The invention is an optical scanner that sequentially focuses optical energy (light) at selected points in space. The essential component of the invention is a scanning wheel including several glass windows with each window having a different thickness. Due to this difference in thickness, the displacement of the emerging light from the incident light is different for each window. The scanner transmits optical energy to a point in space while at the same time receiving any optical energy generated at that point and then moves on to the next selected point and repeats this transmit and receive operation. It fills the need for a system that permits a laser velocimeter to rapidly scan across a constantly changing flow field in an aerodynamic test facility.

The invention provides a distance measuring apparatus for determining the distance of a target object as a function of the transit time of a measurement light pulse which is emitted by a transmitter in the transmission portion of the apparatus towards the target object, reflected thereby and received by the receiving portion of the measuring apparatus and for attainment of superior measurement accuracy the intensity of the measurement light pulse is correlated to the distance and reflectivity of the target object as well as to the "transparency" of the transmission medium between the measuring apparatus and the target object, such correlation being effected by optical damping of either the transmitted light pulses and/or the reference light pulse and/or the light pulses reflected by the target. Optical damping may advantageously be effected by means of a light path change-over switch which feeds a light pulse, generated by the transmitter by controlling the timing of a trigger generator for the transmitter, so that the full intensity or attenuated optic light is passed either into a transmitting measurement light path or into a reference light path having a known transit time for the reference light therein, electrical delays inherent in the apparatus and causing errors in distance measurement being compensated for by subtracting the transit time measurement values of reference light pulses from transit time measurement values of transmitted measurement light pulses.

A programmable optical sensor is formed by coupling a proximity focused channel intensifier tube to a silicon target vidicon. The photocathode is gated by a first time programmed voltage and the gain of the microchannel plate is also controlled by a second time programmed voltage. The second voltage is less than 1,000 volts permitting the use of solid state circuitry.

There is provided a multifunction coaxial objective system (16) for a laser rangefinder (10). The transmitter, receiver, and viewing optical systems have a common, coaxial optical axis (48). The multifunction coaxial objective system (16) includes lenses (28), (30) and mirror (32) each having a central obscuration therein. The multifunction coaxial objective system (16) further includes a lens (34) having a dichroic coating on one surface (50). The dichroic coated lens (34) transmits visible and near infrared light and reflects light of the wavelength transmitted by a laser emitter (18). The viewing optical system includes a pair of focusing wedges (42), (44) for adjusting the focus of the viewing optical system. Each focusing wedge (42), (44) is a wedge-shaped optical flat. The pair of focusing wedges (42), (44) are disposed against one another along a plane inclined with respect to the coaxial optical axis (48) of the multifunction coaxial objective system (16). Focus adjustment is achieved by relative movement between the focusing wedges (42), (44) along the inclined plane. The multifunction coaxial objective system (16) of the present invention may alternatively be incorporated into a rangefinder and camera for example.