Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrophotometer
Reexamination Certificate
2001-04-11
2004-04-27
Chang, Audrey (Department: 2872)
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrophotometer
C356S303000, C356S309000, C356S322000, C356S326000
Reexamination Certificate
active
06727988
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spectrophotometer and spectrophotometry capable of measuring intensity of light transmitted through a target sample and, more particularly, to a spectrophotometer provided with a precision drive means at its light intensity measuring unit for precisely moving said light intensity measuring unit, thus precisely measuring light intensity at any desired points, the present invention also relating to a spectrophotometry using such a spectrophotometer.
2. Description of the Prior Art
A conventional spectrophotometer and a spectrophotometry using such a conventional spectrophotometer will be described as follows:
FIG. 1
shows the construction of a conventional spectrophotometer. As shown in the drawing, the conventional spectrophotometer
100
comprises a light source
10
emitting a light beam having a predetermined wavelength range, and an optical fiber
20
guiding the light beam from the light source
10
to a target sample
30
. The spectrophotometer
100
also comprises a spectrometer head
40
and a signal-processing unit
90
. The spectrometer head
40
receives the light beam transmitted through the target sample
30
, and diffracts the light beam into discrete wavelengths to produce optical spectra, and measures light intensities of the optical spectra. The signal-processing unit
90
receives spectrometric analysis data of the target sample
30
from the spectrometer head
40
, and reproduces the distribution of light intensities of the spectra.
In the above spectrophotometer
100
, the spectrometer head
40
comprises a reflective diffraction grating
50
, a concave mirror
60
, and a photodiode array
70
. The reflective diffraction grating
50
is used for diffracting the light beam, transmitted through the target sample
30
, into discrete wavelengths to produce optical spectra. The concave mirror
60
reflects the diffracted light from the diffraction grating
50
, while the photodiode array
70
measures the intensity of incident light reflected by the concave mirror
60
.
The photodiode array
70
comprises a plurality of photodiodes
80
linearly arranged on a longitudinal mount at regular physical intervals “C”. The photodiodes
80
are devices, each of which is selectively activated to allow an electric current to flow through it in response to incident light, thus generating an output voltage that is almost proportional to the intensity of the incident light.
The optical spectra, produced through the diffraction of the light beam by the grating
50
into discrete wavelengths, are received by the photodiode array
70
, thus being measured in light intensity according to the wavelength. After a measurement of the light intensities of the optical spectra, the photodiode array
70
outputs spectrometric analysis data of the target sample
30
to the signal-processing unit
90
. Upon receiving the spectrometric analysis data of the target sample
30
from the photodiode array
70
of the spectrometer head
40
, the signal-processing unit
90
reproduces the distribution of light intensities of the spectra, and performs photometric comparisons of the spectrometric analysis data of the target sample
30
with those of a reference sample so as to identify and measure the components and contents of the target sample
30
.
FIG. 2
is a flowchart of a spectrophotometry using the conventional spectrophotometer.
As shown in the drawing, the spectrophotometry using the conventional spectrophotometer
100
comprises five steps, that is, a light transmitting step S
10
, a light diffraction step S
20
, a light reflection step S
30
, an intensity measurement step S
40
and an intensity distribution reproduction step S
50
.
At the first step, the so-called light transmitting step S
10
, a light beam, emitted from the light source
10
, is guided to the target sample
30
through the optical fiber
20
, and is transmitted through the sample
30
.
At the second step, the so-called light diffraction step S
20
, the light beam transmitted through the sample
30
is received into the reflective diffraction grating
50
of the spectrometer head
40
, thus being diffracted to produce optical spectra.
At the third step, the so-called light reflection step S
30
, the optical spectra of the diffracted light beam are reflected by the concave mirror
60
to the photodiode array
70
.
At the fourth step, the so-called intensity measurement step S
40
, the photodiode array
70
measures the light intensities of the incident optical spectra according to wavelength, thus obtaining spectrometric analysis data, such as the characteristics of the spectra according to wavelength.
At the fifth step, the so-called intensity distribution reproduction step S
50
, the spectrometric analysis data are transmitted from the photodiode array
70
to the signal-processing unit
90
. Upon reception of the spectrometric analysis data from the photodiode array
70
, the signal-processing unit
90
reproduces the light intensity distribution and performs spectrometric comparisons of said data with those of a reference sample, thus identifying and measuring the components and contents of the target sample
30
. The signal-processing unit
90
is thus able to provide the characteristics of light diffracted into discrete wavelengths.
In the conventional spectrophotometer
100
, the photodiodes
80
are linearly arranged along a longitudinal mount at regular intervals “C” to form a photodiode array
70
. However, the spectrophotometer
100
is problematic in that it is almost impossible to sense light at the intervals “C” between the photodiodes
80
.
The intervals “C” between the photodiodes
80
also reduce the resolving power of the conventional spectrophotometer
100
, and so the spectrophotometer
100
is not suitable for use in a precision measurement.
In the prior art, it has been actively studied to linearly arrange an increased number of photodiodes along the mount of a photodiode array to reduce the intervals “C” in an effort to solve the problems caused by said intervals “C”. However, the linear arrangement of such an increased number of photodiodes undesirably lengthens the signal processing time, and so it is almost impossible to use a spectrophotometer, having a photodiode array with such an increased number of photodiodes, in a real time measurement.
Another problem, experienced with such an increased number of photodiodes of a photodiode array, resides in that said increase undesirably results in a reduction in the size of each photodiode, and so the photodiodes may be easily saturated with light intensity.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a spectrophotometer and spectrophotometry, which uses a precision drive means capable of improving the resolving power during a measurement of light intensity.
Another object of the present invention is to provide a spectrophotometer and spectrophotometry, which uses a precision drive means attached to the photodiode array, thus precisely measuring light intensity while moving as desired.
In order to accomplish the above objects, an embodiment of the present invention provides a spectrophotometer, comprising: a light source used for emitting a light beam having a predetermined wavelength range; a light guiding means for guiding the light beam from the light source to a target sample; a spectrometer head consisting of a light diffracting means for diffracting the light beam transmitted through the target sample to produce optical spectra, a light reflecting means for reflecting the diffracted light from the light diffracting means, a light intensity measuring means for measuring intensity of incident light reflected by the light reflecting means, a drive means for reciprocating the intensity measuring means within a predetermined range, and a stop means for limiting a reciprocating movement of the intensity measuring means;
Kim Kyung Chan
Kim Soo Hyun
Oh Se Baek
Chang Audrey
Curtis Craig
Goldberg Richard M.
Korea Advanced Institute of Science and Technology
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