Course #14

Digital Camera Systems

Oct 25-28, 2010. Barcelona, Spain

INSTRUCTOR
Professor Dr. Albert J. P. Theuwissen, 
Delft University of Technology, The Netherlands
Harvest Imaging, Belgium

TECHNOLOGY FOCUS 
Digital cameras are an essential part of our daily life, e.g. in mobile phones, camcorders, digital photography, cars, and in imaging applications for medical, industrial and broadcasting industries. All these camera applications rely on the solid-state image sensors. 

However, if consumers were forced to choose a digital camera on the basis of the raw data produced by the imager, it would be very doubtful that anyone of us would buy a digital camera. The data produced by a solid-state image sensor is contaminated by various noise sources, by defects, by inconsistencies, and 
many other error sources. To make matters worse, the solid-state image sensors do not themselves produce a coloured image. It is the data processing that must correct all these potential errors and even regenerate the colour information in the post-processing stage. So, what a person actually sees on a display or hard copy is absolutely not the same as what the imager has captured. Luckily - " What you see is not what you got!” 

As we can foresee that our homes, offices and cars soon will be fully equipped with cameras to make life safer and more enjoyable and to reduce our workload, we can recognize the digital camera technique as a forefront technology. Even today, for many applications imaging is in the embryo stage of its development. 

COURSE CONTENT AND OBJECTIVES 
This course will focus on the overall system aspects of digital cameras. The complete path from “photons-in” to“digital-numbers-out” will be discussed.The effect of light sources, optics, imagers, defects, and data processing will be covered. Computer animations and simulations will be used to achieve a realistic understanding of details and shortcomings in digital cameras. Many examples of images will be used to explain the various issues. No detailed knowledge of device physics is assumed. It is complementary and completely different from Courses #13 and #20. 

Monday 

The Image Sensor, the Optics, Image Processing: A Review 
The course begins with a brief overview of the basic theory of solid-state image sensors. The imager is of course only a small, but vital, component of the complete camera system. The effect of the spectral content of the light sources will be discussed. Lectures on optics and on digital image processing are included to form a strong backbone for the remaining parts of the course. 

Image Quality 
Noise, defects, irregularities of the video signal, and inconsistencies can all deteriorate the quality of the image. We will discuss where these problems come from and how they can be corrected. The dilemma that correcting one effect can have a negative impact on some other camera parameters will be discussed. 

Theoretical Calculations 
The first day of the course will end with a few calculations: How many Volts-out will a camera deliver for a single photon-in? 

Tuesday 

Digital Camera Systems 

• Dark Current Compensation: The average value of the dark current can be corrected by the use of dark-reference lines/pixels. Fixed-pattern noise can be 
  corrected by means of dark frame subtraction. How efficient are these techniques? What is their influence on signal-to-noise performance and what 
  about temperature effects? 
• Colour Interpolation: The Bayer pattern sampling is extensively used in digital 
  imaging, but the sampling is only half of the story. The other half is the demosaicing or interpolation. Several methods will be discussed and compared with each other. 
• White Balancing: The human eye is adapting easily and quickly to the spectrum of a light source, the image sensors do not adapt at all! How can we deal with this “shortcoming” of the imagers? 
• Defect Correction: How can defect pixels be corrected without any visible effect? Can similar techniques also be applied to correct defect columns? 

Wednesday 

Digital Camera Systems (cont´d) 

• Noise Filtering: A very important issue in data processing is the filtering of any remaining noise. This can be done in a non-adaptive or an adaptive way. What are the pros and cons of the various techniques? 
• Colour Matrixing: Nobody is perfect, neither are the imagers that suffer from optical cross-talk and from imperfections when it comes to the transmission characteristics of the colour filters. Colour matrixing takes care about these issues. Question is how to find to optimum correction matrix coefficients? 
• Contouring: This is a technique to “regain” details, edges and sharpness in an image. But quite often not only the details are enhanced, but the noise in the image as well. Various contouring techniques will be discusses and compared with each other. 

Thursday 

Digital Camera Systems (cont´d) 

• Lens-Vignetting: Lenses have a strong fall-off of intensity and sharpness towards the edges. On top of that, also the image sensor will add an extra fall-off of intensity. Is correction possible? How complicated needs the correction to be to become invisible for the observer? 
• Auto-focusing: How can the data of the image sensor itself being used to activate the auto-focusing function? 
• Auto-exposure: How can the data of the image sensor itself being used to optimize the exposure time of the imager? 
• Gamma Correction: How to adapt the brightness of the output device to the characteristics of the human eye? 

How to measure the various camera characteristics? 
The course ends with an extended chapter on how to measure the various parameters of a digital camera. This chapter will be used as a kind of wrap-up of the course and in the mean time, extra information will be provided on how to characterize the main characteristics of a digital camera and how they can influence each other. 

Regular Course Fee: EUR 2490

Early Registration Course Fee: EUR 2240
This applies to firm registrations received 2 months before course start. 

University Student and Faculty Rate:
Two university participants are welcome to attend for one course fee if payment is to be made from university funds.

Deliverables:
The course fee covers tuition, course material, and the day conference packages (morning/afternoon refreshments, lunches etc.),  paid on your behalf to the course venue. Accommodation is not included.

Payment should be made before course start.