The output voltage of U12 is the AC voltage of component U2, and the output voltage of component U1 is considered. U3 is the AC component of "output side", and U4 is an excess quantity during analysis.
According to the analysis of Figure 12, U2 is the inverted phase signal of U1. In order to facilitate the derivation, the amplitude of U2 is a times of U1
The circuit will not weaken the low frequency signal. It is also a first-order RC filter circuit, which can weaken the low-frequency signal better than no cancellation.
However, after the network is connected with a logic gate of a nonlinear element, the impedance introduced by the logic gate will make the cancellation function transition to the first-order filtering effect. In order to weaken the influence of the logic gate access, it is necessary to increase R1, R2, C1 and C3 in the figure, so that the output signals of the two logic gates will flow into each other less, so as to maintain equation (11).
From the above analysis, it is necessary to ensure that C1 = C3, R1 = R2, and make the value as large as possible.
In order to verify the control effect of the adjustable light source, the secondary light source system was tested. The external brightness and the light source system brightness were tested at 5:00, 6:00 and 8:00 p.m., respectively. Only two of the test results were taken, as shown in Table 2. The brightness of module 1 and module 12 can be automatically adjusted with the change of external brightness. When the external brightness is lower than a certain value, the brightness of the light source system reaches the maximum value, and the external brightness continues to decrease, and the brightness of the light source system remains unchanged.
Conclusion
In this paper, based on the analysis of the principle and performance of common hardware equipment, according to the lighting principle and light intensity transfer function, a secondary light source lighting system is designed. In the system, five corresponding lighting modes are established according to different defect detection objects, and the images of the detected objects are collected under the corresponding lighting modes, and the optimal image quality can be obtained, so as to meet the image acquisition requirements of various components in the system. In addition, the control circuit of secondary light source system and light source is discussed and designed. Different lighting methods can be used for different defects. The brightness of light source can be automatically adjusted according to the intensity of external light to meet the requirements of system detection. The designed control circuit includes: (1) the brightness of the light source can be controlled by the light sensor to control the brightness of the light source to keep the brightness of the light source consistent; (2) there are 16 brightness control areas, which can be adjusted by any combination or independently. The controller can control the brightness of 16 control areas to highlight the defects or important parts of the product to be tested, so as to improve the detection accuracy and efficiency. Adaptive selection of lighting mode will be the focus of the next research work.
(Editor in charge：admin)
