You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither SPIE nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the SPIE website.
Chapter 6: Automatic Calibration and Error Correction
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print format on
SPIE.org.
Abstract
Image sensor professionals working regularly with digital image sensors should understand that medium- to high-resolution ADC architectures will need some form of linearization processing in order to generate acceptable linearity for image sensor applications. Linearization is performed on chip for commercial stand-alone ADCs and is transparent to the user. In many academic papers, linearization post-processing is often carried out in software long after conversion; however, this technique is slow and not suitable for any sort of real-time or production-quality image sensor system. Image sensor ADC linearization can be performed on the image sensor chip itself, as is done for ADC stand-alone products, or in the image post-processing electronics operating on the image data in real time, as long as the ADC data stream has been designed to accommodate this post-processing.
In the author’s experience, image sensor electronics professionals do not wish to incorporate ADC linearization schemes into the already complex image processing routines running on external processors. This minimizes the number of necessary feedback loops between the image sensor ADCs and external hardware. However, keeping processing off the image-sensing chip can be an important power-saving feature for specialty systems such as infrared focal plane arrays operated at cryogenic temperatures. Again, in the author’s experience, it is worthwhile to linearize the ADC data on the imagesensing chip, even for most cryogenically cooled parts, to enable certain onchip video processing and minimize the complexity of the external video processing engine. The author has found two types of image sensor chips for which the tradeoff is not always obvious. The first is the radiation-tolerant class of parts, where memory can become corrupted by single-event upsets, and external hardened RAM in triplicate provides additional reliability. The second is large digital pixel sensors, where calibration constants are needed for each pixel, and an on-chip secondary memory array might not be worth the circuit area. Whatever type of image-sensing system, it is important for image sensor professionals to understand the complexity of ADC linearization in order to make a good decision about the value of on-chip processing or offchip processing of their ADC data.
Online access to SPIE eBooks is limited to subscribing institutions.