Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Reexamination Certificate
1998-04-20
2001-01-30
Font, Frank G. (Department: 2877)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
C356S319000, C356S320000, C356S367000
Reexamination Certificate
active
06181417
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a readhead for a photometric diagnostic instrument, such as a reflectance spectrometer, for performing tests on a sample of body fluid to be analyzed.
It is useful for various medical diagnostic purposes to utilize a reflectance spectrometer to analyze samples of body fluid, for example, to detect the blood glucose level of infants. Conventional reflectance spectrometers have been used to detect the presence of glucose in a blood sample disposed on a reagent pad. Glucose present in the blood reacts with the reagent on the reagent pad, causing the reagent pad to change color to an extent which depends on the glucose concentration in the blood.
A readhead for use in a spectrometer device is disclosed in U.S. Pat. Nos. 5,518,689 and 5,611,999 to Andrew Dosmann, et al. That readhead is composed of a housing, a pair of light-emitting diodes fixed relative to the housing and adapted to emit light towards a target area in which a reagent pad is located, and a sensor for detecting light emitted from the illuminated reagent pad.
The accuracy of reagent tests of the type described above is dependent on the sensitivity of the reflectance spectrometer to non-uniform color distributions in the reagent pad. It is desirable that the spectrometer is relatively insensitive to such non-uniform color distributions. It has been realized that two important optical characteristics that minimize inaccuracies caused by non-uniform color development are the size of the reagent area that is read by the instrument and the uniformity of the illumination of the reagent pad.
Some prior art techniques used to attempt to improve the quality of an illumination system include the use of ground glass or frosted Mylar plastic in front of the light source. However, those techniques were tested and found to be unacceptable due to excessive expansion of the light beam, relatively large light output loss, and increased stray light.
OBJECT
It is an object of the invention to overcome the disadvantages of the prior art. This object is solved by a combination of features of the main claim. The subclaims disclose further advantageous embodiments of the invention.
SUMMARY OF THE INVENTION
The summary of the invention does not necessarily describe all necessary features of the invention and the invention may also reside in a sub-combination of described features. The “Summary of the Invention,” thus incorporated, presents, therefore, only an example, but not a limitation of the subject matter.
The invention can be summarized as a readhead for a spectrometer for illuminating a target area and receiving light from the target area. The readhead is provided with a housing adapted to be incorporated in a spectrometer, a light source mounted in a fixed position relative to the housing, a support mechanism adapted to support a biological sample to be illuminated by the light source, light-shaping means disposed between the light source and the support for increasing the diameter, intensity and uniformity of the light beam, and a photodetector mounted in fixed position relative to the housing, the photodetector being adapted to detect light from the biological sample illuminated by the light source.
The light source may be in the form of a light-emitting diode that emits substantially monochromatic light having a first wavelength, and the readhead may also include a second light-emitting diode mounted in a fixed position relative to the housing, the second light-emitting diode being adapted to emit substantially monochromatic light of a second wavelength towards the target area, the second wavelength being different from the first wavelength.
The light-shaping means may comprise means for increasing both the uniformity and the divergence of the light beams generated by the light-emitting diodes, and the light-shaping means may be provided in the form of a substantially planar plate that is adapted to transmit greater than about 85 percent all of the light emitted by the light-emitting diodes to the target area. The light-shaping plate may be adapted to cause light from the light-emitting diodes to be distributed in the target area in a Gaussian distribution.
The features and advantages of the present invention will be apparent to those of ordinary skill in the art in view of the detailed description of the preferred embodiment, which is made with reference to the drawings, a brief description of which is provided below.
REFERENCES:
patent: 4815848 (1989-03-01), Hadeishi
patent: 4929078 (1990-05-01), Harmon
patent: 5049487 (1991-09-01), Phillips et al.
patent: 5059394 (1991-10-01), Phillips et al.
patent: 5518689 (1996-05-01), Dosmann et al.
patent: 5611999 (1997-03-01), Dosmann et al.
Physical Optics Corporation “Light Shaping Diffusers” brochure, 2 pages, undated, prior art.
Shie, R. L., et al., article entitled “Surface relief holography for use in display screens”, Physical Optics Corporation, 8 pages, undated, prior art.
Bayer Corporation
Coe Roger Norman
Font Frank G.
Ratiff Reginald A.
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