Optics: measuring and testing – By dispersed light spectroscopy – With sample excitation
Reexamination Certificate
2001-07-02
2003-12-02
Nguyen, Thong (Department: 2872)
Optics: measuring and testing
By dispersed light spectroscopy
With sample excitation
C356S318000, C250S458100
Reexamination Certificate
active
06657720
ABSTRACT:
TECHNICAL FIELD
This invention relates to spectrometry instrumentation in general and in particular examples to fluorescence, phosphorescence and luminescence spectrophotometry.
BACKGROUND
A fluorescence spectrophotometer usually comprises a flash light source, an excitation monochromator or filter, a sample cell containing a sample to be analysed, an emission monochromator or filter, a photodetector and signal processing electronics. A specific wavelength of light from the flash source, as selected by the excitation monochromator or filter, is directed into the sample cell and resultant fluorescence light from the sample enters the emission monochromator or filter. A specific wavelength of the fluorescence light, as selected by the emission monochromatolr or filter, is directed onto the photodetector to produce an electrical signal corresponding to the intensity of the fluorescent light. Such an instrument may be arranged to make a fluorescence, phosphorescence or luminescence measurement. Fluorescence measurements relate to light which is emitted virtually immediately by a sample upon its exposure to the excitation light, whereas phosphorescence measurements relate to the light emitted from the sample a short characteristic time after its exposure to the excitation light. Luminescence measurements are taken by measuring the emitted light from a sample without exposing the sample to excitation light. Such measurements are used to characterise substances, with fluorescence measurements in particular having wide application in the biotechnical field for characterising DNA and other proteins, for example using fluorofors.
It is known in spectrometry instruments in general, and in spectrophotometers for fluorescence, phosphorescence and luminescence measurements, to provide exchangeable accessories. Generally these may provide different sample presentation facilities, for example a liquid sample presentation accessory may be exchanged for one which provides for presentation of a solid state sample. Different accessories may also provide for temperature control of samples via Peltier, Dewar or other cryostat devices, successive feeding of multiple samples to a reading location, or multiple sample carriers such as a well plate and reader therefor.
In order not to compromise test results, it is important that the exchangeable accessories for a spectrometer be repeatably and accurately locatable on the instrument. Prior art arrangements for doing this, which involve screw threaded attachment of one part to another, generally do not facilitate rapid exchange of one accessory for another.
As described above, the capability to make phosphorescence measurements (that is, phosphorescence emission intensity versus time) is included in some fluorescence spectrophotometers. To collect phosphorescence intensity versus time data that results from a short pulse of excitation light, it is necessary to repetitively measure the emission intensity at a time short enough to adequately define the relationship. The capturing of a data point can be done relatively quickly via a sample and hold circuit, however the measurement and digitisation of that data point typically takes a reasonable length of time. Such data conversion often takes longer than the required interval between successive measured points. By way of example, adequate definition of the emission time relationship may require measurement of the emission intensity at 1 microsecond intervals yet the digitisation of a single emission datum may take, say, 19.5 microseconds. For this reason, the prior art technique is to use a sampling approach. In this arrangement, the excitation light pulse is generated repetitively at a constant interval. The interval must be long enough for the emission from one pulse to have fallen substantially to zero before the next pulse is applied. After each excitation pulse a single emission intensity is measured at a controlled time after the excitation pulse so as to give a single datum of the emission time relationship. For each successive cycle the time interval between the excitation and capturing of emission intensity is modified so as to build up a complete picture of the overall emission versus time relationship. In the example given. for the first cycle the time delay could be 1 microsecond. For the second cycle the time delay may be 2 microseconds. For the third the delay will be 3 microseconds and so on.
The problem with this approach is that the interval between excitation pulses must be long enough to allow the emission to die away substantially to zero between one pulse and the next. At the same time many cycles are needed to build up a comprehensive picture of the emission versus time relationship. The overall measurement is thus slow. For example, again referring to the above example of one microsecond intervals between data points, if data covering two milliseconds is desired then 2000 data points will need to be collected. If the time for the emission to substantially fall to zero is 10 milliseconds, it will take 20 seconds to complete the 2000 measurement cycles.
SUMMARY OF THE INVENTION
According to a first aspect the presen
1
t invention provides a spectrometry instrument and an exchangeable accessory therefor including a manually operable mechanism for attaching the exchangeable accessory to the instrument, the mechanism including a manually rotatable camming means associated with one of the accessory or the instrument, a male member associated with the other of the accessory or the instrument, the male member having a camming surface which is engageable by the camming means, wherein the accessory is positionable on the instrument in a predetermined location and the camming means is manually rotatable to engage the camming surface of the male member and thereby lock the accessory on the instrument in the predetermined location.
In spectrometry instruments which have exchangeable accessories, it would be advantageous if the instrument could detect if an accessory has been attached and if so, to identify what accessory it is. The advantages of this include the instrument's set up and programming for use with a particular accessory being able to be automatically established. Also for those accessories that include electrical componentry, such as stepper motors, it would be advantageous to detect the presence of such a component.
According to a second aspect the present invention provides a spectrometry instrument including an electrical circuit for identifying anyone of a plurality of exchangeable accessories which are connectable to the instrument, the electrical circuit including a voltage source and means for generating an identifying voltage therefrom, wherein each accessory includes at least one circuit element such that connection of an accessory to the instrument alters the identifying voltage to a value which is uniquely dependent upon the accessory which is connected to the instrument.
The accessory recognition circuitry may be such that it recognises the presence of an electric motor of an accessory. In this case a voltage divider can be arranged to provide a logic high signal in the presence of a motor by virtue of the motor winding completing a circuit between the voltage source and the voltage divider. In the absence of the motor, the circuit is open and a logic low signal is derived from the voltage divider.
Preferably the spectrometer includes circuitry for identifying an accessory and further circuitry for determining the presence or absence of an electric motor in that accessory.
For a spectrometer with a capacity to have a number of different accessories connected thereto at the same time, each connection socket for each accessory may include accessory recognition circuitry as above described. In this arrangement, the signal line for the identifying voltage from each circuit may be connected to a multiplexer for input to a microprocessor of a computer.
In a third aspect the present invention provides a method and apparatus for reducing the time for measuring a number of da
Berkowitz Edward H
Nguyen Thong
Varian Australian PTY LTD
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