WO2018209957A1

WO2018209957A1 - Sensor main body and regression reflection type photoelectric sensor

Info

Publication number: WO2018209957A1
Application number: PCT/CN2017/118234
Authority: WO
Inventors: 张宁; 叶立平; 谢廷若
Original assignee: 深圳市志奋领科技有限公司
Priority date: 2017-05-18
Filing date: 2017-12-25
Publication date: 2018-11-22
Also published as: CN107340006A

Abstract

A sensor main body, comprising a light-emitting element, a light-receiving element, and a driving circuit (8). The light-emitting element comprises a light source (1) and a first collimating lens (2); the light-receiving element comprises a second collimating lens (4), a polarization splitter (5), a first photoelectric detector (6), and a second photoelectric detector (7); both the first photoelectric detector (6) and the second photoelectric detector (7) are electrically connected to the driving circuit. In addition, also disclosed is a regression reflection type photoelectric sensor, comprising the sensor main body and a regression reflector (3). The regression reflector (3) comprises a pyramid (32) and a dichroic polarizer disposed on the reflection surface of the pyramid; the pyramid (32) is used for converting incident light transmitted by the sensor main body to emergent light. The regression reflection type photoelectric sensor of the present invention features a simple process and low costs; the polarization of the emergent light is uniform and the extinction ratio is high; moreover, the cooperation of the regression reflector and the sensor main body improves a detection distance of the photoelectric sensor.

Description

Sensor body and retroreflective photoelectric sensor

Technical field

The invention relates to the field of photoelectric technology, in particular to a sensor body and a retroreflective photoelectric sensor.

Background technique

At present, in the field of industrial and consumer, the field that needs retroreflection generally adopts a pyramid array to realize the original return of the beam.

The polarization distribution of the ordinary pyramid is not uniform, so some people think of using the optical effect sheet, but the pyramid method based on the optical rotation effect is complicated, and it needs to be used with the phase retarder. It is impossible to use all the incident surfaces of the pyramid, and the distribution of the polarization state is not Uniform, resulting in a large volume; the prior art is a U.S. patent entitled "Optical Conformal Cone", which is US20050264883A1.

In addition to the above prior art, there is a pyramidal array retroreflective sheet, which is a periodic arrangement of ordinary pyramids in a two-dimensional direction, and the output polarization state is evenly distributed, which can be made thin, but the process machine is complicated. Therefore, the cost is relatively high; and the polarization state reflected back by the retroreflective sheeting of the pyramid array is an elliptical polarization state. Due to the low extinction, in the case of limited power, the detection of a long distance cannot be performed.

Although the etched grating can be used to distort the pyramid, it is necessary to etch the precise stripe on the three vertical surfaces of the pyramid to meet the requirements of the polarizing. The grating etching angle and density are highly demanded, the process is complicated, and the cost is relatively high. high.

Summary of the invention

In order to overcome the deficiencies of the prior art, it is an object of the present invention to provide a sensor body that can deflect retroreflected light into linearly polarized light.

Another object of the present invention is to provide a retroreflective photoelectric sensor capable of detecting sensitivity by using orthogonal polarization dual channel detection.

One of the objects of the present invention is achieved by the following technical solutions:

A sensor body includes a light emitting element, a light receiving element, and a driving circuit, the light emitting element including a light source and a first collimating lens, the light receiving element including a second collimating lens, a polarization splitter, a first photodetector, and a second photodetector, wherein the first photodetector and the second photodetector are electrically connected to the driving circuit;

The light source and the first collimating lens are sequentially disposed coaxially on the light-emitting path, and the second collimating lens and the polarization splitter are coaxially disposed on the light-receiving path, and the polarization splitter is configured to receive the received light. The outgoing light is divided into s-polarized light and p-polarized light, the first photodetector is configured to receive p-polarized light and transmit a first photocurrent signal to a driving circuit, and the second photodetector is configured to receive s-polarized light and transmit the first a photocurrent signal is sent to the driving circuit; the driving circuit is configured to determine a magnitude of the differential photocurrent signal and a preset value, wherein the differential photocurrent signal is a difference between the first photocurrent signal and the second photocurrent signal.

Further, the polarization splitter comprises a polarization beam splitting prism, a first right angle prism, a second right angle prism, a third right angle prism and a phase compensation plate; the polarization beam splitting prism is used to divide an incident light into p polarization Light and s-polarized light, said p-polarized light sequentially passing through a first right-angle prism and a second right-angle prism; said s-polarized light sequentially passing through a third right-angle prism and a phase compensating plate; said phase compensating plate is used for s-polarized light Phase compensation is performed to cause the s-polarized light to undergo an equal optical path with the p-polarized light. Through the orthogonal dual-channel polarization detection, the influence of common mode noise is eliminated, and the detection signal-to-noise ratio is improved.

Further, the first right angle prism, the second right angle prism and the third right angle prism are all total reflection prisms.

Further, the light source is an LED light source.

Further, the light source is disposed at a focus of the first collimating lens.

The second object of the present invention is achieved by the following technical solutions:

A retroreflective photoelectric sensor comprising a sensor body and a retroreflector as described above, the retroreflector comprising a pyramid and a dichroic polarizer disposed on the pyramidal reflecting surface, the pyramid being used The incident natural polarized light transmitted from the sensor body is converted into linearly polarized outgoing light, and the direction of the main axis of the dichroic polarizing plate coincides with the polarization direction of the outgoing polarized light.

Further, the dichroic polarizer is glued to the pyramidal reflection surface by optical glue.

Further, the material of the pyramid is glass or optical plastic.

Compared with the prior art, the beneficial effects of the present invention are:

The retroreflector of the photoelectric sensor of the invention has simple process, low cost, uniform polarization state of the emitted light, high extinction ratio, and the cooperation of the retroreflector and the sensor body improves the detection distance of the photoelectric sensor.

DRAWINGS

Figure 1 is a structural view of a photoelectric sensor of the present invention;

2 is a structural view of an orthogonal polarization splitter of a sensor body of the present invention;

Figure 3 is a structural view of a retroreflector of the present invention;

Figure 4 is the coordinate system of the pyramid;

Figure 5 is a sectional view of the entrance surface area of the pyramid;

Figure 6 is an incident view of light;

Figure 7 is a graph showing the relationship between the reflected amplitude s component and the p component complex amplitude reflectance as a function of incident angle;

Figure 8 is a graph showing changes in the phase of the reflected light s component and the p component with angle;

Figure 9 is a schematic diagram of an elliptic equation;

FIG. 10 is a schematic diagram showing changes in phase difference between the s component and the p component of the reflected light.

Reference numerals: 1, light source; 2, first collimating lens; 3, retroreflector; 31, polarizing plate; 32, pyramid; 4, second collimating lens; 5, polarization splitter; Splitting prism; 52, first right angle prism; 53, second right angle prism; 54, third right angle prism; 55, phase compensation plate; 6, first photodetector; 7, second photodetector; Circuit; 9, sensor body; 10, transmission optical path.

detailed description

The present invention will be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the embodiments described below may be arbitrarily combined to form a new embodiment. .

As shown in FIG. 1, the present invention provides a retroreflective photoelectric sensor including a sensor body 9 and a retroreflector 3, the sensor body 9 including a light emitting element, a light receiving element, and a driving circuit 8, the light emitting element The light source 1 includes a second collimating lens 4, a polarization splitter 5, a first photodetector 6, and a second photodetector 7, the first photodetector Both the 6 and the second photodetectors 7 are electrically connected to the driving circuit 8; the material and thickness of the retroreflector are required to be tourmaline having a thickness greater than 1 mm, or cinchona iodosulfate having a thickness greater than 0.3 mm.

As shown in FIG. 2, the present invention provides a polarization splitter 5 comprising a polarization beam splitting prism 51, a first right angle prism 52, a second right angle prism 53, a third right angle prism 54, and a phase compensation plate 55; The first right angle prism 52, the second right angle prism 53, and the third right angle prism 54 are all total reflection prisms. The polarization beam splitting prism 51 is configured to divide an incident light into p-polarized light and s-polarized light, and the p-polarized light sequentially passes through the first right-angle prism 52 and the second right-angle prism 53; the s-polarized light sequentially passes through A three-corner prism 54 and a phase compensating plate 55 are used for phase compensation of the s-polarized light to cause the s-polarized light and the p-polarized light to undergo an equal optical path.

Since the polarization state of the incident light may be linearly polarized, it may also be elliptically polarized, but after the incident light is reflected by the retroreflector 3, the emitted light projects the polarization into two perpendicular directions, one being horizontal, that is, The y-axis, the other is the vertical direction, that is, the z-axis; the incident beam is divided into vertical linearly polarized light and horizontal linearly polarized light by the polarization beam splitting prism 51; the p-polarized light passes through the first right-angle prism 52 and the second After the total reflection of the right-angle prism 53 is emitted as p-polarized light, the s-polarized light is totally reflected by the third right-angle prism 54 and then phase-compensated by the phase compensating plate 55 so that the s-polarized light and the p-polarized light undergo the same optical path.

The light source 1 and the first collimating lens 2 are sequentially disposed coaxially on the light-emitting path, and the second collimating lens 4 and the polarization splitter 5 are sequentially disposed coaxially on the light-receiving path, and the polarization splitter 5 For dividing the received outgoing light into s-polarized light and p-polarized light, the first photodetector 6 is configured to receive p-polarized light and transmit a first photocurrent signal to the driving circuit 8, the second photodetecting The device 7 is configured to receive s-polarized light and transmit a first photocurrent signal to the driving circuit 8; the driving circuit 8 is configured to determine a magnitude of the differential photocurrent signal and a preset value, where the differential photocurrent signal is the first photocurrent a difference between the signal and the second photocurrent signal; the light source 1 is an LED light source; and the light source 1 is disposed at a focus of the first collimating lens 2.

The working principle of the embodiment: the light emitted by the LED light source is collimated and transmitted through the first collimating lens 2, and transmitted to the retroreflector 3 through the transmission optical path 10, and the incident light is totally reflected in the pyramid 32, and is emitted as Linearly polarized light, the polarization direction of the outgoing light is in the Y-axis direction, and the retroreflected light is concentrated by the second collimating lens 4, enters the polarization splitter 5, and then passes through the polarization splitter 5, and the p-polarized light is concentrated at At the second photodetector 7, the s-polarized light is concentrated in the first photodetector 6, and the threshold value of the driving circuit 8 determines that the current is a differential photocurrent signal;

The driving circuit 8 can calculate the ratio of the photocurrents returned by the two channels of the first photodetector 6 and the second photodetector 7 to calculate the ratio of the two-channel photocurrents, and can set a plurality of ratios according to the setting. The ratio of the size to count.

Due to the use of the orthogonal polarization splitter, the polarization state of the linearly polarized light after the transparent body changes, resulting in different light receiving light currents of the first photodetector 6 and the second photodetector 7 of the two receiving channels. The ratio of the photocurrent of the two channels reflects the angular deflection of the linearly polarized light, and the angular deflection of the linearly polarized light is related to the thickness of the transparent body, so that the transparent body of a specific thickness can be detected by calibrating the ratio of the intensity of the two-channel photocurrent.

By calibration, the difference between the photocurrent intensities of the p-polarized light channel and the s-polarized light channel received by the transparent object of a certain thickness is determined. When the threshold is reached, the counter of the thickness transparent body is incremented by one, and multiple calibrations can be set. The value realizes the function of counting the transparent bodies of different thicknesses on the same production line.

As shown in FIG. 3, the present invention provides a retroreflector 3 applied to a retroreflective photoelectric sensor, comprising a pyramid 32 and a dichroic polarizer 31 disposed on the reflecting surface of the pyramid 32, The pyramid 32 is used to convert incident light transmitted by the sensor body 9 into outgoing light. The dichroic polarizing plate 31 is glued to the reflecting surface of the pyramid 32 by optical glue. The material of the pyramid 32 is glass or optical plastic. The optical axis direction of the dichroic polarizing plate 31 is along the y-axis, thereby ensuring that the polarization state of the retroreflected light is horizontal, that is, along the y-axis.

According to the ray tracing theory, the optimal design of the pyramidal area is obtained. By coating a thin layer of dichroic material on the incident surface of the pyramid, the polarization state of the exiting cone is controlled, so that the polarization state of the outgoing light is uniform. The polarized light has a high extinction ratio, a large effective area, a simple manufacturing process, and low cost.

The coordinate system of the pyramid shown in Figure 4, the four planes of the pyramid and the unit normal vector of the plane are:

The coordinate range of the intersection of the ray and each plane is constrained as:

When the ABC surface ray is incident perpendicularly, the incident point of the ray is (x ₀ , y ₀ , z ₀ ), and the direction vector is

The straight line equation is:

The light is incident on the OAC plane, the incident ray equation (6), the OAC plane equation (2), and the simultaneous equations obtain the coordinates of the incident point:

Light ray reflection formula based on vector form, incident ray vector

Exit ray vector

Incident plane unit normal vector

The direction is defined as follows:

The light is totally internally reflected on the surface of the OAC. The reflected light equation is:

The light after total internal reflection is incident on the surface of the OBC, and total internal reflection occurs. The equation of the plane OBC is (1), and the intersection of the line and the plane is:

According to the reflection law of the vector form, the equation of the light after the OBC reflection is obtained as follows:

The reflected light above is incident on the OAB plane. The plane equation of OAB is (3). The intersection of the incident light of the OAB plane and the plane is:

The reflected light of the OAB plane, according to the coordinates of the intersection point, the normal equation, and the law of reflection in the vector form, can obtain the linear equation of the outgoing light as:

The exiting ray passes through the ABC plane and finally exits the pyramid. According to the above reflected ray and the ABC plane equation (4), the coordinates of the exiting pyramid are finally obtained:

According to the above theoretical derivation, the light of each incident pyramid can be traced, thereby obtaining the coordinate position relationship between the incident pyramid and the exit pyramid.

As shown in Fig. 5, and depending on the symmetry, considering the positional possibilities of all incident pyramids, the positional possibilities of all the exiting pyramids are obtained. Regarding the area of the exit surface of the pyramid, the R1-R3 is an invalid area, and the light incident in this area cannot reflect the pyramid. The effective area is the hexagonal area in Fig. 5, and the R4 area is incident and will be emitted from R4'. The R5 region is incident, will be emitted from R5', is incident from the R6 region, will be emitted from R6', and is composed of R4R5R6R4'R5'R6' and other hexagons, thereby achieving the optimal area design of the pyramid.

As wrong! The reference source was not found. As shown, the amplitude reflectance of the reflected light has

Among them, 1 is the incident medium, 2 is the refractive medium, such as error! The reference source was not found. It is the relationship between the reflected amplitude s component and the p component complex amplitude reflectivity with the incident angle, wrong! The reference source was not found. It is the change of the phase of the reflected light s component and the p component with the angle, so that the additional phase after three times of total reflection can be obtained when the normal incident pyramid is obtained.

At normal incidence, total reflection results in an additional phase. When the angle prism is incident, the angle of incidence of the three reflecting surfaces is fixed at an angle of 54.74 degrees.

At normal incidence, the phase difference between p-light and s-light is increased by 0.768 rad (44 degrees) for each reflection. After three times of total reflection, the final phase is 2.304 rad, and if the ray is polarized, it is emitted as elliptically polarized light.

As wrong! The reference source was not found. Schematic diagram of an elliptic equation of general form of elliptically polarized light, the expression of which is

As wrong! The reference source was not found. When the phase difference between the s component and the p component is changed, the change process of the polarization state, except for the special 0, pi phase, is an elliptically polarized form. When the phase angle is

The range is elliptically polarized, and the detection sensitivity depends on the ratio of the long axis to the short axis of the elliptically polarized light.

The polarizing plate 31 is placed on the incident surface of the pyramid 32, or the pyramid material is plated on the surface of the pyramid, and the incident light is polarized to the polarizing plate 31 to enter the pyramidal reflection, and the phase is reflected by the total reflection. The pyramid is elliptically polarized light, which passes through the polarizing plate 31 and becomes linearly polarized light, and the detection sensitivity is from 0 to 100%. The material of the polarizing plate 31 is a dichroic dye polarizing material, which is plated on the incident surface of the pyramid 32 by a plating process, or is disposed as an adjustable direction polarizing plate 31 against the pyramid 32.

The above embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention belong to the present invention. The scope of the claim.

Claims

A sensor body comprising a light-emitting element, a light-receiving element and a driving circuit, the light-emitting element comprising a light source and a first collimating lens, wherein the light-receiving element comprises a second collimating lens, a polarization splitter, a first a photodetector and a second photodetector, wherein the first photodetector and the second photodetector are electrically connected to the driving circuit;

The light source and the first collimating lens are sequentially disposed coaxially on the light-emitting path, and the second collimating lens and the polarization splitter are coaxially disposed on the light-receiving path, and the polarization splitter is configured to receive the received light. The outgoing light is divided into s-polarized light and p-polarized light, the first photodetector is configured to receive p-polarized light and transmit a first photocurrent signal to a driving circuit, and the second photodetector is configured to receive s-polarized light and transmit the first The two photocurrent signals are sent to the driving circuit; the driving circuit is configured to determine a magnitude of the differential photocurrent signal and the preset value, and the differential photocurrent signal is a difference between the first photocurrent signal and the second photocurrent signal.
The sensor body according to claim 1, wherein said polarization splitter comprises a polarization beam splitting prism, a first right angle prism, a second right angle prism, a third right angle prism, and a phase compensation plate; said polarization splitting The prism is configured to divide an incident light into p-polarized light and s-polarized light, and the p-polarized light sequentially passes through the first right-angle prism and the second right-angle prism; the s-polarized light sequentially passes through the third right-angle prism and the phase compensation plate; The phase compensator is used to phase compensate s-polarized light such that s-polarized light and p-polarized light experience an equal optical path.
The sensor body according to claim 2, wherein said first right angle prism, said second right angle prism, and said third right angle prism are all total reflection prisms.
The sensor body of claim 1 wherein said light source is an LED light source.
The sensor body of claim 1 wherein said light source is disposed at a focus of said first collimating lens.
A retroreflective photoelectric sensor comprising the sensor body according to claim 1 and a retroreflector, the retroreflector comprising a pyramid and a dichroic polarizer disposed on the pyramid reflecting surface The pyramid is used to convert incident light transmitted by the sensor body into outgoing light.
The retroreflective photoelectric sensor according to claim 6, wherein the predetermined thickness of the dichroic polarizer is glued to the pyramidal reflection surface by optical glue.