Abstract: A capnography system has a 4.2 micron LED emitter of narrow-band radiation having a center wavelength very close to the 4.26 micron absorption band of CO.sub.2 breathing gas in a breathing tube. The radiation passes through windows in an insert in the breathing passage between the LED source and an infrared detector in an opposite side of the insert. A mirror is optionally placed in the opposite wall to reflect the radiation back to the detector which is then placed on the same side as the emitter. The LED emitter is pulsed at a low frequency repetition rate with a regulated voltage from a power supply. The detector output is applied to processing electronics which includes amplification and dual integrators that integrate the detector output on two signal paths, one the integration of each pulse and the other the integration of detector background with the two differences to provide self calibration against drift and noise.

Abstract: A long exposure photometer-digitizer operative in an integration mode to receive weak illumination as from celestial observations through a telescope or from field or laboratory observations of objects and to provide a recorded digital representation thereof. A silicon, vidicon illumination sensor is employed to provide a wide dynamic range, sensitive and linear response over a large spectral region. Cumulative photon interaction with the vidicon tube during a long exposure is achieved by operating the vidicon at a reduced temperature which minimizes dark current effects and promotes integration mode operation. After a predetermined vidicon exposure interval the image electrically stored in the target is read out by a scanning electron beam, digitized and recorded to provide an immediately available digital record of the object. The target is sensitized before each exposure.