PURPOSE: To enhance the availability for vehicle without requiring any expensive optical system by representing the differential signal of synthesized outputs from two sets of photodetectors arranged alternately in the form of a speed thereby lowering the sensitivity for the height from the ground surface.
CONSTITUTION: A large number of slits 22 are made while elongating laterally with respect to the moving direction of a vehicle and a photodetector is disposed in the rear of slit 22. First and second photodetector sets are connected, respectively, with preamplifiers 26, 27. The first photodetector set comprises every other photodetectors arranged in the moving direction of vehicle and the second photodetector set comprises the remaining photodetectors and thereby the photodetectors in the first and second sets are arranged alternately each other. The amplifiers 26, 27 are connected, respectively, with the inverted and non- inverted inlets of a differential amplifier 28. A signal from the output end of amplifier 28 is passed through a band-pass filter 29 during movement of the vehicle before being fed to a comparator 30. Output signal from the comparator 30 is fed to a frequency/voltage converter 31. Outputs from the comparator 30 and converter 31 drives the digital and analog display of speed, respectively.
GABURIERU DONARUDOSON
NIKORASU JIEEMUZU CHIRUTON
