Linear light spot photoelectric sensor for hollow object detection

Abstract

The invention discloses a linear light spot photoelectric sensor for hollow object detection. The linear light spot photoelectric sensor comprises a sensor shell; the transmitting unit is arranged in the sensor shell and comprises a point light source LED and a transmitting lens; the lens optical filter covers the transmitting window and the receiving window of the sensor shell; the receiving unit is arranged in the sensor shell and comprises an asymmetric double-unit receiving tube and a receiving lens; light reflected by a detected object is converted into parallel light through the lens optical filter, and the parallel light passes through the receiving lens and is collected in a receiving area of the asymmetric double-unit receiving tube; and the circuit board is used for signal processing and is electrically connected with the transmitting unit and the receiving unit. The distance of the sensor is set by selecting the asymmetric double-unit receiving tube and the adjusting lens, so that the detection blind area of the sensor is reduced, zero detection blind area is realized, and the adaptability and the use reliability of the sensor are improved.

Description

Technical Field

[0001] The invention relates to the technical field of electronic manufacturing detection, and in particular to a line spot photoelectric sensor for hollow object detection. Background Art

[0002] In modern industrial production, photoelectric sensors are widely used in various production lines due to their advantages such as non-contact measurement, high precision, and fast response. Especially in the electronics manufacturing industry, the quality control of circuit boards and their hollow structural parts is a key link, and photoelectric sensors play an important role in this process. However, traditional point light source detection technology often finds it difficult to achieve ideal detection accuracy and efficiency when faced with complex circuit layouts and fine pore structures. At the same time, the detection blind area is large and the performance is unstable.

[0003] To solve these problems, existing solutions mainly adopt a large spot light source to improve light concentration and uniformity. At the same time, a symmetrical dual-receiver photosensitive element is used to improve light detection capabilities and reduce blind spots.

[0004] Disadvantages of existing technology

[0005] 1) The existing light source and receiver design cannot completely eliminate the problem of uneven light distribution, which may affect the accuracy of detection. The brightness of the line spot is not enough, and the material and surface roughness of different detection objects will affect the reflection of light, increase the complexity of detection, and affect the sensitivity of measurement.

[0006] 2) Although the background suppression function is achieved by using symmetrical dual-receiver photosensors, the reduction of blind areas is not obvious.

[0007] 3) In complex environments, such as changes in external light, background interference, and close side-by-side installation, the sensor has weak anti-interference capabilities and is prone to malfunction. Summary of the invention

[0008] The present invention provides a line spot photoelectric sensor for hollow object detection. Through optimized optical path design, a point light source is accurately converted into a line spot. The sensor is particularly suitable for the detection of high-density circuit boards and components with complex hollow structures, so as to solve the problems existing in the prior art.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A line spot photoelectric sensor for hollow object detection, comprising:

[0011] Sensor housing;

[0012] The transmitting unit is arranged in the sensor housing, and the transmitting unit includes a point light source LED and a transmitting lens; the point light source LED transmits a pulse light signal, and the parallelism of the light is adjusted by the transmitting lens to obtain a parallel light beam.

[0013] A lens filter covering the transmitting window and the receiving window of the sensor housing is used to convert the parallel light beam into a line light spot and project it onto the object to be detected;

[0014] A receiving unit is arranged in the sensor housing, and the receiving unit includes an asymmetric double-unit receiving tube and a receiving lens; the light reflected by the detected object is converted into parallel light through a lens filter, passes through the receiving lens, and is collected in a receiving area of ​​the asymmetric double-unit receiving tube;

[0015] A circuit board for signal processing, wherein the circuit board is electrically connected to the transmitting unit and the receiving unit.

[0016] A further improvement of the present invention is that the asymmetric dual-unit receiving tube includes a first receiving area and a second receiving area, the receiving area of ​​the first receiving area is larger than the receiving area of ​​the second receiving area, wherein: the first receiving area is used to receive reflected light signals from a farther distance, and the second receiving area is used to receive reflected light signals from a closer distance, so as to realize the detection of objects at different distances.

[0017] A further improvement of the present invention is that a detection distance adjustment knob is provided on the sensor housing for adjusting the position of the receiving lens.

[0018] A further improvement of the present invention is that a frame baffle is provided inside the sensor housing to isolate the transmitting unit from the receiving unit to prevent stray light crosstalk; a narrow-band filter is provided in the receiving unit to filter out stray interference light not emitted by itself.

[0019] A further improvement of the present invention is that the circuit board comprises:

[0020] Power module;

[0021] Transmitter module, used to drive the point light source LED to transmit in pulse modulation mode;

[0022] A receiving module, used for receiving the signal of the asymmetric dual-unit receiving tube;

[0023] MCU controller for signal processing;

[0024] Display module, used to display the working status of the system;

[0025] The output module is used to output the detection signal.

[0026] A further improvement of the present invention is that when at least two line spot photoelectric sensors are installed side by side, the emission period of each line spot photoelectric sensor is controlled by a frequency conversion method so that the emission periods of each line spot photoelectric sensor are staggered with each other, thereby preventing the same-frequency light crosstalk generated when multiple line spot photoelectric sensors are installed side by side.

[0027] A further improvement of the present invention is that the line spot photoelectric sensor adopts a high-frequency light suppression algorithm, samples the interference signal through a comparator and an ADC, and when the interference signal is collected, the transmitting unit stops transmitting, and a receiving unit is used to detect the high-frequency interference signal period; when a high-frequency interference signal exists, the rising edge of the high-frequency interference signal is captured, and the transmitting unit is controlled to transmit at this time, and the transmitted light signal is superimposed on the rising edge of the high-frequency interference signal.

[0028] A further improvement of the present invention is that the lens filter includes a group of micro lenses for adjusting the shape and direction of the light spot.

[0029] The beneficial effects of the present invention include:

[0030] 1) The present invention realizes adjustment of the point light source through special light path design and optical element arrangement, and lens combination, converts the point light source into a line light spot, improves the concentration and uniformity of the light, and improves the measurement accuracy of the hollow object.

[0031] 2) By selecting an asymmetric dual-unit receiving tube and adjusting the lens for sensor distance setting, the sensor's detection blind area is reduced, zero blind area detection is achieved, and the sensor's adaptability and reliability are improved.

[0032] 3) The present invention adopts modulation technology, filtering technology, side-by-side installation algorithm, high-frequency light suppression algorithm, etc. to improve the anti-interference ability. Especially in a strong interference environment, the anti-interference ability of the present invention is better than the existing technology and can provide more accurate detection results.

[0033] 4) The present invention can realize a point-like light spot photoelectric sensor by modifying the filter design without changing the main structure of the existing product, thereby increasing the versatility of materials of major components such as the housing, frame, and aspherical lens, while optimizing power consumption and cost to meet the needs of specific application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a line spot photoelectric sensor for hollow object detection of the present invention;

[0035] Figure 2 The circuit schematic diagram of the line spot photoelectric sensor for hollow object detection of the present invention;

[0036] Figure 3It is a principle schematic diagram of the line spot photoelectric sensor for hollow object detection of the present invention;

[0037] Figure 4 is a schematic diagram of a transmitting unit in the present invention;

[0038] Figure 5 Schematic diagram of the line spot. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0040] It should be noted that the illustrations provided in the following embodiments are only used to illustrate the basic concept of the present invention in a schematic manner, and thus the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0041] An embodiment of the present invention provides a line spot photoelectric sensor for hollow object detection. The main characteristics of the line spot photoelectric sensor include:

[0042] (1) Optimization of the transmitting unit and receiving unit: A small light spot light source is used, and the concentration and uniformity of light are improved through special light path design and optical component arrangement. Asymmetric dual-unit receiving tubes are used to optimize the PCB layout, improve light detection capabilities, reduce blind areas, and thus improve the detection accuracy of hollow objects.

[0043] 2) Optical path design and optical structure optimization: Design the optical structure of the lens filter, adjust the lens position, improve the length and width of the light, optimize the focus and uniformity, and enhance the detection ability of hollow objects.

[0044] 3) Signal processing and algorithm optimization to improve anti-interference technology: Modulation technology, filtering technology, side-by-side installation algorithm, high-frequency light suppression algorithm, etc. are used to improve anti-interference capabilities.

[0045] 4) System integration and optimization: Integrate light source, optical system, signal processing circuit, and output control to achieve high integration and miniaturization; optimize the mechanical structure and installation method of the sensor to improve the reliability and stability of detection; optimize power consumption and cost to meet the needs of specific application scenarios.

[0046] like Figure 1 , Figure 3 As shown, the line spot photoelectric sensor for hollow object detection of the present invention specifically includes: a sensor housing 10 , a transmitting unit, a receiving unit and a circuit board 30 .

[0047] The sensor housing 10 has a mounting hole 13 for fixing the sensor on the detection device. The sensor housing 10 is provided with a transmitting window 11 and a receiving window 12 adjacent to each other.

[0048] The transmitting unit is arranged inside the sensor housing 10. The transmitting unit comprises a point light source LED 14 and a transmitting lens 15; the point light source LED 14 transmits a pulse light signal, and the light is parallelized by the transmitting lens to obtain a parallel light beam.

[0049] The lens filter 16 covering the transmitting window 11 and the receiving window 12 of the sensor housing 10 is used to convert the parallel light beam into a line light spot 40 and project it onto the detected object (hollow object 41);

[0050] The receiving unit is arranged in the sensor housing 10. The receiving unit comprises an asymmetric dual-unit receiving tube 18 and a receiving lens 19; the light reflected by the detected object is converted into parallel light through the lens filter, passes through the receiving lens 19, and is collected in the receiving area of ​​the asymmetric dual-unit receiving tube.

[0051] A circuit board 30 for signal processing, the circuit board 30 is electrically connected to the transmitting unit and the receiving unit. The circuit board 30 (PCBA) is connected to a cable 31, and the cable 31 is used for power supply and signal output.

[0052] like Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown, the working principle of the line spot photoelectric sensor for hollow object detection in this embodiment is as follows: the point light source LED 14 emits a pulse light signal, which is arranged by the emitting lens 15 to obtain a parallel light beam, and the lens filter 16 converts the parallel light beam into a line spot 40 (such as Figure 5 As shown), it is projected onto the hollow object 41 to be detected; the light irradiated on the hollow part cannot be reflected, and the light irradiated on the non-hollow area is reflected. The reflected light is converted into parallel light through the lens filter 16, passes through the receiving lens 19, and is collected in the receiving area of ​​the asymmetric dual-unit receiving tube 18.

[0053] The asymmetric dual-unit receiving tube 18 has two receiving areas, which respectively convert the received optical signal into two signals, one of which is a short-distance signal ( Figure 3The signal detected by the red mark area in the middle), and the other signal is a long-distance signal ( Figure 3 The circuit board 30 detects the hollow object by differentially amplifying and AD collecting the two signals, and the MCU controller on the circuit board 30 makes signal judgment.

[0054] The logic of signal judgment is: the difference between the long-distance signal (yellow mark) and the short-distance signal (red mark) is obtained by differential amplification; when the signal strength of the long-distance signal (yellow mark) of the optical signal is greater than the signal strength of the short-distance signal (red mark), the difference is greater than the reference, and it is determined that there is no target (hollow object) in the detection area; otherwise (the difference is less than the reference), it is determined that there is a target, and the detection of the presence or absence of the detection object is completed. In this embodiment, an asymmetric dual-unit receiving tube 18 is used to achieve background suppression and improve detection accuracy.

[0055] In other embodiments, when the MCU controller uses a simple benchmark to judge the difference, it is easy to cause misjudgment when the difference is near the benchmark, causing the output result of the sensor to jitter; therefore, the hysteresis method is used to eliminate the critical value output jump when the difference is near the benchmark, making the output of the sensor more stable.

[0056] The detection signals obtained by the asymmetric dual-unit receiving tube 18 for objects at different distances are processed differentially, and the difference values ​​obtained are in different ranges to distinguish objects at different distances, thereby achieving background suppression and detection of objects at different distances.

[0057] In this embodiment, the principle block diagram of the circuit on the circuit board 30 is as follows: Figure 2 As shown, it includes: power module, transmitting module, receiving module, MCU controller, display module, output module. Circuit board 30 controls the work of transmitting unit, receiving unit, display module, and output module. A differential amplifier is also integrated thereon. Circuit board 30 is used to analyze and judge, control the output and indicate the circuit response detection results, thereby completing the entire detection process of the photoelectric sensor. The specific functions of each module are:

[0058] Power module: Provides power to the entire system. By selecting low-power, low-voltage dropout devices, the module has higher efficiency and lower temperature rise.

[0059] Transmitting unit: cooperates with the MCU controller to drive the point light source LED 14 to perform pulse modulation transmission.

[0060] Receiving unit: Its asymmetric dual-unit receiving tube 18 cooperates with the optical structure and adopts the principle of triangulation to achieve background suppression.

[0061] MCU controller: used to process various data and coordinate the work of various modules.

[0062] Display module: used to indicate the system working status, equipped with a power indicator light (green) and an output status indicator light (yellow).

[0063] Output module: used to output system signals to other control parts and provide overvoltage and overcurrent protection functions.

[0064] like Figure 1 , Figure 2 As shown, the optical solution part of the line spot photoelectric sensor for hollow object detection in this embodiment includes a point light source LED 14, a transmitting lens 15, a lens filter 16, a receiving lens 19, an asymmetric dual-unit receiving tube 18, a narrow-band filter 20, and a frame spacer 21.

[0065] The point light source LED 14 adopts a high-performance LED small light spot light source with high brightness and long life characteristics to ensure stable light source output. By adjusting the power of the light source, the brightness and effect of the light spot can be changed.

[0066] The asymmetric dual-unit receiving tube 18 integrates two DPs (photodiodes), which correspond to the first receiving area (yellow) and the second receiving area (red), respectively, wherein the first receiving area is used to receive reflected light signals from a longer distance, and the second receiving area is used to receive reflected light signals from a closer distance. The first receiving area and the second receiving area are distributed along the first direction, and the point light source LED 14 is also located in the first direction; compared with the second receiving area, the first receiving area is closer to the point light source LED 14. In the first direction, the length ratio of the first receiving area to the second receiving area is 1:2 to 1:4; the width of the first receiving area is equal to that of the second receiving area.

[0067] The light reflected from objects at different distances is focused by the receiving lens, and the energy distribution of the light spot falling on the two receiving areas of the asymmetric dual-unit receiving tube 18 is also different. After differential amplification, the signals received in the two receiving areas are converted into electrical signal intensity based on the optical information and compared with the set intensity (benchmark) to determine whether the hollow object is within the detection range, thereby achieving accurate detection of the hollow object being detected. Through the selection and design of asymmetric receiving units (indicated by yellow and red), the receiving capacity of the close-range (red) area is increased and the detection blind area is reduced.

[0068] In this embodiment, the emitting lens 15 is an aspherical lens, and the curvature and the material refractive index are accurately calculated so as to converge the light from the point light source LED 14 into a parallel light beam and improve the light intensity in the direction of the optical axis.

[0069] The lens filter 16 is designed as a group of micro lenses for finely adjusting the shape and direction of the light spot to meet the needs of hollow object detection.

[0070] The receiving lens 19 focuses the light, and the light is gathered on the asymmetric dual-unit receiving tube 18 at one focal length and converted into an electrical signal, so that the receiving circuit on the circuit board 30 (PCBA) can amplify the signal. A mechanical adjustment mechanism is designed for the receiving lens 19, which includes a frame that carries the receiving lens 19 and a detection distance adjustment knob 17 that is transmission-connected to the frame; the position of the receiving lens 19 can be adjusted by rotating the adjustment knob 17. By moving the receiving lens 19, the imaging angle can be changed, and the proportion of the received light spot reaching the asymmetric dual-unit receiving tube 18 can be changed. The sensor detection distance adjustment function is then realized in conjunction with the circuit. Due to the movement of the lens in the structure, the imaging angle of the fixed mode is changed, and the reflected light can be detected when the detection object is close to the sensor, reducing the optical blind area.

[0071] The narrowband filter 20 is located behind the receiving lens 19 and is used to filter out stray light and improve detection accuracy.

[0072] A mirror frame baffle 21 is provided inside the sensor housing 10 to isolate the transmitting unit from the receiving unit to prevent stray light crosstalk; a narrowband filter 20 is provided in the receiving unit to filter out stray interference light not emitted by the sensor itself. A mirror frame is also provided inside the sensor housing 10 to fix the optical element.

[0073] This embodiment adopts the line spot adjustment technology: the point light source LED 14 emits a central light beam, which passes through the emitting lens 15 to converge the LED point light source light into a parallel light beam, thereby increasing the light intensity in the direction of the optical axis. The parallel light beam passes through the lens filter 16 to finely adjust the shape and direction of the light spot, ensuring that the point light source is evenly converted into a line light spot 40 of the required width and intensity. The lens filter 16 is designed as a group of microlenses, which can calibrate the installation deviation of the point light source, ensure the uniform color transmission of the line light spot, and improve the detection accuracy. The material and curvature radius of the lens determine its optical performance. Through optical design and simulation, the optical lens design and material selection optimization are carried out to meet the design requirements.

[0074] The technical structure scheme of the present invention adjusts the point light spot into a line light spot 40 by optimizing the lens combination, thereby improving the uniformity of the light spot and the reliability of hollow object detection. The distance is set by adjusting the lens to improve the adjustment accuracy. The optical design is optimized to change the direction of the light path, eliminate blind spots, and improve the hollow object detection range.

[0075] When at least two line spot photoelectric sensors are installed side by side, the emission period of each line spot photoelectric sensor is controlled by frequency conversion so that the emission periods of each line spot photoelectric sensor are staggered to prevent the same frequency light crosstalk when multiple line spot photoelectric sensors are installed side by side.

[0076] In some embodiments, the transmitting unit is controlled by a timer, and when the timer of the MCU controller reaches a specified value or overflows, the transmitting unit can be controlled to drive the point light source LED 14 to emit light. In order to achieve variable frequency control of the emission cycle of each line spot photoelectric sensor, the beat timer load value and the initial count value are changed in sequence, thereby achieving variable frequency of the emission cycle, wherein each variable frequency cycle can be changed as needed to avoid interference caused by the simultaneous emission of line spot photoelectric sensors installed side by side.

[0077] In order to cope with complex environments, the technical solution of the present invention adopts a high-frequency light suppression algorithm, and the MCU controller processes the signal collected by the asymmetric dual-unit receiving tube 18 through a comparator and ADC to sample the interference signal. When collecting interference signals, the transmitting unit stops transmitting, and the receiving unit is used to detect the period of the high-frequency interference signal. When there is a high-frequency interference signal, the rising edge of the high-frequency interference signal is captured (the high-frequency interference signal usually comes from the lighting equipment, and its period is relatively stable). At this time, the transmitting unit is controlled to transmit, and the emitted light signal is superimposed on the rising edge of the high-frequency interference signal, so that the edge of the high-frequency light can reduce the influence of the detection process.

[0078] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A line spot photoelectric sensor for hollow object detection, characterized in that: include: Sensor housing; An emitting unit is arranged in the sensor housing, and the emitting unit comprises a point light source LED and an emitting lens; The point light source LED emits a pulse light signal, which is then aligned with the parallelism of the light through the emitting lens to obtain a parallel light beam. A lens filter covering the transmitting window and the receiving window of the sensor housing is used to convert the parallel light beam into a line light spot and project it onto the object to be detected; A receiving unit is arranged in the sensor housing, and the receiving unit includes an asymmetric double-unit receiving tube and a receiving lens; the light reflected by the detected object is converted into parallel light through a lens filter, passes through the receiving lens, and is collected in a receiving area of ​​the asymmetric double-unit receiving tube; A circuit board for signal processing, wherein the circuit board is electrically connected to the transmitting unit and the receiving unit.

2. The linear spot photoelectric sensor for hollow object detection according to claim 1, characterized in that: The asymmetric dual-unit receiving tube includes a first receiving area and a second receiving area, wherein the receiving area of ​​the first receiving area is larger than the receiving area of ​​the second receiving area, wherein: the first receiving area is used to receive reflected light signals from a longer distance, and the second receiving area is used to receive reflected light signals from a shorter distance, so as to realize the detection of objects at different distances.

3. The linear spot photoelectric sensor for hollow object detection according to claim 1, characterized in that: The sensor housing is provided with a detection distance adjustment knob for adjusting the position of the receiving lens.

4. The linear spot photoelectric sensor for hollow object detection according to claim 1, characterized in that: A frame partition is arranged inside the sensor housing to isolate the transmitting unit from the receiving unit to prevent stray light crosstalk; a narrow-band filter is arranged in the receiving unit to filter out stray interference light not emitted by the receiving unit.

5. The linear spot photoelectric sensor for hollow object detection according to claim 1, characterized in that: The circuit board comprises: Power module; Transmitter module, used to drive the point light source LED to transmit in pulse modulation mode; A receiving module, used for receiving the signal of the asymmetric dual-unit receiving tube; MCU controller for signal processing; Display module, used to display the working status of the system; The output module is used to output the detection signal.

6. The linear spot photoelectric sensor for hollow object detection according to claim 5, characterized in that: When at least two line spot photoelectric sensors are installed side by side, the emission period of each line spot photoelectric sensor is controlled by frequency conversion so that the emission periods of each line spot photoelectric sensor are staggered to prevent the same frequency light crosstalk when multiple line spot photoelectric sensors are installed side by side.

7. The linear spot photoelectric sensor for hollow object detection according to claim 5, characterized in that: The line spot photoelectric sensor adopts a high-frequency light suppression algorithm and samples interference signals through a comparator and an ADC. When collecting interference signals, the transmitting unit stops transmitting and uses a receiving unit to detect the high-frequency interference signal cycle. When a high-frequency interference signal exists, the rising edge of the high-frequency interference signal is captured. At this time, the transmitting unit is controlled to transmit and the transmitted light signal is superimposed on the rising edge of the high-frequency interference signal.

8. The linear spot photoelectric sensor for hollow object detection according to claim 1, characterized in that: The lens filter includes a group of micro lenses for adjusting the shape and direction of the light spot.

Images