unit 142 is provided behind the light detection unit 141 in the invalid scanning range N in order to prevent laser light scanned outside the effective scanning range Z from entering the user's eye 101. For example, as illustrated in FIG. 9, the light shielding unit 142 uses a non-transmissive plate-like member having an opening through which a laser beam scanned in the effective scanning range Z of the maximum scanning range G passes. Further, the light shielding unit 142 is used as a fixing member for fixing the light detection unit 141. In the present embodiment, an intermediate image plane is formed by the lens 135a, and the light shielding portion 142 is disposed at the intermediate image plane position. In this way, the light shielding unit 142 can be reduced in size, and the laser beam detected by the light detection unit 141 is detected at the position where the beam diameter of the laser beam scanned by the scanning unit 130 is the smallest. Accuracy can be improved.

[2.1. Specific Configuration of Light Source Unit 110]
Next, a specific configuration of the light source unit 110, which is a characteristic part of the RSD 100 according to the present embodiment, will be further described with reference to FIG. As described above, the light source unit 110 includes the drive signal supply circuit 111 and the laser units 115r, 115g, and 115b.

  The drive signal supply circuit 111 includes a CPU 201, ROM 202, RAM 203, VRAM 204, D / A converters 205r, 205g, 205b, 208, 209, A / D converters 210, 211, output ports 206g, 206b, and the like. . These are respectively connected to a data communication bus 212, and various information is transmitted and received via the bus 212. In the drive signal supply circuit 111, the CPU 201 operates by executing a control program stored in the ROM 202, operates each part of the RSD 100, and executes various functions provided in the RSD 100. In addition to the control program described above, the ROM 202 stores, for example, a gradation table described later. When the CPU 201 executes a control program stored in the ROM 202, the drive signal supply circuit 111 includes a signal generation unit that generates a drive signal and a signal adjustment unit that superimposes a high-frequency signal on the drive signal input to the laser. Based on the detection timing of the timing detection laser beam by the light detection unit 141, it functions as a control unit that controls the emission timing of the laser beam from the light detection unit 141.

  The CPU 201 converts the image signal S input from the A / D converter 211 into image data composed of a plurality of pixel data, writes it in the VRAM 204, and develops it. This VRAM 204 is used as a frame buffer. Each pixel data stored in the VRAM 204 includes red component R pixel data, green component G pixel data, and blue component B pixel data. The CPU 201 sequentially reads out the R pixel data, G pixel data, and B pixel data developed in the VRAM 204 in units of pixels, converts them into analog signals by the D / A converters 205r, 205g, and 205b, and generates pixel signals. Are sequentially output as drive signals 112r, 112g, and 112b.

  Further, the CPU 201 outputs control signals 113g and 113b for controlling high-frequency oscillators 305g and 305b, which will be described later, superimposed on the drive signals 112g and 112b from the output ports 206g and 206b.

  Further, the CPU 201 converts the high-speed driving signal 116 used in the high-speed scanning unit 132 and the low-speed driving signal 117 used in the low-speed scanning unit 134 into analog signals by the D / A converters 208 and 209 and outputs the analog signals. Further, the CPU 201 inputs the detection signal 143 output from the light detection unit 141 via the A / D converter 210, and detects the scanning position of the scanning unit 130 based on the timing at which the detection signal 143 is input. Based on the detected scanning position of the scanning unit 130, the CPU 201 determines the emission timing of the laser light whose intensity is modulated according to the image signal S from the light source unit 110 and emits the laser light from the light source unit 110.

(R laser part 115r)
The R laser unit 115r includes an R laser driver 301r and an R laser diode 303r.

  The R laser driver 301r generates a drive signal 302r having a current value corresponding to the voltage value of the R drive signal 112r output from the drive signal supply circuit 111, and supplies the drive signal 302r to the R laser diode 303r.

  The R laser diode 303r emits red laser light having an intensity corresponding to the drive signal 302r. In other words, the R laser diode 303r emits red laser light having an intensity corresponding to the R drive signal 112r output from the drive signal supply circuit 111.

(G laser part 115g)
The G laser unit 115g includes a G laser driver 301g, a G laser diode 303g, a high frequency oscillator 305g, and a capacitor 307g.

  The G laser driver 301g generates a drive signal 302g having a current value corresponding to the voltage value of the G drive signal 112g output from the drive signal supply circuit 111, and supplies the drive signal 302g to the G laser diode 303g.

  The high frequency oscillator 305g generates and outputs a high frequency signal 306g having a current value with a predetermined amplitude. The output end of the high frequency oscillator 305g is connected between the G laser driver 301g and the G laser diode 303g via a capacitor 307g, and the high frequency signal 306g is superimposed on the drive signal 302g via the capacitor 307g. The high frequency oscillator 305g is ON / OFF controlled by a control signal 113g output from the drive signal supply circuit 111. That is, when the voltage value of the control signal 113g is a high level signal, the high frequency oscillator 305g performs an oscillation operation to generate and output the high frequency signal 306g. On the other hand, when the voltage value of the control signal 113g is a low level signal, the high frequency oscillator 305g stops the oscillation operation and stops generating the high frequency signal 306g.

  The frequency of the high-frequency signal 306g is the reciprocal 1 / Ts of the generation cycle Ts of the G drive signal 112g generated in pixel units as a pixel signal by the drive signal supply circuit 111 (the cycle in which the G drive signal 112g of one pixel is output). The above frequency. That is, the frequency of the high frequency signal 306g is set to be equal to or higher than the frequency of the read clock signal for reading image data from the VRAM 204. Thus, by setting the frequency fa of the high-frequency signal 306g to be equal to or higher than the frequency of the read clock signal, it is possible to accurately reproduce the characteristic that changes in intensity as shown by the solid line in FIG. However, since the reflection mirror 132b is swung by resonance vibration, the scanning speed is not constant. In this case, it is necessary to change the read clock signal of the image data in accordance with the scanning speed. In order to reduce the influence, it is desirable that the frequency of the high frequency signal 306g is as high as possible as compared with the frequency of the read clock signal. The frequency of the high-frequency signal 306g can be said to be a frequency exceeding twice the maximum frequency in the frequency band of the drive signal continuously output from the drive signal supply circuit 111. Usually, the read clock signal is set to a frequency exceeding twice this.

  The G laser diode 303g receives a current in which the high frequency signal 306g is superimposed on the drive signal 302g output from the G laser driver 301, and emits a green laser beam having an intensity corresponding to the current. For example, when the G laser diode 303g has the input / output characteristics shown in FIG. 3, the input / output characteristics of the G laser diode 303g change in intensity as shown by the solid line in FIG. 5 by superimposing the high frequency signal 306g on the drive signal 302g. It can be regarded as a characteristic.

(B laser unit 115b)
The B laser unit 115b includes a B laser driver 301b, a B laser diode 303b, a high frequency oscillator 305b, and a capacitor 307b.

  The B laser unit 115b has the same configuration as the G laser unit 115g. That is, the B laser driver 301b generates a drive signal 302b having a current value corresponding to the voltage value of the B drive signal 112b output from the drive signal supply circuit 111. On the other hand, the high frequency oscillator 305b generates and outputs a high frequency signal 306b having a current value with a predetermined amplitude. The high frequency oscillator 305b is connected to the B laser driver 301b via the capacitor 307b, and the high frequency signal 306b is superimposed on the drive signal 302b and supplied to the B laser diode 303b. For example, when the B laser diode 303b has the input / output characteristics shown in FIG. 3, the input / output characteristics of the B laser diode 303b change in intensity as shown by the solid line in FIG. 5 by superimposing the high frequency signal 306b on the drive signal 302b. It can be regarded as a characteristic. The high frequency oscillator 305b is controlled to start and stop its oscillation operation by a control signal 113g output from the drive signal supply circuit 111, similarly to the high frequency oscillator 305g.

  The frequency of the high-frequency signal 306b is a frequency equal to or higher than the reciprocal of the cycle in which the B drive signal 112b of one pixel is output, like the frequency fa of the high-frequency signal 306g. For example, when one B drive signal 112b is output in units of Tr (seconds), the frequency fb of the high-frequency signal 306b is set to 1 / Tr or higher. That is, the frequency fb of the high frequency signal 306b is set to a frequency equal to or higher than the frequency of the read clock signal for reading image data from the VRAM 204. However, since the reflection mirror 132b is swung by resonance vibration, the scanning speed is not constant. In this case, it is necessary to change the read clock signal of the image data in accordance with the scanning speed. In order to reduce the influence, it is desirable that the frequency of the high frequency signal 306b is as high as possible than the frequency of the read clock signal.

[2.2. Control processing of RSD 100]
A control process by the CPU 201 of the light source unit 110 configuring the RSD 100 configured as described above will be described with reference to FIG. The following processing by the CPU 201 is started by a power-on operation by pressing a power button (not shown) of the RSD 100, for example.

  First, when the power button is pressed by a user operation, the CPU 201 performs an initial setting process such as initializing the work area of the RAM 203 (step S10), and moves the process to step S11.

  In step S <b> 11, the CPU 201 reads the gradation table for each laser unit 115 r, 115 g, 115 b from the ROM 202 and stores it in the RAM 203. As shown in FIG. 12, the gradation table is a table in which each gradation level and the voltage levels of the drive signals 112r, 112g, and 112b are associated with each other. The gradation table for red, the gradation table for green, and the color for blue There is a gradation table.

  Next, the CPU 201 starts driving the scanning unit 130 (step S12). In this process, the CPU 201 first outputs a low-speed drive signal 117 so that the laser light reflected by the reflection mirror 134b of the low-speed scanning unit 134 enters the light detection unit 141, and the reflection mirror 134b of the low-speed scanning unit 134. Is changed (position Y shown in FIG. 10). Next, the CPU 201 outputs a sinusoidal high-speed drive signal 116 and starts swinging the reflection mirror 132b. Thereafter, the CPU 201 outputs a G drive signal 112g having a predetermined voltage value, and emits a laser beam having a predetermined intensity as a timing detection laser beam from the G laser diode 303g. The reflection mirror 132b scans the timing detection laser beam. At this time, the timing detection laser beam scanned by the reflection mirror 132 b passes through the light detection unit 141 and enters the light detection unit 141. The light detection unit 141 outputs the detection signal 143 at the timing when the timing detection laser light is incident. Based on this detection signal 143, the CPU 201 detects the scanning position in the main scanning direction by the deflection element 132a. Next, the CPU 201 stops the output of the G drive signal 112g, stops the emission of the timing detection laser light, outputs the sawtooth low-speed drive signal 117, and starts to swing the reflection mirror 134b. When the angle of the reflection mirror 134b of the low-speed scanning unit 134 is in the invalid scanning range N, even if light is emitted from the light source unit 110, the laser light output from the scanning unit 130 is shielded by the light shielding unit 142, and the user It does not enter the eye 101 of the eye.

  Next, the CPU 201 outputs control signals 113g and 113b having predetermined voltages, starts the oscillation operation of the high-frequency oscillators 305g and 305b, and starts superimposing the high-frequency signals 306g and 306b on the drive signals 302g and 302b (step S13). ), The process proceeds to step S14.

  In step S <b> 14, the CPU 201 determines whether an image formation period of one frame has started. That is, the CPU 201 determines whether or not the scanning position of the scanning unit 130 has reached the scanning start position z1 shown in FIG.

  If it is determined that the image forming period has not started (step S14: NO), the CPU 201 repeats the process of step S14. On the other hand, if it is determined that the image forming period has started (step S14: YES), the CPU 201 determines whether there is an input of the image signal S from the outside (step S15). In this processing, the CPU 201 determines that there is an input of the image signal S from the outside when the input of the image signal S is started from the outside or when the input of the image signal S is performed from the outside. If it is determined that the image signal S is input from the outside (step S15: YES), the CPU 201 generates a pixel signal and outputs it as the drive signals 112r, 112g, and 112b (step S16).

  In the process of step S16, the CPU 201 develops and stores the input image signal S in the VRAM 204 in units of pixels, and outputs an R drive signal 112r, a G drive signal 112g, and a B drive signal 112b in units of pixels. To do. At this time, the CPU 201 outputs drive signals 112r, 112g, and 112b based on the gradation table stored in the RAM 203. At this time, high frequency current is superimposed on the drive signals 302g and 302b via the capacitors 307g and 307b.

  When it is determined in the process of step S15 that there is no input of the image signal S from the outside (step S15: NO) and when the process of step S16 is completed, the CPU 201 determines whether or not the one-frame image formation period has ended. Is determined (step S17).

  If it is determined that the image forming period has not ended (step S17: NO), the CPU 201 repeats the processes of steps S15 and S16. On the other hand, if it is determined that the image forming period has ended (step S17: YES), the CPU 201 outputs control signals 113g and 113b of a predetermined voltage, stops the oscillation operation of the high-frequency oscillators 305g and 305b, and the high-frequency signal 306g. , 306b on the drive signals 302g, 302b is stopped (step S18), and the process proceeds to step S19.

  In step S19, the CPU 201 determines whether or not the scanning position detection timing has come. In this process, the CPU 201 determines that the scanning position detection timing has come when the angle of the reflection mirror 134b is the position of the light detection unit 141 (the position of Y shown in FIG. 10) or the position immediately before it in the sub-scanning direction. judge. That is, when the timing detection laser beam is emitted from the light source unit 110, the scanning position detection timing is reached when the timing detection laser beam reaches the position in the sub-scanning direction passing through the light detection unit 141 or the position immediately before the position. It is determined that

  If it is determined in step S19 that the scanning position detection timing has come (step S19: YES), the CPU 201 performs timing adjustment processing (step S20). In this timing adjustment process, the CPU 201 first outputs a G drive signal 112g having a predetermined voltage value, and emits a laser beam with a predetermined intensity from the G laser diode 303g as a timing detection laser beam for a predetermined period. At this time, the timing detection laser beam scanned by the reflection mirror 132 b passes through the light detection unit 141 and enters the light detection unit 141. The light detection unit 141 outputs the detection signal 143 at the timing when the timing detection laser light is incident. Based on the detection signal 143, the CPU 201 detects the scanning position in the main scanning direction by the deflecting element 132a and the scanning position in the sub-scanning direction by the deflecting element 134a, and emits laser light whose intensity is modulated according to the image signal S. Adjust timing. That is, the laser light whose intensity is modulated in accordance with the image signal S in the effective scanning range Z is emitted from the light source unit 110.

  When it is determined in step S19 that the scanning position detection timing has not been reached (step S19: NO) or when the processing of step S20 is completed, the CPU 201 outputs control signals 113g and 113b having predetermined voltages, and the high-frequency oscillator 305g, The oscillation operation of 305b is resumed to start superposition of the high frequency signals 306g, 306b on the drive signals 302g, 302b (step S21), and the process proceeds to step S22.

  In step S22, the CPU 201 determines whether or not the image display is stopped by pressing a power button or an image stop button (not shown). If it is determined that the image display is not stopped (step S22: No), the CPU 201 returns the process to step S14. On the other hand, when it is determined that the image display is stopped (step S22: Yes), the CPU 201 ends the process.

  As described above, in the RSD 100 according to the present embodiment, the influence of the kink region W is suppressed by superimposing high-frequency signals on the drive signals, respectively, and the current value of the drive signal and the intensity of the laser light approach a proportional relationship. I am doing so. Therefore, it becomes easy to assign the current value of the drive signal which is a pixel signal for a low gradation level. Therefore, it is easy to accurately reproduce a low gradation level even with a laser in which the kink region W exists in the input / output characteristics.

  In addition, when the scanning timing of the scanning unit 130 is detected, the superposition of the high-frequency signal on the drive signal is stopped, so that the scanning timing of the scanning unit can be reliably detected. Therefore, the accuracy of the emission timing of the laser light from the light source unit during image formation can be improved, and deterioration in image quality such as jitter appearing in the image visually recognized by the user can be suppressed.

  In the above embodiment, as shown in FIG. 10, the light detection unit 141 is arranged at the position where the laser beam is incident before the image formation of one frame in the maximum scanning range G by the scanning unit 130. It is not limited to.

  For example, as shown in FIG. 14, the laser light emitted from the light source unit 110 during image formation is emitted from the light source unit 110 immediately after being scanned in the sub scanning direction and outside the effective scanning range Z in the sub scanning direction. Alternatively, the light detection unit 141 ′ may be disposed at a position where the timing detection laser light is incident. In this case, as shown in FIG. 15, when the scanning range of the scanning unit 130 shifts from the effective scanning range Z in the sub-scanning direction to outside the effective scanning range Z (timing t21), the high-frequency signal 306g to the drive signal 112g Superposition is stopped, and after the detection of the timing detection laser beam by the light detection unit 141 ′ (timing t22), superposition of the high-frequency signal 306g on the drive signal 112g is started. Thereby, it is possible to increase the time until the high frequency signal 306g generated by the oscillation by the high frequency oscillator 305g is stabilized, and the image quality can be improved.

  Further, for example, as shown in FIG. 16, from the light source unit 110 immediately after the laser beam emitted from the light source unit 110 during image formation is scanned in the main scanning direction and outside the effective scanning range Z in the main scanning direction. The light detection unit 141 ″ may be arranged at a position where the emitted timing detection laser beam is incident. In this case, as shown in FIG. 17, the scanning range of the scanning unit 130 is effective scanning in the main scanning direction. When shifting from the range Z to outside the effective scanning range Z (timing t31), the superposition of the high-frequency signal 306g on the driving signal 112g is stopped, and after the detection of the timing detection laser beam by the light detection unit 141 ″ (timing t32) Then, superposition of the high-frequency signal 306g on the drive signal 112g is started. Thereby, it is possible to increase the time until the high frequency signal 306g generated by the oscillation by the high frequency oscillator 305g is stabilized, and the image quality can be improved.

  Further, in the above-described embodiment, the timing detection laser light is emitted from the laser diode 303g, but may be emitted from the laser diode 303b. Moreover, you may make it radiate | emit from two laser diodes 303g and 303b simultaneously. Further, the light may be emitted from the three laser diodes 303r, 303g, and 303b at the same time.

  In the above-described embodiment, the high-frequency signal is superimposed on the G drive signal 112g and the B drive signal 112b. However, when the R laser diode is a laser diode having a kink region as shown in FIG. By superimposing the high-frequency signal on the signal 112r, it becomes easy to accurately reproduce a low gradation level.

  In the above-described embodiment, the oscillation operations of the high-frequency oscillators 305g and 305b are controlled to be turned on / off by the control signals 112g and 112b output from the drive signal supply circuit 111. However, the oscillation of the high-frequency oscillators 305g and 305b is controlled. You may make it superimpose the high frequency signals 306g and 306b on the drive signals 302g and 302b using a switch, without turning ON / OFF operation | movement. For example, as shown in FIG. 18, variable capacitors 307g 'and 307b' are provided instead of the fixed capacitors 307g and 307b between the high frequency oscillators 305g and 305b and the laser drivers 301g and 301b. Then, control signals 113g 'and 113b' for controlling the capacitance values of the variable capacitors 307g 'and 307b' are output from the drive signal supply circuit 111. When stopping the superposition of the high-frequency signals 306g and 306b, the drive signal supply circuit 111 reduces the capacitance values of the variable capacitors 307g ′ and 307b ′ by the control signals 113g ′ and 113b ′ and superimposes the high-frequency signals 306g and 306b. In some cases, the capacitance values of the variable capacitors 307g ′ and 307b ′ are increased by the control signals 113g ′ and 113b ′. In this way, by using the variable capacitors 307g ′ and 307b ′ as switches, it is possible to execute and stop the superposition of the high-frequency signals 306g and 306b without turning on / off the oscillation operation of the high-frequency oscillators 305g and 305b. .

  In addition, an intensity detection unit that detects the intensity of the laser light emitted from the laser diodes 303r, 303g, and 303b is provided, and the drive signal supply circuit 111 assigns the gray level according to the detection result of the intensity detection unit. It can also be done. For example, it is input when the intensity of the laser light of the black level and the white level is set in advance and the intensity of the laser light emitted from each of the laser diodes 303r, 303g, and 303b becomes the intensity of the preset black level. The current values of the drive signals 112r, 112g, and 112b are black pixel signals. Further, the current values of the drive signals 112r, 112g, and 112b inputted when the intensity of the laser light emitted from each of the laser diodes 303r, 303g, and 303b reaches a preset white level intensity are used as the white level pixel signals. And Further, the pixel signal of each gradation level between the black level pixel signal and the white level pixel signal is assigned according to the apparent input / output characteristics. In this way, even when the input / output characteristics of the laser diodes 303g and 303b change due to a temperature change or even if there is an individual difference between the laser diodes 303g and 303b, it is possible to appropriately assign gradation levels. . In the intensity detection unit, laser light whose intensity varies depending on the high-frequency signal is incident. However, the intensity detection unit outputs a detection signal corresponding to the average intensity of the incident laser light.

  Further, in the case of the configuration shown in FIG. 18, the drive signal supply circuit 111 changes the voltage values of the control signals 113g ′ and 113b ′ in accordance with the current values of the drive signals 112g and 112b to change the amplitudes of the high-frequency signals 306g and 306b. To be able to change. In this way, the current values of the drive signals 112g and 112b and the intensity of the laser beam can be made closer to a proportional relationship. For example, for the laser having the input / output characteristics shown in FIG. 3, in the drive signal supply circuit 111, the current values of the drive signals 112g and 112b become the center of the kink region W as shown in FIG. The amplitudes of the high-frequency signals 306g and 306b to be superimposed are increased. On the other hand, the drive signal supply circuit 111 reduces the amplitude of the high-frequency signals 306g and 306b to be superimposed when the current values of the drive signals 112g and 112b pass the center of the kink region W.

  Although the present invention has been described through the above-described embodiments, the following effects can be expected according to this embodiment.

(1) Light source unit 2 (light source unit 110) that emits laser light having an intensity corresponding to drive signal 7 (drive signals 302r, 302g, and 302b) including an image signal and light source unit 2 (light source unit 110) The scanning unit 3 (scanning unit 130) for two-dimensionally scanning the laser beam and the light source unit 2 (light source unit 110) emitted during image formation and scanned by the scanning unit 3 (scanning unit 130) in the effective scanning range Z When detecting the scanning timing of the projection unit 4 (projection unit 140) that projects laser light onto the projection target and the scanning unit 3 (scanning unit 130), the light is emitted from the light source unit 2 (light source unit 110), and the scanning unit 3 (scanning). Detecting the timing detection laser beam by the light detection unit 10 (light detection unit 141) disposed at the position where the timing detection laser light scanned by the unit 130) enters and the light detection unit 10 (light detection unit 141) T Based on timing, and a light detector 10 the control unit 11 (drive signal supply circuit 111) which controls the emission timing of the laser light from (the light detecting unit 141). The light source unit 2 (light source unit 110) includes a signal generation unit 6 (drive signal supply circuit 111, laser drivers 301g and 301b) that generates a drive signal 7 (drive signals 302r, 302g, and 302b) and a drive signal 7 (drive signal). 302r, 302g, and 302b) a laser 5 (laser diodes 303r, 303g, and 303b) that emits laser light having an intensity corresponding to the laser beam, and a drive signal 7 (drive signal) that is input to the laser 5 (laser diodes 303g and 303b) as a pixel signal. 302g, 302b) is superimposed with a high frequency signal 9 (high frequency signals 306g, 306b) having a frequency equal to or higher than the reciprocal 1 / T (1 / Ts, 1 / Tb) of the period of the drive signal 7 (drive signals 302g, 302b). Signal adjustment unit 8 (drive signal supply circuit 111, high frequency oscillators 305g and 305b, capacitor 307g 307b), and the signal adjustment unit 8 (drive signal supply circuit 111, high-frequency oscillators 305g and 305b, capacitors 307g and 307b) is included in the signal generation unit 6 (drive signal supply circuit 111, laser drivers 301g and 301b). ) Is outputting a drive signal 7 (drive signals 302g, 302b) for emitting timing detection laser light, a high-frequency signal 9 (high-frequency signals 306g, 306b) to the drive signal 7 (drive signals 302g, 302b). ) Is stopped. In this way, by superimposing the high-frequency signal on the drive signal, the influence of the kink region W is suppressed, and the current value of the drive signal and the intensity of the laser beam are brought closer to a proportional relationship. Therefore, it becomes easy to assign the current value of the drive signal to the low gradation level. Therefore, it is easy to accurately reproduce a low gradation level even with a laser in which the kink region W exists in the input / output characteristics. In addition, when the scanning timing of the scanning unit is detected, the superposition of the high-frequency signal on the drive signal is stopped, so that the scanning timing of the scanning unit can be reliably detected. Therefore, the accuracy of the emission timing of the laser light from the light source unit during image formation can be improved, and deterioration in image quality such as jitter appearing in the image visually recognized by the user can be suppressed.

(2) The signal adjustment unit 8 (the drive signal supply circuit 111, the high-frequency oscillators 305g and 305b, the capacitors 307g and 307b) is configured so that the scanning range of the scanning unit 3 (scanning unit 130) is outside the effective scanning range Z from the effective scanning range Z. When the transition is made, the superposition of the high-frequency signal 9 (high-frequency signals 306g, 306b) on the drive signal 7 (drive signals 302g, 302b) is stopped, and the timing detection laser light by the light detection unit 10 (light detection unit 141) is stopped. After the detection, superposition of the high frequency signal 9 (high frequency signals 306g, 306b) on the drive signal 7 (drive signals 302g, 302b) is started. As described above, since the superposition of the high-frequency signal to the drive signal is started after the detection of the timing detection laser beam by the light detection unit, it takes a long time until the high-frequency signal generated by oscillation in the signal adjustment unit is stabilized. Image quality can be improved.

(3) The scanning unit 130 includes a high-speed scanning unit 132 (first scanning unit) that scans laser light at a relatively high speed in the main scanning direction (first direction), and a sub-scanning direction that is orthogonal to the main scanning direction. A low-speed scanning unit 134 (second scanning unit) that scans the laser light at a relatively low speed in the (second direction), and the light detection unit 141 ″ is emitted from the light source unit 110 during image formation. Immediately after the laser beam to be scanned in the main scanning direction is outside the effective scanning range Z in the main scanning direction, the signal is disposed at a position where the timing detection laser beam emitted from the light source unit 110 is incident. More time can be taken until the high-frequency signal generated by oscillation in the adjustment unit is stabilized, and the quality of the image can be improved.

(4) The scanning unit 130 includes a high-speed scanning unit 132 (first scanning unit) that scans laser light at a relatively high speed in the main scanning direction (first direction), and a sub-scanning direction that is orthogonal to the main scanning direction. A low-speed scanning unit 134 (second scanning unit) that scans the laser light at a relatively low speed in the (second direction), and the light detection unit 141 ′ is emitted from the light source unit 110 during image formation. Immediately after the laser beam to be scanned in the sub-scanning direction is outside the effective scanning range Z in the sub-scanning direction, the signal is disposed at the position where the timing detection laser beam emitted from the light source unit 110 is incident. More time can be taken until the high-frequency signal generated by oscillation in the adjustment unit is stabilized, and the quality of the image can be improved.

(5) As a signal adjustment unit, provided between the high frequency oscillators 305g and 305b (high frequency signal generation unit) for generating a high frequency signal and the high frequency oscillators 305g and 305b and the laser drivers 301g and 301b (signal generation unit), A high-frequency signal 306g from the oscillators 305g and 305b (high-frequency signal generation unit) to the signal generation unit 6 (laser drivers 301g and 301b). As switches for controlling the superimposition of 306b, variable capacitors 307g 'and 307b' are provided, and the high-frequency signal 306g is controlled by controlling the variable capacitors 307g 'and 307b'. Since the stop and start of superposition of 306b are controlled, it is not necessary for the signal adjustment unit to stop the oscillation operation for generating the high-frequency signal, and the image quality can be improved.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 2,110 Light source part 3,130 Scan part 4 Projection part 5 Laser 6 Signal generation part 7,112r, 112g, 112b, 302r, 302g, 302b Drive signal 8 Signal adjustment part 9,306g, 306b High frequency signal 10 , 141, 141 ′, 141 ″ Photodetection unit 11 Control unit 100 Retina scanning image display device (RSD)
111 Drive signal supply circuit (signal generation unit, signal adjustment unit, control unit)
303r, 303g, 303b Laser diode

Claims (5)

A light source unit that emits laser light having an intensity according to a drive signal including an image signal;
A scanning unit that two-dimensionally scans the laser light emitted from the light source unit;
A projection unit that projects laser light emitted from the light source unit during image formation and scanned in an effective scanning range by the scanning unit;
A light detection unit disposed at a position where a timing detection laser beam emitted from the light source unit and scanned by the scanning unit is incident when detecting the scanning timing of the scanning unit;
A control unit for controlling the emission timing of the laser beam from the light source unit based on the detection timing of the timing detection laser beam by the light detection unit,
The light source unit is
A signal generator for generating the drive signal;
A laser that emits laser light having an intensity according to the drive signal;
A signal adjustment unit that superimposes a high-frequency signal having a frequency equal to or higher than the reciprocal of the period of the drive signal on the drive signal input to the laser,
The signal adjustment unit stops superposition of the high-frequency signal on the drive signal when the signal generation unit outputs a drive signal for emitting the timing detection laser beam. Display device.   The signal adjustment unit stops superposition of the high-frequency signal on the drive signal when the scanning range of the scanning unit shifts from the effective scanning range to outside the effective scanning range, and the timing by the light detection unit The image display apparatus according to claim 1, wherein superposition of the high-frequency signal onto the drive signal is started after detection of the detection laser beam. The scanning unit scans the laser beam at a relatively high speed in a first direction, and the laser beam at a relatively low speed in a second direction orthogonal to the first direction. A second scanning section for scanning,
The light detection unit emits from the light source unit immediately after the laser light emitted from the light source unit during image formation is scanned in the first direction and is outside the effective scanning range in the first direction. The image display device according to claim 1, wherein the image display device is disposed at a position where the timing detection laser beam is incident. The scanning unit scans the laser beam at a relatively high speed in a first direction, and the laser beam at a relatively low speed in a second direction orthogonal to the first direction. A second scanning section for scanning,
The light detection unit emits from the light source unit immediately after the laser light emitted from the light source unit during image formation is scanned in the second direction and is outside the effective scanning range in the second direction. The image display device according to claim 1, wherein the image display device is disposed at a position where the timing detection laser beam is incident. The signal adjustment unit
A high-frequency signal generator for generating the high-frequency signal;
A switch that is provided between the signal adjustment unit and the signal generation unit and controls superposition of the high-frequency signal from the signal adjustment unit to the signal generation unit,
The image display apparatus according to claim 1, wherein the switch is controlled to control stop and start of superposition of the high-frequency signal.

Images