System for testing thermal response time of uncooled infrared focal plane detector array and method therefor

Abstract

A system for testing thermal response time of an uncooled infrared focal plane detector array and a method therefor is provided. The system comprises: a blackbody, a chopper, a detector unit under test and a testing system. The method comprises: emitting radiation by the blackbody, chopping by the chopper, then radiating the radiation to the uncooled infrared focal plane detector array under test; generating different responses on the radiation at different chopping frequencies by the uncooled infrared focal plane detector array under test; collecting different response values of the uncooled infrared focal plane detector array under test at different chopping frequencies; obtaining response amplitude at a corresponding frequency in a frequency domain by FFT; fitting according to a formula $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$
to obtain the thermal response time.

Claims

1. A system for testing thermal response time of an uncooled infrared focal plane detector array, comprising: a blackbody, a chopper, a detector unit under test and a testing system; wherein the detector unit under test comprises an uncooled infrared focal plane detector array under test and an adapter plate; a center of a radiating surface of the blackbody directly faces a center of an optical lens; the center of the blackbody directly faces a center of the uncooled infrared focal plane detector array under test, the chopper is provided between the blackbody and the detector unit under test; the system for testing thermal response time of the uncooled infrared focal plane detector array controls status of the blackbody, the chopper and the detector unit by external interfaces provided on the blackbody, the chopper and the detector unit; data outputted by the detector under test is transmitted to the system for testing by a data acquisition card; wherein the method comprises steps of: emitting radiation by the blackbody, chopping by the chopper, then radiating the radiation to the uncooled infrared focal plane detector array under test; generating different responses on the radiation at different chopping frequencies by the uncooled infrared focal plane detector array under test; collecting different response values of the uncooled infrared focal plane detector array under test at different chopping frequencies; obtaining response amplitude at a corresponding frequency in a frequency domain by Fast Fourier Transform (FFT); fitting according to a formula $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$ to obtain the thermal response time; wherein R.sub.V(f) represents a response amplitude corresponding to a frequency f after FFT, R.sub.V(0) is a DC (direct current) response amplitude, is the thermal response time; f is a chopping frequency of the chopper.

2. The method for testing the thermal response time of the uncooled infrared focal plane detector array, as recited in claim 1, comprising steps of: step (1): measuring DC response of the detector after the detector unit under test is stably powered on, setting a frame frequency of the detector unit to be 50 Hz; covering the detector unit completely with an object at a normal temperature, detecting and recording an output V.sub.L of the detector unit at a first moment; denoting a radiating temperature of the blackbody as T, wherein T is higher than a normal temperature; when the radiating temperature of the blackbody is stable, the detector unit under test is aligned with the blackbody, detecting and recording an output V.sub.0 of the detector unit at a second moment; in order to prevent that the blackbody is not capable of radiating on all array of the detector, getting MN pixels from a central zone of a plane array to calculate an average value, $\stackrel{\_}{V_L}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_L\left(i,j\right)}{MN},\stackrel{\_}{V_0}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_0\left(i,j\right)}{MN};$ calculating the DC response of the detector unit Rv=V.sub.0V.sub.L; step (2) measuring response of the detector under different chopping frequencies denoting a working frequency of the detector unit under test as f.sub.0 Hz; chopping radiation outputted by the blackbody with the chopper; wherein a chopping frequency of the chopper is not higher than $\frac{f_0}{2}\mathrm{Hz};,$ collecting data outputted by the detector unit under different chopping frequencies; continuously collecting N*f frames in each group, wherein N2; performing Fast Fourier Transform (FFT) on the data under different chopping frequencies, so as to obtain a response amplitude V.sub.f under a corresponding frequency in a frequency domain; selecting MN pixels in an identical area of the step (1) to calculate an average value, $\stackrel{\_}{V_f}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_f\left(i,j\right)}{MN};$ calculating a response of the detector unit under different chopping frequencies, Rv(f)=V.sub.fV.sub.L; step (3) fitting curve according to a formula $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$ to calculate a thermal response time ; according to the Rv(f) measured and calculated under different frequencies f in the step (2); taking Rv(0) and 2 as unknown parameters, fitting curve according to a formula $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$ to calculate the thermal response time ; taking a DC response Rv of the detector unit as an initial value of Rv(0) while fitting.

3. The method for testing the thermal response time of the uncooled infrared focal plane detector array, as recited in claim 2, wherein an initial value of in the step (3) is 0.01 s.

4. The method for testing the thermal response time of the uncooled infrared focal plane detector array, as recited in claim 2, wherein calculations in the steps (1)-(3) are eliminated out of blind elements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart of a thermal response time of an uncooled infrared focal plane detector array tested according to a preferred embodiment of the present invention.

(2) FIG. 2 is a schematic view of a thermal response time test platform according to a preferred embodiment of the present invention.

(3) FIG. 3 is a fitting curve diagram of a result of the thermal response time test platform according to the preferred embodiment of the present invention.

(4) Reference numbers: 1chamber blackbody; 2chopper; 3optical lens; 4detector unit under test; 5testing system

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(5) The embodiments of the present invention are described by using specific embodiments as follows. One skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention may also be implemented or applied through different specific embodiments. Details in the specification may also be variously modified or changed based on different perspectives and applications without departing from the spirit of the present invention.

(6) As shown in FIG. 2, a system for testing thermal response time of an uncooled infrared focal plane detector array comprises: a chamber blackbody 1, a chopper 2, a detector unit under test 4 and a testing system 5; wherein the detector unit under test 5 comprises an uncooled infrared focal plane detector array under test, an adapter plate, an optical lens 3; wherein the optical lens 3 is provided on a front portion of the uncooled infrared focal plane detector array under test; a center of a radiating surface of the blackbody directly faces a center of the optical lens; the center of the blackbody directly faces a center of the uncooled infrared focal plane detector array under test, the chopper is provided between the blackbody and the detector unit under test; the blackbody is a chamber black body or an extend blackbody; the system for testing thermal response time of the uncooled infrared focal plane detector array controls status of the blackbody, the chopper and the detector unit by external interfaces provided on the chopper and the detector unit; output data of the detector under test is transmitted to the system for testing by a data acquisition card.

(7) FIG. 1 is a flow chart of a thermal response time of an uncooled infrared focal plane detector array tested according to a preferred embodiment of the present invention.

(8) The preferred embodiment further provides a method for testing the thermal response time of the uncooled infrared focal plane detector array, which tests by utilizing the system mentioned above; wherein the method comprises steps of:

(9) emitting radiation by the blackbody, chopping by the chopper, then radiating the radiation to the uncooled infrared focal plane detector array under test; generating different responses on the radiation at different chopping frequencies by the uncooled infrared focal plane detector array under test; collecting different response values of the uncooled infrared focal plane detector array under test at different chopping frequencies; obtaining response amplitude at a corresponding frequency in a frequency domain by Fast Fourier Transform (FFT); fitting according to a formula

(10) $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$
to obtain the thermal response time; wherein R.sub.V(f) represents a response amplitude corresponding to a frequency f after FFT, R.sub.V(0) is a DC (direct current) response amplitude, is the thermal response time; f is a chopping frequency of the chopper.

(11) Specifically, the method further following steps of:

(12) step (1): setting up test platform according to FIG. 2, connecting devices of the chamber blackbody; the chopper; the detector unit comprising a detector under test, an adapter plate and an optical lens; and a test system in a PC (personal computer); regulating a distance between the chamber blackbody and the detector unit under test to ensure that a distance between a blackbody radiating surface of the chamber blackbody and a plane of the optical lens allows a focused image to be clear and the optical lens to be centered on the radiating surface; regulating a position of the chopper to ensure that blackbody radiation passed through the chopper is capable of being uniformly radiated to the detector unit under test, confirming, powering on and starting the devices;

(13) step (2): measuring DC response of the detector

(14) after the detector unit under test is stably powered on, setting a frame frequency of the detector unit to be 50 Hz; covering the detector unit completely with an object at a normal temperature, detecting and recording an output V.sub.L of the detector unit at a first moment; denoting a radiating temperature of the blackbody as T, wherein T is higher than a normal temperature; when the radiating temperature of the blackbody is stable, the detector unit under test is aligned with the blackbody, detecting and recording an output V.sub.0 of the detector unit at a second moment; in order to prevent that the blackbody is not capable of radiating on all array of the detector, getting MN pixels from a central zone of a plane array to calculate an average value,

(15) $\stackrel{\_}{V_L}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_L\left(i,j\right)}{MN},\stackrel{\_}{V_0}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_0\left(i,j\right)}{MN};$
calculating the DC response of the detector unit Rv=V.sub.0V.sub.L;

(16) step (3) measuring response of the detector under different chopping frequencies

(17) denoting a working frequency of the detector unit under test as f.sub.0 Hz; chopping radiation outputted by the blackbody with the chopper; wherein a chopping frequency of the chopper is not higher than

(18) 0$\frac{f_0}{2}\mathrm{Hz};,$
collecting data outputted by the detector unit under different chopping frequencies; continuously collecting N*f frames in each group, wherein N2; performing Fast Fourier Transform (FFT) on the data under different chopping frequencies, so as to obtain a response amplitude V.sub.f under a corresponding frequency in a frequency domain; selecting MN pixels in an identical area of the step (1) to calculate an average value,

(19) $\stackrel{\_}{V_f}=\frac{\underset{i=1}{\overset{M}{.Math.}}\underset{j=1}{\overset{N}{.Math.}}{V}_f\left(i,j\right)}{MN};$
calculating a response of the detector unit under different chopping frequencies, Rv(f)=V.sub.fV.sub.L;

(20) step (4) fitting curve according to a formula

(21) $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$
to calculate a thermal response time ; according to the Rv(f) measured and calculated under different frequencies f in the step (3); taking Rv(0) and as unknown parameters, fitting curve according to a formula

(22) $\mathrm{Rv}\left(f\right)=\frac{\mathrm{Rv}\left(0\right)}{\sqrt{1+{\left(2f\right)}^2}}$
to calculate the thermal response time ; taking a DC response Rv of the detector unit as an initial value of Rv(0) while fitting; wherein an initial value of is 0.01 s.

(23) FIG. 3 is a fitting curve, wherein a thermal response time is 8.6 ms.

(24) Calculations in the steps mentioned above need eliminating blind elements.

(25) One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

(26) It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.