JP2013037324A - Optical scanner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner capable of easily emitting a light beam to each pixel in an exposure target area of the light beam even if there is no light-emitting timing table.SOLUTION: An optical scanner comprises: a light scanning part 1 that oscillates a reflecting mirror around each axis of first and second axes perpendicular to each other and is formed in a manner capable of applying Lissajous scanning to the light beam within an exposure target area; a phase detection part 2 for detecting an oscillation phase around each axis; a light source part 3 for emitting the light beam to the reflecting mirror; a scan control part 4 for driving the light scanning part 1 by setting oscillation cycles Tand Taround each axis and changing scan amplitude around the second axis for each half cycle of the oscillation cycle Taround the second axis by a fixed amount, so that a scanning line pair S and S, which are approximately parallel to each other in a scanning direction around the first axis, are present on a Lissajous scan trajectory in the half cycle of T; and a light source control part 5 for exposing only a phase section corresponding at the time of scanning the scanning line pair S and S to the light beam from the light source part 3, on the basis of the oscillation phase detected by the phase detection part 2.

Description

  The present invention relates to an optical scanning device that performs Lissajous scanning of a light beam within an irradiation target region of the light beam.

  2. Description of the Related Art Conventionally, an optical scanning apparatus that performs Lissajous scanning of a light beam within a light beam irradiation target region is known. As this type of optical scanning device, for example, a light source unit that projects a light beam at a preset projection timing, an optical scanning unit that includes a two-dimensional galvanometer mirror, and scanning control that drives the optical scanning unit (For example, refer to Patent Document 1), for example, light that performs Lissajous scanning of a light beam in an irradiation target region and measures a distance to an object existing in the irradiation target region It is used as an optical scanning means such as a distance measuring device.

  In this type of optical scanning device, for example, the scanning control unit drives the optical scanning unit at a driving frequency that is initially set in accordance with the resonance frequency of each oscillation direction of the two-dimensional galvanometer mirror. In addition, the light projection timing of the light beam projected from the light source unit is initially set so that the light beam along the Lissajous scanning locus determined according to the initially set drive frequency can be irradiated to each pixel predetermined in the irradiation target region. Has been.

JP-A-7-175005

  However, in the conventional optical scanning device, in order to uniformly irradiate each pixel set in the irradiation target region with the light beam scanned by the Lissajous scanning type optical scanning unit, a table of the light projection timing is determined in advance. There was room for improvement because it had to be stored in the storage unit.

  Therefore, the present invention has been made paying attention to the above-described problems, and provides an optical scanning device that can easily irradiate each pixel in an irradiation target region without a projection timing table. For the purpose.

  In order to achieve the above object, an optical scanning device according to the present invention oscillates a reflecting mirror around each axis of a first axis and a second axis orthogonal to each other and is irradiated with a light beam incident on the reflecting mirror. An optical scanning unit formed so that the light beam can be Lissajous scanned in the region, a phase detection unit for detecting the oscillation phase around each axis of the reflection mirror, and a light beam projected toward the reflection mirror A pair of scanning lines that are substantially parallel to each other in the scanning direction around the first axis in the Lissajous scanning trajectory of the light beam in the half cycle of the second oscillation period that is the oscillation period around the second axis. Are set such that the first oscillation cycle and the second oscillation cycle are oscillation cycles around the first axis, and the second axis is set every half cycle of the second oscillation cycle. The optical scanning unit is driven by changing the scanning amplitude of the surroundings by a certain amount. And a light source control unit that projects the light beam from the light source unit only in a phase section corresponding to the scanning line pair scanning based on the oscillation phase detected by the phase detection unit. And comprising.

  According to the optical scanning device of the present invention, an optical scanning unit capable of performing a Lissajous scan in a region to be irradiated with a light beam incident on a reflection mirror that can swing around the first and second axes orthogonal to each other. In the Lissajous scanning locus in the half cycle of the second oscillation period (oscillation period around the second axis), the first oscillation line is present so that there are scanning line pairs substantially parallel to each other in the scanning direction around the first axis. A dynamic period (oscillation period around the first axis) and a second oscillation period are set, and the scanning amplitude around the second axis is changed by a certain amount every half period of the second oscillation period, Since the light beam is projected from the light source unit only in the phase section corresponding to the scanning line pair scanning based on the surrounding oscillation phase, the rotation about the second axis is performed every half cycle of the second oscillation cycle. The flatness of the Lissajous scanning trajectory with respect to the scanning direction of each scanning line can be changed. It can be projected a light beam during scanning. Therefore, it is possible to irradiate a light beam over the entire irradiation target area by dot-sequential scanning similar to raster scanning even in Lissajous scanning simply by projecting a light beam at constant phase increments within the phase interval. it can. Thereby, even if there is no light beam projection timing table, it is possible to easily irradiate each pixel in the irradiation target region with the light beam.

It is a block diagram which shows one Embodiment of the optical scanning device by this invention. It is a perspective view which shows one structural example of the optical scanning part used in the said embodiment. It is explanatory drawing which shows the Lissajous scanning locus | trajectory of the light beam by the said optical scanning part. It is a side view which shows one structural example of the phase detection part used in the said embodiment. It is explanatory drawing which shows the change of the scanning amplitude around the X-axis of the said optical scanning part. It is explanatory drawing which shows the change of the scanning amplitude around the Y-axis of the said optical scanning part. It is a figure explaining the area which projects a light beam from a light source part based on the phase information of the phase detection part of this embodiment, (a) is the elements on larger scale of FIG. 5, (b) is FIG. It is a partial enlarged view. It is explanatory drawing which shows the condition which changed the flatness of the Lissajous scanning locus by the said optical scanning part. It is a figure which shows the Lissajous scanning locus | trajectory after the completion of scanning about the whole irradiation object area | region by the said optical scanning part. It is a figure which shows another Lissajous scanning locus | trajectory after the completion of scanning about the whole irradiation object area | region by the said optical scanning part. It is a flowchart explaining operation | movement of the said embodiment. It is a figure which shows the condition which provided the adjustment part in the said optical scanning part, and inclined the whole Lissajous scanning locus | trajectory of FIG. It is explanatory drawing which shows another Lissajous scanning locus | trajectory of the light beam by the said optical scanning part. It is explanatory drawing which shows another Lissajous scanning locus | trajectory of the light beam by the said optical scanning part. It is a perspective view which shows the other structural example of the said optical scanning part.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an embodiment of an optical scanning device according to the present invention.
In FIG. 1, an optical scanning device 10 according to the present embodiment performs Lissajous scanning of laser light incident on a reflecting mirror within a laser light irradiation target region (hereinafter, simply referred to as “target region”). In the following description, the case where the optical scanning device is used as an optical scanning unit of an optical distance measuring device that measures a distance to an object existing in the target region by performing Lissajous scanning with laser light in the target region will be described. .

  The optical scanning device 10 according to the present embodiment includes an optical scanning unit 1, a phase detection unit 2, a light source unit 3, a scanning control unit 4, and a light source control unit 5.

  The optical scanning unit 1 oscillates the reflection mirror around each of the first axis (X axis) and the second axis (Y axis) orthogonal to each other, and the reflection mirror oscillates to form the reflection mirror. The incident laser beam L is formed so as to be capable of Lissajous scanning in the target region, and is driven and controlled by the scanning control unit 4. For example, as shown in FIG. 2, the optical scanning unit 1 includes an X-axis scanning device 8A in which a reflecting mirror 7A is swingably supported by a pair of torsion bars 6A and 6A, and a reflecting mirror 7B in a pair of torsion bars 6B. , 6B and two scanning devices of a Y-axis scanning device 8B supported so as to be swingable, and are configured such that the axes of the torsion bars 6A, 6B of the scanning devices 8A, 8B are orthogonal to each other.

  Here, in the present embodiment, the X-axis scanning device 8A becomes a scanning mirror in the horizontal scanning direction of the target region shown in FIG. 2, and the Y-axis scanning device 8B becomes a scanning mirror in the vertical scanning direction shown in FIG. Has been placed. That is, in the present embodiment, the scanning direction around the first axis (X axis) corresponds to the horizontal scanning direction of the target area, and the scanning direction around the second axis (Y axis) corresponds to the vertical scanning direction of the target area. This will be described below.

Specifically, the scanning coordinate X in the horizontal scanning direction in the target region by the reflecting mirror 7A can be expressed as, for example, the following equation (1).
X = A _x · sin (2πt / T _x −θ ₀ ) (1)
Further, the scanning coordinate Y in the vertical scanning direction in the target region by the reflecting mirror 7B can be expressed as the following equation (2), for example.
Y = A _y · sin (2πt / T _y −θ ₀ ) (2)
Here, A _x is the scanning amplitude of the reflecting mirror 7A, A _y is the scanning amplitude of the reflecting mirror 7B, t is the elapsed time (time) from the scanning start reference point (t = 0), and T _x Is the oscillation cycle around the X axis, T _y is the oscillation cycle around the Y axis, θ ₀ is the oscillation phase at the scanning start reference point (t = 0), and the X axis at t = 0 The phase around and the phase around the Y axis are the same.

Note that T _x and T _y are set by the scanning control unit 4 so that, for example, T _y is three times T _x as described later. In this case, when A _x > A _y is set, the Lissajous scanning trajectory of the laser light L by the optical scanning unit 1 becomes a flat S-shape collapsed in the scanning direction around the Y axis as shown in FIG. The flatness of the S-shaped Lissajous scanning trajectory can be expressed as, for example, A _y / A _x . In the present embodiment, corresponds to the first swing period T _x is according to the present invention, T _y corresponds to a second oscillating period according to the present invention.

  In FIG. 2, the reflection mirrors 7A and 7B of the X-axis scanning device 8A and the Y-axis scanning device 8B are both arranged upward, and the plane mirror 9 is disposed to face the reflection mirrors 7A and 7B. The laser beam L reflected by the reflection mirror 7A of the X-axis scanning device 8A is received by the plane mirror 9 and reflected toward the Y-axis scanning device 8B, but the X-axis scanning device 8A and The reflecting mirrors 7A and 7B of the Y-axis scanning device 8B are arranged in parallel and facing each other, and the laser beam L reflected by the reflecting mirror 7A of the X-axis scanning device 8A is reflected by the reflecting mirror of the Y-axis scanning device 8B. You may make it receive directly by 7B. The scanning device driving method may be any method such as an electromagnetic driving method, an electrostatic driving method, or a piezoelectric driving method, and a known technique can be applied.

The phase detector 2 detects the oscillation phase θ around the X-axis and Y-axis of the reflection mirror. For example, as shown in FIG. 4, the oscillation axis on the back side of the reflection mirrors 7A and 7B. A light emitting element 11 such as an LED provided immediately below (X axis, Y axis) and a light receiving element 12 that receives light from the light emitting element 11 reflected by the back surfaces of the reflecting mirrors 7A and 7B; The reflected light of the light projected from the light emitting element 11 on the back surfaces of the reflecting mirrors 7A and 7B is received by the light receiving element 12, and the phase information of the swinging of the reflecting mirrors 7A and 7B is obtained from the change in the amount of the received light. It is configured to output to the control unit 4 and the light source control unit 5. The phase information output from the phase detector 2 is, for example, a sine wave signal in which a peak output appears in a half period of the oscillation periods T _x and T _y of the reflection mirrors 7A and 7B. At the time of this peak output, the reflection mirrors 7A and 7B are in a horizontal state.

  The light source unit 3 projects a pulsed laser beam L toward the reflection mirror 7A, and includes, for example, a light source and a light projecting optical system (not shown). The light source is, for example, a laser diode, and emits pulsed laser light L by emitting light in response to a command from the light source control unit 5 based on phase information as will be described later. The light projecting optical system includes, for example, a collimator lens, and converts the laser light L emitted from the light source into parallel light.

  The laser beam L projected from the light source unit 3 is reflected and scanned by the reflection mirrors 7A and 7B, and is Lissajous scanned in the target area. The laser light L (reflected light) reflected by the object existing in the target region is reflected by the reflection mirrors 7A and 7B. For example, the light receiving unit 13 (for example, a photosensor) of the optical distance measuring device Is received. The light reception timing of the reflected light by the light receiving unit 13 and the light projection command signal of the laser light L from the light source control unit 5 are input to the distance measuring unit 14 of the optical distance measuring device. Thereby, the distance measuring unit 14 of the optical distance measuring device measures the distance to the object existing in the target region based on the time difference between the input timing of the light projection command signal from the light source control unit 5 and the light receiving timing, for example. To do. Thus, the optical scanning device 1 according to the present embodiment is used as an optical scanning unit of the optical distance measuring device.

The scanning control means 4 is for controlling the driving of the optical scanning unit 1, the Lissajous scanning locus of the laser beam L in a half period of the second oscillating period T _y, X-axis in the scanning direction (in FIG. 2 The first oscillation period _Tx and the second oscillation period _Ty are set so that there are scanning line pairs S and S that are substantially parallel to each other in the horizontal scanning direction shown in _FIG . every half cycle, the scan amplitude a _y of the Y-axis is varied by a constant amount .DELTA.A _y, and is configured to drive the optical scanning unit 2.

Specifically, the scan control unit 4, for example, as shown in FIGS. 5 and 6, when the second swing period T _y in other words set (three times of the first swing period T _x, X-axis of the oscillation frequency f _x set to three times the oscillation frequency f _y of the Y axis), and to match the swing phase theta ₀ about each axis in the scanning start reference point (t = 0), the scanning device A drive signal corresponding to each oscillation cycle and the maximum scanning amplitude described later is input to 8A and 8B. As a result, as shown in FIG. 3, a pair of scanning lines S and S (scans indicated by thick lines in FIG. 3) are substantially parallel to the Lissajous scanning locus of the laser light L in the scanning direction around the X axis (horizontal scanning direction). Line) can be present.

For example, when the oscillation phase θ ₀ around each axis is calculated as the start of the time t when the phase θ ₀ is 3π / 4, the scanning coordinate X in the horizontal scanning direction in the target region by the reflecting mirror 7A is expressed by the following equation (3). It can be expressed as follows.
X = A _x · sin (2πt / T _x −3π / 4) (3)
Further, the scanning coordinate Y in the vertical scanning direction in the target area by the reflecting mirror 7B can be expressed as the following equation (4).
Y = A _y · sin (2πt / 3T _x −3π / 4) (4)

Further, as described above, the scanning control unit 4 sets the oscillation period around each axis so that the Lissajous scanning locus includes the scanning line pair S, S, and for example, has a constant scanning amplitude around the X axis. Oscillate with A _x (maximum amplitude value | A _x | max), and about the Y axis, the scanning amplitude A _y around the second axis is set to a predetermined maximum amplitude value every half cycle of the second oscillation period T _y. It is configured to change and swing by a certain amount ΔA _y between | A _y | max and a predetermined minimum amplitude value | A _y | min.

More specifically, as illustrated in FIGS. 5 to 7, the scanning control unit 4 performs fluctuations around the X axis and the Y axis with the maximum amplitude value | A _x | max and the maximum amplitude value | A _y | max. moving each to start, when the half cycle of the second swing period T _y, for Y-axis to change the scan amplitude a _y by subtracting a fixed amount .DELTA.A _y. As a result, the flatness A _y / A _x of the Lissajous scanning trajectory can be changed. Therefore, as shown in FIG. 8, the scanning line pair S, S has a half-cycle of the second oscillation cycle T _y as shown in FIG. The drive of the optical scanning unit 2 can be controlled as if it is shifted by a substantially constant distance ΔY in the scanning direction (vertical scanning direction) around the Y axis.

Here, the shift amount (constant distance) ΔY of the pair of scanning lines S and S coincides with the change amount ΔA _y of the scanning amplitude A _y for each half cycle of the second oscillation cycle T _y . Therefore, the shift amount ΔY can be appropriately set by adjusting the change amount ΔA _y of the scanning amplitude A _y according to the number of scanning lines in the horizontal scanning direction required in the target region. Note that the scan controller 4 determines whether or not scanning a half cycle has been completed the second oscillating period T _y, for example, based on the Y-axis of the phase information input from the phase detector 2 performs The timing for changing the scanning amplitude _Ay around the second axis is determined.

Scanning control unit 4, the flatness control of Lissajous scanning path shown in FIG. 8, performed every half cycle of the second swing period T _y, as shown in FIG. 6, the scan amplitude A _y of the Y-axis is smallest When it coincides with the amplitude value | A _y | min, the scanning of the entire target region (one frame) is completed, and the swing around the Y axis of the next scanning is made a fixed amount ΔA from the minimum amplitude value | A _y | min. _{y is} executed from the amplitude value increased (changed).

In FIG. 6, since the magnitude of ΔA _y is exaggerated for the sake of clarity, the amplitude step for each half cycle of the second oscillation period T _y is exaggerated. ΔA _y is set so that is small. Similarly, in FIG. 6, | A _y | min is shown large for clarity, but for example, | A _y | min = 0 is set, and the coordinate Y = 0 in the vertical scanning direction of the target region is scanned. It is good to do. By setting ΔA _y and | A _y | min in this way, as shown in FIG. 9, a scanning trajectory in which scanning line pairs S and S substantially parallel to each other in the horizontal scanning direction are densely present in the vertical scanning direction is obtained. The laser light can be Lissajous scanned in the target area.

Further, the time required for one frame (frame rate) becomes longer as the constant amount ΔA _y for changing the scanning amplitude A _y becomes smaller, and becomes shorter as the constant amount ΔA _y becomes larger. In this way, the frame rate can be easily controlled simply by adjusting the value of ΔA _y .

When the maximum amplitude value | A _y | max around the Y axis is made larger than the value set in FIG. 9, the entire Lissajous scanning trajectory after completion of one frame is scanned in the horizontal scanning direction as shown in FIG. It can be easily expanded without changing the line density.

The light source control unit 5 instructs the light source unit 3 to project laser light, and responds to scanning of the scanning line pair S and S based on the oscillation phase detected by the phase detection unit 2. The light source unit 3 is configured to project the laser beam only in the phase section (sections A, C, D, and F corresponding to the thick lines in FIGS. 7A and 7B). Here, each phase section shown by (a) to (a) in FIG. 7 (a) and FIG. 7 (b) respectively corresponds to the scanning trajectory of (a) to (c) shown with an arrow indicating the scanning direction in FIG. . For example, the light source control unit 5 determines whether or not the detected value of the oscillation phase detected by the phase detection unit 2 is within the phase interval of A, U, D, F, and is within the phase interval. When the determination is made, the laser beam is projected when the detected value of the oscillation phase of the phase detector 2 coincides with the oscillation phase of the constant phase increment Δθ that is predetermined as the laser beam projection timing. The light source unit 3 is configured to command. The constant phase increment Δθ is set, for example, in correspondence with the interval of each pixel predetermined in a matrix in the target region. Thus, every half cycle of the second swing period T _y, substantially parallel scan lines versus each other in the horizontal scanning direction of the target area S, the laser irradiation position interval corresponding to the phase increment Δθ with the predetermined on S Light can be applied to the target area.

  Next, the operation of the optical scanning device 10 according to the present embodiment will be described with reference to the flowchart of FIG.

First, in step S1, by turning on the start switch of the apparatus, based on the drive control of the scanning control unit 4, the oscillation of the optical scanning unit 1 about the X axis and the Y axis is changed to the maximum amplitude value | A _x | max and the maximum. Start with an amplitude value | A _y | max.

  In step S2, the phase detection unit 2 detects each oscillation phase of oscillation about the X axis and the Y axis, and outputs the phase information to the light source control unit 5. The light source control unit 5 outputs the phase information about each axis. To get.

  In step S <b> 3, the light source control unit 5 determines whether or not the detected value of the oscillation phase from the phase detection unit 2 is within the phase interval (A, C, D, F) of the laser light irradiation range. Determine. Here, when it determines with it being in the phase area of an irradiation range, it progresses to step S4. If it is determined that it is not within the phase section of the irradiation range (that is, if it is the section of A and B), the process proceeds to step S6.

  In step S4, the light source control unit 5 determines whether or not the detected value of the oscillation phase from the phase detection unit 2 coincides with an oscillation phase with a predetermined constant phase increment within the phase section of the irradiation range. To do. Here, when it is determined that the detected value coincides with a predetermined rocking phase in a constant phase step, the light source control unit 5 instructs the light source unit 3 to project laser light, and the process proceeds to step S5.

  In step S5, the light source unit 3 outputs a laser beam and proceeds to step S6. In step S4, if the light source control unit 5 determines that the detected value does not coincide with the predetermined rocking phase in a constant phase step, the process returns to step S2.

In step S6, the scan control unit 4, based on a determination of whether the scanning of a half cycle has been completed the second oscillating period T _y, for example, the Y-axis of the phase information input from the phase detector 2 Do it. Here, when the scanning of the half cycle of the second swing period T _y is judged to be ended, the process proceeds to step S7. Note that, in step S6, if the scanning of the half cycle of the second swing period T _y is found not ended, the process proceeds to step S8.

In step S7, the scanning control unit 4 reduces the magnitude (for example, current value or voltage value) of the drive signal input to the Y-axis scanning device 8B by a certain amount, for example, as shown in FIG. 7B. as such, small fixed amount .DELTA.A _y set in advance the scan amplitude a _y of the Y-axis, and start scanning the next half period (T y _{/ 2),} the process proceeds to step S8.

In step S8, the scanning control unit 4 determines whether or not the scanning amplitude _Ay around the Y axis matches the minimum amplitude value | _Ay | min. The minimum of the scanning amplitude A _y is, for example, a value (current value or voltage value) in which the magnitude (current value or voltage value) of the drive signal input to the Y-axis scanning device 8B corresponds to the minimum amplitude value | A _y | min. This is done by determining whether or not the voltage value matches. If it is determined that the scanning amplitude _Ay does not match the minimum amplitude value | _Ay | min, the process returns to step S2. On the other hand, if it is determined that they match, scanning for one frame is completed.

Although not shown, when scanning is continued, for example, from the amplitude value obtained by increasing (changing) the swing of the next frame around the Y axis by a certain amount ΔA _y from the minimum amplitude value | A _y | min. Let it run. In this case, when the scanning amplitude _Ay about the Y axis coincides with the maximum amplitude value | _Ay | max, scanning for one frame is completed, and when scanning is further performed, the operations from Steps S1 to S8 described above are performed. Do. By repeating these operations, scanning for one frame can be performed a predetermined number of times.

With this configuration, a laser measuring device 1 according to this embodiment, the Lissajous scanning trajectory in half cycle of the second swing period T _y, substantially parallel scan lines vs. each other in the scanning direction of the X axis S, S as but present, and sets the first oscillating period T _x and the second oscillating period T _y, the scan amplitude width a _y of the second axis for each half cycle of the second swing period T _y Since the laser light is emitted from the light source unit 3 only in the phase section corresponding to the scanning line pair S and S based on the oscillation phase around each axis, the light amount is changed by a certain amount ΔA _y . every half cycle of the second swing period T _y, of the scanning direction of the Y axis, it is possible to change the flatness of the Lissajous scanning locus of each scanning line pair S, to project a light beam upon scanning of S be able to. Therefore, it is possible to irradiate a light beam over the entire irradiation target area by dot-sequential scanning similar to raster scanning even in Lissajous scanning simply by projecting a light beam at constant phase increments within the phase interval. it can. Thereby, even if there is no light beam projection timing table, it is possible to easily irradiate each pixel in the irradiation target region with the light beam.

Moreover, as in this embodiment, if you set the second oscillating period T _y to 3 times the first oscillating period T _x, during 1 frame shown in FIG. 9, for irradiating actually laser beam The effective scanning time is the time required for scanning a, c, d, and f shown in FIG. Therefore, when the time required for one frame is T, the effective scanning time can be 2 / 3T.

Further, as in the present embodiment, the scanning amplitude A _y around the Y axis is decreased from the maximum amplitude value | A _y | max by a certain amount to the minimum amplitude value | A _y | min to complete scanning for one frame. The next frame is swung around the Y axis from the amplitude value that is increased (changed) by a certain amount ΔA _y from the minimum amplitude value | A _y | min. Since the scanning amplitude around the Y axis does not change significantly at the time of transition, for example, the generation of noise from the inside of the apparatus due to a sudden change in scanning amplitude can be suppressed, and the Y axis device 8B and the like can be suppressed. The impact to the can also be suppressed. Although not shown, the next frame may be executed from the minimum amplitude value | A _y | min. In this case, since there is no change in the scanning amplitude at the time of transition to the next frame, noise and impact on the Y-axis device 8b due to the change of the scanning amplitude at the time of transition to the frame can be eliminated, and scanning at each frame is performed. The number of line pairs S and S can be made completely coincident.

Contrary to this embodiment, the scanning amplitude _Ay around the Y axis is increased from the minimum amplitude value | A _y | min by a certain amount to the maximum amplitude value | A _y | max to complete scanning for one frame. is, the Y-axis of the swing of the next one frame, the maximum amplitude value | from the amplitude value obtained by a predetermined amount lower than max, or the maximum amplitude value | _| a _y be caused to run from the max _| a _y , Noise and shock can be suppressed or prevented.

In the present embodiment, as described above, the scanning control unit 4 has been described as being configured so that the scanning amplitude _Ay around the Y axis does not change significantly at the time of transition to the next frame. However, the present invention is not limited to this, and swinging around the Y-axis is started with either one of the maximum amplitude value | A _y | max or the minimum amplitude value | A _y | min, and the second swing period T _y The scanning amplitude _Ay around the Y axis is changed by a certain amount every half cycle, and when the scanning amplitude _Ay matches the other amplitude value, the scanning of the entire target region is completed, and the Y axis of the next scanning is completed. The configuration may be such that the swinging around is executed from one amplitude value.

  In the present embodiment, as shown in FIG. 9, the case where the Lissajous scanning is performed in a state where the pair of scanning lines S and S is inclined by the angle θ ′ with respect to the horizontal scanning direction in the target region has been described. Not limited to this, as shown in FIG. 12, Lissajous scanning may be performed in a state in which the scanning line pair S, S is substantially parallel to the horizontal scanning direction in the target region.

  In this case, specifically, the optical scanning unit is an adjustment unit (not shown) that adjusts the installation angle of the optical scanning unit 1 with respect to the target region so that the horizontal scanning direction and the scanning line pair S and S are substantially parallel. It prepares for 2 grades. Although not shown, the adjustment unit is configured to rotate the entire devices 8A and 8B so that, for example, the entire Lissajous scanning locus by the optical scanning unit 1 is rotated by the angle θ ′. Thus, by adjusting the scanning line pair S, S so as to be substantially parallel to the horizontal scanning direction in the target region, the entire scanning locus after one frame scanning can be made substantially rectangular. As a result, as shown in FIG. 12, the rectangular target region and the entire region of the scanning trajectory can be substantially matched, and the rectangular target region can be scanned more efficiently.

Further, in the present embodiment, the optical scanning unit 2 has been described in the case of drawing an S-shaped scanning locus as illustrated in FIG. 3 and the like, but the present invention is not limited to this, and for example, an S-shaped pattern illustrated in FIG. A scanning trajectory combining N S-shaped scanning trajectories, such as a scanning trajectory combining two scanning trajectories or a scanning trajectory combining three S-shaped scanning trajectories shown in FIG. Also good. In these cases, the scan control unit 4 configured to set the second oscillating period T _y an odd multiple of the first swing period T _x. For example, in the case of FIG. 13, the second oscillation period T _y is set to five times the first oscillation period T _x , and in the case of FIG. 14, the second oscillation period T _{y is set} to the first oscillation period T _y . Set to 7 times _x . Thus, to draw the scan path that combines the N a S-shaped scan _{trajectory, T y = (2N + 1} ) · T second oscillating period so that the _{x T y} a first oscillating period _{T x} Should be set. For example, in the case of FIG. 13, there are two pairs of scanning lines S, S, S1, S1, and S2, S2. In the case of FIG. 14, there are three pairs of scanning lines S3, S3, S4, S4 and S5, S5. In each case, any scanning line pair may be used as the scanning line for laser light irradiation.

  In the present embodiment, the case where the optical scanning unit 1 is configured by combining the X-axis scanning device 8A and the Y-axis scanning device 8B has been described. However, the present invention is not limited to this, and as shown in FIG. The scanning unit 1 is swingably supported by an inner torsion bar 21 and is formed in a frame shape surrounding the inner movable unit 22 and an inner movable unit 22 having a reflection mirror 7 formed at the center of the surface. And an outer movable portion 24 supported so as to be swingable by an outer torsion bar 23 that extends in a direction orthogonal to the axis of the inner torsion bar 21.

  In the present embodiment, the scanning direction around the first axis (X axis) corresponds to the horizontal scanning direction of the target area, and the scanning direction around the second axis (Y axis) corresponds to the vertical scanning direction of the target area. However, the present invention is not limited to this, and the scanning direction around the first axis (X axis) corresponds to the vertical scanning direction of the target area, and the scanning direction around the second axis (Y axis) is the horizontal of the target area. The configuration may be such that each scanning device 8A, 8B is arranged so as to correspond to the scanning direction. In this case, the scanning trajectory is a trajectory obtained by rotating the S-shape shown in FIG. 3 by 90 °, and the scanning line pairs S and S included in the scanning trajectory are shifted by a certain amount in the horizontal scanning direction.

  In this embodiment, the case where the light beam is a laser beam has been described. However, the present invention is not limited to this, and the light beam may be a light emitting element (LED).

  In the present embodiment, the case where the optical scanning device 10 is used as the optical scanning unit of the optical distance measuring device has been described. Can also be used. In this case, the light source unit 3 uses, for example, a pair of scanning lines S and S shown in FIG. 8 having the same scanning direction as the image light intensity-modulated in accordance with a video signal input from the outside, or By irradiating only the phase interval (see FIG. 7) corresponding to the pair of scanning lines S and S of D and F, for example, an image can be displayed by dot sequential scanning similar to a cathode ray tube (CRT). it can. Note that the raster scan video signal is input in the order of the horizontal raster scan lines positioned at regular intervals in the vertical direction of the cathode ray tube, for example, so that the video signal for one frame is temporarily stored in a memory or the like. The arrangement of the video signals of the raster scanning lines is changed in accordance with the scanning order of the scanning line pairs S and S. In the case where the optical scanning device 10 is used as a light scanning unit of a projector, color display is possible if RGB three-color light is used as a light beam.

DESCRIPTION OF SYMBOLS 1 ... Optical scanning part 2 ... Phase detection part 3 ... Light source part 4 ... Scanning control part 5 ... Light source control units 6A, 6B ... Torsion bars 7A, 7B, 7 Reflective mirrors 8A, 8B Scanning device 10 Optical scanning device 21 Inner torsion bar 22・ ・ ・ ・ ・ Inner movable part 23 ... External torsion bar 24 ... External movable part

Claims (6)

An optical scanning formed by swinging the reflecting mirror around each of the first axis and the second axis orthogonal to each other so that the light beam can be Lissajous scanned within the irradiation target area of the light beam incident on the reflecting mirror And
A phase detector for detecting the oscillation phase around each axis of the reflecting mirror;
A light source unit that projects a light beam toward the reflection mirror;
The Lissajous scanning trajectory of the light beam in the half cycle of the second oscillation cycle that is the oscillation cycle around the second axis is such that there are scanning line pairs that are substantially parallel to each other in the scanning direction around the first axis. A first oscillation cycle and a second oscillation cycle that are oscillation cycles around the first axis are set, and a scanning amplitude around the second axis is set for each half cycle of the second oscillation cycle. A scanning control unit that drives the optical scanning unit by changing a certain amount;
Based on the oscillation phase detected by the phase detection unit, the light source control unit that projects the light beam from the light source unit only in a phase section corresponding to the scanning line pair scanning,
An optical scanning device comprising:   The scanning control unit sets the second oscillation period to an odd multiple of the first oscillation period, matches the oscillation phase around each axis at the scanning start reference point, and about the first axis Oscillating at a constant scanning amplitude, and about the second axis, the scanning amplitude around the second axis is set to a predetermined maximum amplitude value and a predetermined minimum amplitude value every half cycle of the second oscillation period. The optical scanning device according to claim 1, wherein the optical scanning device is rocked while changing by a certain amount.   The scanning control unit starts swinging around the second axis with one of the maximum amplitude value and the minimum amplitude value, and performs the second rotation every half cycle of the second swing cycle. The scanning amplitude around the axis is changed by the predetermined amount, and when the scanning amplitude around the second axis coincides with the other amplitude value, the scanning of the entire irradiation target region is completed, and the second scanning of the next scanning is completed. 3. The optical scanning device according to claim 2, wherein the swing around the axis is executed from the other amplitude value or from an amplitude value changed by the predetermined amount from the other amplitude value. 4.   The scanning control unit starts swinging around the second axis with one of the maximum amplitude value and the minimum amplitude value, and performs the second rotation every half cycle of the second swing cycle. The scanning amplitude around the axis is changed by the predetermined amount, and when the scanning amplitude around the second axis coincides with the other amplitude value, the scanning of the entire irradiation target region is completed, and the second scanning of the next scanning is completed. The optical scanning device according to claim 2, wherein the swing around the axis is executed from the one amplitude value.   5. The optical scanning device according to claim 1, wherein the second oscillation period is three times the first oscillation period.   An adjustment unit is provided for adjusting an installation angle of the optical scanning unit with respect to the irradiation target region so that a horizontal scanning direction or a vertical scanning direction of the irradiation target region is substantially parallel to the scanning line pair. The optical scanning device according to any one of claims 1 to 5.