The present disclosure relates to an optical scanning apparatus, and an object detection apparatus.
Prior art of an optical scanning apparatus and an object detection apparatus is described in Japanese Unexamined Patent Application Publication No. 2010-151958, for example.
In a specific aspect, it is an object of the present disclosure to further widen measurement viewing angle in an optical scanning apparatus or the like.
(1) An optical scanning apparatus according to one aspect of the present disclosure is an optical scanning apparatus used for detecting an object by irradiating light and receiving the reflected light including: a deflector; a light source having at least a first light-emitting unit that emits a first light and a second light-emitting unit that emits a second light having optical characteristics different from that of the first light; a first optical element disposed so that the first light emitted from the first light-emitting unit is incident thereon and reflects the first light and causes it to be incident on the deflector; a second optical element disposed so that the second light emitted from the second light-emitting unit is incident thereon and reflects the second light and causes it to be incident on the deflector; where the first optical element has optical characteristics of reflecting the first light and transmitting the second light, and where the second optical element has optical characteristics of reflecting the second light and transmitting the first light.
(2) An object detection apparatus according to one aspect of the present disclosure is an object detection apparatus including: an optical scanning apparatus according to the above-described (1); a light receiving unit that detects the reflected light caused by the light irradiated from the optical scanning apparatus and generates a light receiving signal corresponding to the intensity of the reflected light; and a control unit that controls the operation of the optical scanning apparatus and generates point group information based on the light receiving signal.
According to the above configurations, it is possible to further widen measurement viewing angle in an optical scanning apparatus and an object detection apparatus including the same.
This object detection apparatus is mounted on a vehicle and used to detect objects around the vehicle (other vehicles, pedestrians, etc.), for example. In this case, the object detection apparatus can be positioned on the roof, near the emblem, near the rear-view mirror, inside the headlights of the vehicle, etc.
The controller 1 controls the overall operation of the object detection apparatus, and is configured to include a measurement control unit 10, a deflection control unit 11, a lighting control unit 12, a distance measurement unit 13, and a communication unit 14. This controller 1 can be realized by using a computer system equipped with a CPU, ROM, RAM, etc., for example, and having the computer system execute a predetermined operating program.
The measurement control unit 10 controls the operation of the deflection control unit 11, the lighting control unit 12, and the distance measurement unit 13, and also controls the communication unit 14 to transmit point group information, which is the measurement result of the distance measurement unit 13, to an external device (not shown).
The deflection control unit 11 controls the MEMS mirror 22 via the MEMS driver 20 of the scanning light source unit 2 so that it periodically deflects in a specified angle change pattern (typically a raster scan with uniform scanning line spacing).
The lighting control unit 12 controls a light source driver 21 so that a light source LS emits laser light under the pulse conditions specified by the measurement control unit 10.
The distance measurement unit 13 measures the distance to an object in the target space based on time difference between the time of emission and the time of reception of the laser light, using the timing of the instruction to generate laser light from the lighting control unit 12 and the light receiving signal obtained from the light receiving circuit 33 of the light receiving unit 3. Further, three-dimensional position of the object is also detected by the measurement control unit 10 based on the time of emission and the time of reception of the laser light.
The communication unit 14 transmits the obtained point group information (a collection of three-dimensional positions) to an external device (not shown).
The scanning light source unit 2 generates a narrow-angle laser light and emits the laser light in various directions within a predetermined range, and is configured to include a MEMS driver 20, a light source driver 21, a MEMS mirror 22, a light source LS, and a plurality of dichroic mirrors R.
The MEMS driver 20 is connected to the MEMS mirror 22, and under the control of the deflection control unit 11 of the controller 1, generates a drive signal that controls the operation of the MEMS mirror 22 and supplies it to the MEMS mirror 22.
The light source driver 21 is connected to the light source LS, and under the control of the lighting control unit 12 of the controller 1, generates a drive signal that controls the operation of the light source LS and supplies it to the light source LS.
The MEMS mirror 22 is a deflector that has a reflective surface and is configured to be rotatable in two orthogonal directions. This MEMS mirror 22 is disposed so that the laser lights emitted from the light source LS can be incident on the reflective surface from different directions, and rotates based on a drive signal supplied from the MEMS driver 20 in order to scan each laser light within the target space. Each laser light is emitted to the external target space from an opening 23 appropriately provided in the scanning light source unit 2.
The light source LS is configured to include a plurality of light-emitting units, each of which generates a plurality of laser lights of narrow-angle beams (beams with small divergence angles) as detection light based on a control signal from the lighting control unit 12, and emits each laser light (pulsed light). For example, each of the plurality of light-emitting units is a laser diode element. The laser light emitted from each light-emitting unit of the light source LS is a beam with a divergence angle that is comparable to (that is, the same as or smaller than) the angular resolution of the object detection apparatus. Each light-emitting unit of the light source LS can be a near-infrared photonic crystal laser (PCSEL), but is not limited thereto, and any light source LS that can emit a narrow-angle beam of detection light can be used.
The plurality of light-emitting units included in the light source LS includes a first light-emitting unit with predetermined optical characteristics and a second light-emitting unit with optical characteristics different from that of the first light-emitting units. For example, the first light-emitting unit and the second light-emitting unit may have different emission wavelengths or different polarization directions. The light source LS of the present embodiment has two of first light-emitting units and two of second light-emitting units, each with different emission wavelengths.
The light receiving unit 3 receives the reflected light produced by each laser light emitted from the light source LS and generates a light receiving signal, and is configured to include a lens 30, an optical filter 31, a photodetector (light receiving element) 32, and a light receiving circuit 33. This light receiving unit 3 may be configured as a coaxial optical system that receives light along the same optical path as the optical path from the light source LS to the MEMS mirror 22, or it may be configured as a non-coaxial optical system that does not use the same optical path.
The lens 30 collects the reflected light produced by the laser light emitted from the light source LS. The optical filter 31 blocks the light which is in a different wavelength range from the laser light emitted from the light source LS and transmits the light which is in the same wavelength range as the laser light emitted from the light source LS. The photodetector 32 detects the light incident through the optical filter 31.
The light receiving circuit 33 generates a light receiving signal by performing predetermined signal processing (e.g., amplification, frequency filtering, etc.) on the output of the photodetector 32. The generated light receiving signal is supplied to the distance measurement unit 13 of the controller 1.
The light source LS includes a plurality of light-emitting units LS1, LS2, LS3, and LS4 arranged in the depth direction of the sheet in
The laser light can be scanned by deflecting the MEMS mirror 22. For example, the laser light traveling in the Z direction shown in the figure is scanned up and down in the Y direction. The trajectory of the laser light becomes the irradiation area. A part of the irradiation area includes the positions of the dichroic mirrors R1, etc. as shown in the figure. The light reflected by the MEMS mirror 22 and incident on the dichroic mirrors R1, etc. transmits through the dichroic mirrors R1, etc. and proceeds from inside the housing of the scanning light source unit 2 to the outside. Here, when the laser light transmits through the dichroic mirrors R1, etc., the light path of the laser light is shifted from the light path before it enters due to internal refraction. However, since this shift in the light path is approximately the thickness of the dichroic mirrors R1, etc., it does not affect the distance measurement performance and can be corrected at the light receiving unit 3 side.
Here, each dichroic mirror R1, R2, R3, R4 is configured by laminating several to several hundred layers of thin films of high reflective refractive index materials such as titanium oxide, tantalum oxide, niobium oxide, etc., and thin films of low reflective refractive index materials such as silicon oxide and magnesium fluoride on a glass substrate based on a predetermined optical design. In the present embodiment, each of the dichroic mirrors R1, etc. is configured by laminating the above-described thin films on a glass substrate, and is configured to have a size of a short side of about 3 mm, a long side of about 8 mm, and a thickness of about 1 mm, for example. And a portion of about 3 to 4 mm along the long side is bonded and fixed to a slope provided in a position facing the MEMS mirror 22 inside the housing of the scanning light source unit 2, and the remaining portion not fixed to this slope is disposed to hang down from the slope. A photocurable resin or a thermosetting resin can be used to bond the dichroic mirrors R1, etc.
As shown in the layout diagrams of the XY plane and the XZ plane, the dichroic mirrors R1 to R4 are arranged at intervals along the X direction. In the layout diagrams of the XY plane and the YZ plane, the laser light emitted from each light-emitting unit LS1 to LS4 is emitted from below each of the dichroic mirrors R1, etc., and enters each of the dichroic mirrors R1, etc., and then enters the MEMS mirror 22. In the XY plane, the MEMS mirror 22 is arranged further back than each of the dichroic mirrors R1, etc., and in the YZ plane, the MEMS mirror is arranged relatively to the left of each of the dichroic mirrors R1, etc.
The laser light reflected by the MEMS mirror 22 either transmits through each of the dichroic mirrors R1, etc., or transmits through the gaps between each of the dichroic mirrors R1, etc. The former is shown in the layout diagram of the XZ plane of “BEFORE DRIVING”, and the latter is shown in the layout diagram of the XZ plane of “AFTER DRIVING”. When the MEMS mirror 22 is deflected, the laser light enters and transmits through each of the dichroic mirrors R1, etc. up to a certain deflection angle, and at a deflection angle beyond the certain angle, the laser light transmits through the gaps between each of the dichroic mirrors R1, etc. The reason why the laser light transmits through each of the dichroic mirrors R1, etc. will be described next.
As shown by the dotted line in
As shown by the dotted line in
The same applies to the relationship between light-emitting unit LS2 and dichroic mirror R2. The laser light with a wavelength of 900 nm emitted from light-emitting unit LS2 is incident on and reflected by dichroic mirror R2 having reflection characteristics for wavelengths of 900 nm or less, and is reflected by the MEMS mirror 22. Thereafter, the laser light transmits through dichroic mirror R3 having reflection characteristics for wavelengths of 950 nm or less and transmission characteristics for wavelengths of 900 nm or less, and is irradiated to the outside of the scanning light source unit 2.
The same applies to the relationship between light-emitting unit LS3 and dichroic mirror R3. The laser light with a wavelength of 950 nm emitted from light-emitting unit LS3 is incident on and reflected by dichroic mirror R3 having reflection characteristics for wavelengths of 950 nm or less, and is reflected by the MEMS mirror 22. Thereafter, the laser light transmits through dichroic mirror R2 having reflection characteristics for wavelengths of 900 nm or less and transmission characteristics for wavelengths of 950 nm or less, and is irradiated to the outside of the scanning light source unit 2.
According to the above embodiment, it is possible to further widen measurement viewing angle in an optical scanning apparatus or the like.
Here, note that the present disclosure is not limited to the content of the above described embodiment, and various modifications can be made within the scope of the gist of the present disclosure. For example, in the above embodiment, a dichroic mirror was shown as an example of an optical element for wavelength filtering, but a bandpass filter may be used instead of the optical element or in combination with the dichroic mirror. For example, a bandpass filter with a transmission band of 25 nm that transmits wavelengths of 900 nm±12.5 nm and reflects other wavelength ranges, or a bandpass filter with a transmission band of 25 nm that transmits wavelengths of 950 nm±12.5 nm and reflects other wavelength ranges can be used.
Further, in the embodiment described above, light source LS is arranged so that laser light emitted from the light source LS travels along the Y direction, but the arrangement of the light source LS is not limited thereto, and for example, the light source LS may be arranged by rotating the substrate on which it is mounted in the X direction. In such a case, the arrangement of each of the dichroic mirrors R1, etc. may be adjusted so that the laser light is incident along the normal direction (Z direction) of the MEMS mirror 22.
Further, in the embodiment described above, the MEMS mirror 22 is arranged so that its initial tilt is 0° with respect to the Y axis, but the MEMS mirror 22 may be arranged so that it is tilted at a maximum of about 5° with respect to the Y axis. In such a case, the position of each of the dichroic mirrors R1, etc. may be adjusted so that the laser light reflected by the MEMS mirror 22 with a deflection angle of 0° travels parallel to the Z direction.
Further, in the embodiment described above, a dichroic mirror is used as an example of an optical element, but similar effect can be obtained by using a reflective polarizer as the optical element. Here, the reflective polarizer may be a polarizing beam splitter or a wire grid polarizer, for example. In this case, a reflective polarizer may be disposed in the position where each of the dichroic mirrors R1, etc. were disposed in the embodiment described above. Further, in this case, as each of the light-emitting units LS1, etc. of the light source LS, a unit capable of emitting a laser light that has a high degree of polarization and is substantially linearly polarized is used. As one example, an end-face type laser diode that shows a high degree of polarization with S wave component of 90% or more can be used. The basic configuration of the scanning light source unit 2 of the above-described modified working example 1 is similar to that shown in
Each of the reflective polarizers R11, R12, R13, and R14 are respectively substituted for each of the dichroic mirrors R1, R2, R3, and R4 in the above-described embodiment. Each of the reflective polarizers R11, etc. is configured to have a size of about 3 mm on the short side, about 8 mm on the long side, and about 1 mm thick. When each of the reflective polarizers R11, etc. is a polarizing beam splitter, it is configured by laminating a dielectric multilayer film on a glass substrate or the like, and when it is a wire grid type, it is configured by providing a wire grid made of a metal such as aluminum on one side of a glass substrate or the like. And similar to the above-described embodiment, a portion of about 3 to 4 mm along the long side direction is fixed by bonding to a slope provided in a position facing the MEMS mirror 22 inside the housing of the scanning light source unit 2, and the remaining portion not fixed to this slope is arranged to hang down from the slope. When each of the reflective polarizers R11, etc. is configured with a polarizing beam splitter, each of the reflective polarizers R11, etc. is disposed at an angle such that the laser lights emitted from each of the light-emitting units LS1, etc. of the light source LS is incident at approximately 45°. To bond each of the reflective polarizers R11, etc., a photocurable resin or a thermosetting resin can be used, for example.
When the laser light is scanned by deflecting the MEMS mirror 22, a part of the irradiation area includes the position of the reflective polarizer R11, etc., as in the above embodiment. The light reflected by the MEMS mirror 22 and incident on the reflective polarizer R11, etc., transmits through the reflective polarizer R11, etc., and proceeds from inside the housing of the scanning light source unit 2 to the outside. When transmitting through the inside of the reflective polarizer R11, etc., the laser light is refracted inside, causing the optical path to shift from the path before it enters, but since this optical path shift is about the thickness of the reflective polarizer R11, etc., it does not affect the distance measurement performance and can be corrected at the light receiving unit 3 side.
Hereinafter, the operation of the scanning light source unit 2 of modified working example 1 will be described using combination No. 1 shown in
As shown by the dashed line in
Further, as shown by the dotted line in
The same applies to the relationship between light-emitting unit LS2 and reflective polarizer R12. The S wave laser light emitted from light-emitting unit LS2 is incident on and reflected by reflective polarizer R12 having reflection characteristics for S waves, and after being reflected by the MEMS mirror 22, transmits through reflective polarizer R13 having transmission characteristics for S waves, and is irradiated to the outside of the scanning light source unit 2.
The same applies to the relationship between light-emitting unit LS3 and reflective polarizer R13. The P wave laser light emitted from light-emitting unit LS3 is incident on and reflected by reflective polarizer R13 having reflection characteristics for P waves, and after being reflected by the MEMS mirror 22, transmits through reflective polarizer R12 having transmission characteristics for P waves, and is irradiated to the outside of the scanning light source unit 2.
Further, the optical scanning apparatus of modified working example 2 can be obtained by further combining a ¼ wavelength plate with the configuration of modified working example 1 described above. Here, the ¼ wavelength plate is a wavelength plate capable of converting incident linearly polarized light into circularly polarized light, or converting incident circularly polarized light into linearly polarized light. The scanning light source unit 2 of modified working example 2 has a configuration in which each of the dichroic mirrors R1, etc. in the configuration shown in
Each of the reflective polarizers R in this modified working example 2 is configured to have a size of, for example, a short side of about 1 mm, a long side of about 8 mm, and a thickness of about 1 mm, and a portion of 3 to 4 mm in the long side direction is glued and fixed to the housing. The ¼ wavelength plates T are also configured to have a similar size as the reflective polarizers R. The reason why the width (short side) of both the reflective polarizers R and the ¼wavelength plates T are small is that when deflected by the MEMS mirror 22, the incident angle of the laser light when it enters the reflective polarizers R and the ¼ wavelength plates T changes, causing the polarization direction of the laser light to shift, making it difficult to polarize by the reflective polarizers R, thereby the incidence of such a laser light with a large incident angle on the reflective polarizers R, etc. is reduced.
Hereinafter, the operation of the scanning light source unit 2 of modified working example 2 will be described using combination No. 1 shown in
As shown by the dotted line in
Further, as shown by the dotted line in
The same applies to the relationship between light-emitting unit LS2 and reflective polarizer R12. As shown by the dotted line in
The same applies to the relationship between light-emitting unit LS3 and reflective polarizer R13. As shown by the dotted line in
Here, in each of modified working examples 1 and 2, a flat reflective polarizer has been described, but a cube-shaped beam splitter may also be used. In this case, there is an advantage that the optical path length does not shift.
The present application is based on, and claims priority from, JP Application Serial Number, 2024-4461 filed on Jan. 16, 2024, the disclosure of which is hereby incorporated by reference herein in its entirety.
Number | Date | Country | Kind |
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2024-004461 | Jan 2024 | JP | national |