InstaSpec VII and VIII CCD Array Detectors |
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We have been offering InstaSpec™ Multichannel Detection Systems for 10+ years. Our first InstaSpec™ detectors were 512 and 1024 photodiode arrays. We then added CCDs and InGaAs arrays, and continually improved the performance and simplified the operation. Here, we present our newest addition to the InstaSpec™ family - InstaSpec™ VII and InstaSpec™ VIII. These are thermoelectrically cooled spectroscopic CCD systems with 1024 x 252 or 1024 x 124 arrays. They have a USB 2.0 PC interface and include a completely new version of the InstaSpec™ Spectroscopy Software, for true plug-and-play operation. |
InstaSpec™ VII vs InstaSpec™ VIII |
The difference between these two InstaSpec™ families is the array height. InstaSpec™ VII detectors use a 1024 x 124 (or 122) image array with an active area of 25 x 3 mm. These detectors are suitable for single and dual track spectroscopy. The larger arrays of the InstaSpec™ VIII models (when mated with appropriate Oriel Spectrograph) let you resolve up to 9 tracks. These detectors use a 1024 x 252 (or 250) image array with an active area of 25 x 6 mm.
We offer front and back illuminated versions of both InstaSpec™ Detectors. |
Fig. 1 Structure of Front and Back-Illuminated CCDs.
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Back-Illuminated vs Front-Illuminated |
Back-illuminated CCDs (also called back-thinned CCDs) are solid-state imaging devices that have been etched to 15-30 µm thickness in order to collect light through the rear surface. As a result of this modification, no light is lost through absorption and reflection by the polysilicon gate structure providing more than twice the quantum efficiency (light detection ability) of these CCDs compared to their front illuminated counterparts (Fig. 2).
An unfortunate side effect of this process is that the devices become semi-transparent in the near infrared (NIR). The parallel front and back surfaces of these CCDs cause them to act as etalons. This etalon-like behavior leads to unwanted fringes of constructive and destructive interference, which artificially modulate a spectrum. This modulation can be significant and troublesome for almost all NIR spectroscopy. There are ways to reduce this effect through software (such as flat-field correction), but sensitivity and resolution may be adversely impacted. Etaloning becomes apparent at wavelengths over 700 nm and can be very pronounced at wavelengths over 800 nm. Because light detection occurs on the first surface, with frontilluminated CCDs, they do not suffer from etaloning effects. Therefore, the choice between front and back-illuminated CCDs can be summarized as follows:
1. If you have a high signal to noise ratio and work primarily at wavelengths between 600 and 1000 nm, a front-illuminated CCD is your best choice.
2. If you are signal deprived and working at wavelengths under 700 nm, you best choice is a back-illuminated CCD.
3. If you need high sensitivity at wavelengths greater than 700 nm, you may still have the option of using a backilluminated CCD if your experiment is tolerant of etaloning and/or are able to correct for it in software (flat-field correction). This is dependant on your experiment and the results you are trying to achieve. |
What Makes up a InstaSpec™ VII or VIII Detector? |
Each system comes with a CCD detector head, a TE cooler controller and the powerful InstaSpec™ Spectroscopy software. |
Detector Head |
These CCD heads are TE cooled to -35 °C. The sensor area is large and there are no dead regions between elements. The back illuminated models have very good responsivity down to 200 nm (see Fig. 2 for Quantum Efficiency curves).
These detectors have an external trigger for single shot operation and synchronization to pulsed sources. |
TE Controllers |
These systems have a stand alone controller which also houses the USB 2.0 interface. A 15 ft (5 m ) long cable connects the detector head to the controller, and a 15 ft (5 m) long USB cable connects the controller to your PC. |
Powerful Spectroscopy Software |
This is an all new instrument control, data acquisition and analysis software. This Windows™ XP based system commands the spectrograph, shutter and detector; acquires and displays the data in real time; and allows analysis and manipulation of your data. Below are only some of the functions you can perform with the InstaSpec™ software:
•Continuous, single and averaging scans
•Irradiance measurements
•Background correction
•Area under the curve analysis
•SPE to ASCII file conversion
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Multi-track and Imaging |
These CCDs have a two dimensional sensor, unlike the linear CCDs described on the previous pages. This allows the acquisition of multiple spectra simultaneously - known as Multi-track, or multi-stripe, Spectroscopy. With InstaSpec™ VIII, an imaging spectrograph and a multi-track fiber optic, you can acquire up to nine spectra simultaneously. The height of the InstaSpec™ VII array limits the number of spectra which can be simultaneously acquired, to two.
The number of channels that can be resolved simultaneously depends upon the height of the array, the resolution of the imaging spectrograph and the individual track sizes and spacings of the multi-track fiber. |
Shutters |
For Multi-track Spectroscopy or imaging applications with CW sources, you will need a shutter. Our MS260i™ 1/4 m and our MS127i™ 1/8 m imaging instruments come standard with a shutter. The MS257™ has optional shutters. These shutters can be controlled from the InstaSpec™ software. |
Spectral Calibration Lamps Ensure Wavelength Accuracy |
For the highest wavelength accuracy, we recommend using a known set of spectra lines and letting the InstaSpec™ software fit a standard quadratic regression through the known peaks. We offer a variety of Spectral Calibration Lamps for your wavelength calibration needs. We offer a mount, model 78117, to hold two spectral line lamps at the input of our spectrographs, simultaneously. This allows calibration at multiple lines. |
Mounting |
A flange is required to mount these InstaSpec™ detector heads to the output of Oriel Spectrographs, at the proper focal distance. |
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Related Products |
MS260i™ m Spectrograph- MS127i™ m Spectrograph
- MS257™ m Spectrograph
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Fig. 2 Quantum Efficiency of Front and Back Illuminated CCDs.
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Fig. 3 Top screen image shows a 5 track fiber bundle (100µm cores) imaged through the Oriel MS260iTM Spectrograph on an InstaSpecTM VIII CCD.
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