Title: Photometric instrument with thermoelectric control of a photovoltaic semiconductor detector

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1. A standard instrument for generating a stable calibrated quantity of radiant energy to be used such as in the testing and calibration of photometric instruments, the standard instruments being characterized by:

a standard source of radiant energy;

a calibration probe for accurately monitoring the radiant energy output of the standard source including:

a photovoltaic silicon light detecting element arranged to receive radiant energy emitted from the standard source upon a sensitive surface thereof and to emit an electrical signal related to the incident radiant energy;

a thermally conductive block member mounting the photovoltaic silicon light detecting element;

temperature sensing means mounted on the thermally conductive block member and being in thermal communication with the silicon light detecting element along a continuous path through the conductive block member;

controllable heat emitting means mounted on the thermally conductive block member and being in thermal communication with the temperature sensing means and silicon light detecting element along continuous paths through the conductive block member;

a feedback circuit responsive to the temperature sensing means for controlling the heat emitting means to maintain the conductive block member and the silicon light detecting element at a constant temperature; and

the silicon light detecting element being spaced from the temperature sensing and heat emitting means, located adjacent one another, to provide a thermal lag through the conductive block member to smooth out temperature fluctuations and thereby maintain the silicon light detecting element at a substantially invariant temperature; and

an electrical meter for indicating the magnitude of the electrical signal emitted by the light detecting element and for thereby accurately indicating the output of the standard source of radiant energy; and

means on the standard source of radiant energy for adjusting its output, whereby a standard radiant energy value, as measured by the calibration probe and electrical meter, may be obtained with great accuracy,

whereby the relationship between incident radiant energy from the standard source and electrical signal output of the light detecting element remains substantially invariant and the calibration probe can accurately monitor the output of the standard source to maintain its calibrated value.

2. A standard instrument as claimed in claim 1 wherein the temperature sensing means and heat emitting means are semiconductor elements, the instrument further comprising a circuit board mounting the temperature sensing means and heat emitting means, and wherein the conductive block member detachably fits over the temperature sensing means and heat emitting means.

Other info:

Inventors: McCarter, Craig A. (Old Greenwich, CT, US)

Application Number: 694648
Filing Date: 1976-06-10
Publication_date: 1978-05-16
Assignee: Hoffman Engineering Corporation (Old Greenwich, CT)
Primary Class(es): 250/238 327/512, 374/2, 374/121
Other Classes:
US Patent Ref:

3444399	May, 1969	Jones	307/310.
3703651	Nov, 1972	Blowers	307/310.
3877817	Apr, 1975	Ralston	250/238.
3962559	Jun, 1976	Drda	307/310.

Other Refs:
Primary Examiner: Rolinec, Rudolph V.
Assistant Examiner: Sunderdick, Vincent J.
Attorney: