Abstract: A depth sensor for sensing contours of an optically rough target surface includes an optic system for radiating first and second discrete areas on the target surface with first and second beams respectively of linearly polarized, coherent light of a predetermined wavelength .lambda.. The first and second beams have an intersection point an unknown distance from and proximate to the target surface and form an acute included angle .phi. having a bisector approximately normal to the target surface. The light reradiated from each of the discrete areas creates a speckle pattern on a surface spaced from and facing the target surface. Interference fringes will be formed in the area of overlap between speckles from the two speckle patterns.

Abstract: A phase modulated signal is split into quadrature components Savg+SaSin(.phi.(t)+kx(t)) and Cavg+CaCos((.phi.(t)+kx(t)). The average value for each signal is compared with the signal to produce a data bit whose meaning is that the average value was exceeded at a sampling instant. The bits at successive times (t.sub.0 and t.sub.1) are separated by an interval set by the Nyquist rate on the peak rate of change of the phase for the signal. Four bits at two sample times t.sub.0 and t.sub.1 are processed to determine the phase quadrants modulo 360 degrees to determine the direction of the phase change. The determination is used to produce a counter enable signal, counter direction control signal (up/down) and optionally an error signal if the phase change during one clock period is more than plus or minus one quadrant. A tracking counter counts the number of quadrants of change from those signals.

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).

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 F1. 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 +F1 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).

Abstract: A Cassegrain telescope having a primary mirror having an aperture centered n the axis thereof and a secondary mirror spaced from the primary mirror and centered on the axis of the primary mirror for receiving reflected light from the primary mirror and reflecting it through the aperture in the primary mirror and a support member extending from the primary mirror support structure to the secondary mirror. The support member is in the form of a conical honeycomb having cells extending in a direction parallel to the axis of the primary mirror. The support member is made from a carbonized polymeric material.