JPS61108951A - X-ray goniometer - Google Patents

Abstract

PURPOSE:To obtain a goniometer having high accuracy without using a mechanism having high accuracy by driving a fine adjusting mechanism for correcting errors by a piezo-electric element. CONSTITUTION:A detector holding arm 7 of the goniometer is mechanismically connected to a theta driving shaft so that the arm rotates by as much as twice the rotating angle of the theta driving shaft. The lower part of a sample holder 2 is a circular cylindrical part 2a coaxial with the theta driving shaft 1 and is fitted to a cylindrical sleeve 4 in a tight slide fitting state. The holder 2 is made rotatable within the range of the elastic torsion of a leaf spring 3. A base 5 is formed to the sleeve 4 and the rear end of the piezo-electric element 6 having the expanding and contracting direction in the direction tangential to the outside surface of the part 2a in fixed and rear end thereof is kept always in slight contact with the attaching step surface 16 of the spring 3 of the sample holder. The piezo-electric element expands and presses further the one side of the spring 3 when a voltage is impressed thereto. The spring 3 is therefore twisted by receiving the torsional torque by which the holder 2 is rotated at a slight angle with the shaft 1 to correct the error of the rotating angle of the shaft 1.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to increasing the precision of goniometers used in X-ray diffraction devices and the like.

A goniometer of a conventional X-ray diffraction apparatus has a configuration as shown in FIG. In this figure, X is an X-ray, S is a sample, ] is an X-ray detector, and the goniometer rotates the detector 20 times with respect to the rotation angle θ of the sample S. In the conventional goniometer, The absolute angular accuracy of the sample rotation angle θ and the detector rotation angle 2θ is determined by the mechanical accuracy of the goniometer, and the angular accuracy is 0.01° to 0.005°.
, and those with higher precision were extremely expensive. In addition, the accuracy of the rotation angle is determined by how accurately the amount of movement due to the rotation of the outer circumference of the rotating part can be regulated.The accuracy of this amount of movement is determined by the dimensional accuracy of the mechanism, and with current processing technology, it is approximately ±2 μm. is easy. The accuracy of the pick rotation angle improves as the rotation radius increases if the machining accuracy is the same. This hinders the miniaturization of goniometers.

C. Problems to be solved by the invention From the above points, in order to improve the accuracy of the rotation angle of the goniometer, it is necessary to increase the processing accuracy of the mechanism, increase the radius of the goniometer, or use both. In any case, the present invention aims to improve the accuracy of the rotation angle of the goniometer from a completely different direction.

2. Means for solving the problem The present invention provides a method for solving problems by interposing piezoelectric drive means between the sample rotation axis and the sample and between the detector holding arm and the detector in the structure of a normal goniometer. The micro-movement of the sample and detector compensates for angular errors at designated positions of the sample and detector.

E. Function According to the above-mentioned configuration, it is sufficient for the goniometer itself to have normal accuracy.If the mechanical angular error at each angular position of the sample and detector is measured and memorized in advance, the memorized error can be used when using the goniometer. By applying a proportional voltage to the voltage drive means, errors in the angular position of the sample and detector can be compensated for, thus providing a highly accurate goniometer with a normally accurate mechanism.

Embodiment FIGS. 1 and 2 show the main parts of the mechanism of an embodiment of the present invention. FIG. 1 shows the connection between the central θ drive shaft and the sample holder in the goniometer. In this figure, 1 is the θ drive shaft, which is located at the center of the goniometer. 2 is a sample holder;
It is coaxially connected to the upper end of the θ drive shaft 1 via a leaf spring 3. The lower part of the sample holder 2 is a cylindrical part 2a coaxial with the θ drive shaft 1, and this part is fitted into the cylindrical sheath 4 fitted on the upper part of the θ drive shaft 1 in a tight sliding state. In the sample holder 2, the rear end of the piezoelectric element 6, which extends and contracts in the tangential direction within the range of the elastic twist of the plate spring 3, is fixed, and the tip of the piezoelectric element 6 is attached to the plate spring 3 mounting step surface 16 of the sample holder. It is designed to be in constant contact with a slight contact pressure. With this configuration, when a voltage is applied between both electrodes of the piezoelectric element 6, the element expands and further presses one side of the leaf spring 3. Therefore, the leaf spring 3 is twisted by the torsional shift torque, and the sample holder 2 is rotated by a small angle with respect to the θ drive shaft. This rotation compensates for the rotation angle error of the θ drive shaft 1.

The rotation angle error of the θ drive shaft 1 is set to a maximum of ±20'. If the angular deviation of the sample holder 20 with respect to the θ drive axis 1 when no voltage is applied to the piezoelectric element 6 is set to -20', the piezoelectric element will have a deviation of -20' to compensate for the angular error of ±20'. It is sufficient to apply positive and negative voltages for compensating for angular errors superimposed on a constant bias voltage for compensating for angular error. The reason for doing this is that if the operating direction of the piezoelectric element is opposite to the pushing and pulling depending on the positive or negative error, play will be generated at the connection point between the piezoelectric element and the leaf spring 3, and the error can be corrected accurately. This is because the effect of mechanical play is avoided by limiting the direction of action of the piezoelectric element to only pushing.

FIG. 2 shows the angular error compensation mechanism of the detector section.

In this embodiment, instead of moving the X-ray detection element itself relative to the detector holding arm, the slit in front of the detection element is slightly moved to compensate for angular errors. In this figure, 7 is a detector holding arm in the goniometer, and a line detection element 8 is attached to it.

Reference numeral 9 denotes a slit arranged in front of the detection element 8, and the right end of the piezoelectric element is fixed to the arm 7. With this configuration, the piezoelectric element 11 is always under tension by the spring 10 through the slit 9, and when a voltage is applied, its length is shortened and the slit 9 is pulled to the right in the figure.

The error in the 2θ rotation angle of the arm 7 is compensated by the movement of the slit due to the tension between the arm 7 and the slit. The radius of the goniometer, that is, the distance from the center of the goniometer to the slit 9, is 180 m.
m (this is the size of a normal goniometer), the amount of shortening of the piezoelectric element 11 (the amount of movement of the slit 9) corresponding to an angle of 1'' is approximately 6.8 μm.The amount of angle correction is ±20 μm.
'', the shortening amount of the piezoelectric element 11 to cover the entire range of this correction amount is equivalent to 40'', which is 36 μm.

FIG. 3 shows an example of an angular error correction circuit. P is a pulse motor that drives the θ drive shaft at the center of the goniometer, and drive pulses are supplied from a pulse generator G, and the drive pulses are counted by a counter C to detect the rotation angle θ of the θ drive shaft.

This detected rotation angle data is read into the computer CPH. The detector holding arm (not shown in FIG. 3) is mechanically connected to the θ drive shaft so that it rotates by twice the rotation angle of the θ drive shaft. Therefore, by reading the data of the rotation angle θ of the θ drive shaft, the nominal angular position of the detector holding arm can be found naturally. Ml and M2 are first and second memories, and Ml stores a relational table between θ and the error in the angular position of the θ drive shaft at the rotation angle detected by the count of the counter C of the θ drive shaft. . M2 stores a relational table between the nominal angular position of the detector holding arm and the error thereof (specifically, a relational table between the angular position of the θ drive shaft and the error between the angular position of the detector holding arm). be. When the CPU reads the count of the counter C, the CPU reads out the error data in the memo 17 Ml and M2 corresponding to the count value, converts it into a voltage signal via the DA converters DAI and DA2, and sends it to the piezoelectric element 6 via the amplifier. ,1
1 to correct errors in the angular position of the θ drive shaft and the detector holding arm. The error data stored in the memories M1 and M2 is obtained by actually driving the goniometer and actually measuring the error with respect to the nominal angular position of the θ drive axis and the detector holding arm.

In the above embodiment, both the sample holder and the detector slit are connected to the θ drive shaft or the detector arm via an elastic body, and there is no space between the sample holder or the detector slit and the θ drive shaft, etc. of each other. There is no mechanical play at all.

Effects The goniometer of the present invention has the above-described configuration, and the accuracy of the mechanical structure is sufficient to be on the same level as that of a conventional ordinary goniometer.The fine movement mechanism for correcting errors is driven by a piezoelectric element, so the piezoelectric element is essentially Since it is suitable for minute drive, the error correction mechanism can be made very easily, and as a result, an extremely high-precision goniometer can be achieved without using a particularly high-precision mechanism. As mentioned at the beginning, in order to improve the accuracy of a goniometer, the radius of the goniometer must be increased, but in the present invention, high accuracy is achieved through error correction, so the goniometer can be made smaller. Since high accuracy can be obtained even when using a high-speed goniometer, it is possible to downsize the reed and goniometer.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the θ drive shaft section in a goniometer according to an embodiment of the present invention, Fig. 2 is a perspective view of the detector holding arm near the detector mounting section, and Fig. 3 is an angular error of the same embodiment. FIG. 4 is a block diagram of the correction circuit, and FIG. 4 is a plan view of the X-ray goniometer. Agent: Patent Attorney Kosuke Figure 1

Claims (1)

[Claims] It consists of a θ drive shaft located at the center of the goniometer, and a detector holding arm that is linked to the θ drive shaft so that it rotates by an angle 2θ relative to the rotation of the coaxial angle θ. A sample holder is connected to the sample holder so as to be rotatable at a small angle relative to the same axis, a piezoelectric element is rotatably driven to rotate the holder relative to the θ drive axis, and a piezoelectric element is attached to the detector holding arm so as to be movable in the angular direction of the goniometer with respect to the arm. An X-ray goniometer comprising a detector and a piezoelectric element for driving the detector with respect to a detector holding arm, and applying an angular error correction voltage to both piezoelectric elements.