It’s the weekend again, and today a quick checklist will help us understand the principles of infrared optical system design. Hope to be able to help friends!

1. When designing an infrared optical system, the infrared radiation energy is more concerned by the designer, and it is also the key factor of the entire system.

2. At present, there are two main ideas for reducing the loss of infrared light energy.

First of all, the infrared imaging system uses the photosensitive area array to receive the infrared radiation energy from the outside world, and then converts the analog signal in the circuit into a digital signal through the readout circuit. There will be a lot of energy loss in the process of signal conversion, so we need to simplify the system as much as possible. structure to improve the conversion rate of energy.

Secondly, when infrared light passes through the optical lens of the entire system, the infrared radiation energy will be absorbed by the crystal material, resulting in a low overall infrared light transmittance. The current effective solution is to coat some anti-reflection coatings on the mirror surface to improve the transmittance of infrared light.

3. In order to receive the infrared radiation from the target as much as possible, it is necessary to appropriately expand the receiving aperture of the optical system and the size of the photosensitive surface of the infrared detector within the scope of the lens size and processing accuracy, so as to improve the sensitivity of the system.

4. In the design, we need to focus on the matching between the various parts of the system, mainly the matching between the optical system and the detector and the matching between the detector and the readout circuit. The system spatial resolution, aperture size and other conditions should be considered between the optical system and the detector. The cooling detector also needs to analyze the design position of the cold diaphragm, so as to achieve 100% efficiency of the cold diaphragm. In addition, refrigeration detectors need to use a refrigerator to cool down, and at the same time, a large amount of external noise will be introduced. Therefore, the infrared optical system needs to improve the ability to suppress noise as much as possible, and improve the signal-to-noise ratio of the system.

5. When designing the overall structure of the system, the area of ​​the entire photosensitive surface should be fully and reasonably used, and the light spot should be imaged uniformly on the photosensitive surface as much as possible, so as to improve the utilization rate of the system from all aspects.

6. Thermal difference in infrared optical imaging is a key factor affecting the imaging of the system, which must be considered in the design. Among them, when the working temperature of the detector changes, the refractive index and shape of the crystal material of the mirror surface in the transmissive structure will change significantly, resulting in a serious drift of the better imaging image surface of the system. Therefore, it is necessary to eliminate the influence of thermal difference on the imaging of the system to ensure the normal operation of the system within the specified temperature range.

Designing optical systems requires excellent aids. Among the many optical software, Zemax is a set of optical design software that attracts much attention. It integrates the concept, design, optimization, analysis, tolerance analysis and documentation of optical systems. Zemax officially released the new version 21.3 not long ago! The new version supports modeling the complex geometries required for the miniaturization of next-generation optical systems.

The Links:   CM20MD-12H LQ10D031 IGBTMODULE