CN118031175A

CN118031175A - Rotary LED full-angle annular lighting device

Info

Publication number: CN118031175A
Application number: CN202410127439.4A
Authority: CN
Inventors: 王狮凌; 刘�东; 郭世维; 王劭文; 孔明
Original assignee: Zhejiang University ZJU; China Jiliang University
Current assignee: Zhejiang University ZJU; China Jiliang University
Priority date: 2024-01-30
Filing date: 2024-01-30
Publication date: 2024-05-14

Abstract

The invention discloses a rotary LED full-angle annular lighting device, which comprises a hollow conductive slip ring and an outer rotor hollow motor, wherein an LED rotating frame is sleeved and fixed on the outer wall of a rotor of the outer rotor hollow motor, and three groups of collimation LED light sources are uniformly arranged on the LED rotating frame along the circumferential direction; the outer rotor hollow motor is used for realizing 360-degree rotary illumination of the region to be measured; the inner rotor of the hollow conductive slip ring is fixed, and the outer rotor is connected with the power supply line of the collimation LED light source and used for realizing the rotary coupling of the power supply of the collimation LED light source. By utilizing the invention, 360-degree annular illumination (weft direction) can be realized, uniform illumination of luminous flux at each angle can be realized, and meanwhile, the adjustable mechanism can realize illumination direction adjustment (warp direction) of a light source of 0-90 degrees, and the invention plays a key role in machine vision application involving dark field imaging.

Description

Rotary LED full-angle annular lighting device

Technical Field

The invention belongs to the field of machine vision illumination devices, and particularly relates to a rotary LED full-angle annular illumination device for dark field imaging.

Background

Surface defects of optical elements play an important role in laser damage, mechanical strength, imaging quality and long-term stability of precision optical elements. Precise detection of surface defects remains urgent, critical and extremely challenging for a long time, which can greatly aid in studying processing techniques, manufacturing quality control, understanding the relationship between laser damage and defect detection, and the like. Currently, machine vision is often used to detect surface defects of optical elements due to its objectivity, repeatability and digitization.

In the field of machine vision defect detection, a dark field imaging principle is generally adopted for detection, due to the randomness of a microstructure, surface defect morphology and distribution, a detected area is required to receive luminous fluxes from various angles, particularly scratch defects, scattered light generated by the detected area can be received by a detector to the greatest extent only when the luminous fluxes perpendicular to the detected area are received, and if an illumination angle is poor, the signal to noise ratio of a dark field imaging system is poor, so that a high-quality multi-angle illumination system is crucial for realizing accurate detection and analysis in order to prevent the occurrence of the omission phenomenon of the surface defects.

However, the conventional illumination device has many limitations in dark field imaging, and the chinese patent document with publication No. CN 111610197a uses an illumination module and an illumination adjustment module to perform the detection, so as to solve the problem that the detection results of the same defect at different positions of the sample to be detected are inconsistent due to different transmittance or reflectance at different positions of the sample to be detected to a certain extent. The chinese patent publication CN113866181a uses a plurality of annular light sources to achieve a non-illumination angle, while using an annular arrangement of light sources of different illumination brightness. However, as in the chinese patent document of publication No. CN108827971a, none of them can realize a 360-degree dead-angle-free illumination angle.

Further, conventional illumination devices have many limitations in dark field imaging, especially in the accurate detection of surface defects, micro-structures, or transparent samples. These challenges drive the need for more efficient illumination systems to better capture and analyze scattered signals. LEDs have the advantage of being a low power, high brightness light source with dimmable characteristics and long lifetime, however, conventional LED lighting systems are typically static or fixed directional, limiting the application and imaging capabilities at different angles.

Disclosure of Invention

The invention provides a rotary LED full-angle annular lighting device, provides an innovative solution for dark field scattering imaging of machine vision, can realize 360-degree annular lighting (in the weft direction) and uniform lighting of luminous flux at each angle, and simultaneously can realize 0-90-degree light source lighting direction adjustment (in the warp direction) by an adjusting mechanism, thereby playing a key role in machine vision application involving dark field imaging.

The rotary LED full-angle annular lighting device comprises a hollow conductive slip ring and an outer rotor hollow motor, wherein an LED rotating frame is sleeved and fixed on the outer wall of the rotor of the outer rotor hollow motor, and three groups of collimation LED light sources are uniformly arranged on the LED rotating frame along the circumferential direction; the outer rotor hollow motor is used for realizing 360-degree rotary illumination of the region to be measured;

the inner rotor of the hollow conductive slip ring is fixed, and the outer rotor is connected with the power supply line of the collimation LED light source and used for realizing the rotary coupling of the power supply of the collimation LED light source.

Further, three groups of collimation LED light sources are spaced at 120 degrees, each group of collimation LED light sources comprises an LED and a corresponding LED collimation lens, and the front end of each LED collimation lens is provided with an angle-adjustable reflector.

Through the LED collimating lens of plastic to improve the directionality of single beam illumination, reduce the light that reflects and get into the system, make dark field effect better. The LED light source is LED to the target position by the reflector, compared with the inclined LED adopted by the conventional annular light source LED, the structure is more compact, the LED light can be accurately guided to the target position by adjusting the reflector, and the LED light source LED has better adjustment performance.

Further, the outer side wall of the LED rotating frame and the outer rotor of the hollow conductive slip ring are respectively fixed inside the shell through corresponding bearings.

Further, the hollow conductive slip ring and the outer rotor hollow motor are hollow structures and are used for coaxially installing an imaging light path. Because the lighting device is of a complete hollow design, the design requirement on the lens is reduced, and a conventional objective lens, a telecentric lens, an industrial lens and the like can be matched with the lighting device.

Optionally, the imaging light path includes an imaging lens and an image collector arranged at the rear end of the imaging lens; and the light rays emitted by the collimation LED light source reach the region to be detected and are collected by the image collector through the imaging lens.

The calculation formula of the rotating speed a of the outer rotor hollow motor comprises the following steps:

Wherein f is the image acquisition frame rate, and n is the number of LED groups; mu is more than or equal to 1, and is a safety factor.

The luminous flux of the region to be measured is adjusted according to the requirement, and the method specifically comprises the following steps:

(1) The required luminous flux phi of the region to be measured per second, the luminous flux of a single LED light source is x, the rotating speed a of the outer rotor hollow motor is represented by the formula:

φ＝n·x·a

(2) According to the surface property and state of the detection sample, determining luminous flux through calculation, so as to control the illumination brightness and rotation speed of each LED light source, and selecting corresponding parameters;

(3) The illumination angle of the device is adjusted to a required angle according to the detection requirement, namely, the incident angle of the light source is set.

In order to ensure the brightness consistency of imaging in different directions, the brightness consistency of the LED light beams is also required to be ensured, and the following mode is adopted:

(1) Each LED light source is driven by constant current and is connected with a power supply in parallel, and square waves with certain frequency and adjustable duty ratio are generated by an output port of the singlechip;

(2) Each output port controls the brightness of one LED light source, so that the brightness of different paths of LED light beams is accurately regulated;

(3) The duty ratio of PWM waveform of the output port of the singlechip is set to 0-9 by a computer, the brightness of the corresponding LED light sources is also accurately adjusted to 10 digital grades, and the brightness consistency of different paths of LED light beams is realized by calibrating the brightness of each group of LED light sources and setting a specific brightness grade.

Compared with the prior art, the invention has the following beneficial effects:

1. while conventional annular illumination is typically a limited set of LED divergent illumination, the illumination device of the present invention can achieve 360 degree illumination of a collimated light source so that the light source can illuminate the target surface at precisely a number of different angles. The multi-angle illumination capability enables capturing of fine features and defects of the target surface from different directions during imaging, and the collimated illumination direction reduces reflected light entering the imaging system and improves dark field imaging quality and detection comprehensiveness.

2. The special electric control design provided by the invention can ensure the brightness consistency of the LED light beam imaging in different directions, thereby bringing great help to accurate detection and reducing the detection error of the system.

3. The fully hollow design of the present invention allows the device to be adapted to most current machine vision imaging systems, including objective lenses, telecentric lenses, industrial lenses, and the like.

4. The invention adopts LED illumination, allows larger illumination light spots, and provides possibility for high-speed detection.

5. All the component parts of the invention are common devices for industrial production, the difficulty of installation and adjustment is extremely low, and the invention can realize large-scale industrial application.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a rotary LED full angle annular lighting device according to the present invention;

FIG. 2 is a schematic diagram of an arrangement of LEDs in the present invention;

Fig. 3 is a schematic diagram of controlling the brightness uniformity of an LED light source according to the present invention.

Detailed Description

The invention will be described in further detail with reference to the drawings and examples, it being noted that the examples described below are intended to facilitate the understanding of the invention and are not intended to limit the invention in any way.

As shown in fig. 1 and 2, the rotary LED full-angle annular lighting device comprises an image collector 1, an imaging lens 2, a housing 3, a hollow conductive slip ring 4, an outer rotor hollow motor 5, an LED6, an LED rotary frame 7, an LED collimating lens 8, a reflecting mirror 9 and a bearing 10.

In practice, the rotary LED ring illumination device of the present invention is a completely hollow structure, allowing the image collector 1 and the imaging lens 2 to be coaxially installed into the present invention.

As shown in fig. 1, the hollow conductive slip ring 4, the outer rotor hollow motor 5, the LED6, the LED rotating frame 7, the LED collimating lens 8 and the reflecting mirror 9 form a rotary lighting module.

The hollow conductive slip ring 4 and the outer rotor hollow motor 5 are both of an outer rotor structure of an inner stator, the inner stator is of a large-caliber hollow structure, the imaging system is allowed to pass through, and the outer rotor hollow motor 5 is provided with an inner stator outgoing line and can be fixedly connected with the inner stator of the conductive slip ring 4.

The LED6 generates a light beam which is collimated to a certain degree through the LED collimating lens 8, the irradiation direction of the light source and the normal angle of the detection surface can be changed at 0-90 degrees through the adjustable reflector 9, and a path of illumination light path is formed after the light source is projected to the target point. As shown in fig. 2,3 paths are uniformly distributed at 120-degree intervals in the circumferential direction, so as to stabilize the dynamic balance in the rotation process and improve the requirement of illumination power reduction on the rotation speed.

The three groups of illumination light paths are connected with the outer rotor of the outer rotor hollow motor 5 through the LED rotating frame 7, and LED outgoing lines are fixed on the outer ring of the hollow conductive slip ring 4, so that continuous power supply and real-time light control can be realized when the LEDs rotate at high speed.

The shell 3 fixes the lighting device on the lens, and preferably, a bearing 10 is arranged between the shell 3 and the outer rotor hollow motor 5 and between the shell 3 and the hollow conductive slip ring 4 so as to ensure the stability of rotation, so that the whole structure is more compact.

The luminous flux is the radiation power perceived by the human eye and is equal to the product of the radiant energy of a certain band per unit time and the relative visibility of that band. In the field of machine vision defect detection, an industrial camera is used to replace human eyes, and exposure in the working process is a photosensitive process of an image sensor. During exposure, the detector CCD/CMOS collects photons and converts the photons into charges, and after exposure, the CCD/CMOS removes the charges in a certain way. The number of photons per unit time passing through a certain receiving surface is usually in lumen lm. The quality of the photo is greatly affected by light exposure, and if the photo is overexposed, the photo is too bright and the image detail is lost; if underexposed, the photo is too dark, and image detail is lost as well. It is therefore necessary to select an appropriate exposure amount by the total luminous flux.

The luminous flux of the detected area can be adjusted according to the requirement, and the method comprises the following steps:

(1) The required luminous flux phi of the region to be measured per second is x, the rotating speed of the rotating device is a, and the calculation formula of the luminous flux phi is as follows:

φ＝n·x·a

the rotating speed a (rpm) of the rotating device has a calculation formula:

Wherein f is the image acquisition frame rate (frame/s), and n is the number of LED groups; mu is a safety coefficient, and unstable factors existing in the actual rotation and acquisition process are considered to be more than or equal to 1.

(2) The proper luminous flux can be determined through calculation according to the surface property and the state of the detection sample, so that the illumination brightness and the rotation speed of each LED light source are controlled, and proper parameters are selected.

In order to ensure the brightness consistency of imaging in different directions, the brightness consistency of LED light beams is also required to be ensured, otherwise, too strong brightness of a certain path of LEDs can cause too strong brightness of defects in specific corresponding directions, and the brightness consistency of imaging in different directions is affected. The welding, mounting, lighting system, power supply and the like of the LEDs have certain random errors, so that even for the LEDs with the same model and the same lighting design, the LEDs have inconsistent brightness, and therefore, special design for driving and power supply of the LEDs is needed, and the method comprises the following steps:

(1) Each LED is driven by constant current and is connected with a power supply in parallel, and square waves with certain frequency and adjustable duty ratio are generated by an output port of the singlechip.

(2) Each output port controls the brightness of one LED, so that the accurate brightness adjustment of different paths of LED light beams is realized, and the brightness control schematic diagram is shown in figure 3.

(3) The duty ratio of PWM waveform of the output port of the singlechip can be set to 0-9 by a computer, the brightness of the corresponding LEDs can be accurately adjusted by 10 digital grades, and the brightness consistency of different LED light beams can be realized by calibrating the brightness of each LED and setting a specific brightness grade.

The rotary LED annular lighting device of the invention enables the LED light source to irradiate on the target surface at 360 degrees (weft direction) and 90 degrees (warp direction) by introducing innovative rotary design. This design allows to obtain a diversified lighting effect at different angles, so that different features and defects of the observed object can be more clearly visualized. The advantage of multi-angle illumination is beneficial to improving the imaging quality and the detection precision of a dark field imaging system, and is particularly suitable for the fields of detection of micro structures, surface defect analysis, imaging of transparent samples and the like.

The rotary LED annular lighting device has important technical value in the field of machine vision lighting, and provides an innovative solution for dark field imaging. The wide application potential of the method covers a plurality of fields of automatic manufacturing, medical imaging, material science and the like, and provides new possibility for technical progress and development of related industries.

The foregoing embodiments have described in detail the technical solution and the advantages of the present invention, it should be understood that the foregoing embodiments are merely illustrative of the present invention and are not intended to limit the invention, and any modifications, additions and equivalents made within the scope of the principles of the present invention should be included in the scope of the invention.

Claims

1. The rotary LED full-angle annular lighting device is characterized by comprising a hollow conductive slip ring (4) and an outer rotor hollow motor (5), wherein an LED rotary frame (7) is sleeved and fixed on the outer wall of the rotor of the outer rotor hollow motor (5), and three groups of collimation LED light sources are uniformly arranged on the LED rotary frame (7) along the circumferential direction; the outer rotor hollow motor (5) is used for realizing 360-degree rotary illumination of the region to be detected;

The inner stator of the hollow conductive slip ring (4) is fixed, and the outer rotor is connected with the power supply line of the collimation LED light source and used for realizing the rotary coupling of the power supply of the collimation LED light source.

2. The rotary LED full angle annular lighting device according to claim 1, characterized in that three groups of collimated LED light sources are spaced 120 ° apart, each group of collimated LED light sources comprises an LED (6) and a corresponding LED collimator lens (8), the front end of the LED collimator lens (8) is provided with an angle adjustable mirror (9).

3. The rotary LED full angle annular lighting device according to claim 1, wherein the outer side wall of the LED rotary frame (7) and the outer rotor of the hollow conductive slip ring (4) are respectively fixed inside the housing (3) through corresponding bearings (10).

4. The rotary LED full angle annular lighting device according to claim 1, characterized in that the hollow conductive slip ring (4) and the outer rotor hollow motor (5) are hollow structures for coaxially mounting imaging light paths.

5. The rotary LED full-angle annular lighting device according to claim 4, wherein the imaging light path comprises an imaging lens (2) and an image collector (1) arranged at the rear end of the imaging lens (2); the light emitted by the collimation LED light source reaches the region to be detected and is collected by the image collector (1) through the imaging lens (2).

6. The rotary LED full angle annular lighting device according to claim 1, characterized in that the calculation formula of the rotational speed a of the outer rotor hollow motor (5) is:

7. The rotary LED full angle annular lighting apparatus of claim 1, wherein the luminous flux of the area to be measured is adjusted according to the requirement, comprising the steps of:

φ＝n·x·a

8. The rotary LED full angle annular lighting apparatus of claim 1, wherein to ensure uniformity of brightness for imaging in different directions, the uniformity of brightness for LED beams is further ensured by controlling in the following manner: