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The technique of coupling Fiber optic taper to CCD is the key technique of Developing ICCD image sensor.Compared with traditional lens imaging system,the FOT x CCD system has a higher coupling efficiency and it can greatly minimize the size and weight of camera.When CCD is coupled to Fiber Optic Taper,there exist 2 layers.
1) the non-contact area between CCD light sensitive area and sealed silica window. 2) the layer between fiber optic taper’s output and sealed silica window
Any position changes in these two layer will affect the imaging performance of the system.
Here we’re using taper with 2:1 tapered ratio. (with 4um fiber size at small end, 8um fiber size at big end). Area array CCD (1/3″ B/W CCD camera, pixel count 542(H) * 492(V)).
First we will remove the CCD’s silica window,and use Alignment adjustment system,to make Fiber optic taper directly coupling on the CCD’s light sensitive area.Coupled result as followed.
CCD coupled with FOT
Through the CTF curve of CCD camera before and after FOT coupled,we can find following elements which affect the performance of imaging.
CTF curve - FOT x CCD
The malposition between pixel will result in greatly decrease of components’ resolution.We could make fiber size smaller and use a High-precision alignment system to reduce the resolution decrease after coupled.
Coupling components’ CTF is decrease greatly in the High frequency stage.This is mainly because stray light escape from Fiber can not be absorbed immediately by the EMA absorber around the fiber.So the improvement of absorb to stray light is also very important. And we could improve the aperture of Fiber Optic Taper,which could improve coupling efficiency and control the stray light. Also, distortion problems should be considered during the production process.