Compensation for Vanadium Oxide Temperature with Stereo Vision on Long-Wave Infrared Light Measurement

Abstract

In this paper, using automated optical inspection equipment and a thermal imager, the position and the temperature of the heat source or measured object can effectively be grasped. The high-resolution depth camera is with the stereo vision distance measurement and the low-resolution thermal imager is with the long-wave infrared measurement. Based on Planck's black body radiation law and Stefan-Boltzmann law, the binocular stereo calibration of the two cameras was calculated. In order to improve the measured temperature error at different distances, equipped with Intel Real Sense Depth Camera D435, a compensator is proposed to ensure that the measured temperature of the heat source is correct and accurate. From the results, it can be clearly seen that the actual measured temperature at each distance is proportional to the temperature of the thermal image vanadium oxide, while the actual measured temperature is inversely proportional to the distance of the test object. By the proposed compensation function, the compensation temperature at varying vanadium oxide temperatures can be obtained. The errors between the average temperature at each distance and the constant temperature of the test object at 39 °C are all less than 0.1%.

Keywords: Planck’s blackbody radiation law; Stefan–Boltzmann law; binocular stereo vision; image interpolation; structured light stereo vision.

Figure 1

Integrated diagram of the four coordinate systems.

Figure 2

Relationship of world coordinate system and camera coordinate system.

Figure 3

Schematic diagram of $\varphi$ degree rotation around the z-axis.

Figure 4

Relationship of camera coordinate system and image coordinate system.

Figure 5

Relationship of image coordinate system and pixel coordinate system.

Figure 6

Schematic diagram of image interpolation method. The blue pixels are the original image, and the yellow pixels are the added pixels after processing.

Figure 7

Characteristics of nearest neighbor interpolation method.

Figure 8

Schematic diagram of the nearest neighbor interpolation method with isometric interpolation.

Figure 9

Experiment setup.

Figure 10

Normalized response of the VOx sensor.

Figure 11

Experimental environment. (a) Experiment hardware including thermal radiation camera and visible light camera fixed in the wind tunnel. (b) Heating target platform and chip in the wind tunnel.

Figure 12

Imaging of the integrated thermal sensors and deep camera in the experiment. (a) Visible light camera image, (b) depth camera image, and (c) thermal imager image.

Figure 13

Comparison of the temperature data collected by the deep thermal imaging system without compensation.

Figure 14

Compensation results of the depth thermal imaging system at various distances.