The Design and Assembly of Infrared Zoom Lens with Replicate Structure

With the rapid development of optical remote sensing technology, the micro or small remote sensors are widely used in aerospace and other military technical fields. Due to the structure space limitation of micro or small remote sensor and the needs of performance indicators, an infrared lens with replicate structure which is containing two mirrors is designed. The infrared lens can realize the zooming function by optical path automatic switching system, driving by the rotating motor. It not only can provide a large field of view for the pilot in the cruise, but also can switch to a small field of view with high resolution when the target is found. The lens has the characteristics of multi zoom, high image quality, small size and so on. But, compared with the traditional lens, the infrared zoom lens with replicate structure is more complex in structure. Therefore, it puts forward higher requirements on assembly. So, based on the traditional assembling for infrared lens, one method that contains computer-aided alignment and center error of the replicate structure is brought in practical engineering. Firstly, through the eccentric sensitivity for each lens is simulated and analyzed, the alignment priority is decided. Secondly, after the mirrors were fixed, the Opti-Centric IR which is a center error measuring instrument for infrared lens is used to complete the high precision assembling of one optical path which contains all of the lenses. Finally, when the infrared zoom lens is assembled, the imaging quality and the effective focal length of all optical path of the lens are measured in an infrared Modulation Transfer Function (MTF) measurement instrument. The result shows that the design of the infrared zoom lens with replicate structure is reasonable and feasible, and the method is successful and effective to assemble the infrared zoom lens with replicate structure. So the lens with this kind of structure can be widely used in the micro or small remote sensors.