CCD Camera Design
Camera Construction Techniques 1.
The photo below shows a scientific CCD camera in use at the Isaac Newton Group. It is
approximately 50cm long, weighs about 10Kg and contains a single cryogenically cooled CCD.
The camera is general purpose detector with a universal face-plate for attachment to various
telescope ports.
Mounting clamp
Pre-amplifier Pressure Vessel
Vacuum pump port
Camera mounting
Face-plate.
Liquid Nitrogen
fill port
Camera Construction Techniques 4.
A cutaway diagram of the same camera is shown below.
Thermally
Insulating
Pillars
Electrical feed-through
Vacuum Space
Pressure vessel
Pump Port
Telescope beam
Face-plate
CCD
Focal Plane
of Telescope
Optical window
...
CCD Mounting Block Thermal coupling
Boil-off
Nitrogen can
Activated charcoal ‘Getter’
Camera Construction Techniques 5.
The camera with the face-plate removed is shown below
CCD
Retaining
clamp
Temperature servo circuit board
Aluminised Mylar
sheet
Gold plated copper
mounting block
Top of LN2
can
Platinum resistance
thermometer
Pressure
Vessel
‘Spider’.
The CCD mounting
block is stood off from
the spider using
insulating pillars.
Location points (x3)
for insulating pillars
that reference the CCD
to the camera face-plate
Signal wires to CCD
Camera Construction Techniques 6.
A ‘Radiation Shield’ is then screwed down onto the spider , covering the cold components but
not obstructing the CCD view. This shield is highly polished and cooled to an intermediate temperature
by a copper braid that connects it to the LN2 can.
Radiation Shield
Camera Construction Techniques 7.
Some CCDs cameras are embedded into optical instruments as dedicated detectors.
The CCD shown below is mounted in a spider assembly and placed at the focus of a
Schmidt camera.
CCD Signal connector (x3)
Copper rod or ‘cold finger’
used to cool the CCD. It is
connected to an LN2 can.
‘Spider’ Vane
CCD Clamp plate
Gold plated
copper CCD
mounting
block.
FOS 1 Spectrograph
CCD Package
Infrared Camera Design
Differences to CCD cameras
Basic Optics
Example: NIRI
Gemini Near-Infrared Imager
(NIRI)
K. W. Hodapp, J. Hora, E. Graves,
E. Irwin, H. Yamada, D. Neill
J. Douglass, K. Fletcher, T. Young
R. Chung, L. Robertson
Institute for Astronomy
NIRI
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1.0 - 5.5 m Imager for Gemini North
3 Cameras: 117, 50, 22 mas/pixel
Polarimetric Capability
Grism Spectroscopy
Coronographic Capability
Pupil Viewer
IR On-Instrument Wavefront Sensor
Technical Challenges
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Minimize Flexure
Lens Mount for Fast and Aspheric Lenses
Bearings
Bushing Material Selection
Filter Wheel Design
Connector Corrosion
NIRI
OIWFS:
Detector: HAWAII-1 engineering grade
Readnoise: 7 e- rms
(sub-arrays, multi-sampled)
Near-infrared Imager (NIRI)
HAWAII-1 Detector
OIWFS gimbal
NIRI OIWFS
• HAWAII-1 detector used in
combination with a SH on
instrument wavefront sensor to
provide fast tip/tilt/focus
• Demonstrated to work down to
J~15 mag stars at 100 Hz
• Gimbal mirror at pupil used to steer
guide stars across ~3.5 arcmin FOV
into OIWFS
• Improved sky coverage vs. optical
sensing
• Permits wavefront sensing in “dark
clouds”
NIRI
Science Module Detector:
Aladdin II
10241024 InSb detector array,
27m pixels
Readnoise: 20 e- rms multi-sampled
Dark Current: 0.2 e-/s (30 K)
NIRI: f/6 optical path
NIRI f/6: spot image in corner
NIRI f/32: spot image K’
NIRI f/32: spot image M’