JPH09139162A - Reflection type photoelectric sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection type photoelectric sensor which is hardly susceptible to the influence of a distance, an angle, surface irregularities or the like by converging light from a surface light source on the surface of a body through a light projecting lens, diffusing light from the circumference and making it to be incident thereupon. SOLUTION: Light from a light source 2 is led to the detecting region of a detection body 10 through a light projecting lens 3, and reflected light undergoing positive reflection is detected by a light receiving element 5 through a light receiving lens 4, and its detection signal is sent to a comparator 7 through an amplifier 6 to determine the existence of a body, the state of surface gloss or the like and to deliver an output from an output circuit 8. In the above-mentioned reflection type photoelectric sensor 1, a surface light source is used as the light source 2 to radiate light from the surface opposite to the light projecting lens 3. Light from the center of the light source 2 is converged on the surface of the body 10 and besides, light from the circumference is diffused so as to be incident upon the surface of the body. Therefore, the reflection type photoelectric sensor 1 is hardly susceptible to the influence of the distance change and the angle change of the detection body and also the possibility of erroneous detection due to very small irregularities can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection-type photoelectric sensor, and more particularly to a reflection-type photoelectric sensor for detecting the presence or absence of an object that regularly reflects incident light and the surface state thereof.

[0002]

2. Description of the Related Art Conventionally, as a photoelectric sensor for detecting a detection object that has a glossy surface and specularly reflects incident light, a photoelectric sensor of a condensing type that collects light on the surface of the detection object and A divergent beam type photoelectric sensor that diffuses and enters the detection object is used. 8 and 9 show a condensing beam type photoelectric sensor 100 in which light from a light projecting element 101 is incident on a detection object via a condensing lens 102. The reflected light is received by the light receiving element 104 via the light receiving lens 103, and the presence or absence of an object is detected based on the light receiving level. FIG.
0 and FIG. 11 show a diverging beam type photoelectric sensor 110, which is the same as the condensing beam type photoelectric sensor except that the light projecting lens 111 projects light onto a wide range of the object. Each of these photoelectric sensors is a specular reflection detection type sensor that detects the presence or absence of a glossy detection object. However, the condensing beam type and diverging beam type photoelectric sensors 100 and 110 have different detection characteristics depending on the variation of the object and the surface condition. That is, FIG.
As shown in (b) and FIG. 10 (b), when the allowable range of angles ± θ1 and θ2 that can be detected even when the object is tilted by a certain angle is compared, the divergence beam photoelectric sensor 110 has a larger allowable range of angles. Is wide (θ1 <θ2). In addition, the influence of distance fluctuation
As shown in FIGS. 9 (c) and 11 (c), the ratio d2 '/ d2 of the light receiving range when displaced by a constant distance is d1' /
It is smaller than d1. That is, the diverging beam type photoelectric sensor 110 is less susceptible to the influence of the distance variation, and has better characteristics. However, when the surface of the detection object has minute irregularities, the focused beam photoelectric sensor 100 can receive light within a certain range as shown in FIG. For example, as shown in FIG. 11D, if there are minute mountain-shaped irregularities, the reflected light is separated, the reflected light is not obtained at the hatched portion in the figure, and the light receiving element 10
It may not be incident on the 4th side, and there is a drawback that it cannot be detected.

[0003]

As described above, the divergent beam type and the convergent beam type have different detection characteristics, and cannot be photoelectric sensors that are not easily affected by angle fluctuations, distance fluctuations, and minute irregularities. There was a drawback.

The present invention has been made by paying attention to such a conventional problem, is not easily influenced by the distance variation and the angle variation of a detected object, and has a small possibility of erroneous detection due to minute unevenness. The object is to realize a reflective photoelectric sensor.

In addition to the above, an object of the present invention is to provide a photoelectric sensor for detecting the glossiness for detecting the gloss of an object with such a function.

[0006]

According to a first aspect of the present invention, a light source, a light projecting lens for guiding the light incident from the light source to an object detection region, and a reflected light from an object for specularly reflecting the light are received. In the reflection type photoelectric sensor, the light source emits light from a surface facing the light projecting lens, and a light receiving unit that determines the level of an object based on the level of specularly reflected light received by the light receiving unit. It is a surface light source for irradiating, and the light projecting lens focuses the light from the center of the surface light source on the surface of the detection object, and diffuses the light from the periphery of the surface light source into the detection object surface and makes it incident. It is characterized by being arranged as follows.

According to a second aspect of the present invention, a light source that emits light having a polarization component of either P-polarized light or S-polarized light, and a projection lens that guides the light incident from the light source to an object detection area, Of the reflected light from an object that specularly reflects light,
Reflection having a light receiving means for separately receiving the light of the P-polarized component and the light of the S-polarized component, and a determination means for determining the surface state of the object based on the output levels of the P-polarized component and the S-polarized component by the light receiving means. In the photoelectric sensor, the light source is a surface light source that emits light from a surface facing the light projecting lens, and the light projecting lens focuses light from the center of the surface light source on the surface of the detection object, It is arranged such that light from the periphery of the surface light source is diffused and incident on the detection object surface.

In the invention of claim 3 of the present application, the light source is
A light projecting element, and a diffusing means for diffusing the light of the light projecting element,
It is characterized by having.

In the invention of claim 4 of the present application, the light source is
It is characterized by comprising a light projecting element, a collimating lens for collimating the light of the light projecting element into parallel light, and a diffusing means provided behind the collimating lens for diffusing the parallel light.

According to the invention of claim 1 of the present application having such characteristics, light is emitted from the light source to the object detection area through the light projecting lens, and the reflected light from the detected object is received by the light receiving means. The presence or absence of an object is determined based on the received light level. At this time, if the light source is a surface light source, the light emitted from the center of the light source is focused on the surface of the detection object, and the light from the periphery is diffused and incident on the surface of the detection object. And a diffusion type photoelectric sensor. Claim 2
In the invention, the light source area is expanded to a photoelectric sensor that emits light having one of the polarization components and discriminates gloss based on whether or not the polarization component of the reflected light is preserved. In the third aspect, the light source is constituted by the light projecting element and the diffusing means for diffusing the light. In the fourth aspect, the light utilization efficiency can be improved by further providing the collimating lens.

[0011]

1 is a view showing a reflection type photoelectric sensor 1 according to a first embodiment of the present invention. As shown in the figure, the reflective photoelectric sensor 1 has a light source 2 and a light projecting lens 3, and a light receiving lens 4 and a light receiving element 5 for receiving the reflected light from an object illuminated by the light projecting lens 3. Have The output of the light receiving element 5 is output to the comparator 7 via the amplifier 6. The comparator 7 determines the presence or absence of an object at a constant threshold level, and outputs an object detection signal via the output circuit 8. Here, the distance between the light source 2 and the light projecting lens 3 and the distance from the detection lens 3 to the detection object 10 are arranged at positions where the image formation formula is satisfied. That is, assuming that the focal length of the light projecting lens is f, the distance between the light projecting lens 3 and the light source 2 is a, and the distance between the light projecting lens 3 and the detection object 10 is b, the following equation 1 / f = 1 / a + 1 / b Arrange them so that the distance is satisfied. If the light source 2 is a point light source, the above-described condensing photoelectric sensor is used. However, in the present embodiment, the light source 2 is not a point light source but a focal length f.
A relatively large surface light source is used. In this way, of the light emitted from the light source 2, the light emitted from the central portion thereof is focused on the surface of the detection object 10. Further, since the light source area of the light source 2 is large, the light emitted from the peripheral portion of the light source 2 is diffused as shown by the broken line in the figure due to coma aberration, so that it is incident on a wide range of the detection object 10. For this reason, the light emission states of both the divergent beam type condensing beam type photoelectric sensor and the condensing beam type photoelectric sensor of the conventional example described above are equal, and a photoelectric sensor having both characteristics can be obtained. That is, it is possible to obtain a photoelectric sensor that is resistant to angle fluctuations and distance fluctuations and is not easily affected by minute irregularities on the surface of the detection object. The intensity distribution at the position of the light receiving lens indicated by AA 'in FIG. 1 is as shown in FIG. 2B, and light can be received within this range.

Next, a structure for making the light source a surface light source having a relatively large light source area will be described. In order to use the light source as a surface light source, for example, as shown in FIG. 3A, a light emitting element which is considered to be a point light source, for example, a light emitting diode 11 is used as a light source, and a collimator lens 12 is provided at a predetermined position thereof. The collimator lens 12 converts the light emitted from the light emitting diode 11 into light parallel to its optical axis.
In this embodiment, the back surface of the collimator lens 12 is a flat surface, and the back surface of the collimator lens 12 is in close contact with the back surface of the collimator lens 12. Since the diffuser plate 13 diffuses parallel light, it equivalently serves as a surface light source and reduces the area of the light source.
It is possible to increase the size to. FIG. 4 shows a light trace between the enlarged light source and the detection object. Here, in order to make the figure easy to understand, it is shown that the detection object 10 is directly transmitted and is incident on the light receiving lens 4, but in reality, the light is reflected on the surface of the detection object 10 and the light receiving lens 4 and the light receiving element. Join 5 As is apparent from this figure, the light emitted from the center of the light source is focused on the surface of the detection object 10, and the reflected light is obtained by the light receiving element 5. Further, the light emitted from the periphery of the light source enters a relatively wide range of the detection object 10, and a part of the reflected light enters the light receiving element 5. Therefore, as described above, a photoelectric sensor having both characteristics of a diverging beam type and a converging beam type can be obtained. When such a diffusion plate 13 is used, the intensity distribution at the light receiving position A-A 'can be easily set within a certain range by properly selecting the curvature and shape of the light projecting lens 3, as shown in FIG. The photoelectric sensor can be made flat inside and is less likely to be affected by angle fluctuations, distance fluctuations, and minute irregularities.

FIG. 3B shows another method for diffusing light and expanding the light source area. In this example, the back surface 14a of the collimator lens 14 is embossed so that the light emitted from the collimator lens 14 is diffused. As shown in FIG. 3C, a Fresnel lens 15 is used, the light emitting diode 11 side of the Fresnel lens 15 is a convex lens, and the surface 15a of the Fresnel lens 15 on the light projecting lens 3 side is a diffraction grating. By doing so, the light is once made parallel by these actions, and the Fresnel lens 15
The diffused light can be emitted from the entire surface. Therefore, in either case, the light diffuses and becomes a new light source from the diffused position, so that the area of the light source can be equivalently expanded.

As the photoelectric sensor, there is also used a separation type photoelectric sensor in which a head section for projecting and receiving light and an amplifier section for signal processing are separated and connected by an optical fiber. A description will be given of making a surface light source when such an optical fiber is used as the light source instead of the light emitting diode 11. FIG. 5 (a)
If the light source is provided to the head portion through the optical fiber 21, a rod 22 having a cylindrical shape is provided at the tip end portion thereof to enlarge the light source area. The cylindrical rod 22 is, for example, a transparent cylindrical member made of glass or plastic, and the light is emitted in a wide range by reflecting the side surface of the light.

In FIG. 5B, a funnel 23 is provided at the tip of the optical fiber 21. The funnel 23 has a truncated cone shape and is configured so that a light emitting surface is widened. Like the rod 22, the funnel 23 is made of a transparent member made of glass or plastic. By enlarging the light source in this way, it is not necessary to use a lens having a short focal length.

FIG. 6A is a diagram showing the construction of an optical system portion according to the second embodiment of the present invention. FIG. 6A shows FIG.
In (a), the collimating lens 12 is not used and only the diffusion plate is used. FIG. 6A is a diagram showing a light distribution when only the diffuser plate is used. Light from the light emitting diode 11 which is a light projecting element is diffused by the diffuser plate 13.
It shows a state of being incident on and diffusing. Other configurations are the same as those of the first embodiment. Also in this case, it is possible to obtain substantially the same effect as that of the above-described embodiment. However, since the light is distributed in the diffusing direction, all the light does not enter the light projecting lens 3, and the light utilization efficiency is not high. FIG. 1
The light distribution on the line A-A 'is non-uniform as shown in FIG. Therefore, as shown in FIG. 6B, if the light is once made parallel by using the collimator lens 12 and then the light is diffused by the diffusion plate 13, the light utilization efficiency can be improved. Also, instead of the diffusion plate, as shown in FIG.
Even if the surfaces 14a and 15a shown in (c) are textured or a diffraction grating is used, the light utilization efficiency can be similarly improved.

FIG. 7 is a view showing an example of a photoelectric sensor according to the third embodiment of the present invention. In this figure, the optical system part is provided in the head part 51 with the light source 5 as in the above-described embodiment.
2, a collimator lens 53, and a diffusion plate 54 are provided.
Further, the projection lens 5 is provided behind the diffusion plate 54 at a constant interval.
5, and a polarizing filter 56 for aligning the polarization direction of light is provided on the front side of the light projecting lens 55.
The light source is a surface light source, and the positional relationship among the light source, the light projecting lens 55, and the detection object is the same as in the first embodiment. The polarization filter 56 emits the light of the light source to a detection object only in a specific polarization direction, for example, one of the P polarization and the S polarization, in this case, only the S polarization component. The reflected light from the detection object is polarized beam splitter 5 as shown in the figure.
By S 7, the S-polarized component is reflected and the P-polarized component is transmitted to be separated. Then, these reflected lights are received by the pair of light receiving portions, that is, the light receiving lens 58, the light receiving element 59, the light receiving lens 60, and the light receiving element 61. On the front surfaces of the light receiving lenses 58 and 60, a polarization filter that transmits only the P-polarized component and a polarization filter 63 that transmits only the S-polarized component are arranged. These light receiving elements 59, 61
Are amplified through amplifiers 64 and 65, respectively, and input to the difference circuit 66. The difference circuit 66 determines the surface state of the detected object based on the level of the difference between these input signals. That is, if the glossiness of the surface of the detection object is high, the polarization direction of the light emitted from the light source unit is preserved,
The level of reflected light having the same polarization component as the incident light is higher than that of the other polarization component, and the output level of the difference circuit 66 is high. On the other hand, in a detection object having a low glossiness, the polarization component is not preserved, so the level difference of the reflected light of the polarization components in both directions, that is, the output of the difference circuit becomes low. Therefore, it is possible to determine the glossiness of the detected object based on the difference output. Further, the glossiness can be calculated based on the output ratio of the amplifier circuits 64 and 65 instead of the difference circuit. In the present embodiment as well, similar to the first and second embodiments, the surface state of the detection object can be detected without being significantly affected by the inclination and distance variation of the detection object and the minute irregularities on the surface.

It goes without saying that the end portions of the optical fibers may be arranged at the positions of the light projecting element and the light receiving element, respectively, and the head section and the signal processing section may be separated. Further, the means for enlarging the light source area may be any of those shown in FIG. Further, the light projecting portion can be configured without using the collimator lens as in the second embodiment.

[0019]

As described in detail above, according to the first and second aspects of the present invention, in the reflection type photoelectric sensor for detecting an object which is specularly reflected, when the object is tilted or when the distance is varied. In addition, it is possible to provide a photoelectric sensor that is not easily affected by any of the cases where the surface has minute irregularities, and can reliably detect the presence or absence of an object and the gloss level. Further, in the invention of claim 3, the light receiving level at the light receiving position can be made substantially constant by using the diffusion plate, and in the invention of claim 4, the light of the light projecting element is once collimated by using the collimating lens. With this, it is possible to obtain the effect that the light utilization efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a reflective photoelectric sensor according to a first embodiment of the present invention.

FIG. 2 is a graph showing a received light intensity distribution at a light receiving position of the photoelectric sensor according to the present embodiment.

FIG. 3 is a diagram showing various configurations of a light projecting unit of an optical system portion of the present embodiment.

FIG. 4 is a diagram showing a ray trace of the present embodiment.

FIG. 5 is a diagram showing a method of enlarging a light source area when an optical fiber is used as a light source in the present embodiment.

6A is a configuration of a light projecting portion of the reflective photoelectric sensor according to the second embodiment, which does not use a collimating lens, FIG.
FIG. 6B is a diagram showing a configuration of the first embodiment using a collimator lens.

FIG. 7 is a block diagram showing an overall configuration of a photoelectric sensor according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a state in which a conventional focused beam photoelectric sensor and a detection object are tilted.

FIG. 9 is a diagram showing influences on a distance variation and a surface state of a conventional focused beam photoelectric sensor.

FIG. 10 is a diagram showing a state in which a conventional divergent beam photoelectric sensor and a detection object are tilted.

FIG. 11 is a diagram showing influences on a distance variation and a surface state of a conventional divergent beam photoelectric sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflection type photoelectric sensor 2 Light source 3,55 Light emitting lens 4 Light receiving lens 5 Light receiving element 6 Amplifier 7 Comparator 8 Output circuit 10 Detecting object 11 Light emitting diode 12, 14, 53 Collimating lens 13, 54 Diffusing plate 15 Fresnel lens 21 Light Fiber 22 Rod 23 Funnel 51 Head 56, 62, 63 Polarizing filter 64, 65 Amplifying circuit 66 Differential circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shin Nakamura 10 Odoron-cho, Hanazono Todo-cho, Ukyo-ku, Kyoto-shi, Kyoto Prefecture

Claims (4)

[Claims] 1. A light source, a light projecting lens that guides the light incident from the light source to an object detection region, a light receiving unit that receives reflected light from an object that specularly reflects the light, and a positive light received by the light receiving unit. In a reflection type photoelectric sensor having a discriminating unit that discriminates the level of an object by the level of reflected light, the light source is a surface light source that emits light from a surface facing the light projecting lens, and the light projecting lens is The reflection type photoelectric sensor is characterized in that light from the center of the surface light source is focused on the surface of the detection object, and light from the periphery of the surface light source is diffused and incident on the surface of the detection object. . 2. A light source that emits light having a polarization component of either P-polarized light or S-polarized light, a light projecting lens that guides the light incident from the light source to an object detection area, and an object that specularly reflects light. Of the reflected light of P, the light of the P-polarized component and the light of the S-polarized component are separately received, and the discrimination for discriminating the surface state of the object based on the output levels of the P-polarized component and the S-polarized component by the light receiving unit. In the reflection type photoelectric sensor having the means, the light source is a surface light source that emits light from a surface facing the light projecting lens, and the light projecting lens receives light from a center of the surface light source of the detection object. A reflection-type photoelectric sensor, wherein the reflection-type photoelectric sensor is arranged such that the light from the periphery of the surface light source is diffused and incident on the detection object surface while being focused on the surface. 3. The reflection type photoelectric sensor according to claim 1, wherein the light source includes a light projecting element and a diffusing means for diffusing the light of the light projecting element. 4. The light source includes: a light projecting element; a collimating lens that collimates the light of the light projecting element; and a diffusing unit that is provided behind the collimating lens to diffuse the parallel light. The reflective photoelectric sensor according to claim 1, wherein the photoelectric sensor is a reflective photoelectric sensor.