{"id":1154,"date":"2013-04-22T16:00:35","date_gmt":"2013-04-22T16:00:35","guid":{"rendered":"http:\/\/harvestimaging.com\/blog\/?p=1154"},"modified":"2013-04-22T16:00:35","modified_gmt":"2013-04-22T16:00:35","slug":"how-to-measure-non-linearity-3","status":"publish","type":"post","link":"https:\/\/harvestimaging.com\/blog\/?p=1154","title":{"rendered":"How to Measure Non-Linearity ? (3)"},"content":{"rendered":"

After checking out the linearity of the sensor\/camera with a gain set to unity, in this blog the linearity will be checked in the case the sensor\/camera gain is set to 2 and 4.\u00a0 In all three cases (gain = 1, 2 and 4) the linearity will be checked for an output swing of the sensor between 10 % and 90 % of the saturation level.\u00a0 Figures 1-3 contain the obtained results.<\/p>\n

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Figure 1 : Camera output and INL for an output range between 10 % and 90 % of saturation and a sensor\/camera gain setting equal to 1.<\/em><\/p>\n

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Figure 2 : Camera output and INL for an output range between 10 % and 90 % of saturation and a sensor\/camera gain setting equal to 2.<\/em><\/p>\n

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Figure 3 : Camera output and INL for an output range between 10 % and 90 % of saturation and a sensor\/camera gain setting equal to 4.<\/em><\/p>\n

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Some remarks :<\/p>\n

–\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 All output signals in all figures have a fairly abrupt transition from their linear behaviour towards saturation.\u00a0 This is due to the fact that the ADC is defining the maximum output signal and not the pixel or the source-follower.\u00a0 This was already the case with the measurements presented in the previous blog with gain = 1.\u00a0 So by increasing the gain of the sensor\/camera, this saturation effect does not change,<\/p>\n

–\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 All definitions used in this characterization of the INL are described in the previous blogs,<\/p>\n

–\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 The results reported here come from an group of 50 x 50 pixels, and the graphs show the average non-linearity of these 2500 pixels,<\/p>\n

–\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 The three graphs show (more or less) a similar behaviour of the non-linearity.\u00a0 It should be noted that not only the gain of the sensor\/camera is changed, but also the amount of light is changed by adapting the exposure time.\u00a0 The light source itself is not changed.\u00a0 Although the graphs have a different horizontal axis, all three of them :<\/p>\n