JPS61180104A - Measuring instrument for position displacement - Google Patents

Abstract

PURPOSE:To detect the direction of the displacement of a body to be measured even when the setting position of the object body is not within a measurement range by extending the photodetection surface of a PSD (position detecting photodiode) further form an electrode as the measurement range. CONSTITUTION:Photodetection surface S1 and S2 are provided extending to outside electrodes 4 and 5 fitted on the photodetection surface 2 of a PSD17, which is mounted on a position displacement measuring device. When reflected light 13b from the object 14 is at the center point of the PSD17, nearly equal currents i1 and i2 flow to the electrodes 4 and 5. If the reflected light 13b is off the point O, the currents i1 and i'd2 increase and decrease in the opposite directions according to a position (y) shifting from the point O. When the reflected light 13b further shifts and reaches the photodetection surface S1, the current i1 is ceased. When the currents i1 and i2 are inputted to a computing element 18 and a positive and a negative full-scale output voltage are obtained even if the reflected light 13b strike the photodetection surfaces S1 and S2, so that the direction of the displacement of the reflected light 13b is detected.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention irradiates a light beam onto an object to be measured, and uses the reflected light to measure the position and displacement of the object. The present invention relates to a position displacement measuring device that can calculate shapes and dimensions.

[Conventional technology]

Figure 1 shows the main parts of the position displacement measuring device.
11 is a light source that outputs a laser beam or the like; 12 is an irradiation lens; 13a is irradiation light that is focused on the object to be measured 14;
16 is a displacement detector and is a position detection photodiode 17.b which is a displacement detector and is irradiated with the reflected light 13b. and an arithmetic unit 18 for the detected signal.

FIG. 2 shows a conventional position detection photodiode used in such a position displacement measuring device.
This is a schematic diagram of the structure of on S sensitive device (hereinafter referred to as PSD), where 1 is n
1' is a thin semiconductor insulating layer (one layer), 2 is a p-type semiconductor surface layer, and 3 is an electrode provided on the n layer of the n-type high-resistance semiconductor substrate 1. , 5 are electrodes provided at both ends of the p-type semiconductor surface layer 2.

A diode with such a PIN structure is connected to a DC power source 6. as shown in the figure. When the load resistors 7 and 8 are connected and the p-type semiconductor surface layer 2 is irradiated with a spot-shaped light beam L, the current generated by the photoelectric effect is shunted in the load resistors 7 and 8 by the surface resistance of the semiconductor surface layer 2. Photocurrent 11
and 12 are known to flow.

This photocurrent i1. When the load resistances 7 and 8 are sufficiently smaller than the surface resistance of the semiconductor surface layer 2, and the position of the light beam L is displaced from the center 0 by y, the photocurrent i1 flows through the load resistance 7.8. As shown in FIG. 3(a), when y=Q, 12 becomes 1l=i2, and increases and decreases in opposite directions when moving away from the center O. Therefore,
The distance @y that the light beam L is displaced from the center ○ is shown in Figure 3 (b
) as shown by the solid line, Y=K・, , (where K is a constant of proportionality) 11 +
It can be calculated by t2.

By the way, in the above-mentioned position displacement measuring device shown in FIG.
Since the imaging point of the reflected light 13b irradiated on the object 17 also moves as shown by the dotted line, calculating the moved position y of this imaging point from the values of the photocurrents i+ and i2 yields the displacement of the object 14 or Its shape etc. can be measured.

[Problem that the invention seeks to solve]

However, the value of the displaced position y is equal to the photocurrent i1
．． i2 can be calculated in the measurement range where i2 is obtained, that is, in the set position of the object to be measured 14 such that the reflected light 13b irradiates the semiconductor surface layer 2 of the PSD 17. When the position of the object under test 14 is completely out of the measurement range, that is, when the position of the object under test 14 is outside the measurement range, the current due to dark current and thermal noise becomes unstable as shown by the dotted line, and the position of the object under test 14 becomes unstable. Output independent of position occurs.

When the imaging spot formed by the light-receiving lens comes off the semiconductor surface layer 2, that is, when the position of the object to be measured 14 goes out of the measurement range, an indefinite output is generated, and this irregular output causes the position of the object to be measured 14 to be within the measurement range. There are many cases where it is difficult to judge whether the target is correct or not. Especially in high-precision equipment with high light receiving magnification, the object to be measured 1 in space is located several mm away.
4 to a measurement range of about 0.1 mm, the object to be measured 1
When setting the object to be measured 14 in a position displacement measuring device, it becomes extremely difficult to determine its initial position, and at the same time, there is a problem in that it is not possible to configure a servo circuit when automatically setting the settings of the object to be measured 14. there were.

This invention was made in view of these points, and
The present invention provides a position displacement measuring device that is capable of detecting the direction in which an object to be measured is set even if the set position of the object is not within the measurement range by improving the light receiving surface of the SD.

〔Example〕

Figure 4 shows a PS that can be adopted in the position displacement measuring device of this invention.
D (a photodiode for position detection), and the structures 1 to 8 are the same as those in FIG. 2. However, the PS attached to one position displacement measurement bag of this invention
In D, two light-receiving surfaces sl and s2 are provided extending outward from the electrode 4.5 attached to the p-type semiconductor surface layer 2 serving as the light-receiving surface.

Next, a case where the reflected light 13b is incident on the PSD will be described.

As described above, when the reflected light 13b is at the center point 0 of the PSD, substantially the same photocurrent 11+12 flows through the two electrodes provided on the light receiving surface. Also, when the position of this reflected light is displaced and comes to a position away from the center point 0, the fifth
As shown in Figure (a), the two photocurrents 11+12 increase and decrease in opposite directions depending on the position y shifted from the center.

Then, when the deviation of the reflected light 13b becomes even larger and reaches the light receiving surface S1, which is the extension described above, the reflected light 13b
All of the photocurrent due to b flows into the electrode 5, and the photocurrent 12, that is, the current of the electrode 4 becomes O. Conversely, the light receiving surface S extended
When the reflected light 13b shifts toward 2, the photocurrent 11 becomes O
becomes.

Therefore, as shown in FIG. 5(b), the output of the arithmetic unit 18 is the same as before within the normal light-receiving surface that is the measurement range, y=
At the same time, the position 11 +12 of the incident light is detected and the extended light receiving surface S l + S
2, full-scale output voltages +V and -■ can also be obtained. Therefore, it is possible to know in which direction the reflected light 13b is displaced from the normal light receiving surface.
Unlike the PSD shown in FIG. 2 described above, the detected value does not show indeterminacy.

There is a problem when the reflected light 13b is incident on the electrodes 4 and 5, but if the electrodes 4 and 5 are made thin or thin, or if the electrode material is made of transparent and conductive tin oxide, etc. In this respect, the voltage +V corresponding to full scale,
-V is obtained.

FIGS. 6(a) and 6(b) show the shape of another PSD installed in the position displacement measuring device of the present invention, in which the light receiving surface S11 is extended compared to that of FIG. The width of Si2 is narrowed.

If the extended light receiving surface S11, 312 can receive even a portion of the reflected light 13b, the calculation output can be maintained at the full scale value, so there is no problem even if the light receiving surface is narrowed.

With such a structure, 1) Extended light receiving surface SI1. S12 can prevent the junction capacitance from increasing and the response from worsening.

2) Since the increased leakage current can be reduced by extending the light receiving surfaces Sll and S12, the detected value S/
N increases.

There are advantages such as

Note that the extended light receiving surface S1. S2 (S11, 31
The layer resistance in the P-type semiconductor region of 2) does not need to be particularly uniform, and even if the sensitivity of photoelectric conversion is low, the operation and effect will not be affected.

As can be understood from the above explanation, in the position displacement measuring device of the present invention, the light receiving surface of the PSD is the electrode 4 that is the measurement range.
．． 5 further outward to widen the capturing range of the reflected light, so the position of the object to be measured set in the position displacement measuring device can be detected over a wider range than with conventional position displacement measuring devices. Even if the position of the center of the object to be measured is slightly shifted, the direction of the shift can be detected using the calculated value of the photocurrent obtained from the PSD.

〔Effect of the invention〕

As explained above, the position displacement measuring device of the present invention has the following features:
This has the effect that the set position of the object to be measured can be captured over an extremely wide range. In particular, with a high-precision device with a high light-receiving magnification, it is necessary to measure a positional displacement of about 0.1 mm at a spatial distance of several mm, but in this case as well, alignment between the position displacement measuring device and the object to be measured is necessary. This has the advantage of making it easier.

Further, there is an effect that a servo system for automatically setting the object to be measured at the initial position can be easily configured.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of a position displacement measurement device that measures the shape of an object from its position displacement, Figure 2 is a structural diagram of a position detection diode (PSD), and Figures 3 (a) and (b). ) is P
A characteristic diagram of the photocurrent of the SD, Fig. 4 is a structural diagram of the PSD adopted in the position displacement measuring device of the present invention, and Fig. 5 is a characteristic diagram of the photocurrent detected by the position displacement measuring device of the present invention and calculations. Figures 6(a) and 6(b) are structural diagrams showing other embodiments of the PSIM. In the figure, 11 is a light source, 12 is an irradiation lens, 13a is irradiation light, 13b is reflected light, 14 is an object to be measured, ]5 is a focusing lens, 17 is a photodiode, and 18 is a computing unit. Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] A photodiode for position detection using a condensing lens that irradiates a light beam to generate a bright spot on the surface of the object to be measured and captures the reflected light from the bright spot at a constant angle with respect to the irradiation direction of the light beam. In a position displacement detection device that forms an image on the object to be measured and detects the position displacement of the object in a non-contact manner; the photodiode for position detection has a light receiving surface for position detection that receives the reflected light; two electrodes disposed on both sides of the surface for detecting the position of the reflected light; and an overrange region extending further outward from the two electrodes in which the reflected light moves outside the light receiving surface. A position displacement measuring device characterized by comprising two light receiving surfaces for detection.