Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Reexamination Certificate
1998-08-25
2001-05-08
Evans, F. L. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
C356S328000
Reexamination Certificate
active
06229604
ABSTRACT:
TECHNICAL FIELD
The present invention refers to a photoelectric detector device to be used in atomic absorption spectroscopy.
BACKGROUND ART
Photoelectric detector devices of that kind, are known in the field of the atomic absorption spectroscopy, for instance in the form of photo semiconductor devices.
The photo semiconductor devices in a detector device of that kind may exist in the form of photo diodes, CCD structures etc.
However, the signal
oise ratio of known detector devices of that kind depends on the portion of the detector face that is actually loaded by a radiation to be detected. An aggravated signal
oise ratio in particular results if not the entire detector face but only a small part thereof is loaded by the radiation to be detected.
SUMMARY OF THE INVENTION
Thus, the object underlying the invention is to improve the known photoelectric detector device.
This object is achieved by a detector device which is characterized by a photo semiconductor array having a plurality of photo semiconductor devices and a read-out means for jointly reading out the charges generated by impingement of radiation onto the photo semiconductor device of any continuous portion within the photo semiconductor array, and for generating electric signals corresponding to the read-out charges.
By means of a detector device designed in that manner, only the charges generated by impingement of radiation in any continuous portion of the photo semiconductor array can be read out by means of the read-out means. Through this it is possible to only read out charges from that part of the photodetector onto which the radiation to be detected or measured actually impinges. Those portions which in the known detectors make a great contribution to the signal
oise ratio, i.e. those portions that do not deliver a measuring signal but merely lead to a read-out noise are therefore not taken into consideration by the read-out device.
In accordance with an advantageous development, the detector device comprises a plurality of inputs each being assigned to a photo semiconductor device of the photo semiconductor array, an output for the generated electric signals which correspond to the read-out charges, a switching means having at least one switch associated to at least one input, each switch being provided downstream each input associated thereto, and by means of each switch each input associated thereto can be coupled to the output of the read-out device.
By means of this embodiment, which merely comprises simple electronic components, the invention can be realized in an especially reasonable manner.
In accordance with a further embodiment, a switch may be assigned to a plurality of inputs. Since this embodiment requires less components, it is in particular advantageous if the photo semiconductor array is designed symmetrically with respect to an axis, and the face of the detector device shall be enlarged or reduced only symmetrical with respect to this axis.
Each switch of the switching means may preferably be electrically operable. In this case each switch can be controlled quickly and reliably by electric signals supplied to the read-out device.
In an advantageous embodiment a device may additionally be provided to each switch, said device putting all photo semiconductor devices which are not coupled to the output of the read-out device to a predetermined potential. Thus, possible influences of photo semiconductor devices on the circuit, from which charges are not to be read out, are minimized.
For this purpose each device associated to a switch may for instance have a further switch, which is provided between the input associated to the switch and the predetermined potential such that it couples the input—when it is not coupled to the output of the read-out device—to the predetermined potential. Furthermore, the switch and the switch associated thereto may be provided in an operative manner by an electric signal which is supplied to the switch directly and to the associated switch via an inverter.
Moreover, a decoding means can be provided, which in response to digital selection signals operates the switch(es). Thereby it is possible to easily control a plurality of switches electronically, i.e. by means of a processor means.
According to a further advantageous embodiment, a power limiting means, e.g. in the form of a diode, can be provided directly after each input in the read-out device. Such a power limiting means ensures that the read-out device responds not until reaching a predetermined threshold value.
According to an advantageous embodiment, the detector device comprises an amplifier device having an operational amplifier for amplifying the electric signals of the read-out device and a variable capacitance connected in parallel to the amplifier.
Thereby the sensitivity range of the detector can be adjusted in a simple manner by varying the capacitance. By selecting the sensitivity range in response to the signal to be measured, the signal
oise ratio can moreover be optimized.
Such a variable capacitance can in an especially reasonable manner be composed of arrays connected in parallel each consisting of a capacitor and a switch, the capacitance being variable by operating at least one switch.
Furthermore, an additional switch may be provided in parallel to the arrays each consisting of a capacitor and a switch. This measure causes the integrator circuit consisting of the operational amplifier and the variable capacity to be set back in an especially simple and quick manner.
In accordance with a further purposeful embodiment, a decoder means may be used for operating the switches of the variable capacitance, said decoder means operating the switches in response to digital selection signals. Through this an especially simple change of the capacitance in a means having a plurality of parallel connected arrays of capacitors and switches is possible by means of few selection signals.
Further advantages of the invention can be derived from the following exemplary description of preferred embodiments of the invention with reference to the drawings.
REFERENCES:
patent: 4958928 (1990-09-01), Kuderer
patent: WO 91/03714 (1991-03-01), None
Radziuk Bernhard
Rodel Gunter
Bodenseewerk Perkin-Elmer GmbH
Evans F. L.
St. Onge Steward Johnston & Reens LLC
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