JP6365075B2 - Laser scanning device - Google Patents

Description

  The present invention relates to a laser scanning device using a scanning mirror.

  2. Description of the Related Art A laser scanning device that performs optical scanning by irradiating a resonant scanning mirror such as a MEMS (Micro Electro Mechanical Systems) scanning mirror with laser light is known. Such a laser scanning device detects a scanning amplitude that is an optical scanning amplitude of the MEMS scanning mirror, and uses the detection result to control the scanning amplitude to a desired value. As a method for detecting this scanning amplitude, a method is known in which the interval between pulse signals obtained from a photosensor arranged in the vicinity of the end of a scanning region of laser light is measured (for example, see Patent Document 1).

JP 2004-110030 A

  A resonant scanning mirror uses resonance to gain scanning amplitude. This resonant scanning mirror has a high Q value. Further, the resonance scanning mirror rapidly increases the scanning amplitude when the frequency of the drive signal is close to the resonance frequency (natural frequency) of the MEMS structure, and rapidly when the frequency of the drive signal deviates from the resonance frequency. The scan amplitude is reduced. As a result, the resonant scanning mirror requires strict drive signal frequency adjustment. In addition, since this resonance frequency changes depending on manufacturing variations, temperature, atmospheric pressure, and the like, it is necessary to adjust the drive signal at the time of startup and during operation.

  However, when the resonance frequency of the MEMS scanning mirror changes, the interval of pulse signals obtained from the photosensor changes even if the scanning amplitude is the same. As a result, the conventional method has a problem that the accuracy of controlling the scanning amplitude is low.

  SUMMARY An advantage of some aspects of the invention is that it provides a laser scanning device capable of improving the accuracy of scanning amplitude control.

  In order to achieve the above object, a laser scanning device according to an aspect of the present invention includes a laser light source, a scanning mirror that scans laser light from the laser light source, and a drive signal applied to the scanning mirror. A driving unit that drives the scanning mirror, a photosensor that is disposed in a region where the laser light scanned by the scanning mirror scans, and that generates a detection signal when the laser light is detected, and the scanning of the scanning mirror A clock generator that generates a clock signal that is phase-synchronized with the repetition frequency and has a frequency higher than the repetition frequency, a counting unit that counts the generation interval of the detection signal using the clock signal, and the counting unit And a control unit that controls the drive unit so that the count value counted in (2) approaches a predetermined target value.

  According to this configuration, the period of the clock signal changes following the change in the scanning period. Therefore, the laser scanning device can keep the count value counted by the counting unit constant even when the scanning cycle changes due to variations in the resonance frequency of the scanning mirror. Thereby, the laser scanning device can improve the accuracy of controlling the scanning amplitude based on the count value.

  For example, the laser scanning device further includes a signal generation unit that generates a detection pulse signal whose logic value is inverted each time the detection signal is generated, and the clock generation unit is phase-synchronized with the detection pulse signal. In addition, the clock signal having a frequency higher than that of the detection pulse signal may be generated, and the counting unit may count the generation interval by counting a pulse width of the detection pulse signal using the clock signal. .

  According to this configuration, the laser scanning device can easily generate a clock signal that is phase-synchronized with the scanning cycle.

  For example, the signal generation unit may generate the detection pulse signal in which the logic value is inverted every time the detection signal is generated only in an effective period that is a part of one period of the scan. .

  According to this configuration, the laser scanning device can suppress generation of an erroneous detection pulse signal due to noise or the like.

  For example, the clock signal may have a frequency n (n is an integer of 2 or more) times the detection pulse signal.

  According to this configuration, the laser scanning device can easily generate a clock signal that is phase-synchronized with the scanning cycle and has a higher frequency than the scanning cycle.

  For example, the control unit may control the amplitude of the drive signal so that the count value approaches the target value.

  According to this configuration, the laser scanning device can control the scanning amplitude based on the count value.

  The present invention can be realized not only as a laser scanning device including such a characteristic processing unit, but also as a laser scanning method including steps executed by the characteristic processing unit included in the laser scanning device. Can be realized. It can also be realized as a program for causing a computer to function as a characteristic processing unit included in the laser scanning device or a program for causing a computer to execute characteristic steps included in a laser scanning method. Further, it goes without saying that such a program can be distributed via a computer-readable non-transitory recording medium such as a CD-ROM (Compact Disc-Read Only Memory) or a communication network such as the Internet. .

  The present invention can provide a laser scanning device capable of improving the accuracy of scanning amplitude control.

1 is a diagram illustrating a schematic configuration of a laser scanning device according to a first embodiment. It is a figure which shows the mode of the laser beam which passes the photosensor which concerns on Embodiment 1. FIG. 1 is a block diagram of a laser scanning device according to Embodiment 1. FIG. FIG. 3 is a block diagram of a clock generation unit according to the first embodiment. 6 is a diagram illustrating a relationship between a frequency of a drive signal and a scanning amplitude according to Embodiment 1. FIG. 3 is a flowchart showing an operation performed by the laser scanning device according to the first embodiment. 4 is a timing chart of various signals in the laser scanning device according to the first embodiment. It is a figure which shows the relationship between the scanning amplitude and count value which concern on Embodiment 1. FIG. 6 is a diagram illustrating amplitude control of a drive signal by the laser scanning device according to Embodiment 1. FIG. FIG. 10 is a diagram for explaining a problem when a fixed clock is used according to the first embodiment. It is a figure which shows the various signals when the frequency which concerns on Embodiment 1 changes. 6 is a diagram illustrating a photosensor according to Embodiment 2. FIG. 6 is a diagram illustrating a signal obtained from a photosensor according to Embodiment 2. FIG. 6 is a diagram illustrating a detection pulse generation method according to Embodiment 2. FIG. FIG. 5 is a block diagram of a laser scanning device according to a third embodiment. 10 is a block diagram of a clock generation unit according to Embodiment 3. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that each of the embodiments described below shows a comprehensive or specific example. The numerical values, shapes, materials, constituent elements, arrangement positions and connecting forms of the constituent elements, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims are described as arbitrary constituent elements.

(Embodiment 1)
[Configuration of laser scanning device]
FIG. 1 is a diagram showing a schematic configuration of a laser scanning device according to the present embodiment.

  A laser scanning device 100 illustrated in FIG. 1 includes a laser light source 101, a MEMS scanning mirror 102, and a photosensor 103.

  The laser light source 101 emits laser light 121.

  The MEMS scanning mirror 102 is a resonant scanning mirror and reflects the laser beam 121. The MEMS scanning mirror 102 scans the laser beam 121. Further, the laser beam 122 reflected by the MEMS scanning mirror 102 scans the scanning region 123.

  The photosensor 103 is disposed in the scanning region 123 and detects the laser beam 122.

  In addition, as shown in FIG. 2, in one scanning (one cycle) in which the laser beam 122 reciprocates once through the scanning region 123, the laser beam 122 passes twice over the photosensor 103.

  FIG. 3 is a block diagram of the laser scanning apparatus 100 according to the present embodiment. A laser scanning device 100 shown in FIG. 3 includes a laser light source 101, a MEMS scanning mirror 102, a photosensor 103, an oscillator 104, a drive unit 105, a signal generation unit 106, a clock generation unit 107, and a counting unit 108. And a control unit 109.

  The photosensor 103 generates a detection signal 124 when detecting the laser beam 122.

  The oscillator 104 generates a reference signal 125 having a predetermined frequency and supplies the reference signal 125 to the driving unit 105. Further, the oscillator 104 generates a fixed clock 126 having a fixed frequency and supplies the fixed clock 126 to the counting unit 108.

  The drive unit 105 drives the MEMS scanning mirror 102 by applying a drive signal 127 to the MEMS scanning mirror 102. Specifically, the drive unit 105 generates a drive signal 127 having the same frequency as the reference signal 125 using the reference signal 125 supplied from the oscillator 104. The drive unit 105 applies a drive signal 127 to the MEMS scanning mirror 102 to cause the MEMS scanning mirror 102 to scan and deflect the laser light 122.

  In addition, the drive unit 105 generates a binarized drive signal 128 obtained by binarizing the drive signal 127 and supplies the binarized drive signal 128 to the signal generation unit 106. Note that the drive unit 105 may supply the drive signal 127 to the signal generation unit 106, and the signal generation unit 106 may generate the binarized drive signal 128.

  The signal generation unit 106 uses the detection signal 124 to generate a detection pulse 129 (detection pulse signal) indicating an interval at which the detection signal 124 is generated. Specifically, the detection pulse 129 is a signal whose logic value is inverted every time the detection signal 124 is generated. For example, the detection pulse 129 is a signal that is at a high level in a period from the generation of the first detection signal 124 to the generation of the second detection signal 124 in each cycle.

  The clock generation unit 107 generates a count clock 130 (clock signal) that is phase-synchronized with the repetition frequency of scanning by the MEMS scanning mirror 102 and that has a higher frequency than the repetition frequency. That is, the count clock 130 is a signal whose period (frequency) changes following the change in the scanning period of the MEMS scanning mirror 102. Specifically, the clock generation unit 107 generates a count clock 130 that is phase-synchronized with the detection pulse 129 and has a higher frequency than the detection pulse 129. For example, the count clock 130 has a frequency that is n (n is an integer of 2 or more) times the detection pulse 129.

  The counting unit 108 counts the generation interval of the detection signal 124 using the counting clock 130 and notifies the control unit 109 of the obtained count value 131. Specifically, the counting unit 108 counts the generation interval of the detection signal 124 by counting the pulse width of the detection pulse 129 using the counting clock 130.

  The control unit 109 controls the drive unit 105 so that the count value 131 approaches a predetermined target value. Specifically, the control unit 109 controls the amplitude of the drive signal 127 so that the count value 131 approaches the target value.

  FIG. 4 is a block diagram of the clock generation unit 107. As shown in FIG. 4, the clock generation unit 107 includes a PLL (Phase Locked Loop) circuit 111 and a frequency divider 112. The PLL circuit 111 includes a phase comparator 113, a charge pump 114, a loop filter 115, and a voltage controlled oscillator 116.

  The PLL circuit 111 performs a PLL operation. The frequency divider 112 is a 1 / n frequency divider. Here, n is about 100, for example. Since the PLL operation is a general technique, a detailed description of each processing unit is omitted. However, the circuit configuration shown in FIG. 4 is used to synchronize the phase with the detection pulse 129 and to 1 / of the cycle of the detection pulse 129. A counting clock 130 having a period of n is generated. In other words, the frequency of the count clock 130 is n times the frequency of the detection pulse 129.

[Characteristics of MEMS scanning mirror]
The MEMS scanning mirror 102 is a resonant scanning mirror that uses resonance to increase scanning amplitude. Such a resonant scanning mirror has a high Q value. FIG. 5 is a diagram showing the characteristics of the scanning amplitude with respect to the frequency of the drive signal 127 of the MEMS scanning mirror 102. As shown in FIG. 5, when the frequency of the drive signal 127 is in the vicinity of the resonance frequency (natural frequency) of the MEMS structure, the amplitude rapidly increases. On the other hand, when the frequency of the drive signal 127 deviates from the resonance frequency, the scanning amplitude decreases rapidly. Due to such characteristics, it is necessary to adjust the frequency of the drive signal 127 with high accuracy.

  This resonance frequency changes as shown by M1 to M3 in FIG. 5 due to manufacturing variations and environmental changes such as temperature changes and atmospheric pressure changes. In particular, there is a large variation in resonance frequency due to manufacturing variations. Depending on the manufacturing process, the resonance frequency may vary by about 15%.

[Operation of laser scanning device]
FIG. 6 is a flowchart of the scanning amplitude adjustment operation by the laser scanning device 100 according to the present embodiment.

  First, the laser scanning device 100 adjusts the frequency of the drive signal 127 as an initial adjustment at the time of activation (S101). Specifically, the oscillator 104 generates a fixed clock 126 and supplies it to the counting unit 108. Under the control of the control unit 109, the drive unit 105 sweeps the frequency of the drive signal 127. The counting unit 108 counts the pulse width of the detection pulse 129 at each frequency of the drive signal 127 using the fixed clock 126 (S111). Here, the counted pulse width corresponds to the generation interval of the detection signal 124.

  Next, the control unit 109 sets the frequency of the drive signal 127 based on the counting result so that the pulse width is maximized (S112).

  By the above processing, an appropriate frequency of the drive signal 127 is set in consideration of the variation of the resonance frequency based on the manufacturing variation or the like.

  On the other hand, even during operation, the resonance frequency of the MEMS scanning mirror 102 varies due to a temperature change or the like. In order to compensate for this variation, the laser scanning device 100 controls the amplitude of the drive signal 127 during operation (S102). Thereby, even when the resonance frequency fluctuates during operation, the scanning amplitude can be made constant.

  Specifically, first, the count clock 130 is generated by turning on the clock generation unit 107 (S121).

  The counting unit 108 counts the pulse width of the detection pulse 129 using the counting clock 130 (S122). Based on the obtained count value, the control unit 109 adjusts the amplitude of the drive signal 127 so that the count value approaches the target value (S123).

  Further, the processes in steps S122 and S123 are repeatedly performed at predetermined time intervals during the operation.

  FIG. 7 is a timing chart of various signals according to the present embodiment. In FIG. 7, the period T0 (deflection scanning period) of the drive signal 127 and the amplitude A0 of the drive signal 127 are constant. Further, the scanning amplitude is changed from B1 to B3 due to the environmental change.

  The signal generation unit 106 binarizes the detection signal 124 from the photosensor 103 to generate a binarization detection signal. Here, as shown in FIG. 2, since the laser beam 122 crosses the photosensor 103 twice in the forward path and the backward path in one cycle of the MEMS scanning mirror, two detection signals 124 are generated.

  As shown in FIG. 7, when the scanning amplitude of the MEMS scanning mirror 102 is small, the interval between the two detection signals 124 is short, and when the scanning amplitude is large, the interval between the two detection signals 124 is long. That is, information on scanning amplitude can be obtained from this interval.

  In addition, the signal generation unit 106 generates a detection pulse 129 that is set at the rising edge of the first pulse of the binarization detection signal and reset at the rising edge of the second pulse. In other words, the detection pulse 129 is a signal whose logic value is inverted every time the detection signal 124 is generated.

  In addition, the signal generation unit 106 inverts the logical value of the detection pulse 129 according to the binarization detection signal only during the valid period in which the binarization drive signal 128 is at a high level, and the binarization drive signal 128 is low. In the invalid period which is the level, the low level detection pulse 129 is generated. Thereby, it can suppress that the erroneous detection pulse 129 resulting from noise etc. is produced | generated. Note that here, the effective period is a period in which the binarization drive signal 128 is at a high level. This is because the laser beam 122 passes through the photosensor 103 in a period in which the binarization drive signal 128 is at a high level. It is. In other words, the effective period may be a part of one scanning period of the MEMS scanning mirror 102 and a period during which the laser beam 122 passes through the photosensor 103. In other words, the valid period is set according to the position of the photosensor 103.

  The counting unit 108 counts the pulse width of the detection pulse 129, that is, the generation interval of the detection signal 124 with the count clock 130. Specifically, the counting unit 108 obtains a count value by counting the number of clocks of the counting clock 130 from when the detection pulse 129 becomes high level to when it becomes low level.

  Further, as shown in FIG. 7, as the scanning amplitude increases to B1, B2, and B3, the pulse width of the detection pulse 129 increases to W1, W2, and W3. Also, the count value 131 increases as the pulse width increases.

  The control unit 109 controls the amplitude of the drive signal 127 so that the obtained count value 131 becomes equal to the target value.

  FIG. 8 is a diagram illustrating the relationship between the scanning amplitude of the MEMS scanning mirror 102 and the count value 131. When the photosensor 103 is arranged at the end of the scanning region 123 as shown in FIG. 1, the count value 131 cannot be obtained when the scanning amplitude is small and the laser beam 122 does not cross the photosensor 103, but the laser beam 122 When the photo sensor 103 is crossed, the count value 131 is normally obtained.

  FIG. 9 is a diagram illustrating an example of an amplitude adjustment process of the drive signal 127 during operation. As shown in FIG. 9, when the amplitude of the drive signal 127 is A1 and the scanning amplitude is B1, the pulse width W1 of the detection pulse 129 is narrower than the target value. In this case, the control unit 109 increases the amplitude of the drive signal 127 from A1 to A2. As a result, the scanning amplitude increases from B1 to B2, and the generation interval of the detection signal 124 increases. Thereby, the pulse width W2 of the detection pulse 129 increases, and the pulse width approaches the target value. That is, the obtained count value 131 approaches the target value.

  As described above, the laser scanning device 100 can control the scanning amplitude to be constant by adjusting the amplitude of the drive signal 127 in accordance with a change in the operating environment.

[effect]
In the present embodiment, as described above, the count clock 130 that is phase-synchronized with the detection pulse 129 is used to measure the pulse width W2 of the detection pulse 129. As a result, the accuracy of scanning amplitude control can be improved. Hereinafter, this effect will be described.

  FIG. 10 is a diagram for comparison, and shows an operation when a fixed clock having a constant frequency is used instead of the counting clock 130.

  As described above, the frequency of the drive signal 127 is adjusted in order to correct variations in the resonance frequency of the MEMS scanning mirror 102. As shown in FIG. 10, when the frequency of the drive signal 127 is different, the pulse width of the detection pulse 129 changes even if the scanning amplitude B0 is the same.

  For example, as shown in FIG. 10, when the resonance frequency is high (period is T1), the pulse width W1 corresponding to the interval between the two detection signals 124 is narrowed, so the count value 131 is small. On the other hand, when the resonance frequency is low (period is T2 (> T1)), the pulse width W2 is widened, and thus the count value 131 is large. That is, the count value 131 changes due to variations in the resonance frequency of the MEMS scanning mirror 102 even though the scanning amplitude is the same. Thus, accurate amplitude control cannot be performed.

  FIG. 11 is a diagram according to the present embodiment, and is a diagram illustrating an operation when the count clock 130 that is phase-synchronized with the detection pulse 129 is used.

  As shown in FIG. 11, in the present embodiment, the count clock 130 is phase-synchronized with the detection pulse 129. Here, the frequency of the detection pulse 129 is equal to the frequency of the drive signal 127. That is, the frequency of the detection pulse 129 is substantially equal to the resonance frequency of the MEMS scanning mirror 102. Therefore, the count clock 130 has a frequency proportional to the resonance frequency. In other words, the frequency of the counting clock 130 increases as the resonance frequency increases and decreases as the resonance frequency decreases. That is, the frequency of the counting clock 130 changes following the resonance frequency.

  Thereby, as shown in FIG. 11, even when the resonance frequency is changed, the same count value 131 is obtained if the scanning amplitude is the same.

  As described above, the laser scanning apparatus 100 according to the present embodiment can realize stable detection of scanning amplitude because the count value 131 does not change even if the frequency of the drive signal 127 changes due to environmental changes or the like. Thereby, the laser scanning device 100 can realize highly accurate control of the scanning amplitude.

[Modification]
In the above description, the example in which the count clock 130 is generated from the detection pulse 129 has been described. However, the count clock 130 is phase-synchronized with the scanning period (frequency) of the MEMS scanning mirror 102 or the period of the drive signal 127 ( Any signal that is phase-synchronized with (frequency) may be used. In other words, the counting clock 130 may be a signal whose period (frequency) changes following the change of the scanning period (frequency) of the MEMS scanning mirror 102 or the period (frequency) of the drive signal 127.

  For example, the clock generation unit 107 may generate the count clock 130 by using the binarization drive signal 128 instead of the detection pulse 129 and dividing the binarization drive signal 128 by n. Even in this case, the same effect as described above can be realized.

  In the above description, only the frequency of the drive signal 127 is adjusted during initial adjustment and only the amplitude of the drive signal 127 is adjusted during operation. However, the frequency and amplitude may be adjusted during initial adjustment. Similarly, frequency and amplitude may be adjusted during operation.

(Embodiment 2)
In this embodiment, a method for improving detection accuracy of timing at which the laser beam 122 passes through the photosensor 103 will be described.

  FIG. 12 is a diagram illustrating a configuration of the photosensor 103 according to the present embodiment. As shown in FIG. 12, in this embodiment, the photosensor 103 includes two photosensors 103A and 103B.

  FIG. 13 is a diagram illustrating signals obtained by the two photosensors 103A and 103B. The signals SA and SB obtained from the two photosensors 103A and 103B, the difference value SB-SA between the signal SA and the signal SB, the addition value SA + SB between the signal SA and the signal SB, and the difference value SB-SA are zero-crossed. A quantified signal S3, a signal S4 obtained by binarizing the added value SA + SB, and a logical product S5 of the signal S3 and the signal S4 are obtained as shown in FIG.

  FIG. 14 is a diagram for explaining a generation method of the detection pulse 129 by the signal generation unit 106 according to the present embodiment. As illustrated in FIG. 14, the signal generation unit 106 calculates a difference value SB−SA between the signal SA and the signal SB and an addition value SA + SB between the signal SA and the signal SB. Next, the signal generation unit 106 calculates a signal S3 obtained by binarizing the difference value SB−SA and a signal S4 obtained by binarizing SA + SB. Next, the signal generation unit 106 calculates a logical product S5 of the signal S3 and the signal S4 and a logical product S6 of the inverted value of the signal S3 and the signal S4. Then, the signal generator 106 generates a detection pulse 129 that is set at the rise of the logical product S5 and reset at the rise of the logical product S6.

  Thereby, as shown in FIG. 14, the rising and falling timings of the detection pulse 129 coincide with the centers of the two signals SA and SB of the added value SA + SB. That is, the rising and falling timings of the detection pulse 129 coincide with the timing when the laser beam 122 passes through the center of the photosensor 103. Thereby, the laser scanning apparatus 100 according to the present embodiment can improve the detection accuracy of the timing when the laser beam 122 passes through the photosensor 103, and thus can improve the adjustment accuracy of the scanning amplitude.

(Embodiment 3)
In the present embodiment, a modification of the first embodiment will be described. In the first embodiment, the example has been described in which the driving unit 105 supplies the driving signal 127 having the frequency set in the initial setting to the MEMS scanning mirror 102 during operation. In the present embodiment, the laser scanning device adjusts the frequency of the drive signal 127 during operation using self-excited oscillation.

  FIG. 15 is a block diagram of laser scanning apparatus 100A according to the present embodiment. Laser scanning apparatus 100A shown in FIG. 15 further includes a switch 110 in addition to the configuration of laser scanning apparatus 100 according to the first embodiment. Further, the configuration of the clock generation unit 107A is different.

  FIG. 16 is a diagram illustrating a configuration of the clock generation unit 107A according to the present embodiment. The clock generation unit 107A is different from the clock generation unit 107 in that the synchronization signal 132 is output to the switch 110.

  Here, the synchronization signal 132 is a signal that is phase-synchronized with the detection pulse 129 and has the same frequency as the detection pulse 129.

  The switch 110 supplies the reference signal 125 generated by the oscillator 104 to the drive unit 105 at the time of initial setting. Note that the operation at the time of initial setting is the same as that of the first embodiment.

  In addition, the switch 110 supplies the synchronization signal 132 to the drive unit 105 during the operation after the initial setting. As a result, the drive unit 105 generates a drive signal 127 having the same frequency as the synchronization signal 132.

  With the above configuration, in addition to the adjustment of the amplitude of the drive signal 127 described above, the frequency of the drive signal 127 is adjusted by the self-excited oscillation operation so that the fluctuation of the scanning amplitude accompanying the fluctuation of the resonance frequency during operation is suppressed. Is done. Thereby, the laser scanning device 100A can adjust the scanning amplitude with higher accuracy.

  The laser scanning device according to the embodiment of the present invention has been described above, but the present invention is not limited to this embodiment.

  For example, the division of functional blocks in the block diagram is an example, and a plurality of functional blocks can be realized as one functional block, a single functional block can be divided into a plurality of functions, or some functions can be transferred to other functional blocks. May be. In addition, functions of a plurality of functional blocks having similar functions may be processed in parallel or time-division by a single hardware or software.

  In addition, the logic level represented by high / low or the switching state represented by on / off is exemplified to specifically describe the present invention, and different combinations of the illustrated logic level or switching state. Therefore, it is possible to obtain an equivalent result.

  Further, each of the above devices may be specifically configured as a computer system including a microprocessor, ROM, RAM, hard disk drive, display unit, keyboard, mouse, and the like. A computer program is stored in the RAM or hard disk drive. Each device achieves its functions by the microprocessor operating according to the computer program. Here, the computer program is configured by combining a plurality of instruction codes indicating instructions for the computer in order to achieve a predetermined function.

  Furthermore, some or all of the constituent elements constituting each of the above-described devices may be configured by one system LSI (Large Scale Integration). The system LSI is a super multifunctional LSI manufactured by integrating a plurality of components on one chip, and includes, for example, a computer system including a microprocessor, ROM, RAM, and the like. In this case, a computer program is stored in the ROM. The system LSI achieves its functions by the microprocessor operating according to the computer program.

  Furthermore, some or all of the constituent elements constituting each of the above-described devices may be configured from an IC card that can be attached to and detached from each device or a single module. The IC card or module is a computer system that includes a microprocessor, ROM, RAM, and the like. The IC card or the module may include the super multifunctional LSI described above. The IC card or the module achieves its function by the microprocessor operating according to the computer program. This IC card or this module may have tamper resistance.

  Further, the present invention may be the method described above. Further, the present invention may be a computer program that realizes these methods by a computer, or may be a digital signal composed of the above computer program.

  Furthermore, the present invention provides a non-transitory recording medium that can read the computer program or the digital signal, for example, a flexible disk, a hard disk, a CD-ROM, an MO, a DVD, a DVD-ROM, a DVD-RAM, a BD ( It may be recorded on a Blu-ray (registered trademark) Disc), a semiconductor memory, or the like. The digital signal may be recorded on these non-temporary recording media.

  In the present invention, the computer program or the digital signal may be transmitted via an electric communication line, a wireless or wired communication line, a network represented by the Internet, a data broadcast, or the like.

  The present invention may be a computer system including a microprocessor and a memory, wherein the memory stores the computer program, and the microprocessor operates according to the computer program.

  Further, by recording the program or the digital signal on the non-temporary recording medium and transferring it, or transferring the program or the digital signal via the network or the like, another independent computer It may be implemented by the system.

  Furthermore, the above embodiment and the above modification examples may be combined.

  The present invention can be applied to a laser scanning device, for example, a laser range finder for measuring a distance from the laser scanning device to an object.

DESCRIPTION OF SYMBOLS 100,100A Laser scanning device 101 Laser light source 102 MEMS scanning mirror 103, 103A, 103B Photo sensor 104 Oscillator 105 Drive part 106 Signal generation part 107, 107A Clock generation part 108 Count part 109 Control part 110 Switch 111 PLL circuit 112 Frequency divider 113 Phase Comparator 114 Charge Pump 115 Loop Filter 116 Voltage Controlled Oscillator 121, 122 Laser Light 123 Scanning Area 124 Detection Signal 125 Reference Signal 126 Fixed Clock 127 Drive Signal 128 Binary Drive Signal 129 Detection Pulse 130 Count Clock 131 Count Value 132 Sync signal

Claims (5)

A laser light source;
A scanning mirror that scans laser light from the laser light source;
A driving unit that drives the scanning mirror by applying a driving signal to the scanning mirror;
A photo sensor that is arranged in a region to be scanned by the laser beam scanned by the scanning mirror and generates a detection signal when the laser beam is detected;
A clock generation unit that generates a clock signal that is phase-synchronized with the repetition frequency of the scanning of the scanning mirror and that is higher in frequency than the repetition frequency;
A counting unit that counts the generation interval of the detection signal using the clock signal;
A laser scanning device comprising: a control unit that controls the drive unit so that the count value counted by the counting unit approaches a predetermined target value. The laser scanning device further includes:
A signal generation unit that generates a detection pulse signal whose logic value is inverted each time the detection signal is generated;
The clock generation unit is phase-synchronized with the detection pulse signal and generates the clock signal having a frequency higher than that of the detection pulse signal,
The laser scanning device according to claim 1, wherein the counting unit counts the generation interval by counting a pulse width of the detection pulse signal using the clock signal. The said signal generation part produces | generates the said detection pulse signal that the said logic value inverts whenever the said detection signal is produced | generated only in the effective period which is a part of one period of the said scanning. Laser scanning device. The laser scanning device according to claim 2, wherein the clock signal has a frequency that is n (n is an integer of 2 or more) times the detection pulse signal. The laser scanning device according to any one of claims 1 to 4, wherein the control unit controls the amplitude of the drive signal so that the count value approaches the target value.

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