JP7287864B2 - optical scanner - Google Patents

Description

The present invention relates to an optical scanning device having an optical deflector.

2. Description of the Related Art An optical scanning device that generates scanning light using an optical deflector of MEMS (Micro Electro Mechanical Systems) is known. The optical scanning device reciprocates a mirror portion about a predetermined rotation axis, and reflects incident light from a light source on a reflecting surface portion of the mirror portion to generate scanning light.

In such an optical scanning device, for example, in order to confirm that the rotation range of the mirror portion around the rotation axis is rated, or to detect the emission direction of the scanning light, the rotation angle A rotation angle detector for detecting is required.

In the optical scanning device of Patent Document 1, the amount of incident light that has passed straight through a through hole penetrating the mirror portion of the optical deflector in the thickness direction is detected by the PD provided on the back side of the mirror portion. ing. Then, the rotation angle of the mirror portion around the rotation axis is detected based on the amount of light detected by the PD.

JP-A-2003-5124

The amount of incident light that passes straight through the through-hole of the mirror portion is maximized when the incident angle of the incident light with respect to the surface of the mirror portion is 0°, and decreases as the incident angle increases. In a general optical scanning device, the incident angle is maximized when the rotation angle of the mirror portion about the rotation axis is at one end or the other end of the rotation range.

Therefore, in the optical scanning device of Patent Document 1, when the rotation angle of the mirror section about the rotation axis is at one end or the other end of the rated rotation range, the amount of light detected by the rotation angle detection section is minimized. (including 0), and the detection accuracy decreases.

It is possible to conceive a configuration in which the through-holes formed in the mirror section are not parallel to the thickness direction of the mirror section but are inclined. However, forming a through-hole inclined in the thickness direction in the mirror portion increases the manufacturing cost of the MEMS optical deflector.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical scanning device capable of detecting the rotation angle of a mirror section with a sufficient amount of light without forming an inclined through hole.

The optical scanning device of the present invention is
an optical deflector having a mirror portion whose surface is a reflecting surface portion that reflects incident light from a light source, is provided with a through hole that penetrates perpendicularly to the surface, and reciprocates about a predetermined rotation axis;
Within the predetermined rotation angle range of the mirror portion, out of the incident light, the light passing straight through the through hole is out of the optical path, and the incident light is reflected by the inner wall surface of the through hole. a light detection section having a light receiving area within the optical path of the reflected passing light, disposed on the back side of the mirror section, and configured to receive the reflected passing light;
a rotation detection unit that detects the rotation angle or rotation angle range of the mirror unit based on the output of the light detection unit;
Prepare.

According to the present invention, the light passing through the through hole is divided into the reflected passing light that passes through after being reflected by the inner wall surface of the through hole, and the remaining straight passing light. The passing reflected light scans with a sufficient amount of light in a certain direction as the mirror section rotates about a predetermined rotation axis. Therefore, by detecting the reflected passing light with the photodetector, a sufficient amount of light can be applied to the rotation angle of the mirror section without forming a through hole inclined in the thickness direction of the mirror section. range) can be detected.

Preferably, a reflecting surface portion on which the reflected passing light is reflected on the inner wall surface of the through hole is formed as a plane parallel to the rotating shaft.

According to this configuration, the reflecting surface portion of the passing light on the inner wall surface of the through hole is formed as a plane parallel to the rotation axis. As a result, the reflected passing light emitted from the reflecting surface reaches the photodetector while being sufficiently constricted in the radial direction without spreading in the radial direction. As a result, it is possible to improve the detection accuracy of the rotation angle and the like.

Preferably, the reflecting surface portion on which the reflected passing light is reflected on the inner wall surface of the through hole is formed as a metal surface.

According to this configuration, the reflecting surface portion of the through-hole for reflected and passing light is formed as a metal surface. As a result, the reflectance is increased, and the amount of heat generated in the mirror section due to reflected passing light (eg, laser light) can be suppressed.

Preferably, a protuberant portion formed with an extension surface of the reflective surface portion of the through hole is formed on the rear surface side of the mirror portion.

According to this configuration, the light directed toward the photodetector is a combination of the passing reflected light reflected by the reflecting surface portion in the through hole and the remaining reflected light reflected by the extended surface of the raised portion. As a result, it is possible to increase the amount of reflected light detected by the photodetector and improve the detection accuracy of the rotation angle and the like.

Preferably,
The mirror section has a first rotation axis that is the predetermined rotation axis, and a second rotation axis that is different from the predetermined rotation axis and perpendicular to the first rotation axis at the center of the mirror section. reciprocatingly rotates around
The through hole is formed on the second rotating shaft.

According to this configuration, the through hole is formed on the second rotation axis in the mirror section. As a result, the amount of incident light entering the through hole is suppressed from fluctuating during reciprocating rotation of the mirror portion about the second rotation axis. As a result, it is possible to improve the detection accuracy of the rotation angle and the like.

Preferably, the mirror section reciprocates about the first rotation axis and the second rotation axis in resonance and non-resonance, respectively.

According to this configuration, the reciprocating rotation angle of the mirror portion about the resonance axis can be detected with high accuracy using the reflected passing light.

Preferably,
The light detection unit has a light receiving surface that receives the reflected passing light, and outputs an electrical signal related to a light receiving position on the light receiving surface,
The rotation detection section detects a rotation angle of the mirror section about the predetermined rotation axis based on the electrical signal.

According to this configuration, it is possible to detect the rotation angle of the mirror section about the predetermined rotation axis by detecting the light receiving position of the reflected and passing light on the light receiving surface of the light detection section.

Preferably, the photodetector is a PSD.

According to this configuration, the light receiving position of the reflected passing light on the light receiving surface can be detected by the PSD.

Preferably,
setting the center of the rotation angle range of the mirror unit around the predetermined rotation axis as the central rotation angle,
The light-receiving surface of the light detection section is a first surface portion on one side in the scanning direction of the reflected passing light with respect to the light-receiving position of the reflected passing light when the mirror section is at the central rotation angle. and a second surface portion on the other side,
the photodetector includes a first PD having a light receiving surface as the first surface portion and a second PD having a light receiving surface as the second surface portion;
The output of the photodetector includes the output of the first PD and the output of the second PD.

According to this configuration, the light receiving position of the reflected passing light on the light receiving surface can be detected from the output from the PD, which is sufficiently inexpensive compared to the PSD.

Preferably,
setting the center of the rotation angle range of the mirror unit around the predetermined rotation axis as the central rotation angle,
The photodetector is
a PD having a light receiving surface extending in the scanning direction of the reflected passing light;
a light-shielding plate covering the light-receiving surface of the PD and having transmission holes formed on one side and the other side with respect to the scanning direction position when the mirror portion is at the central rotation angle;
have

According to this configuration, the reflected passing light passes through the transmission hole of the light shielding plate and reaches the light receiving surface of the PD only when the scanning position of the reflected passing light coincides with the transmission hole of the light shielding plate. Also, the position of the transmission hole of the light shielding plate corresponds to a predetermined rotation angle of the mirror portion around the predetermined rotation axis. Thereby, the predetermined rotation angle of the mirror section can be detected based on the output of the PD.

Preferably, the position of the transmission hole in the light shielding plate is the position of the reflected passing light when the mirror portion is at the rotation angle at both ends of the rated rotation range of the mirror portion about the predetermined rotation axis. It is set to the scanning direction position.

According to this configuration, it is possible to detect whether or not the mirror portion has rotated to the rotation angles at both ends of the rated rotation range without any trouble.

Preferably,
The direction of incidence of the incident light is set so that the direction of incidence of the incident light is not perpendicular to the surface over the entire predetermined rotation angle range of the mirror section.

According to this configuration, it is possible to avoid a situation in which all of the incident light entering the through hole becomes light passing straight through. As a result, it is possible to improve the detection accuracy of the rotation angle of the mirror portion about the rotation axis.

1 is a configuration diagram of an optical scanning device; FIG. FIG. 4 is a view of the photodetector and the mirror when the mirror is in a neutral position, viewed from the surface side (Z-axis direction + side) of the mirror; FIG. 10 is a view of the photodetector and the mirror when the mirror is at a neutral position, viewed from above (+ side in the Y-axis direction); 3 is a schematic diagram of the relationship between optical paths of light beams and light spots in an optical scanning device; FIG. FIG. 4 is an explanatory diagram of dimensions of a light spot generated on a light receiving surface of a PSD; FIG. 4 is a diagram showing a correspondence relationship between a rotational position of a mirror portion and a position of a light spot Sp when the mirror portion is reciprocatingly rotated around a rotation axis Ay; FIG. 10 is a diagram obtained by examining the relationship between the rotation angle αy of the mirror portion and the barycentric position of the light intensity distribution on the light receiving surface of the PSD by simulation. 5 is a graph showing temporal changes in the rotation angle βy of the mirror portion and the amount of received light Q of the PSD. 4 is a graph showing the relationship between the variation width of the variation voltage in the driving voltage of the inner piezoelectric actuator of the optical deflector and the rotation angle range Wy of the mirror portion around the rotation axis Ay. FIG. 10 is a diagram showing the relationship between the variation width of FIG. 9 and the variation width of the difference between the two output voltages of the PSD; 5 is a flow chart of calibration of the rotation angle range of the mirror unit which is performed each time the power of the optical scanning device is turned on. FIG. 10 is an overall configuration diagram of an optical scanning device according to a second embodiment; It is the figure which looked at the optical scanning device from the + side of the Z-axis in 2nd Embodiment. FIG. 10 is a schematic diagram of the relationship between the optical paths of the light beams and the light spots Sp in the optical scanning device in the second embodiment; FIG. 10 is a diagram showing an optical path and light intensity distribution Sd of reflected passing light or the like when the rotation angle βy of the mirror portion around the rotation axis Ay is 0[°] in the second embodiment; FIG. 10 is a diagram showing optical paths and luminous intensity distributions of reflected passing light and the like when the rotation angle βy of the mirror portion about the rotation axis Ay is −5[°] in the second embodiment; FIG. 10 is a diagram showing optical paths and light intensity distributions of reflected passing light Lc and the like when the rotation angle βy of the mirror portion about the rotation axis Ay is +5[°] in the second embodiment; It is the figure which investigated the relationship between rotation angle (alpha)y and output voltage ratio by the simulation in 2nd Embodiment. FIG. 11 is a diagram of the overall configuration of an optical scanning device according to a third embodiment; FIG. 11 is a view of the photodetector and the mirror section viewed from the + side in the Y-axis direction when the mirror section is in a neutral position in the third embodiment; FIG. 10 is a schematic diagram of the relationship between the optical paths of light beams and the light spots in the optical scanning device according to the third embodiment; FIG. 11 is a diagram obtained by examining the relationship between the rotation angle αy of the mirror section and the output of the PD by simulation in the third embodiment. 10 is a flow chart of calibration of the rotation angle range of the mirror section performed each time the optical scanning device is powered on in the third embodiment. FIG. 4 is a configuration diagram of a main portion for substantially increasing the area of the reflective surface portion;

Preferred embodiments of the present invention are described in detail below. In the following description, common reference numerals are used for substantially identical or equivalent elements and parts. Also, for elements of pairs or groups having the same configuration, reference numerals with the same numerals and different alphabetical subscripts are used. Furthermore, when referring to reference signs that differ only in alphabetical suffixes, reference numerals omitting the alphabetical suffixes are used.

(First embodiment)
FIG. 1 is a configuration diagram of the optical scanning device 10a. The optical scanning device 10 a includes a laser light source 11 , an optical deflector 12 , a control device 13 and a photodetector 14 .

The virtual screen 15 is not included in the components of the optical scanning device 10a. The virtual screen 15 is arranged virtually to explain the scanning state of the scanning light Ls from the optical scanning device 10a. In a practical application of the optical scanning device 10a, the virtual screen 15 is replaced by a wall, screen, track, or the like. The optical scanning device 10a is applied to an image generation device, an ADB (Adaptive Driving Beam) of a car, and the like.

The optical deflector 12 is manufactured from SOI (Silicon on Insulator) as MEMS (Micro Electro Mechanical Systems). The optical deflector 12 includes a mirror portion 31, torsion bars 32a and 32b, inner piezoelectric actuators 33a and 33b, a movable frame portion 34, outer piezoelectric actuators 35a and 35b, and a fixed frame portion 36 as main elements.

For convenience of explanation of the configuration of the optical deflector 12, a three-axis orthogonal coordinate system is defined. The X-axis and Y-axis are parallel to the long sides and short sides of the fixed frame portion 36 . The Z-axis is parallel to the thickness direction of the optical deflector 12 .

O is the center of the mirror section 31 . The center O is also the center of the optical deflector 12 . Incident light La such as laser light from the laser light source 11 is incident on the mirror section 31 so that the peak point of the light intensity distribution in the cross section (also referred to as the center of gravity of the light intensity distribution) is at the center O.

The rotation axis Ax and the rotation axis Ay are orthogonal to each other at the center O of the mirror section 31 as two rotation axes of the mirror section 31 . The surface of the mirror portion 31 serves as a reflecting surface portion for the incident light La. The scanning light Lb is light obtained by reflecting the incident light La on the surface of the mirror section 31 .

Here, the neutral position of the mirror section 31 is defined. The neutral position refers to the rotation angle of the mirror section 31 when it is at the rotation position at the center of the rotation angle range around the rotation axis on which the mirror section 31 is rotatable. The mirror portion 31 of the optical deflector 12 is rotatable about two axes, the rotation axis Ax and the rotation axis Ay. Therefore, the neutral position of the mirror section 31 is defined as a neutral position around the rotation axis Ax and a neutral position around the rotation axis Ay.

A neutral position about the rotation axis Ax is called "neutral position x", and a neutral position about the rotation axis Ay is called "neutral position y". Also, the neutral position where the mirror portion 31 is at the neutral position x and the neutral position y is represented by "neutral position xy". The neutral position xy corresponds to the rotational position of the mirror section 31 when the mirror section 31 faces directly in front of the light detection section 14 .

The torsion bars 32a and 32b extend from both sides of the mirror portion 31 along the rotation axis Ay in the Y-axis direction.

The inner piezoelectric actuators 33a, 33b are arranged on both sides of the mirror section 31 in the X-axis direction, and are coupled to intermediate portions of the torsion bars 32a, 32b at each end in the Y-axis direction. The inner piezoelectric actuators 33 a and 33 b are coupled to each other at both ends in the Y-axis direction, and have an annular shape as a whole, surrounding the mirror section 31 .

The movable frame portion 34 surrounds the inner piezoelectric actuators 33a and 33b. Each torsion bar 32 is coupled to the inner periphery of the movable frame portion 34 at the end opposite to the mirror portion 31 . Each inner piezoelectric actuator 33 is coupled to the inner circumference of the movable frame 34 at the midpoint of the semi-ring-shaped outer circumference. The connecting portion between the inner piezoelectric actuator 33 and the movable frame portion 34 is located on a straight line passing through the center O and parallel to the X-axis.

The outer piezoelectric actuators 35a and 35b are arranged on both sides of the mirror section 31 in the X-axis direction. Each outer piezoelectric actuator 35 is coupled to the outer periphery of the movable frame portion 34 and the inner periphery of the fixed frame portion 36 at both ends. Each outer piezoelectric actuator 35 has a plurality of cantilevers 41 connected in a meander pattern.

The inner piezoelectric actuator 33 and the outer piezoelectric actuator 35 are supplied with drive voltages Vdi and Vdo, respectively, from a drive device (not shown). The inner piezoelectric actuator 33 is interposed between the torsion bar 32 and the movable frame portion 34 to torsionally vibrate the torsion bar 32 around the rotation axis Ay at the resonance frequency. As a result, the mirror section 31 reciprocates around the rotation axis Ay at the resonance frequency Fy.

It is assumed that the plurality of cantilevers 41 of each outer piezoelectric actuator 35 are numbered sequentially from the fixed frame portion 36 side to the movable frame portion 34 side as No. 1, No. 2, . In this case, the odd-numbered cantilevers 41 and the even-numbered cantilevers 41 receive drive voltages Vdo having the same peak-to-peak (voltage variation width) and opposite phases from the control device 13 .

As a result, the odd-numbered cantilevers 41 and the even-numbered cantilevers 41 bend in opposite phases, so that the rotation angle range of the movable frame 34 around the rotation axis Ax by the outer piezoelectric actuator 35 as a whole can be increased. can be done. The mirror portion 31 reciprocates around the rotation axis Ax at a non-resonant frequency Fx. Non-resonant frequency Fx<resonant frequency Fy.

Here, the rotation angles αx and αy are defined. The rotation angle αx is the rotation angle of the mirror section 31 around the rotation axis Ax. The rotation angle αy is the rotation angle of the mirror section 31 around the rotation axis Ay. The rotation angle αy is defined as a value that increases as the mirror portion 31 rotates more to the negative side in the X-axis direction when the optical deflector 12 is viewed from the front (see the horizontal axis in FIG. 7).

As for the rotation angle αy, a rotation angle βy is separately defined as the rotation angle of the mirror portion 31 around the rotation axis Ay (see the vertical axis in FIG. 8). The rotation angle βy is defined as 0[°] when the mirror section 31 is at the neutral position y.

In this example, when the rotation angle βy=0[°], the rotation angle αy is defined as 22.5[°]. Therefore, there is a relationship of βy=αy−22.5.

The control device 13 includes a PSD control circuit 19 , a mirror control IC 20 and a control data memory 21 . The photodetector 14 is arranged on the back side of the optical deflector 12 .

In the optical scanning device 10a, the photodetector 14 is composed of a PSD28. Details of PSD 28 are described in FIG.

The PSD control circuit 19 supplies a voltage necessary for operating the photodetector 14 and receives an output voltage from the photodetector 14 . The mirror control IC 20 implements control software 24 . The mirror control IC 20 executes a control software 24 program based on the data in the control data memory 21 and the input from the PSD control circuit 19 . By executing the program, the luminous intensity of the laser light source 11 and the rotation angles αx and αy of the mirror portion 31 of the optical deflector 12 are controlled.

The laser light source 11 emits incident light La toward the center O of the movable frame 34 . The incident light La is reflected by the movable frame 34 and emitted as scanning light Lb in directions corresponding to the rotation angles αx and αy of the movable frame 34 . The scanning light Lb scans the virtual screen 15 vertically (vertically) and horizontally (horizontally), and the traces of the scanning light Lb form an image or a light distribution pattern image on the virtual screen 15 .

2 and 3, when the mirror portion 31 is in the neutral position, the photodetector portion 14a and the mirror portion 31 are detected from the surface side (Z-axis direction + side) and the upper side (Y-axis direction + side) of the mirror portion 31, respectively. It is a view.

The surface of the mirror portion 31 serves as a reflecting surface portion 45 for the incident light La. The through hole 46 penetrates the mirror section 31 in parallel with the thickness direction (Z-axis direction) of the mirror section 31 . In this example, the through hole 46 is formed with a square cross section, and each side surface of the inner wall surface 55 (FIG. 5) of the through hole 46 is a plane parallel to the rotation axis Ax or Ay.

The light detection section 14 is arranged on the rear surface side of the mirror section 31 . The photodetector 14 is composed of, for example, a PSD (Position Sensitive Detector) 28 and constitutes the photodetector of the optical scanning device 10 . Specifically, the PSD 28 has a structure in which the P layer on the surface of the PIN photodiode is used as a resistance layer, and the position of the light spot on the surface is detected from the voltage across the resistance layer in the longitudinal direction.

The light detection section 14 has a light receiving surface 49 on the mirror section 31 side. The light-receiving surface 49 is square, and each side is aligned parallel to the X-axis and the Y-axis. The through hole 46 is located on a straight line passing through the center O and parallel to the X axis in the mirror portion 31 .

In FIG. 2, the center Od is the center of the light receiving surface 49 of the PSD28. In FIG. 3, the plane Co is a straight line passing through the center O and parallel to the Y-axis. A plane Ch is a straight line passing through the center of the through-hole 46 and parallel to the Y-axis. Plane Ca is a straight line passing through center Od (FIG. 2) and parallel to the Y axis.

In FIGS. 2 and 3, the definitions of Da1 to Da7 are as follows.
Da1: Diameter of mirror portion 31 Da2: Length of through-hole 46 in the Y-axis direction Da3: Length of through-hole 46 in the X-axis direction Da4: Distance between plane Co and plane Ca Da5: Between plane Co and plane Ch Distance Da6: Thickness of mirror portion 31 Da7: Distance in the Z-axis direction between the rear surface of mirror portion 31 and light receiving surface 49

Examples of the values of Da1 to Da7 and the rotation angle αy are as follows.
Da1=2.0mmφ
Da2, Da3=50 μm
Da4=1.175mm
Da5=1.0mm
Da6=50 μm
Da7=1.2mm

FIG. 4 is a schematic diagram of the relationship between the optical path of each light and the light spot Sp in the optical scanning device 10a. Most of the incident light La is reflected by the reflecting surface portion 45 to become the scanning light Lb.

Part of the incident light La enters the through hole 46 . The incident light La entering the through-hole 46 is reflected by the inner wall surface 55 of the through-hole 46 and then travels straight without being reflected by the inner wall surface 55 with the reflected passing light Lc emitted to the rear surface side of the mirror portion 31 . It is divided into straight passing light Ld that passes through the through hole 46 as it is.

The PSD 28 is arranged outside the optical path of the straight passing light Ld and within the optical path of the reflected passing light Lc within a predetermined rotation angle range of the mirror portion 31 about the rotation axis Ay. In this example, the predetermined rotation angle range is (22.5-5)[°]≤αy≤(22.5+5)[°].

FIG. 5 is an explanatory diagram of the dimensions of the light spot Sp generated on the light receiving surface 49 of the PSD 28. As shown in FIG. The mirror section 31 is at the neutral position xy in the position shown in FIG. FIG. 5 shows the configuration of the through holes 46 in detail. The through-hole 46 has an inner wall surface 55 and opens at a front side opening 53 and a back side opening 54 on the front side and the back side of the mirror section 31 .

The inner wall surface 55 is of square cross-section. Of the four side surfaces of the inner wall surface 55 , the side surface closest to the rotation axis Ay forms a reflecting surface portion 57 . The reflecting surface portion 57 is formed as a plane parallel to the rotation axis Ay. The inner wall surface 55 is a metal surface. That is, the mirror section 31 is made of an SOI Si layer in the MEMS, but the inner wall surface 55 is entirely covered with a metal layer.

Therefore, naturally, the reflecting surface portion 57 is also a metal surface. Since the reflective surface portion 57 is a metal surface, the reflectance of the incident light La is increased, and the luminous intensity of the reflected passing light Lc can be increased. Moreover, heat generation of the Si layer of the mirror section 31 can be suppressed.

In FIG. 5, reference numerals are added with respect to FIG. The definition of each added code is as follows.
Ci: plane including reflective surface portion 57 Cr: plane Cl perpendicular to light receiving surface 49 passing through the position closest to rotation axis Ay on the periphery of light spot Sp (the right end of light spot Sp in FIG. 5): light spot Plane θ perpendicular to the light receiving surface 49 passing through the farthest position from the rotation axis Ay on the periphery of Sp (the left end of the light spot Sp in FIG. 5): inclination angle of the incident light La with respect to the reflecting surface portion 45 of the mirror portion 31 θ′: inclination angle of incident light La with respect to plane Ci Dr: distance between plane Ci and plane Cr Dl: distance between plane Ci and plane Cl

Note that θ+θ'=90[°], and θ changes according to the rotation angle αy. Also, Da3 and Da6 in FIG. 5 are as defined in FIG. Furthermore, θ'=βy.

Formula (1): tan θ' ≤ Da3/Da6
Formula (2): Dl = (L + Da6) sin θ'
Formula (3): Dr=L·sin θ′

However, L=Da7. If Da3=Da6=0.050 mm in formulas (1) to (3), tan θ′=1 from formula (1). In order to satisfy θ′≦45[°], the rotation angle αy of the mirror unit 31 is ±5[ °] is assumed.

When θ′=17.5[°] (=22.5−5), Dr=0.394 mm and Dl=0.378 mm. When θ′=22.5[°], Dr=0.518 mm and Dl=0.497 mm. When θ′=27.5[°] (=22.5+5), Dr=0.651 mm and Dl=0.625 mm.

The light spot Sp scans the light receiving surface 49 in the X-axis direction according to the rotation angle αy of the mirror section 31 about the rotation axis Ay. However, the desired dimension of the light spot Sp is ensured in the rotation angle range in which the rotation angle αy changes. This means that a light spot Sp having a sufficient amount of light is generated on the light receiving surface 49 within a predetermined rotation angle range.

FIG. 6 shows the correspondence between the rotation position of the mirror section 31 and the position of the light spot Sp when the mirror section 31 reciprocates about the rotation axis Ay. The mirror portion 31 is at the neutral position x at all of the rotational positions Pc, Pr, and Pl. The rotational position Pc is also the neutral position y of the mirror section 31 . The rotational position Pr corresponds to when the right end of the mirror portion 31 in front view is most on the + side in the Z-axis direction. The rotational position Pl corresponds to when the left end of the mirror portion 31 in the front view comes to the most + side in the Z-axis direction.

The rotation angles αy of the rotation positions Pr, Pc, and Pl are 17.5[°] (=22.5−5), 22.5[°], and 27.5[°] (=22.5+5), respectively. is.

With the dimensions shown in FIG. 3, when the mirror portion 31 is reciprocally rotated around the rotation axis Ay between the rotation position Pr and the rotation position Pl, the center of the light spot Sp at the rotation position Pl and the rotation position Pr is about 0.25 mm from the center of the light spot Sp. On the other hand, among the diameters Sp of the light spots at the rotational positions Pl, Po, and Pr, the maximum diameter is 0.026 mm at the rotational position Pl, and the minimum diameter is 0.016 mm at the rotational position Pr. .

From the above, the change in the diameter of the light spot Sp is sufficiently small with respect to the displacement of the light spot Sp. As a result, the rotation angle αy of the mirror section 31 can be detected from the light receiving position of the light spot Sp while ensuring a sufficient amount of light received by the light receiving surface 49 of the PSD 28 .

FIG. 7 is a diagram showing the relationship between the rotation angle αy of the mirror section 31 and the barycentric position of the luminous intensity distribution Sd (see FIG. 16) on the light receiving surface 49 of the PSD 28, which was examined by simulation.

The reflected passing light Lc generated by reflecting the incident light La on the inner wall surface 55 is highly scattered, and actually has the intensity of the luminous intensity distribution Sd. In the simulation of FIG. 7, the center of the light spot Sp is calculated as the center of gravity of the intensity distribution with σ=0.15 and a scattering ratio of 1 in the luminous intensity distribution Sd.

FIG. 8 is a graph showing changes in the rotation angle βy (=αy−22.5) of the mirror section 31 and the amount of light received Q of the PSD 28 over time (one cycle T). The numerical value on the horizontal axis is simply a scale indicating the passage of time, and the unit is different from seconds. As will be described with reference to FIG. 9, the drive voltage Vdi for the mirror section 31 has a sine wave component, and the change voltage component of the sine wave component is represented by Vis. The waveform of the rotation angle βy becomes a waveform synchronized with the change voltage Vis.

FIG. 9 shows the fluctuation width Viw of the change voltage Vis of the drive voltage Vdi of the inner piezoelectric actuator 33 of the optical deflector 12 and the rotation angle range Wy (variation width of αy) of the mirror section 31 around the rotation axis Ay. is a graph showing the relationship between From FIG. 9, it is necessary to satisfy Viw≧8.2 [V] in order to secure the rotation angle range Wy≧10[°].

FIG. 10 shows the relationship between the variation width Viw in FIG. 9 and the variation width Vpw of the difference between the two output voltages of the PSD 28. In FIG. The PSD 28 outputs two output voltages to the PSD control circuit 19, and the control software 24 determines the position of the light spot Sp at 40 of the PSD 28, that is, the light spot in the scanning direction of the light spot Sp from the difference or ratio between the two output voltages. Detect the position of Sp. Therefore, the variation width Vpw on the vertical axis in FIG. 10 is equivalent to the rotation angle range Wy of αy of the mirror section 31 .

From FIG. 10, it can be seen that when the fluctuation width Viw=8.2 [V], the fluctuation width Vpw=2.8 [V]. In other words, if the variation width Vpw≧2.8 [V] of the PSD 28 is obtained, the rotation angle range Wy≧10 [°] is ensured.

FIG. 11 is a flowchart of calibration of the rotation angle range Wy of the mirror section 31 that is performed each time the optical scanning device 10a is turned on. Since the piezoelectric element of the optical deflector 12 of the optical scanning device 10 deteriorates as it is used for a long time, the amount of deformation for the same drive voltage value gradually decreases. On the other hand, in the optical scanning device 10a, the photodetector section 14 must ensure the rotation angle range Wy of the mirror section 31 to be 10[°] or more.

In the calibration of FIG. 11, the driving voltage Vdi of the inner piezoelectric actuator 33 is increased according to the deterioration of the piezoelectric element of the inner piezoelectric actuator 33 of the optical deflector 12, so that the mirror portion is The rotation angle range Wy of αy of 31 is maintained at 10[°] or more. Note that the reciprocating rotation of the mirror portion 31 about the rotation axes Ay and Ax is resonant and non-resonant, respectively. Therefore, the terms "resonant sine wave voltage" and "non-resonant sine wave voltage" mean the change voltage portion Vis of the drive voltage Vdi and the change voltage portion Vos of the drive voltage Vdo, respectively.

The resonant sine wave voltage corresponds to the change characteristic of the rotation angle βy of the mirror section 31 in FIG. 8 (solid line in FIG. 8). In the rotation angle βy, the unit of the vertical axis is [°], but when the resonant sine wave voltage is shown in FIG. 8, the unit of the vertical axis is changed to [V].

In STEP 101, the control device 13a turns on the light source (laser light source 11).

In STEP 102, the controller 13a increases the variation width (Viw) of the resonant sine wave voltage by a predetermined amount Δ. STEP102 to STEP104 form a loop. Therefore, in the first execution of STEP 102, the resonant sine wave voltage after setting is the initial value read from the control data memory 21 by the controller 13a.

The initial value of the resonant sine wave voltage is set by an inspector at the manufacturing factory of the optical manipulating device 10a when the optical scanning devices 10a are shipped from the factory. This is the value confirmed by inspecting the value of the minimum change voltage component Vis at which the dynamic angle range Wy becomes 10[°] or more. This value is recorded in the control data memory 21 by the inspector as an initial value of the change voltage Vis for each optical scanning device 10a.

In STEP 103, the controller 13a determines whether or not the drive voltage Vdi≦the rated value (the upper limit of the resonant sine wave voltage). Then, when the determination result is affirmative, the process proceeds to STEP104. If the determination result is negative, the process proceeds to STEP106.

In STEP 104, the control device 13a determines whether or not the variation width (Vpw) of the output voltage of the PSD 28≧the threshold value (2.8 V in FIG. 10). Then, when the determination result is affirmative, the process proceeds to STEP105. If the determination result is negative, the process returns to STEP102.

In STEP 105, the controller 13a determines that the optical deflector 12 is accepted. In STEP 106, the control device 13a determines that the optical deflector 12 is rejected.

In STEP 107, the control device 13a turns off the light source (laser light source 11).

(Second embodiment)
FIG. 12 is an overall configuration diagram of the optical scanning device 10b of the second embodiment. Only differences from the optical scanning device 10a will be described. The optical scanning device 10b is equipped with a control device 13b and a photodetector 14b, respectively, in place of the control device 13a and the photodetector 14a of the optical scanning device 10a. The control device 13b includes a TIA (transimpedance amplifier) 67 in place of the PSD control circuit 19 of the control device 13a. The output voltage of the photodetector 14b is input to the mirror control IC 20 via the TIA 67. FIG.

FIG. 13 is a diagram of the optical scanning device 10b viewed from the + side of the Z axis. Only differences from the configuration of FIG. 3 described above will be described.

The photodetector 14b is divided by the boundary 63 into a PD 61l on the negative side in the X-axis direction and a PD 61r on the positive side. The PDs 61l and 61r are independent, and individually detect and output the amount of light received in the light intensity distribution Sd (FIG. 15) generated on the light receiving surfaces 62l and 62r. The light receiving surfaces 62l and 62r are separated in the X-axis direction by the boundary 63, but form one continuous plane continuous in the scanning direction of the light spot Sp (FIG. 14). The light spot Sp corresponds to an area extracted from the luminous intensity distribution Sd where the luminous intensity is equal to or greater than a predetermined threshold value. Therefore, the sum of the amounts of light received by the PDs 61l and 61r (also the sum of the output voltages of the PDs 61l and 61r) maintains a substantially constant value regardless of the position of the light spot Sp in the scanning direction.

The definition of each code|symbol in FIG. 13 is as follows.
Cb: plane passing through boundary 63 and parallel to Z-axis Db1: diameter of mirror portion 31 Db2: side length of through-hole 46 in Y-axis direction Db3: side length of through-hole 46 in X-axis direction Db4: X-axis direction Distance Db5 between the center O and the plane Cb: Distance Db6 between the center O and the plane Ch in the X-axis direction: Thickness of the mirror section 31 Db7: Distance between the back surface of the mirror section 31 and the light receiving surface 49 in the Z-axis direction

Examples of the values of Db1 to Db7 and the rotation angle αy are as follows.
Db1=2.0mmφ
Db2=50 μm
Db3=50 μm
Db4 = 0.895mm
Db5=0.7mm
Db6=50 μm
Db7=0.5mm
Rotating angle αy=22.5 [°]

FIG. 14 is a schematic diagram of the relationship between the optical path of each light and the light spot Sp in the optical scanning device 10b. The optical path of each light is shown. Only differences from FIG. 4 will be described.

The light spot Sp moves back and forth between the light receiving surface 62l of the PD 61l and the light receiving surface 62r of the PD 61r across the boundary 63 in the X-axis direction as the mirror portion 31 reciprocates about the rotation axis Ay.

15 to 17 show the optical paths of the reflected passing light Lc and the like when the rotation angles βy of the mirror section 31 about the rotation axis Ay are 0 [°], -5 [°], and +5 [°], respectively. A luminous intensity distribution Sd is shown. A region of the light intensity distribution Sd having a light intensity equal to or higher than the threshold becomes the light spot Sp. Furthermore, the peak of the luminous intensity distribution Sd becomes the maximum luminous intensity of the luminous intensity distribution Sd.

The position of the light intensity distribution Sd in the scanning direction changes according to the rotation angle βy of the torsion bar 32 . This change results in changes in the output voltages vl and vr of the light receiving surfaces 62l and 62r.
As a result, the position Px of the light spot Sp in the X-axis direction can be calculated from the following equation.
Formula (4): Px=k (vl-vr)/(vl+vr)
However, k is a constant. Px=0 is the position of the boundary 63 in the X-axis direction.

FIG. 18 is a graph showing the relationship between the rotation angle αy (=βy+22.5) and the output voltage ratio examined by simulation. The output voltage ratio means (vl-vr)/(vl+vr). The luminous intensity distribution Sd is set to σ=0.15 and scattering ratio=1. It can be seen that the rotation angle αy (=βy+22.5) and (vl-vr)/(vl+vr) have a unique relationship.

(Third embodiment)
FIG. 19 is an overall configuration diagram of an optical scanning device 10c according to the third embodiment. Only differences from the optical scanning device 10b will be described. The optical scanning device 10c includes a controller 13c and a photodetector 14c instead of the controller 13b and the photodetector 14b. The control device 13c omits the control data memory 21 of the control device 13b.

FIG. 20 is a diagram of the photodetector 14c and the mirror 31 viewed from the + side in the Y-axis direction when the mirror 31 is in the neutral position.

The photodetector 14 c includes a PD 70 and a light shielding plate 75 . The PD 70 has a light-receiving surface 71 whose length covers the entire change in scanning position of the light spot Sp. In FIG. 20, plane Cc is the same plane as plane Cb in FIG. The light shielding plate 75 is arranged parallel to the light receiving surface 71 of the PD 70 so as to cover the light receiving surface 71 . The light shielding plate 75 has through holes 76l and 76r on the - side and the + side in the X-axis direction with respect to the plane Cc. As a result, the light receiving surface 71 receives the reflected passing light Lc when the reflected passing light Lc passes through the through holes 76l and 76r.

The definition of each symbol in FIG. 20 is as follows.
Cl: a plane passing through the center of the through hole 76l and parallel to the plane Cc Cr: a plane passing through the center of the through hole 76r and parallel to the plane Cc Dc1: the diameter of the mirror portion 31 Dc3: the side length of the square through hole 46 Dc4: distance between center O and plane Cb Dc5: distance between center O and plane Ch Dc6: thickness of mirror section 31 Dc7: distance between back surface of mirror section 31 and light receiving surface 71 Dc8: distance between light receiving surface 71 and Distance Dl from the rear surface of light shielding plate 75: Distance Dr between plane Cc and plane Cl: Distance between plane Cc and plane Cr

Examples of values of Dc1 to Dc10 are as follows.
Dc1=2.0mmφ
Dc2, Dc3=50 μm
DC4=1.175mm
Dc5=0.7mm
Dc6=50 μm
DC7=1.2mm
DC8=0.075mm
Dl=0.26 mm
Dr=0.27mm

FIG. 21 is a schematic diagram of the relationship between the optical path of each light and the light spot Sp in the optical scanning device 10c. Only differences from FIG. 4 will be described. In the optical scanning device 10 c , the PD 70 receives only the reflected light Lc that has passed through the through holes 76 l and 76 r of the light shielding plate 75 on the light receiving surface 71 .

FIG. 22 shows the relationship between the rotation angle αy of the mirror section 31 and the output ([W]) of the PD 70. As shown in FIG. The output of the PD 70 appears only when the rotation angle αy=22.5±5[°], and no output occurs at other rotation angles αy.

FIG. 23 is a flowchart of calibration of the rotation angle range Wy of the mirror section 31 that is performed each time the optical scanning device 10c is powered on. In the flow chart of FIG. 23, the resonant sinusoidal voltage is defined in the same way as when the flow chart of FIG. 11 was explained.

In STEP 201, the control device 13c turns on the light source (laser light source 11).

In STEP 202, the controller 13c increases the fluctuation width Viw of the resonant sine wave voltage by a predetermined amount Δ.

In STEP203, the control device 13c determines whether or not the drive voltage Vdi≦the rated value. Then, when the determination result is affirmative, the process proceeds to STEP204. If the determination result is negative, the process proceeds to STEP204.

In STEP 204, the control device 13c determines whether or not the resonant sine wave voltage has switched from the negative half to the positive half. The negative and positive halves of the resonant sine wave voltage respectively correspond to <0[°] and >0[°] regions in the rotation angle βy (solid line) in FIG.

The control device 13c repeats the determination until the determination in STEP204 becomes affirmative, and advances the process to STEP205 as soon as the determination becomes affirmative.

In STEP205, the control device 13c clears the flag.

In STEP 206, the control device 13c determines whether or not the resonant sine wave voltage is on the + side. Then, if the determination is affirmative, the process proceeds to STEP207. If the determination is negative, the process proceeds to STEP211.

In STEP 207, the control device 13c determines whether or not the output voltage of the PD 70≧threshold (eg, the output voltage corresponding to 0.0002 [W] in FIG. 22). Then, when the determination result is affirmative, the process proceeds to STEP208. If the determination result is negative, the process returns to STEP206.

In STEP208, the control device 13c sets a flag. After that, the control device 13c returns the process to STEP206.

In STEP211, the control device 13c determines whether the flag is set. Then, when the determination result is affirmative, the process proceeds to STEP212. If the determination result is negative, the process returns to STEP202.

In STEP212, the control device 13c determines whether or not the resonant sine wave voltage is in the negative half. Then, if the determination is affirmative, the process proceeds to STEP213. If the determination is negative, the process returns to STEP201.

In STEP 213, the control device 13c determines whether or not the output voltage of the PD 70≧threshold (eg, the output voltage corresponding to 0.0002 [W] in FIG. 22). Then, when the determination result is affirmative, the process proceeds to STEP214. If the determination result is negative, the process returns to STEP212.

In STEP 214, the controller 13c determines that the optical deflector 12 is accepted. In STEP 220, the controller 13c determines that the optical deflector 12 has failed. After STEP214 or STEP220, the control device 13c advances the process to STEP215.

In STEP215, the control device 13c turns off the light source (laser light source 11).

(extended reflective surface)
FIG. 24 is a configuration diagram of a main portion for substantially increasing the area of the reflecting surface portion 57. As shown in FIG. FIG. 24 shows a configuration in which the modification is applied to the mirror section 31 of the optical scanning device 10a, but the configuration of the modification can also be applied to the photodetectors 14b to 14d.

The mirror section 31 has ribs 80l and 80r on the rear side. The ribs 80l and 80r reinforce the mirror portion 31 and are formed at symmetrical positions with respect to the rotation axis Ay. A side surface of the rib 80 l on the through hole 46 side is an extended reflecting surface portion 81 that is continuous with the reflecting surface portion 57 of the through hole 46 .

The extended reflective surface portion 81 is a plane that is continuous with the reflective surface portion 57 , so that the reflective surface portion 57 and the extended reflective surface portion 81 form one plane, and the extended reflective surface portion 81 is the extended surface reflection of the reflective surface portion 57 . becomes the face. As a result, the light-receiving surface 49 of the photodetecting portion 14a reflects the reflected passing light Lc from the reflecting surface portion 57 as well as the straight passing light Ld instead of the reflection on the extended reflecting surface portion 81. Light traveling toward the light receiving surface 49 in parallel with the passing light Lc is received as incident light. This increases the output of the photodetector 14a and improves the detection accuracy of the position of the light spot Sp (=detection accuracy of αy).

(Modification)
In the embodiment, through hole 46 has a square cross-section, but may have a rectangular cross-section.

Although the through hole 46 is formed on the rotation axis Ax in the embodiment, it may be formed at a position removed from the rotation axis Ax in the direction of the rotation axis Ay.

Although the through hole 46 is formed on the rotation axis Ax in the embodiment, it can also be formed at a position off the center O on the rotation axis Ay. In this case, the reflecting surface portion 57 is formed as a plane parallel to the rotation axis Ax. Then, the rotation angle αx of the mirror portion 31 about the rotation axis Ax can be detected from the reflected passing light Lc from the reflecting surface portion 57 . In this case, the position of the photodetector is changed according to the optical path and scanning direction of the reflected passing light Lc.

In the embodiment, the extended reflective surface portion 81 as the extended surface of the reflective surface portion 57 on the back side of the mirror portion 31 is formed using the flat side surface of the rib 80l as the raised portion. The extended reflective surface portion 81 may be limited to only the end of the side surface on the through hole 46 side (root end of the rib 80l) instead of the entire side surface of the rib 80l.

In the embodiment, the incident light La is incident on the mirror section 31 at the neutral position xy from the direction of 22.5[°], but it can also be incident at other angles.

10a to 10d optical scanner 11 laser light source 12 optical deflector 13a to 13c controller 14a to 14c photodetector 28 PSD 31...mirror section, 33...inside piezoelectric actuator, 35...outside piezoelectric actuator, 45...reflective surface portion, 46...through hole, 49, 49l, 49r...light receiving surface, 55. Inner wall surface 57 Reflective surface portion 61l, 61r, 70 PD 62, 71 Light receiving surface 75 Light shielding plate 76 Through hole 80 Rib , 81 . . . extended reflecting surface portion (extended surface).

Claims (12)

an optical deflector having a mirror portion whose surface is a reflecting surface portion that reflects incident light from a light source, is provided with a through hole that penetrates perpendicularly to the surface, and reciprocates about a predetermined rotation axis;
Within the predetermined rotation angle range of the mirror portion, out of the incident light, the light passing straight through the through hole is out of the optical path, and the incident light is reflected by the inner wall surface of the through hole. a light detection section having a light receiving area within the optical path of the reflected passing light, disposed on the back side of the mirror section, and configured to receive the reflected passing light;
a rotation detection unit that detects the rotation angle or rotation angle range of the mirror unit based on the output of the light detection unit;
with
A reflecting surface portion on which the reflected passing light is reflected on the inner wall surface of the through hole is formed as a plane parallel to the rotation axis,
A raised portion is formed on the back side of the mirror portion,
The optical scanning device , wherein the raised portion has a flat surface that reflects the rectilinear passing light toward the photodetector . The optical scanning device according to claim 1 , wherein
The optical scanning device according to claim 1, wherein a reflecting surface portion on which the reflected passing light is reflected on the inner wall surface of the through hole is formed as a metal surface. an optical deflector having a mirror portion whose surface is a reflecting surface portion that reflects incident light from a light source, is provided with a through hole that penetrates perpendicularly to the surface, and reciprocates about a predetermined rotation axis;
Within the predetermined rotation angle range of the mirror portion, out of the incident light, the light passing straight through the through hole is out of the optical path, and the incident light is reflected by the inner wall surface of the through hole. a light detection section having a light receiving area within the optical path of the reflected passing light, disposed on the back side of the mirror section, and configured to receive the reflected passing light;
a rotation detection unit that detects the rotation angle or rotation angle range of the mirror unit based on the output of the light detection unit;
provided with,
a reflecting surface portion on which the reflected passing light is reflected on the inner wall surface of the through hole is formed as a metal surface;
A raised portion is formed on the back side of the mirror portion,
The optical scanning device , wherein the raised portion has a flat surface that reflects the rectilinear passing light toward the photodetector . The optical scanning device according to claim 1 or 3,
An optical scanning device according to claim 1, wherein the raised portion is formed with an extension surface of the reflecting surface portion of the through hole. The optical scanning device according to any one of claims 1 to 4,
The mirror section has a first rotation axis that is the predetermined rotation axis, and a second rotation axis that is different from the predetermined rotation axis and perpendicular to the first rotation axis at the center of the mirror section. reciprocatingly rotates around
The optical scanning device, wherein the through hole is formed on the second rotating shaft. The optical scanning device according to claim 5,
The optical scanning device, wherein the mirror section reciprocally rotates about the first rotation axis and the second rotation axis in resonance and non-resonance, respectively. The optical scanning device according to any one of claims 1 to 6,
The light detection unit has a light receiving surface that receives the reflected passing light, and outputs an electrical signal related to a light receiving position on the light receiving surface,
The optical scanning device, wherein the rotation detection section detects a rotation angle of the mirror section about the predetermined rotation axis based on the electrical signal. The optical scanning device according to claim 7,
The optical scanning device, wherein the photodetector is a PSD. The optical scanning device according to claim 7,
setting the center of the rotation angle range of the mirror unit around the predetermined rotation axis as the central rotation angle,
The light-receiving surface of the light detection section is a first surface portion on one side in the scanning direction of the reflected passing light with respect to the light-receiving position of the reflected passing light when the mirror section is at the central rotation angle. and a second surface portion on the other side,
the photodetector includes a first PD having a light receiving surface as the first surface portion and a second PD having a light receiving surface as the second surface portion;
The optical scanning device, wherein the output of the photodetector includes the output of the first PD and the output of the second PD. an optical deflector having a mirror portion whose surface is a reflecting surface portion that reflects incident light from a light source, is provided with a through hole that penetrates perpendicularly to the surface, and reciprocates about a predetermined rotation axis;
Within the predetermined rotation angle range of the mirror portion, out of the incident light, the light passing straight through the through hole is out of the optical path, and the incident light is reflected by the inner wall surface of the through hole. a light detection section having a light receiving area within the optical path of the reflected passing light, disposed on the back side of the mirror section, and configured to receive the reflected passing light;
a rotation detection unit that detects the rotation angle or rotation angle range of the mirror unit based on the output of the light detection unit;
with
The light detection unit has a light receiving surface that receives the reflected passing light, and outputs an electrical signal related to a light receiving position on the light receiving surface,
the rotation detection unit detects a rotation angle of the mirror unit about the predetermined rotation axis based on the electrical signal;
setting the center of the rotation angle range of the mirror unit around the predetermined rotation axis as the central rotation angle,
The photodetector is
a PD having a light receiving surface extending in the scanning direction of the reflected passing light;
a light-shielding plate covering the light-receiving surface of the PD and having transmission holes formed on one side and the other side with respect to the scanning direction position when the mirror portion is at the central rotation angle;
An optical scanning device comprising: The optical scanning device according to claim 10, wherein
The position of the transmission hole in the light shielding plate is the scanning direction position of the reflected passing light when the mirror section is at the rotation angle at both ends of the rated rotation range of the mirror section about the predetermined rotation axis. An optical scanning device characterized by being set to . The optical scanning device according to any one of claims 1 to 11,
An optical scanning device, wherein the incident direction of the incident light is set so as not to be perpendicular to the surface over the entire predetermined rotation angle range of the mirror section.

Images