JPH07101169B2 - Optical extensometer - Google Patents

Description

The present invention relates to an optical extensometer for measuring the elongation amount of a test piece and the like.

B. Prior Art FIG. 2 shows a light source 21 for illumination and a CCD 22 which is a photoelectric conversion element.
1 shows a conventional optical extensometer 20 that includes an imaging optical system 23 and that detects a mark mark MK of a test piece TP by a CCD 22. Here, a signal indicating the image forming position of the marked line mark on the CCD 22 is input to the control circuit 31, and the control circuit 31 controls the optical camera 20 by the pulse motor 33 for tracking control. That is,
The optical camera 20 is drive-controlled by the pulse motor 33 via the motor drive circuit 32 so that the image formation position is always the same position on the CCD 22. The control circuit 31 is a pulse motor.
The display drive circuit calculates the amount of expansion based on the number of 33 pulses.
It is displayed on the display unit 35 via 34. In this way, the camera 20 is made to follow the elongation when testing a material such as rubber in which the displacement amount of the test piece TP is larger than the measurement range of the CCD 20. When the elastic coefficient is high and the displacement is small like a metal material, that is, when the displacement is smaller than the measurement range of the CCD 20, the camera 20 does not need to follow the displacement.

C. Problem to be Solved by the Invention However, in the optical extensometer using the conventional CCD, the resolution of the CCD is low, and thus the displacement measurement accuracy of a material having a high elastic coefficient such as a metal material and a small displacement amount is low. However, there is a problem that it cannot be measured substantially. In addition, in the conventional extensometer, one pair is required for each pair of marked marks, and compactification and cost reduction are not sufficient.

An object of the present invention is to provide an optical extensometer which can accurately measure the displacement of a material having a high elastic coefficient and a small amount of deformation and which can be easily downsized.

D. Means for Solving the Problems The invention according to the present invention is applied to an optical extensometer that measures a displacement amount of a sample by receiving light beams reflected by a pair of reference points on a measurement target with a camera. . Then, the above-mentioned objects are a light source that illuminates a reference point on a measurement target, a pair of imaging optical systems that respectively image a pair of light fluxes on a predetermined focal plane, and a pair of light fluxes that are arranged on a predetermined focal plane. A single semiconductor position detector that receives the light and outputs a signal according to the light receiving position, and the output voltage of the semiconductor position detector with respect to the positional relationship of a pair of incident light beams on the semiconductor position detector, which is stored in advance. This is achieved by including a calculation means for calculating the displacement amount from the output voltage of the semiconductor position detector based on the reference data.

E. Action Each light beam of the pair of reference points forms an image on a single semiconductor position detector, and the image formation position changes according to the deformation of the measurement target. The output signal of the semiconductor position detector also changes in accordance with such a change in the image forming position. Reference data representing the output voltage of the semiconductor position detector with respect to the positional relationship between the pair of incident light beams on the semiconductor position detector is stored in advance, and the displacement amount is calculated by the calculating means from the output signal of the semiconductor position detector and the reference data. Is calculated.

F. Example One example of the present invention will be described based on FIG. 1 showing the configuration of the optical extensometer according to the present invention.

Reference numeral 110 denotes an optical extensometer, which is installed so as to face a pair of mark marks MKU and MKL provided on the test piece TP.
The extensometer 110 includes light sources 111U and 111L (halogen lamps, semiconductor lasers, etc.) that irradiate light on the mark marks MKU and MKL, respectively, and high-brightness reflected light beams of the mark marks MKU and MKL on a predetermined focal plane. Imaging optical systems 112U and 112L for forming an image, a total reflection mirror 115 that guides a reflected light flux from the upper mark mark MKU to a semiconductor position detector 113 described later, and a lower mark mark.
A half mirror 116 that guides the reflected light flux from the MKL to the semiconductor position detector 113, and a semiconductor position detector that is arranged on a predetermined focal plane and receives the reflected light flux and outputs a voltage signal according to the light receiving position to both terminals ( PSD) 113, light sources 111U and 111L, imaging optical systems 112U and 112L, mirrors 115 and 116, and a semiconductor position detector 113, and a case 114 that is immovable with respect to the test piece TP during the test. .

The reflected light flux of the total reflection mirror 115 passes through the half mirror 116 and is incident on the semiconductor position detector 113. However, in the unloaded state, the reflected light fluxes of the upper and lower mark lines MKU and MKL detect the semiconductor position. The optical system is set so that the light enters the same point on the container 113. You may make it inject into different points.

Displacement detection by the optical extensometer configured as described above is performed as follows.

The light from the light sources 111U and 111L is applied as beam light onto the test piece TP. The optical axes of the imaging optical systems 112U and 112L are aligned with the respective mark marks MKU and MKL, and the high-brightness mark marks MKU and MKL pass through the imaging optical systems 112U and 112L and the mirrors 115 and 116. An image is formed on the semiconductor position detector 113. As is well known, a voltage signal corresponding to the light receiving position is taken out from both terminals of the semiconductor position detector 113.

Prior to the test, both terminal voltages of the semiconductor position detector 113 are read and stored. When a tensile load is applied to the test piece TP, the test piece TP extends, the respective mark marks MKU and MKL move, and the light receiving position on the semiconductor position detector 113 changes. Since the amount of elongation of the upper and lower marked lines is different, it is 2 on the semiconductor position detector 113.
The two light receiving positions are separated according to the amount of extension. The elongation amount of the test piece TP can be detected by measuring the fluctuation of the pair of terminal voltages of the semiconductor position detector 113 at that time.

That is, the amount of expansion can be obtained from the variation of the pair of terminal voltages as follows. First, a tensile load is applied to a reference test piece, and the elongation of the test piece is accurately detected by an extensometer separately provided. Then, this detected value is associated with both terminal voltages of the semiconductor position detector 113, and reference back data is created by this. The back data and the fluctuations of the pair of terminal voltages at the time of the test can be compared to obtain the elongation amount of the test piece.

Since the elastic modulus of the test piece TP is high and the amount of deformation is small, the luminous flux reflected from the marked line moves within the measurement range of the semiconductor position detector 113, and therefore it is necessary to follow the extensometer 110 according to the amount of displacement. The extensometer can be simplified. Further, since the resolution of the semiconductor position detector 113 is higher than that of the charge coupled photoelectric conversion element (CCD), the minute displacement amount can be measured with high accuracy.

In this embodiment, one semiconductor position detector 113 is sufficient,
We can provide a compact extensometer.

Further, in the above, the illumination light source is integrally provided on the extensometer side, but it may be provided separately from the extensometer case. Furthermore, a similar light source may be provided on a jig of a material testing machine such as a platen of a compression testing machine.

G. Effects of the Invention As described above, according to the present invention, the displacement amount of a test piece having a high elastic coefficient and a small displacement amount can be measured with high accuracy. Further, since the pair of light beams are guided onto the single semiconductor detector, a compact and inexpensive optical extensometer can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of an optical extensometer according to the present invention, and FIG. 2 is a diagram showing a conventional example. 110: Optical extensometer 111U, 111L: Light source 112U, 112L: Imaging optical system 113: Semiconductor position detector 114: Case 115: Total reflection mirror 116: Half mirror TP: Specimen MKU, MKL: Mark mark

Claims (1)

[Claims] 1. An optical extensometer for measuring the amount of displacement of a sample by receiving light beams reflected by a pair of reference points on a measurement target by a camera, and a light source for illuminating the reference point on the measurement target. A pair of imaging optical systems for respectively imaging the pair of light beams on a predetermined focal plane, and a single unit for receiving the pair of light beams arranged on the predetermined focal plane and outputting a signal according to the light receiving position. An output voltage of the semiconductor position detector based on one semiconductor position detector and prestored reference data representing an output voltage of the semiconductor position detector with respect to a positional relationship between a pair of incident light beams on the semiconductor position detector. An optical extensometer, comprising: a calculating unit that calculates a displacement amount from the optical extensometer.