For better fusion, the fusion system front-end detector must meet two basic requirements: a) both must have nearly the same field of view; b) the optical axes of both must be parallel. The first requirement can be achieved by selecting the lens with the right focal length. In this system, the infrared detector is 320 × 240 pixels, the pixel pitch is 45μm; the CCD of the low-light TV is 1/2 inch, and the focal length of the infrared lens is 55mm, so in order to ensure that the two have the same field of view, The focal length of the low-light lens is about 24.5mm. With precise optical design and high-precision optical processing, infrared and low-light objective lenses with approximately the same field of view can be obtained.
In order to ensure accurate registration of dual-source images from near to infinity, when fixing two kinds of detectors, precise optical axis adjustment must be performed to make the two optical axes parallel to ensure the consistency of the viewing direction. The optical axis adjustment instrument is a "multi-spectral optical system optical axis parallelism test device". The instrument can adjust the optical axis from visible light to far infrared, and the adjustment accuracy (optical axis angle) is 0.1 milliradians. When the cross target is applied with a voltage, the cross target will heat up, and the generated thermal radiation is received by the infrared detector, thereby displaying a cross-dotted line on the infrared detector. After the low-light source illuminates the cross target, the low-light detector can detect the shadow of the cross-dotted line.
When using the low-light observer and the thermal imager to observe the same far enough point target at the same place and the corresponding allowable illuminance, if the image of the point falls on the intersection of the cross-dotted lines of the instruments to be calibrated respectively Above, it indicates that the optical axes after adjustment of the instrument are parallel. Otherwise, using the characteristics of the off-axis parabolic mirror, place the cross-dash line at the focus F, and immerse the objective lens of the instrument in the collimated beam. The cross-point observed is equivalent to the observation in the field. Long distance goal. Measure the deviation between the intersection of the target crosshair in the field of view and the intersection of the cross-line of the instrument, and adjust each instrument so that the two crosshairs coincide and then lock to maintain the accuracy of the calibration. The center positions of the images captured by the two observers coincide.