JP2012247534A - Electromagnetic wave scanning method, picture projection device and image acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic scanning method that can determine a frequency suitable for picture projection, and provide a picture projection device and an image acquisition device.SOLUTION: When an electromagnetic wave is scanned in a first deflection direction x and a second deflection direction y that are vibrating and independent, a deflection reflector 2 for changing the direction of the electromagnetic wave sets a first deflection frequency fat a value obtained by the expression, where the resolution in the second deflection direction is represented as Y and a frame rate at which the scanning of the entire scan area is completed is represented as F.

Description

  The present invention relates to an electromagnetic wave scanning method, an image projection apparatus, and an image acquisition apparatus that form a plane by electromagnetic waves (light beams) by scanning in two directions.

  As a beam scanning method for forming an information plane using a light beam by scanning the light beam in two directions, for example, there is a television projector for displaying an image. In this television projector, a spot-like luminescent spot of a light beam is scanned by a deflecting reflector to form an image as an information plane by the light beam on a screen.

  This deflection reflector has two first and second rotation axes that are substantially orthogonal to each other, and the angle of the deflection reflector can be changed by the first and second rotation axes. By changing the angle of the deflecting reflector around the first and second rotation axes, the direction of the reflected light changes and the position of the bright spot on the screen changes.

  In order to use this bright spot for video display, the light beam is raster-scanned by a deflecting reflector, and the light beam spot is moved back and forth so as to draw an image on the screen. A certain amount is moved.

  In general, in television, such screen drawing by raster scanning is required 60 times per second. For example, when the vertical resolution of the video is 480, the horizontal scanning frequency is 480 × 60 = 28,800, which is about 30 kHz. In addition, the deflecting reflector must be moved at high speed in order to avoid visually worrying about scanning the image.

  In order to realize such a high frequency vibration, a small reflector is formed by a semiconductor process. By making the reflector small and thin, the reflector can be designed to have a high natural vibration frequency. The incident light is modulated with the video signal in synchronization with the position of the reflector. The incident light is modulated independently, with the three colors red, blue, and green corresponding to the three color components of the video signal.

  This operation is basically the same as that of a CRT television. The cathode ray tube television changes the direction of the electron beam by using an electron beam instead of incident light and using a deflection coil instead of a deflecting reflector.

  When scanning the bright spot of the reflected light by this deflecting reflector, the scanning range greatly depends on the deflection angle of the reflector. If the distance from the position of the deflecting reflector to the position of the screen is the same, the projected image becomes larger as the reflector is swung at a larger angle.

  When a deflecting reflector is constituted by a mirror, it is necessary to reciprocally rotate the mirror by oscillating it in order to deflect and scan the light beam by the mirror. In the deflection scanning of the light beam by this mirror, in order to deflect the mirror at several tens of kilohertz, high-speed rotation is required for the rotation of the mirror, which is difficult to realize with a small motor.

  Therefore, when vibration is used, a small size can be realized, but scanning with linear motion or discontinuous motion becomes difficult. When this vibration is used, a large amplitude can be obtained with a small amount of energy by using resonance.

  For example, in scanning in which the reflector of the deflecting reflector is moved with a fundamental wave around two orthogonal first and second rotation axes, the trajectory of the scanning is performed based on a Lissajous figure (for example, see Patent Document 1). ).

  When performing such scanning, it is necessary to determine the frequency in the vertical direction and the horizontal direction. However, since scanning based on the Lissajous figure has a higher degree of freedom in frequency selection than scanning based on raster scanning, it is difficult to determine a frequency suitable for video projection.

  Further, in the scan using the Lissajous figure as in Patent Document 1, when the bright spot of the scan reciprocates once, the scan returns to the position shifted by 120 degrees in the x direction without returning to the starting point. Also, if the bright spot by scanning makes one reciprocation in y (vertical direction), the position of the bright spot by scanning shifts by 120 degrees, so if the bright spot by scanning makes three round trips, the bright spot by scanning rotates exactly 360 degrees. And return to the starting point.

  However, considering that the pixel is formed with a resolution of 20 × 20, for example, with this Lissajous figure, the deflection reflector has a pixel knob portion through which the scanning line does not pass no matter how many reciprocating scans. As in this example, scanning with a Lissajous figure tends to cause scanning unevenness. For this reason, in order to uniformly scan the rectangular area, the scanning resolution and scanning frequency must be selected appropriately.

  Therefore, an object of the present invention is to provide an electromagnetic wave scanning method, a video projection device, and an image acquisition device that can determine a frequency suitable for video projection.

In order to achieve this object, an electromagnetic wave scanning method, a video projection device, and an image acquisition device according to the present invention have a deflector that changes the direction of an electromagnetic wave, and the deflector has an independent first deflection direction x that vibrates. A space is two-dimensionally scanned by scanning an electromagnetic wave having a second deflection direction y and deflected by the deflector. Moreover, the resolution of the second deflection direction Y, when the scanning of the entire scanning area is the frame rate finish was F, a first deflection frequency f _x,
It is characterized by.

  According to such an electromagnetic wave scanning method, a video projection device, and an image acquisition device, the first deflection frequency can be determined from the resolution and the frame rate, so that the entire surface scanning can be completed at the designated frame rate. Design values for applications aiming at video projection are clear. Thereby, a frequency suitable for video projection can be determined.

It is explanatory drawing of the video projector which is a video projector using the electromagnetic wave scanning method concerning this invention. It is a schematic perspective view which shows the relationship between the deflection | deviation reflector shown in FIG. 1, and a screen. FIG. 3 is an enlarged explanatory diagram of the deflecting reflector shown in FIG. 2. FIG. 3 is an operation explanatory diagram of the deflecting reflector shown in FIG. 2. FIG. 2 is a control circuit diagram of the video projector shown in FIG. 1. FIG. 5 is a detailed circuit diagram of the output control unit shown in FIG. 4. It is explanatory drawing of the scanning by the image | video projector shown in FIG. It is explanatory drawing of the Lissajous figure and vibration which are used for the scanning of the video projector shown in FIG. It is vibration explanatory drawing by the Lissajous figure shown in FIG. It is explanatory drawing which shows the relationship between the scanning using the Lissajous figure shown in FIG. 7, and a pixel. It is scanning explanatory drawing using the Lissajous figure shown in FIG. It is explanatory drawing of the phase of x at the time of the scanning using the Lissajous figure shown in FIG. It is explanatory drawing for the phase rotation in the half period (time Ty / 2) of y vibration. It is a schematic perspective view which shows the other structure of the deflection | deviation reflector shown in FIG. It is a schematic explanatory drawing of the image acquisition apparatus using the electromagnetic wave scanning method which concerns on this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Constitution]
FIG. 1 shows an embodiment in which a scanning device for an electromagnetic wave scanning method according to the present invention is applied to a video projector (video projection device), and FIG. 2 shows a deflection scanner of the electromagnetic wave scanning device of FIG. It is the perspective view which showed an example.

In FIG. 1, reference numeral 1 denotes a semiconductor laser beam generator, and 2 denotes a deflecting reflector that deflects and scans a laser beam (electromagnetic wave) generated by the semiconductor laser beam generator 1.
<Semiconductor laser beam generator 1>
The semiconductor laser beam generator 1 generates a red laser diode LD-R that generates a red laser beam LbR (red component of a video signal) that is an electromagnetic wave and a green laser beam LbG (green component of a video signal) that is an electromagnetic wave. And a blue laser diode LD-B that generates a blue laser beam LbB (a blue component of a video signal) that is an electromagnetic wave.

  The semiconductor laser beam generator 1 also converts the red laser beam LbR generated from the red laser diode LD-R into a parallel light beam to prevent diffusion, and the green laser beam LbG generated from the green laser diode LD-G. The lens 4 has a parallel light beam for preventing diffusion, and the lens 5 has a blue laser beam LbB generated from the blue laser diode LD-B as a parallel light beam for preventing diffusion.

  Further, the semiconductor laser beam generator 1 includes a dichroic mirror 6 that synthesizes the green laser beam LbG generated from the green laser diode LD-G with the red laser beam LbR into one light, and a blue laser diode LD-. A dichroic mirror 7 is provided to synthesize the blue laser beam LbB generated from B so as to be combined with the red laser beam LbR and the green laser beam LbG.

The combined laser beam Lb combined by the dichroic mirrors 6 and 7 is scanned by the deflecting reflector 2 and projected onto the screen 8.
<Deflecting reflector 2>
In television, screen drawing is required 60 times per second. When the vertical resolution of the video is 480, for example, the horizontal scanning frequency is 480 × 60 = 28,800, which is about 30 kHz. In order to realize such high-frequency vibrations, the reflectors used in television projectors, etc. are formed by using a semiconductor process to form a small reflector, and the reflector is made smaller and thinner and lighter. The natural vibration frequency of can be designed high.

  The deflecting reflector 2 of FIG. 2 shows a small deflecting reflector model which is a MEMS (Micro Electro Mechanical Systems) mirror formed by this semiconductor process.

  The deflection reflector 2 shown in FIG. 2 includes first and second support frame portions 10 and 11 having a rectangular frame shape, and a rectangular movable mirror portion (scanning mirror portion) 12 serving as a reflector body. The movable mirror portion 12 is disposed in the first support frame portion 10, and the first support frame portion 10 is disposed in the second support frame portion 11.

  Further, as shown in FIG. 2A, the first support frame portion 10 has four support frame portions 10a to 10d, and the second support frame portion 11 has four support frame portions 11a to 11d, which are movable. The mirror part 12 has four mirror side parts 12a to 12d. The support frame portions 10a and 10c are located on the opposite sides, the support frame portions 10b and 10d are located on the opposite sides, the support frame portions 11a and 11c are located on the opposite sides, and the support frame portions 11b and 11d are located on each other. Located on the opposite side. The mirror side portions 12b and 12d of the movable mirror portion 12 correspond to the support frame portions 10b and 10d, and the support frame portions 10a and 10c correspond to the support frame portions 11a and 11c.

  And the longitudinal direction center part of the mirror side parts 12b and 12d of the movable mirror part 12 is connected to the longitudinal direction center part of the support frame parts 10b and 10d via elastic support parts (first rotation shafts) 13 and 13, respectively. ing. Further, the longitudinal center portions of the support frame portions 10a and 10c are connected to the longitudinal center portions of the support frame portions 11a and 11c via elastic support portions (second rotation shafts) 14 and 14, respectively.

Note that the deflecting reflector 2 generates an electrostatic voltage between the movable mirror portions 12 that is not shown in the drawing and that causes the left and right rotations of the movable mirror portion 12 around the elastic support portions 13 and 13 as shown in FIG. A fixed electrode and a second fixed electrode (not shown) that generates an electrostatic voltage between the movable mirror portion 12 that causes the movable mirror portion 12 to rotate up and down around the elastic support portions 14 and 14 are provided.
By variably controlling the electrostatic voltage between the first fixed electrode and the movable mirror 12, the movable mirror portion 12 can be rotated left and right (horizontal rotation) about the elastic support portions 13 and 13, By variably controlling the electrostatic voltage between the second fixed electrode and the movable mirror 12, the movable mirror portion 12 can be turned up and down (vertically turned) about the elastic support portions 14 and 14. Since this configuration is well known in the MEMS technology, its detailed description is omitted. The movable mirror section 12 is driven to rotate by control so that the synthetic laser beam Lb can be scanned called raster scan.

Scan control called raster scan is performed by the control circuit 20 shown in FIG.
<Control circuit>
The control circuit 20 includes a video decoder 21 to which a video signal is input as video information, and a frame memory 22 that stores image data from the video decoder 21. The video decoder 21 converts the pixel coordinate position and color (R, G, B) in the video information into pixel information (image data) based on the vertical / horizontal timing information of the input video information and the color information of the video signal. The reconstructed pixel information is written into the frame memory (frame buffer) 22.
(Signal generators S1, S2)
The control circuit 20 also generates a first control signal (horizontal control signal generator) for controlling the movable mirror 12 of the deflecting reflector 2 around the elastic support portions (first rotation shafts) 13 and 13. Instrument) S1 and a signal generator (vertical control signal generator) for generating a second control signal for controlling rotation of the movable mirror section 12 of the deflecting reflector 2 around the elastic support sections (second rotation shafts) 14 and 14. S2.
(Voltage application drivers Md1, Md2)
Further, the control circuit 20 includes a voltage application driver Md1 for generating an electrostatic voltage for rotating the movable mirror portion 12 of the deflecting reflector 2 in the left-right direction (horizontal direction) based on the first control signal of the signal generator S1, and a signal. A voltage application driver Md2 that generates an electrostatic voltage for rotating the movable mirror portion 12 of the deflecting reflector 2 in the vertical direction (vertical direction) based on the second control signal of the generator S2.
(Output control unit 23)
The control circuit 20 includes an output control unit (output control circuit) 23 to which R, G, and B pixel information (image data) stored in the frame memory 22 is input. The output control unit 23 estimates the movement of the movable mirror unit 12 of the deflecting reflector 2 in accordance with the timing of the signals generated by the signal generator S1 and the signal generator S2, and reflects the reflection of the movable mirror unit 12 of the deflecting reflector 2. The coordinate position of light is calculated. In addition, the output control unit 23 reads pixel information from the frame memory 22 corresponding to the calculated coordinate position of the reflected light.
(Detector 24)
Further, the control circuit 20 includes a detector (angle sensor) 24 that detects a rotational position (horizontal rotation angle) in the horizontal direction of the movable mirror section 12 and a rotational position (vertical rotation angle) in the vertical direction of the movable mirror section 12. Have.

  The detector 24 detects the actual rotational position of the movable mirror unit 12 of the deflecting reflector 2 as a signal related to the angle of the movable mirror unit 12. As the detector 24, for example, a strain sensor that detects distortion due to torsion of the elastic support portions 13 and 14, or a photodetector such as a photodiode that detects light reflected by the movable mirror portion 12 can be used. .

  When a strain sensor that detects torsion of the elastic support portion 13 (first rotation shaft) and the elastic support portion 14 (second rotation shaft) supported by the movable mirror portion 12 is used as the detector 24, the detection is performed by the detector 24. The rotation angle of the movable mirror unit 12 is obtained from the magnitude of the distortion, and the timing at which the screen 8 is irradiated with the bright spot of the laser beam from the movable mirror unit 12 can be determined from the obtained rotation angle.

Further, when a light detector (for example, a photodiode) that detects light reflected by the movable mirror unit 12 is used as the detector 24, when the light detector detects light reflected by the movable mirror unit 12, the movable mirror The timing at which the unit 12 irradiates the bright spot of the laser beam in the direction in which the photodetector (for example, a photodiode) is installed can be seen. The timing at which the movable mirror unit 12 irradiates the light detector with the bright spot of the laser beam is the timing at which the movable mirror unit 12 irradiates the screen 8 with the bright spot of the laser beam.
(Driver for LD or laser diode)
Further, the control circuit 20 is driven and controlled by the output control unit 23 based on the angle detection signal of the movable mirror unit 12 from the detector 24 and the video information (image data) of R, G, B, and the red laser diode LD− R, a green laser diode LD-G, a blue laser diode LD-B, a red LD driver Rd for controlling light emission, a green LD driver Gd, and a blue LD driver Bd.

  As described above, the output control unit 23 reads out pixel information corresponding to the calculated position from the frame memory 22, and according to the color signal, the driver Rd for red LD, the driver Gd for green LD, and the driver for blue LD Send drive signal to Bd. The red LD driver Rd controls the emission of the red laser diode LD-R from the input drive signal, and the green LD driver Gd controls the emission of the green laser diode LD-G from the input drive signal. The blue LD driver Bd controls the emission of the blue laser diode LD-B from the input drive signal.

The red laser beam LbR emitted from the red laser diode LD-R, the green laser beam LbG emitted from the green laser diode LD-G, and the blue laser beam LbB emitted from the blue laser diode LD-B are respectively directional. Have Then, the red laser beam LbR, the green laser beam LbG, and the blue laser beam LbB are incident on the movable mirror portion 12 of the deflecting reflector 2 to be reflected and deflected, and are irradiated on the screen 8 to shine on the screen 8. It becomes a point.
<Details of Output Control Unit (Output Control Circuit) 23>
Next, a detailed configuration of the output control unit 23 described above will be described. As shown in FIG. 5, the output control unit 23 includes a buffer reading unit (buffer reading circuit) 25 that reads R, G, and B image data of a video signal stored in a frame memory (frame buffer) 22; Based on the first control signal from the signal generator S1 and the angle detection signal from the detector 24, the first vibration model signal generation for controlling the vibration of the movable mirror portion 12 around the elastic support portion 13 (first rotation axis) is generated. And a second control signal for controlling the vibration of the movable mirror 12 around the elastic support portion 14 (second rotation axis) based on the second control signal from the signal generator S2 and the angle detection signal from the detector 24. A vibration model signal generation unit 27 is included.

  The first vibration model signal generation unit 26 generates a deflection direction signal (first vibration model signal) of the vibration model 1 in the first direction (horizontal direction) of the movable mirror unit 12, and the second vibration model. The signal generation unit 27 generates a deflection direction signal (second vibration model signal) of the vibration model 2 in the second direction (vertical direction) of the movable mirror unit 12.

  The output control unit 23 is movable based on a deflection direction signal (deflection angle signal) in the first direction (horizontal direction) and a deflection direction signal (deflection angle signal) in the second direction (vertical direction). It has a coordinate calculation unit (coordinate calculation circuit) 28 for converting (calculating) the coordinate position in the deflection direction of the laser beam by the mirror unit 12 and a coordinate correction unit 29 for correcting the calculated coordinate position in the deflection direction of the laser beam. .

  The coordinate correction unit 29 has parameters for correcting distortion of the projected image on the screen 8 by the movable mirror unit 12. The coordinate correction unit 29 performs coordinate conversion of the deflection direction signal (deflection angle signal) in the first direction (horizontal direction) and the deflection direction signal (deflection angle signal) in the second direction (vertical direction). The coordinate position in the deflection direction of the laser beam obtained by the movable mirror unit 12 obtained by coordinate conversion is corrected according to the parameters stored in the coordinate correction unit 29 and input to the buffer reading unit (buffer reading circuit) 25.

  The buffer reading unit (buffer reading circuit) 25 then stores R, G, and B image data stored in the frame memory (frame buffer) 22 based on the coordinate position in the deflection direction of the laser beam from the coordinate calculation unit 28. The pixel data of R, G, B corresponding to the coordinate position calculated by the coordinate calculation unit 28 is read out.

  The output control unit 23 also includes a pixel correction unit (pixel correction circuit) 30 that corrects R, G, and B pixel data read by the buffer reading unit 25 for each of R, G, and B.

  The pixel correction unit 30 corrects gamma correction, color correction, brightness / contrast, etc. of the read R, G, B pixel data, and inputs the R pixel data to the red LD driver Rd. Pixel data is input to the green LD driver Gd, and B pixel data is input to the blue LD driver Bd.

  As described above, the coordinate calculation unit 28 determines the output control unit based on the angular position of the movable mirror unit 12 around the first and second rotation axes (elastic support units 13 and 14) calculated based on the vibration models 1 and 2. 23, the coordinates of pixel data to be output are determined. Further, as described above, the vibration model 1, the vibration model 2, coordinate calculation, and buffer reading have at least three systems, for example, three systems of red, blue, and green components, and each process is performed for each color component of the video. Is done.

The first vibration model signal generation unit (vibration model 1) 26 and the second vibration model signal generation unit (vibration model 2) 27 generate, for example, a sine wave. In addition, when the deflecting reflector 2 vibrates due to resonance, a good approximation can be obtained for the sine wave. By correcting the phase of the sine wave by the detector 24, it is possible to match the direction of the actual reflector. Of course, the signals generated from the first and second vibration model signal generators 26 and 27 may not be sine waves as long as they represent the vibration of the deflecting reflector 2.
[Action]
Next, the operation of the video projector which is the beam scanning device described above will be described.
[I]. Basic Scanning Operation of Video Projector When a video signal is input, the video decoder 21 coordinates pixel coordinates in the video information based on the vertical / horizontal timing information of the video information and the color information of the video signal from the input video signal. The position and color (R, G, B) are reconstructed as pixel information (image data), and the reconstructed pixel information is written into the frame memory (frame buffer) 22.

  The signal generator S1 generates a first control signal for controlling the movable mirror portion 12 of the deflection reflector 2 around the elastic support portions (first rotation shafts) 13 and 13, and the signal generator S2 is deflected and reflected. A first control signal is generated to control the rotation of the movable mirror portion 12 of the container 2 around the elastic support portions (second rotation shafts) 14 and 14. The first control signal is input to the voltage application driver Md1, and the second control signal is input to the voltage application driver Md2.

  The voltage application driver Md1 generates an electrostatic voltage for horizontal rotation that drives the movable mirror unit 12 of the deflecting reflector 2 to rotate in the left-right direction (horizontal direction) based on the first control signal. An electric voltage is applied to the movable mirror portion 12 of the deflecting reflector 2. The voltage application driver Md2 generates an electrostatic voltage for vertical rotation that rotates the movable mirror portion 12 of the deflecting reflector 2 in the vertical direction (vertical direction) based on the second control signal. An electrostatic voltage is applied to the movable mirror portion 12 of the deflecting reflector 2.

  Accordingly, the detector (angle sensor) 24 rotates in the horizontal direction (x direction) of the movable mirror unit 12 and in the vertical (vertical) direction (y direction) of the movable mirror unit 12. The position (vertical rotation angle) is detected and a detection signal is output. At this time, the output control unit 23 moves the movable mirror unit 12 of the deflecting reflector 2 based on the detection signal of the detector 24 and the first and second control signals generated by the signal generator S1 and the signal generator S2. A raster scan (scanning timing) is estimated, and the coordinate position of the reflected light by the laser beam of the movable mirror portion 12 of the deflector reflector 2 is calculated.

  Then, the voltage application driver Md1 repeats the single vibration control for rotating the movable mirror unit 12 in the horizontal direction by a predetermined angle based on the first control signal and the detection signal from the detector 24. Further, the voltage application driver Md2 performs control for rotating the movable mirror unit 12 by a predetermined angle in the vertical direction for each horizontal reciprocation of the movable mirror unit 12 based on the second control signal and the detection signal from the detector 24. Control is repeated until the horizontal reciprocating rotational speed reaches a predetermined number.

  As a result, the voltage application drivers Md1, Md2 perform a raster scan operation as shown in FIG. 6 with the laser beam by the movable mirror portion 12 of the deflecting reflector 2, and HL1, HL2,. HLi... An image is formed by scanning lines indicated by HLn.

  Next, a more detailed operation of the output control unit 23 will be described.

  The first vibration model signal generation unit 26 of the output control unit 23 generates a deflection direction signal (first vibration model signal) of the vibration model 1 in the first direction (horizontal direction) of the movable mirror unit 12. The second vibration model signal generation unit 27 of the output control unit 23 generates a deflection direction signal (second vibration model signal) of the vibration model 2 in the second direction (vertical direction) of the movable mirror unit 12. Moreover, the first vibration model signal generation unit 26 is a movable mirror unit around the elastic support unit 13 (first rotation axis) based on the first control signal from the signal generator S1 and the angle detection signal from the detector 24. 12 vibrations are controlled. Further, the second vibration model signal generation unit 27 is a movable mirror unit around the elastic support unit 14 (second rotation axis) based on the second control signal from the signal generator S2 and the angle detection signal from the detector 24. 12 vibrations are controlled.

  Further, the coordinate calculation unit (coordinate calculation circuit) 28 of the output control unit 23 has a deflection direction signal (deflection angle signal) in the first direction (horizontal direction) and a deflection direction signal in the second direction (vertical direction). Based on the (deflection angle signal), the coordinate position in the deflection direction of the laser beam by the movable mirror unit 12 is converted (calculated). At this time, the coordinate calculation unit 29 receives the parameters for the distortion correction of the projected image on the screen 8 by the movable mirror unit 12 to the coordinate calculation unit 28. Then, the coordinate calculation unit 28 corrects the coordinate position in the deflection direction of the laser beam by the movable mirror unit 12 obtained by coordinate conversion based on the parameter from the coordinate correction unit 29, and a buffer reading unit (buffer reading circuit). 25.

  This buffer reading unit (buffer reading circuit) 25 is based on the R, G, B image data stored in the frame memory (frame buffer) 22 based on the coordinate position in the deflection direction of the laser beam from the coordinate calculation unit 28. R, G, B pixel data corresponding to the coordinate position calculated by the coordinate calculation unit 28 is read. The pixel correction unit (pixel correction circuit) 30 of the output control unit 23 corrects the R, G, and B pixel data read by the buffer reading unit 25 for each of R, G, and B. That is, the pixel correction unit 30 corrects gamma correction, color correction, brightness / contrast, and the like of the read R, G, and B pixel data.

  In the pixel data corrected in this way, the R pixel data is input to the red LD driver Rd, the G pixel data is input to the green LD driver Gd, and the B pixel data is input to the blue LD driver. Input to the driver Bd. The red LD driver Rd controls the emission of the red laser diode LD-R from the input drive signal, and the green LD driver Gd controls the emission of the green laser diode LD-G from the input drive signal. The blue LD driver Bd controls the emission of the blue laser diode LD-B from the input drive signal.

The red laser beam LbR generated from the red laser diode LD-R is converted into a parallel beam by the lens 3, the green laser beam LbG generated from the green laser diode LD-G is converted into a parallel beam by the lens 4, and the blue laser diode LD- The blue laser beam LbB generated from B is converted into a parallel beam by the lens 5. The green laser beam LbG generated from the green laser diode LD-G is reflected by the dichroic mirror 6 and combined with the red laser beam LbR that passes through the dichroic mirror 6 so as to become a single light. . Further, the blue laser beam LbB generated from the blue laser diode LD-B is reflected by the dichroic mirror 7 and is combined with the red laser beam LbR and the green laser beam LbG that pass through the dichroic mirror 7. The combined laser beam Lb. The combined laser beam Lb is scanned by the movable mirror portion 12 of the deflecting reflector 2 and projected onto the screen 8 to form an image by raster scanning on the screen 8.
[II]. Determination of vibration frequency of scanning control In the control accompanying image formation by such raster scanning, when the movable mirror unit 12 deflects the laser beam in two directions perpendicular to each other, the image forming control is performed as described below. Therefore, the vibration frequency of the movable mirror unit 12 is determined. Here, one of the deflection directions is referred to as a first deflection direction, and the other is referred to as a second deflection direction, and the setting of the vibration frequency will be described.

The first deflection direction and the second deflection direction are directions in which simple single oscillation is performed independently of each other. In the example described above, the first deflection direction is the horizontal direction, and the second deflection direction is the vertical direction.
Here, when the frequency f ₁ of vibration in the first deflection direction is T ₁ , the period T ₁ is
... (1)
It is represented by

When the frequency f ₂ in the second deflection direction is T ₂ and the period T ₂ is
... (2)
It is represented by
(i). Scanning control based on Lissajous figure of deflection reflector 2 The first deflection direction (horizontal direction) and the second deflection direction (vertical direction) are substantially orthogonal directions, and the first deflection direction And α is the phase difference between the second vibration and the second deflection direction. Here, the operation of the deflection reflector 2 will be described with the first deflection direction (horizontal direction) as the x direction and the second deflection direction (vertical direction) as the y direction.

  By combining the vibrations in the x and y directions, the deflection direction of the deflecting reflector 2 draws a Lissajous figure as shown in FIG. 7, for example.

  The ratio of the frequency in the x direction and the y direction is 10: 3, which is an example in the case of α = 0 degrees. By projecting light rays in such a direction and projecting them onto the screen 8, the rectangular area of the screen 8 is scanned. Although the size and aspect ratio of the rectangular area can be changed depending on the amplitude of the vibration, the description here assumes that the amplitude ratio of x and y is 1: 1.

  FIG. 8 shows a case where the Lissajous figure as shown in FIG. 7 reciprocates once in the y direction. When the time T2 for one reciprocation in the y direction has elapsed, the vibration in the x direction advances in phase by β degrees.

... (3)
It has become. Since the frequency ratio is 10: 3, β is 120 degrees.

  Therefore, the Lissajous figure does not return to the starting point in one round trip, but returns to a position shifted by 120 degrees in the x direction.

  When y reciprocates, the position shifts by 120 degrees, so when it reciprocates three times, it rotates exactly 360 degrees and returns to the starting point.

  Considering that this Lissajous figure constitutes pixels with a resolution of 20 × 20, for example, FIG. 9 is obtained. In the white pixel in FIG. 9, the scanning line does not pass no matter how many times the deflector scans.

  As in this example, scanning with a Lissajous figure tends to cause scanning unevenness. Further, in order to uniformly scan the rectangular area of the screen 8, the scanning resolution and the scanning frequency must be appropriately selected.

  To reduce the number of unscanned locations, it is better to review the angle β. This means that a rotation of β degrees x direction occurs in one round trip in the y direction. For example, if a combination of frequencies such that β is 10 degrees is selected, a deviation of 10 degrees occurs in the x direction every round trip in the y direction. . According to the previous frequency example, the frequency ratio is f1: f2 = 10: 3.30275. An example of the scanning line at this time is shown in FIG.

Thus, when β is set to a small angle, scanning with higher density becomes possible. However, the time for scanning the entire rectangular area increases. If β = 10 degrees, a time to reciprocate in the y direction 36 times is required.
(ii) Conditions for reducing scanning unevenness Therefore, a condition is set where the scanning position in the x direction is adjacent to the previous scanning position when the scanning position in the y direction having a low frequency vibrates and returns. . This is shown in FIG. This is a schematic diagram of scanning at the center of vibration where the displacement speed of vibration becomes the fastest. t _yd represents the time for the y-axis vibration to cross this horizontal pixel. After the scan # 1 is scanned, the scan of y returns to this vertical position after a half cycle and scans the scan # 2. At this time, if the scan # 1 and the scan # 2 are adjacent to each other, the scan is uniform with few gaps and overlaps.

The conditions for performing such scanning are as follows:
・ X axis vibration frequency: f ₁ = f _x (Hz)
・ Y-axis vibration frequency: f ₂ = f _y (Hz),
・ Period: T _y (Hz),
・ Period: T _x (Hz),
・ Frame rate: F (frames / second),
-Resolution in the x direction of the projected image: X (pixel),
・ Resolution in the y direction of the projected image: Y (pixel),
Is obtained as follows.

The x-axis phase for each period (time) T _y is

... (4)
Will go on. In addition, in order to always rotate the phase by γ at time T _y / 2, half cycle of y vibration (vibration in y direction)

... (5)
The relationship should be established. Here, n represents the number of vibrations of the x axis within the time T _y / 2, and is a positive integer. In the γ term, + indicates that the phase is advanced, and-indicates that the phase is delayed. This is shown in FIG.

  Next, a condition for returning to a position adjacent to the previous scanning position when the y-axis returns to the horizontal scanning position of the vibration center will be considered.

_Assuming that the time that the y-axis crosses one pixel is t _yd , the Y scan line is scanned twice in one cycle of the y-axis, so the time t _yd is
... (6)
It becomes. At this time, the x-axis
... (7)
Only horizontal rotation is performed.

Then, when the y-axis returns to the horizontal scanning position, the scanning is started from the side next to the previous horizontal scanning portion.
The x-axis phase is
... (8)
It only needs to rotate.

Next, consider how many times the scanning in the x direction should be performed with one reciprocation of the y axis. Since the frame rate is F, the y-axis vibrates f _y / F times in 1 frame time 1 / F second. At this time, at least Y horizontal scans may be performed and Y scans may be completed in 1 / F seconds. Assuming two scans with one round trip of x, n is

... (9)
What should I do?
Substituting these into equation (5) above,
... (10)
It becomes.

Here, for example, if F = 60 frame per second and Y = 600,
n = 75 and f _x ≈18030 Hz. Select Y and F where n is an integer.

It is desirable that f _y is a frequency of at least F, and if it is a frequency that is a multiple of F, it is easy to become familiar with the idea of the frame rate.

From the above, as a design value, the frame rate F, the number of pixels in the horizontal direction X, the number of pixels in the vertical direction Y, the frequency f _x, the frequency f _y, etc., for example · F = 60f / s,
・ X = 700,
・ Y = 600,
・ F _x = 18030Hz,
・ F _y = 120Hz
Can be selected.

Here, it is assumed that the plurality of pixels constituting the number Y of pixels in the vertical direction are equally spaced. However, when the angle of the rotating mirror represents the frequency f _y oscillating sinusoidally, the rotation angle of the mirror and the position of the projected bright spot are not expressed by the relationship of the linear expression, and the interval between the projected pixels is not equal. . For this reason, a value larger than the vertical resolution of the image to be projected is used for Y.

  Further, since the scanning speed is low near the maximum amplitude of the sine wave vibration, it is preferable not to use it as an image projection area. For this reason, video is not projected near the periphery of the projection area, and the Y value is set to a large value taking this range into account. For example, when the projection resolution is set to the VGA size of 640 × 480 pixels, it may be included in the values of X and Y such as X = 800 and Y = 600.

  According to such a configuration, a plurality of combinations of vibration frequencies of the deflecting reflector 2 can be selected. This increases the degree of design freedom in manufacturing the deflecting reflector 2, and makes it possible to study a lower cost method.

  For example, in the case of making a deflecting reflector having two-axis deflection directions, it is conceivable that deflecting reflectors in different directions are nested in a unidirectional deflecting reflector. In this case, the mother deflecting reflector is larger and heavier than the sub deflecting reflector because of the insertion of the sub deflecting reflector. That is, the resonance frequencies of the mother deflector reflector and the child deflector reflector are greatly different. In such a case, the possibility of finding a suitable frequency combination increases by examining a combination of frequencies having a large N.

In the case of the present embodiment, for example, the movable mirror portion 12 can be regarded as a child deflecting reflector and the portion including the first support frame portion 10 and the movable mirror portion 12 can be regarded as a main mother deflecting reflector. The movable mirror unit 12 can be regarded as a mother deflector reflector, and the portion including the first support frame unit 10 and the movable mirror unit 12 can be regarded as a main mother deflector reflector.
(Modification 1)
In the embodiment described above, an example is shown in which the deflecting reflector 2 is provided with the first and second rotating shafts (elastic support portions 13 and 14) for rotating the movable mirror portion 12 in directions perpendicular to each other. However, the present invention is not necessarily limited to this.

  For example, as shown in FIG. 13, the first deflection reflector (horizontal deflection reflector) 2x that deflects the laser beam Lb in the first direction (horizontal direction) and the laser beam Lb in the second direction (vertical direction). The deflecting reflector 2 may be composed of a second deflecting reflector (vertical deflecting reflector) 2y that deflects the light. The first deflecting reflector 2x and the second deflecting reflector 2y can be easily manufactured as a MEMS by a semiconductor process (semiconductor manufacturing process).

  The first deflection reflector 2x includes a first support frame portion 10, a square first deflection reflector (first reflector) 12x disposed in the first support frame portion 10, and a first deflection reflection. Elastic support portions (first rotation shafts) 13 and 13 that support the container 12x on the support frame portions 10b and 10d of the first support frame portion 10. The second deflection reflector 2y includes a second support frame portion 11, a square second deflection reflector (second reflector) 12y disposed in the second support frame portion 11, and a second deflection reflector 12y. Elastic support portions (second rotation shafts) 14 and 14 are supported by the support frame portions 11a and 11c of the second support frame portion 11.

  The deflecting reflector 2 shown in FIG. 13 can perform the same scan as the deflecting reflector 2 shown in FIG.

  According to such a configuration, as shown in FIG. 13, the deflection reflector 2 of FIG. 2 is replaced with the first deflection reflector (horizontal deflection reflector) 2x and the second deflection reflector (vertical deflection reflector) 2y. Therefore, a plurality of combinations of vibration frequencies in the first deflection direction (horizontal direction) and the second deflection direction (vertical direction) can be selected. This increases the degree of design freedom in manufacturing the deflecting reflector 2, and makes it possible to study a lower cost method.

  Further, as another example, the present invention can be applied to an image acquisition device that acquires a distant image contrary to a video projector. FIG. 14 shows an example of this image acquisition apparatus. In FIG. 14, reference numeral 31 denotes a photodetector, and 32 denotes a lens.

  In this image acquisition device, a light beam of a minute part of the subject is provided so as to be incident on the deflecting reflector 2 via an optical member such as a lens (not shown), and the minute part of the subject is driven by driving the deflecting reflector 2. The position where the light beam is acquired is scanned by raster scan so that the light beam of this minute portion is incident on the deflecting reflector 2 as a spot beam-like light beam. Then, the incident light beam is deflected by the deflecting reflector 2 and incident on the photodetector 31 through the lens 32, so that it is detected by the photodetector 31. At this time, the photodetector 31 detects the amount of light such as R, G, B, etc. of the light beam in the minute part of the subject. Further, the coordinate position of the minute part for acquiring the light beam of the subject can be obtained from the rotation angle of the movable mirror portion 12 of the deflecting reflector 2 in the x and y directions, and the coordinate position of the minute part for acquiring the light beam of the subject. An image can be formed by associating the detection value of the photo detector 31 with each other.

As described above, the electromagnetic wave scanning method according to the embodiment of the present invention includes the deflector (deflecting reflector 2) that changes the direction of the electromagnetic wave, and the deflecting device (deflecting reflector 2) is independently vibrated. A space is two-dimensionally scanned by scanning an electromagnetic wave having a first deflection direction x and a second deflection direction y and deflected by the deflector (deflection reflector 2). Moreover, the resolution of the second deflection direction Y, when the scanning of the entire scanning area is the frame rate finish was F, a first deflection frequency f _x,

It is said.

  According to such an electromagnetic wave scanning method, the first deflection frequency can be determined from the resolution and the frame rate, so that the full scan can be completed at the specified frame rate, and the application is intended for video image projection. The design value becomes clear. Thereby, a frequency suitable for video projection can be determined.

  In addition, the image projection apparatus and the image acquisition apparatus using this electromagnetic wave scanning method can determine the first deflection frequency from the resolution and the frame rate, so that the entire scanning can be completed at the designated frame rate. Design values for applications aiming at video projection are clear. Thereby, a frequency suitable for video projection can be determined.

Further, when the scanning method of the electromagnetic wave embodiment of the present invention, the second deflection frequency is f _y,

Is a combination of F, Y, and f _{y in} which is an integer.
According to this method, it is possible to reduce pixel scanning unevenness when scanning a bright spot based on a Lissajous figure.

  In addition, the image projection apparatus according to the embodiment of the present invention uses the above-described electromagnetic wave scanning method. With this video projection device, video projection with less noticeable scanning unevenness is possible. In addition, a degree of freedom in design arises in the frequency of the deflector necessary for projection scanning, and it becomes possible to use a deflector with lower cost.

  Furthermore, the image acquisition apparatus according to the embodiment of the present invention uses the above-described electromagnetic wave scanning method. With this image acquisition device, it is possible to acquire an image with inconspicuous scanning unevenness. In addition, there is a degree of design freedom in the frequency of the deflector necessary for image acquisition, and it becomes possible to use a lower cost deflector.

  The electromagnetic wave scanning method according to the present invention can be applied to other medical devices such as infrared image acquisition devices and X-ray image acquisition devices by using electromagnetic waves such as infrared rays, ultraviolet rays, X-rays or other radiations.

2 ... deflecting reflector 8 ... screen 12 ... movable mirror 31 ... photodetector

Special Table 2005-526289

Claims (4)

Has a deflector to change the direction of electromagnetic waves,
The deflector has a vibrating independent first deflection direction x and a second deflection direction y;
In a scanning method for scanning a space two-dimensionally by scanning an electromagnetic wave deflected by the deflector,
The resolution of the second deflection direction Y, when the scanning of the entire scanning area has a frame rate completed and F, the first deflection frequency f _x,
An electromagnetic wave scanning method characterized by the above. The scanning method of claim 1,
When the second deflection frequency is f _y
F but which becomes an integer, electromagnetic wave scanning method which is characterized in that a combination of Y and f _y.   An image projection apparatus using the electromagnetic wave scanning method according to claim 1 or 2.   3. An image acquisition apparatus using the electromagnetic wave scanning method according to claim 1.