JPH07301519A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To eliminate the influence of stray light generated at the window glass section of a distance measuring instrument. CONSTITUTION:A light projecting window 2 through which a light beam 8 is emitted is inclined against the vertical plane of the light beam 8 by a prescribed angle theta. In addition, the stray light 8A reflected by the window 2 is absorbed by means of a light shielding material 10 in a case 1. A part of the light reflected from an object 9 to be measured is reflected by the window 2, but the reflected light is not made incident on a light receiving area Rd. Therefore, influence of stray light can be eliminated.

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 optically measuring a distance to an object by using a triangulation method.

[0002]

2. Description of the Related Art Conventionally, as a distance measuring device using a triangulation method, light is applied to an object to be measured, and an image of scattered light is formed on a light receiving element such as a position detecting element by tilting the light beam at a predetermined angle. , A distance measuring device is used to measure the distance according to the position of the image. In such a distance measuring device, a part of the case is provided with a window for irradiating a light projection beam and receiving scattered light. This window is made of flat window glass or the like in order to facilitate cleaning of dust and the like.

[0003]

However, in such a conventional optical distance measuring device, in addition to the intended light as described below, a normal distance is caused by the following stray light emitted to the light receiving element or the object to be measured. May disturb measurement. The stray light is the light from the light projection lens that is reflected and scattered by the window and directly enters the light receiving element. The stray light that the light from the projection lens is reflected / scattered by the window, is reflected / scattered again by the member of the projection part such as the projection lens, and is irradiated to the measurement object. The stray light that is reflected from the window by the reflected light of the light that has passed through the window from the light projection lens and that has been irradiated to the measurement object, and then irradiates the object again. Such stray light can be reduced by applying a non-reflective coating to the window glass, but it cannot be completely removed, and there is a drawback in that the distance measurement is adversely affected.

The present invention has been made in view of such conventional problems, and an object thereof is to eliminate stray light generated by a window or the like so as not to be affected by distance measurement.

[0005]

According to a first aspect of the present invention, a light projecting element for generating light and irradiating an object with a light projecting beam, and light reflected from an object to be measured are received through a light receiving lens. A distance measuring device comprising a position detection type light receiving element and a signal processing means for detecting a distance to a measuring object based on an output of the light receiving element, wherein the projection beam and scattered light from the measuring object. It is placed at a position that allows the light to pass through, tilted from a plane perpendicular to the projected beam, and the window material that forms part of the case and the position where the projected beam is directly reflected by the window material to attenuate the reflected light. And a light attenuating means for causing the light attenuating means.

The invention according to claim 2 of the present application is a position detecting type light receiving element for receiving light reflected from the object to be measured through a light receiving lens, and a light projecting element for generating light and irradiating an object with a projection beam. And a signal processing means for detecting the distance to the object to be measured based on the output of the light receiving element, wherein the distance measuring device comprises a plane perpendicular to the projected beam at a position where the projected beam is transmitted. A light-projecting window member that is tilted and forms a part of the case, and a light-receiving window that forms a part of the case and is positioned perpendicular to the projection beam at a position that allows scattered light from the measurement object to pass through. The window member, a light attenuating unit arranged at a position where the light projection beam is directly reflected by the light projecting window member, for attenuating the reflected light, and the case surface provided between the light projecting window member and the light receiving window member And a non-glossy member That.

The invention according to claim 3 of the present application is a position detecting type light receiving element for receiving a reflected light from an object to be measured through a light receiving lens, and a light projecting element for generating light and irradiating an object with a projection beam. And a signal processing means for detecting the distance to the object to be measured based on the output of the light receiving element, wherein the distance measuring device comprises a plane perpendicular to the projected beam at a position where the projected beam is transmitted. The projection window material that is placed at an angle and forms a part of the case, and the position that allows scattered light from the measurement object to pass through, tilts in the direction opposite to the tilt of the projection window material with respect to the projection beam. And a light receiving window member disposed at a position where the projection beam is directly reflected by the light projecting window member and attenuating the reflected light, and the light projecting window member and the light receiving window member. And a non-glossy member provided on the surface of the case between It is intended to.

[0008]

According to the present invention having such characteristics, the light emitted from the light projecting element is emitted to the object to be measured through the window member. If the measurement object is within the predetermined detection range, the scattered light is received by the light receiving element through the window member,
The position of the measuring object is detected based on the light receiving position. Here, since the window member is arranged so as to be inclined from the vertical plane of the projected beam, the directly reflected light is attenuated by the light attenuating means inside the distance measuring device and is not adversely affected as stray light. Further, the light directly reflected from the object to be measured is also reflected by the window material, but since it is incident on a position different from the light receiving visual field, it does not adversely affect as stray light.

[0009]

1 is a sectional view showing the structure of a distance measuring apparatus according to a first embodiment of the present invention, showing an optical system portion. The case 1 has a light projecting window 2 and a light receiving window 3 in a part thereof, and a window member made of window glass is provided in each case to seal the inside of the case 1. Then, the light projecting element 4 is provided in the case 1.
Is mounted toward the light projecting window 2, and a diaphragm 5 and a light projecting lens 6 are provided along the optical axis thereof. The light projecting lens 6 is arranged, for example, in a black alumite lens barrel 7, and focuses the light projecting beam 8 emitted from the light projecting element 4 through the window material of the light projecting window 2, that is, the window glass 2a. The object 9 to be measured is irradiated. A light-shielding body 10 for absorbing light is provided in the case 1 at a position adjacent to the lens barrel 7. The light shield 10 is a light absorbing unit configured by a member that not only shields light but also absorbs incident light and does not reflect it. Further, an optical system of the light receiving portion is formed on the side thereof. That is, if the measurement object 9 is irradiated with the light projection beam 8, a part of the scattered light from the measurement object 9 enters the case 1 of the distance measuring device through the window material of the light receiving window 3, that is, the window glass 3a. Then, the light is incident on the light receiving element 12 via the light receiving lens 11. Here, it is assumed that the light receiving element 12 uses a position detection element (PSD) in which the current values of the pair of output terminals are different depending on the light receiving position. Between the light projecting window 2 and the light receiving window 3 of the case 1, a non-glossy non-glossy member is used to prevent reflected light.

FIG. 2 is a block diagram showing the overall configuration of the distance measuring device. As shown in the figure, the light projecting element 4 is pulse-driven by the drive circuit 21, and the object to be measured 9
The scattered light from is output as a current signal to both ends of the light receiving element 12. This signal is converted into a voltage by the I / V converters 22a and 22b and output to the linearity correction circuit 23 via the preamplifier. Then, after the linearity is corrected, these outputs are divided by the division circuit 24 to obtain an output signal according to the irradiation position. This signal is output to the outside via the output circuit 25. The configuration of such a signal processing unit is the same as that of the conventional distance measuring device.

According to this structure, the light is reflected on the predetermined area of the light receiving element 12 within the range from the distance measuring device to the measuring object 9 within the range from La to Lc, and the position of the object is detected. . In this way, it is possible to measure the distance to the measuring object 9 within the range of the distances La to Lc. Since the light receiving element 12 receives scattered light slightly outside this range, Rd shown in FIG. 1 becomes a light receiving field.

Here, the light projecting window 2 is arranged not at a right angle to the light projecting axis but at a predetermined angle θ with respect to a vertical plane. Therefore, even if the projection beam 8 is reflected in the case 1 by the window glass 2a of the projection window 2 and the reflected primary stray light 8A is generated, the light is not directly reflected to the projection element 4 side. It is reflected in the case. Here, the light shield 10 is provided in the case 1.
Is provided, and this primary stray light 8A is blocked. Therefore, the influence of the primary stray light 8A can be removed without the primary stray light 8A entering the light projecting element 4 or the light receiving element 12.

A part of the light reflected by the object 9 to be measured is reflected by the window glass 2a of the light projecting window 2 to become the secondary stray light 8B. If θ is 90 °, this light is specularly reflected again and the secondary stray light 8B is received in the light receiving field Rd of the measuring object 9.
Irradiate the inside. However, since θ is set to an angle of 90 ° or less as in the present embodiment, the secondary stray light 8B is reflected to the outside of the light receiving visual field Rd and does not enter the light receiving element 12. Further, as shown in FIG. 3, the measuring object 9 is inclined at a predetermined angle with respect to the projection beam 8, and the specularly reflected light is incident on the window glass 3a of the light receiving window 3 and is reflected to generate the secondary stray light 8B. Even if the secondary stray light 8B is incident on the outside of the light receiving field Rd and does not enter the light receiving element 12, it does not adversely affect the distance measurement.

Further, the inclination angle of the measuring object 9 is smaller than that in FIG. 3, and the specularly reflected light of the projection beam 8 may be radiated between the projection window 2 and the light receiving window 3 of the case 1. In this case, since these gaps are made of non-glossy materials, light is hardly reflected. Even if a part of the secondary stray light enters the light-receiving field, the level at which the reflected light again enters the light-receiving element can be greatly attenuated.

In this embodiment, the inclination of the light projecting window 2 is arranged so as to be inclined at a predetermined angle from the plane perpendicular to the light projecting beam, and the light receiving window 3 is a plane perpendicular to the light projecting beam. The angle is not the plane perpendicular to the projection beam 8 but the inclination θ as shown in FIG.
Alternatively, the angle α formed by the projection beam 8 and the glass 3a of the light receiving window 3'may be set to 90 ° or more. By doing so, the secondary stray light 8B is received by the light receiving region Rd.
It is possible to surely prevent the light from entering.

Next, a third embodiment of the present invention will be described. FIG. 5 is a vertical sectional view showing the configuration of the third embodiment, showing the optical system portion of the distance measuring device. In this embodiment, the same parts as those in the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, a common window 32 for projecting light and receiving light is provided in the case 31. This window does not have an inclination of 90 ° with respect to the projection beam as in the first embodiment, but has a different value, for example, θ = 72 °.
Shall be set to. The lens barrel 7 is spirally cut to prevent stray light from returning to the projection lens. Then, the primary stray light generated by the projection beam 8 being reflected by the window glass 32a is absorbed by the lens barrel 7 and does not return to the projection lens 6 or the projection element 4 side. Therefore, this lens barrel 7 serves as a light attenuating means for attenuating the reflected light. Even when the specularly reflected light of the measurement light is reflected again by the window glass 32a, the stray light 8B due to the secondary reflection can be made to enter the outside of the light receiving visual field Rd by setting θ to an appropriate value.

[0017]

As described in detail above, according to the present invention, the light beam emitted from the projection lens is attenuated by the light absorbing means in the case even if it is reflected by the window of the case.
There is no stray light. Further, even if the light reflected by the object is reflected again by the window, the secondary light reflected thereby does not enter the light receiving visual field. Therefore, it is possible to obtain an effect that an error due to stray light can be reduced despite the extremely simple configuration.

[Brief description of drawings]

FIG. 1 is a sectional view showing an optical system portion of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a distance measuring device according to a first embodiment of the present invention.

FIG. 3 is a vertical cross-sectional view showing a state in which the measuring object is tilted in the first embodiment of the present invention.

FIG. 4 is a vertical sectional view of a distance measuring device according to a second embodiment of the present invention.

FIG. 5 is a vertical sectional view of a distance measuring device according to a third embodiment of the present invention.

[Explanation of symbols]

 1,31 Case 2 Light-projecting windows 2a, 3a, 32a Window glass 3 Light-receiving window 4 Light-projecting element 5 Aperture 6 Light-projecting lens 7 Lens barrel 8 Light-projecting beam 8A Primary stray light 8B Secondary stray light 9 Object to be measured 10 Light-shielding body 11 light receiving lens 12 light receiving element 32 window

Claims (3)

[Claims] 1. A light projecting element for generating light and irradiating an object with a light projecting beam, a position detection type light receiving element for receiving reflected light from an object to be measured through a light receiving lens, and an output of the light receiving element. A signal processing means for detecting the distance to the measurement object based on the above, and a position perpendicular to the light projection beam at a position where the scattered light from the light projection beam and the measurement object is transmitted. A window member that is arranged so as to be inclined from the surface and forms a part of the case; and a light attenuating unit that is arranged at a position where the projection beam is directly reflected by the window member and attenuates the reflected light. A distance measuring device characterized by the above. 2. A light projecting element for generating light and irradiating an object with a light projecting beam, a position detection type light receiving element for receiving reflected light from an object to be measured through a light receiving lens, and an output of the light receiving element. A signal processing means for detecting the distance to the measurement object based on the above, in a distance measuring device comprising: a position for transmitting the light projection beam, the position being inclined from a plane perpendicular to the light projection beam, A light projecting window member forming a part of the case, and a light receiving window member arranged perpendicular to the light projecting beam at a position for transmitting scattered light from an object to be measured and constituting a part of the case. Provided on a case surface between the light projecting window member and the light receiving window member, and a light attenuating unit disposed at a position where the light projecting beam is directly reflected by the light projecting window member and attenuating the reflected light. And a non-glossy member Characteristic distance measuring device. 3. A light projecting element for generating light and irradiating an object with a light projecting beam, a position detection type light receiving element for receiving reflected light from an object to be measured through a light receiving lens, and an output of the light receiving element. A signal processing means for detecting the distance to the measurement object based on the above, in a distance measuring device comprising: a position for transmitting the light projection beam, the position being inclined from a plane perpendicular to the light projection beam, A light projecting window member forming a part of the case, and a position in which scattered light from the measurement object is transmitted, and is inclined in a direction opposite to the tilt of the light projecting window member with respect to the light projecting beam. A light receiving window member arranged, a light attenuating unit arranged at a position where the light projecting beam is directly reflected by the light projecting window member, for attenuating reflected light, the light projecting window member and the light receiving window A non-glossy member provided on the case surface between the materials, A distance measuring device comprising: