JPH07122594B2 - Spectrophotometer - Google Patents

Description

The present invention relates to a wavelength scanning mechanism of a spectrophotometer.

(Prior Art) In a conventional spectrophotometer, a so-called sine bar mechanism has been used as a mechanical wavelength scanning mechanism. This has the advantage that the relationship between the number of rotations of the motor and the wavelength of the emitted monochromatic light is linear and the wavelength can be easily calculated, but on the other hand, the mechanism is complicated, the number of parts is large, and the scanning speed is also limited. There was a drawback. In addition, recently, by using a microprocessor, the diffraction grating can be directly rotated by a pulse motor without using the sine bar mechanism, and the wavelength can be calculated by CP.
The method of calculation by U has become possible, but in order to obtain a certain level of wavelength accuracy, it is necessary to reduce the rotation angle of the diffraction grating per step of the pulse motor, which requires a reduction mechanism. Then, there was a problem that the structure became complicated in the end.

(Problems to be Solved by the Invention) In view of the above problems, it is an object of the present invention to provide a compact wavelength scanning mechanism of a spectrophotometer capable of high-speed inspection.

(Means for Solving the Problems) In order to achieve the above object, the spectrophotometer according to the present invention has a recording medium 3 provided on the peripheral surface of a rotary drum 2 directly connected to the rotary shaft of a subtotal DC servomotor. A sensor 4 attached to the recording medium 3 generates a rotation position detecting pulse, and a diffraction grating 6 is arranged on the rotating drum 3 at the rotation center position.
A counter 12 that counts the pulses and an arithmetic circuit 13 that calculates the wavelength of the emitted light from the counter output are provided.

(Operation) Since a so-called encoder direct-coupling type DC servomotor is used as the rotating mechanism of the diffraction grating, the resolution can be sufficiently increased without using the reduction mechanism, and the rotational position detection pulse from the encoder can be wavelength-converted. Can be used to calculate
Further, since the sine bar mechanism and the speed reduction mechanism are not necessary, the device can be downsized, and the noise and vibration can be reduced and the reliability can be improved.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which a flat type DC servomotor is fixed to the back surface of a motor control printed circuit board 1 and a motor shaft protruding through the printed circuit board 1 to the upper surface. A rotary drum 2 is coupled to the rotary drum 2, and a rotary encoder is provided on the peripheral surface of the rotary drum 2 and has a magnetic recording medium 3 on which pulse signals are recorded at a fine pitch, and a magnetic sensor 4 provided opposite to the magnetic recording medium 3. , And a comparator circuit 5 that generates a two-phase pulse output for detecting the rotation position and the rotation direction. The diffraction grating 6 is mounted on the rotary drum 2 at the center of rotation, and the diffraction grating 6 is rotationally driven at a constant speed by a motor,
The wavelength of the monochromatic light that enters through the entrance slit 7 and exits through the exit slit 8 is scanned.

FIG. 2 shows a motor control circuit, which has an encoder E.
The pulse output from the rotation direction detection circuit 11 and the counter
The pulse is added to the counter 12, and the counter 12 adds or subtracts the pulse according to the output from the rotation direction detection circuit 11, and inputs the output to the arithmetic circuit 13. The arithmetic circuit 13 detects the current rotational position and direction from the outputs of the rotation direction detection circuit 11 and the counter 12, and sends a control signal to the motor drive circuit 15 according to a command from the operation circuit 14 to control the motor M, From the current rotation angle, the grating constant of the diffraction grating, and the geometrical arrangement of both slits, calculate the wavelength of the emitted monochromatic light,
It is displayed on the display circuit 16 and stored in the storage circuit 17.

FIG. 3 shows a method of determining the wavelength by the above-mentioned configuration, and the wavelength scanning is performed by rotating the motor at a constant speed.
The 0th-order light λ _{0, which} is the reference of the emitted light, has a sufficient intensity as compared with other diffracted light, and therefore can be detected by monitoring the emitted light with a photodetector. Further, a gap is provided on the magnetic recording surface as a reference point of the pulse from the encoder, and the pulse is counted from the end point t _{0 of the} gap. If the rotation device for the 0th-order light λ ₀ is set as the count number N ₀ ,
Wavelength λ ₁ or λ corresponding to the count number N ₁ or N _2
2 can be calculated by the arithmetic circuit 13.

(Effects of the Invention) As described above, the spectrophotometer according to the present invention rotatably drives the diffraction grating by the direct current servomotor of the encoder direct connection type,
As the encoder, the one with the pulse signal recorded at a fine pitch such as a magnetic recording medium is attached to the peripheral side surface of the drum on which the diffraction grating is mounted, so the output pulse of the encoder is counted by counting the output pulse of the encoder. Since the wavelength is calculated, the resolution can be sufficiently increased without using a reduction mechanism compared to the conventional method using a step motor, and the output pulse from the encoder can be directly converted to the wavelength. Since it can be used for calculation, the circuit can be simplified and the calculation speed can be increased, and since the sine bar mechanism and the speed reduction mechanism are unnecessary, the device can be downsized and noise and vibration can be reduced. There is an advantage.

In the present embodiment, the magnetic encoder is used as the rotary encoder, but if the pulse encoder can record and read the pulse signal at a fine pitch similar to that of the magnetic encoder, for example, a photoelectric encoder is used. You can also

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a main part circuit diagram of the above, and FIG. 3 is an operation explanatory diagram of the same. 1 ... Printed circuit board, 2 ... Rotating drum, 3 ... Recording medium, 4 ... Sensor, 5 ... Comparator, 6 ... Diffraction grating, 7 ... Incident slit, 8 ... Exit slit.

Claims (1)

[Claims] 1. A recording medium capable of recording pulse signals at a fine pitch, such as a magnetic recording medium, is provided on the circumferential side surface of a rotary drum directly connected to the rotary shaft of a small DC sabot motor, A sensor provided in opposition to this recording medium generates a rotational position detecting pulse by reading the recorded pulse signal, arranges a diffraction grating at the rotational center position on the rotating drum, and counts the pulse. A spectrophotometer comprising a counter and an arithmetic circuit that calculates the wavelength of emitted light from the output of the counter.