JP2009175017A - Method and apparatus for analysis - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analytical method and an analyzer capable of reducing measurement errors due to the dependency of optical filters on the angle of incidence. <P>SOLUTION: Light from a specimen 2 carried by a test strip 3 is passed through an optical system having an optical filter 6 and received by an image sensor 7 provided with a plurality of pixels to acquire concentration information of the specimen in the analytical method. The angle θ of the filter incidence incident onto the optical filter 6 of the light which forms an image in the pixels A is computed. The amount of shift of the filter band of the optical filter 6 corresponding to the angle θ of the filter incidence is acquired to acquire a correction coefficient corresponding to the amount of shift. The correction coefficient is used to correct luminance. Concentration information of the specimen 2 is acquired on the basis of this corrected luminance value. Since it is possible to reduce measurement errors due to the dependency of the optical filter 6 on the angle of incidence by this analytical method, measurement accuracy and reliability at the time of analyzing the specimen 2 are improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an analysis method and an analysis apparatus for obtaining concentration information of a specimen using an image sensor.

FIG. 5 shows a configuration of a conventional analyzer that obtains concentration information of the specimen carried on the test piece. In the conventional analyzer, the light from the light source 1 is applied to the test piece 3 on which the specimen 2 is carried, and the scattered light (or transmitted light or reflected light in some cases) from the test piece 3 is used as the lens 4. The image sensor 7 formed of a CCD or the like is irradiated with an image through an optical system including the diaphragm 5, the optical filter 6 and the like to form an image, and each pixel of the image sensor 7 (here, the pixel O in FIG. 5 is the optical system). The pixel at the position of the optical axis Z, which is the central axis of the optical axis Z, and the pixel A indicates a pixel deviated from the optical axis). 3 is configured to quantify the concentration of the specimen 2 carried on the surface 3 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 7-5110

  In the analyzer of the conventional configuration, in order to obtain the concentration of the sample 2 carried on the test piece 3, light from the sample 2 (scattered light amount, transmitted light amount, or reflected light amount) is acquired by the pixel of the image sensor 7. The pixel output value is the product of the light amount of the light source 1, the scattering intensity of the sample 2, and the sensitivity of the image sensor 7 in the light source 1, the sample 2, and the image sensor 7 each having wavelength characteristics. Among the wavelength characteristics obtained from the above, it is obtained as an integral value in a range satisfying the transmission wavelength band of the optical filter 6.

  For example, as shown in FIGS. 6 and 7, a light source 1 having a light quantity distribution as shown in FIG. 6 (a) with respect to a wavelength, a specimen 2 having a scattering characteristic as shown in FIG. 6 (b), When the image sensor 7 having the sensitivity distribution as shown in FIG. 6C is used, the wavelength characteristic representing the luminance is obtained as a characteristic as shown in FIG. Further, in the wavelength characteristic as shown in FIG. 7A (same as the characteristic shown in FIG. 6D), when the wavelength is limited by the optical filter 6 having the transmission characteristic as shown in FIG. The wavelength characteristic representing the luminance after passing through the filter 6 is as shown in FIG. 7C, and the integrated value (the area of the hatched portion in FIG. 7C) becomes the pixel output value of the image sensor 7.

  Incidentally, as shown in FIG. 5, the light (scattered light) from the specimen 2 existing on the optical axis Z enters the optical filter 6 substantially perpendicularly (that is, along the optical axis Z) and enters the pixel O. However, the scattered light of the specimen 2 that is imaged on the pixel A and separated from the optical axis Z has an incident angle θ with respect to a perpendicular (optical axis Z) perpendicular to the optical filter 6. At this time, the optical filter 6 has a so-called incident angle dependency in which the transmission wavelength band shifts in the negative direction according to the incident angle θ of light, and therefore, as shown by a dotted line in FIG. 8B. In addition, in the pixel A, the wavelength band of the imaged light is shifted in the negative direction compared to the pixel O. As a result, as shown in FIG. 8C, the wavelength characteristic of the luminance at the pixel A is also shifted in the negative direction of the wavelength band, and the change amount as shown in FIG. , The pixel output value at the pixel A also changes by the amount of change (decreases in the case shown in FIG. 8). That is, even with the same amount of light obtained from the same specimen 2, the pixel output value changes depending on the pixel position in the image sensor 7, resulting in a measurement error.

  The present invention solves the above-described conventional problems, and an object thereof is to provide an analysis method and an analysis apparatus that can reduce a measurement error due to an incident angle dependency of an optical filter.

  In order to solve the above-described conventional problems, the present invention is configured to receive light from a specimen carried on a test piece through an optical system having an optical filter by an image sensor having a plurality of pixels, and to provide concentration information on the specimen. And a filter incident angle detection step for detecting a filter incident angle of light that forms an image on a pixel, and a shift amount of a filter band of the optical filter corresponding to the filter incident angle. A correction amount setting step that sets a correction coefficient in accordance with the shift amount, a correction step that corrects a luminance value or a value corresponding to the luminance value using the correction coefficient, and correction in the correction step And a concentration acquisition step of obtaining concentration information of the specimen based on the corrected value.

Further, the present invention is an analyzer that obtains concentration information of the specimen by receiving light from the specimen carried on the test piece through an optical system having an optical filter by an image sensor having a plurality of pixels. Filter incident angle detecting means for detecting the filter incident angle of light that forms an image on the pixel and incident on the optical filter, shift amount acquiring means for obtaining the shift amount of the filter band of the optical filter corresponding to the filter incident angle, and the shift A correction coefficient setting means for setting a correction coefficient according to the amount; a correction means for correcting a luminance value or a value corresponding to the luminance value using the correction coefficient; and a correction value of the sample based on the correction value corrected by the correction means. And a density acquisition means for obtaining density information.

  According to the analysis method and the analysis apparatus, even when the specimen of the test piece is imaged by the image sensor and the light to the pixel of the image sensor passes through the optical filter at an incident angle (tilt), According to the incident angle of light to the pixel, the filter band shift amount and the correction coefficient of the optical filter corresponding to the incident angle of the filter are obtained, and the concentration information of the specimen is corrected well. Measurement errors due to angle dependency can be reduced.

  According to the analysis method and the analysis apparatus of the present invention, it is possible to reduce the measurement error due to the incident angle dependency of the optical filter, and the measurement accuracy and reliability when analyzing the specimen are improved.

Hereinafter, an analysis method and an analysis apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view showing a schematic configuration of an analyzer according to an embodiment of the present invention. The general configuration is the same as the configuration of the conventional analyzer shown in FIG. 5, and the same components are denoted by the same reference numerals and description thereof is omitted. As in the conventional analyzer, this analyzer has a light source for irradiating the test piece 3 with light, but is omitted in FIG.

  Here, the analysis device according to the embodiment of the present invention is different from the conventional analysis device in that a control unit that executes a unique correction algorithm for correcting the pixel output value from each pixel of the image sensor 7. (Not shown) is provided. The control unit that executes this correction algorithm includes a filter incident angle detection unit that detects a filter incident angle of light that forms an image on the pixel and is incident on the optical filter 6, and a filter band of the optical filter 6 that corresponds to the filter incident angle. Shift amount obtaining means for obtaining a shift amount (movement amount), correction coefficient setting means for setting a correction coefficient corresponding to the shift amount, correction means for correcting a luminance value using the correction coefficient, and a corrected luminance value Concentration acquisition means for obtaining concentration information of the specimen based on the above.

The correction algorithm will be described in detail below.
First, the incident angle when the light from the specimen 2 passes through the optical filter 6 is detected. FIG. 1 is a diagram showing an optical path in an optical system including a lens 4, a diaphragm 5, an optical filter 6, and the like. In FIG. 1, the principal ray of light whose incident angle to the optical filter 6 is perpendicular, that is, 0 ° with respect to a perpendicular perpendicular to the optical filter 6 is defined as the optical axis Z of the optical system. It is assumed that the light from the sample 2 located at is formed on the pixel O. Here, the light that forms an image on the pixel O is a collection of light beams distributed innumerably in a cone with the opening 5a of the diaphragm 5 as a bottom surface, so that each light beam other than the optical axis is slightly applied to the optical filter 6. Although it has an incident angle (inclination angle with respect to the optical axis Z), it is assumed here that the aperture diameter is sufficiently small, that is, all light rays are approximated to one optical axis Z. . In this case, since the transmission band of the optical filter 6 corresponding to the pixel O has no incident angle dependency and is a transmission band as designed, the pixel output value obtained in the pixel O is a true value.

  On the other hand, in the case of light that forms an image on the pixel A having an incident angle dependency on the optical filter 6, as in the case of the pixel O, the incident angle is considered when all light rays are approximated to chief rays. θ is as shown in (Equation 1) below.

θ = tan ⁻¹ (H1 / L) (Formula 1)
Here, L is a distance between the test piece 3 and the diaphragm 5 (distance between the test piece and the diaphragm), and H1 is an object height with respect to the pixel A (light of the portion of the specimen 2 corresponding to the pixel A in the test piece 3). Distance from the axis position).

  The object height H1 with respect to the pixel A can be obtained from the image height of the pixel A (distance from the central portion corresponding to the optical axis Z to the pixel A in the image sensor 7) H2 and the image magnification B of the optical system. The following (Formula 2) is obtained.

H1 = H2 / B (Formula 2)
Therefore, the incident angle θ of the light imaged on the pixel A can be obtained from (Expression 1) and (Expression 2).

  Next, a transmission band shift amount (transmission band movement amount) caused by the angle dependency of the optical filter 6 is obtained. The incident angle θ to the optical filter 6 and the transmission band shift amount with respect thereto are determined as the specifications of the optical filter 6. For example, it is easy to measure as design data at the time of manufacturing the optical filter 6 or after obtaining the optical filter. Is available. The relationship between the incident angle θ on the optical filter 6 and the transmission band shift amount draws a downward-sloping curve as shown in FIG. 2, for example. As a characteristic, the transmission band shifts in the minus direction as the incident angle to the optical filter 6 increases. By referring to this graph, the wavelength band of the light focused on the pixel A can be known.

  Next, how to obtain the correction coefficient according to the transmission band shift amount will be described with reference to FIG. The graph shown in FIG. 3 is the wavelength characteristic of the luminance shown in FIG. 6D described above, and this characteristic represents the amount of change in the measurement error due to the incident angle dependence of the optical filter 6, so that the correction is performed. This graph is used to obtain the coefficient.

  First, assuming that the center wavelength of the wavelength band of light imaged on the pixel O is λo, this is the design value of the transmission band of the optical filter 6 as described above. If the central wavelength of the wavelength band of the light focused on the pixel A is λa, the value of λa can be obtained from the incident angle and the transmission band shift amount. The luminance at the center wavelength λo and the center wavelength λa can be obtained from this graph, and is assumed to be Io and Ia, respectively. This means that the luminance that should originally be obtained as the luminance Io in the pixel A is obtained as the luminance Ia by the transmission band shift due to the angle dependency of the optical filter 6, and the luminance becomes Io for correction. It is necessary to multiply the luminance Ia by such a correction coefficient. That is, the correction coefficient αa is as follows.

αa = Io / Ia (Formula 3)
Finally, a correction method using the correction coefficient will be described with reference to FIG. As shown in FIG. 4, the pixel output value of the pixel A that is affected by the incident angle dependency of the optical filter 6 is multiplied by the correction coefficient αa. Then, the luminance at each wavelength increases by the amount multiplied by the correction coefficient αa, and becomes the same level as the luminance at the pixel O. That is, the pixel output value at the pixel A, which is the integrated value of the luminance with respect to the wavelength, also becomes a pixel output value at the pixel O, that is, a value close to the true value, and the influence of the incident angle dependency of the optical filter 6 is corrected. Thus, the optical filter 6 can be brought close to the incident angle dependency. Further, the correction coefficient is calculated in the same process for other pixels on the image sensor 7, and the obtained pixel output value is multiplied by the correction coefficient corresponding to each pixel position to thereby obtain the optical filter 6. Can be minimized.

  For example, when the wavelength characteristic of the specimen 2 does not change with time or the environment, the wavelength characteristic of luminance does not change, so the correction coefficient held in each pixel may be one pattern. Further, when there are several types of specimens 2, correction coefficients corresponding to the wavelength characteristics of the respective specimens 2 are created in advance, and the correction coefficient pattern may be changed for each specimen 2 each time.

  As described above, the incident angle to the optical filter 6 is obtained, the transmission band shift amount of the optical filter 6 with respect to the angle is obtained, and the corresponding pixel output value is multiplied by the correction coefficient obtained from the change in luminance with respect to the shift amount. By using this algorithm, a pixel output value close to the true value can be obtained at any pixel on the image sensor 7.

  Thus, according to the analysis method and the analysis apparatus of the present invention, the measurement error due to the incident angle dependency of the optical filter 6 can be reduced, and the measurement accuracy and reliability when analyzing the specimen 2 are improved. be able to. For example, when the measurement error in the absorbance widely used as an index for measuring the concentration of the subject (specimen 2) using light is observed, when the incident angle θ to the optical filter 6 is about 30 degrees, In the case where the correction is not performed, the measurement error of the sample 7 is 5% or more. However, when the correction is performed using the above algorithm, the measurement error of the concentration of the sample 2 is 0.2% to 0.3%. It became possible to suppress to.

  In the above embodiment, the luminance value is corrected using the correction coefficient, and the concentration information of the specimen 2 is obtained based on the luminance correction value. However, the present invention is not limited to this, and digital data corresponding to the luminance value is used. Etc. may be corrected, and the concentration information of the specimen 2 may be obtained based on the correction data.

  The analysis method and analysis apparatus according to the present invention have a function of reducing measurement errors due to the incident angle dependency of an optical filter, and are particularly useful for biochemical analysis methods and apparatuses that require concentration detection with high accuracy.

The front view which shows roughly the structure of the analyzer which concerns on embodiment of this invention The figure which shows the relationship (characteristic) of the incident angle to the optical filter of the analyzer which concerns on the same embodiment, and an analysis method, and the amount of transmission band shifts The figure which shows the wavelength characteristic of the brightness | luminance of the analyzer and analysis method which concern on the same embodiment The figure which shows the wavelength characteristic of the brightness | luminance after the optical filter transmission of the analyzer and analysis method which concern on the same embodiment A perspective view schematically showing the configuration of a conventional analyzer (A)-(d) is the figure which shows the wavelength characteristic of the light source of an analyzer, respectively, the figure which shows the scattering characteristic of a test substance, the figure which shows the sensitivity distribution of an image sensor, and the figure which shows the wavelength characteristic of a brightness | luminance (A)-(c) is a figure which shows the wavelength characteristic of a brightness | luminance in an analyzer, respectively, The figure which shows the transmission characteristic of an optical filter, The figure which shows the wavelength characteristic of the brightness | luminance after optical filter transmission (A)-(c) is a figure which shows the wavelength characteristic of a brightness | luminance in an analyzer, respectively, The figure which shows the transmission characteristic of an optical filter, The figure which shows the wavelength characteristic of the brightness | luminance after optical filter transmission

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Sample 3 Test piece 4 Lens 5 Aperture 6 Optical filter 7 Image sensor

Claims (2)

An analysis method for receiving light from a specimen carried on a test piece through an optical system having an optical filter by an image sensor having a plurality of pixels to obtain concentration information of the specimen,
A filter incident angle detecting step for detecting a filter incident angle of light that forms an image on the pixel and that enters the optical filter;
A shift amount obtaining step for obtaining a shift amount of the filter band of the optical filter corresponding to the filter incident angle;
A correction coefficient setting step for setting a correction coefficient according to the shift amount;
A correction step of correcting a luminance value or a value corresponding to the luminance value using the correction coefficient;
A concentration acquisition step of obtaining concentration information of the specimen based on the correction value corrected in the correction step. An analyzer that receives light from a specimen carried on a test piece through an optical system having an optical filter by an image sensor having a plurality of pixels to obtain density information of the specimen,
Filter incident angle detection means for detecting a filter incident angle of light that forms an image on a pixel and is incident on an optical filter;
Shift amount acquisition means for obtaining the shift amount of the filter band of the optical filter corresponding to the filter incident angle;
Correction coefficient setting means for setting a correction coefficient according to the shift amount;
Correction means for correcting a luminance value or a value corresponding to the luminance value using the correction coefficient;
An analyzer comprising: a concentration acquisition unit that obtains concentration information of the specimen based on the correction value corrected by the correction unit.

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