DD228053A1 - PROCESS FOR PHOTOELECTRIC ADJUSTMENT OF EDGES AND STRUCTURES - Google Patents

Abstract

The invention relates to a method for probing edges and structures by means of circular circular ring detectors with the aim of increasing the measurement accuracy. The main task is to achieve an improved evaluation of the measurement signals during the measurement processes. From the electrical signals generated by the detectors are generated by subtraction measurement signals that are further processed in an evaluation or in a computer. From the zero pulses of these measurement signals, the position of the edge or structure is determined. Very flat measurement signals are not forwarded for processing.

Description

Title:

Method for the photoelectric probing of edges and structures

Field of application of the invention

The invention relates to a method for the photoelectric probing of edges and structures by means of circular-circular ring detectors, in particular of object edges in measurements in transmitted and reflected light.

Characteristic of the known technical solutions

The field of application of objectified optoelectronic probing of test objects has a number of different sensors which are used to solve specific measuring problems in manufacturing and length measuring technology.

From DE-OS 31 43 948 a photoelectric method and a receiver arrangement for detecting the position of edge-shaped measuring structures is known in which circular Kreiring detectors are applied «These consist of a circular inner and an annular outer detector, wherein the photosensitive surfaces are isolated from each other and advantageously have the same surface area.- The measuring signal

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is formed by a differential circuit of both receiver surfaces.

It is a disadvantage of this known method that at an acute angle between the scanning direction and the position of the structural edge or line structure the geometrically physical influencing variables cause impermissible exceedances of the measurement uncertainty, because the obtained measuring signals are very flat, ie with a small pitch In the most unfavorable case, for example if the structure edge or line structure no longer fully exceeds the detector surface η during the probing, no difference signal (measuring signal) is produced which has a zero crossing. In this case it is not possible to determine the structure of the structure «

Object of the invention

It is an object of the invention to overcome this deficiency of the state of the art and to increase the probing and measuring accuracy.

Essence of the invention

The invention has for its object to provide a method for photoelectric probing of edges and structures, which increases the measurement accuracy and the measurement uncertainty can be improved by improved evaluation of the measurement signals of photoelectric detectors in manual and especially in automatic, computer-aided measurement processes.

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According to the invention, this object is achieved in a method for photoelectrical scanning of edges and structures by means of movable relative to the edges or structures circular-circular detectors, wherein from the electrical signals supplied by the detectors by summing or subtraction measurement signals are formed whose zero crossings the location of the determined edge or structure along a direction in the direction of displacement of the detector coordinate, achieved in that at least two thresholds Ui U ₂ (amplitude values) of the measurement signal are determined that the displacement of the detectors along the coordinate by means of a Wegoder timer in distance or Zeitincremente the efficiency of these increments along this coordinate χ has an increasing or decreasing tendency x .. % * X ₂ ic ··· ic ^x i>"fc-i ^ * 2 ^ 3 ^ ^ i ^{that the} coordinate values x * ¹ »^ ₂ ¹ belonging to these threshold values U-; U ₂ t ₂ ; t ₂ existing number Έ of the distance or time increments is determined by means of a counter, and that the determined number IT of these increments is compared with a predetermined number of increments IJ in an evaluation unit or in a computer, such that when N> N a transfer of the zero pulses of the measuring signal into the evaluation unit or into the computer does not take place «

For unambiguous probing in particular of structures, it is advantageous if the temporally successive zero pulses of the measuring signal generated during the passing over of the edge or structure are compared with the coordinate values belonging to them, such that if two coordinate values of successive coordinate values deviate from one another the

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associated with them, rising or falling tendency does not take over the Hullimpulse in the evaluation unit or in the computer or the relative movement between the detectors and the edge or structure is interrupted.

When using the method according to the invention for determining the position of edges and structures, uncertainties and inaccuracies are largely avoided, since unsafe or unusable for the evaluation measurement signals are avoided or do not get to further processing. These signals are supplied to the evaluation unit or the computer only from a previously defined steepness of their amplitude profile.

embodiment

The invention will be explained in more detail with reference to embodiments. In the drawing, Pig. 1 schematically shows the conditions in the probing

an edge, Pig. 2 schematically shows the conditions when probing a structure in the form of a narrow rectangle

and Pig. 3 in enlarged Porm the waveform according to Pig. 1 with indication of the threshold values U-; U ₂ and the increments.

Pig.1 shows a circular photoelectric circular detector with the detector surfaces T and 2 for scanning an edge 3, wherein the detector and the edge 3 relative to each other along a coordinate χ are displaced. In the shift, z. B. the edge 3 across the detector from the position I to the position II

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From each detector surface, electrical signals are generated from which, by subtraction, a measurement signal A whose course in Pig. 1 is formed. The zero crossing xp ß ^ ^ the location of the fingered edge 3 and is determined by means of an evaluation or a computer (not shown) · This procedure of evaluation of the measurement signal A prepares at perpendicular to the edge 3 extending Antastrichtung no difficulties, because of the large slope the curve of the measuring signal A, the zero crossing at x. ^ is reliably determined. The measurement signal B (shown in dashed lines) results when an edge 4 at an angle to the scanning direction is moved over the surfaces 1 and 2 of the detector from location III to location IV. The measuring signal B is substantially flatter, and from a certain minimum slope a reliable detection of the zero pulse at the zero crossing Xg _{2 is} no longer possible. In order to avoid that unsafe zero pulses are fed to the evaluation unit or the computer, at least two threshold values IL; U ₂ (amplitude values) of the measurement signals A; B (Pig. 3), and the displacement path of the detector along the coordinate χ is divided into path or time increments by means of an unillustrated path or timer. In Pig. 3, these increments are generally labeled N and corresponding indices. These increments N are machine coordinates x. associated with a significance of increasing or decreasing tendency, namely according to Pig. 1 is x.- ^ x. ₂ ^ ^x ai ^{0 <^ he} ei Ze it increments η ^ A 1 ^ ^ 4.2 £ ^ A3 * ³ ^ Enso applies ^ - ^ ^the zero crossings of the signal curves C and D (Pig. 2) along the coordinate axis χ

^X C1 £ ^X C2 $ ^X C3 $ ^X C4 ^And

^X D2

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The coordinates ^{χ |} between the values belonging to the threshold values η U. and Up ai ^{and x} 'a2 ^{tzw # χ1} Β1 ^{and zf} B2 ^{voriia! :: L} "dene number of increments H. or E ₀ (Pig * 3) is determined by means of a counter (not shown), and the number Έ and E _n is in the evaluation unit or

A ο

in the computer with a predetermined number of increments Ή compared «Is the number of increments H,> IT.

In the case of flat curves of the pail, there is no assumption of the zero pulses of the measurement signal in the evaluation unit or in the computer. In FIG. 3, these relationships are shown by the example of curves A and B and represented by the inequality Ng> 1 "> U. marked "

In Fig. 2 the course of measurement signals G and D is shown, when passing over the surfaces 1 and 2 by. Structures 5 and 6 different inclination to the coordinate χ (shift direction) are formed by subtraction of the signals supplied by the detector surface η. This produces the measuring signal G z. B. in the movement of the structure 5 from the position V in the position VI. Analogously, the measurement signal D is formed during the displacement of the structure 6 from the position VII to the position VIII. In order to determine a defined position of the structure, eg a stroke of a division, the pulses are applied to the evaluation unit or to the computer lulldurchgängen x ~ ^, · .., Xq, or x ^ ^, ··, xq. the measured signals G and D evaluated, in each case the four.UuIldurchgänge a measurement signal detected must be. Again, at least two thresholds U ₁ ; U ₂ fixed and the displacement of the detector along the coordinate χ is divided into increments H, which are counted. Again, as described in Figs. 1 and 3, when the number N of increments between the,

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Thresholds U ..; If the associated coordinates χ are greater than a predetermined number U of the increments, the transfer of the hulliin pulses into the evaluation unit is prevented.

In order to ensure that all zero-crossing points of the measuring signal are also detected in the correct order, the rising or falling tendency of the significance of the increments or coordinates in the x-direction in the evaluation unit or the computer is evaluated. The position of the structure is determined from the four zero pulses.

Instead of a fixed number Ή of increments, an increase ^ p may be set, · which (with the increases Cp ^ and (p _B Pig x 1 and 3) are compared. The increases Cp. And Cp ^ are then respectively by the evaluation unit · Calculated by the computer from the thresholds U ₁ , U ₂ and the corresponding increments 35L and Έ-ο If the determined increase, ζ. Β. ^ Ώ »is smaller than the increase ^ ₀ , the hull impulses are not transferred to the computer.

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Claims (2)

P at e nt to pr pr oy 1. A method for fotoe.lektrischen palpation of edges and structures by means of relative to the edges or structures of movable Krels-circular ring detectors, _ being formed from the, supplied by the detectors electrical signals by summing or subtraction measurement signals whose Zulldurchgänge the place determine the probed edge or structure along a coordinate running in the displacement direction of the detector, characterized that at least two thresholds XL ·; U ₂ (amplitude values) of the measurement signal., That the displacement of der'Detektoren along the coordinate by means of a path or timer in path or time increments is divided, the valence of these increments along this coordinate χ an increasing or decreasing tendency x. ^ x -> ^ ··· ^ x .; t .. ^ t ₂ ^ ♦ ·· ^^ i have that between the to these thresholds U ..; U ₂ associated coordinate values x * -; x'p or t-; t ₂ existing number 1 of the distance or time increments is determined by means of a counter, and that the determined number Έ of these increments with a predetermined number of increments Ii in an evaluation or in a computer is compared, such that at Έ >> Έ a takeover of the zero pulses of the measuring signal in the evaluation or in the computer does not take place. 2. The method according to claim T, characterized in that during the Überfahre ns the edge or 4740 Structure are generated by the detectors generated, successive zero pulses of the measured signal with their belonging coordinate values, such that when two deviating in the direction of coordinate values from their associated rising or falling tendency, a transfer of zero pulses in the evaluation or in the computer not takes place ", the relative movement between the detectors and the edge or structure is interrupted. For this 2 sheets of drawings 4740