Abstract

Thermistor bolometers are fast, sensitive infrared detectors with good responsivity from 1 to 15 microns. The detectors consist of a thin flake of thermistor material mounted on a thermal sink. The time constant of the detectors is determined by the type of thermal sink on which the flakes are mounted. By cementing thermistor flakes to quartz or glass thermal sinks, detectors with time constants ranging from 3 to 5 and 5 to 8 milliseconds, respectively, are obtained.

Experimental results are given for quartz- and glass-backed thermistor detectors having sizes of sensitive areas ranging from 0.2 to 12.5 square millimeters. Performance criteria for these detectors are tabulated and plotted as a function of size of sensitive area. Typical frequency response and relative spectral responsivity data are given.

Detector flakes have to be mounted in sealed housings for noise-free operation. Two types of housings are described.

© 1953 Optical Society of America

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References

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  1. W. H. Brattain and J. A. Becker, J. Opt. Soc. Am. 36, 354 (1946).
  2. J. A. Becker and et al., OSRD 5991, Final Report on Development and Operating Characteristics of Thermistor Bolometers.
  3. R. C. Jones, J. Opt. Soc. Am. 36, 448 (1946).
    [Crossref]
  4. This reference band width is that used by R. C. Jones [J. Opt. Soc. Am. 39, 327–356 (1949)];however, the value of ENI defined in this paper differs from that used by Jones, since responsivity at 15 cps (S15) is used instead of computing zero frequency responsivity S0. Jones’ zero frequency responsivity, which is equivalent to Bell Telephone Laboratories’ first time-constant, steady-state responsivity, is arrived at by substituting a single time-constant curve which is in contact with the experimental curve at the point where the slope is 3 db. In order to arrive accurately at S0from the tabulated responsivity S15an experimental frequency response curve has to be taken for each detector unit, since τ2 and τ3 vary from unit to unit.Complete frequency response data are available only for a small number of the units tabulated. From these data we can approximately relate S0 and S15 in general. From the foregoing data we find for quartz-backed units S0 ranges from 1.0 to 1.25 times S15.
    [Crossref] [PubMed]
  5. Research and Development Board, Natl. Bur. Standards, Symposium on Infrared Instrumentation, Houston, Texas, September 13–15, 1951
  6. R. J. Havens, J. Opt. Soc. Am. 36, 355 (1946).

1949 (1)

1946 (3)

R. J. Havens, J. Opt. Soc. Am. 36, 355 (1946).

W. H. Brattain and J. A. Becker, J. Opt. Soc. Am. 36, 354 (1946).

R. C. Jones, J. Opt. Soc. Am. 36, 448 (1946).
[Crossref]

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Figures (10)

F. 1
F. 1

Resistance of thermistor detector flakes as a function of shape of sensitive area (resistance at 25°C).

F. 2
F. 2

Steady state voltage current curve of thermistor detector.

F. 3
F. 3

Thermistor bolometer bridge circuit.

F. 4
F. 4

Performance criteria vs active area for quartz-backed thermistor detectors.

F. 5
F. 5

Performance criteria vs active area for glass-backed thermistor detectors.

F. 6
F. 6

Frequency response curve for quartz-backed thermistor detector.

F. 7
F. 7

Variation of responsivity over a thermistor flake 3.07 × 1 mm sensitive area.

F. 8
F. 8

Spectral responsivity curves of blackened thermistor detector (0.6 × 0.75 mm) and gold-blackened thermocouple (0.75 × 0.75 mm).

F. 9
F. 9

Relative spectral responsivity of blackened thermistor detector as compared to gold-blackened thermocouple.

F. 10
F. 10

Thermistor detector assembly mounted on preamplifier unit.

Tables (3)

Tables Icon

Table I Comparison of three types of thermistor detectors. Size of sensitive area: 2.5 × 0.2 = 0.5 mm2. No. 2 thermistor material, resistance 3 megohms at 25°C.

Tables Icon

Table II Characteristics of quartz-backed thermistors over a range of sensitive areas.

Tables Icon

Table III Characteristics of glass-backed thermistors over a range of sensitive areas.

Equations (3)

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V P 2 / R P = C T ( T P T 0 ) ,
Δ V Δ W = F a α V B [ 1 C 1 ( 1 t / T 1 ) + 1 C 2 ( 1 t / T 2 ) + ] ,
Δ V Δ W = F a α V B [ 1 C 1 ( 1 t / T 1 * ) ] ,