Device for measuring the roughness and waviness of the surface at fixed values of base length

 

(57) Abstract:

The device relates to techniques for the measurement. The device includes a base with a hole, is fixed on the base of the lighting system for the formation of the incident radiation, the optical receiving system, consisting of a photodetector, a rotating modulator, on the cylindrical surface of which is made of holes, and a signal processing unit, consisting of amplifier key block connected to the additional output of the photodetector unit, a subtraction unit, division, averaging, divide, store signals and indicating devices, optical spatial filtering of the radiation of the lighting system, made in the form of two coaxial lenses that are installed apart from each other at a distance equal to the sum of their focal lengths, at the point of coincidence of the tricks that I have posted a screen performed in parallel to the base of the slit, the spatial filtering block radiation. The device improves the accuracy of measurement and makes the measurement results identical to the results of measurements on the profilometers. 3 Ile

The invention relates to techniques of measurement and can be used to control output from regli, optical, printing industry, in aircraft, in coating technologies.

The basis of the invention is the development of devices for measuring the roughness and waviness of the surface at fixed values of the base length, which would ensure the allocation of short-wave and long-wave component of the profile by creating a spatial optical filters with well-defined borders bandwidth, which is given by the values of the base length L, which will increase the measurement accuracy and to extend the functionality of the device.

The problem is solved in that known device for measuring the roughness and waviness of the surface at fixed values of the base length, containing a base with a hole, is fixed on the base of the lighting system for the formation of the incident radiation, the spatial filtering of the radiation of the lighting system installed coaxial lighting system and executed in the form of two coaxial lenses that are installed apart from each other at a distance equal to the sum of their focal lengths, at the point of coincidence of the tricks that I have posted a screen made who - the Lina waves incident radiation of the lighting system;

F1- the focal length of the lens optical spatial filtering of the radiation of the lighting system;

Lm- the maximum value of the base length;

the optical receiving system consisting of a sensor, modulator, on the cylindrical surface of which is made holes and spatial filtering of the light reflected from the sample surface, made in the form of collimating lenses mounted between the base and the modulator so that the point of focus of the collimating lens placed the surface of the modulator on the end surface of which is fixed a plate for blocking light from the additional light source to the additional photodetector, the signal processing unit comprising an amplifier connected to the photodetector, the key block, the block subtraction, separation unit, block averaging, unit division, the storage unit signals and indicating devices, with an amplifier, the separation unit, the block averaging, subtraction unit, the unit, the storage unit signals and indicating device connected in series, the input key unit is connected to the output D. the subtraction, the block dividing unit and store signals openings in the cylindrical surface of the modulator in the form of slits, the width "b" one of which is chosen from the condition:

b = F2/Rj,

where

F2- focal length collimating lens;

Rjis the radius of the needle profilometer, which attested the device, the width "c1" the rest of the slots is chosen from the condition:

ci= F2/Li,

where

L1- the value of the base length;

i = 1, 2, ..., n;

n is the number of base lengths;

and the collimating lens, the projection axis of the modulator and the photodetector of the optical receiving system is installed coaxially in the direction of the specular component of the reflected light flux from the surface.

The distinctive features that characterize the form of the optical spatial filtering of the radiation of the lighting system and placing it relative to the lighting system, as well as well-defined slit width a, the dimensions of which are limited to a maximum value of the base length Lmthe measured surface profile of the proposed device is provide for the creation of the wave front of the incident radiation with a spatial periment spatial filtering of the wave front of the investigated radiation (Handbook of laser technology. Kiev, "Technique", 1978, 281 - 284).

In the device collimating lens and the modulator with holes (transparency) are also designed to filter the reflected radiation from the sample surface at spatial frequencies, but this filtering is carried out by the same dependencies as in the measurement of roughness and waviness mechanically, when using the movement of various needles along the sample surface, record the signal on the vertical displacements of these needles. This signal is not fully corresponds to the true profile for the following reasons. When measuring the roughness and waviness mechanically in these devices is the filtering of this signal by the base length L1to highlight the components of this signal is related to either a component profile, called roughness or part of the profile, called the wave. For example, when measuring the roughness of all information about the long-wave part of the profile, in excess of L1that is discarded, and when measuring waviness discarded all information about the short-wave part of the profile, the smaller the L1. The rules of this filter and the values of the base length L1= 8; 2,5; 0,8; 0,25; 0,08 Mercia signal is an electric filters (RC-series).

In the invention, where information about microtopographic surface is contained in the scattered light, the filtering information on the studied profile is carried out using a spatial optical filters with well-defined borders bandwidth, which is given by the values of the base length L1. This goal is achieved as follows. The wave front of the radiation incident on the analyzed surface should not contain distorted smaller Lmwhy the radiation from the illuminator passes through the spatial optical filter with a certain limit of the bandwidth, which is defined by the maximum value of the base length Lm. Then all the distortions of the wave front in the reflection from the sample surface with a periodicity of the wave front lower L1will be caused only by reflection from the short-wave component of the profile called roughness with a given value of the base length L1. Registering the signal only with such distortions of the wave front, i.e. the reflected radiation passing through the spatial optical filter with a certain limit of the bandwidth, which is determined by the value of the base length Lireceived information caused by reflection from the long-wavelength component of the profile called waviness with a given value of the base length Li.

But the intensity of the reflected radiation will greatly depend not only on microtopographic surface, but also on the nature of the reflective surface (Fresnel coefficients of reflection), from surface contamination. In order to exclude the influence of the proposed device is designed to provide the division signal characterizing the roughness on the sum of the signals characterizing the roughness and waviness. Similarly, the inventive device converts the signal characterizing the undulation.

Thus, the invention allows to measure the signals proportional to both the roughness and waviness of the surface at fixed values of the base length Li.

Based on the above analysis of known sources of information, we can conclude that the proposed device for measuring the roughness and waviness of the surface at fixed values of base length not obvious from the prior art, and therefore meets the condition of patentability "inventive step".

In Fig. 1 shows a device for measuring the roughness and waviness with fixed values of BA the bandwidth for spatial filtering of the radiation of the light source and the spatial filtering of the radiation, reflected from the sample surface as a function of frequency distortion of the wave front x.

Device for measuring roughness and waviness at fixed values of base length comprises a base 1 with an opening 2, is fixed on the basis of the illumination system 3 for the formation of the incident radiation, the spatial filtering of the radiation of the lighting system installed coaxial lighting system and executed in the form of two coaxial lenses 4 and 5 are set apart at a distance equal to the sum of their focal lengths, at the point of coincidence of the tricks that I have posted the screen 6 is made parallel to the base 1 by the slit 7, the width of which "a" is chosen from the condition:

a = F1/Lm,

where

- the wavelength of the incident radiation of the lighting system;

F1- the focal length of the lens optical spatial filtering of the radiation of the lighting system;

Lm- the maximum value of the base length.

In the direction of specular reflection of radiation from the surface of the investigated material in the device is placed optical receiving system consisting of the photodetector 8, the modulator 9, a cylindrical surface the target surface, made in the form of a collimating lens 12, is installed between the base 1 and the modulator so that the point of focus of the collimating lens 12 is placed the surface of the modulator on the end surface of which is fixed to the plate 13 to overlap the light flux from the secondary light source 14 to the additional photodetector 15.

The signal processing unit consists of amplifier 16 connected to the photodetector 8, the separation unit 17, block averaging 18, the subtraction unit 19 unit 20, the storage unit signals 21 and showing the device 22, the key unit 23, and the amplifier 16, the separation unit 17, block averaging 18, the subtraction unit 19 unit 20, a storage unit signals 21, showing the device 22 are connected in series, the input key unit 23 is connected to the additional output of the photodetector 12, and outputs the key unit 23 are connected respectively with the separation unit 17, the subtraction unit 19, unit 20 and the storage unit signals 21.

Openings in the cylindrical surface of the modulator 9 is made in the form of slits, the width "b" one of whom 10 (Fig. 1, 2) is chosen from the condition:

b = F2/Rj,

where

F2- focal length collimating lens oil 11 is chosen from the condition;

ci= F2/Li,

where

Li- the value of the base length;

i = 1, 2, ..., n;

n is the number of base lengths.

Collimating lens 12, the projection axis of the modulator 9 and the photodetector of the optical receiving system 8 installed coaxially in the direction of the specular component of the reflected light flux from the surface.

The device operates as follows.

The radiation from the illumination system 3, passes through coaxially mounted lenses 4 and 5 optical spatial filtering of the radiation of the lighting system and the opening 2 in the base 1, falls on the analyzed surface. Lenses 4 and 5 are located from each other at a distance equal to the sum of their focal lengths, and at the point of coincidence of their tricks placed the screen 6 with the slit 7, parallel to the base 1. The width of this slit "a" is determined from the condition:

a = F1/Lm,

where

- the wavelength of the incident radiation of the lighting system;

F1- the focal length of the lens optical spatial filtering of the radiation of the lighting system;

Lm- the maximum value of the base length.

Due to this arrangement of the lenses 4, 5 and screen 6 with 7 crack widths. the last rays through lenses 4, 5 and slot 7 in screen 6 all the distortions of the wave front with a periodicity of x smaller Lmclipped. The dependence of the transmittance of this filter as a function of frequency distortion of the wave front x shown in Fig. 3A. Luminous flux with this wave front is used to illuminate the sample surface. Further, when the reflection light flux from the sample surface are distorted wave front. The reflected radiation passes through the spatial filtering of the reflected radiation, consisting of a collimating lens 12 and the modulator 9, a cylindrical surface which is located at the focus of lens 12. Openings in the cylindrical surface of the modulator in the form of slits, the width "b" of one of the 10 chosen from the condition:

b = F2/Rj,

where

F2- focal length collimating lens 12;

Rjis the radius of the needle profilometer, which attested the device, and the width "ci" the rest of the slots 11 is chosen from the condition:

ci= F2/Li,

where

Li- the value of the base length;

i = 1, 2, ..., n;

n is the number of base lengths.

Collimating lens 12, the projection axis modulate the Institute specular component of the reflected light flux from the surface.

Upon reflection from the surface distortion of the wave front due to the short-wave and long-wave part of the spatial spectrum of the surface profile at the location of the focus lens 12 of the slot width "b" block, the spatial filtering of the reflected radiation passes radiation reflected from the surface with a periodicity of x profile from infinity to Rjwhen cracks "ci"from the surface with a periodicity profile x from infinity to the given values of Li.

The dependence of the transmittance of the block in the spatial filtering of the reflected radiation as a function of frequency distortion of the wave front x , if the focus lens 12 is slit with a width "b" shown in Fig. 3b, if the focus lens 12 are slit, the width of each of which is "ci- shown in Fig. 3c.

By definition, the roughness is called the characteristic profile with steps smaller base length Liand waviness - steps, large base length Li. The value of the base length Li= 8; 2,5; 0,8; 0,25; 0,08 mm is strictly regulated (see GOST 25142-82 (STSM 1156-78) "surface Roughness. Terms and definitions").

Thus, the signal Regis is Arisue waviness and roughness, and signal when the slit width "ci"denoted Jthe ox(i) characterizes the waviness of the surface at fixed values of the base length Li.

When one turn of the modulator with the photodetector 8 is supplied to the n+1 signal to the amplifier 16. These signals separation unit signals 17 are separated by n+1 signals in strict sequence for a signal from the key unit 23. The signal separation unit signals 17 are received in the block averaging signals 18 are averaged. In block subtraction signals 19 from the signal of the Jbsubtracting the signals Jthe ox(i) and the received signal Jcher(i) = Jb- Ithe ox(i) characterizes the roughness of the surface at fixed values of the base length Li. To eliminate the dependence of the readings of the device from fluctuations in the light intensity of the lighting system 3 and the difference of the coefficients of reflection Fresnel sample surface in the block dividing signals 20 are determined by the ratio of Icher(i) = Jcher(i)/Jthe ox; Ithe ox(i) = Jthe ox(i)/Jbwhere the short-wave part of the spatial spectrum of the surface profile (roughness) with frequency profile from Rjto Licharacterizes the signal Icher(i), and glendavanhouse.com characterizes the signal Ithe ox(i).

The number of pairs of signals Icher(i) and Ithe ox(i) corresponds to the specified number of base length Liwhere i = 1, 2, ..., n; n is the number of base lengths. The storage unit 21 stores these signals for each specific Liand Icher(i), Ithe ox(i) visually represented on showing the device 22. Key block 23 (Fig. 1) associated with the additional output of the photodetector 15 and to the inputs of blocks division 17, subtracting 19, division 20, storage 21 signals. The key input unit 23 is connected with the additional output of the photodetector 15. In the gap between the additional photodetector 15 and the additional light source 14 moves the plate 13 fixed to the end face of the modulator 9. The position of the plate 13 relative to the slits b and cispecifies the strict sequence of read signals required for operation of the key unit 23, which in turn sets a strict sequence of operations with signals in units of division 17, the subtractor 19, division 20, storage 21 signals.

This device allows the measurement of roughness and waviness at fixed values of the base length, which greatly expands its functional capabilities is filomeno.

Device for measuring roughness and waviness at fixed values of the base length, containing a base with a hole, is fixed on the base of the lighting system for the formation of the incident radiation, the spatial filtering of the radiation of the lighting system, installed coaxially with the lighting system and executed in the form of two coaxial lenses installed from one another at a distance equal to the sum of their focal lengths, at the point of coincidence of the tricks that I have posted a screen performed in parallel to the base of the slit, the width and which is chosen from the condition

a = F1/Lm,

where is the wavelength of the incident radiation of the lighting system;

F1- the focal length of the lens optical spatial filtering of the radiation of the lighting system;

Lm- the maximum value of the base length,

the optical receiving system consisting of a sensor, modulator, on the cylindrical surface of which is made holes, and spatial filtering of the light reflected from the sample surface, made in the form of collimating lenses mounted between the base and the modulator so that the point fastin for blocking light from the additional light source to the additional photodetector, the signal processing unit, state of the amplifier connected to the photodetector, the separation unit, block averaging, subtraction unit, unit, unit for storing signals indicating device and the key unit and the amplifier, the separation unit, the block averaging, subtraction unit, the unit, the storage unit signals and indicating device connected in series, the input key unit is connected to the output of the additional sensor, and outputs the key block are connected respectively with the separation unit, a subtraction unit, a unit and a storage unit signals, the openings in the cylindrical surface of the modulator in the form of slits, the width b one of which is chosen from the condition

b = F2/Rj,

where F2- focal length collimating lenses:

Rjis the radius of the needle profilometer, which attested the device,

the width of the C1the rest of the slots is chosen from the condition

C1= F2/Li,

where Li- the value of the base length;

i = 1, 2, ..., n;

n is the number of base lengths;

and the collimating lens, the projection axis of the modulator and the photodetector of the optical receiving system is installed coaxially in the direction of the mirror sostav the

 

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