JPH04290933A - Diffraction grating drive device - Google Patents

Abstract

PURPOSE:To accomplish a diffraction grating drive device in a small size, with which wavelength scan with constant scan speed can be made using a simple control system, by furnishing the drive device with a rotational angle instructing device to generate an output in accordance with the sine of the rotational angle. CONSTITUTION:A diffraction grating 5 is installed in the rotating center position on a rotary drum 4, which is coupled directly with the rotary shaft of a motor 3 driven by a motor driving circuit 8, and a recording medium 1 is provided on the peripheral surface of this rotary drum 4. Pulses in accordance with the sine of the rotational angle from the reference position of the diffraction grating 5 are generated by a sensor 2 which is instal led confronting the recording medium 1, and also further a counter 7 for counting these pulses and a rotating direction sensing circuit 6 are furnished. This constitution allows elimination of any sine bar mechanism or develeration mechanism, and the driving device can be constructed in small size. Also the control system can be simplified, and wavelength scan be performed with constant scan speed using simple control system. Simplification of the control mechanism leads to achieving the wavelength scan performed at a high speed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to driving a diffraction grating in a spectrometer.

0002

2. Description of the Related Art Conventionally, a so-called sine bar mechanism has been used as a drive device for a diffraction grating.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 63-167226, a diffraction grating is rotated by a DC servo motor, the rotation angle is detected as a pulse by a rotary encoder, and the wavelength of the emitted light is calculated and determined based on the pulse. method is now possible.

0004

The prior art using the above-mentioned sine bar mechanism has the drawbacks that the mechanism is complicated and large, and that there is a limit to the scanning speed.

Furthermore, the method disclosed in JP-A-63-167226 requires an arithmetic circuit to determine the wavelength, and has the disadvantage that the motor control system becomes complicated if wavelength scanning is attempted at a constant wavelength scanning speed. was there.

In view of the above-mentioned problems, it is an object of the present invention to provide a diffraction grating driving device that is compact and capable of high-speed scanning, and that can perform wavelength scanning with a constant wavelength scanning speed using a simple control system. .

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a rotating drum 4 directly connected to a rotating shaft of a motor 3.
A diffraction grating 5 is provided at the upper rotational center position, a recording medium 1 is provided on the circumferential surface of the rotating drum 4, and a sensor 2 provided facing the recording medium 1 detects the sine of the rotation angle from the reference position of the diffraction grating 5. A counter 7 is provided to generate corresponding pulses and count the pulses.

[0008]

[Operation] Since the number of pulses is counted according to the sine of the rotation angle, the relationship between the number of counts and the wavelength of the emitted light is linear, and wavelength scanning with a constant wavelength scanning speed can be performed with a simple control system. Furthermore, since the sine bar mechanism is no longer necessary, the drive device can be made smaller.

[0009]

[Embodiment] FIG. 1 is a diagram showing an embodiment of the present invention, in which a motor 3 is driven by a motor drive circuit 8 in response to a signal from a control section, and the rotation center on a rotating drum 4 directly connected to the rotation shaft of the motor 3. A diffraction grating 5 is installed at a position, and a wavelength indicating groove 1 is formed on the circumferential surface of the rotating drum 4 in accordance with the sine of the rotation angle of the diffraction grating 5.
An optical sensor 2 provided opposite to the wavelength indicating groove 1 detects the groove 1 and outputs a two-phase pulse.

The positional relationship between the optical sensor 2 and the wavelength indicating groove 1 is determined based on the 0th-order diffracted light, which has sufficient intensity compared to other diffracted lights. The pulse output of the optical sensor 2 is input to the rotation direction detection circuit 6 and the counter 7.
Then, pulses are added or subtracted according to the input from the rotation direction detection circuit 6 and output to the control section.

The initial position of the wavelength is determined based on the zero-order diffracted light.

FIG. 2 is a block diagram of an embodiment of a spectrophotometer using the present invention. The control unit 9 connects a wavelength drive unit 10 , a photomultiplier signal A/D conversion unit 11 , a photomultiplier drive unit 12 , a slit drive unit 13 , a filter drive unit 14 , and a light source switching unit 15 via a control bus 21 .
, is connected to the recorder D/A converter 16. The output of the recorder D/A converter 16 is connected to the recorder 17. Further, a data processing section 18 is connected to the control section 9, and a printer 19 is connected to the data processing section 18. In addition, a wavelength drive section 10, a photomultiplier signal A/D conversion section 1
1. The photomultiplier driving section 12, the slit driving section 13, the filter driving section 14, and the light source switching section 15 are connected to the optical system 20.

FIG. 3 is a diagram showing the main parts of the optical system 20 of the spectrophotometer. The light from the light source I 22 or the light source II 23 is selected by the light source switching mechanism 24 and enters the diffraction grating 5 through the entrance optical system 25 and the entrance slit 26 . The diffracted light from the diffraction grating 5 passes through an output slit 27, a filter 28, and an output optical system 29, and then passes through a photomultiplier 30.
incident on .

FIG. 4 is an explanatory diagram of the action of the diffraction grating. In FIG. 4, the diffraction grating 5 is provided so as to be rotatable about the rotation axis 31, and the entrance slit 26 and the output slit 27 are installed so that the opening angle with respect to the rotation axis 31 is K, so that the incident light 32 is directed to the perpendicular line 3 of the diffraction grating. It is known that when the angle formed by the angle K/2+θ, the wavelength λ of the emitted light is proportional to the sine of the angle θ, as shown in Equation 1.

[0015]

[Math 1]

[0016] d: lattice constant, m: diffraction order, K: opening angle λ: wavelength, θ: rotation angle number When 1 is transformed, the equation 2 is obtained.

[0017]

[Math 2]

If grooves are provided on the circumferential surface of the rotating drum shown in FIG. 1 at angles corresponding to equal wavelength intervals using Equation 2, the amount of scanning wavelength can be determined by counting the grooves.

FIG. 5 is a diagram showing an example of the groove spacing of the wavelength indicator 1 of FIG. 1. If the longest wavelength handled by the spectrophotometer of the above embodiment is λmax, then from Equation 2, the rotation angle θmax at this time is
x is obtained.

[0020] From this, grooves are formed so as to correspond to equal wavelength intervals using the relationship of Equation 2 between the rotation angle of 0 degrees and θmax degrees. In addition, between θmax and 360 degrees, the groove spacing becomes narrower as the rotation angle increases, so that when the diffraction grating is rotated more than 360 degrees, the groove spacing becomes narrower, and the groove spacing becomes 0 degrees at 360 degrees. Grooves are cut to match.

FIG. 6 shows an example in which a magnetic recording medium 35 is used as the wavelength indicator 1 of the above embodiment, a magnetic head 36 is used instead of the optical sensor, and a recording circuit 37 is further provided for recording signals on the recording medium. This is an example. The recording circuit 37
By providing this, calibration using actual light becomes easy and it becomes possible to set the wavelength with high accuracy.

[0022]

Effects of the Invention As described above, the diffraction grating driving device according to the present invention outputs pulses corresponding to the amount of scanning wavelength, and drives the diffraction grating based on these pulses. This method is easier to control than the case where pulses corresponding to the wavelength are used, and wavelength scanning with a constant wavelength scanning speed can be performed with a simple control system. Furthermore, since control can be simplified, wavelength scanning can be performed at higher speeds.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a spectrophotometer.

FIG. 3 is a diagram showing main parts of the optical system.

FIG. 4 is a diagram showing the effect of a diffraction grating.

FIG. 5 is a diagram showing an example of a wavelength indicating section.

FIG. 6 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

1...Wavelength indicator, 2...Optical sensor, 3...Motor, 4...
Rotating drum, 5... Diffraction grating, 6... Rotation direction detection circuit, 7
...Counter, 8...Motor drive circuit, 9...Control unit, 10...
Wavelength drive section, 11... Photo multiplier signal A/D conversion section, 12... Photo multiplier drive section, 13... Slit drive section, 14... Filter drive section, 15... Light source switching section, 16... D/A conversion for recorder 17...Recorder, 18...Data processing unit, 19...Printer, 20...Optical system, 21...Control bus, 22...Light source I, 23...Light source II,
24... Light source switching mechanism, 25... Incoming optical system, 26... Incoming slit, 27... Outgoing slit, 28... Filter, 2
9... Output optical system, 30... Photo multiplier, 31...
Rotation axis, 32... Incident light, 33... Perpendicular to the diffraction grating, 34...
Outgoing light, 35...Magnetic recording medium, 36...Magnetic head, 37
...recording circuit.

Claims (4)

[Claims] Claim 1: A diffraction grating is provided at the center of rotation on a rotating drum directly connected to the rotating shaft of a motor, a recording medium is provided on the circumferential surface of the rotating drum, and a sensor provided opposite to the recording medium is used as a reference for the diffraction grating. A diffraction grating drive device characterized by using an angle detection device that generates a signal based on a specific function according to a rotation angle from a position. 2. The diffraction grating driving device according to claim 1, further comprising a counter for generating pulses corresponding to a sine by the sensor and counting the pulses. 3. The diffraction grating driving device according to claim 1, characterized in that a rewritable recording medium is used. 4. The diffraction grating drive device according to claim 1, wherein a rotating disk is used instead of the rotating drum, and a recording medium is provided on the surface of the disk.