Precision piezoelectric ceramic target tracking system design
Atmospheric laser transmission, due to the interaction with the turbulence, resulting in fluctuations in amplitude and phase of light waves. Jitter frequency is mainly low-frequency components, the frequency response of the piezoelectric ceramic crystal above 1000Hz, to meet the elimination of atmospheric turbulence caused by the spot jitter. In the optical tracking system, the conventional device is used for target tracking CCD. Since a large amount of data collected by CCD, on the back of the high requirements of the data processing unit, and a large amount of data processing increases the processing complexity and processing time.
The tracking system uses the PSD position sensitive spot position sensors collect information, only four signal output, only five additions, one subtraction and one division, computation is greatly reduced. And the microprocessor of the system sampling dsPIC33F series microcontrollers, it has 40M of instruction cycles. Its interior is a single instruction cycle subtraction, division, only 19 instruction cycles, which greatly improves the computing speed.
Principle 1 composition and correction system
Correction overall system block diagram shown in Figure 1, a light beam from a mile away, and by the laser radar system receives, by tilting mirror, beam by beam splitter splitting, enter part of the imaging system, entering the PSD position sensitive part of the sensor.
Collected by bit sensitive sensor spot position, the formation of four current signals, the current-voltage conversion after amplification by the microcontroller A / D conversion and calculate the offset spot, and calculate the driving piezoelectric ceramics based on spot offset the required voltage. Finally, the drive voltage value D / A converter and drives the PZT (piezoelectric ceramic crystal) change the angle of the mirror is inclined by a high pressure drive, so that the spot is always in the center of the imaging system.
Tracking System Block Diagram
2 overall system design
2.1 sensitive sensor system
Position sensitive sensor is composed of a Si photodiode, the output signal is a current signal. Current size and strength of the spot position and light intensity related. Its primary circuit must be current-voltage conversion circuit. Four output signal and the relationship between the spot position is:
Where i1, i2, i3, i4 for four output signals. Seeking the formula x, y when the division is used to eliminate the influence of light intensity change of the position to obtain the position signal independent of the light intensity.
