JPH0441939B2 - - Google Patents

Description

[Detailed Description of the Invention] [1] Technical Field The present invention relates to an improved wavelength calibration method for a device that analyzes the state of pigments on the surface of a living body by shining light on the surface of a living tissue and spectroscopically analyzing the reflected light. Related.

[2] Prior art and its problems Conventionally, the wavelength calibration of this device used a method of aligning the wavelength axis with the peak wavelength of the transmission spectrum using a wavelength calibrator using an interference filter (peak wavelength 571 nm). That is, the spectrum of the light transmitted through the interference filter 21 of the calibrator in FIG.
Waveform a in FIG. B, whose peak wavelength is λ ₀ , is subjected to wave calibration by shifting waveform b before calibration by wavelength δ to match a.

However, there is a relationship between the above λ ₀ and the filter thickness t as follows: λ ₀ = 2/3t (1), and this thickness t depends on the manufacturing lot of the filter and the inclination of the filter with respect to the optical axis. It was not uniform, and therefore the peak wavelength λ ₀ also varied.

Furthermore, the method of aligning the X axis (wavelength axis) with this peak wavelength λ ₀ has conventionally been carried out by moving a cursor to the wavelength peak value (571 nm) as shown in FIG. This was a very intuitive method and had poor accuracy.

[3] Purpose The purpose of the present invention is to provide an accurate and highly reproducible wavelength calibration method for a spectrometer.

[4] Means for solving the problems In the calibration method of the present invention that solves the above problems, the peak wavelength is determined by using a filter that gives a spectral waveform specific to the material that makes up the filter, regardless of the thickness of the interference filter. It is characterized by shifting. A particularly suitable structure for such a filter is, for example, one in which deidium is deposited on the surface of a glass substrate. The transmission spectrum waveform is as shown in FIG.

The automatic wavelength calibration method using this daymium filter will be described below. In FIG. 5, the solid line spectrum waveform is a calibrated spectrum waveform measured with a spectrometer calibrated with a laser beam or the like. This spectrum is stored in the device. The spectral waveform indicated by the dotted line is a waveform measured with a spectrometer whose wavelength is shifted by Δλ.

Here, the calibrated spectrum waveform is IT (λ), the measured waveform is ID (λ), and the shift amount between the two (the shaded area in Figure 5) I _DW is calculated using the following formula:
It is calculated by integrating over a wavelength range [a, b] that has a characteristic transmission spectrum of the transmission filter used.

I _DW =∫ _a ^b [IT (λ) − ID (λ + Δλ)] ² dλ ...(2) Now, if we plot the wavelength deviation Δλ and the shift amount I _DW , we get Δλ= I _DW is minimum when 0...(3).

Calibration can be performed automatically if I _DW is calculated using this characteristic, Δλ is shifted so as to minimize this value, and calibration is completed when I _DW becomes minimum.

[5] Example A flowchart of implementation steps based on the above-mentioned principle is shown in FIG.

An example implemented using the above steps is shown in FIG.

[6] Effect Highly accurate automatic wavelength calibration is now possible.

This allows highly sensitive and reliable reflection spectrum measurement. It is also reproducible due to quantitative calibration.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the I _DW value calculated by the wavelength calibration method and used as a standard for determining calibration and the wavelength deviation Δλ. FIG. 2A shows an interference filter used in a conventional wavelength calibrator, and FIG. 2B shows the transmission spectrum and the relationship between its center wavelength λ ₀ and the filter thickness t. Figure 3 describes how to adjust the conventional wavelength calibration method.
This shows how the cursor is shifted according to the peak wavelength of the filter. FIG. 4 shows the transmission spectrum of a deidium filter having a material-specific spectrum as one of the embodiments of the present invention. Figure 5 is the 4th
The principle diagram of the wavelength calibration method when using the deidium filter shown in the figure is shown. FIG. 6 shows a flowchart of the implementation steps. FIG. 7 shows an example of wavelength calibration in this apparatus when using an absorption spectrum instead of a transmission spectrum.

Claims (1)

[Claims] 1. In a wavelength calibration method used in a tissue spectrometer that diagnoses the state of the tissue by projecting light onto living tissue and analyzing the reflected light using a spectrum spectrometer, a calibrated spectrometer is used. The means for measuring and storing the spectral waveform ID (λ) of the light transmitted through the interference filter measured using the calibrated spectrometer, and the means for measuring the spectral waveform ID (λ) of the spectrometer to be calibrated, and the memorized waveform IT (λ) ), and a means for calculating the integral ^value I _DW of the _deviation with respect to the wavelength λ from the A wavelength calibration method characterized by shifting the wavelength axis. 2. The wavelength calibration method according to claim 1, characterized in that a filter in which deidiumium is vapor-deposited on the surface of a glass substrate is used as an interference filter for wavelength calibration.