Optical scanning apparatus

Abstract

To provide a technique capable of detecting the necessity of correction of driving voltage of an optical deflector by a simple apparatus configuration without reducing a scanning range.SOLUTION: An optical scanning apparatus comprises: an optical polarizer having a sensor that detects a deflection angle of a mirror; a control device; a memory; and a driving circuit that supplies the driving voltage to the optical polarizer. The control device includes: a driving signal generation section that generates a driving signal containing set values of a drive frequency and a voltage level of the driving voltage; a feature value calculation section that obtains a phase difference between the driving signal and a sensor signal output from the sensor, acquires the drive frequency of the driving voltage, and calculates a feature value which is a value indicating a frequency characteristic of the phase difference of the sensor signal on the basis of the phase difference and the drive frequency; and a detection section that detects a change in the deflection angle by referring to data stored in the memory using the feature value. The data stored in the memory contains information representing a correspondence relation between the deflection angle and the feature value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to optical scanning devices. [Background technology]

[0002] Japanese Patent No. 6990573 (Patent Document 1) describes an optical scanning device that detects light scanned by an optical deflector using an optical sensor and has the function of calibrating the drive voltage based on the time when this detection occurred and the frequency and intensity of the drive signal used to drive the optical deflector.

[0003] The above-described optical scanning device requires a beam splitter or the like to be placed within the scanning range to guide the light scanned by the optical deflector to the optical sensor, which reduces the available scanning range and leaves room for improvement.Furthermore, the device configuration becomes larger due to the need for an optical sensor and a circuit for performing signal processing such as amplification on the output of the optical sensor, which leaves room for improvement. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6990573 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of a specific aspect of the present disclosure is to provide a technique capable of detecting whether or not correction of the drive voltage of an optical deflector is required using a simple device configuration without reducing the scanning range. [Means for solving the problem]

[0006] An optical scanning device according to one aspect of the present disclosure includes: an optical deflector having a mirror that operates by resonance and a sensor that detects the deflection angle of the mirror; a control device for controlling the operation of the optical deflector; a memory connected to the controller; a drive circuit for supplying a drive voltage to the optical deflector under the control of the control device; Including, The control device a drive signal generating unit that generates a drive signal including set values ​​for the drive frequency and voltage level of the drive voltage; a feature value calculation unit that calculates a phase difference between the sensor signal output from the sensor and the drive signal, acquires the drive frequency of the drive voltage from the drive signal generation unit, and calculates a feature value that is a value indicating a frequency characteristic of the phase difference of the sensor signal based on the phase difference and the drive frequency; a detection unit that detects a change in the deflection angle by referring to the data stored in the memory using the feature value calculated by the feature value calculation unit; It has the data stored in the memory includes information representing a correspondence relationship between the deflection angle and the feature value; It is an optical scanning device.

[0007] According to the above configuration, a technique is provided that can detect whether or not the drive voltage of the optical deflector needs to be corrected using a simple device configuration without reducing the scanning range. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing the configuration of an optical scanning device according to an embodiment. [Figure 2] FIG. 2 is a diagram for explaining the phase difference. [Figure 3] FIG. 3 is a diagram showing the characteristics of the phase difference centered on the resonance frequency ω0. [Figure 4] FIG. 4 is a diagram illustrating the relationship between the drive frequency and the phase difference of the sensor signal. [Figure 5] FIG. 5 is a diagram illustrating the relationship between the drive frequency and the phase difference of the sensor signal, which varies depending on the magnitude of the deflection angle. [Figure 6]Fig. 6(A) is a diagram showing an example of the relationship between the drive frequency and the amplitude of the sensor signal before and after the change due to aging of the optical deflector. Fig. 6(B) is a diagram in which the horizontal axis represents the frequency when the frequency at resonance before and after the change in the graph shown in Fig. 6(A) is set to 0, and the vertical axis represents the phase difference of the sensor signal at resonance before and after the change. [Figure 7] FIG. 7 is a flowchart showing the operation procedure of the control device when determining a characteristic amount (for example, a Q value) and detecting a deflection angle based on the characteristic amount. [Figure 8] FIG. 8 is a flowchart showing the operation procedure of the control device when determining a characteristic amount (for example, a Q value) and detecting a deflection angle based on the characteristic amount. [Figure 9] FIG. 9 is a flowchart showing the operation procedure of the control device when determining a characteristic amount (for example, a Q value) and detecting a deflection angle based on the characteristic amount. [Figure 10] FIG. 10 is a diagram for explaining the correspondence relationship between the tilt B and the deflection angle. [Figure 11] FIG. 11 is a diagram illustrating an example of the feature value. DETAILED DESCRIPTION OF THE INVENTION

[0009] Fig. 1 is a block diagram showing the configuration of an optical scanning device according to one embodiment. The optical scanning device is capable of scanning light incident from a light source or the like (not shown) in at least one direction, and includes a control device 1, a memory 2, a drive circuit 3, an optical deflector 4, and a sensor signal processing circuit 5. As shown in Fig. 3 of Patent Document 1, scanning in one direction involves twisting a torsion bar to rotate a mirror, thereby performing one-dimensional scanning. In the case of an optical scanning device that scans in two directions, scanning in two directions involves moving bellows-shaped actuators on both sides of a mirror to rotate another mirror in a direction perpendicular to the mirror, thereby performing two-dimensional scanning.

[0010] The control device 1 controls the overall operation of the optical scanning device, such as controlling the operation of the optical deflector 4, and is connected to a memory 2, a drive circuit 3, and a sensor signal processing circuit 5. The control device 1 is configured, for example, by having a computer equipped with a processor, RAM, etc. execute a predetermined operation program on the processor. In the following, to facilitate understanding of the functions of the control device 1, the following description will be given using the functional blocks of a drive signal generation unit 10, a feature value calculation unit 11, and a detection unit 12.

[0011] The drive signal generation unit 10 generates a drive signal (control signal) required to drive the optical deflector 4. Specifically, the drive signal generation unit 10 generates a drive signal including setting values ​​such as the drive frequency and voltage level of the drive voltage generated by the drive circuit 3. The generated drive signal is supplied to the drive circuit 3.

[0012] The feature value calculation unit 11 acquires the sensor signal input from the sensor signal processing circuit 5 and calculates the phase difference between the sensor signal and the drive signal. The feature value calculation unit 11 also acquires the drive frequency of the drive signal from the drive signal generation unit 10 and detects a feature value, which is information indicating the frequency characteristics of the phase difference of the sensor signal, based on the drive frequency and the phase difference. The feature value will be described in detail later.

[0013] The detection unit 12 detects the rate of change of the deflection angle based on the feature value calculated by the feature value calculation unit 11 and data stored in advance in the memory 2 and including information relating the feature value to the deflection angle.

[0014] The memory 2 is configured using, for example, a nonvolatile memory, and is used to store data necessary for information processing in the control device 1. The memory 2 pre-stores data including information relating the above-mentioned characteristic values ​​to the rate of change of the deflection angle.

[0015] The drive circuit 3 generates a drive voltage for operating the optical deflector 4 based on a drive signal supplied from the drive signal generating unit 10 of the control device 1, and supplies the drive voltage to the optical deflector 4.

[0016] The optical deflector 4 includes a mirror 6 that is configured to be able to swing in at least one direction, and by swinging this mirror 6, light incident on the mirror 6 from a light source (not shown) is reflected and scanned. The optical deflector 4 includes a sensor 7 that detects the deflection angle of the mirror 6.

[0017] The sensor signal processing circuit 5 performs signal processing such as amplification and noise removal on the signal (analog signal) detected by the sensor 7 of the optical deflector 4, and also converts the signal into a digital signal. The obtained digital signal is input to the control device 1 as a sensor signal.

[0018] FIG. 2 is a diagram for explaining the phase difference. The optical deflector 4 oscillates due to a drive voltage generated by the drive circuit 3 based on a drive signal. However, a phase difference exists between the time when the drive signal is input to the drive circuit 3, the time when the corresponding drive voltage is input to the optical deflector 4, and the time when the mirror 6 of the optical deflector 4 actually oscillates. Therefore, as shown in FIG. 2, a phase difference occurs between the drive signal and the sensor signal output from the sensor 7 of the optical deflector 4. Furthermore, when considering a resonating object, the phase difference rotates by 180 degrees around the resonant frequency ω0 (see FIG. 3). For example, if the frequency is sufficiently lower than the resonant frequency, the phase difference is 0, but if the frequency is sufficiently higher than the resonant frequency, the phase difference is 180 degrees. Therefore, in the present disclosure, the phase difference characteristic with respect to such frequency (hereinafter referred to as the "phase-frequency characteristic") is utilized to detect changes in the deflection angle of the optical deflector 4.

[0019] FIG. 4 illustrates the relationship between the drive frequency and the phase difference of the sensor signal. Here, the horizontal axis represents the difference between the drive frequency and the resonant frequency. A difference of 0 indicates that the drive frequency is equal to the resonant frequency ω0. Here, two drive frequencies near the resonant frequency are designated ω1 and ω2. Both are expressed in terms of angular frequencies. Also, the phase differences of the sensor signals at the drive frequencies ω1 and ω2 are designated δ1 and δ2, respectively. The values ​​of the frequencies ω1 and ω2 are output from the drive signal generator 10 to the feature value detector 11. The phase difference of the sensor signals is calculated in the feature value detector 12 based on the sensor signals output from the sensor signal processing circuit 5. Here, the slope B can be calculated based on the difference between δ1 and δ2 for the change from ω1 to ω2, and this slope B can be used as the feature value. This calculation is performed in the feature value detector 12.

[0020] FIG. 5 illustrates the relationship between the drive frequency and the phase difference of the sensor signal, as a function of the magnitude of the deflection angle. As illustrated, the graph shape changes as the deflection angle of the optical deflector 4 changes. In other words, the rate of change of the deflection angle can be detected based on the graph shape. Therefore, if information such as a data table or a relational expression showing the correspondence between a feature value (e.g., tilt B) reflecting the graph shape and the rate of change of the deflection angle is calculated in advance and stored in memory 2, the rate of change of the deflection angle can be obtained from the feature value by using the data table or the like. Specifically, as described above with reference to FIG. 4, the feature value (e.g., tilt B) is calculated using the sensor signal, and the rate of change of the deflection angle corresponding to the feature value can be obtained by referencing the data in memory 2 using this feature value. Furthermore, the deflection angle itself can be obtained by multiplying the rate of change by the initial value of the deflection angle.

[0021] The change in the graph shape is thought to be due to changes in mechanical characteristics depending on the magnitude of the deflection angle of the optical deflector 4. In other words, in principle, the change in the graph shape does not depend on changes in the degree of change in the deflection angle relative to the voltage level of the drive voltage on the optical deflector 4 side, so the rate of change in the deflection angle can be detected by ignoring such changes on the optical deflector 4 side.

[0022] The correspondence relationship between the tilt B and the rate of change of the deflection angle may be stored in memory 2, for example, as a data table. In this case, the rate of change of the deflection angle corresponding to the tilt B can be obtained by reading out the data table in memory 2. The relationship between the tilt B and the rate of change of the deflection angle may also be stored in memory 2 in the form of a relational expression (function) such as an approximation. In this case, the rate of change of the deflection angle can be calculated by substituting the tilt B into the relational expression. The data table or the relational expression may be written in memory 2, for example, when the optical scanning device is manufactured. The data in memory 2 may also be updated when regular or irregular adjustments are made.

[0023] Note that instead of storing the correspondence relationship between the tilt B and the rate of change of the deflection angle in memory 2, for example, a predetermined threshold value for the tilt B may be stored in memory 2, and when the tilt B exceeds this threshold value or falls outside a certain range, such a case may be detected and an error may be notified. Also, although the tilt B is given as an example of a characteristic value, other characteristic values ​​may also be used. Other characteristic values ​​will be described later.

[0024] FIG. 6(A) shows an example of the relationship between the drive frequency and the amplitude of the sensor signal before and after changes due to aging of the optical deflector. The degree of change in the deflection angle relative to the voltage level of the drive voltage changes in the optical deflector 4 due to aging and other factors. The degree of change in the sensor signal relative to the degree of change in the deflection angle also changes. FIG. 6(A) shows the frequency characteristics when the deflection angle at resonance is adjusted to be the same before and after the change. The horizontal axis shows the frequency difference when the resonant frequency before the change is set to 0. The vertical axis shows the amplitude when the amplitude of the sensor signal at resonance before the change is set to 100%. As shown in FIG. 6(A), it can be seen that changes occur in the resonant frequency and the amplitude of the sensor signal before and after the change.

[0025] Figure 6(B) is a graph in which the horizontal axis represents the frequency when the frequency at resonance before and after the change in the graph shown in Figure 6(A) is set to 0, and the vertical axis represents the phase difference of the sensor signal at resonance before and after the change. As shown in Figure 6(B), it can be seen that the shape of the graph before and after the change, that is, the slope before and after the change, remains unchanged. In other words, even if there is a change in the degree of change in the deflection angle relative to the voltage level of the drive voltage or the degree of change in the sensor signal relative to the deflection angle, the feature value, which is information indicating the phase-frequency characteristics, remains almost unchanged before and after the change. Therefore, it can be seen that the deflection angle can be identified by using the feature value (slope B, as an example).

[0026] In general, the characteristics of displacement when an object is displaced (deformed) change depending on its mechanical characteristics (such as weight, hardness, size, shape, etc.) In particular, it is known that a resonating object has a characteristic in which the delay characteristics of the applied force, expressed as a phase difference, change by 180 degrees around the resonance frequency (see Figure 3), and it is thought that the characteristics of the phase difference with respect to frequency change depending on the mechanical characteristics (such as weight, hardness, size, shape, etc.).

[0027] Let's apply this to an optical deflector. The mechanical characteristics of an optical deflector are not always constant, and its hardness and other properties change depending on the magnitude of the deflection angle. In other words, when comparing when the deflection angle at resonance is large and when it is small, the phase difference characteristics with respect to frequency are different.

[0028] On the other hand, since the sensor installed in the optical deflector generates a voltage according to the magnitude of the deflection angle, it can be said that the efficiency of the conversion from the deflection angle to voltage at the sensor is not affected by the mechanical characteristics of the optical deflector. In other words, when a feature indicating the phase frequency characteristics is obtained from the phase difference of the sensor signal and used to detect the deflection angle, changes in the conversion efficiency can be ignored.

[0029] 7, 8, and 9 are flowcharts showing the operation procedure of the control device 1 when determining a feature amount (for example, tilt B) and detecting the deflection angle based on the feature amount. Note that the order of the processes shown here can be changed as long as no contradiction or inconsistency occurs in the results of the information processing, and other processes not explicitly shown here can also be added.

[0030] In the operation procedure of the first mode shown in Figure 7, a drive signal is generated by the drive signal generation unit 10 and supplied to the drive circuit 3, and when the optical deflector 4 is driven by the drive circuit 3, the feature value calculation unit 11 acquires the drive frequency of the drive signal from the drive signal generation unit 10 and calculates the phase difference of the sensor signal corresponding to that drive frequency based on the sensor signal acquired from the sensor signal processing circuit 5, and stores these drive frequencies and phase differences in memory 2 (step S11).

[0031] Next, the feature value calculation unit 11 instructs the drive signal generation unit 10 to change the drive frequency of the drive signal until the phase difference of the sensor signal changes by a certain amount (step S12). As an example, the drive frequency of the drive signal is changed until the phase difference of the sensor signal changes by about 50 degrees. The feature value calculation unit 11 stores the drive frequency of the drive signal after being changed in step S12 and the corresponding phase difference of the sensor signal in the memory 2 (step S13).

[0032] The feature value calculation unit 11 calculates the slope B, which is a feature value of the phase-frequency characteristics of the sensor signal, based on the drive frequency and phase difference stored in the memory 2. The detection unit 12 detects the rate of change of the deflection angle using a data table or the like pre-stored in the memory 2 based on the calculated feature value (slope B) (step S14). For example, if the rate of change of the deflection angle with respect to the calculated slope B is 80%, it can be detected that the deflection angle has decreased to a value 80% of its initial value. This completes the detection of the rate of change of the deflection angle.

[0033] Instead of detecting the rate of change of the deflection angle, it is also possible to detect whether the deflection angle has changed by a certain amount or more by comparing it with a threshold value related to the tilt B. For example, when the deflection angle falls below a certain threshold, it is possible to detect this, i.e., that a change has occurred in the deflection angle. Similarly, it is also possible to set upper and lower threshold values ​​related to the tilt B, and detect whether the tilt B is within the range between the upper and lower threshold values. The same applies to the operation procedures of the second and third aspects described below.

[0034] In the second mode of operation procedure shown in FIG. 8, a drive signal is generated by the drive signal generating unit 10 and supplied to the drive circuit 3, and when the optical deflector 4 is driven by the drive circuit 3, the feature value calculating unit 11 instructs the drive signal generating unit 10 to sweep the drive frequency of the drive signal within a specific range (step S21).

[0035] The feature value calculation unit 11 acquires at least two drive frequencies within the sweep range of the drive frequency of the drive signal from the drive signal generation unit 10, and calculates the phase differences of the sensor signals corresponding to those drive frequencies based on the sensor signals acquired from the sensor signal processing circuit 5, and stores these drive frequencies and phase differences in memory 2 (step S22).

[0036] The feature value calculation unit 11 calculates the slope B, which is a feature value of the phase-frequency characteristics of the sensor signal, based on the drive frequency and phase difference stored in the memory 2. The detection unit 12 detects the rate of change of the deflection angle based on the calculated feature value (slope B) using a data table or the like pre-stored in the memory 2 (step S23). This completes the detection of the rate of change of the deflection angle.

[0037] In the operation procedure of the third mode shown in Figure 9, a drive signal is generated by the drive signal generation unit 10 and supplied to the drive circuit 3, and when the optical deflector 4 is driven by the drive circuit 3, the feature value calculation unit 11 instructs the drive signal generation unit 10 to control the drive frequency of the drive signal so as to maintain the resonant state (step S31).

[0038] When controlling the resonant state, the feature value calculation unit 11 acquires at least two drive frequencies from the drive signal generation unit 10, and calculates the phase differences of the sensor signals corresponding to those drive frequencies based on the sensor signals acquired from the sensor signal processing circuit 5, and stores these frequencies and phase differences in memory 2 (step S32).

[0039] The feature value calculation unit 11 calculates the slope B, which is a feature value of the frequency characteristics of the sensor signal, based on the drive frequency and phase difference stored in the memory 2. The detection unit 12 detects the rate of change of the deflection angle based on the calculated feature value (slope B) using a data table or the like pre-stored in the memory 2 (step S33). This completes the detection of the rate of change of the deflection angle.

[0040] The voltage level of the drive signal can also be corrected using the rate of change of the deflection angle obtained by any of the first to third embodiments. For example, assume that the deflection angle θ and the tilt B have the correspondence relationship shown in Fig. 10. In this case, if the optical deflector 4 is driven so that the tilt becomes B1, and the actually obtained tilt is B2 due to aging or other reasons, then it is sufficient to calculate a correction coefficient so that the tilt becomes B1, and correct the voltage level of the drive voltage.

[0041] Therefore, based on the rate of change of the deflection angle, for example, if the tilt obtained when driving at a deflection angle θ1 is B2, the ratio (θ1 / θ2) of the deflection angle θ2 corresponding to this tilt B2 to the deflection angle θ1 may be used as the correction coefficient. Alternatively, if the rate of change of the deflection angle corresponding to the tilt B1 is 100% and the rate of change of the deflection angle corresponding to the tilt B2 is 80%, the value obtained by calculating 100 / 80 may be used as the correction coefficient. Based on such a correction coefficient, the voltage level of the driving voltage may be corrected, for example, by multiplying the correction coefficient by the voltage level before correction. Note that the correction coefficient may be calculated so that the deflection angle is equal to or greater than a specific value, or so that the deflection angle falls within a specific range.

[0042] The voltage level of the drive signal is determined using the correction coefficient thus determined by the detection unit 12, and the voltage level is then indicated to the drive signal generation unit 10. As a result, the voltage level of the drive signal is corrected in accordance with the rate of change of the deflection angle.

[0043] According to the above-described embodiment, an optical scanning device can be obtained that can detect whether or not the drive voltage of the optical deflector needs to be corrected with a simple device configuration without reducing the scanning range.

[0044] The present disclosure is not limited to the above-described embodiment and can be modified in various ways within the scope of the present disclosure. For example, in the above-described embodiment, the slope B is used as an example of a feature value, which is information indicating the phase-frequency characteristics of a sensor signal. However, the feature value is not limited to this. As illustrated in FIG. 11, one or more phase differences at frequencies a specific magnitude away from the resonant frequency can also be used as the feature value. Furthermore, the phase differences at two or more frequencies can be fitted using curve approximation or the like (for example, the curve approximation expressed by the following formula) to determine a coefficient, which can then be used as the feature value. In the formula, ω3 and ω4 represent two frequencies, φ represents the phase difference, and ζ represents the coefficient. In either case, by storing the correspondence between the feature value and the deflection angle in the form of a data table or a function in memory 2, as in the case of the slope B, the rate of change of the deflection angle can be obtained based on the feature value.

[0045]

number

[0046] Furthermore, the timing for detecting the rate of change of the deflection angle is not limited to the cases described in the above embodiments. For example, when the photodetector is driven on two axes, there are times when the drive turns back, or when the laser light is turned off at the end of the scanning range where the laser light is scanned two-dimensionally, and there are also times when the laser light is turned off depending on the content that turns on the laser light. Therefore, the rate of change of the deflection angle may be detected at these times. Alternatively, the rate of change of the deflection angle may be detected when the drive of the optical deflector is stopped. Furthermore, a process for detecting the rate of change of the deflection angle may be added during product inspection before shipment. In this case, it is possible to take measures such as noise reduction processing (e.g., averaging), which requires time, or increasing the number of frequencies used for detection, thereby enabling more accurate detection of the rate of change of the deflection angle.

[0047] The present disclosure has the following additional features. (Appendix 1) an optical deflector having a mirror that operates by resonance and a sensor that detects the deflection angle of the mirror; a control device for controlling the operation of the optical deflector; a memory connected to the controller; a drive circuit for supplying a drive voltage to the optical deflector under the control of the control device; Including, The control device a drive signal generating unit that generates a drive signal including set values ​​for the drive frequency and voltage level of the drive voltage; a feature value calculation unit that calculates a phase difference between the sensor signal output from the sensor and the drive signal, acquires the drive frequency of the drive voltage from the drive signal generation unit, and calculates a feature value that is a value indicating a frequency characteristic of the phase difference of the sensor signal based on the phase difference and the drive frequency; a detection unit that detects a change in the deflection angle by referring to the data stored in the memory using the feature value calculated by the feature value calculation unit; It has the data stored in the memory includes information representing a correspondence relationship between the deflection angle and the feature value; Optical scanning device. (Appendix 2) The feature value is at least one of a gradient obtained from the relationship between the phase difference of the sensor signal and the drive frequency, one or more phase differences at frequencies that are a specific magnitude away from a frequency at which the drive frequency resonates, or a coefficient obtained when fitting is performed based on the phase differences of the sensor signal at at least two frequencies. 2. The optical scanning device according to claim 1. (Appendix 3) the data is a data table representing a correspondence relationship between the deflection angle and the feature value or a relational expression representing the correspondence relationship; 3. The optical scanning device according to claim 1 or 2. (Appendix 4) the change in the deflection angle detected by the detection unit is a rate of change of the deflection angle from a predetermined reference value; 4. The optical scanning device according to claim 1. (Appendix 5) The change in the deflection angle detected by the detection unit is information indicating whether the deflection angle satisfies a predetermined condition. 5. The optical scanning device according to any one of claims 1 to 4. (Appendix 6) the detection unit corrects a set value of the voltage level of the drive voltage in the drive signal generation unit in accordance with the detected change in the deflection angle. 6. An optical scanning device according to any one of claims 1 to 5. [Explanation of symbols]

[0048] 1: control device, 2: memory, 3: drive circuit, 4: optical deflector, 5: sensor signal processing circuit, 6: mirror, 7: sensor

Claims

1. an optical deflector having a mirror that operates by resonance and a sensor that detects the deflection angle of the mirror; a control device for controlling the operation of the optical deflector; a memory connected to the controller; a drive circuit for supplying a drive voltage to the optical deflector under the control of the control device; Including, The control device a drive signal generating unit that generates a drive signal including set values ​​for the drive frequency and voltage level of the drive voltage; a feature value calculation unit that calculates a phase difference between the sensor signal output from the sensor and the drive signal, acquires the drive frequency of the drive voltage from the drive signal generation unit, and calculates a feature value that is a value indicating a frequency characteristic of the phase difference of the sensor signal based on the phase difference and the drive frequency; a detection unit that detects a change in the deflection angle by referring to the data stored in the memory using the feature value calculated by the feature value calculation unit; It has the data stored in the memory includes information representing a correspondence relationship between the deflection angle and the feature value; Optical scanning device.

2. The feature value is at least one of a gradient obtained from the relationship between the phase difference of the sensor signal and the drive frequency, one or more phase differences at frequencies that are a specific magnitude away from a frequency at which the drive frequency resonates, or a coefficient obtained when fitting is performed based on the phase differences of the sensor signal at at least two frequencies.

2. The optical scanning device according to claim 1.

3. the data is a data table representing a correspondence relationship between the deflection angle and the feature value or a relational expression representing the correspondence relationship; 2. The optical scanning device according to claim 1.

4. the change in the deflection angle detected by the detection unit is a rate of change of the deflection angle from a predetermined reference value; 2. The optical scanning device according to claim 1.

5. The change in the deflection angle detected by the detection unit is information indicating whether the deflection angle satisfies a predetermined condition.

2. The optical scanning device according to claim 1.

6. the detection unit corrects a set value of the voltage level of the drive voltage in the drive signal generation unit in accordance with the detected change in the deflection angle.

2. The optical scanning device according to claim 1.

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