JPH05256947A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a distance measuring apparatus for measuring the distance by the method of a laser radar and which is able to incorporate a stain detecting device within a light transmitting unit thereby to enhance the detecting sensitivity of stain. CONSTITUTION:The light to be used for measuring the distance and emitted from a laser diode 2 is condensed by a convex lens 3 and passes through a front glass 14. If a stain 141 is present on the front glass 14, the light is partially scattered backward. A condenser lens 31 adjacent to the convex lens 3 and integral with the convex lens 3 condenses the scattering light onto a photodiode 9 in a light transmitting unit 1. Accordingly, the stain 141 on tone front glass 14 can be detected. At the same time, the apparatus becomes compact and the detecting sensitivity of stain is improved.

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 irradiating an object with light and detecting reflected light from the object to measure a distance.

[0002]

2. Description of the Related Art An infrared laser beam or the like is irradiated toward an object, and the reflected light reflected by the object is received by an optical means such as a convex lens or a concave mirror to generate an infrared laser beam. A device for measuring a distance to an object by detecting a delay time from transmission to light reception is already known. For example, a device mounted on a vehicle to measure a distance to a preceding vehicle or detect an obstacle ahead. Is disclosed in JP-A-59-24278.

In a device using such optical means, in order to prevent dust, water, etc. from entering the optical system, the entire device is housed in a case in which light is transmitted and a light receiving surface is made of transparent glass. This prevents the lens and photoelectric conversion element from becoming dirty, but since the glass surface of the case is in contact with the outside air, there is always the possibility that it will become dirty due to the adhesion of dust or water droplets. Markedly reduced.

Therefore, in such a case, it is necessary to inform the user of this in advance. FIG. 4 shows this example, which is disclosed in Japanese Patent Laid-Open No. 3-30116. To explain this example, in FIG.
Reference numeral 1 is a light transmitting unit, which is a laser diode 2 which emits a laser beam, and converges the laser beam at a predetermined angle to L
_It is composed of a convex lens 3 which is sent as _t . Reference numeral 4 is a pulse generation circuit for pulse-driving the laser diode 2.

Reference numeral 5 denotes a light receiving unit, which is a convex lens 6 for collecting reflected light L _R from an object and a photodiode 7 arranged at the focal point of the convex lens 6.
It is composed of Reference numeral 8 denotes a widening circuit for widening the electric signal photoelectrically converted by the photodiode 7.

Reference numeral 9 is a photodiode for detecting dirt, and 10 is a cylindrical hood for preventing stray light from entering the photodiode 9. Reference numeral 11 denotes a widening circuit for widening the electric signal of the photodiode 9 for detecting dirt. Reference numeral 12 is an arithmetic circuit for processing the signals of the pulse generating circuit 4, the widening circuit 8 and the widening circuit 11, and further sending the signals to the display device 15 described later.

Reference numeral 13 designates a case for accommodating all of these units, and a transparent glass front glass 14 is used on the surface on which the light transmitting lens 3 and the light receiving lens 6 are arranged so as not to prevent the transmission and reception of light. To be done.

Reference numeral 15 is a display device for concretely displaying the measured distance in the form of graphs and numbers, and when the surface of the front glass 14 of the case 13 is contaminated by the contamination detection photodiode 9, the fact is indicated. Is displayed.

Next, the operation of this conventional device will be described. First, the laser diode 2 pulse-driven by the pulse generation circuit 4 emits a pulsed laser beam, which is irradiated by the convex lens 3 onto the object as the outgoing beam L _t having a predetermined angle, and the reflected beam thereof is L _R. Then, the light is focused on the photodiode 7 by the convex lens 6 and converted into an electric signal, and then amplified by the width increasing circuit 8 and sent to the arithmetic circuit 12. The arithmetic circuit 12 calculates the distance to the object based on the time difference between the pulse signal supplied to the pulse generation circuit 4 and the received signal from the amplification circuit 8.

In this case, if the front glass 14 of the case 13 is not dirty, the light sent from the light sending unit 1 passes through the front glass 14 as it is, and the light does not enter the photodiode 9 for dirt detection. The dirt detecting photodiode 9 is arranged so as to be largely inclined with respect to the optical axis of the light transmitting unit 1 so that the light emitted from the laser diode 2 and regularly reflected by the front glass 14 does not enter.

Next, the reference numeral 14 is attached to the light transmitting portion of the front glass 14.
When the stain indicated by 1 is attached, a part of the transmitted light L _t becomes scattered light at this portion, and the photodiode 9 for detecting the stain is present.
Will be incident on. Therefore, if the output signal of the photodiode 9 is widened by the widening circuit 11 and is input to the arithmetic circuit 12 so that the display device 15 is displayed that there is dirt, the front glass 14 can be displayed to the user. Can be encouraged to clean.

[0012]

Since the conventional distance measuring device is constructed as described above, the dirt detecting device consisting of the photodiode 9 and the cylindrical hood 10 must be installed outside the light transmitting unit 1. In addition, since the photodiode 9 receives the weak scattered light as it is, it is necessary to increase the amplification rate of the amplification circuit 11, and the stray light from the outside is more likely to be affected. There is a problem that stray light must be cut using the long cylindrical hood 10. Further, since the cylindrical hood 10 has a long shape, there is a problem that the mounting method is also restricted.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a distance measuring device which can incorporate a dirt detecting device in a light transmitting unit and can increase the sensitivity of dirt detecting. To aim.

[0014]

In the distance measuring apparatus of the present invention, in the apparatus, a scattered light condensing lens for condensing scattered light due to dirt on the front glass of the case into a light transmitting unit is used as a light transmitting lens. A light receiving element that is integrally formed adjacent to and that receives the condensed light.

[0015]

In the distance measuring device according to the present invention, the scattered light condensing lens disposed adjacent to the light transmitting lens condenses scattered light due to dirt on the surface of the transparent window to the light receiving element in the light transmitting unit. I can guide you. Further, the scattered light condensing lens can bend the optical path of the scattered light to dispose the light receiving element for detecting dirt in the light transmitting unit.

[0016]

【Example】

Example 1. An embodiment of the present invention will be described below. Since the principle of distance measurement is the same as that of the above-mentioned conventional apparatus, the description thereof will be omitted, and the dirt detection apparatus which is the gist of the present invention will be described.

FIG. 1 is a cross-sectional view showing the structure of a light transmitting unit according to an embodiment housed in a case, in which the light transmitting unit and the dirt detecting device are integrated. Reference numeral 1 is a light transmitting unit, 2 is a laser diode which is a light source for irradiating an object whose distance is to be measured with laser light, and 3 is light transmitting for converging the laser light at a predetermined angle and sending it out. It is a convex lens as a lens. The light sending unit 1 is composed of a laser diode 2 and a convex lens 3, the laser diode 2 is fixed to the bottom inner surface of the bottomed cylindrical metal fitting, and the convex lens is attached to the front opening of the bottomed cylindrical metal fitting.

Reference numeral 31 denotes a scattered light collecting lens for collecting scattered light due to dirt on the surface of the front glass 14 as a transparent window of the case arranged in front of the light sending unit 1 into the light sending unit 1. The convex lens has a half-moon shape in which the convex lens is divided into upper and lower parts, and the thick side is adjacent to the convex lens 3 and integrally molded with acrylic plastic or the like. 9 is a photodiode for detecting dirt,
It is arranged side by side with the laser diode 2 inside the light transmitting unit 1 so as to receive light at the condensing position of the condensing lens 31, that is, its focal position.

FIG. 2 is a plan view showing a lens plate 300 in which the convex lens 3 and the condenser lens 31 shown in FIG. 1 are integrated. 301 is a hole provided at four corners for attaching the lens plate 300 to the opening of the bottomed tubular metal fitting of the light transmitting unit 1. The other configurations except the dirt detection device and the light sending unit are the same as those in FIG.

Next, the operation of the first embodiment will be described with reference to FIG. If the front glass 14 is clean, the transmitted light L emitted from the laser diode 2 and passing through the convex lens 3
_{Although t} passes through the front glass 14 as it is, if there is dirt 141 on this surface, a part of the transmitted light L _t becomes backward scattered light at this portion.

As described above, the condensing lens 31 for condensing the scattered light due to the dirt is provided adjacent to the convex lens 3. The condensing lens 31 has a half-moon shape in which a convex lens is divided into upper and lower halves, and thus has a function of condensing scattered light due to dirt and a function of refracting incident scattered light toward the thicker side. have.

Therefore, the scattered light due to the dirt 141 becomes an optical path as shown by the dashed line in FIG. 1 by the action of the condenser lens 31, and is focused on the light receiving surface of the photodiode 9 installed in the light transmitting unit 1. Thus, if the focal length of the condenser lens 31 is previously determined, the dirt 141 on the front glass 14 can be detected by the output of the photodiode 9.

Example 2. Although the case where the spherical lens is used as the scattered light condensing lens has been described above, the scattered light condensing lens is shown as a plane and a cross section taken along the line AA in FIGS. 3A and 3B. Even if a half-moon shaped Fresnel lens 311 that is integrated adjacent to the convex lens 3 is used, the same effect as in the above embodiment can be obtained.

Example 3. Further, if it is merely to guide the scattered light into the light transmitting unit 1, the condenser lens 31 shown in FIG.
Instead of this, this part may be used as a prism.

[0025]

As described above, according to the present invention, the scattered light due to the dirt on the surface of the transparent window of the case is integrated in the light transmitting unit by the scattered light condensing lens adjacent to the light transmitting lens. Since the light is collected on the light receiving element, the dirt detection can be made highly sensitive, and the dirt detection device can be installed in the light sending unit because of the lens shape that creates the optical path in the light sending unit. There is an effect that it can be integrated and the entire device can be made compact.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a light transmitting unit portion of a distance measuring device according to an embodiment of the present invention.

FIG. 2 is a plan view of a lens of the light transmitting unit according to the embodiment.

FIG. 3 is a diagram showing a lens of a light transmitting unit according to another embodiment in a plan view and a cross section.

FIG. 4 is a diagram showing a configuration of a conventional device.

[Explanation of symbols]

 1 Light-sending unit 2 Laser diode (light-emitting element) 3 Convex lens (light-transmitting lens) 4 Pulse generation circuit 5 Light-receiving unit 6 Convex lens 7 Photodiode 9 Photodiode (light-receiving element) 12 Arithmetic circuit 13 Case 14 Front glass (transparent window) 31 Condensing lens (lens for collecting scattered light) 311 Fresnel lens (lens for collecting scattered light)

Claims (1)

[Claims] 1. A light-sending unit comprising a light-emitting element for generating light, a light-sending lens for converging the light emitted by the light-emitting element and irradiating it toward an object, and a light-sending unit for the object. A light receiving unit for receiving the reflected light and an arithmetic circuit are housed in a case having a transparent window, and the light sending unit sends the light and then the light receiving unit receives the reflected light from the object. In the distance measuring device for measuring the distance from the time to the object, the scattered light condensing lens for condensing the scattered light from the transparent window of the case in the light transmitting unit is used as the light transmitting lens. 2. A distance measuring device, characterized in that it is provided integrally with adjacent ones and provided with a light receiving element for receiving the condensed light by the scattered light condensing lens in the light transmitting unit.