CN110082358B

CN110082358B - Method for realizing structured light illumination

Info

Publication number: CN110082358B
Application number: CN201910368307.XA
Authority: CN
Inventors: 骆聪; 袁春辉; 杨鹏
Original assignee: Tztek Technology Co Ltd
Current assignee: Tztek Technology Co Ltd
Priority date: 2019-05-05
Filing date: 2019-05-05
Publication date: 2022-01-04
Anticipated expiration: 2039-05-05
Also published as: CN110082358A

Abstract

The invention provides a method for realizing structured light illumination, wherein an LED array is placed in a defocusing area of an imaging module, the imaging resolution of an imaging system on the LED array can be reduced, the control on the phase of sinusoidal structured light of the LED array can be realized by lightening LEDs at different positions in the LED array, the phase shift of the sinusoidal structured light of the LED array is realized, thus the high-brightness LED linear structured light illumination and imaging are realized, and the detection efficiency is improved.

Description

Method for realizing structured light illumination

Technical Field

The invention relates to the technical field of illumination, in particular to a method for realizing structured light illumination.

Background

The illumination light source with sine-shaped light intensity distribution can enhance the defects of high-reflectivity surfaces such as glass, ceramics, polished metal and the like, so the illumination light source is widely applied to the detection of the materials, generally, a high-brightness liquid crystal display is used for displaying sine stripes to realize a structured light source, and a displayed image is changed to realize the translation of structured light; due to the limitation of the heat dissipation structure of the liquid crystal display module, 1500nit high-brightness illumination is difficult to realize through the liquid crystal display, and a flaw detection system using the structured light source needs to acquire an image with a high signal-to-noise ratio by using an ultra-long exposure time, so that the detection efficiency of the whole flaw detection system is reduced.

Disclosure of Invention

In order to solve the problems, the invention provides a method for realizing structured light illumination, which can realize high-brightness structured light illumination, thereby greatly improving the defect detection efficiency.

The technical scheme is as follows: the method is characterized in that: which comprises the following steps:

(1) arranging single LEDs at equal intervals, and sequentially lightening to obtain a group of linear lighting source LED arrays with periodic structures;

(2) placing a detection sample between the LED array and an imaging module, and adjusting the distance between the detection sample and the imaging module so that the imaging module can clearly image the detection sample, wherein the LED array is positioned in a defocusing area of the imaging module;

(3) the light intensity of the image of the detected sample is expressed in a sine curve form and is modulated by the sine structure light of the LED array, so that an obvious sine stripe structure appears on the image of the detected sample;

(4) and by lighting the LEDs at different positions in the LED array, the phase change of the sine stripes in the image is realized, so that the phase shift of the sine structured light of the LED array is realized, and finally the linear structured light illumination and imaging of the high-brightness LED are realized.

It is further characterized in that:

the imaging module adopts a linear array CMOS sensor;

the period of the LED array is L, the modulation degree of modulation transfer function MTF of the imaging module when the LED array is imaged at 1/2L spatial frequency is 0, and the modulation degree at 1/L spatial frequency is 0.2-0.5;

each row of the LED array is shifted by a distance of L/4 relative to the previous row, and the sinusoid of the LED array's sinusoidal structured light correspondingly produces 1/4 cycles of shift.

The LED array is placed in the defocusing area of the imaging module, so that the imaging resolution of the imaging system on the LED array can be reduced, the control on the sinusoidal structure light phase of the LED array can be realized by lighting LEDs at different positions in the LED array, the phase shift of the sinusoidal structure light of the LED array is realized, the high-brightness LED linear structure light illumination and imaging are realized, and the detection efficiency is improved.

Drawings

FIG. 1 is a schematic diagram of the optical path structure of a flaw detection system for a structured light source;

FIG. 2 is a schematic diagram of an arrangement of LED arrays;

FIG. 3 is a schematic diagram of the light intensity distribution of an LED array;

fig. 4 is a schematic diagram of an optical path structure according to an embodiment of the present invention.

Detailed Description

As shown in fig. 1, fig. 2 and fig. 3, the method for implementing structured light illumination of the present invention includes the following steps:

(1) the single LEDs 3 are arranged at equal intervals and are sequentially lightened to obtain a group of linear lighting source LED arrays with periodic structures, the existing low-brightness liquid crystal display is replaced, and the brightness is greatly improved; the imaging module 1 adopts a linear array CMOS sensor, and the power of an LED3 in an LED array is 2.5W;

(2) the detection sample 2 is placed between the LED array and the imaging module 1, and the distance between the detection sample 2 and the imaging module 1 is adjusted, so that the detection sample 2 is clearly imaged by the imaging module 1, and the LED array is located in a defocusing area of the imaging module 1, so that the imaging resolution of the imaging system on the LED array can be reduced; the imaging system consists of an LED array and an imaging module;

(3) the light intensity of the image of the detected sample 2 is expressed in a sine curve form and is modulated by the sine structure light of the LED array, so that an obvious sine stripe structure appears on the image of the detected sample 2;

(4) by lighting the LEDs 3 at different positions in the LED array, the phase change of the sine stripes in the image is realized, so that the phase shift of the sine structured light of the LED array is realized, and finally the linear structured light illumination and imaging of the high-brightness LED are realized.

In fig. 1 to 4, the black color of the LED in the LED array indicates off, whereas the black color of the LED is on.

Specifically, as shown in fig. 4, 4 groups of LED arrays are provided, each group of LED arrays has a period of L, and each group of LED arrays is provided with a corresponding imaging module;

detect sample 2 and be located 4 groups LED array and its corresponding formation of image module 1 between, the adjustment detects the distance between sample 2 and the formation of image module 1 to make formation of image module 1 to detecting the clear formation of image of sample 2, the modulation transfer function MTF when formation of image module 1 is to the formation of image of LED array needs to satisfy the condition simultaneously: the modulation degree at 1/2L spatial frequency is 0, and the modulation degree at 1/L spatial frequency is 0.4; when the defocusing amount meets the relationship of the two modulation transfer functions MTF, the periodic stripes in any form can be degraded into sine structure stripes, so that the sine structure light illumination is realized.

By lighting the LEDs 3 at different positions, phase change of sinusoidal stripes in an image, that is, translation of stripes, can be achieved, wherein each row in the LED array is translated by a distance of L/4 with respect to the previous row, and the sinusoidal curve of the sinusoidal structured light of the LED array correspondingly generates translation of 1/4 periods, that is, as shown in fig. 3, the light intensity distribution of the LED array is represented by a sinusoidal curve form, and in the LED array, the left LED3 is lit, so that the sinusoidal curve of the sinusoidal structured light on the image plane of the sample 2 detected in the imaging module 1 is translated to the left by 1/4 periods, that is, by lighting the LEDs at different positions, control of the phase of the sinusoidal structured light of the LED array is achieved, and therefore phase shift of the sinusoidal structured light of the LED array is achieved, and linear structured light illumination and imaging of the high-luminance LEDs are achieved, and under the condition of ensuring the signal-to-noise ratio of the detection system, the detection efficiency is improved.

Claims

1. A method for realizing structured light illumination is characterized by comprising the following steps: which comprises the following steps:

(4) by lighting the LEDs at different positions in the LED array, the phase change of the sine stripes in the image is realized, so that the phase shift of the sine structured light of the LED array is realized, and finally the linear structured light illumination and imaging of the high-brightness LED are realized;

the period of the LED array is L, the modulation degree of modulation transfer function MTF of the imaging module when the LED array is imaged at 1/2L spatial frequency is 0, and the modulation degree at 1/L spatial frequency is 0.2-0.5; each row of the LED array is shifted by a distance of L/4 relative to the previous row, and the sinusoid of the LED array's sinusoidal structured light correspondingly produces 1/4 cycles of shift.

2. A method of implementing structured light illumination as claimed in claim 1, wherein: the imaging module adopts a linear array CMOS sensor.