JP2008116678A - Device and method for display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To excellently display an image uninfluenced by a temperature rise or the like of a mirror when the image is projected on a screen by using the resonant scan mirror. <P>SOLUTION: The display device is provided with: a light source 2 which emits laser light having a prescribed wavelength and the scan mirror 18 which reflects and reciprocally scans the first laser light on the screen 4. Further, a projector apparatus 100 is provided with: an amplitude detection part 36 which detects the resonant oscillation of the scan mirror 18; an accumulator 32 which corrects a driving signal for driving the scan mirror 18 by an amplitude detection signal; and an electrostatic actuator 34 which resonantly oscillates the scan mirror 18 by the corrected driving signal and controls the amplitude of the resonant oscillation of the scan mirror 18. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device and method suitable for application to a projector device that scans using, for example, a scanning device that performs reciprocal scanning of a laser beam emitted from a laser light source and displays an image on a screen.

  Conventionally, in order to project an image on a screen, for example, an LCD (Liquid Crystal Display) type projector apparatus has been put into practical use. The LCD projector device transmits or reflects light from a light source by an LCD panel that displays an image, and projects the transmitted or reflected light on a screen. On the other hand, in recent years, a technique for performing two-dimensional scanning on a screen using a resonant optical scanner such as a MEMS (Micro Electro Mechanical Systems) device has been proposed in order to reduce the size of a projector apparatus. In this case, laser light is used as a light source, the laser light is directly modulated with an image signal, and then the modulated laser light is two-dimensionally scanned with a resonance type optical scanner.

  As a MEMS device capable of performing two-dimensional scanning, a MEMS mirror that reflects laser light is provided, and the MEMS mirror is resonated and oscillated between a main axis and a sub axis that are orthogonal to each other, thereby projecting laser light onto a screen. MEMS scanners have been put into practical use. Conventionally, in a biaxial MEMS scanner, a minute MEMS mirror is held by a hinge portion supported in the main axis and sub-axis directions.

Patent Document 1 describes a technique for displaying an image on a screen using a semiconductor laser.
Japanese Patent Laid-Open No. 2002-357883

  By the way, when an image is projected using a biaxial MEMS scanner, there is a drawback that the size of the image changes depending on the brightness of the image. This is considered to be because the remaining light that has not been reflected is absorbed by the MEMS mirror itself even if the light is reflected by the MEMS mirror. The reflectivity of the MEMS mirror does not reach 100%, and a certain amount of light is absorbed by the mirror itself. And since the amount of heat absorbed by the MEMS mirror changes depending on the amount of incident light, that is, the brightness of the screen, the temperature of the MEMS mirror changes.

  When the temperature of the MEMS mirror changes, the rigidity of the hinge portion supporting the MEMS mirror changes slightly, so that the amplitude of the MEMS mirror changes even when the same driving voltage is applied. Therefore, when the mirror is driven with a constant driving force, the deflection angle of the MEMS mirror is changed by changing the brightness of the screen by strengthening the laser beam. For this reason, there is a drawback that the brightness of the screen also changes.

  The present invention has been made in view of such a situation, and an object thereof is to display an image satisfactorily when an image is projected onto a screen using a projector device.

  The present invention is applied to a case where a first laser beam having a predetermined wavelength, which is modulated based on a supplied image signal, is emitted, and the first laser beam is reflected by a reflection unit and reciprocally scanned on a screen. . Resonance vibration performed by the reflection unit is detected, and a drive signal for driving the reflection unit is corrected based on the detection signal. Then, the reflection unit is caused to resonate with the corrected drive signal, and the amplitude of the resonance vibration performed by the reflection unit is controlled.

  By doing in this way, it became possible to control the amplitude of the resonant vibration performed by the reflecting portion to be constant.

  According to the present invention, since the amplitude of the resonance vibration performed by the reflection unit can be controlled to be constant, the screen size projected onto the screen is kept constant regardless of the screen brightness (laser beam intensity). Can keep. For this reason, there exists an effect that an image can be favorably displayed on a screen.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the present invention is applied to a projector apparatus that displays an image by scanning a laser beam emitted from a light source on a screen.

  First, an example of the overall configuration of the projector apparatus 100 will be described with reference to FIG. The projector device 100 includes an image signal supply unit 1 that performs conversion processing on an image signal. The projector apparatus 100 supplies the image signal converted by the image signal supply unit 1 to a light source 2 that emits a laser beam, and performs a modulation process on the laser beam. The light source 2 is a semiconductor laser device, for example. The laser beam emitted from the light source 2 is reflected by the two-axis MEMS scanner 10 configured to scan with two axes of a main axis and a sub-axis orthogonal to the main axis. The laser beam reflected by the two-axis MEMS scanner 10 is projected onto a two-dimensional plane screen 4 via a projection optical system 3 composed of a lens, a mirror, etc., and displays an image.

  The biaxial MEMS scanner 10 includes a scan mirror on the main axis, and performs horizontal scanning and vertical scanning. The scanning direction 7 of the main axis is the horizontal direction of the screen 4, and horizontal resonance vibration of the sine wave 5 is performed. This horizontal resonance vibration derives a necessary frequency range from the horizontal frequency of the image signal, but is not synchronized with the horizontal frequency of the image signal, and is determined by factors such as the dimensions and temperature of the biaxial MEMS scanner 10. The scanning direction 8 of the secondary axis is the vertical direction of the screen 4, and the vertical resonance vibration of the sawtooth wave 6 is performed. This vertical resonance vibration is performed in synchronization with the vertical frequency of the image signal. The projector apparatus 100 of this example has a function of two-dimensionally scanning the laser beam emitted from the light source 2 with the horizontal vibration and the vertical vibration of the image by the two-axis MEMS scanner 10.

  Next, an example of the external configuration of the biaxial MEMS scanner 10 will be described with reference to FIG. The biaxial MEMS scanner 10 includes a scan mirror 18 that reflects a laser beam, a rectangular inner frame portion 19 that supports the scan mirror 18, a rectangular outer frame portion 20 that supports the inner frame portion 19, and an inner frame. It is comprised with the sub-axis electromagnetic drive magnets 11a and 11b which drive the part 19 electromagnetically. The scan mirror 18 and the inner frame portion 19 oscillate around the directions orthogonal to each other. In this example, the axis that vibrates the inner frame portion 19 is the secondary axis, and the axis that vibrates the scan mirror 18 is the main axis. The countershaft electromagnetic drive magnets 11 a and 11 b are configured to sandwich the outer frame portion 20.

  The outer frame portion 20 is formed with auxiliary shaft torsion bars 12 a and 12 b that support the inner frame portion 19 in the direction of the rotation axis of the inner frame portion 19. The countershaft torsion bars 12 a and 12 b are members that support the inner frame portion 19 so as to be twisted to the left and right by a predetermined angle, and are integrally formed with the outer frame portion 20.

  In the vicinity of the apex in the diagonal direction of the outer frame portion 20, auxiliary shaft electrodes 14a and 14b serving as current input / output portions are provided. A conductive wire connected to the countershaft electrode 14 a is laid on the inner frame portion 19 via a countershaft torsion bar 12 a that supports the inner frame portion 19. The conducting wire disposed in the inner frame portion 19 forms the secondary shaft electromagnetic drive coil 13 of several turns along the edge of the inner frame portion 19. And a conducting wire is connected to the countershaft electrode 14b via the countershaft torsion bar 12b.

  The inner frame portion 19 generates an electromagnetic force when an AC voltage (driving frequency is 60 Hz, for example) is applied to the auxiliary shaft electrodes 14a and 14b from an AC power source (not shown), and the auxiliary shaft torsion bar 12a. , 12b is vibrated by the twisting action. The driving method of the secondary shaft is electromagnetic, the vibration method is non-resonant, and the vibration waveform is, for example, a sawtooth wave. The vibration waveform may be a triangular wave.

  The outer frame portion 20 includes main shaft electrodes 15a and 15b in the vicinity of the apex in the diagonal direction different from the diagonal direction of the sub shaft electrodes 14a and 14b. A conductive wire (not shown) is connected from the main shaft electrode 15 a to the inner frame portion 19 via a sub shaft torsion bar 12 b that supports the inner frame portion 19.

  The inner frame portion 19 is provided with main shaft torsion bars 16 a and 16 b that support the scan mirror 18 in the direction of the rotation axis of the scan mirror 18. The main shaft torsion bars 16 a and 16 b are members that support the scan mirror 18 so as to be twisted to the left and right by a certain angle, and are integrally formed with the inner frame portion 19. On both sides of the main shaft torsion bars 16a and 16b, rotation-side electrodes 17a and 17b, which are fine electrodes, are formed like comb teeth.

  Further, a fine electrode fixed side electrode having a comb-like shape is formed on the inner frame portion 19 so as to mesh with the respective rotation side electrodes 17a and 17b. The conducting wire connected to the inner frame portion 19 is connected to the main shaft electrode 15b via the sub shaft torsion bar 12b.

An almost elliptical scan mirror 18 is an SOI (Silicon On Insulator) substrate in which an oxide layer such as silicon dioxide (SiO ₂ ) and a semiconductor film such as silicon are sequentially laminated on the surface of a holding substrate made of, for example, silicon. From the semiconductor film, the holding substrate and the oxide layer are selectively removed. The flat surface of the semiconductor film is used as the scan mirror 18 that becomes the light incident surface. A reflective film such as aluminum (Al) or gold (Au) is formed on the flat surface of the scan mirror 18 to increase the reflectance.

  An AC voltage (resonance frequency is set to 16 kHz, for example) substantially equal to the resonance frequency of the scan mirror 18 or an integral multiple thereof is applied to the spindle electrodes 15a and 15b from an AC power source (not shown). 18 drives. The main shaft torsion bars 16a and 16b vibrate due to the twisting action. The driving method of the main shaft is an electrostatic method, the vibration method is a resonance method, and the vibration waveform is a sine wave.

  Next, an example of the internal configuration of the biaxial MEMS scanner 10 that drives the scan mirror 18 and the inner frame portion 19 will be described with reference to FIG.

  The image signal converted by the image signal supply unit 1 is supplied to the light source 2, and the laser beam output from the light source 2 is subjected to modulation processing. Then, the modulated laser beam is emitted and reflected by the scan mirror 18 configured in the biaxial MEMS scanner 10. The laser beam reflected by the scan mirror 18 is projected onto the screen 4 via the projection optical system 3.

  In addition, the image signal supply unit 1 supplies a reference (voltage) signal for driving the scan mirror 18 and the inner frame unit 19 to the adder 32 in synchronization with the image signal supplied to the light source 2. The adder 32 performs a correction process of adding a servo signal voltage supplied from an amplitude detection unit 36 (to be described later) and a drive signal voltage supplied from the image signal supply unit 1 to obtain a drive signal. However, in the case of this example, the adder 32 performs a process of subtracting the servo voltage from the drive signal. The signal corrected by the adder 32 is supplied to the integrator 33. A drive signal whose frequency is corrected by the signal integrated by the integrator 33 is supplied to the electrostatic actuator 34 that drives the scan mirror 18 and the inner frame portion 19, and the scan mirror 18 and the inner frame which are electrostatic drive MEMS devices. The drive amplitude of the unit 19 is controlled. The electrostatic actuator 34 has a function of controlling the resonance vibration of the scan mirror 18 and the inner frame portion 19 and controlling the amplitude of the resonance vibration performed by the scan mirror 18 and the inner frame portion 19. A sensor 35 for detecting the amplitude of the scan mirror 18 and the inner frame portion 19 is built in the electrostatic actuator 34. The sensor 35 detects the electrostatic capacity accumulated in the capacitor. The sensor 35 generates a detection signal from the detected capacitance and supplies the detection signal to the amplitude detection unit 36 that analyzes the detection signal.

  The amplitude detector 36 analyzes the amplitude from the detection signal. The amplitude detector 36 generates a servo signal for controlling the resonance vibration of the scan mirror 18 and the inner frame 19 and supplies the servo signal to the adder 32 in order to make the brightness of the image projected on the screen 4 constant. The adder 32 inverts the voltage of the servo signal and adds it to the voltage of the drive signal supplied from the image signal supply unit 1. The adder 32 is set with reference values for making the amplitude and drive frequency of the scan mirror 18 and the inner frame portion 19 constant, and supplies a drive signal obtained by adding servo signals to the integrator 33. In this way, feedback control of the entire system is performed.

  Next, an operation example of the biaxial MEMS scanner 10 will be described. The biaxial MEMS scanner 10 of this example detects the deflection angle of the scan mirror 18 and the inner frame portion 19 with the sensor 35, extracts amplitude information therefrom, and sets the reference value so that the value becomes a reference value. Feedback control is performed based on the difference from the value. In order to make the amplitudes of the scan mirror 18 and the inner frame portion 19 constant regardless of the amount of heat applied to the biaxial MEMS scanner 10, the correction band of the drive signal for driving the resonance is the temperature time constant of the scan mirror 18. It is necessary to make it higher than the band corresponding to.

Incidentally, there are the following two types of operations of the electrostatic actuator 34.
(1) When the drive frequency is increased from the starting frequency, the amplitude increases. At this time, the amplitudes of the scan mirror 18 and the inner frame portion 19 substantially depend only on the drive frequency, and do not depend on the drive voltage. For this reason, the output of the integrator 33 needs to output a signal having a polarity for increasing the driving frequency when the detected amplitude falls below the reference value.
(2) When the drive frequency is lowered from the starting frequency, the amplitude is increased. At this time, the amplitude of the scan mirror 18 and the inner frame portion 19 depends on both the drive frequency and the drive voltage, so that the output of the integrator 33 is detected. When the amplitude falls below the reference value, it is necessary to output a signal with a polarity that lowers the driving frequency or a signal with a polarity that increases the driving voltage.

<Capacitance detection method>
In the projector apparatus 100, a capacitance detection method detected on the scan mirror 18 will be described with reference to FIGS. The electrostatic capacity detection method is a technique for detecting the amplitudes of the scan mirror 18 and the inner frame portion 19 based on a change in the capacity of the electrostatic actuator 34 used for driving.

  First, an internal configuration example of the electrostatic actuator 34 will be described with reference to FIG. An actuator drive voltage unit 34a that drives the electrostatic actuator 34 supplies a predetermined drive voltage. One end of the actuator drive voltage unit 34a is grounded, and the other end is connected to one end of the first switch 34b. One end of the second switch 34c is grounded, and the other end is connected to the other end of the first switch 34b. The other end of the first switch 34b and the other end of the second switch 34c are connected to a capacitor 34d. Further, the capacitor 34 is connected to the capacitor 34f. A third switch 34e is connected in parallel with the capacitor 34f. The capacitor 34d and the inverting input terminal of the operational amplifier 34g are connected. The operational amplifier 34g is connected in parallel with the capacitor 34f. The non-inverting input terminal of the operational amplifier 34g is grounded, and a drive voltage is output from the operational amplifier 34g via the output unit 34h. Here, the third switch 34e, the capacitor 34f, and the operational amplifier 34g are used as the sensor 35.

  Next, an operation example of the electrostatic actuator 34 will be described with reference to FIG. The operation waveform of the electrostatic actuator 34 vibrates at a constant period as shown in FIG. FIG. 5B is an example of a driving waveform of the first switch 34b. The first switch 34b is turned on and off in synchronization with the drive voltage supplied from the actuator drive voltage unit 34a. FIG. 5C shows an example of a driving waveform of the second switch 34c. The second switch 34c is switched off and on in synchronization with the on and off of the first switch 34b. FIG. 5D shows an example of the driving waveform of the third switch 34e. When the second switch 34c is turned on, the third switch 34e is turned off, and immediately before the second switch 34c is turned off, the third switch 34e is turned on.

  Thus, the electrostatic actuator 34 is controlled by the first switch 34b. Then, in synchronization with the first switch 34b, the second switch 34c and the third switch 34e are controlled to calculate the output. The output is sampled and held at a later timing (not shown), and the value is compared with a reference value.

  Next, an operation waveform and a drive waveform of the electrostatic actuator 34, and an example of the capacitance will be described with reference to FIG. FIG. 6A shows an example of an operation waveform of the electrostatic actuator 34 with the vertical axis representing amplitude and the horizontal axis representing time. FIG. 6B shows an example of a driving waveform of the electrostatic actuator 34 with the vertical axis representing amplitude and the horizontal axis representing time. FIG. 6C shows an example in which the vertical axis represents capacitance and the horizontal axis represents time.

  6A and 6B show that when the amplitude of the operation waveform of the electrostatic actuator 34 becomes 0, the drive waveform of the electrostatic actuator 34 is switched from on to off. Further, when the amplitude of the operation waveform of the electrostatic actuator 34 takes a positive extreme value, it is indicated that the drive waveform of the electrostatic actuator 34 is switched from on to off. Further, it is indicated that when the amplitude of the operation waveform of the electrostatic actuator 34 takes a negative extreme value, the drive waveform of the electrostatic actuator 34 is switched from OFF to ON.

  6A and 6C show that when the amplitude of the operation waveform of the electrostatic actuator 34 becomes 0, charges are accumulated and the capacity is maximized. Further, it is indicated that the capacitance becomes 0 when the amplitude of the operation waveform of the electrostatic actuator 34 becomes maximum or minimum.

  Since the voltage is applied to the electrostatic actuator 34 only in a part of one period, the sensor 35 detects the capacitance at a certain timing in this part. And it controls so that the capacity | capacitance which the sensor 35 detected becomes constant. In order to detect the capacitance, for example, the current change of the electrostatic actuator 34 may be integrated by a capacitor as shown in FIG.

  According to the first embodiment described above, it is possible to control the amplitudes of the scan mirror 18 and the inner frame portion 19 by changing the capacitance detected by the sensor 35. At this time, feedback control is performed so as to return to the normal amplitude by comparing the normal amplitude and the amplitude where the abnormality has occurred. For this reason, even when an image is projected using laser beams having different luminances, the size of the image displayed on the screen 4 does not change, and the predetermined screen size can be easily maintained. There is.

  Next, a configuration example of the projector device according to the second embodiment when a sensor is installed in the biaxial MEMS scanner 10 will be described with reference to FIGS. The present embodiment is also an example applied to the projector apparatus 200 that scans the laser beam emitted from the light source on the screen 4 and displays an image. Since the external configuration example of the projector device 200 is the same as that of the first embodiment, detailed description thereof is omitted.

  First, an example of the internal configuration of the biaxial MEMS scanner 10 that drives the scan mirror 18 and the inner frame portion 19 will be described with reference to FIG. An example of the internal configuration of the biaxial MEMS scanner 10 is substantially the same as that of the first embodiment described above. However, the difference is that a sensor 52 for detecting the amplitude of resonance vibration performed by the scan mirror 18 and the inner frame portion 19 is provided separately from the electrostatic actuator 51. The sensor 52 is configured to detect the amplitude of resonance vibration of the scan mirror 18 and the inner frame portion 19, generate a detection signal, and supply the detection signal to the amplitude detection portion 36.

<Piezo gyro system>
First, a piezo gyro system applied to the sensor 52 will be described with reference to FIG. FIG. 8 is a diagram illustrating an example of a gyroscope. In the piezo gyro system, a reciprocating object is used for a gyroscope. The gyroscope 50 is formed of a rectangular parallelepiped-shaped Elinvar alloy with little expansion and contraction in the axial directions (z-axis) of the main shaft torsion bars 16a and 16b and the sub shaft torsion bars 12a and 12b. The vibration direction (x axis) is taken in the direction perpendicular to the z axis, and the detection direction (y axis) is taken in the direction perpendicular to the x axis and the y axis. The gyroscope 50 is supported by a support wire 55 formed in the y-axis direction. In the x-axis direction of the gyroscope 50, a vibrating piezoelectric ceramic 53 that detects vibration is formed. On the other hand, a detecting piezoelectric ceramic 54 for detecting Coriolis force is formed in the y-axis direction of the gyroscope 50.

When an AC voltage is applied to the vibrating piezoelectric ceramic 53, the gyroscope 50 is excited by bending vibration. When a rotational force is generated around the z-axis, a Coriolis force proportional to the rotational force can be detected as a voltage by the detecting piezoelectric ceramic 54. With the detected voltage, the amplitudes of the scan mirror 18 and the inner frame portion 19 can be obtained, and feedback control can be performed.
<Magnetic resistance detection method>
Next, a magnetoresistive detection method applied to the sensor 52 will be described with reference to FIG. FIG. 9 is a diagram illustrating an installation example of the magnetoresistive sensor. In the magnetoresistive detection method, magnetoresistive sensors (also referred to as MR sensors) 61 a and 61 b that are magnetoresistive detection elements are formed in a direction orthogonal to the main axis direction of the scan mirror 18. Then, magnets 62 a and 62 b are placed on the inner frame portion 19 which is a fixed portion outside the scan mirror 18. The magnetoresistive sensor 61a and the magnet 62a are formed to face each other. Similarly, the magnetoresistive sensor 61b and the magnet 62b are formed to face each other.

  When the scan mirror 18 vibrates, the magnetic field formed by the magnets 62a and 62b changes. And the magnetoresistive sensors 61a and 61b take out the fluctuation | variation of the output accompanying the change of a magnetic field. At this time, it is necessary to extract the fundamental wave component from the output waveform including the higher-order component and perform control with the amplitude. As a method of extracting the fundamental wave component, there is a method of obtaining a correlation coefficient with a reference sine wave using a narrow passband filter. Thereafter, the envelope detection is performed to detect the amplitude and perform feedback control. Although not shown, it is possible to detect the amplitude of the inner frame portion 19 by installing a magnetoresistive sensor in the inner frame portion 19 and perform feedback control.

  According to the second embodiment described above, the sensor 35 can reliably grasp the amplitudes of the scan mirror 18 and the inner frame portion 19. For this reason, the fluctuation | variation which arises in the amplitude of the scan mirror 18 and the inner frame part 19 by absorbing a laser beam with high brightness | luminance is detectable. At this time, feedback control is performed so as to return to the normal amplitude by comparing the normal amplitude and the amplitude where the abnormality has occurred. For this reason, even when an image is projected using laser beams having different luminances, there is an effect that the size of the image displayed on the screen 4 is not changed and the predetermined screen size can be easily maintained. .

  Next, a configuration example of the projector device according to the third embodiment when a sensor is installed outside the biaxial MEMS scanner 10 will be described with reference to FIGS. This embodiment is also an example applied to the projector device 300 that scans the laser beam emitted from the light source on the screen 4 and displays an image.

<Photodetector method>
First, an external configuration example of the projector apparatus 300 will be described with reference to FIG. The projector device 300 includes split photodetectors as external sensors at the top, bottom, left and right ends of the screen 4. At the left end of the screen 4, light receiving elements 71 </ b> L and 71 </ b> R composed of a photodetector or the like are provided. In addition, at the right end of the screen 4, light receiving elements 72L and 72R are provided. In addition, light receiving elements 73U and 73D are provided at the upper end of the screen 4. In addition, at the lower end of the screen 4, light receiving elements 74U and 74D are provided. In the following description, adjacent light receiving elements are also referred to as divided light receiving elements. Since an external configuration example other than the light receiving element of the projector device 300 is the same as that of the second embodiment, detailed description thereof is omitted.

  Next, an example of the internal configuration of the biaxial MEMS scanner 10 that drives the scan mirror 18 and the inner frame portion 19 will be described with reference to FIG. An example of the internal configuration of the biaxial MEMS scanner 10 is almost the same as that of the second embodiment described above. However, the difference is that light receiving elements 71L, 71R, 72L, 72R, 73U, 73D, 74U, and 74D, which are constituted by a split photo detector (PD) as an external sensor, are provided at the top, bottom, left and right ends of the screen 4. . The light receiving elements 71L, 71R, 72L, 72R, 73U, 73D, 74U, and 74D detect the edge of the amplitude of the laser beam reflected by the resonance vibration of the scan mirror 18 and the inner frame portion 19, and generate a detection signal. The amplitude detection unit 75 is configured to be supplied. Since an internal configuration example other than the light receiving element of the projector device 300 is the same as that of the second embodiment, detailed description thereof is omitted.

  Here, an example of the internal configuration of the amplitude detector 75 will be described with reference to FIG. The detection signal input from each input unit is a signal indicating the screen end of the screen 4. The detection signal output from the light receiving element 71L is input to the arithmetic circuit 85 from the input unit 81L. The detection signal output from the light receiving element 71R is input to the arithmetic circuit 85 from the input unit 81R. The detection signal output from the light receiving element 72L is input to the arithmetic circuit 86 from the input unit 82L. The detection signal output from the light receiving element 72R is input to the arithmetic circuit 86 from the input unit 82R. The detection signal output from the light receiving element 73D is input to the arithmetic circuit 87 from the input unit 83D. The detection signal output from the light receiving element 73U is input to the arithmetic circuit 87 from the input unit 83U. The detection signal output from the light receiving element 74D is input to the arithmetic circuit 88 from the input unit 84D. The detection signal output from the light receiving element 74U is input to the arithmetic circuit 88 from the input unit 84U.

  The arithmetic circuits 85 to 88 subtract the detection signals input from the two input units, respectively, and compare them with reference values held inside. From this result, the end of the screen of the laser beam irradiated on the screen 4 can be known. The calculated signal output from the calculation circuit 85 and the inverted signal after calculation output from the calculation circuit 86 are added by the adder 89 and output from the output unit 91 as amplitude information in the X (horizontal direction of the screen 4) direction. Is done. Further, the signal after calculation output from the calculation circuit 87 and the inverted signal after calculation output from the calculation circuit 88 are added by the adder 90, and amplitude information in the Y (vertical direction of the screen 4) direction is output from the output unit 92. Is output as

  Here, an example of the internal configuration of the arithmetic circuit 85 will be described with reference to FIG. However, since the arithmetic circuits 86 to 88 have the same configuration as the arithmetic circuit 85, detailed description thereof is omitted. The arithmetic circuit 85 is configured to compare the detection signals supplied from the light receiving elements 71R and 71L with a reference value. The detection signal output from the light receiving element 71R is input from the input unit 81R. The detection signal output from the light receiving element 71L is input from the input unit 81L. The detection signals input from the input units 81R and 81L are added by the adder 101, and a sum signal is generated. On the other hand, the detection signals input from the input units 81R and 81L are added by the adder 102 to generate a difference signal. However, the adder 102 inverts the detection signal input from the input unit 81L and adds the detection signal input from the input unit 81R.

  The sum signal generated by the adder 101 is supplied to a comparator 103 that compares it with a reference value. The comparator 103 compares the sum signal with the reference value. The switching unit 104 that switches the outputs from the comparator 103 and the adder 102 switches the sum signal or the difference signal according to the reference value. Then, the extracted sum signal or difference signal is supplied to the bottom hold unit 105 that obtains the minimum value of the signal. The bottom hold unit 105 obtains the minimum value and outputs it from the output unit 106. The output value output from the output unit 106 is a signal indicating the scanning end of the laser beam.

  Depending on how the photodetector signal is input to the arithmetic circuit, the top hold is used instead of the bottom hold. Then, amplitude information in two directions (X and Y directions) can be calculated by subtracting signals indicating the respective scanning ends.

  Here, an example of a detection signal output when the divided light receiving element detects a laser beam will be described with reference to FIG. FIG. 14A shows an example of a waveform of a sum signal obtained by adding detection signals detected by the divided light receiving elements. FIG. 14B shows an example of the waveform of the difference signal obtained by subtracting the detection signal detected by the divided light receiving element. A range in which the divided light receiving element can detect the laser beam is shown as a beam position 89. When the laser beam to be scanned is located in the middle of the beam position 89, the sum signal takes the maximum value, and the difference signal forms point-symmetric peaks and valleys at the center. Here, taking as an example a case where the scanning locus of the laser beam is folded back from the left to the right, the bottom hold output changes because the position of the reaching left end is different. FIG. 14C shows an example when the amplitude of the scanning locus is small (when the ray locus is turned from the left to the right at the position X on the right side). The bottom hold output has the value shown in FIG. FIG. 14D shows an example when the amplitude of the scanning locus is large (when the ray locus is turned from left to right at the left position Y). The bottom hold output has the value shown in FIG. For this reason, if feedback control is performed so as to return the bottom hold output value to normal, the amplitude can be kept constant.

  As described above, in the projector device 300, it is possible to know whether the amplitudes of the scan mirror 18 and the inner frame portion 19 are not deviated from normal values by the light receiving elements provided at the upper, lower, left and right ends of the screen 4. Since the laser beam is detected on the screen 4, it can be immediately known when the size of the image projected on the screen 4 changes. For this reason, since feedback control for returning the amplitude to normal can be performed, there is an effect that the amplitude control can be easily performed.

  Next, a configuration example of the projector device according to the fourth embodiment when a sensor is installed outside the biaxial MEMS scanner 10 will be described with reference to FIGS. 15 to 17. The present embodiment is also an example applied to the projector apparatus 400 that scans the laser beam emitted from the light source on the screen 4 and displays an image.

<Photodetector method>
First, an external configuration example of the projector device 400 will be described with reference to FIG. In the projector device 400, the quadrant photodetector 110 is installed on the back surfaces of the scan mirror 18 and the inner frame portion 19. The four-divided photodetector 110 detects the laser beam reflected by the four light receiving elements 111 to 114 from the back surface of the scan mirror 18 and the inner frame portion 19. A laser light source 115 that irradiates a laser beam toward the back surfaces of the scan mirror 18 and the inner frame portion 19 is also installed on the back surfaces of the scan mirror 18 and the inner frame portion 19. The laser light source 115 weakens the output so that the irradiated laser beam does not affect the scan mirror 18 and the inner frame portion 19. Since an external configuration example other than the quadrant photodetector 110 of the projector device 400 is configured in the same manner as in the first embodiment, detailed description thereof is omitted here.

  Next, an example of the internal configuration of the biaxial MEMS scanner 10 that drives the scan mirror 18 and the inner frame portion 19 will be described with reference to FIG. An example of the internal configuration of the biaxial MEMS scanner 10 is almost the same as that of the second embodiment described above. However, the difference is that a light receiving element 110 constituted by a split photodetector as an external sensor is arranged on the back surface of the scan mirror 18 and the inner frame portion 19. The light receiving element 110 detects the amplitudes of the scan mirror 18 and the inner frame portion 19 by the reflected light emitted from the laser light source 115 and reflected from the back surfaces of the scan mirror 18 and the inner frame portion 19. A detection signal having the detected amplitude is generated and supplied to the amplitude detection unit 116. Since an internal configuration example other than the light receiving element of the projector device 400 is the same as that of the second embodiment, detailed description thereof is omitted.

<Photodetector method>
Next, an internal configuration example of the amplitude detection unit 116 will be described with reference to FIG. The detection signal output from the light receiving element 111 is input from the input unit 121 to the adder 125 and the adder 126. The detection signal output from the light receiving element 112 is inverted and input from the input unit 122 to the adder 125 and input to the adder 126 as it is. The detection signal output from the light receiving element 113 is input as it is from the input unit 123 to the adder 125 and is inverted and input to the adder 126. The detection signal output from the light receiving element 114 is inverted and input from the input unit 124 to the adder 125 and the adder 126.

  The adder 125 adds the input detection signals and supplies the addition signals to the top hold unit 127 and the bottom hold unit 128. The signal output from the top hold unit 127 is input to the adder 131 as it is. The signal output from the bottom hold unit 128 is inverted and input to the adder 131. The signal added by the adder 131 is output from the output unit 133. The output signal has amplitude information in the X (horizontal direction of the screen 4) direction.

  The adder 126 adds the input detection signals and supplies the addition signals to the top hold unit 129 and the bottom hold unit 130. The signal output from the top hold unit 129 is input to the adder 132 as it is. The signal output from the bottom hold unit 130 is inverted and input to the adder 132. The signal added by the adder 132 is output from the output unit 134. The output signal has amplitude information in the Y (vertical direction of the screen 4) direction.

  The amplitude detector 116 can obtain scanning end information by top-holding or bottom-holding the difference signal of the light receiving element 110 that is a four-divided photodetector. Amplitude information can be obtained by subtracting this information.

  As described above, in the projector device 400, whether or not the amplitudes of the scan mirror 18 and the inner frame portion 19 deviate from normal values by detecting the laser light emitted to the back surfaces of the scan mirror 18 and the inner frame portion 19 is determined. Can know. Further, since feedback control that returns the amplitudes of the scan mirror 18 and the inner frame portion 19 to normal can be performed, there is an effect that the amplitude control can be easily performed.

  In the fourth embodiment described above, the laser light source is used to irradiate the back surface of the scan mirror 18 and the inner frame portion 19 with a laser beam, but a light emitting diode or the like may be used.

  In the projector apparatus according to the first to fourth embodiments described above, the scan mirror 18 and the inner frame portion 19 themselves are warmed by the amount of the laser beam incident on the scan mirror 18 and the inner frame portion 19, and the spindle torsion bar The control time constant of the amplitude control performed by the amplitude detection unit is faster than the temperature time constant at which the characteristics of the secondary shaft torsion bar (hinge portion) change. Then, by detecting fluctuations in the amplitudes of the scan mirror 18 and the inner frame portion 19, the amplitude can be feedback controlled within a predetermined limit value.

  Further, in the conventional projector apparatus, as the screen becomes brighter (the output of the laser beam increases), the amplitudes (shake angles) of the scan mirror 18 and the inner frame portion 19 change, and the size of the image projected on the screen 4 becomes larger. It has changed. However, in the projector devices according to the first to fourth embodiments described above, a constant screen size can be maintained regardless of the screen brightness. For this reason, there is an effect that an image can be favorably displayed on the screen 4.

  In addition, the sensor for detecting fluctuations in the amplitude of the scan mirror 18 and the inner frame portion 19 can be reduced in size, and includes the image signal supply unit 1, the light source 2, the projection optical system 3, and the biaxial MEMS scanner 10. There is an effect that the whole can be reduced in size.

  In the first to fourth embodiments described above, the feedback control is performed by detecting the amplitudes of the scan mirror 18 and the inner frame portion 19. Feedback control may be performed by detecting temperature, frequency, and the like.

It is the external block diagram which showed the example of the projector apparatus in the 1st Embodiment of this invention. It is the external block diagram which showed the example of the biaxial MEMS scanner in the 1st Embodiment of this invention. It is an internal block diagram which showed the example of the biaxial MEMS scanner in the 1st Embodiment of this invention. It is an internal block diagram which showed the example of the electrostatic actuator in the 1st Embodiment of this invention. It is explanatory drawing which showed the example of the operation | movement waveform and drive waveform of the electrostatic actuator in the 1st Embodiment of this invention. It is explanatory drawing which showed the example of the characteristic of the electrostatic actuator in the 1st Embodiment of this invention. It is an internal block diagram which showed the example of the biaxial MEMS scanner in the 2nd Embodiment of this invention. It is the external block diagram which showed the example of the gyroscope in the 2nd Embodiment of this invention. It is the external block diagram which showed the example of the magnetoresistive sensor in the 2nd Embodiment of this invention. It is the external block diagram which showed the example of the projector apparatus in the 3rd Embodiment of this invention. It is an internal block diagram which showed the example of the biaxial MEMS scanner in the 3rd Embodiment of this invention. It is an internal block diagram which showed the example of the amplitude detection part in the 3rd Embodiment of this invention. It is an internal block diagram which showed the example of the arithmetic circuit in the 3rd Embodiment of this invention. It is explanatory drawing which showed the example of the waveform of the detection signal in the 3rd Embodiment of this invention. It is the external block diagram which showed the example of the projector apparatus in the 4th Embodiment of this invention. It is an internal block diagram which showed the example of the biaxial MEMS scanner in the 4th Embodiment of this invention. It is an internal block diagram which showed the example of the amplitude detection part in the 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image signal supply part, 2 ... Light source, 3 ... Projection optical system, 4 ... Screen, 5 ... Sine wave, 6 ... Saw wave, 7 ... Main axis scanning direction, 8 ... Sub-axis scanning direction, 10 ... Biaxial MEMS scanner , 11a, 11b ... Magnets for secondary shaft electromagnetic drive, 12a, 12b ... Torque bar for secondary shaft, 13 ... Coil for secondary shaft electromagnetic drive, 14a, 14b ... Secondary shaft electrode, 15a, 15b ... Main shaft electrode, 16a, 16b ... Main shaft Torsion bar, 17a, 17b ... rotation side electrode, 18 ... scan mirror, 19 ... inner frame, 20 ... outer frame, 32 ... adder, 33 ... integrator, 34 ... electrostatic actuator, 35 ... sensor, 36 ... Amplitude detector, 50 ... Gyroscope, 61a, 61b ... Magnetic resistance sensor, 62a, 62b ... Magnet, 110-114 ... Light receiving element, 100,200,300,400 ... Projector device

Claims (8)

An image signal supply unit for supplying an image signal;
A first light source that emits a first laser beam having a predetermined wavelength modulated based on the image signal supplied from the image signal supply unit;
In a display device comprising a reflection unit that reflects the first laser light and reciprocally scans the screen,
An amplitude detection unit for detecting resonance vibration performed by the reflection unit;
A correction unit that corrects a drive signal for driving resonance vibration of the reflection unit using an amplitude detection signal of the amplitude detection unit;
A display device, comprising: an actuator that resonates and vibrates the reflection unit based on the drive signal corrected by the correction unit. The display device according to claim 1,
The display device according to claim 1, wherein the amplitude detection unit detects a capacitance of a capacitor built in the actuator and detects a resonance vibration of the reflection unit. The display device according to claim 1,
The display device according to claim 1, wherein the amplitude detection unit includes a sensor configured by a gyroscope that detects rotation of the hinge unit attached to a hinge unit that supports the reflection unit. The display device according to claim 1,
The display device, wherein the amplitude detection unit includes a magnetoresistive detection element mounted on the reflection unit. The display device according to claim 1,
The display device according to claim 1, wherein the amplitude detection unit includes a sensor including light receiving elements provided at upper, lower, left and right ends of the screen. The display device according to claim 1,
The amplitude detecting unit reflects a second laser beam having a predetermined wavelength emitted from a second light source to the back surface of the reflecting unit, and includes a light receiving element that detects the reflected second laser beam. A display device comprising: A first laser beam having a predetermined wavelength, which is modulated based on the supplied image signal, is emitted,
In a display method in which the first laser beam is reflected by a reflecting portion and reciprocally scanned on a screen,
Detecting resonance vibration performed by the reflection unit,
The drive signal for driving the resonance vibration of the reflection part is corrected by the detection signal of the resonance vibration,
A display method comprising: causing the reflection portion to resonate and vibrate based on the corrected drive signal. The display method according to claim 7,
A display method, wherein a correction band of a drive signal for driving resonance is higher than a band corresponding to a temperature time constant of the reflection unit.

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