SPOT 4.1 Basic and Advanced Software Manual for SPOT Insight ...

Ch. 5 – Preparing to Take a PictureThe Thermal Frame correction data is stored as a file. The user must select it in the Image Setups optionsprior to image captures. Select the checkbox for Thermal Frame and then browse to select a ThermalFrame correction file from those that have been previously developed and stored.You may select a thermal frame to use in the subtraction process within the image set-up post-processingwindow. For a detailed description of the steps involved in acquiring a Thermal Frame, refer to Ch. 7 –Taking a Picture.InsightB/WIf 12 bit monochrome is selected as the Pixel Bit Depth on the Image Setup window, theautomatic Black Level Subtract process is always turned off when acquiring background images.Get Flatfield Image (Flatfield Correction)Flatfield correction is used to correct for display problems associated with uneven intensity or colorationin illumination, or to correct for artifacts (e.g., dust) in the optical system. For the SPOT Insight camerasthat use a color mosaic chip, flatfield correction serves another purpose. In the production process for colormosaic CCD chips, the RGB colors are applied directly to the pixels on the chip. This process often resultsin an uneven color density around the outer 30-40 rows of the CCD chip, causing a “halo” appearance insome image captures, particularly those with low contrast. The Flatfield option can be used to correct thisproblem.Note: Flatfield correction with the SPOT camera refers only to the correction of unevenlighting. It should not be confused with the correction of optical field flatness.Flatfield correction works by sampling the brightfield background without the specimen in the field ofview. This lets the SPOT software know, on a pixel-by pixel basis, which areas in the field of view arereceiving less illumination than the brightest areas. The flatfield correction function also samples thesystem offset and dark current by taking a bias frame. After the flatfield correction file is created and savedto the Image Setup, the software uses this information to accurately increase the brightness of each pixel inthe dimly illuminated areas. The resulting image gives the appearance of an even illumination.For a detailed description of the steps involved in the flatfield correction process, refer to refer to Ch. 7 –Taking a Picture.112 User Guide to the SPOT Insight Camera