SU1065683A1 - Method of checking complex-shaped part furnace form deviation - Google Patents

Abstract

THE METHOD OF CONTROL OF THE DEVIATION OF THE DETAIL SURFACE FORM DIFFICULT FOR1 # 1, which takes images of the topograms of the surfaces of the part being monitored and the reference, combines these images, takes the moire pattern in the form of moire strips, on the basis of which they judge. the deviation $ OPNEJ of the part surface, which is also distinguished by the fact that, in order to increase the accuracy and performance of control of parts with higher-order axially symmetric aspherical surfaces, the image surface topogram of the part surface is coaxially formed before the image alignment with its axis of symmetry, the interference field is directed to the surface of the part with an equidistant step of the strips at a given angle; the system is set relative to the axis of symmetry of the part to the angle determined by the resolution (Method (by the value of this system and the direction of the normal to the surface area of the part), with the maximum frequency of the observed interference fringes.

Description

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The invention relates to measurement technology and can be used for contactless control of the deviation of the surface shape of a complex shape, in particular, axisymmetric aspherical surfaces of the highest order, mainly optical.

The known method is to control the deviation of the surface shape of a complex shape, based on obtaining topographic maps of the surface relief by means of the IS. :: projection of interference fringes and allowing one to monitor the deviations of the shape in real time and with a given method of orientation of the object.

When this method is used to control axisymmetric aspherical surfaces of parts, the interference field reconstructed from a hologram is formed with an equidistant step of the strips, the step of the interference strips is measured relative to one base point located on the axis of rotation of the part, and the coordinates of the points of the controlled section a. surface

The disadvantage of the method based on direct measurement of the interference band on the controlled surface is the impossibility of increasing the accuracy and sensitivity of the control by reducing the pitch of the equidistant bands in the interference field. Reducing the stride pitch leads to accumulation of the total measurement of the measurement relative to the base point and unproductively long time measurement of the coordinates of the interference fringes. In addition, it is impossible to visually determine the localization of surface areas where there is a deviation

The closest to the invention to the technical essence is the method of controlling the deviation of the form of the surface of parts of complex shape, concluding that they receive images of the topogram of the surfaces of the controlled plane and the standard, combine isobrogens, get a moire pattern in the form of moire stripes, the court the deviation of the form surface of the part L2l.

The controlled object is placed in an interference field formed by coherent, almost parallel collimated beams and beams, the angle between KOTOptiM is 2/6.

First, a photograph of the topographic map of the reference surface is obtained and the angle t between the bisector and the surface plane of the object is measured. Then set in place of the reference object

controlled object and also receive a photograph of a topographic map. If the object under control is located at the same distance and has the same orientation as the reference one, then the distance between two adjacent dark moire lines will correspond to the deviation of the surface shape (in the direction perpendicular to the surface) equal to 2ti;

l

2fl:

Sir 0 SVn t cot 1)

where i. - the angle between the direction of observation (photographing) and the plane of the object surface. Images of topographic maps can be obtained on one negative or on two separate pictures 2.

The disadvantage of this method is the need for accurate installation of the test piece in place of the reference. To match the orientations of the controlled and reference parts, it is necessary to mark three base points on them. As already noted, the definition of bases on the test surface has an error due to the deviation of its shape. This reduces the accuracy of the alignment of parts, leads to distortion of the moire strips and ultimately reduces the accuracy of control. A second disadvantage of the method is the need to make photographs of contour maps of the reference and controlled parts, which is an unproductive and time consuming operation. This method does not allow controlling deviations of the shape of surfaces of complex shape, for example, high-order axisymmetric aspheric optical surfaces that do not have samples with reference surfaces due to the lack of certification methods with the required accuracy (less than ~ 5 µm).

The aim of the invention is to improve the accuracy and productivity of inspection of parts with high-order axially symmetric aspherical surfaces.

The goal is achieved by the fact that according to the method of controlling the deviation of the surface of parts of complex shapes, which consists in obtaining images of the topograms of the surfaces of the test piece of the standard, combine these images, get a moire pattern in the form of moire strips, according to the step of judging the deviation of the surface shape of the part, prior to combining the images of topograms, the optical axis of the system forming the image of the topogram of the workpiece surface, coaxially with its axis of symmetry, is directed to over spine part interference. a field with equidistant stripe pitch at a given angle sets the specified system relative to the axis of symmetry of the part at an angle determined by the resolution of this system and the direction normal to the part surface of the part with the maximum frequency of the observed interference fringes,

The drawing shows a schematic diagram of a device implementing the proposed method.

The device contains successively located laser 1, system 2, forming an image of the topogram of the surface of the part and axis 3 of rotation of system 2 relative to the axis of symmetry of the test surface, made in the form of a lens, installed with a possibility of moving along the axis of symmetry, node. 4 orientation of the optical axis of the system 2, equipped with a mechanism for input and output from the course of the laser beam 1, collimator 5, a reflecting mirror b, a hologram 7, node 8 for orientation of the interference field, equipped with a mechanism (not shown) for input and output from the interference field , transparency 9 of the topogram of the reference surface, set in the plane. images of system 2 rotated on axis 3 to the working position, and executed as a series of opaque strips on a transparent substrate, and spindle 10 for mounting a controlled axisymmetric part.

Node 4 consists of a reflecting mirror 11 and a glued-up rotary prill 12 with a translucent surface 13. Node 8 consists of an alignment prism 14 with a translucent face 15 and with a reflective face 16 and a reference transparency 17 of interference fringes in the form of a series of opaque strips on transparent substrate. The control method is carried out as follows.

Part 18 with a controlled axis. A symmetrical aspheric surface 19 is mounted on the spindle 10 and centered on the axis of rotation.

Next, the mutual orientation of the controlled axis 18 axis of the part 18, the interference field and the optical axis of the system 2 forming the image of the topogram of the surface 19 of the part 18 that is necessary for using the moire effect is performed, while the axis of symmetry of the part 18

is the base axis, relative to which all operations are relative orientation. The orientation of system 2 is carried out according to the autocollimation scheme, and

the optical axis of this system 2 is aligned coaxially with the axis of symmetry of the part 18. The narrow light beam 20 from the laser. 1 is directed along the axis of symmetry of the part 18 by inputting

on the path of this beam of node 4, the orientation of the optical axis of the system 2, is biased in the opposite direction from the top, at the point O of the aspherical surface 19 of the part 18. For more

accurately performing the alignment operation of the beam 20 with the axis of symmetry of the part 18 (in the case of a rough aspherical surface) in the vicinity of the point O a layer of reflective liquid 21 is applied, the part 18 is brought into rotation on the spindle 10,

a funnel is formed in the liquid, the vertex of which exactly coincides with point 0.

It is assumed that

The axis of symmetry of the part 18 coincides with the axis of rotation of the spindle 10 of the machine (not shown) to process the aspherical surface, since the described method of controlling the deviation of the shape can be used as a stage of the technological process of forming the aspherical surface without removing the part from the machine spindle. If

when part 18 is rotated, beam 20 describes, in the reverse direction, circles around itself in forward motion, then using adjusting movements of system 2, both paths of beam 20 can be combined in space, for example, when visually observing this alignment on a semi-transparent surface 13. Next, enter beam path .20 optical system 2, and the axis of this

system 2 is set coaxially with the axis of symmetry of the part 18, and the position of the coaxiality is also monitored on the specified translucent surface 13 due to the alignment constant of the beam 20 in the forward

and reverse the course obtained before the introduction of this beam of the given system 2 into the course. After that, the node 4 is brought out of the course of the beam 20. - The beam 20 is expanded by the collimator 5,

it reflects from mirror 6 and diffracts on hologram 7, from which the interference field 22 is reconstructed with an equidistant step ft. los

An interference field 22 is directed onto the controlled surface 19 at an angle of f to its axis of symmetry, and a topogram — contour interference — surface relief map is formed on this surface. The orientation of the integrated field 22 relative to the axis of symmetry of the part 18 is performed by inserting the node 8 thereto, the quote prism 14 of which is rigidly connected to the reference banner 17 of the image of the interference fringes by the edge 16 of the alignment prism. The working edges 15 and 16 of the adjustment prism 14 and the plane of the transparency 17 are oriented relative to each other at given angles 6 and V, the translucent edge 15 of the adjustment prism is set perpendicular to the axis of symmetry of the part 18. In this case, the angle determines the direction of the reflected interference fringes of the field 22 from the reflecting face 16 of the adjusting prism 14, and the angle V defines the pitch of 17 strips applied to the reference transparency. When the interference fringes reflected from the face 16 are superimposed on the strips of the reference transparency 17, a moire pattern is formed, the auxiliary, tuning operation is performed compared to the main, measured by the moire pattern formed by the transparency. If the step of the reflected interference fringes and the stripe spacing to the transparency 17 are the same, then adjust The moire pattern has a strip of infinite width. The direction of interference bands, i.e. The angle Y is variable, you can get a tuning mu, ay on the {1 ° infinite width and, thus, orient the interference field 22 relative to the base axis (the axis of symmetry of the part 1) The simplest option is the angle f-0. Setting the angles d and V can be The interference fringes at the desired angle j. After this, the node 8 is derived from the interference field 22. The transparency 17 is performed in various ways (photographing a drawing, which is a system of straight lines, synthesized on a computer, cutting strokes on a transparent substrate with power separating machines, etc.).

Optical system 2 is rotated by an angle .r relative to the axis of symmetry of the part Ox around axis 3, mounted in point C, and the lens of this system 2 forms an image of the topogram of the aspheric surface 19 in the plane of the reference image 9 corresponding to the surface 19. As a result of the conjugation of two images of topograms, a moire pattern is formed in the form of moire strips in the zones of deviation of the aspherical surface being monitored from the calculated, reference Oh.

The relationship between the product (x.j,) and Y2 (X2) of the functions describing the reference and controlled surfaces in a controlled section, combined with the xy plane, in a pair of conjugate points x and Xg, is defined as follows:

v | (x,) (5inp4) cos; a

2 (hr ii

in fj

v; (x,) si

--51PE

cos

Formula (1) allows determining the value of the angle of inclination of the tangent V or the angle of inclination of the normal relative to the axis oy at a given point Xg of the test surface 19 by the value of the derivative) formula (1) ..

The deviation of the angle of inclination u.cL of the normal at the corresponding point of the tested aspherical surface 19, which characterizes the deviation of the surface shape from the calculated angle, is determined by the formula

ticos fot + fi)

(2)

If the section of the calculated reference surface by the xou plane is specified as a broken line with a step li (step surface), the beginning of which is aligned with the top of the aspherical surface, the normal angle for the middle, the nth part of the broken line is also determined by the formula 2) at

oC oi,

to ucL ..

The value of i3c (, is preliminarily calculated for a given equation of the test surface at a predetermined step of the moiré stripes h, according to the tolerance, and is determined in the process of control by the measured step ti, while i

i Aon

Required control accuracy

(LoC) deviations of the form are provided by the optimal choice of the parameters / E, b for this type of controlled aspherical surface by recording the measured value b, by qualifying step Ii of the interference field used to obtain topographic interferograms.

The described method does not require the presence of a part with a reference surface of a complex profile, made according to the calculated equation of the optimal comparison surface and tested with an order of magnitude higher than the required manufacturing accuracy. In the described method, a flat equivalent of the reference topogram, a transparency 9, corresponding to the lens used in the system 2, fronting the image of the topogram of the surface of the part, is calculated and made, and placed in the image plane of this lens, paired with the plane of the target surface 19. Thus , a synthesized image of the reference topogram is obtained, i.e. a synthesized image of the topographs of the reference surface, and the reference surface is understood to be the mathematically given surface of a complex profile (corresponding to the calculation equation of the surface to be tested or another selected comparison surface (step surface). The synthesized image is performed, for example / in the form of a banner, i.e. a system seta opaque stripes on a transparent substrate.

The transparency 9 must have movements in three mutually perpendicular and directional lines for exact conjugation of two images of topograms (detail and reference), at which the maximal contrast of the moire strips will be observed, as well as in order to combine the edges of the two surfaces. Naturally, the size of the synthesized image on the transparency 9 must be equal to the size of the image, which is shaped by the lens of system 2. This is achieved during the synthesis of the transparency 9, taking into account the scale of the image given by the lens of system 2.

In order to observe interference fringes on the entire test surface 19 (in the case of axisymmetric surfaces it is half the meridional section with a small transition; the top of the point O), or to opt them using optical with stems, it is necessary to increase the resolution of the system 2 N. This system.2 in the direction / close to the direction of the normal to the middle zone of the meridional section of the test surface 19, while, if possible, try to bring this direction closer to mali, surface portion with a maximum spatial frequency of the interference fringes,

Thus, in the described method, the system 2, which forms the image of the topogram of the surface of the part being monitored, and the interference field in the form of a series of equidistant planes are oriented at the calculated angles y and ft relative to the axis of symmetry of the surface 19, coinciding with the axis of rotation on the spindle 10 of the machine . In this case, the optical axis of the specified system 2 intersects the axis of symmetry of the part 18 at a given point C. C. For the inspection, you must install a transparency 9, which is a synthesized image of the reference topogram, in the image plane unfolded on

0 of system 2, aligning the reference mark on the banner 9 and, on the image of the topogram. The pitch of the resulting moire fringes is measured in / transmitted light by a scanning one5 coordinate device (not shown) mounted behind the image plane of system 2.

The described method makes it possible to control the deviation of the shape of the axisymmetric aspherical surfaces of higher order with an accuracy of 2-5 in the angular measure and provides an increase in productivity.

In view of the adopted orientation system

The five main components of the concept that implements the method, the moire pattern obtained is unambiguous without orientation of the test surface over three base points. The axisymmetry of this surface allows one to control deviations of shape in different meridional sections with a constant installation of the image of the reference topogram.

5 In this case, the observation of the moire pattern and the measurement of the pitch of the moire stripes are carried out in real time. To determine the shape deviation in the selected area of the aspherical surface, it is sufficient to measure the pitch of the corresponding moire band without the need to determine the location of this band relative to the origin.

five

The invention allows, with high accuracy and productivity, to control the deviation of the shape of axisymmetric aspherical surfaces during their formation without removing parts from the machine spindle.

Claims (1)

THE METHOD FOR CONTROLING THE SURFACE FORM OF THE SURFACE OF DETAILS OF COMPLEX FORM, which consists in the fact that they obtain topographic images of the surfaces of the controlled part and the standard, combine these images, obtain a moire pattern in the form of moire stripes, by the step of which they judge the deviation of the shape surface of the part, distinguishing with the fact that, in order to increase the accuracy and performance of control of parts with axisymmetric aspherical surfaces of higher order, they set the optical axis with the optical axis before combining the images of the system forming the image topogram 1 1 of the part’s surface, coaxially with its axis of symmetry, directs an interference field with an equidistant stripe pitch at a given angle to the part’s surface, sets the specified system relative to the symmetry axis of the part at an angle determined by the resolution dnoco6 of this system and the direction of the norms the surface area of the part with the maximum frequency of the observed interference bands. SL eo>