JP2000321130A - Reflective photosensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflective photosensor in which detection reliability of an object is enhanced by arranging a plurality of light receiving elements around a light emitting element. SOLUTION: A circuit board 12 is secured in a case 1 where the upper opening of a transparent case body 1a is closed by a cover 1b and a light emitting element 2 is mounted in the center of the circuit board 12. The light emitting element 2 is mounted on the circuit board 12 while directing the optical axis 5 substantially perpendicular to the circuit board 12 and an irradiating part 7 is formed in a circular region on the cover 1b having the intersection of the circuit board 12 and the optical axis 5 as a center. A plurality of light receiving elements 4 are arranged around the light emitting element 2 on the circuit board 12. The light receiving elements 4 comprises photodiodes, or the like, arranged, at a constant pitch, on a same circle centering about the light emitting element 2. Furthermore, a barrier wall 6 is provided between the light emitting element 2 and the light receiving elements 4 in order to prevent the light emitted from the light emitting element 2 from entering directly into the light receiving element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type photo sensor.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a reflection type photosensor is formed by arranging one light emitting element 2 and one light receiving element 4 on a base frame 10 at opposing positions. The optical axis 5 of the light emitted from the light emitting element 2 is directed obliquely upward, and when the object 3 is present on the optical axis 5, the reflected light from the object 3 is detected by the light receiving element 4, The presence or absence of the detection target 3 can be detected by the generation of a photocurrent in the light receiving element 4.

[0003]

However, in the above-mentioned prior art, the reflected beam of the light emitted from the object 3 is projected onto the corresponding light receiving element 4, so that when the object 3 is small. When the object 3 is deviated from the optical axis 5 or when the reflection surface of the object 3 is irregularly reflected, the amount of light projected on the light receiving element 4 is reduced or reduced, and the detection of the object 3 is performed. There is a drawback that you can not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks, and has as its object to provide a reflection type photosensor having high detection reliability of an object to be detected.

[0005]

According to the present invention, it is an object of the present invention to irradiate light emitted from a light emitting element 2 housed in a case 1 to an object 3 and reflect light reflected from the object 3 to the case 3. 1
A reflection-type photosensor for detecting the presence or absence of the object to be detected 3 by detecting the presence or absence of the detection target 3 by detecting the presence or absence of the object 3 to be detected. Is achieved by

In the reflection type photosensor, a plurality of light receiving elements 4, 4... Correspond to one light emitting element 2, and each light receiving element 4 is arranged so as to surround the light emitting element 2. 4 has the following advantages over a conventional reflection type photosensor in which the light emitting elements 2 correspond one to one. That is,
As shown in FIG. 4, the conventional reflection-type photosensor is based on the premise that the light beam emitted from the light-emitting element 2 is totally reflected by the detection target 3 and supplied to the light-receiving element 4.
Although it has a high detection capability for the reflected light from the specific reflection point 11, the reflected light at the point 11 'deviated from the reflection point 11 suddenly combines with the directivity of the light receiving element 4 side. The amount of light received by the light receiving element 4 decreases. For this reason, when the detected object 3 is relatively small, the detected object 3
In the case of a slight departure from 1 or a rising surface corresponding to the reflection point 11 and a change in the reflection angle, the amount of light received by the light receiving element 4 is sharply reduced and the detection reliability is lowered. According to this, the extraordinary reflected light from the detection target 3 can be received by the other light receiving elements 4, so that the determination accuracy is improved. Further, the reflection type photosensor according to the present invention can obtain high determination accuracy for the same reason even when the reflection surface of the detection target 3 is an irregular reflection surface.

Further, when a light emitting element 2 having a directional characteristic that is as gentle as possible is used, the range in which light can be received by the light receiving element 4 is widened, so that the determination accuracy can be further improved. . In addition, such a configuration has the following advantages. That is, the light emitting element 2
In the conventional example in which the light receiving element 4 and the light receiving element 4 correspond to each other, the light emitting element 2 and the optical axis 5 of the light receiving element 4 are determined in order to increase the amount of light received from the ideal reflection point 11 as much as possible. The optical axis 5 of the light emitting element 2 greatly varies in the manufacturing process, especially in the process of mounting the cap lens, and the production yield is deteriorated. Costs are reduced. Further, in the present invention in which scattered light or the like is also used as detection light, a relatively gentle change occurs without a large difference in the amount of received light at the time of detection of the detection target 3 as compared with the above-described conventional example. Therefore, it is possible to adopt a circuit configuration in which only the threshold value for detection is strictly detected without considering the saturation current or the like, so that the circuit design is easy and the reliability of the circuit can be improved.

On the other hand, in the present invention, since the influence of disturbance light is greater than in the conventional example in which a sharp change in the detection current is detected at the detection position, the light emitting element 2 is located between the light receiving element 4 and the light emitting element 2. It is desirable to arrange a partition 6 for preventing direct irradiation of the light receiving element 4 by the light emitting element 4, in which case the partition 6 does not need to completely surround the periphery of the light receiving element 4, and the light emitted from the light emitting element 2 is directly received. It is sufficient to dispose it only at a position where it does not reach the element 4. In addition, it is sufficient to provide an opening for irradiating the irradiation light from the light emitting element 2 to the detection target 3 in the ceiling portion of the case 1, but only the passage of the wavelength light near the wavelength band of the emission light is allowed. When the irradiating section 7 formed of a filter material is formed, disturbance light included in the reflected light from the detection target 3 can be blocked, so that the detection accuracy can be improved and the optical path is mechanical. This also helps to prevent the small detection object 3 from falling into the case 1. Further, when a cylindrical light guide section 8 is formed on the back surface of the irradiation section 7 to surround the light emitting element 2, the emitted light deviated from the optical axis 5 is guided to the irradiation section 7 via the light guide section 8. Therefore, the loss of light amount can be reduced. If a diameter-enlarging portion 9 composed of a conical surface whose diameter gradually increases as the outer peripheral wall approaches the surface is provided at the boundary between the light-guiding portion 8 and the irradiation portion 7,
The effective measurable area can be increased because the light reflected on the inner peripheral wall and the outer peripheral wall and transmitted to the surface side is emitted from the surface with a predetermined spread.

[0009]

FIG. 1 shows an embodiment of the present invention. The circuit board 12 is fixed in the case 1 in which the upper opening of the opaque case body 1a is closed by the lid 1b, and the light emitting element 2 is mounted in the center of the circuit board 12. A signal line for detection output and a connector 13 for power supply are mounted on the circuit board 12. A light emitting diode can be used as the light emitting element 2. In this embodiment, a red light emitting diode having a wavelength at which the radiation intensity peaks is about 600 to 700 nm, or a wavelength of 900 nm to 9 nm.
An infrared light emitting diode of about 50 nm is used. Further, in order to detect the presence or absence of the small object 3 with high accuracy, the directional characteristics of the emitted light are more likely to be as shown by a solid line in FIG. Desirably, the lens has a gentle directional characteristic, and the cap lens covering the light emitting portion is also desirably manufactured so as to provide the directional characteristic described above.

The light emitting element 2 is mounted on the circuit board 12 so that the optical axis 5 is substantially perpendicular to the circuit board 12, and the lid 1b is provided with the center of the intersection with the optical axis 5 of the light emitting element 2 as the center. The irradiation unit 7 is formed in a circular region to be formed. The irradiation unit 7 is formed of a filter material that allows only light having a wavelength near the wavelength band of light emitted from the light emitting element 2 to pass so that disturbance light other than light reflected from the object 3 is not introduced into the case 1. When an infrared light emitting diode is used as the light emitting element 2 formed, an infrared transmitting filter is used. In this embodiment, the entirety of the lid 1b is formed of the above-mentioned filter material, and the central portion of the lid 1b is made into a mirror-like shape to form the irradiation section 7. The irradiating section 7 is provided on the general surface 1c of the lid 1b.
It is formed in a more protruding shape, and, for example, when mounted on a box or the like, consideration is given so that only the irradiation unit 7 can be exposed from the opening 14 a of the housing 14.

A light guide section 8 is integrally formed on the back surface of the irradiation section 7. The light guide section 8 has a cylindrical shape surrounding the periphery of the light emitting element 2, and the light emitted to the side of the emitted light is introduced into the light guide section 8, then reflected on the inner and outer peripheral surfaces, and is reflected on the surface of the irradiation section 7. The light is guided to the section and is irradiated on the detection target 3. At the upper end of the light guide 8, there is provided an enlarged diameter portion 9 having a conical surface whose diameter gradually increases as the outer peripheral wall approaches the surface. The irradiation unit 7 has a predetermined angle θ
Irradiated from the surface.

A plurality (four in the illustrated example) of light receiving elements 4 are arranged on the circuit board 12 so as to surround the light emitting elements 2. As the light receiving elements 4, a photodiode or a phototransistor can be used, and the respective light receiving elements 4 are arranged at the same pitch on the same circumference around the light emitting element 2.

Further, a partition 6 is provided between the light emitting element 2 and the light receiving element 4. The partition 6 is for preventing light emitted from the light emitting element 2 from directly entering the light receiving element 4, and is formed of an opaque body or prohibits passage of light having a wavelength near the wavelength band of the emitted light. A filter material can be used, and the light emitting element 2 side can be used as a reflection surface. In this embodiment, the partition 6 is integrally formed so as to protrude from the bottom of the case body 1a.
Is extended to a position surrounding the light guide section 8 from the outside through the partition wall insertion hole 12a established in the above. Remaining portion 12b connecting the mounting area of light emitting element 2 of circuit board 12 and the surrounding area
The partition 6 is formed in the shape of a leg that is discretely arranged at a constant interval on the same circumference centering on the light-emitting element 2 in order to secure the circuit board 12 on the circuit board 12. The thickness of the light guide section 8 and the enlarged diameter section 9 is such that the reflection efficiency at the outer wall of the light guide section 8 in the circumferential direction is affected by the partition walls 6 arranged discretely on the outer wall of the light guide section 8. It is determined experimentally so that the light periodically changes and the projected light from the surface of the irradiation unit 7 is not striped by the light guided by the light guide unit 8.

Therefore, in this embodiment, when the light emitting element 2 emits light, the emitted light is projected while being refracted in the light guide section 8 or directly from the surface of the irradiation section 7 as shown in FIG. When the object 3 is present in the irradiation area, the light is reflected by the object 3 and enters the light receiving element 4. As shown in FIG. 2, the respective light receiving elements 4 are connected in parallel, and the total current iT is supplied to the output adjustment unit 15. The output adjustment unit 15 is configured as shown in FIG.
As shown in FIG. 1, a first-stage DC amplifier circuit 16 using an operational amplifier, a noise cut circuit 1 using a low-pass filter
7. The signal voltage amplified by the first-stage DC amplifier circuit 16 can be constituted by a second-stage amplifier circuit 18 using an operational amplifier and a comparator 19. The binary signal is input to the two-stage amplifier circuit 18 and is extracted from the output terminal as binary information having the reference potential VREF as a threshold by the comparator 19, and the presence or absence of the detection target is determined based on the binary information.

[0015]

As is apparent from the above description, according to the present invention, a relatively small object can be detected with high accuracy.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing the present invention, wherein FIG. 1A is a plan view showing the inside of a case with a cover removed, and FIG. 1B is a view taken along line 1B-1B of FIG. 1A with the cover attached. It is sectional drawing.

FIG. 2 is a circuit diagram of an output adjustment unit.

FIG. 3 is a diagram showing directivity characteristics of a light emitting element.

FIG. 4 is a diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Light emitting element 3 Detected object 4 Light receiving element 5 Optical axis 6 Partition wall 7 Irradiation part 8 Light guide part 9 Large diameter part

Claims (5)

[Claims] 1. A reflection device for irradiating a detection object with light emitted from a light emitting element housed in a case and detecting light reflected from the detection object by a light receiving element in the case to detect the presence or absence of the detection object. A reflective photosensor, wherein a plurality of the light receiving elements are arranged around a light emitting element. 2. The reflection type photosensor according to claim 1, wherein said light emitting element has a directional characteristic as gentle as possible, and the optical axis is directed substantially vertically. 3. The reflection type photosensor according to claim 1, wherein a partition for preventing the light emitting element from directly irradiating the light receiving element is disposed between the light receiving element and the light emitting element. 4. A ceiling portion of the case includes an irradiating portion formed of a filter material that allows only light having a wavelength in the vicinity of a wavelength band of emitted light, and a partition and a light emitting element are provided on a back surface of the irradiating portion. 4. The reflection type photosensor according to claim 2, wherein a cylindrical light guide section surrounding the light emitting element from the side is formed integrally with the light guide element. 5. A reflection type photosensor according to claim 4, wherein a diameter-enlarging portion comprising a conical surface whose diameter gradually increases as the outer peripheral wall approaches the surface is provided at a boundary between said light guide portion and said irradiation portion.