| |
Sensitivity
The sensitivity of a detector pixel at a certain wavelength is defined as the detector electrical output per unit of radiation energy (photons) incident to that pixel. With a given A/D converter this can be expressed as the number of counts per mJ of incident radiation.
The relation between light energy entering the optical bench and the amount hitting a single detector pixel depends on the optical bench configuration. The efficiency curve of the grating used, the size of the input fiber or slit, the mirror performance and the use of a Detector Collection Lens are the main parameters. With a given set-up it is possible to do measurements over about 6-7 decades of irradiance levels. Some standard detector specifications can be found in Table 4 detector specifications. Optionally a DCL cylindrical detector collection lens can be mounted directly on the detector array. The quartz lens (DCL-UV for AvaSpec-2048/3648) will increase the system sensitivity by a factor of 3-5, depending on the fiber diameter used.
In Table 4 the overall sensitivity is given for the detector types currently used in the UV/VIS AvaSpec spectrometers as output in counts per ms integration time for a 16-bit AD converter. To compare the different detector arrays we have assumed an optical bench with 600 lines/mm grating and no DCL. The entrance of the bench is an 8 µm core diameter fiber, connected to a standard AvaLight-HAL halogen light source. This is equivalent to ca. 1µWatt light energy input.
Table 4 Detector Specifications (based on a 16-bit AD converter
|
Detector
|
TAOS 128
|
HAM256
|
HAM1024
|
SONY2048
|
TOSHIBA3648
|
HAM2048x14
|
|
Type
|
Photo diode array
|
CMOS linear array
|
CMOS linear array
|
CCD linear array
|
CCD linear array
|
Back-thinned CCD array
|
|
# Pixels, pitch
|
128, 63.5µm
|
256, 25 µm
|
1024, 25 µm
|
2048, 14 µm
|
3648, 8 µm
|
2048x14, 14µm
|
|
pixel width x height (µm)
|
55.5 x 63.5
|
25 x 500
|
25 x 500
|
14 x 56
|
8 x 200
|
14x14 (total height 196µm)
|
|
Pixel well depth (electrons)
|
250,000
|
4,000,000
|
4,000,000
|
40,000
|
120,000
|
250,000
|
|
Sensitivity (V/lx.s)
Photons/count @600nm
|
100
|
22
|
22
|
240
|
160
|
200
|
|
100
|
440
|
440
|
40
|
60
|
50
|
|
Sensitivity
(AvaLight-HAL, 8 µm fiber) in counts/µW per ms integration time
|
4000 (AvaSpec-128)
|
120 (AvaSpec-256)
|
120 (AvaSpec-1024)
|
20,000 (AvaSpec-2048)
|
14,000
(AvaSpec-3648)
|
16,000 (AvaSpec-2048x14)
|
|
Peak wavelength
|
750 nm
|
500 nm
|
500 nm
|
500 nm
|
550 nm
|
650 nm
|
|
Signal/Noise
|
500:1
|
2000:1
|
2000:1
|
200:1
|
350:1
|
500:1
|
|
Dark noise (counts RMS)
|
60
|
28
|
60
|
35
|
35
|
50
|
|
Dynamic Range
|
1000
|
2500
|
2500
|
2000
|
2000
|
1300
|
|
PRNU**
|
± 4%
|
± 3%
|
±3%
|
± 5%
|
± 5%
|
±3%
|
|
Wavelength range (nm)
|
360-1100
|
200-1000
|
200-1000
|
200*-1100
|
200*-1100nm
|
200-1160
|
|
Frequency
|
2 MHz
|
500 kHz
|
500 kHz
|
2 MHz
|
1 MHz
|
1.5 MHz
|
* DUV coated
** Photo Response Non-Uniformity = max difference between output of pixels when uniformly illuminated, divided by average signal
In table 5 the specification is given for the NIR spectrometers, in figure 5 and figure 6 the spectral response curve for the different detector types are depicted.
Table 5 NIR Detector Specifications
|
Detector
|
NIR256-1.7
|
NIR256-2.2
|
NIR256-2.5
|
|
Type
|
Linear InGaAs array
|
Linear InGaAs array with 2 stage TE cooling
|
Linear InGaAs array with 2 stage TE cooling
|
|
# Pixels, pitch
|
256, 50 µm
|
256, 50 µm
|
256, 50 µm
|
|
pixel width x height (µm)
|
50 x 500
|
50 x 500
|
50 x 500
|
|
Pixel well depth (electrons)
|
16,000,000
|
1,500,000
|
1,500,000
|
|
Sensitivity
(AvaLight-HAL, 8 µm fiber) in counts/µW per ms integration time
|
350
|
250
|
200
|
|
Peak wavelength
|
1550 nm
|
2000 nm
|
2300 nm
|
|
Signal/Noise
|
4000:1
|
1200:1
|
1200:1
|
|
Dark noise (counts RMS)
|
12
|
40
|
40
|
|
Dynamic Range
|
5000
|
1600
|
1600
|
|
PRNU**
|
± 5%
|
± 5%
|
±5%
|
|
Defective pixels (max)
|
0
|
12
|
12
|
|
Wavelength range (nm)
|
900-1750
|
1000-2200
|
1000-2500
|
|
Frequency
|
500 kHz
|
500 kHz
|
500 kHz
|
** Photo Response Non-Uniformity = max difference between output of pixels when uniformly illuminated, divided by average signal
|
CORPORATE