JP2012255738A - Optical measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance measurement performance in an optical measuring apparatus.SOLUTION: An optical measuring apparatus 1 includes a first light-receiving lens 11, an annular second light-receiving lens 12 arranged around the first light-receiving lens 11, a photodetector 15 for detecting light, and an optical element 13. The optical element 13 includes a waveguide 13a that guides light L1 received by the first light-receiving lens 11 and light L2 received by the second light-receiving lens 12 to the photodetector 15. The waveguide 13a is formed of a reflection plane 13b for reflecting light, and the cross section of which becomes smaller as it approaches the photodetector 15.

Description

  The embodiments discussed herein relate to an optical measurement device that performs measurements by detecting light.

As illustrated in FIGS. 6 and 7, the optical measurement device 200 is disposed, for example, in the center of the front end of the vehicle 100 and measures the distance from the measurement object 300 that is the preceding vehicle.
The optical measurement apparatus 200 includes a laser oscillator 201, a polygon mirror 202, a light receiving lens 203, a photodetector 204, and a housing 205.

The laser oscillator 201 emits laser light L11.
The polygon mirror 202 reflects the laser beam L11 on the outer peripheral surface while rotating.

The light receiving lens 203 is disposed on the surface of the housing 205 and receives the laser light L <b> 12 that is scattered light reflected by the measurement object 300.
The light detector 204 includes a light receiving circuit 204a and detects the laser light L12 incident from the light receiving lens 203.

  Further, as an optical measuring device, there is an optical measuring device using a lens that reflects light incident from the side to the outside and receives it by a light receiving element.

JP-A-5-332822 JP 2009-229462 A JP 2005-259824 A

  By the way, in the optical measuring device 200 as shown in FIG. 7, the light receiving lens 203 is a simple singlet (single-piece structure), so that the inclination θ from the incident optical axis A is large as shown in FIG. The light incident from the side may deviate from the light receiving area of the photodetector 204.

However, if the reflected light deviates from the light receiving region of the photodetector, the SNR (Signal to Noise Ratio) of the measurement signal is deteriorated, which causes an error in the measurement result such as distance.
Of the optical measuring devices described above, the optical measuring device using the lens that reflects the light incident from the side to the outside and receives the light to the light receiving element reliably transmits the light incident from the side to the lens. It is difficult to reflect on the detector.

  The optical measurement device disclosed in the present specification makes it possible to improve measurement performance.

  An optical measurement device disclosed in the present specification includes a first light receiving lens, an annular second light receiving lens disposed around the first light receiving lens, a photodetector for detecting light, and an optical An element. The optical element includes a waveguide for guiding light received by the first light receiving lens and light received by the second light receiving lens to the photodetector. This waveguide is formed of a reflective surface that reflects light, and the cross-sectional area becomes smaller as it approaches the photodetector.

  According to the optical measurement device disclosed in the present specification, the measurement performance can be enhanced.

It is a schematic block diagram which shows the optical measuring device which concerns on one embodiment. It is explanatory drawing for demonstrating the optical measuring device which concerns on one embodiment. It is sectional drawing which shows the optical element in one embodiment. It is a top view which shows the 2nd light receiving lens in one Embodiment. It is sectional drawing which shows the 2nd light receiving lens in one Embodiment. It is a top view which shows a vehicle provided with the optical measuring device which concerns on one embodiment. It is a top view which shows a vehicle provided with the optical measuring device which concerns on a reference technique. It is a schematic block diagram which shows the optical measuring device which concerns on a reference technique. It is explanatory drawing for demonstrating the optical measuring device which concerns on a reference technique.

Hereinafter, an optical measurement apparatus according to an embodiment will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram illustrating an optical measurement apparatus 1 according to an embodiment.
The optical measuring device 1 shown in FIG. 1 includes a first light receiving lens 11, a second light receiving lens 12, an optical element 13, a condenser lens 14, a photodetector 15, a housing 16, and an irradiation. Part 20. As will be described later, the optical measurement apparatus 1 measures the distance to the measurement object by detecting reflected light from the measurement object that is the vehicle (moving body) 100 illustrated in FIG. 5, for example. In addition, as the condensing lens 14, a biconvex lens and a planoconvex lens are employ | adopted, for example.

  As shown in FIG. 2, the first light receiving lens 11 mainly receives light L <b> 1 from the front, for example, at a position protruding from the surface of the housing 16. The first light receiving lens 11 is a meniscus lens in which the front surface portion 11a has a convex shape and the back surface portion 11b has a concave shape, but other shapes can also be used.

  The second light receiving lens 12 shown in FIGS. 4A and 4B has an annular shape and is arranged around the first light receiving lens 11. In the present embodiment, the second light receiving lens 12 is shorter in the front-rear direction (the direction of the incident optical axis A) than the first light receiving lens 11, but the front end of the second light receiving lens 12 is The position in the direction matches the position of the front end of the first light receiving lens 11.

  As shown in FIG. 2, the second light receiving lens 12 mainly receives the light L2 from the side. For example, the second light receiving lens 12 reflects the light L2 incident from the outer peripheral surface 12a toward the optical element 13 on the inner peripheral surface 12b.

  The outer peripheral surface 12a of the second light receiving lens 12 is, for example, an annular surface. The inner peripheral surface 12b is, for example, a conical surface whose diameter decreases from the front end opening 12c on the front side to the rear end opening 12d on the back side as it approaches the optical element 13. The rear end opening 12d is located deeper on the front side than the rear end of the outer peripheral surface 12a. The second light receiving lens 12 can have other shapes.

  The condensing lens 14 has both a front portion 14 a and a back portion 14 b having a convex shape, and emits light L 1 incident from the first light receiving lens 11 to the optical element 13. The condenser lens 14 can be omitted. In addition, one or more lenses other than the condensing lens 14 or a plurality of lenses including the condensing lens 14 are arranged between the first light receiving lens 11 and the second light receiving lens 12 and the optical element 13. Also good.

  The optical element 13 shown in FIG. 3 guides the light L1 incident indirectly from the first light receiving lens 11 via the condenser lens 14 and the light L2 incident from the second light receiving lens 12 to the photodetector 15. An optical waveguide 13a is included.

  The waveguide 13a is formed of, for example, a total reflection surface (an example of a reflection surface) 13b that is positioned on the outer peripheral surface and reflects (for example, total reflection) the light L1 and L2. It exhibits a horn shape with a reduced cross-sectional area. The cross-sectional area of the waveguide 13a may be reduced at a constant rate as in the case where the total reflection surface 13b is a conical surface, but the cross-sectional area gradually decreases as it approaches the photodetector 15. It is desirable to make it.

  The optical element 13 has a smaller cross-sectional area as it approaches the photodetector 15 at a portion other than the front end outer peripheral surface 13c having a constant diameter located at the front end. Therefore, in the present embodiment, the waveguide 13a is the entire portion of the optical element 13 below the front end outer peripheral surface 13c.

  The waveguide 13a may be hollow or made of other members. The total reflection surface 13 b may be a coating film or the like, or may be formed inside the optical element 13.

  The length H in the front-rear direction of the optical element 13 of the present embodiment is, for example, about 30 mm to 60 mm, but can be larger or smaller than this.

  The photodetector 15 receives the convergent lights L1 and L2 from the first light receiving lens 11 and the second light receiving lens 12. The photodetector 15 includes a light receiving circuit 15a that performs time measurement using a time-of-flight measurement method and binarization of an image, and detects a distance to a measurement target, for example.

  For example, the light receiving circuit 15a (the optical measuring device 1) uses the time required from when the light irradiating unit 20 described later irradiates light until the light detector 15 detects reflected light to reach the measurement target. Measure distance.

  The size W (the length or diameter of one side) of the photodetector 15 and its light receiving range is, for example, about several mm to several tens mm, but it can be made larger or smaller than this. . Further, the photodetector 15 may measure other elements such as the position and shape of the symmetrical object instead of the distance.

  The irradiation unit 20 includes a semiconductor laser diode 21, a collimator lens 22, a MEMS (Micro Electro Mechanical Systems) mirror 23, and a scanning magnification lens group 24 having a condenser lens 24a and a meniscus lens 24b.

The semiconductor laser diode 21 emits pulsed light L0 by being controlled to emit light by, for example, a pulse light emitting circuit 21a with an optical monitor circuit.
The collimator lens 22 converts the pulsed light L0 emitted from the semiconductor laser diode 21 into substantially parallel light.

  The MEMS mirror 23 is controlled to swing by the MEMS drive circuit 23a, reflects the substantially parallel light converted by the collimator lens 22, and scans within a range of several tens of degrees. The scanning magnifying lens group 24 further expands the scanning angle with the condensing lens 24a and the meniscus lens 24b into which the light emitted from the condensing lens 24a enters from the concave surface side.

  The optical measurement apparatus 1 may not include the irradiation unit 20 and may measure reflected light of sunlight or reflected sunlight of light irradiated by the irradiation unit of another apparatus.

  Hereinafter, the operation of the optical measurement apparatus 1 according to the present embodiment will be described while appropriately omitting the points overlapping with the above description.

  The above-described optical measuring device 1 may be arranged, for example, at a total of four locations on the front and rear, left and right of the vehicle 100 that is the moving body shown in FIG. 5, or only at the front portion FRONT and at the rear portion BACK. There is also a case.

  As shown in FIG. 1, the pulsed light L0 emitted by the semiconductor laser diode 21 of the irradiation unit 20 is converted into substantially parallel light by the collimator lens 22. The substantially parallel light is reflected by the MEMS mirror 23 controlled to swing, scanned within a range of several tens of degrees, and scanned over a wide range by the scanning magnification lens group 24.

  The laser light irradiated as described above is reflected by the vehicle 100 shown in FIG. 6 to become scattered light, and enters the first light receiving lens 11 and the second light receiving lens 12 as shown in FIG. 2 (laser light). L1, L2).

  The laser beams L 1 and L 2 incident on the first light receiving lens 11 and the second light receiving lens 12 are incident on the optical element 13 directly or indirectly via the condenser lens 14.

  The lights L1 and L2 incident on the optical element 13 are guided to the photodetector 15 while being reflected by the waveguide 13a formed by the total reflection surface 13b, and are detected by the photodetector 15. And the photodetector 15 measures the distance with a measuring object from the detected light.

  By the way, the range that can be measured by the distance measuring technique using the laser beam is a range in which the refracted light reaches the photodetector 15 when the laser beam returned to the measurement object is refracted by the light receiving lens. . In the present embodiment, the light L1 and L2 incident on the optical element 13 travels in the direction of the photodetector 15 while being totally reflected in the waveguide 13a and converges in the direction of the photodetector 15; The laser beams L1 and L2 incident from the incident optical axis A with an inclination θ of approximately 90 degrees can be detected by the photodetector 15. That is, the range that can be measured is expanded.

  In the present embodiment described above, the optical element 13 receives the light received by the first light receiving lens 11 and the lights L1 and L2 received by the annular second light receiving lens 12 disposed around the optical element 13. A waveguide 13a that guides light to the photodetector 15 is included. The waveguide 13 a is formed by a total reflection surface 13 b that totally reflects the light L 1 and L 2, and the cross-sectional area becomes smaller as it approaches the photodetector 15. Therefore, the light L2 from the side can be sufficiently received, for example, the signal quality for distance measurement can be improved, and errors in the measurement result can be reduced. Therefore, according to this Embodiment, measurement performance can be improved.

  Further, by receiving the lights L1 and L2 with the single photodetector 15, the stray capacitance is reduced, the band of the measurement signal is extended, and the signal quality can be improved.

  Further, when the optical measurement apparatus 1 performs distance measurement using the time-of-flight measurement method, the optical system can be arranged without considering the imaging performance (such as aberration) as long as the amount of light can be received. Therefore, it is not necessary to dispose a large number of aspherical lenses and the like, which can contribute to design freedom and simplification of the structure.

  The light beam reflected only once at the total reflection surface 13b and the light beam reflected twice or more change the flight distance of the light by the amount of the light path length until reaching the photodetector 15, so that the flight time, that is, The distance to the measurement object will be different.

  However, when there is a distance of, for example, several meters to 100 meters between the optical element and the measurement object, the optical path difference that reflects the inside of the optical element 13 having a diameter of several millimeters to several centimeters, for example, several times is several meters. Compared to the order of ~ 100 m, this is a negligible distance difference. Even when the optical measuring device 1 and the measuring object 100 are large, measurement that ignores the influence of the optical path difference is possible.

  In the present embodiment, the cross-sectional area of the waveguide 13a gradually decreases as it approaches the photodetector 15. Therefore, the light received by the optical element 13 can be more reliably guided to the photodetector 15, and therefore the measurement performance can be further improved.

  In the present embodiment, the total reflection surface 13 b is formed on the outer peripheral surface of the optical element 13. Therefore, measurement performance can be enhanced with a simple configuration.

  Further, in the present embodiment, the second light receiving lens 12 becomes smaller as the diameter of the inner peripheral surface 12b approaches the optical element 13, and light incident from the outer periphery (outer peripheral surface 12a) is incident on the inner peripheral surface 12b. Reflect toward (13). Therefore, the light receiving range of the second light receiving lens 12 is expanded, and the measurement performance can be further enhanced.

  The optical measurement apparatus 1 according to the present embodiment includes a light irradiation unit 20 that irradiates the measurement target with light, and the photodetector 15 reflects the reflected light of the light irradiated to the measurement target by the light irradiation unit 20. The optical measuring device 1 light receiving circuit 15a detects and measures the distance to the measurement object using the time required from the light irradiation unit 20 irradiating the light until the light detector 15 detects the reflected light. To do. Therefore, distance measurement performance can be improved.

DESCRIPTION OF SYMBOLS 1 Optical measuring device 11 1st light receiving lens 11a Front part 11b Back part 12 2nd light receiving lens 12a Outer peripheral surface 12b Inner peripheral surface 12c Front end opening part 12d Rear end opening part 13 Optical element 13a Waveguide 13b Total reflection surface 13c Front end outer peripheral surface 14 Condensing lens 14a Front portion 14b Back portion 15 Photo detector 15a Light receiving circuit 16 Housing 20 Irradiating portion 21 Semiconductor laser diode 21a Pulse light emitting circuit 22 Collimator lens 23 MEMS mirror 23a MEMS drive circuit 24 Scanning magnification lens group 24a Condenser lens 24b Meniscus lens 100 Vehicle

Claims (4)

A first light receiving lens;
An annular second light-receiving lens disposed around the first light-receiving lens;
A light detector for detecting light;
An optical element including a waveguide for guiding the light received by the first light receiving lens and the light received by the second light receiving lens to the photodetector;
Comprising
The waveguide is formed of a reflective surface that reflects light, and the cross-sectional area becomes smaller as it approaches the photodetector.
An optical measuring device. In the optical measuring device according to claim 1,
The reflective surface is formed on the outer peripheral surface of the optical element.
An optical measuring device. In the optical measuring device according to claim 1,
The second light receiving lens is smaller as the diameter of the inner peripheral surface approaches the optical element, and reflects light incident from the outer periphery toward the optical element on the inner peripheral surface.
An optical measuring device. In the optical measuring device according to claim 1,
It further comprises a light irradiator that irradiates the measurement object with light,
The light detector detects reflected light of the light irradiated to the measurement object by the light irradiation unit,
The optical measuring device measures the distance to the measurement object using the time required from the time when the light irradiation unit irradiates the light until the light detector detects the reflected light.
An optical measuring device.