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The Use of our Cover Slips - Our Perspective

Many sensors are available with either a 'permanent' or 'taped' cover slip. The 'taped' cover slip is removed prior to final camera assembly. The 'permanent' cover slip cannot be removed and is left on for the life of the camera. Unfortunately 'permanent' cover slips have detrimental effects on the final image (see the "Internal Reflections" discussion below). The decision of which sensor cover slip version to use is left with our customers. 

Cover Slips - Manufacturing Implications

Manufacturing cameras without cover slips places a premium on quality control and manufacturing techniques. That being the case we firmly believe that the extra efforts are worth it as the customer will ultimately receive the best imaging system for their application. Feel free to contact FLI should you need assistance in making this critical decision. 

FLI will place either version into your camera at no extra cost. 

The test below is an application where a non-cover slip imaging system is advantageous

Internal Reflections

The image below is a comparison of two cameras using identical sensor types. One of the cameras has a KAF-3200ME with a "Sealed AR Coated Glass" cover slip installed. The second camera has a KAF-3200ME with a “Clear Taped Glass" cover slip which was removed during  installation into the camera.

Image Information

·         Cover Slip Sensor:                  Grade 2

·         Non-Cover Slip Sensor:         Engineering Grade

·         Image Exposure:                    60 seconds

·         Filters used:                            None

·         Object:                                     Scheat {Beta Pegasi}

·         Telescope:                               Takahashi FSQ106N at f/5

·         Focuser:                                   DF-2

·         Software:                                 Maxim DL 4.03


Please note the field rotation which occurred when the cameras were switched

The effect of the cover slip is clearly seen as an expanding cross pattern with multiple reflections extending left and right of the star.  Although there is a glow around the bright, saturated star in the right image, there is no hint of these reflections. 

A sensor's QE is lower when used with any cover slip

Along with the potential of internal reflections discussed above, there is another reason to consider using a digital imaging system that does not employ a permanent sensor cover slip: a sensor's QE is lower when a cover slip is used (up to nearly 8% lower). The actual loss is dependant upon the cover slip's material but ANY digital imaging system using a sensor with a cover slip will suffer QE losses that an identical imaging system without a cover slip will not.