JPH01143920A - Spectrophotometric device - Google Patents

Abstract

PURPOSE:To improve S/N and to enable the collection of a large quantity of data at a high speed by storing the data subjected to A/D conversion by the timing signal synchronized with wavelength scanning into a RAM, etc. and computing the data of a desired wavelength as the integrated average value of the A/D converted data within a half-amplitude level. CONSTITUTION:The incident angle to the dispersion face of a dispersion element 3 is changed by rotation of said element and the photometric data is obtd. by the element 3 when said element receives the dispersed light. The rotation of the element 3 is controlled by a pulse meter 5 at this time. The timing signal corresponding to the rotating speed of the element 3 is determined according to the signal from a pulse motor control 11 and is outputted with the higher resolving power than the wavelength resolving power of the element 3. The detection signal of the light diffracted by the element 3 from a photodetector 16 is, thereupon, stored via a block 18, a sample-hold circuit 21, and an A/D converter 23 in a buffer 23 and a memory 25. A microcomputer 26 integrates and averages the data within the half-amplitude level of an arbitrary wavelength by the data of the memory 25.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a spectrophotometric device.

[Conventional technology]

When measuring weak light, conventional technology uses a combination of a photometer and a scanning device to obtain data by feeding the wavelength in steps, a structure in which the wavelength is sent at a constant speed and data is taken at temporal timing, and a structure in which the wavelength is kept constant. It was configured to send data at high speed and capture data using mechanical timing. Also,
When I tried to raise the S/N sufficiently, AC photometry was used and the measurement speed became slow.

[Problem that the invention seeks to solve]

In the conventional techniques as described above, the relationship between the data sampling speed and the S/N is determined, that is, the sampling speed is reduced and AC photometry is performed to improve the S/N. Then, when measuring on a line such as trench depth measurement, or simply measuring, it takes time and is not suitable for processing large amounts of data.The present invention solves these conventional problems. The purpose of this invention is to provide a spectrophotometric device that can improve the S/N ratio and collect a large amount of data at high speed.

[Means for solving problems]

In order to solve the above problems, in the present invention, data is A/D converted using a timing signal synchronized with wavelength scanning,
This A/D conversion data is made to correspond to the timing signal and R
After being stored in an AM or the like, data of a desired wavelength is calculated as an integrated average value of A/D conversion data within the wavelength resolution range of the desired wavelength, that is, within the half width.

[For production]

In the present invention, since the timing signal corresponds to the rotation angle (that is, wavelength data) of the dispersion element, sampling of A/D conversion data for wavelength can be performed even if the pulse corresponding to the scan signal has speed fluctuations (acceleration/deceleration). . In addition, data can be collected at high speed by performing A/D conversion using timing signals, so if A/D conversion is performed using an interrupt and the data is transferred using direct memory access (DMA), data collection can be done more efficiently in terms of time. I can do it. Furthermore, data is collected by performing A/D at a higher speed than the wavelength resolution, and the data at the desired wavelength is determined by the integrated average value of the data within the half width, so that the S/N ratio is improved.

(Example) Figure 1 shows an example of the present invention, and Figures 2 (a) and (b)
) is a graph explaining the operation of the embodiment of FIG.

Light entering the spectrometer from the entrance slit 1 is diffracted by the dispersion element 3 whose rotation is controlled by the pulse motor 5, exits the exit slit 2, and enters the light receiver 16. The rotation of the pulse motor 5 is controlled by a pulse motor control 11 via a driver 9. In addition, the light receiver 16 in FIG.
A photomultiplier tube is used. The voltage applied to the photomultiplier tube is controlled by a microcomputer (MPU) 26 via a high voltage data buffer 13, a D/A converter 14, and a high voltage unit 15.

The detection signal from the photoreceiver 16 passes through a preamplifier 17,
The signal reaches the selector switch 20 via a block 18 consisting of a variable gain amplifier and a low pass filter (LPF). The variable gain amplifier in block 18 optimizes the gain by S
/N, and low pass filter 1
8, when the frequency of the spectral curve is sufficiently low, the cutoff frequency is lowered and oversampled to improve the S/N. The changeover switch 2o is controlled by a microcomputer 26 via a control buffer 19. The position of the switch piece shown in FIG. 1 is the measurement state.

In the measurement state, the output signal of the block 18 enters the sample-and-hold circuit 21, and the sample-and-hold circuit <S/
H) The output signal of 21 is the A/D converter (ADC) 2.
After being converted into a digital signal in step 3, data buffer 2
4, it is temporarily stored. Sample hold circuit 21
The timing of hold by A/D converter 23, the timing of A/Di conversion by A/D converter 23, and the storage in data buffer 24 are determined by direct memory access (DMA) in response to commands from pulse motor control 11, which controls the drive of pulse motor 5. ) The timing of the sample hold and A/D conversion performed by the control logic 22 is determined by the direct memory access control logic 22 according to the signal from the pulse motor control 11 so that the timing of sample hold and A/D conversion is performed at a resolution greater than the wavelength resolution of the dispersion element 3. decide. As a result, as shown in the spectroscopic spectrum of FIG. 2(a), the spectroscopic spectrum P is a convolution of single wavelengths P1 to P with a half-value width Δλ corresponding to the wavelength resolution of the dispersive element 3. Therefore, as shown in Fig. 2(b), considering a certain single wavelength P, m points within its half width Δλ can be sampled and A/D converted, so the average value is By using data of a single wavelength P, the S/N can be increased.

On the other hand, in the initial setting state before measurement, the potentiometer 8 that monitors the absolute rotational position of the pulse motor 5
The microcomputer 26 switches the changeover switch 20 so that the output signal of the sample and hold circuit 21 is inputted to the sample and hold circuit 21. As a result, the signal from the potentiometer 8 is transmitted to the sample and hold circuit 21, the A/D converter 23,
The data is taken into the microcomputer 26 via the data buffer 24. The microcomputer 26 thereby controls the pulse motor control 1 via the buffer 12.
1, the first jlJ1 rotation direction command of the pulse motor 5 is given.

The limit 4 is used to initialize an arbitrary wavelength in 50 nm increments, and the position signal of the potentiometer 8 and the timing signal sent out from the limit 4 are the origin point exit zinc 1.
It is input to 0. The origin detection logic 10 has limit 4
The pulse motor controller 11 is instructed to use the position signal of the potentiometer 8 when the timing signal is output from the controller as the origin. The microcomputer 26 receives this origin signal from the pulse motor control 11.

As described above, the pulse motor control 11 receives instructions from the microcomputer 26 via the control buffer 12, the origin position signal from the origin detection logic, and the mechanical limits of the short wavelength side and long wavelength side of the dispersive element 3. A limit signal from a limit switch 6.7 for limiting is inputted, and a control signal is outputted to the driver 9 and the direct memory access control logic 22, respectively.

The direct memory access control 27 is an IC for performing direct memory access on behalf of the microcomputer 26, and issues commands to the direct memory access control logic 22. When the microcomputer 26 releases the bus,
Direct memory access control 27 causes data in data buffer 24 to be transferred to memory (RAM) 25.

Next, the operation of one embodiment of the present invention will be briefly explained using the flowchart shown in FIG. FIG. 3 mainly describes the operation of the microcomputer 26.

Upon starting the measurement, the microcomputer 26 initializes the device (step 30) and controls the pulse motor control 1 via the control buffer 12.
1 to move the dispersion element 3 to the origin position (step 31).

As already mentioned, the movement to the origin position is performed in step 30.
Since the switch 20 is changed so that the potentiometer 8 is connected to the sample and hold circuit 21, the rotation direction of the pulse motor 5 is determined by the signal corresponding to the wavelength obtained through the buffer 24, and a command is issued based on this determination. I do.

Pulse motor control 11 Li, llj When detecting that the dispersion element 3 has come to the origin position set by the limit 4 by the signal from the X point detection logic 10, this is communicated to the microcomputer 26, so the microcomputer 26 , a command is given to the pulse motor control 11 via the control buffer 12 to start scanning within the measurement wavelength range specified by the operator from a keyboard (not shown), etc., and the switch 20 is switched to block the block. 18 is input to the sample hold circuit 21 (step 32).

Pulse motor 5 by pulse motor control 11
is rotating at a constant speed from one side of the measurement wavelength range to the other, and while the pulse motor 5 has not reached the other side of the measurement wavelength range (steps 33 and 34), the dynamic memory access control 27 controls the dynamic memory access control. Controls logic 22. As a result, the dynamic memory access control logic 22:
The sample hole g circuit 2 L is
The A/D converter 23 is driven and data is temporarily stored in the data buffer 24 (steps 330, 331, and 332).

And dynamic memory access control 27
In step 333), it is determined whether the bus of the microcomputer 26 is free, and if the bus is free,
The data in the buffer 24 is transferred to the memory (RAM) 25 by dynamic memory access (step 33).
4.335).

The above operation is repeated while the pulse motor 5 is rotating, and when the pulse motor 5 stops, the wavelength scan is completed.
Step 6 compares the data in the memory 25 to determine whether the gain is appropriate (step 35). If the gain is inappropriate, step 6 sets the gain for the block day to the optimum value via the buffer 19. 36) A command is given to the Hals motor control 11 to start the pulse motor 5 again (step 37).

During the execution of steps 35 and 36, the pulse motor control 11 has set the dispersive element 3 to one side of the wavelength measurement range, so that the pulse motor is operated in the following steps 38 and 36.
At step 39, the dispersive element 3 is rotationally controlled within exactly the same wavelength range as at step 33.34.

Also, during the rotation of the pulse motor 5, the dynamic memory access 27 is performed in steps 330.331.332.3.
33. Performs the same operation as 334.335.

When the pulse motor stops (step 39), the microcomputer 26 integrates and averages the data within the half-width of an arbitrary wavelength using the data in the memory 25, and displays it (steps 40, 41).

〔Effect of the invention〕

As described above, according to the present invention, since data is acquired at high speed in proportion to the wavelength axis, speeded-up measurement is possible. Further, although the S/N usually deteriorates due to speed amplification, since sampling is performed m times within the half width of a single wavelength, the S/N improves by that amount.

Further, even if fluctuations occur in the rotation of the motor, the data corresponding to the wavelength is accurate because it is synchronized at a finer cycle than the wavelength resolution.

Therefore, a measuring device that measures depth using white interference such as a trench groove can perform measurements with good S/N and at high speed.

Furthermore, as in the embodiment, by dynamic memory access transfer of data, faster measurement can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an apparatus according to the invention. 2A and 2B are graphs for explaining how to obtain data in an embodiment of the device according to the present invention, and FIG. 3 is a flowchart for explaining the circuit operation of FIG. 1.
It is. [Explanation of symbols of main parts] 3... Dispersion element, 5... Pulse motor, 9... Driver, 11... Pulse motor control, 12... Buffer, 16... Light receiver, 21 ...Sample hold, 22...DMA control logic, 23...A
/D converter, 24...Buffer, 25...RAM. 26...MPU. 27...DMA control. Applicant Nippon Kogaku Kogyo Co., Ltd.

Claims (1)

[Scope of Claims] A spectrophotometric device that changes the angle of incidence of the dispersive element with respect to the dispersion surface by rotating the dispersive element, and obtains photometric data by receiving dispersed light from the dispersive element, comprising: a rotation drive means for continuously rotating the dispersion element; a timing signal output means for outputting a timing signal corresponding to the rotation angle of the dispersion element with a resolution greater than the wavelength resolution of the dispersion element; a light receiving means for converting a photoelectric conversion signal of dispersed light by the element into a digital signal; a storage means for storing the output signal of the light receiving means in correspondence with the timing signal; and a storage means for storing the digital data in the storage means at a predetermined wavelength. 1. A spectrophotometer, comprising: arithmetic means for integrating and averaging within each wavelength resolution range and using this as photometric data for the corresponding wavelength.