Mekanisk integration av en IR-detektor i en Stirlingkylare

Sammanfattning

The master thesis ”Mechanical Integration of an IR-detector in a Micro Cooler” has been

performed at FLIR Systems AB in Danderyd. FLIR Systems is a world leader in the design,

manufacture and marketing of thermal imaging camera systems.

The thesis project is divided into to two areas, Production Method and Noise.

The Production Method concerns the positioning of a detector on the cold finger within the IRcamera.

The detector has to be positiond with very high accuracy at the center of the cold finger,

so it can be placed in line with the optical axis to avoid movement of the picture during zooming.

The positioning of the detector is at present done with the help of specially designed guides on a

plate on top of the cold finger. The design workes well but the special machining needed for this

plate is very expensive.

The goal concerning the production method was to derive a new more cost effective method for

the assembling and positioning of the detector on the cold finger by replacing the guides on the

plate with a reusable equipment or some other alignement operation.

Several concept ideas have been generated with the help of concept generation methods in the

form of concept classification trees and concept combinational tables. Two of these concepts

were selected to be further refined. The selection was done with the help of a concept scoring

method and a concept evaluation meeting. In the first concept the detector is positioned with the

help of a microscope and in the second with the help of an external fixture. A prototype of the

fixture has been manufactured and an evaluation was done concerning function and price

aspects. This showed that the positioning of the detector will be good and the assemblers were

positive towards the fixture and the handling of it. The investment of the fixture will be returned

compared to the plate with the guides after only four assembled detectors.

The Noise part of the thesis concerns a disturbance that sometimes can be seen in the picture.

This disturbance, here called flicker, seem to be generated by the Stirling micro cooler since the

frequency of the flicker follows the frequency of the cooler. The cause of this flicker is unknown

despite numerous of studies. The goal concerning the noise was to do studies in order to confirm

or refute some hypothesis. Experiments, simulations and calculations have been done to analyse

the deformations in the detector caused by pressure pulsations and the effects on the detector by

vibrations of the cold finger caused by the Stirling micro cooler. However these studies did not

give a clear conclution to the cause of the flicker and therefore further studies have to be done.