CN115615541A - Photoelectric sensor with double-emission-wavelength light source design - Google Patents

Photoelectric sensor with double-emission-wavelength light source design Download PDF

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CN115615541A
CN115615541A CN202211134243.5A CN202211134243A CN115615541A CN 115615541 A CN115615541 A CN 115615541A CN 202211134243 A CN202211134243 A CN 202211134243A CN 115615541 A CN115615541 A CN 115615541A
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light
lens
emitting
light source
wavelength
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赵爱伦
叶立平
唐可信
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Shenzhen Akusense Technology Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/0295—Constructional arrangements for removing other types of optical noise or for performing calibration
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0407—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors

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  • Spectroscopy & Molecular Physics (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Abstract

The invention relates to the technical field of reflection type and opposite type photoelectric sensors, in particular to a photoelectric sensor technology with a double-emission wavelength light source design. The invention mainly aims at the light source of the light emitting unit and the light receiving unit to carry out special design, so that the sensor has stronger environment light interference resistance and convenient and accurate debugging and installation.

Description

Photoelectric sensor with double-emission-wavelength light source design
[ technical field ] A method for producing a semiconductor device
The invention relates to the technical field of reflection type and opposite type photoelectric sensors, in particular to a photoelectric sensor technology with a double-emission wavelength light source design.
[ background of the invention ]
As shown in fig. 1, the conventional light receiving unit 12 and the conventional light emitting unit 13 are both located in a closed space of the sensor, the sensor light emitting unit emits light, when an object 15 is present in a set detection range, the light emitted by the sensor light emitting unit is reflected by the object, part of the reflected light is received by the light receiving unit to generate an electrical signal, and the electrical signal is transmitted to a processing circuit by a signal output line 14, and then the sensor emits a command signal.
The principle of the correlation type photoelectric sensor is shown in fig. 2, the existing light emitting unit 12 and the existing light receiving unit 13 are separated, when no object 15 is arranged between the light emitting unit and the light receiving unit, the light receiving unit can receive light, when an object to be detected enters a detection range, light beams can be shielded, so that the light receiving unit cannot receive the light emitted by the light emitting unit, the light is transmitted to a processing circuit through a signal output line 14, and therefore the change of optical signals is detected, and a receiving end reacts.
The existing photoelectric sensor emitting end light source generally adopts single-wavelength red light or near infrared light, and the wavelength is about 650nm, about 850nm or 940nm which is more commonly used. The use of red light as the light source is because the light beam is easily recognized when it strikes an object, and is also a common practice in the field of industrial automation. However, a photoelectric sensor using red light as a light source at an emission end is relatively easily interfered by various light sources in the environment, because the ambient light generally contains light waves of about 650nm, especially in recent years, because LED illumination is popularized, the brightness of an LED illumination light source is high, and interference is more easily caused. And adopt near-infrared light as transmitting end light source sensor, because be invisible light, can't see the facula that the sensor jetted out with the naked eye, when debugging installation, can't accurately find the central part of facula, be difficult to detect object or accurate receiver, whether sensor light emitting element normally works in addition also can't audio-visual judgement.
[ summary of the invention ]
Aiming at the problems, the invention mainly aims at the light source of the light emitting unit and the light receiving unit to carry out special design, so that the sensor has stronger ambient light interference resistance and the convenience and the accuracy of debugging and installation. The light-emitting element adopts a light source emitting two wavelengths, and comprises two independent light-emitting chips of visible light and near infrared light, and the light-emitting chips can be LEDs. The invention is characterized in that through the special layout of two light emitting chips emitting different wavelengths, as shown in fig. 4 and 5, the light emitting chips of the light source are stacked in close contact in space, wherein the infrared light emitting chip is arranged at one side close to the lens, the red light emitting chip is arranged at the other side, the light emitting surfaces of the two light emitting chips face the emitting lens, the area of the red light emitting chip is larger than that of the near infrared light emitting chip, the central axes of the two light emitting chips coincide, or the distance error of the central axes is less than 5mm, so as to ensure that the centers of light spots of light beams passing through the lens coincide or nearly coincide;
the invention adopts light capable of emitting light with two wavelengths as a light source, the emitted light beams with two wavelengths comprise visible light and near infrared light, and the centers of light spots of the visible light and the near infrared light are coincident or nearly coincident. Therefore, the accurate position of light irradiation can be very conveniently found by observing the light spot of the visible light in the installation and debugging process, so that a measured object is correctly placed in the detection range of the sensor, and meanwhile, the visible light spot can be used as the reference of the near-infrared light spot range because the center of the near-infrared light spot is coincident with or close to the center of the visible light spot. In addition, a narrow-band filter is added in front of a light receiving element (generally a silicon-based photosensitive element, and different devices are adopted according to requirements) in the light receiving unit to filter light except a near-infrared light source, and near-infrared light is adopted as received detection light, so that the interference of visible light in a use environment is avoided, and the purpose of stable detection is achieved.
The invention relates to the technical field of a photoelectric sensor with a double-emission wavelength light source design, in particular to the technical field of a reflection type photoelectric sensor and a correlation type photoelectric sensor, and the structure of the photoelectric sensor with the double-emission wavelength light source design comprises a light emitting unit, a light receiving unit and a signal processing unit, wherein:
the light emitting unit consists of a driving power circuit, a dual-wavelength emitting light source and an emitting lens, wherein the driving power circuit is connected with the dual-wavelength emitting light source, the dual-wavelength emitting light source is formed by special layouts of two light emitting chips emitting different wavelengths, the dual-wavelength emitting light source and the emitting lens are connected and fixed through a fixing device, a certain distance is kept as required, and the driving circuit provides power for the light source;
the light receiving unit comprises a light beam receiving lens, an optical filter and a photosensitive element, the light beam receiving lens is fixedly connected with the photosensitive element through a fixing device, the light beam receiving lens is used for collecting light reflected by a measured object or light emitted by a transmitter and converging the light to a light receiving surface of the photosensitive element, and the optical filter is used for filtering light in a visible light wavelength range, only allowing near infrared light to pass through and eliminating visible light interference; considering the limited space in the sensor, the filter of the receiving unit can be removed, and the filter is plated on the surface of the receiving lens to filter the light except the emitted light wavelength;
the signal processing unit comprises a series of electric signal processing elements which are connected with the light receiving unit through electrodes, and the signal processing unit is used for amplifying and processing the electric signals output by the photosensitive elements into standard signals capable of communicating with the outside of the sensor;
further, it is characterized in that: the dual-wavelength emission light source comprises a visible light wavelength light source and a near infrared wavelength light source, and comprises two independent light emitting chips of visible light and near infrared light, wherein the light emitting chips can be LEDs;
further, it is characterized in that: through the special layout of two light-emitting chips emitting different wavelengths, the light-emitting chips of the light source adopt a spatial stacking mode, wherein the infrared light-emitting chip is arranged at one side close to the lens, the red light-emitting chip is arranged at the other side, the diameter of the red light chip is larger than that of the infrared light chip, the light beam axial lines (104) of the two light-emitting chips are coincided, and the distance of the central axial lines is less than 5mm;
furthermore, the two light emitting chips emitting different wavelengths are specially arranged, the diameter of the red light chip is D1, the diameter of the infrared chip is D2, the diameter of the emitting lens is D3, and the emitting lens has the function of converging light emitted by the light source according to the use scene so that the light beam energy is concentrated in the range needing to be detected; wherein D1, D2, D3 must satisfy the following conditions:
d1 is less than or equal to D3/10, because the LED is regarded as a point light source when the lens is designed, provided that the diameter of the light source is less than 1/10 of the diameter of the lens;
D1-D2 is more than or equal to 2 mu m, and according to the experiment, a red light spot can not be observed if the red light emitting area is too small;
d2 is more than or equal to 10 mu m, so as to ensure that the intensity of the infrared light emitted is enough to detect an object, and practical tests show that when the diameter of the light-emitting chip is smaller than the value, the sensor cannot work normally due to the fact that the signal received by the sensor receiving unit is too weak, namely the radiation flux emitted by the light source is insufficient;
wherein the ranges of D1, D2, and D3 discussed herein are those for photosensors whose values are limited to practical use, in this type of photosensor structure the distance between the light emitting chip of the light source and the center point of the lens is in the range of 2-30 mm.
Further, it is characterized in that: the design of the lens at the transmitting end should follow the focal length relationship f Red light ＜f Design of ＜f Infrared ray Because, the focal length formula of the emitting end lens (103) is as follows:
Figure BDA0003849167290000041
n is the refractive index of the glass, d is the center thickness of the lens, when d =0, the lens is a thin lens, f is the focal length, and r is the spherical radius of the lens. Because the propagation speeds of different wavelengths in the glass are different and the refractive indexes are also different, the focal lengths are also different, namely the focal lengths of the same lens are different under the condition of different wavelengths. According to the Cauchy's formula, the longer the wavelength, the smaller the refractive index; according to the focal length formula of the lens, the smaller the refractive index is, the longer the focal length is.
The relationship between the vertical axis magnification β and the focal length f is that, where x is the distance of the image
Figure BDA0003849167290000051
In order to ensure that the centers of the light spots of the red light and the near infrared light coincide after passing through the lens, and the overlapping of the light spot ranges is reduced as much as possible, the design of the lens (103) at the transmitting end follows f Red light ＜f Design of ＜f Infrared ray 。
Compared with the prior art, the invention has the following advantages:
the invention is developed aiming at the situations, and takes the light source with two wavelengths of red light and near infrared light into consideration, the lens passing through the light emitting unit can generate axial chromatic aberration and transverse chromatic aberration, and especially the transverse chromatic aberration has larger influence on the light spot coverage. The focal length of the lens is as follows
Figure BDA0003849167290000052
n is the refractive index of the glass, d is the center thickness of the lens, when d =0, the lens is a thin lens, f is the focal length, and r is the spherical radius of the lens. Because the propagation speeds of different wavelengths in the glass are different and the refractive indexes are also different, the focal lengths are also different, namely the focal lengths of the same lens are different under the condition of different wavelengths. According to the Cauchy's formula, the longer the wavelength, the smaller the refractive index; according to the lens focal length formula, the smaller the refractive index, the longer the focal length.
The relationship between the vertical axis magnification beta and the focal length f is that, where x is the distance of the image
Figure BDA0003849167290000061
In order to make the centers of the light spots coincide after the red light and the near infrared light pass through the lens and simultaneously reduce the overlapping of the light spot ranges as much as possible, the design of the lens should follow the focal length f Red light ＜f Design of ＜f Infrared ray . Therefore, the lens of the emitting part of the sensor is also designed by special achromatism, so that the center of the light spot of the emergent red light and the center of the light spot of the near infrared light are coincident or nearly coincident. The light receiving unit part is additionally provided with a narrow-band filter to only allow near-infrared light energy emitted by the light source to reach the photoelectric detector. The purpose of design like this can be in installation debugging in-process, and the position of facula is all the time visible, has the effect of location, and convenient debugging does not receive the interference of lighting apparatus visible light in the environment again simultaneously in the sensor in-service use.
[ description of the drawings ]
FIG. 1 is a schematic diagram of a conventional reflective sensor;
FIG. 2 is a schematic diagram of a prior art correlation sensor; whether the projected light is blocked or not is taken as a detection basis;
FIG. 3 is a schematic diagram of a photosensor with a dual emission wavelength light source design according to the present invention;
FIG. 4 is a top view of the dual wavelength transmitting unit of the present invention in a spatially stacked manner;
FIG. 5 is a perspective view of the dual wavelength transmitting unit of the present invention in a spatially stacked manner;
fig. 6 is a schematic diagram of the operation of the dual wavelength transmitting unit of the present invention.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 3-6, the present invention provides a photoelectric sensor with dual emission wavelength light source design, which includes the following steps:
a structure of a photosensor 1 with a dual emission wavelength light source design includes a light emitting unit 10, a light receiving unit 20, and a signal processing unit 30, in which:
the light emitting unit 10 is composed of a driving power circuit 101, a dual-wavelength emitting light source 102 and an emitting lens 103, the dual-wavelength emitting light source 102 and the driving power circuit 101 are connected with the dual-wavelength emitting light source 102, the dual-wavelength emitting light source 102 and the emitting lens 103 are fixedly connected through a fixing device, and the driving circuit 101 supplies power to the light source;
the light receiving unit 20 comprises a light beam receiving lens 201, an optical filter 202 and a photosensitive element 203, the light beam receiving lens 201, the optical filter 202 and the photosensitive element 203 are fixedly connected by a fixing device, the light beam receiving lens 201 is used for collecting light reflected by a measured object or light emitted by a transmitter and converging the light to a light receiving surface of the photosensitive element 203, and the optical filter 202 is used for filtering light in a visible light wavelength range, only allowing near infrared light to pass through and eliminating visible light interference;
the signal processing unit 30 includes a series of electric signal processing elements, is connected with the light receiving unit 20 through the electrode 301, and has the function of amplifying and processing the electric signal output by the light sensing element 203 into a standard signal capable of communicating with the outside of the sensor.
The dual-wavelength emission light source 102 includes a visible light wavelength light source 104 and a near infrared wavelength light source 105, and the visible light wavelength light source 104 and the near infrared wavelength light source 105 emit light using separate light emitting chips. The visible light wavelength light source 104 adopts a red light emitting chip to emit visible light, and the near infrared wavelength light source 105 adopts an infrared light emitting chip to emit near infrared light; the light emitting chips may be LEDs. The invention is characterized in that through the special layout of two light-emitting chips emitting different wavelengths, the light-emitting chips of the light source adopt a spatial stacking mode, wherein the infrared light-emitting chip is arranged at one side close to the lens, the red light-emitting chip is arranged at the other side, the diameter of the red light-emitting chip is larger than that of the infrared light-emitting chip, the central axes of the two light-emitting chips are coincided, and the distance between the center of the red light-emitting chip and the central axis of the infrared light-emitting chip is less than 5mm.
The diameter of the red light emitting chip is D1, the diameter of the infrared light emitting chip is D2, and the diameter of the emission lens 103 is D3, wherein D1, D2, and D3 must satisfy the following conditions:
d1 is less than or equal to D3/10, because the light-emitting chip is regarded as a point light source when the lens is designed, provided that the diameter of the light source is less than 1/10 of the diameter of the lens;
D1-D2 is more than or equal to 2 mu m, because according to practical test experience, if a red light emitting area is too small, red light spots cannot be observed;
d2 is more than or equal to 10 mu m, so as to ensure that the intensity of the infrared light emitted is enough to detect an object, and practical tests find that the sensor cannot work normally when the diameter of the light-emitting chip is less than the value, namely the light-emitting intensity of the light source is insufficient;
the ranges of D1, D2 and D3 discussed herein are limited to practical use photosensors, and the distance between the light emitting chip of the light source and the center point of the lens in this type of photosensor structure is in the range of 2-30 mm.
The lens has the function of converging light emitted by the light source according to the use scene requirement, so that the energy of the light beam is concentrated in the range needing to be detected;
1. the first embodiment:
the structure of the present invention includes a light emitting unit 10, a light receiving unit 20, and a signal processing unit 30.
Wherein, the diameter D1 of the red light emitting chip is 0.5mm, the diameter D2 of the infrared light emitting chip is 0.3mm, and the diameter D3 of the emitting lens 103 is 6mm.
The LED chip comprises two independent light emitting chips of visible light and near infrared light, wherein the visible light wavelength is 650nm, and the near infrared wavelength is 850nm. According to the characteristics of the LED light source and the use requirement, the focal length f of the transmitting end lens 103 is actually designed after the achromatization is considered Design of ＝5.2mm
2. The second embodiment:
the red light emitting chip is square, the side length D1 is 0.6mm, the infrared light emitting chip is also square, the side length D2 is 0.3mm, the diameter D3 of the emitting lens is 6mm, the emitting wavelength of the red light emitting chip is 660nm, and the emitting wavelength of the infrared light emitting chip is 910nm. According to the characteristics of the LED light source and the use requirement, the focal length f of the transmitting end lens 103 is actually designed after achromatization is considered Design of ＝5.2mm
3. The third embodiment:
when a large object needs to be detected, and a small-area cavity is formed in part of the object or the reflectivity is very low (for example, less than 5%), the red light emitting chip is square, the side length D1 is 1mm, the infrared light emitting chip is circular, the diameter D2 is 0.8mm, and the diameter of the lens is 10mm.
The emission wavelength of the red light emitting chip is 620nm, and the emission wavelength of the infrared light emitting chip is 880nm.
According to the characteristics of the LED light source and the use requirement, the focal length f of the transmitting end lens (103) is actually designed after the achromatization is considered Design of ＝5.5mm。
4. The fourth embodiment:
when detecting small or fine objects, a small spot is required. The red light emitting chip is circular and has a diameter of 0.3mm, the infrared light emitting chip is circular and has a diameter of 0.2mm, and the emitting lens 103 has a diameter of 5mm.
Wherein, the emission wavelength of the red light emitting chip is 640nm, and the emission wavelength of the infrared light emitting chip is 930nm.
According to the characteristics of the LED light source and the use requirement, the focal length f of the transmitting end lens 103 is actually designed after achromatization is considered Design of ＝5.2mm。
Compared with the prior art, the invention has the following advantages:
the invention is developed in view of the above situation, and considering that the light source has two wavelengths of red light and near infrared light, the lens passing through the light emitting unit can generate axial chromatic aberration and lateral chromatic aberration, and especially the lateral chromatic aberration has a large influence. The focal length of the lens is as follows
Figure BDA0003849167290000101
n is the refractive index of the glass, d is the center thickness of the lens, when d =0, the lens is a thin lens, f is the focal length, and r is the spherical radius of the lens. Because the propagation speeds of different wavelengths in the glass are different and the refractive indexes are also different, the focal lengths are also different, namely the focal lengths of the same lens are different under the condition of different wavelengths. According to the Cauchy's formula, the longer the wavelength, the smaller the refractive index; according to the lens focal length formula, the smaller the refractive index, the longer the focal length.
The relationship between the vertical axis magnification β and the focal length f is that, where x is the distance of the image
Figure BDA0003849167290000102
In order to make the centers of the light spots coincide after the red light and the near infrared light pass through the lens and simultaneously reduce the overlapping of the light spot ranges as much as possible, the design of the lens should follow f Red light <f Design of <f Infrared ray . Wherein f is Red light Is the focal length of the red light emitting chip, f Design of Is the focal length of the emitter lens 103, f Infrared ray Is the focal length of the infrared light emitting chip; therefore, the lens of the emitting part of the sensor is also designed by special achromatism, so that the center of the light spot of the emergent red light and the center of the light spot of the near infrared light are coincident or nearly coincident. The light receiving unit part is additionally provided with a narrow-band filter to only allow near-infrared light energy emitted by the light source to reach the photoelectric detector. The purpose of design like this can be in installation debugging in-process, and the position of facula is all the time visible, has the effect of location, and convenient debugging does not receive the interference of lighting apparatus visible light in the environment again simultaneously in the sensor in-service use.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and any modifications, equivalents, improvements, etc. made within the spirit of the present invention should be included in the scope of the present invention.

Claims (5)

1. A photosensor with a dual emission wavelength light source design comprising a light emitting unit (10), a light receiving unit (20) and a signal processing unit (30), characterized by the following further comprising the features:
the light emitting unit (10) is composed of a driving power circuit (101), a dual-wavelength light emitting source (102) and an emitting lens (103), the driving power circuit (101) is connected with the dual-wavelength light emitting source (102), the dual-wavelength light emitting source (102) is composed of two light emitting chips emitting different wavelengths, the dual-wavelength light emitting source (102) and the emitting lens (103) are fixedly connected through a fixing device, and the dual-wavelength light emitting source (102) and the emitting lens (103) are arranged at intervals.
The light receiving unit (20) comprises a light beam receiving lens (201), an optical filter (202) and a photosensitive element (203), the light beam receiving lens (201), the optical filter (202) and the photosensitive element (203) are fixedly connected through a fixing device, the light beam receiving lens (201) has the function of collecting light reflected by a measured object or light emitted by a transmitter and enabling the light to be converged on a light receiving surface of the photosensitive element (203), and the optical filter (202) has the function of filtering light in a visible light wavelength range, only allowing near infrared light to pass through and eliminating visible light interference;
the signal processing unit (30) is connected with the light receiving unit (20) through electrodes, and the signal processing unit (30) amplifies and processes the electric signals output by the photosensitive element (203) into standard signals capable of communicating with the outside of the sensor.
2. A photosensor having a dual emission wavelength light source design according to claim 1 wherein:
the dual-wavelength emission light source (102) comprises a visible light wavelength light source (104) and a near infrared wavelength light source (105), and the visible light wavelength light source (104) and the near infrared wavelength light source (105) adopt independent light emitting chips to emit light.
3. The photosensor with dual emission wavelength light source design of claim 2, wherein the visible light wavelength light source (104) emits visible light using a red light emitting chip and the near infrared wavelength light source (105) emits near infrared light using an infrared light emitting chip; the infrared light-emitting chip is close to one side of the emission lens (103), the red light-emitting chip is arranged on the other side, the diameter of the red light-emitting chip is larger than that of the infrared light-emitting chip, the beam axes of the two light-emitting chips are coincided, and the distance between the center of the red light-emitting chip and the center of the infrared light-emitting chip is smaller than 5mm.
4. A photosensor having a dual emission wavelength light source design as claimed in claim 2 wherein: the diameter of the red light emitting chip is D1, the diameter of the infrared light emitting chip is D2, the diameter of the transmitting lens (103) is D3, and the transmitting lens has the function of converging light emitted by a light source according to the use scene so that the energy of light beams is concentrated in the range needing to be detected; wherein D1, D2 and D3 satisfy the following conditions:
d1 is less than or equal to D3/10, because the light-emitting chip is regarded as a point light source when the lens is designed, wherein the diameter of the light source must be less than 1/10 of the lens;
d2 is more than or equal to 10 mu m, which is used for ensuring that the intensity of infrared light emitted by the infrared light-emitting chip is enough to detect an object, and if the diameter of the light-emitting chip is smaller than the value, the sensor cannot work normally because the signal received by the sensor receiving unit is too weak, namely the radiation flux emitted by the light source is insufficient;
D1-D2 is more than or equal to 2 mu m, and if the area of the red light emitting chip is too small, red light spots cannot be observed;
d1 The range of D2 and D3 is limited to the photoelectric sensor in practical use, and the distance between the light source light-emitting chip and the central point of the lens in the photoelectric sensor structure is in the range of 2-30 mm.
5. A photosensor having a dual emission wavelength light source design as claimed in claim 2 wherein: the design of the emission lens (103) should follow f Red light ＜f Design of ＜f Infrared ray Wherein f is Red light Is the focal length of the red light emitting chip, f Design of Is the focal length of the emitting end lens (103), f Infrared ray Is the focal length of the infrared light emitting chip;
the focal length formula of the transmitting end lens (103) is as follows:
Figure FDA0003849167280000031
n is the refractive index of the glass, d is the central thickness of the lens, f is the focal length, r is the spherical radius of the lens, and the focal lengths are different because the propagation speeds of different wavelengths in the glass are different and the refractive indexes are also different, namely the focal lengths of the same lens are different under different wavelengths; according to the Cauchy's formula, the longer the wavelength, the smaller the refractive index; according to a lens focal length formula, the smaller the refractive index is, the longer the focal length is;
the relationship between the vertical axis magnification β and the focal length f is that, where x is the distance of the image
Figure FDA0003849167280000032
In order to ensure that the centers of light spots of the visible light wavelength light source (104) and the near infrared wavelength light source (105) are superposed after light passes through the lens, and simultaneously, the light spot ranges are reduced to the greatest extent,therefore, the design requirement f of the emission end lens (103) Red light ＜f Design of ＜f Infrared ray 。
CN202211134243.5A 2022-09-16 2022-09-16 Photoelectric sensor with double-emission-wavelength light source design Pending CN115615541A (en)

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