Breakthrough QSI image quality for high speed applications with a large 4.2MP sensor
The QSI 640 model camera employs a 4.2mp Kodak interline transfer CCD image sensor with microlens technology. The increased Field of View, high quantum efficiency, wide dynamic range, dual read rates, low noise performance and internal 5 or 8-position color filter wheels make the QSI 640 ideally suited to a broad range of demanding scientific, medical, astronomical, and industrial imaging applications.
The compact design of the QSI 600 Series allows the 640 to set a new benchmark for cost and size in a high performance, full-featured scientific CCD camera. With optional features and upgradeability, the QSI 640 can be tailored to fit your needs today and in the future.
The 640 camera system is supported by industry leading image acquisition software plus a full camera control API is available for creating custom Windows or Linux applications.
High Performance CCD Image Sensor
Large 4.2mp Image Sensor
The large 2048×2048 sensor in the QSI 640, shown to the left approximately life size, provides unprecedented field of view in a camera using standard 1¼” filters.
The compact design and internal color filter wheel of the QSI 640ws allows unvignetted, filtered images even with very fast optical systems.
The QSI 640 camera employs a Kodak KAI–04022 4.2 megapixel interline transfer CCD image sensor with microlens technology. It has excellent quantum efficiency between 350nm and 1000nm with significant enhancement at the blue end of the spectrum. Low dark current and high pixel charge capacity result in a dynamic range exceeding 74db. The sensor employs a vertical overflow drain that provides both antiblooming protection and a fast electronic shutter. Micro lenses cover the surface of the CCD to focus the light into each 7.4µm pixel to increase optical response. See the Specifications tab below for additional details.
With the fast electronic shutter and 8MHz High Speed read mode, the QSI 640 can produce frame rates of up to 15 frames per second (fps) when reading a Region of Interest (ROI), or 5 fps for low resolution full-frame 16-bit images.
Leading Edge Technical Performance
Two separate analog processing chains, providing dual read rates, allow the QSI 600 Series to meet two seemingly incompatible imaging goals. The QSI 600 Series High Quality mode provides the highest possible Signal to Noise Ratio (SNR) for applications that require the lowest noise and widest possible dynamic range. High Speed mode has a read rate of 8MHz providing high speed reads at multiple frames per second. The read mode is easily changed under program control providing exceptional flexibility it tuning the camera’s performance to the desired imaging goals.
- All significant performance characteristics, including Linearity,Read Noise, and Photon Transfer (Gain), are tested and confirmed during manufacture. Each camera’s timing and voltages are carefully set during manufacture to ensure maximum Charge Transfer Efficiency, and to minimize charge injection and other secondary noise sources. QSI’s exclusiveResearchSpec® profiling ensures optimal performance in every camera.
- Sophisticated mixed-signal design practices are utilized throughout the camera. This permits a very compact design while eliminating interference from conducted and radiated noise. ROHS compliant multi-layer circuit boards and surface-mount components are used exclusively. A unique circuit board stacking methodology eliminates interconnecting wires that could reduce reliability.
- A carefully designed and isolated switching power supply generates all of the voltages needed to operate the camera from a single 12VDC power source. Low noise design practices and advanced filtering techniques completely eliminate any measurable impact on camera noise performance.
- Arguably, the most important aspect of a CCD camera design is the video processing subsystem. This is where almost all of the camera’s performance characteristics are established. The 600 Series video processing begins with a very low noise, precision preamp to accurately amplify the microvolt level pixel signal from the CCD image sensor. This signal is then processed through a Correlated Double Sampler (CDS) to reduce temporal read noise in the pixel signal. Subsequent signal conditioning then feeds the pixel level to a high-speed, precision 16 bit Analog to Digital Converter (ADC) where it is converted to a digital value between 0 and 65535.The Read Noise contributed by this entire subsystem is exceedingly small. So small in fact, that it is virtually undetectable, contributing less than 1/30 of the combined read noise of a typical image sensor. The low read noise and carefully chosen camera gain yield excellent Dynamic Range. Linearityis also outstanding, limited only by the CCD image sensor itself.
Small enough to practically hide behind a CD-ROM, the medium format QSI 600 Series family sets new standards for full-featured, high performance scientific CCD cameras. The striking appearance, refined design and superior fit and finish only hint at the advanced technical performance lurking inside. Some have described it as a work of art.
A defining feature of the 600 Series is the flexible design that permits three progressively configured body styles with a minimal impact on overall size. The relative sizes of the three body configurations, Slim, Medium, and Full, can be seen in the image to the right. A camera’s body size depends on the internal features installed. The Slim body is the thinnest version and can be used with CCDs incorporating an electronic shutter. The Medium body provides addition space for an internal mechanical shutter. The Full body allows the installation of both the shutter and a five position filter wheel with interchangeable filters.
Engineered with extensive use of sophisticated CAD-CAM design tools, the QSI 600 Series is CNC machined from aircraft grade aluminum alloy. The finely finished anodized body components are assembled with corrosion resistant stainless steel hardware throughout.
Small, Light-Weight and Thin
The 600 Series is designed to support image sensors with a maximum diagonal measurement of 22.5mm. For this class of camera they are surprisingly compact. At just 4.45″ square, the Slim body camera is just 1.68″ deep, occupying less than 30 cubic inches and weighing in at under 26 ounces. Even a Full body camera with shutter and color filter wheel is only 2.5″ deep and a mere 40 ounces. In fact, the small footprint is the practical limit for a camera with a 5 position filter wheel using standard 1.25″ threaded or 31mm unmounted filters.
Keeping the depth of the camera to a minimum was an early design goal. Not only is backfocus minimized, but the camera moment-arm is reduced resulting in greater stability. The shutter and filter wheel were placed inside the body, very close to the image sensor reducing backfocus and overall depth. The motion control electronics are actually buried in the 0.12″ thick shutter/filter mounting plate to reduce depth further. Pulling the cooling fans and heatsinks into the body resulted in another significant reduction in depth. Finally, having all electrical cables and the optional liquid heat exchanger recirculation hoses exit the body in the same direction and perpendicular to the optical axis insured an interference-free fit in tight spaces.
Efficient, Low Power CCD Sensor Cooling
Key in the compact design of the 600 Series cameras is a very efficient custom 2-stage thermoelectric cooler (TEC) subsystem. Intelligent, programmable cooling fans are integrated into the rear of the camera body to remove the heat generated by the cooler. Typically, forced air cooling lowers the regulated CCD temperature by up to 45°C below ambient utilizing 85% power. Tight +/- 0.1°C temperature regulation is maintained at temperature settings of 10°C below ambient and lower. A slim liquid heat exchanger (shown at right) can be attached to the rear of the camera body to increase the cooling further, up to 55°C below the temperature of the circulating fluid.
The cooled CCD image sensor is positioned in a hermetically sealed environmental chamber covered with an anti-reflection coated precision optical window. The chamber is purged with an ultra dry noble gas to increase heat conduction and eliminate the possibility of frost forming inside the chamber. To extend the useful period before re-purging is required, a user-rechargeable microsieve desiccant is employed to scavenge water molecules that enter the chamber. It is located behind a sub-micron, gas-permeable membrane to prevent particulate contamination of the CCD chamber.
Cooling and Dark Current
Effective cooling of the CCD image sensor is essential for long exposure imaging, especially in astronomy. Thermally generated electrons accumulate in the pixels over time and compete with the photo-electrons that make up the image. This accumulation of thermal electrons is known as ‘dark current’. It lowers the dynamic range of the sensor and reduces the signal to noise ratio. Eventually the thermally generated electrons will swamp the image.
Fortunately, dark current can be reduced dramatically by cooling the CCD. Sony ExView CCD sensors accumulate thermal electrons at a rate of roughly 4 electrons per second per pixel at 25°C. With every approximately 6°C decrease in temperature the dark current is reduced by half. Where a 10 minute exposure might generate 2400 thermal electrons at 25°C, it will produce only about 10 at -25°C. This is a very small number when compared to the CCD read noise and pixel full well capacity.
Two Shutters and a Filter Wheel
The QSI 640 utilizes the electronic shutter built into the KAI-04022 CCD image sensor to control exposures. Shutter timing is very precise and can range from as short as 100 microseconds up to 240 minutes. The very fast acting shutter is possible due to two key features of the interline transfer architecture.
Any existing electrons can be removed from the pixels instantly with a single electronic pulse, beginning the exposure.
After the specified exposure duration, the entire image field can be instantaneously moved into a light-shielded holding area on the CCD. The image is then read out at the normal rate without being contaminated by any light still illuminating the CCD surface.
The Model 640s model incorporates the optional internal, even-illumination mechanical shutter in the ‘mid-size’ camera body configuration. When operating with an interline transfer CCD, the mechanical shutter is not used to actually make the exposure. This is still the responsibility of the electronic shutter. The mechanical shutter is employed to cover the CCD and simplify the creation of Dark and Bias frames for subsequent image processing.
The Model 640ws adds an internal five position filter wheel to the camera in a ‘full-size’ camera body. The 640ws-8 incorporates a larger 8-position filter wheel. Even with the large 4mp sensor, the short backfocus and close spacing provided by the internal color filter wheel allows the 640ws or ws-8 to work even with optics faster than f/2.8 with no vignetting. The filter wheel accepts any standard threaded 1.25″ or unmounted 31mm filters.
The filter wheel can be easily removed and replaced to change or clean the glass filters. Additional filter wheels can be purchased allowing quick interchange of different filter set configurations.
Innovative Integrated Guider Port
Selecting the best guiding solution for deep sky imaging has always required a compromise. The available Integrated Guider Port (IGP) solves many of the problems associated with existing guiding solutions.
The Right Guiding Solution
Guiding with a separate guide scope provides the most flexibility, but differential flexure can be an issue, especially with long focal length scopes. With an internal guide chip, you’re forced to guide with light through your filters and you can’t guide at all while the shutter is closed or an image is being downloaded. This is especially problematic for narrowband imagers. To get around those issues, you could add an external off-axis guider, but a traditional OAG can add an inch or more of back focus plus more weight and two new mounting surfaces that need to be held rigidly.
Guide with Light From in Front of the Filter Wheel
The QSI 600 Series WSG models solves the problems with other guiding solutions by integrating a Precision Off-Axis Guider directly into the camera body with the pick-off prism positioned in front of the integrated color filter wheel – right where it belongs.
Never Struggle With Finding a Guide Star
One of the main challenges when using a camera with an internal guide chip is to find a star bright enough to guide by within the limited field of view of the internal guide sensor. When shooting through red, green or blue filters, ⅔ of the available light is blocked by the filter and not transmitted to the internal guider chip, guaranteeing lower signal-to-noise stars for guiding. This problem is compounded with narrowband filters where as little as 1% of the total light from a star reaches the guide chip. By positioning the pick-off prism in front of the filters, you always have all the star’s light available for guiding.
Integrated Guide Port Supports Fast Optical Systems
By integrating the Off-Axis Guider into the camera, we’re able to position the pick-off prism very close to the internal filter wheel adding minimal backfocus and eliminating any possibility of flexure or rotation compared to a traditional OAG. The large ½” square pick-off prism is optimally positioned close to the internal filter wheel, supporting the use of guide cameras with large sensors, while preventing any vignetting of the main sensor even with very fast optical systems.
Flexible Guide Camera Options
The Integrated Guide Port (IGP) built into 600 Series WSG models is designed to support any camera with 12.5mm of back focus or less that can be attached using C-mount or T-mount threads. Many cameras are designed with 12.5mm of back focus to be compatible with CS-mount lenses. CS-mount lenses use the same thread as C-mount (1″ x 32tpi) but with 12.5mm of back focus as opposed to 17.5mm for C-mount.
Easy, Rigid Guide Camera Focusing
The guide camera attaches to the WSG using a C-mount or T-mount threaded adapter (specified at time of order). The threaded adapter sits on top of the focus ring and allows the guide camera to be rotated to any position. The focus ring threads onto the focus base to allow 3mm of travel when focusing the guide camera. Once focus is achieved, the focus ring is locked with a set screw. The guide camera can still be rotated manually if desired without changing the focus. The end result is a rigid, easily focused guide camera that will not move or flex while your mount tracks the apparent motion of the night sky.
Connectivity and Notification
The connector panel, shown above, is thoughtfully recessed into the body of the camera for protection and provides access for all external connections. The two threaded holes on the back of the body are used to attach an optional cable restraint system to support the electrical connections as well as the recirculation hoses if the liquid heat exchanger is employed.
All QSI 600 Series cameras utilize High Speed USB 2.0 port (USB 1.1 compatible) for connection to the host computer and imaging application software. Read and transfer time for an entire 2048×2048 image frame is typically approximately one-half a second in High Speed mode and less than 7 seconds in High Quality mode. The frame rate can be further increased by reading just a portion of the image (ROI) or with flexible on-chip binning.
A four channel optically isolated control port is accessible through a standard 6 pin modular connector. The signal pin-out is compatible with most modern telescope mount drive correctors and is intended to be used for telescope guiding under MaxIm/DL and CCDSoft. The outputs can also be used for other control purposes when developing your own applications with the 600 Series ActiveX software development toolkit. The outputs are common emitter, open-collector and can sink up to 50ma. The maximum voltage should not exceed 50v.
One of the defining features of the 600 Series cameras is power efficiency. A fully configured 640ws camera operates from a single 12v DC supply and consumes less than 24 watts at full cooling, with both fans at maximum and the filter wheel moving. Other camera model configurations have power consumption as low as 5 watts. Included with each camera is an approved 12 volt DC power supply with an input voltage range of 90-240V, 50-60HZ.
Both visual and audible notification is built into all 600 Series cameras. A multi-color LED status display provides visual indication of the various states of camera operation. The behavior of the indicator is configurable and can be disabled by user command. A unique internal beeper provides audible feedback of camera operation and status. Like the visual display, the beeper can be configured and disabled by the user.
Extensive Software Support
Comprehensive Software Support
Every 600 Series camera is accompanied by a collection of software applications and tools that allow you to begin imaging immediately or develop custom camera control applications to precisely match your requirements.
MaxIm LE and MaxIm DL
MaxIm LE is based on the award winning MaxIm DL version 4.5 from Diffraction Limited providing the fastest and easiest way to image the night sky. All QSI 600 Series cameras are supported for imaging and auto-guiding, plus most popular guider cameras are supported as well.
Drivers for Software Bisque’s CCDSoft and TheSkyX
Realizing that one shoe doesn’t fit all, QSI also supplies the necessary drivers for CCDSoft, the popular Image Processing and Camera Control Software from Software Bisque, as well as their latest imaging application, TheSkyX.
Many other popular astronomical imaging packages are also support. See the QSI Software page for complete details.
Windows Custom Application Development
QSI provides an ASCOM-compatible API (Application Programming Interface) enabling customers to write their own custom camera control applications. The camera control API is an automation component that communicates with the camera device driver and exports a COM automation interface. COM automation provides an interface which Microsoft Office, VB, VBA, C++, and other Windows applications can use to control the camera. The API is available as part of the QSI Software Development Kit (SDK), available for download from the QSI website.
Using the Windows COM API with LabVIEW, MATLAB and other applications
The QSI camera control Windows API is an automation component that communicates with the camera device driver and exports a COM automation interface. The COM automation interface allows custom camera control applications to be developed for use with National Instruments LabVIEW, MathWorks MATLAB and any other application that adhere to the Windows COM interface. The API is distributed on the QSI Installation CD and is included with the QSI USB Drivers and Software installer above. The API Reference Manual can be downloaded from the Manuals & Downloads tab. QSI has sample VI’s for LabVIEW that can be used as a starting point to develop custom LabVIEW applications.
Linux Custom Application Development
QSI provides a camera control C++ API for Linux users on Intel x86-compatible platforms. The API provides full camera control and image capture capabilities via the USB interface. The API is implemented as a shared library providing an easy to use camera object that exposes all of the features and capabilities of the camera. It is well suited for both simple scripting, and more sophisticated imaging application development.
Field Upgradeable Firmware
All 600 Series cameras can be upgraded to the latest firmware in the field. The latest firmware is always available for download from the QSI Software page. QSI supplies a simple fail-safe Updater application that handles all the details.
No Mechanical Shutter
No Internal Filter Wheel
No Integrated Guider Port
5 Positions Internal Filter Wheel
No Integrated Guider Port
5 Positions Internal Filter Wheel
Integrated Guider Port
8 Positions Internal Filter Wheel
No Integrated Guider Port
8 Positions Internal Filter Wheel
Integrated Guider Port