JP7658796B2 - Optical scanning device, vehicle lighting device, and method for manufacturing optical scanning device - Google Patents

Description

The present invention relates to an optical scanning device that uses an optical deflector, a vehicle lamp that uses the optical scanning device, and a method for manufacturing the optical scanning device.

Conventionally, optical deflectors made with MEMS (Micro Electro Mechanical Systems) technology and optical scanning devices having such optical deflectors are known. Optical deflectors have a mirror section that rotates around a rotation axis, and reflect incident light in a direction according to the deflection angle of the mirror section, emitting the reflected light as scanning light. Typically, the irradiation area of the scanning light is rectangular, and areas of high and low illuminance are generated by overlapping irradiation areas of different sizes.

The oscillator device of Patent Document 1 has a mirror plate, which reflects light from a light source to form an irradiation trajectory on an object. At this time, the oscillator device oscillates the mirror plate by spiral drive.

Spiral drive (spiral scanning, helical scanning) is achieved, for example, by driving the mirror plate to rotate around a point on its central axis while modulating the tilt angle (oscillation angle) of the mirror surface of the mirror plate from the central axis when the mirror surface is not driven (Patent Document 1, paragraphs 0046 to 0049, Figure 4).

Patent No. 6670143

In the above oscillator device, spiral drive is achieved by matching the drive frequencies in the horizontal and vertical axis directions. However, in reality, there is a slight difference between the resonance frequencies in the horizontal and vertical axis directions due to manufacturing errors, etc. Therefore, when attempting to resonate drive both in the horizontal and vertical axis directions, it is difficult to control the deflection angle of the mirror plate, and there is a problem in that it is very difficult to design a two-axis optical deflector that can perform accurate spiral scanning.

The present invention was made in consideration of these circumstances, and aims to provide an optical scanning device for vehicle lamps that can perform accurate spiral scanning.

The optical scanning device for vehicle lamps of the present invention includes a first optical deflector having a rotating mirror that reflects incident light and scans the incident light in a vertical direction, a second optical deflector having a rotating mirror that scans the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction, and a drive unit that drives each of the first optical deflector and the second optical deflector, and the drive unit resonantly drives the first optical deflector and the second optical deflector with modulated waveforms having the same drive frequency but a phase difference of 90°, the drive frequency being matched with the peak resonant frequency of the second optical deflector, and the first optical deflector has a peak resonant frequency different from the drive frequency and is driven at the drive frequency.

The optical scanning device of the present invention resonates and drives a first optical deflector that scans incident light in the vertical direction and a second optical deflector that scans light in the horizontal direction using a drive unit to generate a light distribution pattern. The first optical deflector has a peak resonance frequency different from that of the second optical deflector. By driving the second optical deflector with a drive frequency that matches the peak resonance frequency of the second optical deflector, the deflection angle of the rotating mirror of the second optical deflector is kept relatively large.

The driving unit also drives the first optical deflector at the driving frequency (with a phase difference of 90°), so that the driving frequency is a frequency that is different from the peak resonance frequency of the first optical deflector. In other words, the scanning range (vertical direction) of the first optical deflector can be made smaller than the scanning range (horizontal direction) of the second optical deflector, resulting in an elliptical spiral scan with a long second scanning direction.

In the optical scanning device of the present invention, it is preferable that the difference between the peak resonant frequency of the first optical deflector and the peak resonant frequency of the second optical deflector is within the range of 3 to 50 Hz.

With this configuration, when the drive frequency is matched to the peak resonant frequency of the second optical deflector, the first optical deflector is driven at a frequency that is shifted from the peak resonant frequency within the range of 3 to 50 Hz. This optical scanning device can resonantly drive the first optical deflector even if the scanning range of the first optical deflector is smaller than the scanning range of the second optical deflector.

In addition, in the optical scanning device of the present invention, it is preferable that the deflection angle of the rotating mirror of the first optical deflector is within a range of D (0<D≦25)% with respect to the deflection angle of the rotating mirror of the second optical deflector when driven at the driving frequency and the same driving voltage.

The deflection angle of the rotating mirror of the first optical deflector is smaller than the deflection angle of the rotating mirror of the second optical deflector because the first optical deflector is driven at a frequency shifted from the peak resonant frequency. In the case of an optical scanning device used in a vehicle lamp, driving is required within a scanning range whose width in the vertical direction is smaller than that in the horizontal direction (approximately 25%). Therefore, even if the deflection angle of the rotating mirror of the first optical deflector is smaller than the deflection angle of the rotating mirror of the second optical deflector by D (0<D≦25)%, there is no need to make the maximum driving voltage value of the first optical deflector larger than the maximum driving voltage value of the second optical deflector.

The vehicle lamp of the present invention is characterized by comprising the optical scanning device described above, a light source that generates the incident light, a phosphor plate provided at a position where the scanning light of the rotating mirror of the second optical deflector is incident, and a projection lens that collects the light that has passed through the phosphor plate and projects a light distribution pattern.

According to this configuration, the incident light generated by the light source is scanned by the rotating mirror of the first optical deflector of the optical scanning device, then scanned by the rotating mirror of the second optical deflector, and the scanned light is incident on the phosphor plate. Furthermore, the light that passes through the phosphor plate passes through the projection lens to generate a light distribution pattern. This allows the vehicle lamp to project a desired light distribution pattern in front of the vehicle.

The vehicle lamp of the present invention further comprises a light source that generates incident light, a first optical deflector having a rotating mirror that reflects the incident light and that scans the incident light in a vertical direction, a second optical deflector having a rotating mirror that scans the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction, a drive unit that drives each of the first optical deflector and the second optical deflector, and a sensor that detects the scanning angle of each of the first optical deflector and the second optical deflector, and the drive unit drives the first optical deflector. The first optical deflector and the second optical deflector are resonantly driven with a modulation waveform having the same drive frequency but a phase difference of 90°, the drive frequency is matched to the peak resonance frequency of the second optical deflector, and the drive unit and the sensor respectively identify a first drive voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle and a second drive voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle, and set these as maximum drive voltages for driving the first optical deflector and the second optical deflector.

In the present invention, a sensor detects the scanning angle of each of the rotating mirrors of the first optical deflector and the second optical deflector. The drive unit and the sensor respectively identify a first drive voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle, and a second drive voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle. Furthermore, the first drive voltage and the second drive voltage are set to the maximum drive voltages of the first optical deflector and the second optical deflector, respectively. This allows the vehicle lamp to control each rotating mirror to drive at a desired deflection angle.

The manufacturing method of the optical scanning device for vehicle lamps of the present invention is characterized by comprising: a selection process for selecting two optical deflectors each having a rotating mirror that reflects light, and a drive unit that drives each of the two optical deflectors, the two optical deflectors having a deflection angle of 25% or more of a predetermined reference value under the same driving conditions and/or a difference in resonance frequency within a range of 3 to 50 Hz; an assembly process for assembling one of the two optical deflectors selected in the selection process as a first optical deflector that scans incident light in a vertical direction using a rotating mirror and the other as a second optical deflector that scans the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction using a rotating mirror; a peak resonance frequency acquisition process for acquiring a peak resonance frequency of the second optical deflector; and a drive frequency setting process for matching the drive frequency of the first optical deflector and the second optical deflector by the drive unit to the peak resonance frequency acquired in the peak resonance frequency acquisition process and setting them to the same frequency.

In the manufacturing method of the optical scanning device of the present invention, in the selection process, two optical deflectors to be used in the optical scanning device are selected. In particular, optical deflectors whose deflection angle under the same driving conditions is 25% or more of a reference value and whose difference in resonance frequency is within the range of 3 to 50 Hz are selected. Next, in the assembly process, one is made into a first optical deflector that scans vertically, and the other is made into a second optical deflector that scans horizontally. Furthermore, they are arranged so that the rotating mirror of the first optical deflector scans the incident light, and the rotating mirror of the second optical deflector scans the scanning light of the first optical deflector.

Next, in a peak resonance frequency acquisition process, the peak resonance frequency of the second optical deflector is acquired, and in a drive frequency setting process, the peak resonance frequency acquired in the peak resonance frequency acquisition process is set as the drive frequency of both optical deflectors. The first optical deflector is driven at a frequency that is different from the peak resonance frequency. With this method, since a difference occurs in the deflection angle of the rotating mirror between the first optical deflector and the second optical deflector (the deflection angle of the rotating mirror of the first optical deflector is smaller), it is possible to manufacture an optical scanning device that generates a light distribution pattern of a desired shape.

In addition, it is preferable that the manufacturing method of the optical scanning device of the present invention includes a drive voltage setting process for obtaining a first drive voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle and a second drive voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle, and setting these as maximum drive voltages for driving the first optical deflector and the second optical deflector, respectively.

In the drive voltage setting process, first, a first drive voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle and a second drive voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle are measured. Furthermore, the first drive voltage and the second drive voltage are set as the maximum drive voltages of the first optical deflector and the second optical deflector, respectively. This method makes it possible to manufacture an optical scanning device in which each rotating mirror is driven at a desired deflection angle.

1 is a diagram showing an overall configuration of a vehicle lamp according to an embodiment of the present invention; FIG. 2 is a diagram showing an internal configuration of a vehicle lamp and an optical scanning device. 1A is a diagram illustrating the frequency characteristics of a mirror rotating in the horizontal axis direction, and FIG. 1B is a diagram illustrating the frequency characteristics of a mirror rotating in the vertical axis direction. FIG. 4 is a diagram for explaining a driving waveform of an optical deflector. 7A to 7C are diagrams for explaining modified forms of the drive waveform of the optical deflector. 5 is a flowchart illustrating a manufacturing method of the optical scanning device.

The optical scanning device and vehicle lamp of the present invention will be described below with reference to the drawings.

(Overall composition)
1 shows the overall configuration of a vehicle lamp 1 according to an embodiment of the present invention. As shown in the figure, the vehicle lamp 1 is composed of an optical scanning device 10 and an optical system unit 20, and projects a generated light distribution pattern onto a virtual screen 30. The vehicle lamp 1 is used in a headlight mounted on a vehicle.

(Optical scanning device)
The optical scanning device 10 is composed of a light source 7, a condenser lens 8, and one-axis optical deflectors 11 and 12.

(light source)
The light source 7 is a laser diode (LD) having a central wavelength of about 450 nm, and emits blue light (light beam B). Note that a light emitting diode (LED) or the like may also be used as the light source.

(Condenser lens)
The light beam B emitted from the light source 7 is condensed by the condenser lens 8 and then reaches the optical deflector 11. The condenser lens 8 is a collimator lens (e.g., focal length 1.96 mm, diameter 2.6 mm, axial thickness 1.5 mm) and converts the incident light beam B into a substantially parallel light beam and guides it to the optical deflector 11.

(Optical deflector)
The optical deflector 11 (the "first optical deflector" of the present invention) includes a rotating mirror 11a and reflects and scans the light beam B within a predetermined angular range. The optical deflector 11 includes an actuator that drives the rotating mirror 11a. The actuator is a torsion bar (not shown) that resonantly drives the rotating mirror 11a around a first axis.

In the optical scanning device 10, the optical deflector 11 is disposed on the optical axis so that light is incident on the center of the rotating mirror 11a. As an optical deflector equipped with such a mirror, for example, a mirror of a known configuration described in JP 2020-197653 A can be used.

In the optical scanning device 10, the optical deflector 11 scans the vertical axis direction (V axis direction) of the light distribution pattern projected onto the virtual screen 30. The scanning light S1 scanned by the optical deflector 11 (rotating mirror 11a) reaches the optical deflector 12 (the "second optical deflector" of the present invention) and is reflected by the rotating mirror 12a.

The configuration of the optical deflector 12 is basically the same as that of the optical deflector 11 described above, but the peak resonance frequency is different from that of the optical deflector 11. Here, the peak resonance frequency refers to the frequency at which the deflection angle of the rotating mirror 12a is maximum when the driving voltage is the same. In the optical scanning device 10, the optical deflector 12 scans the horizontal axis direction (H axis direction) of the light distribution pattern projected onto the virtual screen 30.

In the optical scanning device 10 of the present invention, the scanning range (V-axis direction) of the optical deflector 11 is smaller than the scanning range (H-axis direction) of the optical deflector 12. In this embodiment using two optical deflectors, narrowing the scanning range of the optical deflector on which light is first incident reduces the irradiation range of the optical deflector on which light is next incident, making it easier to arrange them. Therefore, the optical deflector 11 (rotating mirror 11a) is arranged at the position where the linear light beam B is incident, and the optical deflector 12 is arranged at the position where the scanning light S1 from the optical deflector 11 is incident.

(Optical system unit)
The optical system unit 20 is composed of a phosphor plate 13 and a projection lens 14. The scanning light S2 scanned by the optical deflector 12 (rotating mirror 12a) is incident on the phosphor plate 13.

(Phosphor plate)
The phosphor plate 13 is a flat plate on which a yellow phosphor is applied to a certain thickness at approximately the center of a sapphire substrate. The yellow phosphor is made of, for example, Y3Al5O12:Ce3+, and when irradiated with the scanning light S2 (blue light), the wavelength is converted to emit yellow light, which is a complementary color to the blue light.

As a result, an area with a luminance distribution for generating a light distribution pattern is formed in the yellow phosphor, and white light that is a mixture of blue light and yellow light is emitted. The white light is incident on the projection lens 14, which will be described later.

(Projection lens)
The projection lens 14 is composed of, for example, four lenses, each of which is held by a lens holder. Each lens has the role of suppressing distortion and the like and improving the resolution of the light distribution pattern. The lens closest to the phosphor plate 13 is disposed so that its rear focal point is at the position of the phosphor plate 13.

The projection lens 14 is not limited to a four-lens configuration, and if the phosphor plate 13 is curved, the light distribution pattern can be projected with fewer lenses. The projection lens 14 also suppresses the aberration of the light from the phosphor plate 13, and projects the image forward while enlarging it. Then, the light distribution pattern is generated on a virtual screen 30 (for example, positioned about 25 m ahead of the vehicle lamp 1).

Next, the internal configuration of the optical scanning device 10 will be described with reference to FIG. 2. Note that the lamp control ECU 2 and the control device 3, which will be described later, are located outside the optical scanning device 10.

(Lamp control ECU)
A lamp control ECU (Engine Control Unit) 2 receives lighting modes such as light distribution modes (Hi/Lo/ADB) and image information from a camera (not shown) (position information of preceding vehicles, oncoming vehicles, etc.) from a higher-level system and transmits the information to the control device 3.

(Control device)
In addition, the control device 3 determines the size of the light distribution (illumination area) and the light distribution pattern to be generated by the optical scanning device 10 , and the position of the light distribution area to be projected, converts the signals, and transmits them to the light distribution generating unit 4 .

(Internal configuration of optical scanning device)
The optical scanning device 10 includes a light distribution generating unit 4 , a light distribution angle control unit 5 , a current control unit 6 , a light source 7 , and optical deflectors 11 and 12 .

(Light distribution generating unit, light distribution angle control unit)
The light distribution generation unit 4 transmits scanning range information of the optical deflectors 11, 12 (rotating mirrors 11a, 12a) to the light distribution angle control unit 5. The light distribution angle control unit 5 (the "drive unit" of the present invention) receives the scanning range information, controls the actuators so as to drive the rotating mirrors 11a, 12a, and adjusts the range of the deflection angle of the rotating mirrors 11a, 12a. At the same time, the light distribution generation unit 4 generates light distribution data and transmits it to the current control unit 6. In addition, the light distribution angle control unit 5 transmits scanning position information of the rotating mirrors 11a, 12a to the current control unit 6. At this time, the light distribution generation unit 4 may use data for generating the light distribution data stored in a storage unit (not shown) such as a RAM or ROM.

(Current control section)
The current control unit 6 controls the drive current of the light source 7 based on the received light distribution data and scanning position information. In particular, the current control unit 6 controls the current supplied to the light source 7 in order to turn the light source 7 on and off and change the light amount of the light source 7. The light beam B emitted from the light source 7 is scanned by the rotating mirrors 11a and 12a of the optical deflectors 11 and 12, and then projected as a predetermined light distribution pattern via the optical system unit 20.

In this way, the vehicle lamp 1 of this embodiment performs light distribution control using the light source 7 and the optical deflectors 11, 12, etc., and generates an elliptical light distribution pattern with a long horizontal axis direction, as shown in Figure 2. The principle of how the elliptical light distribution pattern is generated is explained below.

Next, the frequency characteristics of the optical deflector will be described with reference to Figure 3. Figure 3 shows the change in the optical deflection angle when the frequency is changed while keeping the driving voltage constant. In the frequency characteristics of Figures 3(a) and 3(b), the horizontal axis is frequency and the vertical axis is optical deflection angle.

3A shows the frequency characteristics of the rotating mirror 12a of the optical deflector 12 that scans in the horizontal axis direction. The peak resonance frequency of the rotating mirror 12a is _fH [kHz]. As described above, at the peak resonance frequency _fH , the optical deflection angle is maximum. Note that the resonance frequency is simply the frequency at which resonance occurs. The optical scanning device 10 of this embodiment drives the optical deflector 12 (rotating mirror 12a) at a drive frequency _fS [kHz] that coincides with the peak resonance frequency _fH [kHz].

3B shows the frequency characteristics of the rotating mirror 11a of the optical deflector 11 that scans in the vertical axis direction. The peak resonance frequency of the rotating mirror 11a is f _V [kHz], which is different from the peak resonance frequency f _H [kHz] of the rotating mirror 12a. The difference in resonance frequency is mainly caused by errors (variations) during manufacturing, but is preferably within the range of 3 to 50 [Hz]. Note that f _H < f _V or f _H > f _V may be acceptable.

Selecting an optical deflector based on strict criteria, such as a peak resonance frequency difference of within 3 Hz, would require a great deal of labor. The present invention is applicable even when the difference in frequency characteristics is large (25 Hz or more). However, since there is a possibility that resonance itself will not occur, it is preferable that the difference be within 50 Hz.

Furthermore, the optical deflection angle of the rotating mirror 11a at the peak resonance frequency f _H [kHz] is smaller (less than 100%) than the optical deflection angle of the rotating mirror 12a under the same driving voltage condition, and is 25% or more. In the case of a vehicle lamp (headlamp), a light distribution area (scanning range) whose width in the vertical axis direction is about 1/4 of that in the horizontal axis direction is required. In order to realize such requirements specific to vehicle lamps, the present invention makes it possible to make the maximum driving voltage value of the optical deflector 11 in the vertical axis direction equal to or less than the maximum driving voltage value of the optical deflector 12 in the horizontal axis direction by setting the optical deflection angle to 25% or more.

The optical deflection angle of the rotating mirror 11a can also be controlled by making the maximum drive voltage value larger than that of the rotating mirror 12a. However, even in this case, it is preferable that the optical deflection angle of the rotating mirror 11a at the peak resonance frequency _fH [kHz] is smaller (less than 100%) than the optical deflection angle of the rotating mirror 12a under the same drive voltage condition, and is 20% or more.

If the same drive conditions (drive voltage value, drive frequency f _H [kHz]) were adopted for the vertical and horizontal axis directions as assumed in Patent Document 1, the difference would be obvious to the human eye. Even an optical deflector 11 with an optical deflection angle of 50 to 70% or less of that of the optical deflector 12 can be used without any problems in the present invention. This means that the optical deflector to be used can be easily selected in the present invention.

In the optical scanning device 10, the optical deflector 11 (rotating mirror 11a) is also driven at the same driving frequency f _S [kHz] as the optical deflector 12 (rotating mirror 12a). That is, the rotating mirror 11a uses a frequency different from the peak resonance frequency f _V [kHz], and therefore, when driven with the same driving voltage, the deflection angle is smaller than that of the above-mentioned rotating mirror 12a. As a result, a rectangular light distribution pattern is generated in which the horizontal axis direction scanned by the rotating mirror 12a is long and the vertical axis direction scanned by the rotating mirror 11a is short.

Fig. 4 shows the drive waveforms of the optical deflectors 11 and 12. The waveform on the left side of Fig. 4 shows the "vertical axis drive waveform" by the rotating mirror 11a. The frequency of this drive waveform coincides with the above-mentioned operating frequency f _S [kHz], but since it is amplitude modulated, the amplitude is small at the center and increases toward the periphery.

In the case of a sine wave modulation waveform, the scanning length per unit time is short in the center, so the amount of light is greater. In addition, by adjusting the modulation waveform, it is possible to generate areas of high and low illuminance. As a result, a variety of light distribution patterns can be realized.

The waveform on the lower right side of Fig. 4 shows the "horizontal axis drive waveform" by the rotating mirror 12a. The frequency of the drive waveform is the operating frequency _fH [kHz], and since it is also amplitude modulated, the amplitude is small at the center and increases toward the periphery. Since the operating frequency _fS [kHz] matches the resonance frequency _fH [kHz] of the rotating mirror 12a, a large amplitude can be realized efficiently.

The deflection angle of the rotating mirror 12a is about ±20°, while the deflection angle of the rotating mirror 11a is about ±5°. The frequency characteristics of the rotating mirror 11a, i.e., the deflection angle when driven with the same driving voltage, may be up to 25% smaller than the deflection angle of the rotating mirror 12a.

The maximum drive voltage of the optical deflector 11 can be set to be equal to or less than the maximum drive voltage value of the optical deflector 12, with the drive voltage at the point where the amplitude of the peripheral portion of the "vertical axis drive waveform" is the largest. The maximum drive voltage of the optical deflector 12 does not vary significantly due to the influence of manufacturing errors, and the optical scanning device 10 can be designed based on the previously predicted maximum drive voltage of the optical deflector 12.

In addition, the drive waveform in the horizontal axis direction is 90° out of phase with the drive waveform in the vertical axis direction, so the peaks of the waveform are shifted when compared at the center of the drive waveform. This makes it possible to perform a spiral scan like the "scanning pattern" in the figure, generating an elliptical light distribution pattern with a bright center.

The drive waveforms in the vertical and horizontal directions are not limited to the shapes shown in FIG. 4. In FIG. 4, the dashed line C connecting the antinodes of the drive waveform is also a sine wave. Meanwhile, FIG. 5 shows a modified form of the drive waveform. For the drive waveform in FIG. 4, the dashed line C' connecting the antinodes of the drive waveform in the center of the modulated waveform has longer rise and fall times than a sine wave shape, and shorter rise and fall times in the peripheral parts of the modulated waveform, so that the central part of the light distribution pattern becomes brighter.

In the drive waveform of FIG. 5, the period of the waveform depicted by dashed line C' is the same as the period of dashed line C in FIG. 4. The drive waveform of FIG. 5 may be applied to both the drive waveforms of optical deflectors 11 and 12, or to only one of the optical deflectors 11 and 12, i.e., the drive waveforms of FIG. 4 and FIG. 5 may be used in the vertical axis direction and the horizontal axis direction. As a result, the light distribution pattern has narrower spiral spacing toward the center, and the illuminance in the center portion is higher.

Finally, a manufacturing method for the optical scanning device 10 will be described with reference to Figure 6.

First, an optical deflector selection process is carried out (STEP 01). This is a process for selecting two optical deflectors to be used in the optical scanning device 10. Even optical deflectors of the same design, with the same size, shape, weight, etc., will have slight errors in their resonant frequencies due to manufacturing variations.

In this process, optical deflectors whose peak resonance frequency differs by at most 50 Hz are selected using a predetermined resonance frequency as the reference. Two optical deflectors may be selected under the condition that the deflection angle of the rotating mirror under the same conditions (driving frequency and driving voltage) is within a range of 25% or more of a predetermined deflection angle (reference value), or two optical deflectors that satisfy both the resonance frequency condition and the deflection angle condition may be selected. For example, if an optical deflector with a resonance frequency of 21,864 Hz is used as the reference, the resonance frequency at which the deflection angle is 1/4 is 21,830 Hz (Δ34 Hz).

Next, the optical scanning device assembly process is performed (STEP 02). This is a process for assembling the optical scanning device 10 using the two optical deflectors selected in the optical deflector selection process (STEP 01). One of the two optical deflectors is used as an optical deflector for scanning in the vertical axis direction, so it is placed in a position in the optical scanning device where the light beam from the light source is incident on the rotating mirror (optical deflector 11 in Figure 1).

The other of the two optical deflectors is used as an optical deflector for scanning in the horizontal axis direction, and is therefore placed in a position in the optical scanning device where the scanning light from one of the optical deflectors is incident on the rotating mirror (optical deflector 12 in Figure 1). Note that the light source and the condenser lens are also components of the optical scanning device, and are therefore placed on the optical axis (see Figure 1).

Next, a peak resonance frequency acquisition step is performed (STEP 03). This is a step of measuring and acquiring the peak resonance frequency _fH of the optical deflector 12 for scanning in the horizontal axis direction. The resonance frequency _fH is used as the drive frequency _fS .

Next, a drive frequency setting step is performed (STEP 04). This is a step in which the peak resonance frequency _fH obtained in the previous step is set as the drive frequency _fS at which the light distribution angle control unit 5 drives both optical deflectors. Since the optical deflector for scanning in the horizontal axis direction is driven at the peak resonance frequency and the optical deflector for scanning in the vertical axis direction is operated at a frequency slightly shifted from the peak resonance frequency, the deflection angle of the rotating mirror is larger for the optical deflector for scanning in the horizontal axis direction when they are driven with the same drive voltage.

Next, a drive voltage setting process is performed (STEP 05). This is a process for acquiring the drive voltages for both optical deflectors. Specifically, the optical deflector for vertical axis scanning is driven at the drive frequency determined in the drive frequency acquisition process, and a voltage value is acquired that results in the desired deflection angle of the rotating mirror (e.g., 5°). This voltage value becomes the maximum drive voltage for the optical deflector for vertical axis scanning.

Similarly, the optical deflector for horizontal axis scanning is driven at the drive frequency determined in the drive frequency acquisition process to obtain a voltage value at which the rotating mirror has the desired deflection angle (e.g., 20°). This voltage value becomes the maximum drive voltage for the optical deflector for horizontal axis scanning. In the optical scanning device 10, the maximum drive voltages of both optical deflectors are measured and set in advance, and both optical deflectors are driven at the maximum drive voltage.

The drive waveforms for both optical deflectors have the same drive frequency, but are out of phase with each other by 90 degrees. This results in a light distribution pattern that is elliptical in shape with a long horizontal axis and high illuminance in the center.

The vehicle lamp 1 may be provided with a sensor to carry out the steps from STEP 03 onwards. This sensor is capable of detecting the scanning angles in both the vertical and horizontal axis directions. For example, a sensor for measuring the scanning angle is attached to the phosphor plate 13. The scanning angle may also be measured by the means disclosed in JP2019-509507A (a photodetector arranged outside the scanning area).

As disclosed in JP 2019-219549 A, the optical deflector may have a sensor that detects the amount of deformation of the piezoelectric actuator. The device in the publication is a two-dimensional optical deflector, but it can also be made into a one-dimensional optical deflector by using a semi-annular piezoelectric actuator with a similar shape.

In the case of a vehicle lamp having the above sensor, the same process as STEP 03 and thereafter can also be performed after manufacture. For example, the peak resonance frequency acquisition process is started when the vehicle lamp is turned on. This process is performed by the light distribution angle control unit 5 driving the optical deflector 12 for horizontal axis scanning at a constant drive voltage while changing the frequency, setting the frequency at which the sensor signal gives the maximum deflection angle as the peak resonance frequency, and storing it in the memory unit. Note that if the peak resonance frequency has already been set, it can be overwritten.

The peak resonance frequency is then set as a common drive frequency. Then, for each of the optical deflector 11 for vertical axis scanning and the optical deflector 12 for horizontal axis scanning, the light distribution angle control unit 5 changes the drive voltage at a constant drive frequency, and the voltage value at which the sensor is at a specified deflection angle (for example, 20° in the horizontal axis direction and 5° in the vertical axis direction) is set as the maximum drive voltage and stored in the memory unit. Note that if a maximum drive voltage has already been set, it can be overwritten.

For vehicle lamps that operate in this way, it is possible to select optimal driving conditions even when the peak resonance frequency changes due to deterioration of the optical deflector.

In the above embodiment, a blue laser diode is used as the light source, but this is not limited to this. The optical axes of three RGB lasers may be aligned using optical fibers or a dichroic mirror, etc., to produce white laser light. In this case, the phosphor plate may be omitted and the scanning light may be made to directly enter the projection lens. Instead of the phosphor plate, a diffusion plate that only has a diffusion effect by roughening the surface may be placed.

Although the above describes an embodiment for carrying out the present invention, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the gist of the present invention.

1...vehicle lamp, 2...lamp control ECU, 3...control device, 4...light distribution generating unit, 5...light distribution angle control unit (drive unit), 6...current control unit, 7...light source, 8...concentrating lens, 10...optical scanning device, 11...optical deflector (first optical deflector), 12...optical deflector (second optical deflector), 11a, 12a...rotating mirror, 13...phosphor plate, 14...projection lens, 20...optical system unit, 30...virtual screen.

Claims (6)

a first optical deflector having a rotating mirror that reflects incident light and that scans the incident light in a vertical direction;
a second optical deflector having a rotating mirror for scanning the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction;
a driving unit that drives each of the first optical deflector and the second optical deflector,
the driving unit resonantly drives the first optical deflector and the second optical deflector with modulation waveforms having the same driving frequency, a phase difference of 90°, and different maximum driving voltages;
the drive frequency is set to coincide with a peak resonance frequency of the second optical deflector;
The optical scanning device for a vehicle lamp, wherein the first optical deflector has a peak resonance frequency different from the drive frequency, and is driven at the drive frequency. The optical scanning device for vehicle lamps according to claim 1, characterized in that the difference between the peak resonant frequency of the first optical deflector and the peak resonant frequency of the second optical deflector is within the range of 3 to 50 Hz. An optical scanning device according to claim 1 or 2;
A light source generating the incident light;
a phosphor plate provided at a position where the scanning light of the rotating mirror of the second optical deflector is incident;
a projection lens that collects the light that has passed through the phosphor plate and projects a light distribution pattern;
A vehicle lamp comprising: A light source generating incident light;
a first optical deflector having a rotating mirror that reflects the incident light and that scans the incident light in a vertical direction;
a second optical deflector having a rotating mirror for scanning the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction;
a driving unit that drives each of the first optical deflector and the second optical deflector;
a sensor for detecting a scanning angle of each of the first optical deflector and the second optical deflector,
the driving unit resonantly drives the first optical deflector and the second optical deflector with modulation waveforms having the same driving frequency, a phase difference of 90°, and different maximum driving voltages;
the drive frequency is set to coincide with a peak resonance frequency of the second optical deflector, which is set by driving the second optical deflector while changing the frequency at a constant drive voltage and obtaining a maximum deflection angle based on the signal of the sensor;
The vehicle lamp is characterized in that the driving unit and the sensor respectively identify a first driving voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle and a second driving voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle, and set these as maximum driving voltages for driving the first optical deflector and the second optical deflector. The optical deflector includes two optical deflectors each having a rotating mirror that reflects light, and a driving unit that drives each of the two optical deflectors,
a selection step of selecting the two optical deflectors having a deflection angle under the same driving condition that is 25% or more of a predetermined reference value and/or a difference in resonance frequency that is within a range of 3 to 50 Hz;
an assembling process for assembling one of the two optical deflectors selected in the selecting process as a first optical deflector that scans incident light in a vertical direction by a rotating mirror and the other as a second optical deflector that scans the scanning light of the first optical deflector in a horizontal direction perpendicular to the vertical direction by a rotating mirror;
a peak resonance frequency acquisition step of acquiring a peak resonance frequency of the second optical deflector;
a drive frequency setting step of setting a drive frequency of the first optical deflector and the second optical deflector by the drive unit to be equal to the peak resonance frequency acquired in the peak resonance frequency acquisition step;
A method for manufacturing an optical scanning device for a vehicle lamp, comprising: The method for manufacturing an optical scanning device for vehicle lighting described in claim 5 further includes a drive voltage setting process for obtaining a first drive voltage at which the rotating mirror of the first optical deflector has a first predetermined deflection angle and a second drive voltage at which the rotating mirror of the second optical deflector has a second predetermined deflection angle, and setting these as maximum drive voltages for driving the first optical deflector and the second optical deflector, respectively.

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