JPH07208944A - Object detecting sensor for narrow space - Google Patents

Abstract

PURPOSE:To make it possible to detect only an object in a narrow space by a simple construction, by generating a slender projection beam by disposing a cylindrical lens in front of a light emitting element. CONSTITUTION:In the case where a cylindrical lens l and a light emitting element 2 of a small spatial extent located inside the lens are provided as a light-projecting part, the focal distance of the lens l is selected so that the half-width of the quantity of light in a direction 3 of convergence of a projection beam by the lens 1 in front of the light-projecting part by 30 cm be + or -3D/or below when the width of the lens 1 is made D. In other words, the spatial extent of the element 2 is made approximate to a point of this degree. On the other hand, the extent stretches in accordance with the directivity of the element 2 in a direction 4 in which the beam is not converged. As the result, a projection beam 5 of a slender section corresponding to an area of detection is generated. A photodetector 6 is provided in the vicinity of the position in the axial direction of the lens 1 and a construction is made so that a light obtained by reflection of the beam 5 on an object be received effectively. According to this constitution, it is detected whether a reflected light signal outputted by the photodetector 6 is of a prescribed level or above, and the existence or nonexistence of the object within the area of detection is judged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optically active type object detection sensor for an interspace for detecting only an object in the interspace.

[0002]

2. Description of the Related Art A conventional optical reflection type object detection sensor is
The light projecting unit and the light receiving unit are integrated, light is directly applied to the object to be detected, and the reflected light is detected to detect the presence or absence of the object. Therefore, the detectable range is in the range of the projected light, and it is necessary to change the shape of the projected beam according to the detection specifications.

[0003]

Now, whether or not an object is present in the narrow space 9 between the obstacle range I7 and the obstacle range II8 as shown in FIG. 2 is detected by using a reflection type optical sensor. In the case of having a light emitting element only without using a lens as a light projecting portion, the projected light spreads according to the directivity of the light emitting element, and reaches the obstacle ranges I and II. It even senses certain objects. Therefore, for example, by arranging a point light source at the focal point of the convex lens,
It is necessary to narrow down the projection beam by using the property that all the light passing through the lens is parallel. However, there is no light emitting element that serves as a strict point light source, and even in this method, the projected light is spread due to the spatial expansion of the light emitting element,
It senses objects in obstacle ranges I and II.

Further, even when a light emitting element having a small spatial spread can be used, and even if it is possible to set such that an object in an obstacle range is not sensed, if a normal convex lens is used as a lens, the light is projected. The light becomes isotropically thin, and the detectable range is only within the light beam having a circular cross section, which causes a problem that only a small part of the entire elongated interstitial region can be included in the detectable range. Conventionally, in order to detect an object in the entire narrow space, a complicated and expensive structure such as a plurality of light emitting elements, a light projecting lens, and a light projecting / receiving electric circuit accompanying them has been required.

Therefore, an object of the present invention is to provide an object detecting sensor for a narrow space which can detect only an object in the narrow space with a relatively simple structure.

[0006]

In order to achieve the above-mentioned object, the present invention provides at least one light emitting element and an elongated projection beam arranged in front of the light emitting element in an object detecting sensor for interstitial spaces. An intervening object detection sensor characterized by having a cylindrical lens to be generated and a light receiving element arranged in the vicinity of the cylindrical lens so as to receive reflected light from an object existing in the elongated projection beam To do.

[0007]

Embodiments of the present invention will now be described with reference to the drawings. First, the principle of the present invention will be described. FIG. 1 is a schematic perspective view for explaining the principle of the present invention. As shown in FIG. 1, a cylindrical lens 1 and at least one light emitting element 2 placed inside thereof are provided as a light projecting portion. When the light emitting element 2 having a small spatial spread is provided, assuming that the width of the cylindrical lens 1 is D,
By appropriately selecting the focal length of the lens, the half value width of the light amount in the direction 3 converged by the cylindrical lens 1 of the projection beam 30 cm ahead of the projection unit is set to be ± 3D or less. That is, the spatial spread of the light-emitting element is close to the "point" of this degree. On the other hand, in the direction 4 in which light is not collected, it spreads according to the directivity of the light emitting element 2. As a result, a projection beam 5 having an elongated cross section corresponding to the range to be detected is generated. A light receiving element 6 is provided near the axial position of the cylindrical lens in parallel with the light projecting portion, and the light projecting beam 5 emitted from the light emitting element 2 hits an object (not shown) and is reflected by the light receiving element 6. Is configured to effectively receive light. A determination means (not shown) detects a state in which the reflected light signal output from the light receiving element 6 is equal to or higher than a predetermined level, and a range to be detected based on the detection output (a space between the obstacle ranges). (Region) determines whether or not an object exists.

FIG. 3 is a perspective view showing a specific embodiment. In FIG. 3, a cylindrical lens 1 as a light projecting portion and five light emitting elements 2 are provided inside thereof.
As a light emitting device, the semiconductor light emitting area is 0.3 mm ×
It is as small as 0.3 mm, and the epoxy resin that covers it is 1
mm Infrared light emitting diode (wavelength peak: 880
nm) was used. The light-receiving element 6 is arranged side by side with the light-projecting portion and is arranged at an interval of 20 mm near the axial position of the cylindrical lens, as shown in FIG. Is converted to
A PIN photodiode having a wavelength sensitivity peak of 900 nm was used. Duty ratio 20 to increase the light emission output
Pulse emission was performed with a pulse width of 0: 1 and a pulse width of 5 μs. When the detection object enters the narrow area to be detected, the light projected from the light emitting element is reflected by the detection object, and a part of the reflected light is received by the light receiving element. The light receiving element converts the reflected light into an electric signal, the electric signal is amplified by an amplifier (not shown) as necessary, and a comparator (not shown) determines whether or not the electric signal is above a predetermined level, This output is displayed on a display, for example. The cylindrical lens 1 has a width D of 10 mm and a length of 20 mm and a focal length of 12.4 mm. The results of measuring the light intensity distribution 30 cm ahead using an optical power meter are shown by the curve 10 in FIG. 4 and the curve 11 in FIG.

In FIG. 4, the horizontal axis shows the spread of light in the direction converged by the cylindrical lens, and in FIG. 5, the horizontal axis shows the spread of light in the unfocused direction. The vertical axis represents the relative intensity distribution of the projected light. As is clear from FIG. 4, the half width of the light amount in the converged direction is ± 20 mm (that is, ± 2D),
As is apparent from FIG. 5, it is confirmed that the spread light projection beam 5 is projected so that the half-value width of the light amount in the unfocused direction is ± 180 mm. 30 cm in front
210mm x 297mm as a sensing object in
(A4 size) Using white paper, considering a part of the white paper as an object in a narrow space, a test result of a detectable range of the object is shown in a curve 12 of FIG. The detectable range in the direction in which the light is not converged is shown by the curve 13 in FIG. As is clear from FIG. 6, the width of the detectable range in the direction in which the light is converged is about 20 mm (± 10 mm) 30 cm ahead, and as is clear from FIG. 7, the direction in which the light is not converged. The width of the detectable range is 160 mm (± 8
0 mm), and it is possible to detect an object in the narrow space.

Therefore, for example, when applied to a pinch prevention sensor for a power window of an automobile, a window frame, a seat,
It can be configured to detect the presence of a person's hand or head within a width of about 2 cm near the power window and to stop the power window without sensing the person in a normal state. It is possible to prevent the risk of the head being caught in the power window.

The present invention can be applied not only to the above-mentioned monitoring for prevention of pinching for power windows of automobiles, but also to other object detection sensors for intervening spaces in fields such as industrial robots.

[0012]

As described above, according to the present invention,
A projection beam that is converged in only one direction by a projection unit having a cylindrical lens and a light emitting element that can be regarded approximately as a point light source inside thereof is used, and the projection lens is arranged in parallel with this projection unit. By arranging the light receiving element in the vicinity of the axial direction, it is possible to judge only the presence of an object existing in the elongated projection beam. Therefore, it is possible to detect an object for a gap, which is difficult with a conventional sensor, that is, "detect only an object in a gap region sandwiched by an obstacle range without detecting an object in the obstacle range". By setting the focal point of the cylindrical lens appropriately, it is possible to reduce the half-value width of the light quantity in the direction converged by the cylindrical lens of the projected beam 30 cm ahead to ± 3D or less. It is possible to set a narrow detection area. For example, as a pinch prevention sensor for automobile power windows, it is possible to detect only when a hand or head comes into a region near the power window without detecting window frames, seats, people in normal condition, etc. become.

[Brief description of drawings]

FIG. 1 is a schematic perspective view for explaining the principle of the present invention.

FIG. 2 is a perspective view for explaining a use environment in which the object detection sensor for an interval of the present invention is used.

FIG. 3 is a perspective view showing an embodiment of the present invention.

FIG. 4 is a graph showing a light intensity distribution 30 cm ahead of the emitted light in the direction in which the light is condensed by the cylindrical lens.

FIG. 5 is a schematic diagram of radiated light in the direction not focused;
It is a graph which shows the light intensity distribution in front of cm.

FIG. 6 is a graph showing an object detectable range in the direction in which light is collected.

FIG. 7 is a graph showing an object detectable range in a direction in which light is not collected.

[Explanation of symbols]

 1 Cylindrical lens 2 Light emitting element 6 Light receiving element 7 Obstacle range I 8 Obstacle range II 9 Between

Claims (3)

[Claims] 1. In the object detection sensor for interstitial spaces, at least one light emitting element and a light emitting element arranged in front of the light emitting element,
For a narrow space, characterized by having a cylindrical lens for generating an elongated projection beam and a light receiving element arranged near the cylindrical lens so as to receive reflected light from an object existing in the elongated projection beam. Object detection sensor. 2. The object detection sensor for narrow spaces according to claim 1, wherein when the width of the cylindrical lens is D, the half value width of the light amount in the direction in which the projection beam is converged 30 cm in front of the cylindrical lens is ± 3D or less. An object detection sensor for interstitial spaces, characterized by selecting a light emitting element having a size as a point light source such that 3. The interstitial object detection sensor according to claim 1, wherein the light receiving element is arranged at an axial position of the cylindrical lens.