Optics: measuring and testing – By shade or color – Trichromatic examination
Patent
1994-12-23
1996-07-16
Gonzalez, Frank
Optics: measuring and testing
By shade or color
Trichromatic examination
356419, 356420, 356445, G01N 2125, G01N 2155
Patent
active
055372139
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to light measurement apparatus, in particular, though not exclusively, to colour and/or intensity measurement apparatus for use with for example a biomedical diagnostic test card.
BACKGROUND OF THE INVENTION
In recent years there have been developed test cards, e.g. solid phase immunoassay test cards, for biomedical diagnostic purposes. Such test cards are normally provided with one or more test sites, normally only a few millimeters (eg. about 5 millimeters) wide, to which a liquid sample (e.g. blood or serum) is applied. The test sites are designed to change colour in response to the presence and concentration of a particular component (e.g. a certain protein) in the liquid sample.
This colour change can, at least to a certain extent, be detected and measured by eye, by for example comparing a treated test site with a reference colour chart. Such visual techniques are, however, clearly unsatisfactory when it is desired to produce an accurate reliable measurement. To obtain reliably highly accurate measurements, an instrumental system is sought.
Measurement of colour, colour spectra and colour intensity of an opaque surface is performed by analyzing the light reflected from the surface when exposed to a defined light. It is essential that the surface area to be measured and the detection system are not exposed to external light during measurements, and light shielding of the mechanism is therefore provided. This is particularly critical if weak light sources such as light emitting diodes (LEDs) are used rather than strong sources such as xenon arc lamps or the like. It is also important that the light emitter and the light detector have defined positions relative to the surface to be measured.
Conventional instruments for analyzing surface colours tend to be large and heavy, thus not readily transportable, or smaller but still inflexible in use. Attempts to develop more versatile, small transportable systems have been made, but to date no known system meets all the requirements to overcome the problems of the prior art.
SUMMARY OF THE INVENTION
According to the present invention there is provided light measurement apparatus comprising an elongate member, said elongate member having at one end thereof light-emitting means and light-detecting means, at least the end of said elongate member provided with said light-emitting means and said light-detecting means being surrounded by a resiliently biassed sheath whereby in use when said elongate member is applied to a surface to take a reading said sheath defines a light-tight enclosure.
Preferably, the light-emitting and light-detecting means may comprise electronic components such as photodiodes, phototransistors or the like whereby the dimensions at the end of the member (i.e. the "tip") may be small so that the apparatus may be applied to a small surface area. The provision of a sheath to define a light-tight enclosure enables a low intensity light source to be used as the light-emitting means, e.g. a light-emitting diode (LED).
The light-emitting means may comprise means for emitting broad spectrum light or light of limited wavelength ranges. The use of two or more narrow band emitters will allow simple spectral analysis to be performed. Such a possibility is particularly advantageous when it is desired to measure concentration ratio(s) of two or more components on the test site which absorb light of different wavelength bands/regions. In this latter arrangement, two or more separate light sources may be provided, e.g. two or more LEDs, or alternatively switchable filter means may be provided to a single light source. Since absorption spectra from coloured surfaces always are of a broad-band nature, the signal-to-noise (S/N) ratio can be improved during measurements by using broad-band light emitters which coincide with the absorption range.
The sheath is preferably adapted to be slidable between the position in which it defines a light-tight enclosure, and a position in which the end of the elongate memb
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International Search Report for PCT/GB93/01357 (3pages).
Borch Stig M.
Seim Torstein
Eisenberg Jason D.
Gonzalez Frank
Nycomed Pharma AS
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