JP2002214327A - Range finding device and object detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range finding device and an object detection device capable of detecting light beams reflected from an object to be measured, and capable of high-precision range finding. SOLUTION: A projecting optical system 11 includes a light source 12 and a projecting lens (collimating lens) 13 serving as a light intensity correcting means. The light source 12 is a laser diode (LD) for outputting light beams corresponding to a drive signal input from a laser diode drive circuit (LD drive circuit) 33. The projecting lens 13 is for projecting the light beams output from the LD 12 toward the object T to be measured, and for correcting the intensity distribution of the light beams output from the LD 12; the intensity distribution of the light beams is corrected so that the light beams output from the LD 12 at a position a predetermined distance away from the projecting lens 13 have higher intensity at their peripheries than near their optical axes. The projecting lens 13 includes an aspherical lens portion and a cylindrical lens portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for measuring a distance to an object to be measured, and an object detecting device using the distance measuring device.

[0002]

2. Description of the Related Art Conventionally, for example, ETC (Electronic Tol
l Collection System)
An irradiation optical system that uses a light source (such as a laser diode) that generates irradiation light emitted to the outside, and a detection optical system that uses a light receiving element or the like that detects reflected light from an object to be measured A distance measuring device is known which detects the presence or absence of an object to be measured in a detection direction by the presence or absence of light reception, and detects the distance to the object to be measured from a time difference / phase difference between irradiation light and reflected light. I have.

For example, Japanese Patent Application Laid-Open No. 7-253462 discloses a transmission optical system for transmitting light emitted from a laser light source, and receiving light reflected from an object and returned from light transmitted from the transmission optical system. Receiving means for outputting a received signal, detecting means for detecting an object based on the received signal, and calculating a distance to the object by measuring a round trip time to the object based on a difference between a light transmission timing and a reception timing. There is disclosed a distance measuring device provided with a calculating means for performing the above. In the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 7-253462, the transmission optical system includes a fly-eye lens having a plurality of main points arranged in parallel to flatten the light flux intensity distribution of light. The light from the laser light source is transmitted with the intensity distribution flattened by the fly-eye lens, and the light projected on the object is the one in the central part of the measurement light beam,
Alternatively, regardless of the peripheral portion, the intensity does not differ, the error due to the intensity distribution of the light emitted from the light source is reduced, and highly accurate distance measurement can be performed.

[0004]

As a result of investigation and research by the present inventors, it has been found that the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 7-253462 has the following problems. did. In the distance measuring device disclosed in Japanese Patent Application Laid-Open No. 7-253462, a fly-eye lens is used for a transmission optical system. However, since the luminous intensity distribution of the laser light source has a Gaussian distribution (high near the optical axis and low near the periphery), the fly-eye lens only subdivides the luminous flux having the Gaussian luminous intensity. Therefore, it is difficult to flatten the emission intensity distribution of the entire light beam.

[0005] Even if the luminous intensity distribution of the entire light beam is flattened, if only a part of the cylindrical or columnar object to be measured enters the irradiation range of the light beam emitted from the light source, the object to be measured is The amount of reflected light from the object is reduced, making it difficult to detect the reflected light itself, which may result in poor detection accuracy and accuracy. In a cylindrical or columnar object to be measured, the light reflecting surface is a curved surface. For this reason, when a light beam is irradiated on the central part of the measured object,
The irradiated light beam is specularly reflected and the reflected light beam has a high light intensity. However, when the light beam is irradiated to the end (peripheral portion) of the object to be measured, the end portion has a large curvature due to a large curvature, so that the reflected light beam has a large scattering. The light intensity decreases dramatically. Further, since the light emission intensity distribution of the laser light source is a Gaussian distribution as described above, the light intensity itself at the periphery of the light beam is lower than the light intensity near the optical axis of the light beam. For these reasons, in a state where only the end of the measured object whose outer shape is a curved surface enters the irradiation range of the light beam, the light intensity of the reflected light beam is extremely low, and detection becomes difficult.

The present invention has been made in view of the above points, and a distance measuring apparatus and an object detecting apparatus capable of reliably detecting a reflected light beam from an object to be measured and performing highly accurate distance measurement. The purpose is to provide.

[0007]

A distance measuring apparatus according to the present invention includes a light projecting optical system for irradiating a light beam output from a light source toward an object to be measured, and a light reflected by the object to be measured. A detection optical system for detecting the reflected light beam, and a distance measuring device for measuring a distance to the object to be measured, wherein the light projecting optical system has a light intensity near the optical axis of the light beam at a position separated by a predetermined distance. It is characterized by having light intensity correction means for increasing the light intensity at the peripheral portion of the light beam.

In the distance measuring device according to the present invention, since the light projecting optical system has the light intensity correcting means, the light intensity distribution of the light beam output from the light source and irradiated on the object to be measured has a light intensity distribution around the light beam. The light intensity distribution of the portion is higher than the light intensity near the optical axis of the light beam. Accordingly, when the light of the peripheral part of the light flux enters the end of the measured object whose outer shape such as a cylinder or a column is a curved surface, the light of the reflected light flux from the end of the measured object is The intensity is higher than the light intensity distribution of the light beam output from the light source is Gaussian distribution or flattened. Therefore, even in a state where only the end of the measured object whose outer shape is a curved surface enters the irradiation range of the light flux, the light intensity of the reflected light flux from the measured object increases, and this reflected light flux is appropriately adjusted. Can be detected. As a result, the distance measurement device according to the present invention enables highly accurate distance measurement. When light is incident on the central portion of the object to be measured whose outer shape is a curved surface, the light is substantially specularly reflected.
Even if light near the optical axis of the light beam (which has a lower light intensity than the peripheral portion of the light beam) enters the central portion of the object to be measured, the light intensity of the reflected light beam becomes an intensity necessary for detection.

Further, it is preferable that the light intensity correcting means includes an aspheric lens part and a cylindrical lens part. Since the light intensity correcting means includes the aspherical lens portion and the cylindrical lens portion, light near the optical axis of the light beam output from the light source spreads toward the peripheral portion of the light beam. Accordingly, a light intensity correcting means capable of increasing the light intensity at the peripheral portion of the light beam at a position separated by a predetermined distance from the light intensity near the optical axis of the light beam is a combination of an aspherical lens portion and a cylindrical lens portion. It can be realized with a simple configuration.

An object detecting device according to the present invention is an object detecting device provided with the above distance measuring device, wherein a plurality of light projecting optical systems are arranged in a direction intersecting the optical axis of the light beam. It is characterized by:

In the object detecting apparatus according to the present invention, when an object to be measured having a curved outer shape enters a detection zone constituted by light beams output from a plurality of light projecting optical systems arranged in parallel. Also, highly accurate distance measurement can be performed, and the detection accuracy of the measurement target object can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a distance measuring apparatus according to the present invention will be described below in detail with reference to the drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference symbols, without redundant description.

First, the configuration of a distance measuring device according to an embodiment of the present invention will be described with reference to FIG. FIG.
It is a block diagram showing the composition of the distance measuring device concerning this embodiment. The distance measuring device 1 includes a light projecting optical system 11 for irradiating a light beam as measurement light to the measured object T, a detection optical system 21 for detecting a reflected light beam reflected by the measured object T, And a signal processing system 31 for processing various electric signals input to and output from the light projecting optical system 11 and the detection optical system 21.

The light projecting optical system 11 has a light source 12 and a light projecting lens (collimating lens) 13 as light intensity correcting means. The light source 12 is a laser diode (LD) that generates and outputs a light beam in accordance with a drive signal input from a laser diode drive circuit (LD drive circuit) 33. The light intensity distribution of the light beam output from the light source (hereinafter, referred to as LD) 12 is a Gaussian distribution (the light intensity near the optical axis of the light beam is higher than the light intensity around the light beam). The light projecting lens 13 emits the light beam output from the LD 12 toward the object T to be measured, and corrects the light intensity distribution of the light beam output from the LD 12.
At a position away from the light projecting lens 13 by a predetermined distance, L
The light intensity at the periphery of the light beam is made higher than the light intensity near the optical axis of the light beam output from D12. In the present embodiment, the light projection lens 13 has a ratio of the light intensity near the optical axis of the light beam to the light intensity at the periphery of the light beam of about 1: 2 at a position about 5 m away from the light projection lens 13. Is designed to be

Next, the configuration of the light projecting lens 13 will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the light projecting lens 13. 2A is a top view, FIG. 2B is a view from the emission side, FIG. 2C is a bottom view, and FIG. 2D is a view from the emission side. The light projecting lens 13 includes an aspherical lens portion 14 and a cylindrical lens portion 15, and these aspherical lens portion 14 and cylindrical lens portion 15 are integrally formed. The light projecting lens 13 is disposed in a state where the aspherical lens portion 14 is located on the incident (LD12) side of the light projecting lens 13 and the cylindrical lens portion 15 is located on the emitting (measurement object T) side. ing. The cylindrical lens portion 15
The emission surface is concave in a semi-cylindrical shape. In addition, the floodlight lens 1
3 is a projection lens 13 which is a cylindrical lens portion 15.
May be disposed with the aspherical lens portion 14 positioned on the emission side.

The light beam output from the LD 12 is incident on the light projecting lens 13 and the aspherical lens portion 1 of the light projecting lens 13
4 makes it parallel light. The width of the collimated light beam is
It is set to about 50 mm. And the floodlight lens 1
By the third cylindrical lens portion 15, light near the optical axis of the light beam spreads toward the peripheral portion of the light beam. As a result, as shown in FIG. 3, the light intensity distribution of the light beam output from the LD 12 is higher than the light intensity near the optical axis of the light beam from the Gaussian distribution. become.

As shown in FIG. 4, the beam shape of the light beam emitted from the light projecting lens 13 has a substantially rectangular shape when viewed in a plane perpendicular to the optical axis L of the light beam. Further, as shown in the figure, the light intensity distribution along two straight lines passing through the optical axis L of the light beam and orthogonal to each other shows that the light intensity at the peripheral portion of the light beam is lower than the light intensity near the optical axis L of the light beam. It has a high distribution. The ratio of the light intensity near the optical axis L of the light beam to the light intensity at the peripheral portion of the light beam is about 1: 2 as described above.

Instead of using the light projecting lens 13 shown in FIG. 2, the light projecting lens 1 shown in FIGS.
6, 18 may be used. FIGS. 5 and 6 are views showing an example of the light projecting lenses 16 and 18 as in FIG. FIG. 2A is a top view, FIG. 2B is a view from the emission side, and FIG. 1C is a bottom view. Floodlight lens 16 shown in FIG.
Includes an aspheric lens portion 14 and a cylindrical aspheric lens portion 17 as shown. This floodlight lens 16
Is disposed with the aspherical lens portion 14 positioned on the incident side of the light projecting lens 13 and the cylindrical aspherical lens portion 17 positioned on the output side. The light projecting lens 18 shown in FIG. 6 includes an aspheric lens part 14 and a roof prism part 19. The light projecting lens 13 is disposed in a state where the aspheric lens part 14 is located on the incident side of the light projecting lens 13 and the roof type prism part 19 is located on the exit side.

Referring back to FIG. Detection optical system 21
Includes a light receiving lens 22 and a photodetector 23.
The light receiving lens 22 causes the reflected light flux reflected from the measurement target object T and returned from the light flux emitted through the light projecting lens 13 to enter the photodetector 23. The photodetector 23 is a photodiode (PD) that outputs a light-receiving signal, which has been photoelectrically converted according to the incident reflected light flux, to the amplifier 34.

The signal processing system 31 includes a pulse generation circuit 32
, An LD drive circuit 33, an amplifier 34, a comparator 35, a clock generation circuit 36, a time difference measurement circuit 37
And a distance output unit 38. Pulse generation circuit 3
Numeral 2 generates a pulse signal having a predetermined cycle and outputs the pulse signal to the LD drive circuit 33 and the time difference measurement circuit 37.
The LD drive circuit 33 operates with a pulse signal input from the pulse generation circuit 32 as a lighting trigger, and outputs a drive signal to the LD 12.

The amplifier 34 amplifies the received light signal input from the photodetector (hereinafter referred to as PD) 23. The amplified received light signal is output to the comparator 35 as an analog output signal. The comparator 35 converts an analog output signal from the amplifier 34 into a digital rectangular wave light receiving pulse signal, and outputs the converted light receiving signal to the time difference measuring circuit 37.

The time difference measuring circuit 37 includes a pulse generating circuit 3
Based on the pulse signal from the second and the light-receiving pulse signal from the comparator 35, the time difference between the light-projecting timing of the light beam from the LD 12 and the light-receiving (detection) timing of the reflected light beam at the PD 23, that is, the light beam output from the LD 12 The time until the reflected light flux is reflected by the measured object T and enters the PD 23 (the reciprocating flight time of the light flux) is measured. The clock signal from the clock generation circuit 36 is input to the time difference measurement circuit 37, and the time difference measurement circuit 37 changes the input timing of the pulse signal (for example, the rising timing of the pulse signal) to the input timing of the light receiving pulse signal (for example, By counting the clock signal up to the rising timing of the light receiving pulse signal) and multiplying the counted number of clock signals by the period of the clock signal,
The reciprocating flight time of the light beam is calculated and measured.

The reciprocating flight time of the light beam calculated and measured by the time difference measuring circuit 37 is used as time information as a distance output unit 38.
Is output to The distance output unit 38 includes a time difference measurement circuit 37
The distance from the distance measuring device 1 to the object to be measured T is calculated based on the time information from, and is output as distance information.

As described above, in the distance measuring device 1 according to the present embodiment, since the light projecting optical system 11 has the light projecting lens 13, the light flux output from the LD 12 and radiated to the object T to be measured. The light intensity distribution is such that the light intensity at the periphery of the light beam is higher than the light intensity near the optical axis of the light beam. Accordingly, for example, as shown in FIG. 3, when light around the luminous flux is incident on the end of the measured object T having a curved outer surface such as a cylinder or a columnar shape, the measured object The light intensity of the light beam reflected from the end of T is higher than the light intensity distribution of the light beam output from the light source, which is Gaussian distribution or flattened. Therefore, the light intensity of the reflected light beam from the measured object T is high even when the end of the measured object T having a curved outer shape slightly enters the irradiation range (detection area) of the light beam. That is, an amount of received light necessary for detecting the reflected light beam at the PD 23 (detection optical system 21) is obtained, and the reflected light beam can be appropriately detected at the PD 23 (detection optical system 21). As a result, according to the distance measurement device 1 of the present embodiment, highly accurate distance measurement can be performed. When light is incident on the central portion of the object T to be measured having a curved outer surface, the light is substantially specularly reflected. Therefore, for example, light near the optical axis of the light flux (light intensity is higher than that of the peripheral portion of the light flux). (Low) is incident on the center of the object T to be measured, the light intensity of the reflected light flux is an intensity necessary for detection.

Incidentally, as a technique for increasing the light intensity of the reflected light beam, it is conceivable to increase the output of the LD 12. By increasing the output of the LD 12, the light intensity not only in the vicinity of the optical axis of the light beam but also in the peripheral portion is increased, and the light intensity of the light beam reflected from the end of the measured object T whose outer shape is a curved surface is also increased. As described above, increasing the output of the LD 12 causes the life of the LD 12 to be shortened. Also,
Lasers are classified into classes such as 1, 2, 3A, 3B and 4 in the Japanese Industrial Standards (JIS) for safety. In order to obtain a sufficient amount of received light necessary for detecting a reflected light beam, a class 3B is required. It is necessary to use about LD12,
Problems arise in terms of security. However, according to the distance measuring device 1 according to the present embodiment, even when the LD 12 having an output of about class 1 is used, the reflected light beam can be appropriately detected by the PD 23 (detection optical system 21).
There is no problem of early deterioration, safety, etc. of the LD 12. Further, it is possible to reduce costs such as a reduction in the cost of the LD 12 itself and a reduction in running cost due to a reduction in power consumption.

The light projecting lens 13 includes an aspherical lens portion 14 and a cylindrical lens portion 15 so that light near the optical axis of the light beam output from the LD 12 spreads toward the peripheral portion of the light beam. become. This allows
A light projecting lens 1 capable of increasing the light intensity at the periphery of a light beam at a position separated by a predetermined distance from the light intensity near the optical axis of the light beam
3 (light intensity correction means) can be realized with an extremely simple configuration of a combination of the aspherical lens portion 14 and the cylindrical lens portion 15.

Next, an object detecting device using the above-described distance measuring device 1 will be described with reference to FIGS. FIG. 7 is a schematic perspective view illustrating a configuration of the object detection device according to the embodiment of the present invention, and FIG. 8 is a light intensity distribution of a light beam output from the light projecting optical system in the object detection device according to the embodiment. FIG. Note that the object detection device shown in FIG. 7 is a vehicle detection device used for ETC and the like.

The vehicle detecting device (object detecting device) 41 is installed on the vehicle entrance side of the tollgate island 51, and the distance measuring device 1 is arranged at a predetermined interval (for example, 40 mm pitch).
(For example, 38 channels). As shown in FIG. 7, the distance measuring device 1
Are arranged side by side in a direction intersecting (for example, orthogonally) with the optical axis of the light beam emitted from the light projecting optical system 11 in the vehicle vertical direction. The vehicle detecting device 41 irradiates a light beam as the measurement light from the plurality of the distance measuring devices 1 arranged side by side in an area, and the reflected light beam is incident on the distance measuring device 1, whereby the reciprocating flight time of the light beam is measured, Based on the reciprocating flight time (time information) of this light beam, it is detected whether or not a vehicle is present.

As shown in FIG. 7, when the vehicle to be measured T is, for example, a towing vehicle, a towing rod V3 is provided between the towing drive vehicle V1 and the towing vehicle V2.
Are connected by Such a tow vehicle is generally treated as one vehicle as a whole in terms of toll payment. As the tow bar V3, an aluminum or iron cylindrical pipe material (having a diameter of about 40 mm) may be used.

The light intensity distribution of the light beam emitted from the light projecting optical system 11 of each distance measuring device 1 is as shown in FIG.
The light intensity at the periphery of each light beam has an intensity distribution higher than the light intensity near the optical axis of the light beam. For this reason, when the light beam is applied to the end of the tow bar V3 (cylindrical pipe material), the light intensity of the light beam reflected from the end of the tow bar V3 is Gaussian. The distribution is higher than when the distribution is flattened. Therefore, even when the end of the tow bar V3 slightly enters the detection area of the distance measuring device 1 (the irradiation range of the light beam from the light projecting optical system 11), the light intensity of the reflected light beam from the tow bar V3. And the amount of received light necessary for detecting the reflected light beam by the distance measuring device 1 is obtained, and the reflected light beam can be appropriately detected. As a result, according to the vehicle detection device 41 of the present embodiment, highly accurate distance measurement can be performed, the towing vehicle can be correctly detected as one vehicle, and the detection accuracy of the vehicle can be improved. .

The present invention is not limited to the above-described embodiment, and the light projecting lens 13 may be arranged such that the light intensity distribution of the luminous flux is smaller than the light intensity near the optical axis at a position at a predetermined distance from the light projecting lens 13. The configuration is not limited to the above-described configuration as long as the light intensity distribution in the peripheral portion is increased. The value of the “predetermined distance” described above is appropriately set in consideration of the detection range of the distance measuring device 1.

The distance measuring device according to the present invention can be applied to an object detecting device other than the above-described vehicle detecting device. And the object detection device according to the present invention
It is suitable for detecting an object to be measured having a curved surface portion.

The distance measuring device according to the present embodiment is based on the time from when the light beam emitted from the light projecting optical system is reflected by the object to be measured and returns until the reflected light beam is detected by the detection optical system. Although it is configured to measure the distance, the object to be measured is not limited to this, and based on the phase difference between the light beam emitted from the light projecting optical system and the reflected light beam detected by the detection optical system. It may be configured to measure the distance to.

[0034]

As described above in detail, according to the distance measuring device and the object detecting device of the present invention, the reflected light beam from the object to be measured can be reliably detected, and a highly accurate distance measurement can be performed. It is possible to provide a distance measurement device and an object detection device that can be used.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a light projecting lens included in the distance measuring device according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a light intensity distribution of a light beam output from a light projecting optical system in the distance measuring device according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram illustrating a light intensity distribution of a light beam output from a light projecting optical system in the distance measuring device according to the embodiment of the present invention.

FIG. 5 is a diagram showing an example of a light projecting lens included in the distance measuring device according to the embodiment of the present invention.

FIG. 6 is a diagram showing an example of a light projecting lens included in the distance measuring device according to the embodiment of the present invention.

FIG. 7 is a schematic perspective view illustrating a configuration of an object detection device according to an embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a light intensity distribution of a light beam output from a light projecting optical system in the object detection device according to the embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Distance measuring device, 11 ... Emission optical system, 12 ... Light source (L
D), 13: Projection lens, 14: Aspheric lens part, 1
5: cylindrical lens portion, 21: detection optical system, 2
DESCRIPTION OF SYMBOLS 3 ... Photodetector (PD), 31 ... Signal processing system, 37 ... Time difference measurement circuit, 38 ... Distance output part, 41 ... Vehicle detection device,
T: object to be measured, V1: towing drive vehicle, V2: towing truck, V3: towing rod.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Go Ohta, 1126-1, Nomachi, Hamamatsu City, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (72) Inventor Hiroki Shimano 1, 1261, Nomachi, Hamamatsu City, Shizuoka Prefecture (72) Inventor Hironori Totsuka 1126 No. 1-cho, Ichino-cho, Hamamatsu-shi, Shizuoka Prefecture F-term (reference) 2F112 AD01 BA07 CA20 DA06 DA32 EA05 FA03 FA14 GA05 5J084 AA02 AA05 AB01 AD01 BA04 BA06 BA13 BA36 BB04 BB07 BB10 CA03 DA01 DA07 DA08 EA01 FA01

Claims (3)

[Claims] 1. A light projection optical system for irradiating a light beam output from a light source toward an object to be measured, and a detection optical system for detecting a light beam reflected by the object to be measured, A distance measuring device that measures a distance to the object to be measured, wherein the light projecting optical system has a light at a peripheral portion of the light beam at a position separated by a predetermined distance from a light intensity near an optical axis of the light beam. A distance measuring device comprising light intensity correction means for increasing the intensity. 2. The distance measuring apparatus according to claim 1, wherein said light intensity correcting means includes an aspheric lens part and a cylindrical lens part. 3. An object detection device comprising the distance measuring device according to claim 1 or 2, wherein a plurality of the light projecting optical systems are arranged in a direction intersecting an optical axis of the light beam. An object detection device, characterized in that: