JPH0672803B2 - Visible UV spectrophotometer - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absorption spectrophotometer having measurement wavelengths in both ultraviolet and visible regions.

B. Prior Art In this type of spectrophotometer, referring to FIG. 1, a deuterium lamp L1 for the ultraviolet range and a halogen lamp L2 for the visible range are used in the light source section (a), and both are switched. Therefore, the measurement wavelength range is selected. Both lamps L1 and L2 are installed on a fan-shaped turntable 1, and the turntable 1 is configured to be rotated by a predetermined angle by a pulse motor PM1 so as to switch the light from the selected light source lamp. Reflected by concave mirror M1, entrance slit 2
Through the diffraction grating 3 of the spectroscopic section (b) to form an image on the exit slit 4, and the high-order diffracted light cut filter 5 removes the high-order diffracted light to obtain monochromatic light. This monochromatic light is split into two beams by the half mirror HM,
The light passes through the sample cell SAM and the control cell REF, is photoelectrically converted by the photodetectors D1 and D2 of the photometric section (C), and is amplified by the amplifier A1.
A and A2 are amplified, the control side voltage VR and the sample side voltage VS are alternately switched by the switch S1 and A / D converted by the A / D converter 6, and then a control device composed of a microcomputer (d). Captured by T = VS / VR × 100
The transmittance of the sample can be obtained by (%). In this way, the transmittance is plotted for each wavelength. PM2
Is a pulse motor for rotating the diffraction grating 3 to scan the wavelength.

In the above configuration, switching of the light source is performed by controlling the pulse motor PM1 using a micro computer, but conventionally, the origin of the rotation angle of the pulse motor PM1 (for example, one light source position) is set to a micro switch or a photoelectric switch. The light source is switched by rotating the motor from that position by a predetermined number of steps. However, since this origin position detecting means is premised on being fixed in the positional relationship between the rotary base 1 and the lamps L1 and L2 installed thereon, the lamp may be replaced or aged with time. If there is a deviation in the light emission center, there is no means to correct it and the amount of light incident on the entrance slit 2 decreases. Further, the initial setting of the filter switching pulse motor PM3 for switching the high-order diffracted light cutting filter 5 is also performed by the micro switch or the photoelectric switch, which is one of the causes of the high cost.

C. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks. Even if the positional relationship between the rotary table supporting the lamp and the light emission center of the lamp deviates for some reason, the maximum amount of light can always be made incident on the entrance slit. While providing the position detection means of the turntable,
It is an object of the present invention to omit a micro switch or a photoelectric switch as a position detecting means of a filter for a high order diffracted light cut and its associated wiring.

D. Structure of the invention The present invention, a light source unit having a switching means between the light source for the visible region and the light source for the ultraviolet region, a spectroscopic unit consisting of a diffraction grating for splitting the light from the light source unit and a filter group for cutting higher-order diffracted light. In a spectrophotometer equipped with a photometric unit for measuring the light from the spectroscopic unit through the sample, the initial setting of the pulse motor for driving the rotary table for light source switching is performed by rotating the pulse motor one step at a time. It is equipped with a control device that detects the position of each light source and the position of the slit provided on the rotating disc by determining the output of the photometric unit of the spectrophotometer itself. Alternatively, instead of the initial setting means of the pulse motor using a photoelectric switch or the like, in the light source switching rotary table, the maximum value of the output of the photometric unit passes through the entrance slit. The maximum light intensity is detected, and in the rotary disc for filter switching, the position of the slit provided on the rotary disc is detected by discriminating the output of the photometric unit of the spectrophotometer itself, and the rotation at this time is detected. The angles are initially set as the light source position and the filter switching origin position, respectively.

E. Embodiment FIG. 1 shows an embodiment of the present invention. In the light source section (a), a halogen lamp L2 for the visible range and a deuterium lamp L1 for the ultraviolet range are installed on a fan-shaped turntable 1, and the turntable 1 is rotationally driven by a pulse motor PM1. It is becoming like this. Light from the selected light source lamp (ultraviolet lamp L1 in the figure) is condensed by the concave mirror M1, passes through the entrance slit 2 and enters the spectroscopic section (b).
In the spectroscope (b), the incident light is dispersed by the diffraction grating 3 whose rotation is controlled by the pulse motor PM2, and the monochromatic light having a predetermined wavelength is emitted from the exit slit 4. Each element F1, F2, ... Of the filter 5 for cutting higher-order diffracted light from the emitted light is rotated by a filter switching pulse motor PM3 as shown in FIG. Board 6
They are lined up in the vicinity of, and these filter groups F1, F2,…
And a slit 15 serving as a position detection mark is provided on the same circumference. The rotary disc 6 is arranged in the vicinity of the exit slit 4 in close proximity. The light passing through the high-order diffracted light cut filter 5 is split into two beams by the half mirror HM, passes through the sample cell SAM and the control cell REF, and is detected by the photodetectors D1 and D2 of the photometric section (C), respectively. Photoelectric conversion is performed by. The outputs of photodetectors D1 and D2 are amplified by amplifiers A1 and A2, respectively, and then switched.
It is switched alternately by S1, converted into a digital value by the A / D converter 7, and arithmetically processed by the control unit (d) composed of a micro computer. That is, if the voltage on the sample side is VS and the voltage on the control side is VR, then T = VS / VR
The transmittance of the sample can be determined by × 100 (%). This transmittance is obtained for all wavelengths by sequentially rotating the diffraction grating 3 with the pulse motor PM2. The control unit (d) is composed of a CPU8, a ROM9, a PAM10, a display device 11 and the like, and processes the analysis data and controls the pulse motors PM1, PM2 and PM3 so that a light source,
The measurement wavelength and filter are switched.

As described above, the pulse motor PM1 is controlled to control the light sources L1 and L1.
In order to switch 2 and control the pulse motor PM3 to switch the filter groups F1, F2, ..., The reference positions of the rotation angles of the pulse motors PM1 and PM3 must be given to the CPU as information. For that purpose, conventionally, the rotary table 1 and the rotary disk 6 are initialized by using a micro switch or a photoelectric switch, but in the present invention, the light source position and the filter position are initialized by the following means. Make settings.

FIG. 2 shows an example of a drive mechanism for switching the rotary base 1 by the pulse motor PM1. The eccentric shaft 12 provided on the motor shaft and the elongated hole 13 provided on the rotary base 1 are engaged with each other. ,
Rotate the pulse motor PM1 once, during which the photometric unit (c)
It detects the point where the output of shows the maximum value. To do this, first set the diffraction grating 3 of the spectroscopic section (b) in the ultraviolet region, for example,
It is set near 290 nm, and the origin position of the high-order optical cut filter 5 is not yet known, so set it at an arbitrary position. Next, while only the deuterium lamp L1 is turned on, the pulse motor PM1 is rotated step by step in that state, and the signal VR on the reference cell REF side is read into the microcomputer through the A / D converter 7 for each step, and the motor is read. By making one rotation, the turntable 1 is reciprocated once, and the position where the value of VR is the maximum value in each step is determined as the ultraviolet light source position. However, depending on the position of the filter rotary disc 6, even if the rotary table 1 is reciprocated once, the light of 290 nm may not enter the photometric unit at all or almost. This is 290n
The exit slitter 4 is a filter that cuts light in the wavelength range of m.
Or the frame between the filters overlaps the exit slit. Therefore, if the output of the photometric unit does not exceed a certain level even if the rotary table 1 is reciprocated once, the rotary disc 6 is rotated 100 ° in that direction from that position. The filters F1, F2 ... are projected around the rotating disc 6 in the range of 90 °, and the rotating disc is 100 °.
When it is rotated, the transparent portion of the disk 6 where the filter is not protruded comes after the exit slit 4. Then, the rotary table 1 is reciprocated once again to detect the position where the photometric output is maximum, and the count of the drive pulses of the motor PM1 at that time is stored and used as the position of the deuterium lamp L1.

When the position of the ultraviolet light source L1 is determined as described above, the origin of the filter rotating disk 6 is detected next. The diffraction grating 3 is set to the 290 nm position until L1 is turned on, and the device state is set so that the output voltage of the photometric unit becomes maximum, so rotate the rotating disk 6 step by step. When,
Eventually, a protrusion 14 provided with a slit 15 at the peripheral edge of the disc 6
Comes after the exit slit 4 to block the light, and when the disk 6 is further rotated, the slit 15 coincides with the exit slit 4 and the output of the photometric unit again reaches the maximum value. Therefore, it is determined that the slit 15 coincides with the exit slit 4 when the output of the photometric unit once drops to the level of the light-shielding state and then reaches the maximum again with a constant rotation amount of the disc 6, and the disc 6 at this time is determined. The position of is the origin position and the number of drive pulses of the pulse motor PM3 is stored.

When the origin of the filter rotating disk 6 is determined by the above-mentioned point, the position of the visible light source L2 is finally detected. That is, after setting the diffraction grating 3 in the visible light region, for example, near 540 nm, and setting the filter 5 in the same region, only the halogen lamp L2 is turned on, and the pulse motor PM1 is set to the deuterium lamp L1.
The stepper rotation is performed only within a certain range that is apart from the fixed position determined by the design by the fixed rotation angle, and the VR value for each step is also obtained, and the position of the pulse motor PM1 corresponding to the maximum value is visible. Determined as the area light source position. After that, by controlling the pulse motor using these position data, the light source can be switched so that the lamp is always at the optimum position. In the above embodiment, the light source is switched by rotating the lamp with the turntable, but the lamp is fixed and the concave mirror provided on the turntable is rotated to switch the light source. It may be performed. Further, although the present embodiment has shown the example of the double beam system using the half mirror, it may be a single beam system or a chopping double beam system using a rotating mirror. Either the light source or the filter may be initialized first.

F. As described above, the present invention does not separately use a micro switch or a photoelectric switch as the initial setting means of the light source switching rotary base and the filter switching rotary disk, and each driving pulse motor is stepped by one step. Since the position of the light source and the position of the slit are detected by discriminating the output of the photometering unit while rotating, the spectrophotometer is equipped with a metering unit by simply adding a program for the microcomputer. This has the advantage that the parts can be used and the cost can be reduced accordingly. Further, even if the positional relationship between the rotary base and the light emission center is deviated due to the replacement of the lamp or the like, there is an advantage that the maximum light quantity can always be set to enter the entrance slit of the spectroscope.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a perspective view of a light source switching rotary base of the above, and FIG. 3 is a perspective view of a filter switching rotary disk of the same. 1 ... Turning table, 2 ... Inlet slit, 3 ... Diffraction grating,
4 ... Exit slit, 5 ... Filter for high-order diffracted light cut, 6 ... Rotating disk, 7 ... A / D converter, 8 ... CP
U, 9 ... ROM, 10 ... RAM, 11 ... Display device, 12 ... Eccentric shaft, 13 ... Oval hole, 14 ... Convex portion, 15 ... Slit,
(A) …… Light source section, (b) …… Spectroscopic section, (c) …… Photometry section, (d) …… Control device, L1 …… Visible light source, L2 ……
Light source for ultraviolet region, PM1 ... Pulse motor for switching light source, PM2 ...
… Diffraction grating drive pulse motor, PM3 …… Filter switching pulse motor.

Claims (1)

[Claims] 1. A light source section having means for switching between a light source for visible range and a light source for ultraviolet range, and a spectroscopic section comprising a diffraction grating for spectrally splitting light from the light source section and a filter group for cutting high-order diffracted light. In a spectrophotometer equipped with a photometric unit for measuring the light from the spectroscopic unit through the sample, a control device for controlling light source switching and filter replacement is provided, and the light source switching means is provided at the position of the two light sources. Is moved by a pulse motor to position any one of the light sources at a use position, and the filter replacement means is provided by arranging the filter groups in a row on the same circle on one rotating disk, and A slit that indicates the origin of the same disk is provided on the circumference, and this rotating disk is driven by a pulse motor so that one filter is positioned on the optical path of the spectroscopic unit. In the determining operation, the control device sets the diffraction grating to one wavelength position in the ultraviolet region for the ultraviolet light source, turns on the ultraviolet light source, and drives the pulse motor for switching the light source while performing photometry. The position of the UV light source showing the maximum output of the section is detected, the position is stored, and for the visible light source, the diffraction grating is set to one wavelength in the visible range, and the same as above. In the operation of driving the pulse motor to detect the position where the output of the photometry unit becomes maximum, storing the position, and determining the origin position of the rotating disk in which the filter group is arranged, in the ultraviolet range, Turns on one of the visible light sources at its use position, sets the diffraction grating to one wavelength in the wavelength range of the light emitted from that light source, rotates the rotating disk, and passes through the slit on the disk. The same circle when the detected light is detected by the metering unit Visible purple external spectrophotometer, characterized in that is adapted to the origin position the rotational position of the.