Silicon photodiode linear array

The classical silicon photodiode linear array manufactured by Reticon was the first detector marketed successfully. Similar solid state linear array detectors based on charge coupled devices, or charge.injection devices may also be of interest. Typical of the families of detectors, the Reticon detectors are built in a number of elements/array sizes. Commercially available units have anywhere from 128 to 1024 elements/array. Each individual element in the array is 1 x 1 mil to 1 x 100 mil in area, and are spaced on approximately 1 mil centers. The spectrometer system discussed in this article was built using Reticon-type devices. 

Photodiode arrays Basically, these arrays are made up of silicon photodiodes linearly set up within an integrated circuit. The numbers in each array are typically 512 or 1024. The photocurrent from each diode causes a capacitance build-up proportional to the incident light flux, which is read by sequentially discharging the array elements via an analog-to-digital converter for data processing. These arrays have a spectral response similar to that of the silicon photodiode, i.e., 180-1100 nm. A typical sensitivity plot is shown in Figure 8. 

The use of a linear detector array in the image plane of a polychromator in place of the fluorescence monochromator in Figure 12.1 enables the parallel data accumulation of complete fluorescence spectra. Silicon photodiode arrays, operated in a CCD mode(34) are the most widely used detector elements. The spectral response of the diodes enables fluorescence to be detected from the near-UV up to ca. 1100 nm with a peak response in the near-IR. Up to 8192 elements are now available commercially in a single linear array at low cost. However, the small length of each element (ca. 10 [im) presently limits sensitivity and hence cylindrical lens demagnification is often necessary. 

We have used a Reticon photodiode array and an Optical Multi-channel Analyzer to measure optical density changes Induced in photovisual materials using this technique. The Reticon is a device which incorporates a linear high density monolithic array of silicon photodiodes with integrated scanning circuits for serial readout. The array consists of 128... 

As an example, linear arrays of silicon photodiodes (photodiode arrays) are available as a package complete with the necessary circuitry to read out the array following exposure. Arrays are available with up to 2048 elements, and they are read out on an element by element basis. The scanning circuitry can access an element in 10 - 25 /rs, which suggests that the entire array can be read out in approximately 20 - 50 ms. Thus modulation frequencies can not exceed 50 Hz. However, as was discussed earlier, PEMs are driven at a resonant frequency which usually varies between 50 and 100 kHz, and this exceeds the readout rate of the photodiode array by three orders-of-magnitude. 

Photodiode arrays are one-dimensional detectors which consist of a linear array of photodiodes, produced in MOS technology on a single silicon chip [27, 28]. Arrays with up to 1024 diodes of 25.4 pm length and 2.5 mm width are presently available, leading to an active length of up to 25 mm. 

Antcliff, R. R., Hillard, M. E., and Jarrett, O. "Intensified Silicon Photodiode Array Detector Linearity Application to Coherent Anti-Stokes Raman Spectroscopy." Applied Optics 14 (1984) 2369. 

The photodiode array discussed in Section 7 - -.3. consists of a linear array of several hundred photodiodes (2.s6. 512. 1024, 2048) that have been fornieil along ihe length of a silicon chip, l ypically. the chips are 1 lo 6 cm long, and (he widths of (he individual diodes arc l5to.5() pm (see Figure 13-1.5). linear (TD... 

The linear photodiode array (LPDA) is a transducer developed to enable simultaneous measurement of light intensity at many wavelengths. The diode array consists of a number of semiconductors embedded in a single crystal in a one-dimensional linear array. A common procedure is to use a single crystal of doped silicon that is an n-type semiconductor. A small excess of a group 3A element, such as arsenic, is embedded into the surface at regular intervals. This creates local p-type semiconductors. The semiconductor device ideally has a cross-section such as that shown in Fig. 5.24. The surface contains a linear series or array of pn junctions, each of which is a photodiode. The individual diodes are called elements, channels, or pixels. 

Linear phosphonitrilic chlorides (LPNCs), silicone fluids and, 22 573 Linear photodiode arrays, 19 153 Linear polyesters, 14 116 Linear polyethylene fibers, 20 398 Linear polyimides, synthesis of, 20 273 Linear polymers, 20 391 25 455 high molecular weight, 23 733 zero-shear viscosity of, 19 839 Linear poly(thioarylene)s, 23 705 Linear PPS, 23 704. See also... 

Diode array detector A silicon chip that accommodates numerous photodiodes provides the capability to collect data from entire spectral regions simultaneously. Usually contains 64 to 4096 photodiodes arranged linearly. 

Silicon charge coupled devices (CCDs), commonly used in solid-state video cameras and in research applications, are being applied to low light level spectroscopy applications. The main advantage of area array CCDs over linear photodiode detectors is the two-dimensional format, which provides simultaneous measurements of spatial and spectral data. 

Milano et al. [153, 154] and Cook [34] introduced an approach to derivative spectra by substituting electronic wavelength modulation for the mechanical systems used in derivative spectrometers. This effect is achieved by superimposing a low-amplitude, periodic wave form on the horizontal sweep signal. In this way spectra were generated. Warner et al. [155] applied a vidicon detector for fast detection of fluorescence spectra and obtained derivatives of the stored data by digital computation. Cook et al. [156] also made use of a silicon vidicon detector for multichannel operations in rapid UV-VIS spectrophotometers with the possibility of first-order differentiation. For the same purpose Milano et al. [93, 157] used a multichannel linear photodiode array for detection of spectra in polychromator optics and stored data manipulations (d ). Technical explanations of the principles of diode array and vidicon devices cem be found in [158-161]. 

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