LineSpec™ CMOS and CCD Array Spectrometers

  • Complete packages – Oriel MS125TM Spectrograph and linear array detector
  • 1024 CMOS and 2048 CCD linear arrays
  • True plug and play systems with USB interface

Overview

For applications not requiring the two dimensional area of our InstaSpec™ CCD systems, but needing the versatility and superior resolution not afforded by our integrated minispectrometers, LineSpecTM Spectrometers are a smart alternative. Gratings and slits are interchangeable so you can re-define the usable spectral range and resolution, as your needs change.
LineSpecTM Spectrometers are made up of our MS125™ 1/8 m Spectrograph and an external 2048 CCD or 1024 CMOS array. We also offer the array detectors separately, for mounting to other Oriel Spectrographs.

What Makes up a LineSpec™ Spectrometer?

We offer two models of LineSpec™ Linear Arrays, a 2048 pixel CCD detector and 1024 pixel CMOS detector. Both systems include everything you need to begin work:

  • MS125™ Spectrograph
  • Your choice of grating
  • Your choice of entrance slit with input slit holder
  • 2048 CCD or 1024 CMOS detector with mounting flange
  • LineSpec™ Software

MS125™ Spectrograph

We chose the MS125 as the spectrograph for these systems, because of its high resolution and throughput, economical price, and compact size. The MS125 is a micrometer driven, 1/8 m (120 mm), focal length instrument.

Table 1 Grating Options for LineSpec Linear Array Spectrometers

Grating Model Line Density (I/mm) Blaze Wavelength Type Spectral Resolution (nm)* Array Bandpass
(nm)
Primary Wavelength Region
(nm)**
77419 2400 250 Gratings 0.11 nm 84 200 – 500
77411 1200 350 Gratings 0.22 nm 170 200 – 1000
77464 1200 500 Gratings 0.22 nm 170 280 – 1600
77412 1200 750 Ruled Gratings 0.22 nm 163 450 – 1000
77414 600 400 Gratings 0.43 nm 338 250 – 1300
77415 600 750 Gratings 0.43 nm 338 450 – 2000
77416 400 350 Gratings 0.65 nm 503 200 – 800
77417 400 500 Gratings 0.65 nm 505 300 – 1200
Fig. 1 Quantum efficiency of CCD and CMOS Detectors.

Fig. 1 Quantum efficiency of CCD and CMOS Detectors.

CMOS vs CCD Detectors

A key performance parameter determining the choice of CMOS or CCD is the maximum S/N achievable by the detector. Maximum S/N is achieved when the detector is close to saturation and the shot noise is much higher than all the other noises. For example, if one has a signal strong enough to saturate the well in the shortest exposure time, then the dark signal noise contribution is negligible, and as the readout noise adds orthogonally to the shot noise, it too has negligible contribution. To make a high resolution measurement of a signal level, a better S/N than the expected resolution of the measurement, is required. Consider trying to measure a 0.3% change in the intensity of a spectral line. Ideally, the S/N should be at least 5X better than the difference being measured and therefore a S/N of 0.3%/5 = 0.06%, or 0.06 in 100, which is 1667:1, is desired. One can only achieve this S/N level with a detector with a well capacity >1667 squared, i.e. >2,780,000 e. No CCD can achieve this S/N ratio in a single measurement, but a CMOS can. It should be noted, however, that a CMOS detector is less sensitive than a CCD so stronger signals are required with a CMOS than with a CCD.

The key differences between the CCD and CMOS detectors are sensitivity and dynamic range. Because the CCD pixels are 2.9X larger than the CMOS pixels, the CCD sees 2.9X more light. The CCD’s much larger gain makes it 23.4X more sensitive. Overall, the CCD is 2.9 x 23.4 = 67.9X more sensitive than the CMOS detector. The CMOS detectors have a well capacity that is 24-30X greater than the linear CCDs, and so the signal to noise ratio of a CMOS detector ~4X greater than for CCD detectors.

In short, CMOS detectors have application for high signal, high dynamic range and high S/N measurements, whereas CCD detectors are for low signal measurements.

LineSpec Data Acquisition and Control Software

The LineSpec software (included with each spectrometer or stand alone array detector) is an intuitive instrument control and data acquisition software that runs under Windows 98/W2K/XP. The software supports routine spectroscopic measurements and data acquisition, such as: continuous, single and averaging scans; absorption, transmission and emission spectra; irradiance measurements. We also supply optional LabView Drivers and an OEM Development Kit.

Calibration Accessory

To ensure wavelength accuracy, we recommend using a known set of spectral lines, such as our 78822 HgAr Calibration Set, and letting the LineSpec™ software fit a standard quadratic regression through the known peaks. The 78822 includes a power supply, a mounting adapter to couple the lamp to the MS125™, and a HgAr calibration lamp.

Fig. 2 Transmittance spectra of BG36 Schott Glass Filter taken with 78871 CMOS Spectrometer. The MS125™ Spectrograph used a 400 l/mm grating blazed at 500 nm, and a 50 µm input slit. Integration time = 50 ms, averaging = 1 and 500 (noted on the inset graph).

Fig. 2 Transmittance spectra of BG36 Schott Glass Filter taken with 78871 CMOS Spectrometer. The MS125™ Spectrograph used a 400 l/mm grating blazed at 500 nm, and a 50 µm input slit. Integration time = 50 ms, averaging = 1 and 500 (noted on the inset graph).

Specification

For detailed performance Specifications please refer to www.Newport.com

CCD Detector (78854) CMOS Detector (78866)
Spectral Response 200 – 1100 nm 250 – 1100 nm (Usable); 330 – 1100 nm (Primary)
Number of Active Pixels 2048 1024
Pixel Size 200 µm (H) x 14 µm (W), on 14 µm centers 125 µm (H) x 7.8 µm (W), on 7.8 µm centers
Array Quality no bad pixels, no fringing no bad pixels, no fringing
Array Length 29 mm 8 mm
Well Capacity 140,000 electrons 3,260,000 electrons
Dark Signal 680 e/s (@ 25°C, subtractable) 3000 e/s (@ 25°C, subtractable)
Dark Noise 26 e/s (@ 25°C) 55 e/s (@ 25°C)
Saturation Exposure (633 nm) 3 nJ cm-2 (total); 8.4 x 10-14 J (per pixel) 195 nJ cm-2 (total); 1.9 x 10-12 J (per pixel)
Readout Noise (in counts, RMS) 4 1.3
Readout Noise (in electrons, RMS) 122 1022
Gain (e/ADC count) 34 796
Maximum S/N 374:1 (single exposure) 1800:1
Dynamic Range (Well Capacity/Readout Noise) 1150 3190
Integration Time 8 ms – 10 s 1 ms – 10 s
Synchronization Modes continuous scan, self trigger and external trigger continuous scan, self trigger and external trigger
External Trigger Jitter 300 ns 300 ns
A/D Converter 12 bit 12 bit
Computer Interface USB 1.1, 2 USB 1.1, 2
Software Environments Windows 98/W2K/XP Windows 98/W2K/XP
RAM Requirements 64 MB 64 MB

 

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