Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

1 / 27

Toolkit for testing CCD cameras

Janusz Użycki

Faculty of PhysicsWarsaw University of Technology

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

2 / 27

CCD matrix(Charge-Coupled Devices)

CCD sensors are produced in full choiceof resolution and dimenstions. They areaccessible with diameter bigger than half inch.It is very important in professional astronomyapplications. The CCD sensors are low noiseand have high sensivity.

selected resolution: 2048 x 2048 pixels,15 x 15m each

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

3 / 27

How it worksmain idea of readout

from CCD sensor

charges vs light

making a photoexposure timephotons

empty

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

4 / 27

How it works

horizontal shift of charges

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

5 / 27

How it works

vertical shiftof chargesin a queue

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

6 / 27

How it works

ADCamplifier

video signal

readouthorizontal shift

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

7 / 27

How it works

p

n SiO2

cross-section

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

8 / 27

How it works

Inserting a charge into the CCD matrix

p

n

the charge inserting

egde barier

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

9 / 27

How it works

Potential well

confinement

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

10 / 27

How it works

three phases

clock signals

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

11 / 27

How it works

three stagesof chargemovingprocess

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

12 / 27

Consequence of usage the CCDWe 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.

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

13 / 27

Solutions

- cold environment (about -10C)- noise and infra-red radiation reduction- statistical methods for analizing „black / dark photos” – finding the best parameters

Example:

CCD amplifier ADClight readout

What is a total gain of the circuit?

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

14 / 27

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 packageand Microsoft Visual C++.

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

15 / 27

Requirements – continuation (1)

- read images in fits

astronomical format which is used by our aparature (there are raw data from the CCD)

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

16 / 27

Requirements – continuation (2)

- eliminate the offset and ‘hot’ pixels

by substraction of two successive images

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

17 / 27

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

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

18 / 27

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

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

19 / 27

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.

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

20 / 27

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

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

21 / 27

CCD Toolkitin action

examples of print-screens

main window(management)

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

22 / 27

CCD Toolkit

in action

previewwindow(enlargement)

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

23 / 27

CCD Toolkit

in action

histogramsfor XY& profiles

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

24 / 27

CCD Toolkit

in action

profiles(projections)

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

25 / 27

CCD Toolkit

in action

afterdivisioninto regions

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

26 / 27

CCD Toolkit

in action

mean

sigm

a

exampleof badgain fittingreason: offset

Toolkit for testing CCD cameras – one of tools „Pi of the Sky” project

Wilga 2005

27 / 27

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