JP2009244799A - Image projecting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a change in a resonance point and to change a driving frequency so as not to generate distortion in a projected image in an image projecting apparatus 1 using a resonance type high-speed optical scanner 3. <P>SOLUTION: The image projecting apparatus includes an oscillation detection part 6 for detecting an oscillation state of the high-speed optical scanner 3 and a phase comparison part 7 for comparing a phase of a first driving signal for driving the high-speed optical scanner 3 with a phase of the detected oscillation. At the timing when a phase difference between the phase of the first driving signal and the phase of the detected oscillation exceeds a prescribed value, a scanner driving part 5 changes the frequency of the first driving signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image projection apparatus that modulates light emitted from a light source in accordance with an input image signal, scans the modulated image light with an optical scanner, and draws an image on a projection surface.

  FIG. 14 is a block diagram showing a conventionally known retinal scanning image projection apparatus (see, for example, Patent Document 1). The image projection apparatus 100 directly forms an image on the retina 120 of the user's eyeball 118. Video light emitted from the B laser 107 that emits blue light, the G laser 108 that emits green light, and the R laser 109 that emits red light is converted into parallel light by the collimating optical system 110 and synthesized by the dichroic mirror 111. The light is condensed by the coupling optical system 112 and is incident on the optical fiber 119. The image light emitted from the optical fiber 119 is applied to the mirror unit 127 of the optical scanning element 122 via the second collimating optical system 113. The mirror unit 127 is driven and oscillated by the horizontal scanning driving circuit 114 to horizontally scan the reflected light. The horizontally scanned image light is applied to the galvanometer mirror 121 via the first relay optical system 115. The galvano mirror 121 scans the reflected light in the vertical direction with its mirror surface oscillated by a magnetic field. The image light reflected from the galvanometer mirror 121 is imaged on the retina 120 of the eyeball 118 through the first lens 123a and the second lens 123b constituting the second relay optical system.

  The video signal supply circuit 103 inputs a video signal and outputs image signals corresponding to blue (B), green (G), and red (R) colors to the B laser driving circuit 104, the G laser driving circuit 105, and the R laser. Output to each of the drive circuits 106. The B laser 107 emits a B-color laser beam whose light intensity is modulated based on a drive signal from the B laser drive circuit 104. Similarly, the G laser 108 and the R laser 109 emit laser light of each color whose light intensity is modulated based on each image signal. The video signal supply circuit 103 outputs a horizontal synchronizing signal and a vertical synchronizing signal synchronized with the image signal to the horizontal scanning driving circuit 114 and the vertical scanning driving circuit 116. The horizontal scanning drive circuit 114 outputs a drive signal to the optical scanning element 122 to swing the mirror unit 127. The oscillation in this case is based on the resonant oscillation of the mirror unit 127.

  Patent Document 2 describes an optical scanning device that draws a two-dimensional image using a galvanometer mirror driven at a resonance period for horizontal scanning and a stepping motor for vertical scanning. The vertical scanning by the stepping motor includes a sweep period in which the projection image is projected and a blanking period in which the projection image is not projected. Galvano mirrors used for horizontal scanning have a resonance cycle that varies depending on environmental characteristics such as variations in mechanical structure and temperature. When the resonance period changes, the horizontal scanning period changes, causing problems such as folding of the lower end of the projected image or shortening of the lower end of the projected image.

In order to prevent this, the time length of the sweep period is determined by the product of the resonance period of the galvanomirror and the number of scanning lines, and the time length of the blanking period is determined by the time length obtained by subtracting the sweep period from the frame period. In other words, even if the resonance period of the galvanometer mirror fluctuates, the lower end of the projected image is not changed.
JP 2008-009326 A JP 2003-302590 A

  In the image projection apparatus described in Patent Document 1, an optical scanner using resonance vibration of a mirror is used as the optical scanning element 122 that performs horizontal scanning of laser light. An optical scanner normally vibrates at a frequency of about 30,000 Hz. However, since resonance vibration is used, the resonance point changes due to a physical change of the oscillating portion and a change in ambient temperature. When the resonance point changes, the amplitude of the oscillating portion decreases, and the projected image is distorted. In order to compensate for this, the drive voltage for driving the optical scanner can be increased, but the power consumption is increased and the energy efficiency is lowered. In addition, if a drive signal with a changed frequency is supplied from the horizontal scanning drive circuit in accordance with the ambient temperature change or the resonance point change with time, the projection image is distorted or uneven in brightness immediately after the supply, and the projection image Image quality has deteriorated.

  The optical scanning device described in Patent Document 2 uses a method in which a shift in the horizontal scanning resonance period is absorbed by a blanking period in the vertical scanning. When the galvanometer that performs horizontal scanning shifts from the resonance point, a drive signal is output. It is not described how to change. When a drive signal with a changed frequency is supplied from the drive circuit when the resonance point changes, similarly to Patent Document 1, distortion and luminance unevenness occur in the projected image immediately after the drive signal is supplied.

  In the present invention, the following means have been taken in order to solve the above problems.

  In the invention according to claim 1, an image modulating unit that modulates a light beam from a light source according to an image signal, an optical scanner that scans the light beam with a reflecting surface that oscillates to form a projection image, and A scanner driving unit that generates a drive signal for swinging the optical scanner, and the scanner includes a resonance type high-speed optical scanner that scans in the main scanning direction and a low-speed optical scanner that scans in the sub-scanning direction. In the image projection device that generates a first drive signal for driving the high-speed optical scanner, the drive unit detects a swing state of the high-speed optical scanner, and a phase of the first drive signal and the detection A phase comparison unit that compares the phase of the oscillation that has been detected, and the phase difference between the phase of the first drive signal and the phase of the oscillation that has been detected exceeds a predetermined value. , Catcher Na driver was image projection apparatus characterized by changing the frequency of the first drive signal.

  In the invention according to claim 2, the predetermined value is that the distortion of the projected image generated when the scanner driving unit applies the first driving signal having the changed frequency to the high-speed optical scanner is approximately one frame. The image projector according to claim 1, wherein the phase difference is eliminated in a period.

  The invention according to claim 3 is characterized in that a projection image based on the light beam is not projected for a period of one frame of the projection image projected by the optical scanner, triggered by a change in the frequency of the first drive signal. The image projection apparatus according to claim 1 or 2.

  According to a fourth aspect of the invention, the image modulation unit performs a blurring process on the projected image for a period of one frame of the projected image, triggered by a change in the frequency of the first drive signal. The image projector according to any one of claims 1 to 3, wherein

  In the invention according to claim 5, in one scanning period of the low-speed optical scanner, a first scanning period for scanning an effective area on which the projection image is projected and an invalid area that is an area outside the effective area are scanned. 5. The frequency change is performed after the phase difference exceeds the predetermined value and during the second scanning period. 5. It was set as the image projector of any one of these.

  6. The image projecting device according to claim 5, wherein the frequency change is performed immediately after the low-speed light scanner scans in the second scanning period. did.

In the invention according to claim 7, there is provided a mask portion for blocking the scanning light beam from being applied to an ineffective region that is an outer region of the region onto which the projection image is projected,
The optical scanner driving unit stops the oscillation of the low-speed optical scanner for a period of one frame when the frequency of the first drive signal is changed. Image projection apparatus.

  The invention according to claim 8 further includes a temperature sensor for detecting a temperature, and the change of the frequency is triggered by the detected temperature exceeding a predetermined temperature change, or the phase difference becomes the predetermined value. The image projecting device according to claim 1, wherein the image projecting device is performed in response to exceeding.

  The invention according to claim 9 further includes: an image memory unit that stores image data based on the image signal; and an image analysis unit that analyzes the stored image data, and the change of the frequency is The image projecting device according to claim 1, wherein the image analyzing unit is performed when the temporal change of the stored image data is detected to be small. .

  The invention according to claim 10 further includes an image memory unit that stores image data based on the image signal, and an image analysis unit that analyzes the stored image data, and the change of the frequency is performed by the image The image projecting apparatus according to claim 1, wherein the image projecting apparatus is performed when the analysis unit detects that the stored image data has a low projection luminance.

  In the image projection apparatus according to claim 1, the fluctuation detection unit that detects the fluctuation state of the high-speed optical scanner is compared with the phase of the first driving signal that drives the high-speed optical scanner and the detected phase of the fluctuation. And the phase difference between the phase of the first drive signal and the detected oscillation phase exceeds a predetermined value, and the scanner drive unit receives the frequency of the first drive signal. Was changed. Thereby, without using a complicated circuit, the resonance frequency and the driving frequency can be matched, power consumption can be reduced, and the mechanical load applied to the vibrating body can be reduced.

  In the image projection apparatus according to claim 2, the distortion of the projected image that occurs when the first drive signal having the changed frequency is applied to the high-speed optical scanner as the predetermined value is approximately one frame. The phase difference disappears in the period. This makes it difficult for the user to recognize the image distortion when the frequency is changed, thereby preventing the image quality from being deteriorated.

  In the image projection device according to claim 3, the projection image based on the light beam is not projected for a period of one frame of the projection image projected by the optical scanner when the frequency of the first drive signal is changed. did. As a result, the user has an advantage that the distortion and luminance unevenness of the projected image are hardly recognized.

  In the image projection device according to claim 4, the image modulation unit performs a blurring process on the projected image for a period of one frame of the projected image, triggered by the change in the frequency of the first drive signal. I did it. As a result, an image to be projected becomes unclear, and there is an advantage that distortion and luminance unevenness when the frequency of the drive signal is changed are not noticeable.

  Further, in the image projection apparatus according to claims 5 and 6, one scanning period of the low-speed optical scanner includes a first scanning period for scanning an effective area on which a projection image is projected and an invalid area that is an area outside the effective area. The frequency change is performed after the phase difference exceeds a predetermined value and the scanning of the high-speed optical scanner is performed during the second scanning period. did. Thereby, the distortion given to the projection image of an effective area | region can be reduced.

  The image projection apparatus according to claim 7 is provided with a mask unit for blocking the scanning light beam from being irradiated to the invalid area which is an area outside the area where the projection image is projected. In response to the change in the frequency of the first drive signal, the optical scanner drive unit stops the oscillation of the low-speed optical scanner for a period of one frame. As a result, since the light beam is not projected onto the projection surface during the period of one frame, it is possible to prevent a deterioration in the quality of the projected image such as a brighter outer area of the effective area.

  The image projection apparatus according to claim 8 further includes a temperature sensor that detects the temperature, and the change in frequency is triggered by the detected temperature exceeding a predetermined temperature change, or the phase difference is a predetermined value. It was made to take place when it exceeded. As a result, it is possible to prevent the projection image from being distorted or uneven in brightness when the ambient temperature changes.

  The image projection apparatus according to claims 9 and 10 further includes an image memory unit that stores image data based on the image signal, and an image analysis unit that analyzes the stored image data, and the frequency change is This is performed when the image analysis unit detects that the temporal change in the stored image data is small or the projection luminance is low. Therefore, since the frequency is changed when the projected image is almost constant or when the brightness is low, even when the projected image is disturbed due to the change of the frequency, the user recognizes the disturbance of the projected image. It becomes difficult.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram showing a basic configuration of an image projection apparatus 1 of the present invention. The image projection apparatus 1 includes a light source 9, a resonance type high-speed optical scanner 3 that enters a light beam emitted from the light source 9 through a relay lens 10 and scans in a main scanning direction (X direction), and high-speed light. A light beam scanned from the scanner 3 is made incident through the relay lens 10 and scanned in the sub-scanning direction (Y direction), and projection optics for imaging the scanned light beam on the projection surface 12. The system 11 includes a light source 9, a high-speed optical scanner 3, and a signal processing unit 15 that drives the low-speed optical scanner 4.

  The signal processing unit 15 includes an image modulation unit 2 that modulates a light beam emitted from the light source 9 based on an input image signal, a scanner driving unit 5 that drives the high-speed optical scanner 3 and the low-speed optical scanner 4, and a high-speed optical scanner. 3, a swing detection unit 6 that detects the swing state of 3, a drive signal that drives the high-speed optical scanner 3 from the scanner drive unit 5, and a swing signal that indicates the swing state of the high-speed optical scanner 3 from the swing detection unit 6. And a phase comparator 7 for detecting a phase difference between the first and second phases.

  The image projector 1 is driven as follows. The light beam emitted from the light source 9 is scanned at high speed in the X direction, which is the main scanning direction, on the projection surface 12 by the high speed optical scanner 3, and at low speed in the Y direction, which is the sub scanning direction, on the projection surface 12 by the low speed optical scanner 4. Scanned. Therefore, a projection image is drawn on the projection surface 12 by one light beam. A period from the upper left scanning start point to the lower right scanning end point is a period of one frame. Usually, scanning is performed several hundred times or more in the main scanning direction in one frame period, that is, in a period in which scanning is performed once in the sub-scanning direction. One frame period is usually 1/60 sec.

  In the high-speed optical scanner 3, the reflection surface that reflects light performs resonance type oscillation. The scanner drive unit 5 provides a first drive signal having a frequency that matches the resonance frequency of the high-speed optical scanner 3. As a result, the swing of the maximum amplitude can be performed with the minimum energy consumption of the first drive signal. The scanner drive unit 5 gives the second drive signal to the low-speed optical scanner 4 on the basis of the frequency of the first drive signal. The reflecting surface of the low-speed optical scanner 4 performs forced oscillation whose oscillation width is determined by the potential of the second drive signal. The scanner driving unit 5 uses a frame synchronization signal for determining a scanning start point of frame scanning on the projection surface 12 and a horizontal synchronization signal for determining a drawing start point at which image drawing starts on the basis of the frequency of the first drive signal. It is generated and given to the image modulation unit 2. The image modulation unit 2 inputs a frame synchronization signal, a horizontal synchronization signal, and an image signal, generates a light source drive signal, and controls light emission of the light source 9.

  In the high-speed optical scanner 3, the resonance point fluctuates with time or due to environmental changes. As a result, a deviation occurs between the resonance frequency of the high-speed optical scanner 3 and the frequency of the first drive signal. Since the Q value of the high-speed optical scanner 3 has a very large value, for example, 500 to 1500, if this deviation occurs, the amplitude of the reflection surface of the high-speed optical scanner 3 decreases and the current of the first drive signal increases. Power consumption increases. Since the first drive signal having a frequency shifted from the resonance point of the high-speed optical scanner 3 is given, the mechanical load given to the vibrating body also increases. Further, when a deviation occurs between the resonance frequency of the high-speed optical scanner 3 and the frequency of the first drive signal, the actual oscillation phase of the high-speed optical scanner 3 and the phase of the first drive signal applied to the high-speed optical scanner 3 Deviation occurs between

  The swing detection unit 6 detects the actual swing state of the high-speed optical scanner 3 and generates a swing signal. The phase comparison unit 7 detects a phase difference between the phase of the first drive signal applied to the high-speed optical scanner 3 and the oscillation phase of the high-speed optical scanner 3 detected by the oscillation detection unit 6. Then, when this phase difference exceeds a predetermined value, the scanner drive unit 5 changes the frequency of the first drive signal given to the high-speed optical scanner 3. This change in frequency is changed so as to approach the changed resonance frequency of the high-speed optical scanner 3. That is, when the resonance point of the high-speed optical scanner 3 fluctuates due to a change with time or an environmental change, the high-speed optical scanner 3 is driven while being intermittently corrected so as to approach the changed resonance frequency. Thereby, without using a complicated circuit, the resonance frequency and the driving frequency can be matched, power consumption can be reduced, and the mechanical load applied to the vibrating body can be reduced.

  FIG. 2 is an explanatory diagram for explaining a change in vibration of the high-speed optical scanner 3 when the frequency of the first drive signal for driving the high-speed optical scanner 3 is changed. 2A shows the displacement of the vibration plane of the optical scanner with respect to time, and FIG. 2B shows the projection of the light beam from the scanning start point P1 to the scanning end point P2 on the projection plane 12 during the frame 1 period. Represents the trajectory.

  In FIG. 2A, the horizontal axis represents time, and the vertical axis represents the displacement (for example, angle) of the optical scanner. A solid line displacement D1 represents the displacement of the reflecting surface of the high-speed optical scanner 3, and represents a state before the frequency of the first drive signal is changed. The solid line displacement D3 represents the displacement of the reflecting surface of the low-speed optical scanner 4. A broken line displacement D <b> 2 represents an example of the displacement of the reflection surface when a drive signal having a changed frequency is given to the high-speed optical scanner 3. As indicated by displacement D3, the low-speed optical scanner 4 starts displacement from time t0 and ends frame 1 at time t3. The low-speed optical scanner 4 restores the displacement at time t3 and increases the displacement again to scan the frame 2. The reflection surface of the high-speed optical scanner 3 continuously oscillates and oscillates with a predetermined displacement width. Then, the light beam modulated by the image signal is irradiated from the time when the high-speed optical scanner 3 reaches the time t1, and a projection image is drawn on the projection surface 12.

  The displacement D2 is an example of the displacement of the reflecting surface of the high-speed optical scanner 3 when a drive signal whose frequency is changed is given to the high-speed optical scanner 3 at time t1. The oscillation cycle becomes unstable by changing the frequency of the drive signal. FIG. 2A shows a state in which an unstable state continues until time t4 of frame 2, that is, for a period of tx, and thereafter becomes stable. When the oscillation period of the high-speed optical scanner 3 becomes unstable, the projected image drawn on the projection surface 12 is distorted and the image quality is degraded. Therefore, when changing the frequency, it is necessary to keep the period in which the fluctuation of the oscillation is maintained within a predetermined period.

  FIG. 2B shows a trajectory in which the light beam is scanned during the period of frame 1 in FIG. The light beam is scanned by the high-speed optical scanner 3 in the main scanning direction, that is, the X direction, and is scanned by the low-speed optical scanner 4 in the sub-scanning direction, that is, the Y direction. For the light beam, the light emission timing of the light source 9 is determined by the image modulation unit 2, and the light emission timing is usually determined so that a projected image is projected within the effective region 8a. In FIG. 2B, in order to facilitate understanding, the locus irradiated in the invalid area 8b when the light source 9 emits light continuously is also displayed. A solid line B1 represents a stable projection state before the drive frequency of the high-speed optical scanner 3 is changed, and a solid line B2 represents a state of the projection image after the drive frequency of the high-speed optical scanner 3 is changed. The drive frequency is changed at the drawing start point P3 (corresponding to time t1 in FIG. 2A). When the oscillation of the high-speed optical scanner 3 is disturbed, the length of the trajectory of the light beam in the main scanning direction and the interval of the trajectory change, or the length in the sub-scanning direction, that is, depending on the upper side and the lower side of the effective area 8a. The size of the partitioned screen varies.

  When changing the frequency of the first drive signal for driving the high-speed optical scanner 3, the greater the change in the drive frequency, the longer the time tx in which the oscillation cycle is disturbed. As the time tx becomes longer, the user can recognize the disturbance of the projected image. However, if the fluctuation of the oscillation cycle is short, it is not observed by the user as distortion of the projected image.

  Therefore, the relationship between the phase difference between the phase of the first drive signal detected by the phase comparison unit 7 and the oscillation phase of the high-speed optical scanner 3 and the change width of the frequency to be changed is obtained in advance. Then, when the phase comparison unit 7 detects a phase difference in which the distortion of the projected image continues for a period of about one frame due to the change in frequency, the frequency of the first drive signal is changed by the scanner drive unit 5. be able to. By setting the distortion of the projected image within a period of approximately one frame, it is difficult for the user to recognize the distortion as an image distortion, and the circuit configuration of the signal processing unit 15 can be simplified. In addition, if it is attempted to reduce image distortion within a period of 0.5 frames, for example, a fine phase difference must be detected, the circuit configuration of the signal processing unit 15 becomes complicated, and malfunction due to noise or the like occurs. It becomes easy. Therefore, the period during which the distortion of the projected image continues is preferably approximately 0.5 frame to approximately 1 frame. Thereby, it is difficult for the user to visually recognize, and the phase difference can be easily detected.

  FIG. 3 shows experimental results showing the relationship between the amount of change in the driving frequency of the high-speed optical scanner 3 and the time tx until the oscillation of the reflecting surface is stabilized. The period of one frame is 16.7 msec, and the resonance frequency of the high-speed optical scanner 3 is approximately 30,000 Hz. When the high-speed optical scanner 3 having a resonance frequency of 30,708 Hz is changed from 30,707 Hz to 30,708 Hz by 1 Hz, the time tx is 6.2 msec. When the high-speed optical scanner 3 having a resonance frequency of 30,709 Hz is changed from 30,707 Hz to 30,709 Hz by 2 Hz, the time tx is 18 msec. When the high-speed optical scanner 3 having a resonance frequency of 30,709 Hz is changed from 30,706 Hz to 30,709 Hz by 3 Hz, the time tx is 36 msec. When the high-speed optical scanner 3 having a resonance frequency of 30,709 Hz is changed from 30,699 Hz to 30,709 Hz by 10 Hz, the time tx is 40 msec.

  From the experimental results shown in FIG. 3, when the frequency of the high-speed optical scanner 3 is changed, in order for the fluctuation of the reflection surface to be within approximately one frame period (about 16.7 msec), the frequency change amount is It can be understood that the frequency may be about 2 Hz. Further, in order to make the fluctuation of the swinging of the reflecting surface approximately 0.5 frame period (approximately 8 msec), the frequency change amount may be approximately 1.5 Hz. Therefore, when the phase comparison unit 7 detects a phase difference corresponding to a deviation of about 1.5 Hz to 2 Hz in the resonance frequency of the high-speed optical scanner 3, the scanner driving unit 5 sets the first drive signal to about 1.5 Hz. What is necessary is just to make it change -2Hz.

  In the scanning of the low-speed optical scanner 4, the scanner drive unit 5 outputs the first drive signal with the period for scanning the effective area 8 a as the first scanning period Rx and the period for scanning the invalid area 8 b as the second scanning period Ry. The frequency is changed during the second scanning period Ry during which the invalid area 8b of the projection surface 12 is scanned. For example, when the timing at which the phase comparison unit 7 detects that the phase difference exceeds a predetermined value is the first scanning period Rx in which the low-speed optical scanner 4 scans the effective area 8a, the scanner driving unit 5 Immediately after the optical scanner 4 enters the second scanning period Ry of the invalid area 8b, the frequency of the first drive signal of the high-speed optical scanner 3 is changed. When the timing at which the phase comparison unit 7 detects that the phase difference exceeds a predetermined value is the second scanning period Ry of the invalid region 8b, the scanner driving unit 5 Change the frequency of 3 immediately. Thereby, the distortion of the projected image in the effective area 8a can be reduced.

  Further, when the first drive signal given to the high-speed optical scanner 3 is changed, the projection image projected by the optical scanner is not projected for a period of one frame, and the projection image is distorted by the user. It can be made difficult to be recognized. For example, when the scanner drive unit 5 changes the first drive signal, the image modulation unit 2 is notified of the frequency change, and the image modulation unit 2 stops the light emission of the light source 9 for a period of one frame. In addition, a mask for preventing the light beam from irradiating the ineffective area 8b of the projection surface 12 is provided, and the second drive given to the low-speed optical scanner 4 when the scanner drive unit 5 changes the first drive signal. The signal supply is stopped for a period of one frame, and the light beam is irradiated onto the mask so that the user cannot see it.

  The image modulation unit 2 includes an image memory unit that stores image data to be projected, and an image analysis unit that analyzes the image data stored in the image memory unit. The phase comparison unit 7 detects that the phase difference between the phase of the first drive signal and the oscillation phase exceeds a predetermined value. Then, the image analysis unit detects time change of the image data stored in the image storage or luminance information of the image data. Then, when it is detected that the time change of the image data is small, or when it is detected that the brightness of the projected image is low, the scanner drive unit 5 is notified, and the first drive signal of the high-speed optical scanner 3 is detected. Change the frequency. This makes it difficult for the user to recognize the distortion of the projected image.

  Further, a temperature sensor for detecting the temperature is provided, and the scanner driving unit 5 can be configured to change the driving frequency of the high-speed optical scanner 3 when the temperature around the optical scanner changes abruptly. When the ambient temperature changes rapidly, the resonance point of the high-speed optical scanner 3 changes. Therefore, a relationship between the change in the ambient temperature and the frequency to be changed is determined in advance, and the frequency of the first drive signal is changed when the ambient temperature has a predetermined temperature change. With this configuration, even when the ambient temperature changes abruptly and the resonance point of the high-speed optical scanner 3 fluctuates, the drive frequency can follow this and the distortion of the projected image can be reduced.

  For example, a laser light emitting diode can be used as the light source 9. As the high-speed optical scanner 3, an optical scanner using vibration of a piezoelectric body can be used. A galvanometer mirror can be used as the low-speed optical scanner 4. The projection surface 12 is a screen surface when the image projection device 1 is a projector, and is a retina when the image projection device 1 is a retinal scanning projection device. The swing detection unit 6 may detect a swing state by inputting a signal from a piezoelectric body provided in the vicinity of the swing axis of the high-speed optical scanner 3, or may detect the light scanned from the high-speed optical scanner 3. It may be detected by a beam detector and this detection signal may be input.

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

(Embodiment 1)
FIG. 4 is a functional block diagram showing the image projection apparatus 1 according to the first embodiment of the present invention. The same reference numerals are assigned to the same parts or parts having the same function. As shown in FIG. 4, the image projection apparatus 1 includes a light source 9, a resonance type high-speed optical scanner 3 that scans a light beam emitted from the light source 9 in the main scanning direction, and light scanned from the high-speed optical scanner 3. A low-speed optical scanner 4 that scans the beam in the sub-scanning direction (Y direction) and a signal processing unit 15 that drives them are configured.

  The signal processing unit 15 detects an oscillation state of the image modulation unit 2 that processes an input image signal, a scanner driving unit 5 that supplies a driving signal to the optical scanner, and a high-speed optical scanner 3, and generates an oscillation signal. Temperature information from the temperature sensor 13, the fluctuation detection unit 6 that detects the phase difference by comparing the phase of the driving signal that drives the high-speed optical scanner 3 with the phase of the fluctuation signal, and the phase sensor 7. And a detected temperature processing unit 14 that generates temperature change information. The image modulation unit 2 includes an image signal processing unit 21 that generates a light source drive signal from an image signal, a light source driver 16 that drives the light source 9 based on the light source drive signal, and an image memory that stores the input image signal as image data. Unit 20 and an image analysis unit 17 that performs data analysis of the image data stored in the image memory unit 20. The scanner driving unit 5 generates a driving signal processing unit 22 that generates a driving signal for the scanner, a first driving signal that drives the high-speed optical scanner 3 based on the driving signal, and a second driving signal that drives the low-speed optical scanner 4. A scanner driver 23 is provided.

  The signal processing unit 15 is driven under the control of a control unit (not shown). The control unit includes a CPU, a RAM, a ROM, and the like, and controls the signal processing unit 15 by operating a control program read from the ROM by the CPU using the RAM. Further, for example, the image analysis unit 17 and the detection temperature processing unit 14 are configured by software incorporated in a control program.

  The drive signal processing unit 22 generates a first drive signal having a resonance frequency for driving the resonance type high-speed optical scanner 3 and a second drive signal for driving the low-speed optical scanner 4, and supplies them to the scanner driver 23. The scanner driver 23 sets the offset of the drive signal, supplies the first drive signal and the second drive signal amplified and amplified to the high-speed optical scanner 3 and the low-speed optical scanner 4 respectively. The drive signal processing unit 22 generates a frame synchronization signal and a horizontal synchronization signal and supplies them to the image signal processing unit 21. The image signal processing unit 21 modulates the input image signal based on the frame synchronization signal and the horizontal synchronization signal to generate a light source drive signal. The light source driver 16 drives the light source 9 based on the light source drive signal.

  The fluctuation detection unit 6 receives a detection signal from a fluctuation sensor attached to the high-speed optical scanner 3 or provided near the high-speed optical scanner 3, and amplifies and shapes the detection signal to generate a fluctuation signal. . The phase comparison unit 7 receives the oscillation signal and a drive signal based on the first drive signal given to the high-speed optical scanner 3, compares the phase, determines whether the phase difference exceeds a predetermined value, and determines the frequency. Generate a change notification. The drive signal processing unit 22 and / or the image signal processing unit 21 changes the frequency of the first drive signal for driving the high-speed optical scanner 3 based on the notification of the frequency change, and applies the second drive to the low-speed optical scanner 4. The signal is changed, the analysis of the image analysis unit 17 is started, or the supply of the light source driving signal generated by the image signal processing unit 21 is interrupted.

  FIG. 5 is a schematic perspective view showing an embodiment of the high-speed optical scanner 3 used in the image projector 1 according to the present invention. The high-speed optical scanner 3 includes a reflecting portion 31 formed with a reflecting surface for reflecting light, spring portions 32 and 32 that support the reflecting portion 31 from both sides, and a fixed frame 35 having a shape surrounding the periphery of the reflecting portion 31. And an optical scanning unit 30 including two bifurcated beam portions 33 and 33 for connecting the spring portion 32 and the fixed frame 35, and four piezoelectric elements 37 a and 37 b installed on the two beam portions 33. In addition, the central portion is formed in a concave shape, and is configured by a housing 39 that holds the optical scanning unit 30 by being joined to the fixed frame 35 of the optical scanning unit 30.

  Electrode terminals 36 are formed on the surface of the fixed frame 35 and are electrically connected to the electrodes (not shown) formed on the piezoelectric elements 37 a and 37 b by wiring 34. By applying alternating voltages having opposite phases to the two piezoelectric elements 37a and 37a of the beam portion 33, the two beam portions 33 alternately bend and vibrate in the vertical direction. Due to this vibration, a rotational torque is applied to the spring portion 32, and the reflecting portion 31 swings about the spring portion 32 as the swing axis Z. As a result, the light beam incident on the reflecting portion 31 is converted into a light beam scanned at a predetermined cycle.

  Further, the two piezoelectric elements 37b can be used as swing sensors. When the reflecting portion 31 is swung by vibration of the piezoelectric element 37a, the two piezoelectric elements 37b perform bending vibration in the vertical direction. Due to this bending vibration of the piezoelectric element 37b, a voltage is generated at the electrode terminal. This voltage has a period synchronized with the oscillation of the reflecting portion 31. The fluctuation detection unit 6 receives this voltage generated by the piezoelectric element 37b, performs amplification and waveform shaping, and generates a fluctuation signal.

  In the above embodiment, the swing sensor is the piezoelectric element 37b, but the present invention is not limited to this. As the oscillation sensor, the light beam scanned from the reflection unit 31 is used as a beam detector (hereinafter referred to as BD), and the oscillation detection unit 6 inputs the detection signal of this BD to detect the oscillation state of the high-speed optical scanner 3. You may do it.

(Embodiment 2)
FIG. 9 is an explanatory diagram for explaining a driving method of the image projection apparatus 1 according to the second embodiment of the present invention. The second embodiment is a case where a projection image for a period of one frame is not projected when the drive signal of the high-speed optical scanner 3 is changed. The same portions or portions having the same function are denoted by the same reference numerals.

  In FIG. 9, the horizontal axis is the time axis, and represents the period from frame 1 to frame 4. The bottom row represents the image data D5 of the light source drive signal supplied from the image signal processing unit 21 to the light source 9 and during the period from the drawing start point P3 to the drawing end point P4. The upper stage represents the displacement D3 of the reflecting surface of the low-speed optical scanner 4. The upper stage shows the displacement of the amplitude accompanying the swinging of the reflecting surface of the high-speed optical scanner 3, the solid line displacement D1 is before changing the frequency of the high-speed optical scanner 3, and the broken line displacement D2 is changing the frequency. After that, the oscillation period is unstable, and the solid line D2 ′ is a period in which the oscillation period after the frequency change is stable. The uppermost stage represents the phase difference D4 between the phase of oscillation and the phase of the first drive signal detected by the phase comparison unit 7. Level F1 is a state where there is no phase difference, that is, a state where phase difference is 0, and level F2 changes the frequency of the first drive signal for driving high-speed optical scanner 3 as the resonance point of high-speed optical scanner 3 changes over time. It is a level that should be done. For example, when the driving frequency of the high-speed optical scanner 3 is changed, the phase difference of the level F2 is a phase difference in which the distortion of the projected image accompanying the change lasts for a period of about one frame, for example. It should be noted that the phase difference becomes unstable (indicated by the broken line D7) during approximately one frame in the period of the broken line D2 where the oscillation period of the high-speed optical scanner 3 is unstable. Therefore, it is desirable to set the unstable period so that the phase comparison unit 7 does not notify the frequency change in advance.

  When the resonance point of the high-speed optical scanner 3 changes with time and the phase comparison unit 7 detects that the phase difference D4 between the first drive signal and the oscillation signal reaches the level F2 (P5 in FIG. 9). Timing) and a notification of frequency change are given to the drive signal processor 22. The drive signal processing unit 22 changes the drive frequency of the high-speed optical scanner 3 in the next frame 3 while the low-speed optical scanner 4 is scanning the invalid area 8b. The image signal processing unit 21 gives the light source driver 16 a light source drive signal for stopping the light emission of the light source 9 when receiving a notification that the frequency has been changed from the drive signal processing unit 22. Thereby, the light beam is not projected during the period of the frame 3. Next, in synchronization with the frame synchronization signal, the image signal processing unit 21 supplies the light source drive signal including the image data D5 to the light source driver 16 and resumes drawing the projected image.

  As a result, no image is projected on the projection surface 12 during the period of the frame 3. Thereby, the projection image is not drawn in the period of the frame 3 immediately after the drive frequency of the high-speed optical scanner 3 is changed, so that the distortion of the projection image is hardly visually recognized by the user. Note that the frequency change timing of the first drive signal may be a frame immediately after the phase difference D4 reaches the level F2, or may be a subsequent frame.

(Embodiment 3)
FIG. 6 is an explanatory diagram for explaining a driving method of the image projection apparatus 1 according to the third embodiment of the present invention. In the third embodiment, the scanning of the low-speed optical scanner 4 is stopped for one frame period after the frequency change is notified. The same reference numerals are given to the same parts or parts representing the same functions.

  In FIG. 6, the horizontal axis is the time axis, and represents the period from frame 1 to frame 4. The bottom row represents the displacement D3 associated with the swing of the reflecting surface of the low-speed optical scanner 4. The middle row shows the amplitude displacement associated with the swing of the reflecting surface of the high-speed optical scanner 3, the solid line displacement D1 is before the frequency of the high-speed optical scanner 3 is changed, and the broken line displacement D2 is the frequency changed. The subsequent oscillation period is an unstable period, and the solid line D2 ′ is a period in which the oscillation period after the frequency change is stable. The upper part represents a change in the phase difference D4 detected by the phase comparison unit 7 between the phase of the oscillation vibration and the phase of the first drive signal for driving the high-speed optical scanner 3. The upper vertical axis represents the phase difference, and the level F1 is a state where there is no phase difference between the phase of the first drive signal and the phase of the oscillation vibration, that is, a state where the phase difference is zero. The level F2 is a level at which the resonance point of the high-speed optical scanner 3 changes with time and the frequency of the first drive signal for driving the high-speed optical scanner 3 should be changed. For example, when the driving frequency of the high-speed optical scanner 3 is changed, the phase difference of the level F2 is a phase difference in which the distortion of the projected image accompanying the change lasts for approximately one frame. Note that the phase difference is unstable (indicated by the broken line D7) in approximately one frame indicated by the broken line D2 in which the oscillation period of the high-speed optical scanner 3 is unstable. Therefore, it is desirable to set the unstable period so that the phase comparison unit 7 does not notify the frequency change in advance.

  When the resonance point of the high-speed optical scanner 3 changes with time and the phase comparison unit 7 detects that the phase difference D4 between the first drive signal and the swing signal reaches the level F2, the drive signal processing unit 22 The frequency change notification is given. The drive signal processing unit 22 stops the swinging of the low-speed optical scanner 4 in the next frame 3. That is, the drive signal processing unit 22 sets the second drive signal in which the scanning direction of the light beam of the low-speed optical scanner 4 is retracted to the invalid area 8b. Further, the drive signal processor 22 drives the high-speed optical scanner 3 during the second scanning period of the low-speed optical scanner 4, that is, during the period of scanning the invalid area 8b shown in FIG. The frequency of the second drive signal to be changed is changed.

  As a result, the image of the frame 3 is not projected on the effective area 8a of the projection surface 12. The drive signal processing unit 22 resumes swinging of the low-speed optical scanner 4 from the frame 4. Since one frame immediately after changing the driving frequency of the high-speed optical scanner 3 is not projected onto the effective area 8a, the user hardly sees the distortion of the projected image. Note that the timing of changing the frequency of the second drive signal may be the frame immediately after the phase difference D4 reaches the level F2, or the subsequent frame, but if the operation is performed reliably, The next frame is desirable. Further, as will be described with reference to FIG. 8, by providing the mask portion 24, it is possible to prevent the light beam from being projected onto the invalid region 8b. Further, as described with reference to FIG. 9, the light emission of the light source 9 may be stopped during the period in which the oscillation of the low-speed light scanner 4 is stopped.

(Embodiment 4)
FIG. 7 is an explanatory diagram for describing a driving method of the image projection apparatus 1 according to the fourth embodiment of the present invention. In the fourth embodiment, after the notification of the frequency change is generated, the drive frequency of the high-speed optical scanner 3 is changed immediately after the second scanning period in which the scanning of the low-speed optical scanner 4 scans the invalid area 8b. It is. The same reference numerals are given to the same parts or parts representing the same functions.

  In FIG. 7, the horizontal axis is the time axis, and represents the period from frame 1 to frame 4. The bottom row represents the displacement D3 associated with the swing of the reflecting surface of the low-speed optical scanner 4. The middle row shows the amplitude displacement associated with the swing of the reflecting surface of the high-speed optical scanner 3, the solid line displacement D1 is before the frequency of the high-speed optical scanner 3 is changed, and the broken line displacement D2 is the frequency changed. The subsequent oscillation period is an unstable period, and the solid line D2 ′ is a period in which the oscillation period after the frequency change is stable. The upper part represents a change in the phase difference D4 detected by the phase comparison unit 7 between the phase of the oscillation vibration and the phase of the first drive signal for driving the high-speed optical scanner 3. The upper vertical axis represents the phase difference, and the level F1 is a state where there is no phase difference between the phase of the first drive signal and the phase of the oscillation vibration, that is, a state where the phase difference is zero. The level F2 is a level at which the resonance point of the high-speed optical scanner 3 changes with time and the frequency of the first drive signal for driving the high-speed optical scanner 3 should be changed. For example, when the driving frequency of the high-speed optical scanner 3 is changed, the phase difference of the level F2 is a phase difference in which the distortion of the projected image accompanying the change lasts for approximately one frame. Note that the phase difference is unstable (indicated by the broken line D7) in approximately one frame indicated by the broken line D2 in which the oscillation period of the high-speed optical scanner 3 is unstable. Therefore, it is desirable to set the unstable period so that the phase comparison unit 7 does not notify the frequency change in advance.

  When the resonance point of the high-speed optical scanner 3 changes with time and the phase comparison unit 7 detects that the phase difference D4 between the first drive signal and the swing signal reaches the level F2, the drive signal processing unit 22 A frequency change notification is given. The drive signal processing unit 22 stops the swinging of the low-speed optical scanner 4 in the next frame 3. That is, the drive signal processing unit 22 sets the second drive signal in which the scanning direction of the light beam of the low-speed optical scanner 4 is retracted to the invalid area 8b. Further, the drive signal processing unit 22 changes the frequency of the second drive signal that drives the high-speed optical scanner 3 immediately after the low-speed optical scanner 4 enters the second scanning period, as indicated by the displacement D2. Thereby, since the influence of the unstable period of the oscillation of the high-speed optical scanner 3 can be shortened, the period during which the projected image is distorted can be shortened. As will be described with reference to FIG. 8, by providing the mask portion 24, it is possible to prevent the light beam from being projected onto the invalid region 8b. Further, as described with reference to FIG. 9, the light emission of the light source 9 may be stopped during the period in which the oscillation of the low-speed light scanner 4 is stopped.

(Embodiment 5)
FIG. 8 is a schematic perspective view showing a projection unit of the image projection apparatus 1 according to the fifth embodiment of the present invention. In the fifth embodiment, the light beam is not projected onto the projection surface 12 when the drive of the low-speed optical scanner 4 is interrupted and retracted. The same portions or portions having the same function are denoted by the same reference numerals.

  As shown in FIG. 8, mask portions 24 a and 24 b that block the light beam are provided between the projection optical system 11 and the projection surface 12. As shown in FIG. 6, during the period of the frame 3, the low-speed optical scanner 4 is evacuated and retracted. The low-speed optical scanner 4 retracts at a position where the light beam reflected from the reflecting surface is irradiated outside the effective area 8a where the projection image of the projection surface 12 is projected. Therefore, when the low-speed optical scanner 4 is retracted on the upper side of the invalid area 8b, a mask portion 24a is provided. When the low-speed optical scanner 4 is retracted on the lower side of the invalid area 8b, a mask portion 24b is provided. Cut off. Accordingly, since the light beam is not projected anywhere on the projection surface 12 during the period of the frame 3 in which the drive frequency of the high-speed optical scanner 3 is changed, it is possible to prevent the quality of the projection image from being deteriorated.

  Except for the mask portions 24a and 24b, the configuration is the same as that of the image projection apparatus 1 described in FIG. The mask parts 24 a and 24 b may be provided between the low-speed light scanner 4 and the projection optical system 11. Further, instead of providing the mask portions 24a and 24b as in the fifth embodiment, the image signal processing portion 21 receives a drive stop notification of the low-speed optical scanner 4 from the drive signal processing portion 22 and notifies the light source driver 16 to the light source driver 16. Then, the supply of the light source drive signal may be stopped so that the light beam is not emitted from the light source 9.

(Embodiment 6)
FIG. 10 is an explanatory diagram for explaining a driving method of the image projection apparatus 1 according to the sixth embodiment of the present invention. The difference from FIG. 9 is that the light source drive signal subjected to the blurring process of the projected image is given from the image signal processing unit 21 to the light source driver 16 during the period of frame 3. The other parts are the same as in FIG. The same portions or portions having the same function are denoted by the same reference numerals.

  The image memory unit 20 stores image data for one frame or a plurality of frames. When the image signal processing unit 21 receives an image signal from the outside, the image signal processing unit 21 converts it into image data and temporarily stores it in the image memory unit 20. Usually, the image signal processing unit 21 reads the image data from the stored image memory unit 20, converts it into a light source drive signal, and outputs it to the light source driver 16. The image analysis unit 17 receives a notification of frequency change from the drive signal processing unit 22 in which the drive frequency of the high-speed optical scanner 3 is changed. Then, the image analysis unit 17 reads the image data stored in the image memory unit 20 and performs a blurring process on the projected image. For example, image data corresponding to each dot of the projected image to be drawn is made to interfere with image data corresponding to a dot adjacent thereto, thereby blurring the outline of the projected image. Alternatively, the area of the minimum unit image is enlarged.

  The image analysis unit 17 stores the converted image data after the blurring process in the image memory unit 20. The image signal processing unit 21 receives from the drive signal processing unit 22 a notification of the frequency change in which the drive frequency of the high-speed optical scanner 3 has been changed, reads the converted image data from the image memory unit 20, and generates a light source drive signal To do. As a result, since a projected image with an unclear outline is projected on the frame 3, even if a distortion occurs in the projected image due to a change in the driving frequency, it is difficult for the user to recognize the distortion. In particular, there is little change in luminance or shape of the projected image between the projected image of the frame 3 subjected to the blurring process and the frame 2 and the frame 3 on which the normal projected image is drawn. Can hardly be recognized. Further, if the drawing of the projection image subjected to the blurring process is made one frame period, the user hardly recognizes the distortion of the projection image.

(Embodiment 7)
FIG. 11 is an explanatory diagram for describing a driving method of the image projection apparatus 1 according to the seventh embodiment of the present invention. In the seventh embodiment, after the phase comparison unit 7 notifies the frequency change for changing the drive frequency of the high-speed optical scanner 3, the image analysis unit 17 performs image analysis of the projected image and satisfies a predetermined condition. In addition, this is a driving method for changing the driving frequency of the high-speed optical scanner 3. The same portions or portions having the same function are denoted by the same reference numerals.

  In FIG. 11, the horizontal axis is the time axis and represents the period from frame 1 to frame n + 1. The bottom row represents image data D5 of a light source driving signal given from the image signal processing unit 21 to the light source 9. A projection signal is supplied during the period from the drawing start point P3 to the drawing end point P4. The upper stage represents the displacement D3 of the reflecting surface of the low-speed optical scanner 4. The upper stage represents the displacements D1, D2 and D2 'of the reflecting surface of the high-speed optical scanner 3. The displacement D1 indicated by the solid line is before the frequency of the first drive signal is changed, the displacement D2 indicated by the broken line is a period in which the oscillation cycle is unstable after the frequency is changed, and the solid line D2 ′ is a stable oscillation cycle. It is the period. The uppermost stage represents the phase difference D4 between the phase of oscillation and the phase of the first drive signal detected by the phase comparison unit 7. Level F1 is a state where there is no phase difference, that is, a state where phase difference is 0, and level F2 changes the frequency of the first drive signal for driving high-speed optical scanner 3 as the resonance point of high-speed optical scanner 3 changes over time. It is a level that should be done. The phase difference of level F2 is a phase difference in which, when the driving frequency of the high-speed optical scanner 3 is changed, the distortion of the projected image accompanying the change lasts for a period of approximately one frame, for example. It should be noted that the phase difference becomes unstable (indicated by the broken line D7) during approximately one frame in the period of the broken line D2 where the oscillation period of the high-speed optical scanner 3 is unstable. Therefore, it is desirable to set the unstable period so that the phase comparison unit 7 does not notify the frequency change in advance.

  When the phase comparison unit 7 detects that the resonance point of the high-speed optical scanner 3 changes with time and the phase difference D4 between the first drive signal and the oscillation signal reaches the level F2, the phase comparison unit 7 displays the frequency change notification as an image. The analysis unit 17 is notified. The image analysis unit 17 analyzes the image data stored in the image memory unit 20. Then, the image analysis unit 17 extracts the luminance data from the image data, and changes the frequency when analyzing that the average luminance of the image data in the frame n (n is an integer of 3 or more) is lower than a predetermined value. Notice. The drive signal processing unit 22 receives the change notification and changes the frequency of the high-speed optical scanner 3 between the drawing end point P7 of the n frame and the drawing start point P8 of the frame n + 1, for example. This makes it difficult for the user to recognize the distortion of the projected image because the frequency is changed when the brightness of the projected image is low.

  Further, when the phase comparison unit 7 detects that the resonance point of the high-speed optical scanner 3 has changed with time and the phase difference D4 has reached the level F2, the phase comparison unit 7 notifies the image analysis unit 17 of a frequency change notification. The image analysis unit 17 reads the image data stored in the image memory unit 20, and notifies the change when analyzing that the change amount of the image data between frames is smaller than a predetermined amount from the image data. . The drive signal processing unit 22 receives the change notification and changes the frequency of the high-speed optical scanner 3 during the scanning period of the invalid area 8b of the frame n + 1. This makes it difficult for the user to recognize the distortion of the projected image because the brightness change of the projected image is small.

(Embodiment 8)
FIG. 12 is an explanatory diagram for describing a driving method of the image projection apparatus 1 according to the eighth embodiment of the present invention. In the eighth embodiment, the driving frequency of the high-speed optical scanner 3 is changed when the ambient temperature change exceeds a predetermined temperature change. The same portions or portions having the same function are denoted by the same reference numerals.

  In FIG. 12, the horizontal axis is the time axis, and represents the period from frame 1 to frame 4. The lowermost stage displacement D1 represents the amplitude accompanying the oscillation of the low-speed optical scanner 4. The middle-stage displacements D1, D2, and D2 ′ represent the amplitudes associated with the oscillation of the high-speed optical scanner 3, the solid-line displacement D1 is before the frequency of the high-speed optical scanner 3 is changed, and the broken-line displacement D2 is the frequency. Is a period in which the oscillation period after the change is unstable, and a solid line D2 ′ is a period in which the oscillation period after the frequency change is stable. The upper stage shows a phase difference D4 between the phase of the oscillation detected by the phase comparator 7 and the phase of the first drive signal. Level F1 is a state where there is no phase difference, that is, a state where phase difference is 0, and level F2 changes the frequency of the first drive signal for driving high-speed optical scanner 3 as the resonance point of high-speed optical scanner 3 changes over time. It is a level that should be done. The uppermost temperature difference D6 represents the temperature difference D6 detected by the detected temperature processing unit 14. Level E1 is a state in which the ambient temperature does not change during a predetermined period, that is, a state in which the temperature change is 0 °. The level E2 is a temperature change level at which the ambient temperature changes and the frequency of the first drive signal for driving the high-speed optical scanner 3 should be changed. For example, when the driving frequency of the high-speed optical scanner 3 is changed, the temperature difference of the level E2 is a temperature difference in which the distortion of the projected image accompanying the change lasts for approximately one frame.

  When the ambient temperature changes and the detected temperature processing unit 14 detects that the temperature difference D6 between the first drive signal and the swing signal reaches the level E2, the drive signal processing unit 22 is notified of the frequency change. give. The drive signal processing unit 22 changes the frequency of the second drive signal for driving the high-speed optical scanner 3 at the initial stage of the frame 3 as indicated by the displacement D2.

  As a result, even when the ambient temperature changes suddenly and the resonance point of the high-speed optical scanner 3 changes, the drive signal is intermittently changed to match the frequency to the resonance point, so the power consumption of the high-speed optical scanner 3 is reduced. This can reduce the increase in the mechanical load on the high-speed optical scanner 3. It should be noted that the phase difference becomes unstable (indicated by the broken line D7) during approximately one frame in the period of the broken line D2 where the oscillation period of the high-speed optical scanner 3 is unstable. Therefore, it is desirable to set the unstable period so that the phase comparison unit 7 does not notify the frequency change in advance.

  As described above, in the second to eighth embodiments, the driving method of the image projection apparatus 1 of the present invention has been described. However, it is obvious that these driving methods can be combined, and the driving method combining these is also the present method. Included in the invention. In the embodiment described above, the example in which the frequency is changed in the second scanning period in which the low-speed optical scanner 4 scans the invalid area 8b after the phase difference D4 reaches the level F2 has been described. Instead of this, it is not always preferable to perform correction as effectively as possible. However, after the phase difference D4 reaches the level F2, it is the first scanning period during which the low-speed optical scanner 4 scans the effective area 8a. The frequency may be changed during the period when the scanning of the optical scanner 3 scans the invalid area 8b, and the light emission from the light source 9 may be stopped approximately one frame in synchronization with this. In the above description, since the change in the frequency and the change in the phase correspond to some extent, it is possible to determine whether the correction to increase or decrease the frequency according to which direction the phase shifts. Of course.

(Embodiment 9)
FIG. 13 is a schematic configuration diagram of an image projection apparatus 1 according to the ninth embodiment of the present invention. The ninth embodiment is a retinal scanning image projection apparatus. The same portions or portions having the same function are denoted by the same reference numerals.

  As shown in FIG. 13, the image projection apparatus 1 directly forms an image on the retina 60 of the user's eyeball 58. Video light emitted from the B laser 47 that emits blue light, the G laser 48 that emits green light, and the R laser 49 that emits red light is converted into parallel light by the collimating optical system 50 and synthesized by the dichroic mirror 51. The light is condensed by the coupling optical system 52 and is incident on the optical fiber 59. The image light emitted from the optical fiber 59 is applied to the mirror section 67 of the high-speed optical scanner 3 through the second collimating optical system 53. The mirror unit 67 is driven by the first drive signal to swing, and scans the reflected light in the main scanning direction. The image light scanned in the main scanning direction is applied to the low-speed optical scanner 4 composed of a galvanometer mirror through the first relay optical system 55. The mirror surface of the galvanometer mirror is swung by a magnetic field, and the reflected light is scanned in the sub-scanning direction. The image light reflected from the galvanometer mirror is imaged on the retina 60 of the eyeball 58 through the first lens 63a and the second lens 63b constituting the second relay optical system. In addition, although it has comprised so that all the light beams may pass through the center of a pupil, the structure converged so that each light beam may be settled in a pupil may be sufficient. The beam detector (BD) 40 detects the light scanned from the high-speed optical scanner 3 and detects the swinging state of the mirror unit 67.

  The signal processing unit 15 inputs a video signal and uses a light source driving signal corresponding to blue (B), green (G) and red (R) as a light source driver, a B laser driving circuit 44, and a G laser driving circuit. 45 and the R laser drive circuit 46 respectively. The B laser 47 emits a B-color laser beam whose light intensity is modulated based on a drive signal from the B laser drive circuit 44. Similarly, the G laser 48 and the R laser 49 emit laser light of each color whose light intensity is modulated based on each image signal. The signal processing unit 15 outputs the first drive signal and the second drive signal synchronized with the image signal to the high-speed optical scanner 3 and the low-speed optical scanner 4. The mirror unit 67 swings in the main scanning direction by the first drive signal. The reflection surface of the low-speed optical scanner 4 is swung in the sub-scanning direction by the second drive signal. The oscillation in this case is based on the resonance oscillation of the mirror part 67.

  Since the signal processing unit 15 is the same as that described in the first embodiment, the description thereof is omitted. In the tenth embodiment, the BD 40 is used as the swing sensor. The swing detection unit 6 receives a signal from the BD 40 and generates a swing signal.

1 is a schematic configuration diagram of an image projection apparatus according to an embodiment of the present invention. It is explanatory drawing of the image projector which concerns on embodiment of this invention. It is an experimental result showing the relationship between the variation | change_quantity of the drive frequency of a high-speed optical scanner, and the time tx until rocking | fluctuation is stabilized of the illuminating device which concerns on embodiment of this invention. It is a functional block diagram of the image projector which concerns on embodiment of this invention. It is a typical perspective view of the high-speed optical scanner used for the image projector which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. 1 is a schematic configuration diagram of an image projection apparatus according to an embodiment of the present invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. It is explanatory drawing for demonstrating the drive system of the image projector which concerns on embodiment of this invention. 1 is a schematic configuration diagram of an image projection apparatus according to an embodiment of the present invention. It is a block diagram of a conventionally well-known image projection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image projector 2 Image modulation part 3 High-speed optical scanner 4 Low-speed optical scanner 5 Scanner drive part 6 Swing detection part 7 Phase comparison part 8a Effective area 8b Invalid area 9 Light source 10 Relay lens 11 Projection optical system 12 Projection surface 13 Temperature sensor 14 Detection temperature processing unit 15 Signal processing unit

Claims (10)

An image modulation unit that modulates a light beam from a light source according to an image signal, an optical scanner that scans the light beam by a reflecting surface that oscillates the light beam to form a projection image, and a drive signal that oscillates the optical scanner A scanner driving unit that generates a high-speed optical scanner that scans in the main scanning direction and a low-speed optical scanner that scans in the sub-scanning direction, and the scanner driving unit includes the high-speed optical scanner. In an image projection device that generates a first drive signal to be driven,
A swing detector for detecting the swing state of the high-speed optical scanner, and a phase comparator for comparing the phase of the first drive signal with the detected swing phase;
When the phase difference between the phase of the first drive signal and the detected oscillation phase exceeds a predetermined value, the scanner drive unit changes the frequency of the first drive signal. A characteristic image projection apparatus.   The predetermined value is a phase difference that eliminates the distortion of the projected image that occurs when the scanner driving unit applies the first drive signal of the changed frequency to the high-speed optical scanner in a period of approximately one frame. The image projection apparatus according to claim 1. In response to a change in the frequency of the first drive signal,
The image projection apparatus according to claim 1, wherein a projection image based on the light beam is not projected for a period of one frame of a projection image projected by the optical scanner. In response to a change in the frequency of the first drive signal,
The image projection device according to claim 1, wherein the image modulation unit performs a blurring process on the projected image for a period of one frame of the projected image. One scanning period of the low-speed optical scanner has a first scanning period that scans an effective area on which the projection image is projected, and a second scanning period that scans an invalid area that is outside the effective area,
5. The image according to claim 1, wherein the change of the frequency is performed after the phase difference exceeds the predetermined value and during the second scanning period. 6. Projection device.   The image projection apparatus according to claim 5, wherein the frequency change is performed immediately after the low-speed light scanner scans in the second scanning period. A mask portion is provided to block the scanned light beam from being applied to an ineffective area that is an area outside the area where the projection image is projected;
The optical scanner driving unit stops the oscillation of the low-speed optical scanner for a period of one frame when the frequency of the first drive signal is changed. Image projector. A temperature sensor for detecting the temperature;
The frequency change is performed when a detected temperature exceeds a predetermined temperature change, or when the phase difference exceeds the predetermined value. The image projector of any one of these. An image memory unit for storing image data based on the image signal; and an image analysis unit for analyzing the stored image data;
The frequency change is performed when the image analysis unit detects that a temporal change in the stored image data is small. The image projection apparatus described. An image memory unit that stores image data based on the image signal; and an image analysis unit that analyzes the stored image data;
10. The frequency change according to claim 1, wherein the frequency change is performed when the image analysis unit detects that the projection brightness of the stored image data is low. Image projection device.

Images