CN114527140A - Transparent object dust and foreign matter detection system based on TOF principle - Google Patents

Abstract

The invention discloses a transparent object dust and foreign matter detection system based on TOF principle, which comprises a transmitting end, a receiving end, an image signal processor and a crystal oscillator, wherein the distance measurement method adopted by the system is an indirect distance measurement method, the transmitting end adopts a laser driving technology and provides encodable narrow pulse laser, the transmitting end adopts a multi-pulse accumulation mode to realize target distance and signal intensity encoding, the receiving end decodes the target distance through image gray scale, and the receiving end performs target detection and identification through fusing a gray scale image and a distance image; the active light source reduces the dependence of the detection system on the detection environment; the implementation is simple, and the peripheral software and hardware requirements are low; the detection distance precision of dust and foreign matters of the transparent object is improved.

Description

Transparent object dust and foreign matter detection system based on TOF principle

Technical Field

The invention relates to the technical field of foreign matter detection, in particular to a transparent object dust and foreign matter detection system based on a TOF principle.

Background

Foreign substances may be generated for various reasons in a manufacturing process of a transparent object, a packaging process, a pattern forming process using the same, and the like. At present, in the fields of medicine, beverage and the like, when foreign matters are detected in liquid products such as transparent and semitransparent medicines, infusion bottles, oral liquid and the like, the situation that the foreign matters are mixed in by accident often occurs, and the physical or mental injury is caused when a consumer uses or eats the medicines or foods containing the foreign matters. The foreign matter detection system can observe hard foreign matters in food on one hand, can also identify product defects such as package cracks, bubbles, content defects, surface foreign matter adhesion and the like on the other hand, detect the loss and defective products of the packaged products and realize complete finished product detection.

The existing scheme for detecting dust and foreign matters on the surface of a transparent object is to use a common image sensor and a related algorithm to identify the dust and the foreign matters attached to the surface of the transparent object (such as glass, acrylic and the like), but the method has poor performance and low distance resolution on the transparent object and cannot be used even in strong sunlight (outdoors).

For example, chinese patent CN107957395B, published 2020, 7/3, is a detection device for foreign matter in transparent/translucent products, and relates to the technical field of analysis and measurement control. The invention relates to a detection device for foreign matters in transparent/semitransparent products, which comprises: an illumination system for providing illumination to a foreign object, the illumination system comprising a light source, the light source being a short wave infrared light source; the image acquisition system is used for acquiring a polarization image of the illuminated foreign object target and comprises a short-wave infrared polarization camera; and the data processing system is used for fusing the collected polarization image data to finish the analysis of the multispectral polarization characteristics of the foreign object target. The invention can overcome the defects of low efficiency and high false detection rate of the current artificial light detection and visible light imaging detection, and meets the requirements of various fields on the detection of foreign matters in transparent/semitransparent products. The method has the problems of low distance resolution and incapability of using under strong sunlight.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the existing detection system for the dust and foreign matters on the surface of the transparent object has the technical problems of low distance resolution and poor detection reliability. A transparent object dust foreign matter detection system based on TOF principle having high distance resolution and high reliability is provided.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the utility model provides a transparent object dust foreign matter detecting system based on TOF principle, includes transmitting terminal, receiving terminal, image signal processor and crystal oscillator, crystal oscillator with image signal processor connects, the receiving terminal pass through image sensor with image signal processor connects, image signal processor pass through the light source driver with the transmitting terminal is connected.

The detection system comprises a hardware module, wherein the hardware module mainly comprises an optical LENS (LENS), a CCD/CMOS Image Sensor (Image Sensor), an Image Signal Processor (TOF Signal Processor), a Crystal oscillator (Crystal), a 940nm infrared light source (VCSEL), a light source Driver (Driver) and the like.

Preferably, the receiving end comprises a TOF sensor, a lens base, an optical filter, a lens and a receiving cover plate; the transmitting end comprises a VCSEL laser, a light homogenizing sheet and a transmitting cover plate.

The detection system also comprises an optical module, the transmitting end comprises a VCSEL laser and a light homogenizing sheet, and a cover plate (the light homogenizing sheet and the cover plate can be combined into a whole); the receiving end comprises a TOF sensor, a lens base, a filter, a lens and a cover plate (the cover plate may not be arranged, and the lens is directly exposed). The transmitting end and the receiving end need to be optically isolated so as to ensure that the receiving end is not influenced by stray light.

Preferably, the system detects the detected object through the transmitting end and the receiving end, and the detected object detection process comprises the following steps: emitting light by a VCSEL laser; irradiating the surface of the measured object after passing through a light homogenizing sheet and a cover plate; if dust or foreign matters exist on the surface of the measured object, the light rays can be reflected to the TOF sensor; and the TOF sensor receives photons, converts the photons into electrons after photoelectric conversion, and performs depth data settlement and data transmission.

The device mainly comprises a light source part and a TOF sensor part. A940 nm active light source is arranged in the device and irradiates the surface of a measured object after passing through a light homogenizing sheet and a cover plate, if dust or foreign matters exist on the surface of the measured object, light can be reflected to a TOF sensor, and the sensor receives photons and converts the photons into electrons after photoelectric conversion to perform depth data settlement and data transmission.

Preferably, the image signal processor performs a contrast analysis according to the received data to determine whether dust and foreign matter exist, and the contrast analysis process includes: if the difference value of the actual testing distance and the set distance parameter is smaller than the contrast value a cm, judging that dust or foreign matters exist at the current position and outputting corresponding image information; and if the difference value of the actual testing distance and the set distance parameter is more than or equal to the contrast value a cm, discarding the current data and not outputting the image information.

Wherein a can be taken as 1, and the information such as whether dust and foreign matter exist or not, the size of the dust and the like is accurately judged after comparison of set distance parameters, and the set distance parameters need to be determined according to the actual installation position, namely the actual installation distance between the detected transparent object and the detection device.

Preferably, the process of detecting the transparent object foreign matter by the system comprises the following steps:

fixing the installation position of the detection device;

determining a distance parameter;

calibrating the distance, if the distance does not meet the requirement, reselecting the installation position of the detection device, and if the distance meets the requirement, emitting a light source;

receiving photons;

performing photoelectric conversion;

calculating the depth value;

carrying out gray level depth fusion;

comparing the distance data, judging a difference value, discarding the current data if the difference value is greater than or equal to a comparison value a, and determining the sizes of dust and pollutants if the difference value is less than the comparison value a;

the foreign matter image is saved and output.

The light source that this device used is 940nm wavelength's infrared VCSEL, and VCSEL has advantages such as high output and high conversion efficiency, and the range finding mode that this device adopted is indirect range finding method (PTOF), uses narrow pulse width and degree of depth grey level to fuse the technique, can detect information such as dust or foreign matter on the measured object surface fast effectively.

Preferably, the depth value calculation formula is:

wherein Distance is the calculated depth value,

c is the speed of light, i.e. the propagation speed of light or electromagnetic waves in a vacuum or medium, f_modIs the modulation frequency of the emitting light source.

Depth data can be calculated by a formula, and an effective distance value and a point cloud picture can be obtained after a series of fusion is carried out according to the depth and the gray value.

Preferably, the process of performing grayscale depth fusion includes:

acquiring image frames of high-low power staggered exposure by setting high-low power exposure parameters;

performing pixel statistical classification on the obtained image frames, and fusing the depth images and the gray images in the obtained high and low power image frames respectively according to statistical information;

performing high-low power fusion on the depth map according to the linear area range of the gray value of each pixel point corresponding to the high-low power image frame;

the gray level image fusion comprises proportionally fusing high and low image frames in an unexposed area; fusing the high-power overexposure area by proportionally replacing the gray value of the low-power image with the gray value of the high-power overexposure area according to the high-power gray scale and low-power gray scale proportional relation;

and carrying out nonlinear transformation and image optimization on the fused gray-scale image to obtain a final fused gray-scale image.

Data acquisition of an object to be detected is completed through a transmitting end and a receiving end, and the transmitting end adopts a laser driving technology and provides encodable narrow-pulse laser; the transmitting end adopts a multi-pulse accumulation mode to realize target distance and signal intensity coding; the receiving end decodes the target distance through the image gray scale (signal intensity); and the receiving end carries out target detection and identification by fusing the gray level image and the distance image.

The substantial effects of the invention are as follows: the invention comprises a transmitting end, a receiving end, an image signal processor and a crystal oscillator, wherein the adopted distance measuring method is an indirect distance measuring method, the transmitting end adopts a laser driving technology and provides encodable narrow-pulse laser, the transmitting end adopts a multi-pulse accumulation mode to realize target distance and signal intensity encoding, the receiving end carries out target distance decoding through image gray scale, and the receiving end carries out target detection and identification through fusing a gray scale image and a distance image; the active light source reduces the dependence of the detection system on the detection environment; the implementation is simple, and the peripheral software and hardware requirements are low; the detection distance precision of the dust and foreign matter of the transparent object is improved.

Drawings

FIG. 1 is a schematic composition diagram of the present embodiment;

FIG. 2 is a schematic diagram illustrating the detection principle of the present embodiment;

FIG. 3 is a schematic diagram illustrating a detection step according to the present embodiment;

FIG. 4 is a schematic view of TOF principle of the present embodiment;

fig. 5 is a schematic diagram illustrating a TOF depth value calculation principle of the present embodiment.

Wherein: 1. the device comprises a transmitting end, 2, a receiving end, 3, an image signal processor, 4, a crystal oscillator, 5, an image sensor, 6, a light source driver, 7, a TOF sensor, 8, a lens base, 9, a light filter, 10, a lens, 11, a receiving cover plate, 12, a VCSEL laser, 13, a light homogenizing plate, 14 and a transmitting cover plate.

Detailed Description

The following provides a more detailed description of the present invention, with reference to the accompanying drawings.

A transparent object dust and foreign matter detection system based on TOF principle is disclosed, as shown in figure 1 and figure 2, and comprises a transmitting end 1, a receiving end 2, an image signal processor 3 and a crystal oscillator 4, wherein the distance between an object to be detected and the device is d, and the receiving end 2 comprises a TOF sensor 7, a lens base 8, an optical filter 9, a lens 10 and a receiving cover plate 11; the transmitting end 1 comprises a VCSEL laser 12, an integrator 13 and a transmitting cover plate 14. The crystal oscillator 4 is connected with the image signal processor 3, the receiving terminal 2 is connected with the image signal processor 3 through the image sensor 5, and the image signal processor 3 is connected with the transmitting terminal 1 through the light source driver 6. The detection system comprises a hardware module, and the hardware module mainly comprises an optical LENS 10(LENS), a CCD/CMOS Image Sensor 5(Image Sensor), an Image Signal Processor 3(TOF Signal Processor), a Crystal oscillator 4(Crystal), a 940nm infrared light source (VCSEL), a light source Driver 6(Driver), and the like. The detection system also comprises an optical module, the transmitting end 1 comprises a VCSEL laser 12, a light homogenizing sheet 13 and a cover plate (the light homogenizing sheet 13 and the cover plate can be combined into a whole); the receiving end 2 comprises a TOF sensor 7, a lens base 8, a filter 9, a lens 10 and a cover plate (the cover plate may not be provided, and the lens 10 is directly exposed). The transmitting end 1 and the receiving end 2 need to be optically isolated to ensure that the receiving end 2 is not affected by stray light.

In the embodiment, data acquisition of an object to be detected is completed through a transmitting terminal 1 and a receiving terminal 2, and the transmitting terminal 1 adopts a self-grinding laser driving technology to provide encodable narrow-pulse laser; the transmitting terminal 1 adopts a multi-pulse accumulation mode to realize target distance and signal intensity coding; the receiving end 2 decodes the target distance through the image gray scale (signal intensity); the receiving end 2 performs target detection and identification by fusing the gray level image and the distance image.

The present embodiment mainly includes a light source section and a TOF sensor section. A940 nm active light source is arranged in the device, irradiates the surface of a measured object after passing through the light homogenizing sheet 13 and the cover plate, if dust or foreign matters exist on the surface of the measured object, light can be reflected to the TOF sensor, and the sensor receives photons and converts the photons into electrons after photoelectric conversion to perform depth data settlement and data transmission. And comparing the specific distance parameters through an algorithm level, and then accurately judging whether dust and foreign matters exist and the size and other information of the dust and foreign matters. And if the difference value between the actual test distance and the specific distance parameter is less than 1cm, judging that dust or foreign matters exist at the current position and outputting corresponding image information. And if the difference value between the actual testing distance and the specific distance parameter is more than or equal to 1cm, discarding the current data and not outputting the image information. The specific distance parameter is determined according to the actual installation position, namely the actual installation distance between the detected transparent object and the detection device. The system for detecting the foreign matter in the transparent object comprises the following steps as shown in fig. 3:

fixing the installation position of the detection device;

determining a distance parameter;

calibrating the distance, if the distance does not meet the requirement, reselecting the installation position of the detection device, and if the distance meets the requirement, emitting a light source;

receiving photons; performing photoelectric conversion; calculating the depth value; carrying out gray level depth fusion;

comparing the distance data, judging a difference value, if the difference value is greater than or equal to a comparison value a, and a can be 1cm, discarding the current data, and if the difference value is less than the comparison value a, determining the sizes of dust and pollutants;

the foreign matter image is saved and output.

The light source used by the device is an infrared VCSEL with 940nm wavelength, the VCSEL has the advantages of high output power, high conversion efficiency and the like, the distance measurement mode adopted by the device is an indirect distance measurement method (PTOF), and information such as dust or foreign matters on the surface of a measured object can be quickly and effectively detected by using a narrow pulse width and depth gray level fusion technology.

The TOF schematic block diagram is shown in fig. 4, and a method of measuring phase offset is adopted, that is, the phase difference between the transmitted square wave and the received square wave is used to calculate the depth information of the measured object. The TOF ranging principle is shown in fig. 5, and the depth value calculation formula is:

wherein Distance is the calculated depth value,

C1-C4 are offset phase waveforms of 0, 180, 90 and 270 degrees of the light source transmission signal, respectively, for the time difference of the transmission signal and the reception signal. Depth data can be calculated by a formula, and an effective distance value and a point cloud picture can be obtained after a series of fusion is carried out according to the depth and the gray value. The distance formula derivation process is as follows:

s(t)＝a·(1+sin(2πft))

in the formula, s (T) is a transmitted sinusoidal signal, the amplitude is a, the modulation frequency is f, Δ T is the receiving time delay, r (T) is the received signal, A is the amplitude after attenuation, B is the signal intensity offset, the four sampling time intervals are equal and are all T/4, Δ φ is the phase offset of transmission and reception, and d is the distance between an object and a depth camera.

The depth data can be calculated by the graph formula, and an effective distance value and a point cloud graph are obtained after a series of fusion is carried out according to the depth and the gray value. The fusion process is as follows: the method comprises the steps of obtaining image frames of high-low power staggered exposure by setting high-low power exposure parameters, carrying out pixel statistical classification on the obtained image frames, and fusing a depth map and a gray map in the obtained high-low power image frames respectively according to statistical information. And performing high-low power fusion on the depth image according to the linear area range of the gray value of each pixel point corresponding to the high-low power image frame. The gray level image fusion is divided into the steps that high and low image frames in an unexposed area are fused in proportion; and fusing the high-power overexposure area by proportionally replacing the gray value of the low-power image with the gray value of the high-power overexposure area according to the high-power gray scale and low-power gray scale proportional relation in the high-power parameter overexposure area. And carrying out nonlinear transformation and image optimization on the fused gray-scale image to obtain a final fused gray-scale image.

The terms referred to herein are explained as follows:

TOF Time of flight ranging Time of flight method

VCSEL Vertical resonant Cavity Surface Emitting Laser

CCD, a solid-state electronic device charge-coupled device for detecting light to realize storage and transfer of charge information

CMOS Complementary Metal Oxide Semiconductor (CMOS) Semiconductor

TOF is an abbreviation of Time of flight, interpreted as the meaning of Time of flight. Time-of-flight techniques are understood in a broad sense to be techniques for further understanding certain properties of ions or media by measuring the time it takes for an object, particle or wave to fly a certain distance in a fixed medium (both medium/distance/time being known or measurable). PTOF is an indirect TOF measurement method. The TOF technology that this embodiment had applied exclusive low duty cycle pulse modulation and narrow pulse laser technique is applied to transparent object dust foreign matter and detects, can be applied to car windshield's dust and foreign matter and detect, can effective early warning glass cleanliness, in time cooperates equipment such as windshield wiper to clear up and can effectively reduce the in-process occurence of failure probability of traveling.

The present example has solar resistance: the low duty ratio laser pulse is combined with the special principle of optical amber, so that the influence of sunlight can be effectively reduced; anti-interference performance: the special working time sequence of the laser and the sensor can accommodate the operation without interference among a plurality of devices; high precision: the transverse direction can provide angular resolution better than 0.1 degrees, and the longitudinal direction can provide cm-level distance resolution, and has the advantages of high reliability, low cost and the like.

The above examples only show some embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.

Claims (7)

1. The transparent object dust and foreign matter detection system based on the TOF principle is characterized by comprising an emitting end (1), a receiving end (2), an image signal processor (3) and a crystal oscillator (4), wherein the crystal oscillator (4) is connected with the image signal processor (3), the receiving end (2) is connected with the image signal processor (3) through an image sensor (5), and the image signal processor (3) is connected with the emitting end (1) through a light source driver (6).

2. A transparent object dust and foreign matter detection system based on TOF principle according to claim 1 wherein the receiving end (2) comprises a TOF sensor (7), a lens holder (8), a filter (9), a lens (10) and a receiving cover plate (11); the emitting end (1) comprises a VCSEL laser (12), a dodging sheet (13) and an emitting cover plate (14).

3. A transparent object dust and foreign matter detection system based on TOF principle according to claim 1 or 2, wherein the object detection is performed by the transmitting end (1) and the receiving end (2), and the object detection process comprises: emitting light by a VCSEL laser (12); after passing through a light homogenizing sheet (13) and a cover plate, irradiating the surface of the measured object; if dust or foreign matters exist on the surface of the measured object, the light rays can be reflected to the TOF sensor; and the TOF sensor receives photons, converts the photons into electrons after photoelectric conversion, and performs depth data settlement and data transmission.

4. A transparent object dust and foreign substance detection system based on TOF principle according to claim 1 wherein the image signal processor (3) performs a comparative analysis based on the received data to determine whether dust and foreign substance are present, the comparative analysis comprising: if the difference value of the actual testing distance and the set distance parameter is smaller than the contrast value a cm, judging that dust or foreign matters exist at the current position and outputting corresponding image information; and if the difference value of the actual testing distance and the set distance parameter is more than or equal to the contrast value a cm, discarding the current data and not outputting the image information.

5. The transparent object dust and foreign substance detection system based on TOF principle as claimed in claim 1 or 4 wherein the system performing transparent object foreign substance detection process comprises the steps of:

fixing the installation position of the detection device;

determining a distance parameter;

calibrating the distance, if the distance does not meet the requirement, reselecting the installation position of the detection device, and if the distance meets the requirement, emitting a light source;

receiving photons;

performing photoelectric conversion;

calculating the depth value;

carrying out gray level depth fusion;

comparing the distance data, judging a difference value, discarding the current data if the difference value is greater than or equal to a comparison value a, and determining the sizes of dust and pollutants if the difference value is less than the comparison value a;

the foreign matter image is saved and output.

6. The transparent object dust and foreign matter detection system based on the TOF principle according to claim 5, wherein the depth value is calculated by the formula:

wherein, Distance is the calculated depth value, c is the angle of the light source emission signal,

is the time difference between the transmitted signal and the received signal.

7. The transparent object dust foreign object detection system based on the TOF principle as recited in claim 5, wherein the process of performing gray scale depth fusion comprises:

acquiring image frames of high-low power staggered exposure by setting high-low power exposure parameters;

performing pixel statistical classification on the obtained image frames, and fusing the depth images and the gray images in the obtained high and low power image frames respectively according to statistical information;

performing high-low power fusion on the depth map according to the linear area range of the gray value of each pixel point corresponding to the high-low power image frame;

the gray level image fusion comprises proportionally fusing high and low image frames in an unexposed area; fusing the high-power overexposure area by proportionally replacing the gray value of the low-power image with the gray value of the high-power overexposure area according to the high-power gray scale and low-power gray scale proportional relation;

and carrying out nonlinear transformation and image optimization on the fused gray-scale image to obtain a final fused gray-scale image.

Images