CN101852650B - Device and method for improving temperature measurement uniformity of thermal infrared imager - Google Patents

Abstract

The invention discloses a device and method for improving the temperature measurement uniformity of a thermal infrared imager. The device comprises an optical lens group, a non-refrigerated infrared focal plane and a motor, a thermal imaging circuit module, a focusing mechanism and a focusing circuit module, wherein the optical lens group is installed at the center of a shell; the non-refrigerated infrared focal plane and the motor are installed on a substrate; a displacement sensor based on the differential transformer principle is installed on the substrate and sequentially comprises an iron core, an original secondary coil winding and a shielding case from the inside out; one end of a slide rod is connected with the iron core, and the other end of the slide rod is connected with the shell of the optical lens group; and the original secondary coil winding is connected with a detection circuit module drived by the displacement sensor. Because the displacement sensor based on the transformer principle and a treatment circuit drived by same are additionally arranged, the temperature value of each pixel point in a thermal image is computed according to the response voltage of the focal plane after focusing and the displacement sensor. The invention can be used for measuring the temperature and simultaneously measuring the image distance value of the lens, thereby compensating the thermal image error caused by oblique light beams to acquire a more accurate measurement result of temperature field.

Description

Improve the device and method of temperature measurement uniformity of thermal infrared imager

Technical field

The present invention relates to measure method of temperature and device, be specifically related to a kind of device and method that improves temperature measurement uniformity of thermal infrared imager.

Background technology

The principle of infrared thermal imaging technique is to receive the infrared radiation that measured object is launched by sensors such as non-refrigeration focal surfaces, thereby records the Temperature Distribution on measured object surface.Because characteristics such as it is directly perceived, untouchable are widely used in fields such as medical diagnosis, malfunction monitoring, pipeline inspection.Except monitoring function, thermal infrared imager is also natural to be a kind of temperature measurement tool.Its advantage is directly to measure the two-dimensional temperature field with certain area, and conventional temperature sensor such as thermopair, thermal resistance can only be measured the temperature of single-point.

Although thermal infrared imager can be measured the temperature field, can't reach higher accuracy of measurement at present, one of them major issue is each pixel measuring error skewness.There are three reasons to cause this situation: one, because the manufacturing process problem of infrared eye, can't guarantee that all the detection units on the focal plane all have identical response characteristic, this heterogeneity causes having fixing noise pattern on the infrared thermal imagery, and being reflected on the temperature-measuring results is exactly uneven fixed error.Adopt the black matrix Calibration Method can compensate this heterogeneity, pending application CN 200710192272 has then proposed a kind of real-time calibration device and has simplified the step of demarcating greatly; Two, because the effect of blocking of diaphragm, unthreaded hole etc. in the optical system, part axle outer light beam can't be received by infrared eye, so that the detector received energy is inhomogeneous, this phenomenon is called " vignetting ", document " infrared optical system emergent pupil and cold screen matching way and vignetting analytical calculation " (infrared technique, 2006 28 the 2nd phases of volume) is illustrated this phenomenon.This compensation of error factor can be calculated according to the structural parameters of thermal imaging system itself; Three, during skew ray bundle incident optical system, increase along with incident angle, illumination on the detector diminishes gradually, if according to document " the thermal infrared imager thermometric calculates and error analysis " (infrared technique, 1999 21 the 4th phases of volume) when described thermal imaging system common-used formula calculates, can take place more by the big more situation of image border error.

In above-mentioned three kinds of phenomenons, preceding two kinds only relevant with the structural parameters of thermal imaging system, have reasonable method and compensate.But the third error is except fixing structural parameters, and the dynamic parameter when also working with thermal imaging system---image distance, object distance are relevant, thereby existing thermal imaging system device also fails to overcome the influence of this heterogenicity error.

Summary of the invention

At the heterogeneity problem of present infrared thermal imaging technique measurement two-dimensional temperature field, purpose of the present invention is in providing a kind of device and method that improves temperature measurement uniformity of thermal infrared imager, to improve the measuring error that causes because of the 3rd class heterogeneity in the background technology.

To achieve these goals, the present invention adopts following technical scheme:

One, a kind of device that improves temperature measurement uniformity of thermal infrared imager:

Comprise housing, be installed in the housing center the optical lens group, be installed in non-refrigerating infrared focal plane and motor, thermal imaging circuit module, Focusing mechanism and focusing circuit module on the substrate; Displacement transducer based on differential mutual inductor principle is installed on substrate, described displacement transducer comprises iron core, former secondary coil winding and shielding case from inside to outside successively, sliding bar one end links to each other with iron core, the other end links to each other with the optical lens assembly housing, the shielding case of displacement transducer is installed on the substrate, and former secondary coil winding drives the testing circuit module with displacement transducer and links to each other.

Described displacement transducer drives the testing circuit module and comprises AD598 one chip displacement of the lines differential transformer signal conditioner, operational amplification circuit OPA177 and AD conversion chip AD7887; Primary coil winding two ends link to each other with EXC2 with the output terminal EXC1 of AD598 respectively, secondary coil winding two ends link to each other with VB with the input end VA of AD598 respectively, the signal output part of AD598 links to each other with operational amplification circuit OPA177 input end, the output terminal of operational amplification circuit OPA177 links to each other with the analog input end of AD7887, and the digital output end of AD7887 links to each other with the DSP module with control end.

Two, a kind of method that improves temperature measurement uniformity of thermal infrared imager is characterized in that the step of this method is as follows:

A) the optical lens group position of adjustment thermal imaging system makes thermal imaging system focus on measured target;

B) by i * j voltage signal V that surveys in the unit in the thermal imaging circuit module collection non-refrigerating infrared focal plane _{I, j}, by the output voltage V of displacement transducer driving testing circuit module Displacement Measurement sensor _M

C) utilization of DSP module is built in calibrating parameters k and the b in the FLASH module, with V _MBe converted into the image distance l ' of thermal imaging system optical lens group,

D) use V _{I, j}And V _MCalculate the temperature T of each pixel:

Concrete computing formula is as follows:

$T=\sqrt[n]{\frac{{16l}^{\′2}\sqrt{1-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2f{l}^{\′}}F(i,j)\right]}^2}}{C{\mathrm{\π}}^2{D}_d^2{(D_L-\frac{f^{\′}}{l^{\′}-f^{\′}}{D}_d)}^{2}F(i,j)\sqrt{F(i,j)-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2f{l}^{\′}}F(i,j)\right]}^2}}{V}_{i,j}}$

Wherein $F(i,j)=\frac{{\left(l^{\′}f\right)}^2}{{\left[f^{\′}{D}_d\sqrt{{(i-\frac{M}{2})}^2+{(j-\frac{N}{2})}^2}\right]}^2+{\left(l^{\′}f\right)}^2}$

Variable in the formula: V _{I, j}Be the response voltage V of the unit of the detection on the focal plane _{I, j}I, j are pixel coordinate; L ' is an image distance;

Constant in the formula: f is the object space focal length of optical lens group; F ' is picture side's focal length; Be D _LOptical lens group diameter; D _dBe the first diameter of single detection on the non-refrigerating infrared focal plane; M, N are thermographic pixel column, columns; C is the constant relevant with the non-refrigeration focal surface material with n; These constants all are built in the program.

Described displacement transducer is tested displacement d and output voltage V in its range _MBe linear, i.e. d=kV _MThe relation of+b.

The beneficial effect that the present invention has is:

The present invention can measure the image distance value of camera lens simultaneously measuring temperature, and then the thermal imagery error of skew ray Shu Zaocheng is compensated, and obtains temperature field measurement result more accurately.

Description of drawings

Fig. 1 is that master of the present invention looks part sectioned view.

Fig. 2 is a side cutaway view of the present invention.

Fig. 3 is a top plan view of the present invention.

Fig. 4 is the stereographic map after the present invention removes shell.

Fig. 5 is a circuit structure block diagram of the present invention.

Fig. 6 is the circuit theory diagrams that displacement transducer drives the testing circuit module

Among the figure: 1, shell, 2, the infrared imaging lens group, 3, non-refrigerating infrared focal plane, 4, focusing mechanism, 5, displacement transducer, 6, shielding case, 7, sliding bar, 8, pedestal, 9, substrate, 10, web member, 11, motor, 12, threaded rod, 13, threaded hole, 14, guide pole, 15, guide pole, 16, pilot hole, 17, pilot hole, 18, thermoelectric temperature stabilizator temperature control circuit, 19, the A/D Acquisition Circuit, 20, the FPGA module, 21, the D/A modular converter, 22, the vision signal module, 23, RAM, 24, FLASH, 25, the DSP module, 26, the RS232 communication module, 27, the focusing circuit module, 28, displacement transducer drives the testing circuit module

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

As Fig. 1, Fig. 2, Fig. 3, shown in Figure 4, the present invention includes housing 1, be installed in the housing center optical lens group 2, be installed in non-refrigerating infrared focal plane 3 and motor 11, thermal imaging circuit module, Focusing mechanism and focusing circuit module 27 on the substrate 9; Shell is interior to be that the boundary can be divided in two parts with substrate 9, and wherein the latter half space is mainly used in and places all circuit modules.Displacement transducer 5 based on differential mutual inductor principle is installed on substrate, described displacement transducer 5 comprises iron core, former secondary coil winding and shielding case 6 from inside to outside successively, sliding bar 7 one ends link to each other with iron core, the other end links to each other with optical lens group 2 shells, the shielding case 6 of displacement transducer 5 is installed on the substrate 9 by pedestal 8, and former secondary coil winding drives testing circuit module 28 with displacement transducer and links to each other.

Non-refrigerating infrared focal plane 3 is installed in the middle position of substrate 2, and the place ahead is the optical lens group 2 of installing with its concentric.Motor 11 is installed in the top of substrate 2, its central shaft and optical lens group 2 axis parallels; 11 front ends of motor connect a threaded rod 12 by web member 10, and junction cover one has the web member 10 of threaded hole, and web member 10 upper screwed holes can be screwed into screw makes threaded rod 12 follow 11 rotations synchronously of motor; Threaded rod 12 is by the threaded hole 13 on optical lens group 2 shells, and when control signal drive motor 11 rotated, the rotation generation that optical lens group 2 integral body are followed threaded rod 12 moved axially, and realized focusing on thereby adjust image distance.Substrate 9 both sides respectively install and fix a guide pole 14 and 15, guide pole 14 and 15 front ends are by the pilot hole 16 and 17 of optical lens group 2 shell both sides, when motor 11 orders about optical lens group 2 when moving forward and backward, guide pole 14 and 15 guarantees not disalignment of optical lens groups 2 moving directions.

As shown in Figure 5, circuit module of the present invention comprises thermoelectric temperature stabilizator temperature control circuit 18, A/D Acquisition Circuit 19, FPGA module 20, D/A modular converter 21, vision signal module 22, RAM module 23, FLASH module 24, DSP module 25, RS232 communication module 26, focusing circuit module 27 and displacement transducer drive testing circuit module 28.Thermoelectric temperature stabilizator temperature control circuit 18 wherein, A/D Acquisition Circuit 19, FPGA module 20, D/A modular converter 21, vision signal module 22, RAM module 23, FLASH module 24 and DSP module 25 have been formed the thermal imaging circuit module.Thermoelectric temperature stabilizator temperature control circuit 18 in the thermal imaging circuit module has adopted the ADN8830 integrated circuit, and it links to each other with non-refrigerating infrared focal plane 3, and effect is to control the temperature of non-refrigerating infrared focal plane 3 near optimum temperature.The detection unit output signal of non-refrigerating infrared focal plane 3 is connected on the A/D Acquisition Circuit 19, and the concrete model of A/D Acquisition Circuit 19 is AD9240, and it is with each surveys the output voltage V of unit on the non-refrigerating infrared focal plane 3 _{I, j}Convert digital signal to and be sent to FPGA module 20.FPGA module 20 has two effects, and the one, the digital signal that A/D Acquisition Circuit 19 is sent here is carried out sending in the RAM module 23 behind the preliminary signal condition, the 2nd, for non-refrigerating infrared focal plane 3 provides correct time clock.FLASH module 24 stored program and measure needed all parameters of temperature, program and parameter are loaded in the DSP module 25 after the thermal infrared imager system start-up.Displacement transducer drives testing circuit module 28 detectable voltage signals V from displacement transducer 5 _M, being converted into digital signal then and being sent to DSP module 25, DSP module 25 is utilized V _M, V _{I, j}With the temperature value that is built in each pixel of calculation of parameter in the FLASH module 24.DSP module 25 also links to each other with focusing circuit module 27, with 11 actions of control motor thermal infrared imager is correctly focused on to measured target.FPGA module 20 is taken out treated thermal-image data from RAM module 23, deliver to D/A modular converter 21, D/A modular converter 21 is integrated circuit ADV7123, and it converts thermal-image data to simulating signal, delivers to the vision signal that vision signal module 22 generates standard again.

As shown in Figure 6, described displacement transducer driving testing circuit module 28 comprises AD598 one chip displacement of the lines differential transformer signal conditioner, operational amplification circuit OPA177 and AD conversion chip AD7887; Primary coil winding two ends link to each other with EXC2 with the output terminal EXC1 of AD598 respectively, secondary coil winding two ends link to each other with VB with the input end VA of AD598 respectively, the signal output part of AD598 links to each other with operational amplification circuit OPA177 input end, the output terminal of operational amplification circuit OPA177 links to each other with the analog input end of AD7887, and the digital output end of AD7887 links to each other with DSP module 25 with control end.

Step of the present invention is as follows:

A) optical lens group 2 positions of adjustment thermal imaging system make thermal imaging system focus on measured target;

B) by i * j voltage signal V that surveys in the unit in the focal plane circuit module collection non-refrigerating infrared focal plane 3 _{I, j}, by the output voltage V of displacement transducer driving testing circuit module 28 Displacement Measurement sensors 5 _M

C) DSP module 25 is utilized calibrating parameters k and the b that is built in the FLASH module 24, with V _MBe converted into the image distance l ' of thermal imaging system optical lens group,

D) use V _{I, j}And V _MCalculate the temperature T of each pixel:

Concrete computing formula is as follows:

$T=\sqrt[n]{\frac{{16l}^{\′2}\sqrt{1-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2f{l}^{\′}}F(i,j)\right]}^2}}{C{\mathrm{\π}}^2{D}_d^2{(D_L-\frac{f^{\′}}{l^{\′}-f^{\′}}{D}_d)}^{2}F(i,j)\sqrt{F(i,j)-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2f{l}^{\′}}F(i,j)\right]}^2}}{V}_{i,j}}$

Wherein $F(i,j)=\frac{{\left(l^{\′}f\right)}^2}{{\left[f^{\′}{D}_d\sqrt{{(i-\frac{M}{2})}^2+{(j-\frac{N}{2})}^2}\right]}^2+{\left(l^{\′}f\right)}^2}$

Variable in the formula: V _{I, j}Be the response voltage V of the unit of the detection on the focal plane _{I, j}I, j are pixel coordinate; L ' is an image distance;

Constant in the formula: f is the object space focal length of optical lens group; F ' is picture side's focal length; Be D _LOptical lens group diameter; D _dBe the first diameter of single detection on the non-refrigerating infrared focal plane; M, N are thermographic pixel column, columns; C is the constant relevant with the non-refrigeration focal surface material with n; These constants all are built in the program.

Displacement transducer 5 is tested displacement d and output voltage V in its range _MBe linear, i.e. d=kV _MThe relation of+b.

The present invention can measure the thermal infrared imager of camera lens image distance value with compensating distortion in real time.

Claims (4)

1. device that improves temperature measurement uniformity of thermal infrared imager, comprise housing (1), be installed in the housing center optical lens group (2), be installed in non-refrigerating infrared focal plane (3) and motor (11), thermal imaging circuit module, Focusing mechanism and focusing circuit module (27) on the substrate (9); It is characterized in that: the displacement transducer (5) based on differential mutual inductor principle is installed on substrate, described displacement transducer (5) comprises iron core, former secondary coil winding and shielding case (6) from inside to outside successively, sliding bar (7) one ends link to each other with iron core, the other end links to each other with optical lens group (2) shell, the shielding case (6) of displacement transducer (5) is installed on the substrate (9), and former secondary coil winding drives testing circuit module (28) with displacement transducer and links to each other.

2. a kind of device that improves temperature measurement uniformity of thermal infrared imager according to claim 1 is characterized in that: described displacement transducer drives testing circuit module (28) and comprises AD598 one chip displacement of the lines differential transformer signal conditioner, operational amplification circuit OPA177 and AD conversion chip AD7887; Primary coil winding two ends link to each other with EXC2 with the output terminal EXC1 of AD598 respectively, secondary coil winding two ends link to each other with VB with the input end VA of AD598 respectively, the signal output part of AD598 links to each other with operational amplification circuit OPA177 input end, the output terminal of operational amplification circuit OPA177 links to each other with the analog input end of AD7887, and the digital output end of AD7887 links to each other with DSP module (25) with control end.

3. method that improves temperature measurement uniformity of thermal infrared imager, the device that it uses raising temperature measurement uniformity of thermal infrared imager as claimed in claim 1 is characterized in that the step of this method is as follows:

A) optical lens group (2) position of adjustment thermal imaging system makes thermal imaging system focus on measured target;

B) by i * j in the thermal imaging circuit module collection non-refrigerating infrared focal plane (3) voltage signal V that surveys in the unit _{I, j}, by the output voltage V of displacement transducer driving testing circuit module (28) Displacement Measurement sensor (5) _M

C) DSP module (25) utilization is built in calibrating parameters k and the b in the FLASH module (24), with V _MBe converted into the image distance l ' of thermal imaging system optical lens group,

D) use V _{I, j}And l ' calculates the temperature T of each pixel:

Concrete computing formula is as follows:

$T=\sqrt[n]{\frac{{16l}^{\′2}\sqrt{1-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2{\mathrm{fl}}^{\′}}F(i,j)\right]}^2}}{{\mathrm{C\π}}^2{D}_d^2{(D_L-\frac{f^{\′}}{l^{\′}-f^{\′}}{D}_d)}^{2}F(i,j)\sqrt{F(i,j)-{\left[\frac{(l^{\′}-f^{\′})D_L-f^{\′}{D}_d}{2{\mathrm{fl}}^{\′}}F(i,j)\right]}^2}}}{V}_{i,j}$

Wherein $F(i,j)=\frac{{\left(l^{\′}f\right)}^2}{{\left[f^{\′}{D}_d\sqrt{{(i-\frac{M}{2})}^2+{(j-\frac{N}{2})}^2}\right]}^2+{\left(l^{\′}f\right)}^2}$

Variable in the formula: V _{I, j}Be the response voltage V of the unit of the detection on the focal plane _{I, j}I, j are pixel coordinate; L ' is an image distance;

Constant in the formula: f is the object space focal length of optical lens group; F ' is picture side's focal length; D _LBe optical lens group diameter; D _dBe the first diameter of single detection on the non-refrigerating infrared focal plane; M, N are thermographic pixel column, columns; C is the constant relevant with the non-refrigeration focal surface material with n; These constants all are built in the program.

4. a kind of method that improves temperature measurement uniformity of thermal infrared imager according to claim 3 is characterized in that: described displacement transducer (5) is tested displacement d and output voltage V in its range _MBe linear, i.e. d=kV _MThe relation of+b.

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