LASER DOPPLER FREQUENCY CONTROL

Abstract

A pulse Doppler, laser radar as described which includes master laser whose output Fo is shifted in frequency by dF(t) during its amplification. The dF(t) frequency shift is compensated by providing a modulator which modulates the master laser output frequency Fo with a local oscillator signal Fl. A first mixer is provided which combines the shifted master laser frequency signal and the local oscillator modulated, master laser output so as to eliminate the master laser frequency Fo from the combined signals. A second mixer is provided for combining the reflected, Doppler shifted laser signal with the local oscillator modulated, master laser output signal Fo+Fl to eliminate the master laser output frequency Fo from the combined signal. Additional detection circuitry is provided to determine the difference in frequencies of the combined signals from the first and second mixers so as to isolate the Doppler shift signal from the amplifier-induced shift dF(t). An additional frequency control subsystem for the master laser is also described which employs an absorption cell in the feedback loop.

Source: Google Patents

35 USC §181 Secrecy Order

Inventor

• 1ALAN B. CALLENDER

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