JPH0534611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application of the Invention The present invention relates to a spectrophotometer using a diffraction grating.

(b) Prior Art A spectrophotometer using a diffraction grating uses a filter to remove unnecessary light such as stray light and higher-order diffracted light. These filters need to be switched depending on the wavelength range to be measured. Conventionally, filters were replaced by rotating a plate on which multiple types of filters were attached using a mechanism such as a cam linked to the wavelength scanning of a spectrometer. A method was used in which a filter was switched at a specific wavelength position in a spectrometer. In the former method, a disk equipped with a filter rotates continuously in conjunction with wavelength scanning.
Filter replacement proceeds gradually and continuously over a certain wavelength range of the spectrometer, so there is no difference in the filter replacement position in the spectrum measurement record, but it is mechanically complex and the mechanism is The disadvantages are that adjustment is troublesome, the filter has a large shape, and is therefore expensive. The reason why filters are so large is that a certain wavelength range is covered by one filter, but since the filter rotates in conjunction with wavelength scanning, one filter can cover a certain wavelength range. remains in the optical path of the spectrophotometer, the filter needs to have an area considerably larger than the cross-section of the optical path. The latter method, in which the filter is replaced at a specific wavelength, is mechanically simple because it uses a pulse motor or the like to insert one of multiple filters into the optical path of the spectrophotometer. Since the filter does not move within the range, the filter area only needs to be slightly larger than the cross section of the optical path, and there is an advantage that the filter can be small, but the filter is replaced discontinuously at specific wavelength positions. , it is necessary to temporarily stop wavelength scanning at the filter exchange position, which makes high-speed wavelength scanning difficult, and because filter exchange is discontinuous, there is no need to record spectra without sudden stray light, etc. The disadvantage is that a step appears as a result of the change.

(c) Purpose The present invention aims to eliminate the drawbacks of the above-mentioned conventional methods regarding filter replacement.

(d) Structure The present invention uses one filter as shown in FIG.
A wavelength range A in which Fa is used, and adjacent to it,
Set one wavelength range Δ including the boundary with wavelength range B in which filter Fb is used, and drive the filter only while the spectrometer passes through this wavelength range during wavelength scanning. The feature is that filters A and B are replaced continuously.

(E) Example FIG. 2 shows a spectrophotometer of the present invention. 1 is a light source,
2 is a spectroscope, and the monochromatic light flux f emitted from the spectroscope 2 is split into two light fluxes by a sector mirror M1,
A sample cell S is inserted into one of these two light beams, a reference cell R is inserted into the other light beam, and these two light beams are overlapped again on the same optical path by a sector mirror M2 and made to alternately enter the light receiving element D. The filter F is inserted into a single beam portion between the spectroscope 1 and the sector mirror M1. This configuration is the same as a conventional double beam spectrophotometer. The feature of the present invention lies in the filter drive control method.

FIG. 3 shows the structure of the filter in the above embodiment. F1, F2, . . . are a plurality of types of filters attached to a fan-shaped plate 3, and the fan-shaped plate 3 is rotated by a pulse motor PM. The PC is provided at a position where the edge of the fan-shaped plate 3 is sandwiched between the photocouplers, and the position where one edge of the fan-shaped plate 3 is detected by the photocoupler PC is the origin position of the filter configuration. , filter F1
is inserted into the optical path of the output beam f of the spectrometer 2.

FIG. 4 shows the configuration of the control circuit in the above embodiment. The CPU is a central control unit with driver circuit 4,
The rotation of the pulse motor PM and the wavelength scanning pulse motor 6 of the spectrometer 2 is controlled via the pulse motor 5, and the pulses sent to the pulse motor 5 are counted and
The wavelength position of is detected. The wavelength scanning range of the spectrometer 2 is divided into first, second, . . . from the wavelength origin side, with the wavelength at the wavelength origin being λ0, and the boundary wavelength between the first and second divisions being λ1, etc. A wavelength range of ±Δλ is set around the boundary wavelengths λ1, λ2, . . . of each division. The CPU controls the position of the sector plate 3 so that the filter F1 is inserted into the light beam f while the spectrometer is in the wavelength range of λ0 and λ1-Δλ. That is, in this wavelength range, the fan-shaped plate is stopped at a position where the edge detection signal of the fan-shaped plate 3 is output from the photocoupler PC.
When spectrometer 2 enters the range from λ1-Δλ to λ1+Δλ,
A pulse is also output to the driver circuit 4 in synchronization with the wavelength sending pulse of the spectrometer 2 to drive the pulse motor.
The PM is driven, and as the wavelength position of the spectrometer advances from λ1 - Δλ to λ1 + Δλ, the sector plate 3 is rotated to cause the filter F2 to enter the light beam f. In this way, when the wavelength position of the spectrometer reaches λ1+Δλ, the filter F1 completely escapes from the light beam f, and the filter F2 is completely inserted into f. Filters are replaced continuously in the same manner before and after the boundaries of other wavelength divisions. When the wavelength position of the spectrometer is in the range of λi±Δλ, two types of filters Fi and Fi+1 are inserted into the output beam f of the spectrometer 2, and each beam cross-section occupation ratio is equal to the wavelength of the spectrometer. It changes continuously with scanning, and one filter occupies the cross section of the light beam f outside the range of Δλ before and after the division boundary, and the filter is stopped.

Note that in FIG. 4, the output of the light receiving element D is A/D converted and read into the CPU, and the CPU drives the display device 7 based on the wavelength data and the output data of the light receiving element D to display or record the spectrum. let

Although the above embodiments apply the present invention to a double beam spectrophotometer, it goes without saying that the present invention can also be applied to a single beam spectrophotometer.

(f) Effects According to the present invention, since the filter changes continuously from A to B within a certain wavelength range, no steps appear on the spectrum display due to sudden changes such as stray light, and the filter While the spectrometer is scanning wavelengths, it moves only in a certain wavelength range and stops in most of the wavelength range corresponding to each filter. The area only needs to be slightly larger than the cross section of the light beam, the filter can be made small, and a mechanism linked to the spectrometer mechanism is not required, so it is mechanically simple and easy to adjust.

[Brief explanation of the drawing]

Fig. 1 is a graph explaining the wavelength range for filter replacement, Fig. 2 is a plan view of the optical part of one embodiment of the present invention, Fig. 3 is a perspective view of the filter configuration in the same embodiment, and Fig. 4 is a block diagram of a control circuit in the same embodiment. 1...Light source, 2...Spectroscope, F...Filter configuration, F
1, F2...filter, 3...sector plate, PM...pulse motor, PC...photocoupler.

Claims (1)

[Claims] 1 A rotary plate in which multiple types of filters are attached with their edges adjacent to each other, driven by a pulse motor, a wavelength position detection means of a spectrometer, and a wavelength position of the spectrometer is determined by the detection means to match the filter exchange wavelength. The pulse motor is driven in synchronization with the wavelength feed of the spectrometer only while the wavelength is detected to be within a predetermined narrow wavelength range before and after the spectrometer passes through the wavelength range. A spectrophotometer characterized in that it is equipped with a control circuit for switching filters from one filter to an adjacent filter.