Camera technology and CCD books

Reviewed by T. Nelson

Image Sensors and Signal Processing for Digital Still Cameras
by Junichi Nakamura, ed.


I n this book about the technology behind those now-ubiquitous digital cameras, written by a collection of Japanese engineers, you might expect to find paragraphs like this:

Electrons generated near the potential well being formed in the imaging region, integrates the potential well. Such the image signal charge packets that have been collected, integrated into the prescribed periodic signal charge packet is forwarded. Towards the storage area to serve as the frame memory of the analog parallel.

In fact, this $200 book (recently reduced to half price because of its age) doesn't read like a VCR manual at all. For a technical book, it's very well written. In 2006, CCDs were king and eight megapixel images were considered big. Quaint it may be, but the basic technology hasn't changed much.

If you're just a photographer, this book may be more technical than you need. There's not much about the mechanical workings of a camera. But if you're interested in the technology, this is a good starting point. It covers a much broader scope than other books, so it's not as detailed as what you'd get here or from the books by Janesick (at right). For example, the discussion of autofocusing is general and leaves out important details. The last few chapters are nontechnical and repeat material covered in the beginning. Here's what's in it:

In the future, we may see sensors in which the entire spectrum can be read out from each pixel. Each pixel will be able to select its color electronically, eliminating the need for lens filters and on-chip Bayer masks. Optical low-pass filters will no longer be needed to eliminate moiré. For sure we'll have CMOS sensors with 16-bit ADCs. But this being engineering, all these improvements will be driven by economics. Or as the authors of all those VCR manuals might have put it: However, this is to drive the economic technical all of the improvement.

oct 12 2013

Photon Transfer DN→λ
by James R. Janesick


P hoton transfer curves are essential in evaluating the performance of CCD and CMOS cameras. They provide information that technical users and designers of digital cameras need to know, such as:

This book provides the theory and a clear explanation of photon transfer curves. Numerous solved example problems are included. The reader is walked through a complete data reduction example in the Appendix. There are numerous graphs of noise sources and their effects, including simulations and real data.

Some of these techniques can be found on the Internet. But many of the Internet descriptions are oversimplified, make unwarranted assumptions of linearity, or omit important sources of noise. This book is a valuable source of practical and accurate information on measuring the noise in a digital camera.

may 28, 2012

Scientific Charge-Coupled Devices
by James R. Janesick


T his is a more thorough investigation of the sources of charge generation, charge collection, charge transfer, charge measurement, and noise in CCD sensors, written in 2001 by author of Photon Transfer DN→λ. The treatment is more theoretical and gives fewer details about photon transfer curves, but more details about damage by cosmic rays and X-rays, the effects of temperature on read noise, and use of CCDs in a space environment.

Scientific cameras, such as those installed on the Hubble and the Cassini probe, have driven CCD technology forward. Even though the technology has progressed considerably since this book was written, to the extent of becoming commoditized, the basic technology is still the same. The book is packed with equations, graphs, diagrams, and grayscale photos.

Most CCD modifications, such as backside thinning, QE-pinning, and application of AR coatings, have to be done during manufacture. But Janesick builds and troubleshoots CCDs for a living, and his enthusiasm for how CCDs work in the real-world shows. For example, on page 179 he says that writing on a frontside-illuminated CCD with a yellow highlighter pen extends its quantum efficiency into the far UV (down to 500Å), because the highlighter acts as a phosphor coating. Contrary to popular belief, CCD "amplifier glow," a common problem in many early cameras, is not caused by heat, he says, but by NIR luminescence caused by impact ionization in the transistors, which can act like small infrared LEDs.

Even though only six years passed between this book and Photon Transfer, the pace of technological change has been enough to shift the grayscale value of the author's hair well to the right. Solved example problems are included. CCD driver circuits and electron-multiplying CCDs are not discussed.

jul 04, 2012