Oriel InstaSpec X CCD
Key Features
  • Front illuminated, open electrode, and back illuminated CCDs
  • TE cooled at -75 °C
  • Resolve up to 9 tracks simultaneously (spectrograph dependent)
  • USB 2.0 interface and powerful software
Print View
Technical Question
Share This Page
Feedback
DescriptionSpecifications Models Catalog PDF
78235 InstaSpec X CCD coupled to MS260i Imaging Spectrograph

Three Models of InstaSpec X

We offer three models of InstaSpec X CCDs. All are completely integrated, TE cooled instruments with USB 2.0 interface. They use a 1024x256 pixel array; active area is 26.6 x 6.6 mm. Choose the model based on your spectral range of interest. Use Table 1 and the following discussion as a guide.

Table 1 InstaSpec X CCD Detection Systems
 Model  Type  Spectral Range  Advantages  Disadvantages
 78235  Front-Illuminated  400 – 1000 nm  Most economical option
for VIS-NIR spectral range		  Not usable in the UV
 78236  Front-Illuminated, Open Electrode  200 – 1000 nm  Advantages of a back illuminted CCD
without the etaloning problems;
relatively flat response		  QE not as high as
Back-Illuminated CCDs
 78237  Back-Illuminated  200 – 1000 nm  Highest QE in the UV;
best for low light level
measurements below 700 nm		  Etaloning effect at
wavelengths above 700 nm



Fig. 1 Structure of Front and Back-Illuminated CCDs.


Fig. 2 Quantum efficiences of InstaSpec X CCDs

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. This is the advantage of the Open Electrode CCDs. Open electrode CCDs are front-illuminated CCDs with a different architecture. In this design, some of the polysilicon gate structure is removed so that a portion of the pixel area is left uncovered. The result is a QE that is significantly better than that of conventional front-illuminated CCDs, but not as good as the QE of a back-illuminated CCD. Refer to Fig. 2 for the QE of all three CCD types.

If you are working with very low light levels, and need the QE that only a back-illuminated CCD can provide, there are ways to reduce the etaloning effects 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 front-illuminated CCDs, they do not suffer from etaloning effects. Therefore, the choice between front-illuminated, back-illuminated, and front-illuminated open electrode 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 have a high signal to noise ratio, but are working in the UV, choose a front-illuminated open electrode CCD.

3. If you are signal deprived and working at wavelengths under 700 nm, your best choice is a back-illuminated CCD.

4. If you need high sensitivity at wavelengths greater than 700 nm, you may still have the option of using a back-illuminated CCD if your experiment is tolerant of etaloning and/or you 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.

Building a Complete Benchtop Spectrometer

In order to ensure the greatest flexibility for Researchers, we’ve maintained a modular design. The spectrograph and CCD are separate components so you can choose the Spectrograph that best suits your needs. The spectrograph’s gratings and input slit assembly are interchangeable, so you can define your throughput and resolution. As your needs change, you can easily switch components in the field. To build a complete InstaSpec X Benchtop Spectrometer, you will need:
  • Oriel Spectrograph
  • Grating(s) and input slit
  • InstaSpec X CCD (InstaSpec Software is included)
  • Appropriate mounting flange for your spectrograph


Fig. 3 Top screen image shows a 5 track fiber bundle (100 µm cores) imaged through MS260i Spectrograph on an InstaSpec X CCD.

Multi-Track Imaging

These CCDs have a two dimensional sensor, unlike our LineSpec™ Linear CCDs. This allows the acquisition of multiple spectra simultaneously - known as Multi-track, or multi-stripe, Spectroscopy. With any InstaSpec X, an imaging spectrograph and a multi-track fiber optic, you can acquire up to nine spectra simultaneously. 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. See Oriel Multi-track Fiber Bundles for multi-track fibers.

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. See Oriel MS257™ 1/4 m Monochromator and Imaging Spectrograph to Oriel MS260i™ 1/4 m Imaging Spectrograph for spectrographs.

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. See Pencil Style Calibration Lamps for Spectral Calibration Lamps. 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. We list the flanges in the Ordering Information Table.