JPH0520988A - Photoelectric sensor - Google Patents

Abstract

PURPOSE:To improve detection accuracy for an object position without increasing the size of a sensor by providing a multiple reflection element between a light receiving lens and a light receiving element in a distance measurement type photoelectric sensor on the basis of the trigonometrical survey method. CONSTITUTION:A beam 6 from a luminous element 1 is projected to a substance 5 via a projection lens 2. Diffused reflection light from a substance surface 5a is condensed with a light receiving lens 3, and incident upon a multiple reflector 11. The light thereby repeats total reflection and, then, is introduced to a position sensor 4. According to this construction, an optical path between the lens 3 and the sensor 4 becomes relatively large, compared with a conventional optical path, and the distance resolution of a photoelectric sensor for object position detection can be improved without substantially enlarging a device. Also, detection accuracy for a substance position can be 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 photoelectric sensor based on a triangulation method.

[0002]

2. Description of the Related Art As a conventional distance measuring photoelectric sensor,
As shown in FIG. 3, there is a device which has a light emitting element 1, a light projecting lens 2, a light receiving lens 3 and a position sensor (PSD) 4 as basic elements and detects an object 5 by a triangulation method.

In this case, the light beam 6 emitted from the light emitting element 1 is condensed by the light projecting lens 2 into a minute spot on the object plane 5a, and the diffuse reflected light 7 is passed through the light receiving lens 3 to the position sensor 4 Focused on top. And position sensor
According to the principle of triangulation method, the distance L from the projection lens 2 to the detection object 5 depends on the position of the spot focused on 4
Is detected. That is, from the projection lens 2 to the detected object
The distance L up to 5 is 1, the distance between the light emitting element 1 and the light projecting lens 2 is l, the distance between the optical axis of the light projecting lens 2 and the light receiving lens 3 is D, and the light emitting element is When the distance between 1 and the position of the spot focused on the position sensor 4 is x, it is given by L = Dl / (x−D). Therefore, since x at the position of the spot focused on the position sensor 4 is detected by the position sensor 4, L can be detected.

The object 5 is displaced by ΔL and the object surface 5a
Is at the position of the chain line, the diffuse reflection light 7 on the object surface 5a is focused on the position sensor 4 via the light receiving lens 3 as shown by the chain line in the figure.

[0005]

However, in the above-mentioned conventional photoelectric sensor, when the light emitting diode (LED) is used as the light emitting element 1, the distance resolution is only 10% of the measured distance L, and There is a problem that the detection accuracy for the position is poor.

In addition, the position of the position sensor 4 is set to the light receiving lens.
If the distance is more than 3, the distance resolution is improved and the detection accuracy for the object position is increased, but there is a problem that the device becomes large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a photoelectric sensor capable of improving the distance resolution and the detection accuracy of an object position without increasing the size of the device in view of the above conventional problems. .

[0008]

A photoelectric sensor according to a first aspect of the present invention includes a light source, a light projecting lens for projecting light from the light source onto an object, and a light receiving element for collecting reflected light or diffused light from the object. In the distance measuring photoelectric sensor based on the triangulation method, which has a light-receiving lens and a light-receiving element for receiving light from the light-receiving lens, reflected light or diffused light from an object is provided between the light-receiving lens and the light-receiving element. Is provided with a multiple reflection element for multiple reflection of the light and guiding it to the light receiving element. The photoelectric sensor according to claim 2 or 3 is characterized in that a multi-reflection plate or a multi-reflection mirror including a pair of mirrors is used as the multi-reflection element.

[0009]

According to another aspect of the photoelectric sensor of the present invention, the light from the light source is projected onto the object through the light projecting lens, and the reflected light or diffused light from the object is received through the light receiving lens. For example, multiple reflection is performed by a multiple reflection plate or a multiple reflection mirror including a pair of mirrors, and the light is guided to the light receiving element.
As a result, the optical path length between the light-receiving lens and the light-receiving element can be increased, which is substantially equivalent to the distance between the light-receiving element and the conventional one. Therefore, it is possible to improve the detection accuracy for the object position without increasing the size of the photoelectric sensor.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a simplified block diagram showing an embodiment of a photoelectric sensor according to the embodiment of the present invention. In the figure,
The same reference numerals are used for the same or corresponding parts as 3. 1, a photoelectric sensor of the present invention comprises a light emitting element 1 as a light source of the present invention, a light projecting lens 2, a light receiving lens 3,
The position sensor 4 as the light receiving element of the present invention.

The multiple reflection plate 11 is arranged between the light receiving lens 3 and the position sensor 4. Further, a hologram element 12 is formed on the incident surface of the light from the light receiving lens 3 of the multiple reflection plate 11, and a hologram element 13 is formed on the emission surface of the multiple reflection plate 11 to the position sensor 4. ing. This multiple reflection plate 11 is a hologram element 1
Light from the light-receiving lens 3, that is, diffuse reflected light (diffused light or reflected light) on the object surface 5a is input from 2, and the diffuse reflected light 7 is repeatedly totally reflected in the multiple reflection plate 11 (multiplexed). The hologram element 13 is caused to output the light (reflected) and the light is guided (condensed) to the position sensor 4.

With such a structure, the light beam 6 from the light emitting element 1 is projected onto the object 5 through the light projecting lens 2. Diffuse reflected light 7 from the object surface 5a is condensed by the light-receiving lens 3, enters the multiple reflection plate 11, and is repeatedly totally reflected (multiple reflection) in the multiple reflection plate 11 as shown in FIG. It is guided to the position sensor 4.

By using the multiple reflection plate 11 as described above, the optical path length between the light-receiving lens 3 and the position sensor 4 can be made larger than in the conventional case, that is, compared with the case where the multiple reflection plate 11 is not provided, and therefore, This means that the distance between the light-receiving lens 3 and the position sensor 4 is substantially separated from the conventional one. Therefore, the distance resolution of the object position detection by the photoelectric sensor can be improved as compared with the related art without increasing the size of the device (photoelectric sensor) as compared with the related art, and the detection accuracy for the object position can be increased.

Further, in FIG. 3, when the distance (distance) D between the optical axis of the light projecting lens 2 and the optical axis of the light receiving lens 3 is made small in order to reduce the size of the photoelectric sensor as a whole, it is left as it is. The distance resolution will deteriorate. On the other hand, in the present invention, the optical axis of the light projecting lens 2 and the light receiving lens 2
Even when the distance (interval) D between the optical axis 3 and the photoelectric sensor is reduced to reduce the size of the photoelectric sensor as a whole, the multiple reflection plate 11 can be used to increase the optical path length without taking up space. Therefore, the distance resolution by the photoelectric sensor can be made substantially equal to or higher than the conventional one. In addition,
Light propagates through the multiple reflection plate 11 by utilizing the total reflection phenomenon, so that the loss is extremely low.

FIG. 2 is a simplified block diagram showing another embodiment of the present invention. In the figure, the same or corresponding parts as those in FIGS. 1 and 3 are designated by the same reference numerals. In FIG. 2, a multiple reflection mirror 14 including a pair of reflection mirrors as a multiple reflection element of the present invention is used in place of the multiple reflection plate 11 of FIG. 1, and other configurations are the same as in FIG. .
The multiple reflection mirror 14 is provided with reflection mirrors 17 and 18 mounted inside two transparent plates 15 and 16 which are arranged in parallel and opposed to each other so as to perform multiple reflection. In the multiple reflection mirror 14, the diffuse reflection light 7 on the object surface 5a
Is input to the multiple reflection mirror 14 via the light receiving lens 3, and after multiple reflection, can be output to the position sensor 4,
The positions of the reflection mirror 17 and the reflection mirror 18 are shifted.

When detecting the object 5 at a short distance, the multiple reflection mirror 14 for the diffuse reflection light 7 from the object 5a.
Since the angle of incidence on the multi-reflection mirror 14 is increased (increased) by inserting (interposing) a prism between the light-receiving lens 3 and the transparent plate 15 of the multi-reflection mirror 14.
The optical path may be bent so that the angle of incidence on the (reflection mirror 18) is reduced. Thereby, multiple reflection can be performed by the multiple reflection mirror 14.

In FIG. 2, the multiple reflection plate 11 of FIG. 1 is replaced with a multiple reflection mirror 14, and the same operation and effect as those of FIG. 1 are obtained. Therefore, the description of the operation and the effect is omitted.

The present invention is not limited to this embodiment, and various applications and modifications are conceivable without departing from the gist of the present invention.

[0020]

As described above, according to the present invention, the following effects can be obtained. (1) Since a multiple reflection element such as a multiple reflection plate or a multiple reflection mirror consisting of a pair of mirrors is arranged between the light receiving lens and the light receiving element, the optical path length between the light receiving lens and the light receiving element is multiplexed. It can be made large as compared with the case where there is no reflective element (conventional case). Therefore, the detection accuracy for the object position can be improved without increasing the size of the device. (2) Even when the distance between the optical axis of the light projecting lens and the optical axis of the light receiving lens is made smaller than in the conventional case and the size of the device is reduced, for example, multiplex is provided between the light receiving lens and the light receiving element. By disposing a multi-reflection element such as a reflection plate or a multi-reflection mirror including a pair of mirrors, the distance resolution of the photoelectric sensor can be made substantially equal to or higher than that of the conventional one.

[Brief description of drawings]

FIG. 1 is a simplified configuration diagram showing an embodiment of a photoelectric sensor according to the present invention.

FIG. 2 is a simplified configuration diagram showing another embodiment of the present invention.

FIG. 3 is a simplified configuration diagram showing an example of a conventional photoelectric sensor.

[Explanation of symbols]

1 Light emitting element 2 Projection lens 3 Light-receiving lens 4 Position sensor 5 objects 6 light beam 7 Diffuse reflected light 11 Multiple reflector 14 Multiple reflection mirror 17, 18 Reflective mirror

Claims (3)

[Claims] 1. A light source, a light projecting lens for projecting light from the light source onto an object, a light receiving lens for collecting reflected light or diffused light from the object, and light from the light receiving lens. In a distance measuring photoelectric sensor based on a triangulation method, which has a light receiving element for receiving light, the light receiving element is provided by multiply reflecting reflected light or diffused light from the object between the light receiving lens and the light receiving element. A photoelectric sensor having a multi-reflection element for guiding to a photoelectric sensor. 2. The photoelectric sensor according to claim 1, wherein a multiple reflection plate is used as the multiple reflection element. 3. The photoelectric sensor according to claim 2, wherein a multi-reflection mirror composed of a pair of mirrors is used as the multi-reflection element.