Toolkit for testing CCD cameras Janusz Użycki Faculty of Physics Warsaw University of Technology Strona tytułowa

CCD matrix (Charge-Coupled Devices) CCD sensors are produced in full choice of resolution and dimenstions. They are accessible with diameter bigger than half inch. It is very important in professional astronomy applications. The CCD sensors are low noise and have high sensivity. selected resolution: 2048 x 2048 pixels, 15 x 15m each

How it works main idea of readout from CCD sensor making a photo exposure time photons charges vs light empty

How it works horizontal shift of charges

How it works vertical shift of charges in a queue

How it works video signal ADC amplifier horizontal shift readout

How it works p f1 f3 f2 n SiO2 cross-section

How it works the charge inserting p n egde barier Inserting a charge into the CCD matrix the charge inserting p f1 f3 f2 n egde barier

How it works Potential well confinement

How it works three phases clock signals

How it works three stages of charge moving process

Consequence of usage the CCD We had to use own Problems - the CCD matrix - control circuits - video signal amplifier analog to digital converter (ADC) noise, temperature of an environment, dark current, ‘hot’ pixels, sensivity gradient to find the best timmings noise, gain selection digitalization effects: offset, non-linearity etc.

Solutions - cold environment (about -10C) - noise and infra-red radiation reduction - statistical methods for analizing „black / dark photos” – finding the best parameters Example: CCD amplifier ADC light readout What is a total gain of the circuit?

Requirements for the toolkit for testing CCD cameras designed for PC platform: Windows XP and 2000 systems (main platform for electronics) Linux system possible It was used ROOT library package and Microsoft Visual C++. Punkt drugi planu prezentacji

Requirements – continuation (1) read images in fits astronomical format which is used by our aparature (there are raw data from the CCD)

Requirements – continuation (2) eliminate the offset and ‘hot’ pixels by substraction of two successive images

Requirements – continuation (3) display pictures the preview allows to find main errors instantly cut egdes for analize to find the best useful part of view

Requirements – continuation (4) XY histogram single pixel distribution it allows to find min/max brightness of view X and Y profile (sum or average) to find unvisible errors, dark current effect for example

Requirements – continuation (5) X and Y profile (projection) histograms divide the image into regions and make single pixel histograms, fit Gauss distribution parameters (mean and sigma values) We can estimate where is a bad region.

Requirements – continuation (6) plot chart in mean and sigma axis to fit gain line and pitch of one (tangens of angle) Here is an answer for question: What is a total gain of the circuit? electrons / ADU value = pitch of the line

CCD Toolkit in action examples of print-screens main window (management) Trzeci punkt planu prezentacji

CCD Toolkit in action preview window (enlargement)

CCD Toolkit in action histograms for XY & profiles

CCD Toolkit in action profiles (projections)

CCD Toolkit in action after division into regions

CCD Toolkit in action example of bad gain fitting reason: offset sigma mean

Summary program is still testing and it will be developing and improving if necessary - there is a lot of work for tuning the best parameters for our new cameras