This , it is not considered advanced optical properties , only from practical applications, to talk about several elements of
source selection:
1 Select the angle of the light source for machine visionLow angle dark field light is mainly used to detect , which is most reflective object surface is not into the camera, so the
background is black , spiky place only reflective objects into the camera, such as the detection of metal surface scratches ,
background black, white scratches are mainly used in high-angle light bright-field illumination , which is the most reflective
surface can be measured into the camera, so the background is white, such as the detection of salient features of the
surface . diffuse reflection angle of the light source is mainly detecting irregular or applied to the surface shape of the light
emitting surface , which compensates for changes in the angle of the surface , a more uniform image.
Low angle light choices are: low angle ring light , zero angle ring light , strip light, a combination of strip light, square lightHigh angle representation light : high angle ring light , 90 degree circular light , strip light, coaxial light source , such as a
combination of strip light
Representative diffuse sources are: Ring shadowless light, shadowless light dome , flat shadowless light , etc.According to the irradiation direction of machine vision lighting , can be divided into the front lighting, back lighting,
structured lighting , forward lighting is light and camera on the same side of the object to be measured , the advantage
of easy installation , primarily reflecting objects surface detail features , will be measured back- lighting is placed between
the light source and camera parts , mainly reflecting contour edge information of the object , its advantage is to obtain
high -contrast images , structured lighting is light grating or structure projected onto the measured object , the structure
of the optical path , to determine the three-dimensional information .
Forward light source choices are: ring light , shadowless light , strip light, coaxial light source ( most sources are forward
lighting )
Back- light illumination source: backlight, backlight parallel , coaxial light , strip light, highlighting the parallel light3 Choose light colors - the longer the wavelength , the stronger penetration ; the shorter the wavelength , the better
diffusion .
LED machine vision lighting , the red with the most , because of the low cost of the red LED , and the most sensitive
monochrome CCD chip 660nm light. Blue surface quality suitable for detecting an object , because the wave length . Of
course, the better the ultraviolet scattering , since the wavelength is shorter . The white is a neutral color, suitable for
making color images , or the color of the object is changing. High intensity of green and blue wavelengths and close, so
sometimes used instead of the blue green . Infrared detection for translucent objects such as light color and background
color to consider using the same color with the measured object light makes the image brighter. ( Eg : red the red obje-
cts brighter ) ; using the measured object contrast color light will darken the image lines ( eg : the blue object darker red )
Rich love their specific wavelength light source can be customized : such as ultraviolet light sources, infrared light, infrared
light , such as COSCO
4 Select the size of the light sourceIn addition to limiting the installation space , i.e., the field size of the object to be detected is the primary factor in
selecting the size of the light source , taking into account the general uniformity and line offset the detected field of view
, the range can be uniformly irradiated with light to be detected than large field of view about 1/3
Rich love their large size can be customized machine vision lighting , as long strip light, large area backlight, coaxial light
source, etc.
5 Select the brightness of the light sourceWhen the light is not bright enough , there may be three bad will happen . First, the camera signal to noise ratio is not
enough ; since the brightness of the light is insufficient, the image contrast is not necessarily , the possibility of noise
appearing in the image is then increased. Secondly, the brightness of the light is not necessarily to increase the aperture ,
thereby reducing the depth of field. In addition, when the brightness of the light source is not enough time , natural light
and other random effects of light on the system will be the largest .
Especially in the high-speed machine vision inspection , since less light into the camera industry , the brightness of the light
source is put forward higher requirements for the general high-brightness light source solutions include : the use of high-
power LED dense arrangement of particles , plus special optical lens , the controller using the flash to raise the voltage to
increase the instantaneous luminance .
Rich love their special advantages in terms of high-brightness light source , especially highlighting the backlight , using a
special circuit and thermal design , three times the brightness of the backlight in general .
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