RU1772612C - Device for measuring lateral dimension of parts - Google Patents

Abstract

The invention relates to measuring technique and can be used for accurate non-contact measurement of the transverse size of metal, glass, polymeric and other materials, for example, the diameter or width of rolled products, in order to control the manufacturing process. The aim of the invention is to increase the range of measurements. The goal is achieved in that the device is equipped with an optical wedge. As the multifaceted mirror prism rotates, the axis of the light beam exiting the lens moves parallel to itself in a direction perpendicular to the optical axis of the lens. The beam emerging from the lens is deflected by an optical wedge, crosses the measurement zone with a controlled part, and is collected at a photodetector. As the multifaceted mirror prism rotates, the light beam emerging from the optical wedge moves parallel to itself in the measurement zone with the controlled part. In this case, the distance between the boundary beams of the illuminating beam after passing through the optical wedge increases and, therefore, a large-sized part can be installed in the measurement zone. When the scanning beam crosses the controlled part, a shading pulse is generated at the output of the photodetector, the duration of which is proportional to the transverse size of the part. In another embodiment of the device, the sweep of the directed radiation beam is achieved by changing the angle of refraction of light during rotation of the optical cube. When two optical wedges are used in the circuit, a large magnification factor can be achieved with a much smaller angle of the optical wedge, which reduces the criticality of the circuit to the influence of disturbing factors, pf, 2 zp f-ly, 5 ill. (L C x1 XJ

Description

The invention relates to measuring technique and can be used for accurate non-contact measurement of the transverse size of metal, glass, polymeric and other materials, such as diameter or width of rolled products, in order to control their manufacturing process.

A device is known for measuring the transverse dimension of a part containing a source of a directed beam of radiation — a laser and a scanning unit located along its rays, made in the form of a rotating mirror mounted in the focal plane of the lens and a receiving unit including a collimating lens, a photodetector, and a signal processing device . The processing device registers the beginning and the end of the shading pulse corresponding to a two-fold drop in the signal amplitude, measures its duration by the number of pulses of the crystal oscillator, and the size of part 1 is calculated from the pulse duration.

A transverse dimension measuring device is also known, consisting of a scanning unit including a sequentially directed source of a directed radiation beam, a lens and a rotating optical cube, and a receiving unit including a collimating lens and a photodetector 2.

Closest to the proposed technical solution, selected as a prototype, is a device for measuring the transverse dimension of a part, comprising a scanning unit, consisting of an optically coupled source of a directed beam of radiation from a multifaceted mirror prism and a lens mounted at the focal distance from the reflecting face prisms and a receiving unit including a collimating lens, a photodetector, a detection and measurement circuit for a shading pulse 3.

A disadvantage of the known device is that its measuring range is bounded above by the magnitude of the lens diameter.

The aim of the invention is to increase the range of measurements.

This object is achieved in that the device comprising a scanning unit, consisting of a sequentially mounted source of a directed beam of radiation, a scanning unit and a lens, a receiving unit including a sequentially mounted collimating lens, a photodetector and a circuit for isolating and measuring the duration of the shading pulse, is equipped with an optical wedge, located at the output of the scanning unit and oriented in such a way that its main section lies in the scanning plane of the scanning beam, and the normal and to the first and second surfaces of the optical wedge form, with the optical axis of the lens, the angles d and a.g respectively equal to O a arcsln (1 / n) and t a - y, where n is the refractive index of the material of the optical wedge, y is the angle at the apex of the wedge.

The device can be equipped with a second optical wedge identical to the first one located along the radiation behind the first optical wedge and oriented so that the vertices of both wedges are located on opposite sides of the heating axis of the scanning unit, and the first and second along the radiation surface of the second optical wedge the axis of the scanning beam emerging from the first optical wedge, respectively, is the angles (-ai) ii (-oa).

In addition, the device may be provided with another second optical wedge, which is located along the radiation in front of the collimating lens and

oriented so that the first along and emitting the surface of the second wedge is perpendicular to the optical axis of the scanning beam.

On Fig, 1 shows a diagram of the proposed

devices with one optical wedge; figure 2 is a variant of the circuit of the device with two optical wedges; Fig. 3 is an optical diagram of a device with a second optical wedge in a receiving unit; figure 4 the course of the axial rays of the scanning beam in the optical wedge; Fig. 5 is a graph showing the dependence of the magnification of the measurement range on the angle at the apex of the optical wedge.

The device (Fig. 1) contains a scanning unit 1, consisting of an optically coupled source 2 of a directed radiation beam, a scanning unit 3, made in the form of a rotating multifaceted mirror prism, and a lens 4 mounted at the focal distance from the reflector, an optical wedge 5 and a receiving unit 6. consisting of a collimating lens 7, a photodetector 8 located at the focus of the lens 7, and a circuit 9. for isolating and measuring the duration of the shading pulse, the input of which is connected to the output of the photodetector 8. Controlled part 10 Position the wedge between a first optical receiving unit 5 and 6.

All elements of the optical circuit of the device are located on the same optical axis, and the optical wedge 5 is oriented so that its main section lies

in the plane of the scanning beam, and the normals to the first and second surfaces of the optical wedge form 4 angles 0 with the optical axis of the lens 4, and arcsirt (1 / n) and OS zi - у, where n is the refractive index of the material of the optical wedge, у is the angle at the top of the optical wedge.

The device (figure 2) additionally contains a second optical wedge 11, which is oriented similarly to the first with respect to the axis of the light beam incident on it, and its vertex is directed opposite to the top of the first optical wedge 5.

The device (Fig. 3) in the space in front of the receiving unit 6 further comprises another second optical wedge 12, which is oriented so that its first surface is perpendicular to the axis of the scanning light beam.

The controlled part 10 is located in the device of Fig. 2 between the second optical wedge 11 and the receiving unit 6, and in the device of Fig. 3 between the first 5 and the second 12 optical wedges.

The device (figure 1) works as follows. A directional radiation source 2 illuminates one of the faces of the polyhedral mirror prism 3 parallel to the light beam. A parallel light beam reflected from the mirror face of the prism falls onto the lens 4 and exits it in the form of a narrow converging light beam. When the multifaceted mirror prism rotates, the axis of the light beam exiting from the lens 4 moves parallel to itself in a direction perpendicular to the optical axis of the lens 4.

The beam emerging from the lens is deflected by the optical wedge 5, crosses the measurement zone with the controlled part 10, and is collected by the collimating lens 7 on the photodetector 8. When the multifaceted mirror prism 3 is rotated, the narrow beam of light emerging from the optical wedge 5 moves parallel to itself in the measurement zone with the controlled part 10. In this case, the distance between the boundary beams of the illuminating beam after passing through the optical wedge 5 is increased and, therefore, a large part can be installed in the measurement zone measures. When the scanning beam crosses the controlled part, a shading pulse is generated at the output of the photodetector, the duration of which is proportional to the transverse size of the part. The signal from the output of the photodetector is processed by a shading pulse extraction and measurement circuit 9, which measures the shading pulse duration and calculates the size of the part to be monitored from it.

The beam 13 exiting from the scanning unit 1 (see Fig. 4) is refracted on the lateral edge 14 of the optical wedge 5, which is located at an angle 1 1 to the optical axis of the lens 4, and, in accordance with the law of refraction, changes the propagation direction. In accordance with the law

refraction angle of incidence a is related to the angle of refraction / ratio: sin a p

0

5

(D

Where

-7Ј

"- the angle of the fall;

j-angle of refraction;

n is the refractive index of the material of the optical wedge;

n0 1 is the refractive index of air.

The angle y at the top of the optical wedge 5 can, for example, be selected from the conditions:

y arcsin () (2)

5

0

5

0

5

0

5

Expressing ai through y and substituting in (1), it is easy to show that, i.e. in this case, the angle of refraction is equal to the angle at the apex of the optical wedge. Figure 4 shows that, under condition (2), the refracted beam 16 is perpendicular to the second surface 15 of the optical wedge 5, and the incident beam 13 forms a normal angle to the second surface of the optical wedge: a - 1 - y.

A simple geometric calculation shows that in such a scheme, when two parallel beams 13 and 17 pass through an optical wedge 5, the distance between them increases by a factor of v. D2

D7

cos y

(3)

sin 90 ° - arcsln (n-sin y) where v is the magnification factor;

Da is the distance between the refracted rays 16 and 18;

DI is the distance between the incident rays 13 and 17.

Thus, the proposed scheme provides an increase in the scanning zone of a narrow beam of radiation, thereby increasing the size of the controlled parts in comparison with the prototype.

Geometric analysis shows that an increase in the scanning zone takes place only if the angle of incidence of the scanning beam on the first surface of the optical wedge lies in the interval 0 Щ arcsin (1 / n), and the optical wedge is oriented in such a way that it is normal to its second surface forms an angle -y with the optical axis of the beam exiting the scanning unit.

It should also be noted that for a given angle of incidence of the beam on the first surface of the optical clique, the fulfillment of condition (2) provides the highest magnification factor v.

In accordance with formula (3), when condition (2) is fulfilled, the magnification factor depends on the refractive index n and angle y at the apex of the optical wedge. Fig. 5 shows, by way of example, graphs of v (y) for two grades of glass K8 (n - 1.5147) and TF5 (n - 1.749). The graphs show that with increasing angle y at the apex of the optical wedge, a monotonous increase in the coefficient of increase v occurs, which, as it approaches the limit value, the reproach tends to infinity. The angle at pre is equal to the angle of total internal reflection:

Pre arcsin (-) (4)

For example, for K8 glass, y = 34.9 °. Thus, by choosing the appropriate brand of glass and the angle y at the apex of the optical wedge, the necessary increase in the range of controlled sizes can be achieved. For example, when an optical wedge made of TF5 glass with an angle at the apex of 31.5 ° is introduced into the circuit, the measurement range of the known device doubles with a constant lens diameter.

From the graph depicted in Fig. 5 and the analysis of formula (3), it follows that as the angle at the apex of the optical wedge grows, and, therefore, in accordance with (2), as the angle of incidence a increases, the coefficient of increase V increases rapidly, to infinity with Y those. a rapid increase in the sensitivity of the magnification coefficient V to the angle of incidence of light on the optical wedge is observed. Therefore, for large values of the magnification coefficient v, the presence of disturbing factors, such as, for example, uneven thermal expansion of the structural elements of the device or their vibration, can lead to the displacement of the optical wedge relative to the lens and to a change in the magnification coefficient V, which reduces the measurement accuracy. To prevent this undesirable phenomenon, a second optical wedge 11 may be inserted into the device (see Fig. 2). Both optical wedges 5 and 11 are made identical and rigidly fixed on a common base so that in the initial position the angle 1 1 of the incidence of the radiation beam on the first optical wedge is equal in magnitude and opposite in sign of the angle (- op) of incidence of the radiation beam on the second optical wedge . In this case, the scanning area increases v times after the scanning beam passes through

0

5

0

5

the first optical wedge and even v times after the scanning beam passes through the second optical wedge, and the total magnification factor is:

v06U, v, (5)

Therefore, when two optical wedges are used in the circuit, a large magnification factor can be achieved with a much smaller angle at the optical wedge, which reduces the criticality of the circuit to the influence of disturbing factors.

In addition, in such a scheme, with a decrease in the angle of incidence of radiation on the first optical wedge, an increase in the angle of incidence of radiation on the second optical wedge occurs, and the overall coefficient of increase of the system remains unchanged to a first approximation, since a decrease in the coefficient of increase of the first wedge is compensated by an increase in the coefficient of increase of the second wedge, while the measurement accuracy of the device remains unchanged.

To reduce the light diameter of the collimating lens 7 of the receiving unit 6, the device can be equipped with a second optical wedge 12 (see Fig. 3) installed in front of the objective of the receiving unit. The optical wedge 12 is oriented in such a way that its magnification factor is Vflon 1, which provides a reduction in the scanning area at the input of the receiving unit 6, and, accordingly, a reduction in the size of the receiving unit.

The calculation shows that the largest reduction in the size of the scanning zone at the inlet of the receiving unit can be achieved when the additional optical wedge is oriented in such a way that its main section lies in the scanning plane of the scanning beam and the first surface is perpendicular to the optical axis of the scanning beam.

Claims (2)

1. A device for measuring the transverse dimension of a part, comprising a scanning unit, consisting of a sequentially mounted directional beam source, a scanning unit and a lens, a receiving unit including a collimating lens, a photodetector and a detection and measurement circuit for the duration of the shading pulse in series, characterized in that that, with the aim 5 5 To increase the measurement range, it is equipped with an optical wedge located at the output of the scanning unit and oriented so that its main section lies in the scanning plane of the scan beam, and the normals to the first and second surfaces of the optical wedge form the angles IN INGS, respectively, equal to 0 i i arcsln (1 / n) lag-y-y gAe n the refractive index of the material of the optical wedge, y is the angle at the apex optical wedge. 2. The device according to claim 1, with the exception that it is equipped with a second optical wedge identical to the first one located along the radiation behind the first optical wedge and oriented so that the vertices of both wedges are located along different sides from the optical axis of the block 0 5 scanning, and the first and second along the radiation surface of the second optical wedge form with the optical axis of the scanning beam emerging from the first optical wedge, respectively, the angles (-I1) And (). 3, The device according to claim 1, it is desirable that it is provided with a second optical wedge located along the radiation in front of the collimating lens oriented so that the surface of the second wedge is first perpendicular to the optical along the radiation axis of the scanning beam. L Figure 1 kЈ  J FIG. 2 Thebes. Z Fig 4 V Og / Dt, crab & &,.