RU2375677C1 - Roughness metre - Google Patents

Abstract

FIELD: physics; optics.

SUBSTANCE: invention relates to devices for measuring surface roughness. The roughness metre has a light emitter and a reflected signal photodetector. The light emitter is a laser and the reflected signal photodetector is a photodiode. The roughness metre also has devices for defocusing the light beam incident on the analysed surface and focusing light reflected by this surface, an amplifier for amplifying signal from the photodiode, comparator, AND circuit, binary pulse counter, pulse decoder, memory storage for standard codes, digital comparison device, display device. The signal from the photodiode is transmitted to the amplifier, from the output of the amplifier to the comparator input, from the comparator output to the AND circuit, then to the input of the binary pulse counter, further to the input of the decode, from the output of the decoder to the input of the digital comparison device where signals from the memory storage for standard codes are also transmitted at the same time, and from the output of the digital comparison device to the input of the display device.

EFFECT: wider operational characteristics of the roughness metre.

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Description

The invention relates to the field of measuring surface roughness, in particular to devices for measuring the roughness of various surfaces.

A known roughness meter of the cylindrical surface of products [1], in which the test product is rotated about its axis of symmetry with a given peripheral speed, and the tip of the measuring transducer, making a reciprocating movement, takes readings of the surface roughness.

The disadvantage of this meter is that it is a contact meter, it is used to determine the roughness of only cylindrical parts, it requires their rotation at a certain speed on special equipment, and requires removal of the part from the product.

A device for determining the roughness of shafts and cylinders [2] is known, in which a measuring segment of another material that does not have the same surface finish is applied to a heated controlled surface. The segment is connected to thermocouples and a measuring device. From the heated shaft, the heat flux is transmitted to the segment through the gap between them, heating this segment. If the cleanliness (roughness) of the controlled surface corresponds to the cleanliness of the segment surface, then heating of the latter occurs in a certain time, if it does not, then the heating time will be different.

The disadvantage of this device is the low accuracy of determining the roughness, the need for heating the controlled part and the shutdown of the process.

The closest technical solution is a device for measuring surface roughness by the optical method [3], in which a narrow beam of light from a source through a slit is projected onto a controlled surface of the product. An illuminated strip forms on the surface, which is the trace of the intersection of the profile by the plane of the light flux. The rays reflected from the protrusions and depressions of the profile are displaced on the ocular mesh relative to each other. The amount of displacement depends on the height of the bumps. By combining the lines drawn on the grid of the eyepiece-micrometer, with the protrusions and depressions of the profile of the controlled surface, the surface roughness is determined.

A double microscope [3], IMS-11, which is this device, consists of a lighting tube and a microscope fixed in a housing. The measurement is carried out by an ocular micrometer.

The disadvantage of the IMS-11 microscope is that it can be used to determine the surface roughness of small, in size, parts and, of course, with disassembly of the product. In addition, the double microscope itself has a rather complex and massive design and is inconvenient for use in the field.

The objective of the invention is to develop a device for determining surface roughness, which should be compact and would allow to determine the roughness in any conditions, including field, with or without disassembly of the product.

The technical result of the invention is achieved by the fact that in a roughness meter containing a light emitter and a photodetector of the reflected signal, a laser is used as a light emitter, while the meter further comprises devices for defocusing the beam incident on the surface to be tested and focusing the stream reflected by this surface: as a reflected photodetector flow applied photodiode; signal amplifier from the photodiode; a comparator comparing the voltage supplied to it from the amplifier with a ramp of the generator and generating a voltage pulse; the “I” circuit encoding a pulse arriving at it from the comparator into a packet of short pulses of a generator of a reference frequency; a binary pulse counter that counts the number of pulses in a packet; pulse decoder; a memory device for reference codes, where values of signals from known roughness standards are recorded in advance; a digital comparison device comparing the signal received from the surface to be monitored with the reference signals; an indication device where the roughness value of the controlled surface of the part is displayed, and the signal generated in the photodiode enters the amplifier, from the amplifier output to the comparator input, and from the comparator output to the “I” circuit, then to the input of the binary pulse counter, then to the input of the decoder, from the output of the decoder to the input of the digital comparison device, where signals from the memory device of the reference codes come simultaneously with this signal, and from the output of the comparison device to the input of the display device.

A defocused radiation flux from any source, for example, from a laser, of any range and any intensity, in particular low, falls onto the surface of the controlled part. The controlled surface absorbs part of the energy of the incident flux, and the remaining part reflects, which focuses and enters the photoelectric detector, in particular the photodiode, is compared with the reference value of the reflected flux obtained in advance from the reference roughness samples for the used source of irradiation of the surface of the controlled part. In a photodiode, the reflected stream is converted into a signal in the form of an electric voltage or current. Depending on the surface roughness, the intensity of the reflected flux and, consequently, the magnitude of the signal generated in the photodiode will also change: the higher the purity class, i.e. the smaller the surface roughness, the larger the magnitude will be the reflected flux and the higher the magnitude of the signal generated by the photodiode.

When comparing a signal from a photodiode with reference signals, some reference signal will be equal to (or closest to) the received signal. This will correspond to a certain roughness.

New features with significant differences are:

- the presence of defocusing and focusing systems;

- photodetector, for example a photodiode;

- a block for processing signals from a photodetector;

- The relationship between the elements.

The use of new features, together with the well-known, and new connections between them ensures the achievement of the technical result of the invention, namely: the possibility of creating a compact device that can be used in any conditions, including field conditions, both with disassembly of the product, and without disassembly (in working position).

In Fig.1 shows a diagram for determining surface roughness and structural diagram of a roughness meter, Fig.2 - the formation of signals in the elements of the processing unit reflected from the controlled surface of the light flux

The proposed device (Fig. 1) uses a radiation source, such as a laser 1, a defocusing device, such as a lens 2, a test surface of a part 8, a focusing device, such as a lens 3, a reflected signal receiver, such as a photodiode 4.

Since the surface roughness is determined by the size of the protrusions and depressions, which have an unequal size, therefore, the beam incident on the controlled surface is defocused in order to average the reflected part of this beam from a certain surface area. Each protrusion on the surface of the part and each cavity will reflect the incident beam individually. However, if we take a certain area of the controlled surface (the spot area of the incident beam), then its reflectivity will determine the reflectivity of the entire surface under study. In this case, a sample is taken from the entire set, where the entire controlled surface is the studied set of protrusions and depressions, and the area of the ray incident on the surface is a sample from this set. Therefore, the incident beam is not focused, but defocused. And, on the contrary, in order to collect as much energy as possible from the stream reflected from the surface to be monitored by the photodetector, the reflected beam is focused on the photodetector, for example a photodiode, in which, under the action of this beam, a signal appears in the form of an electric voltage or current. The higher the cleanliness class (less roughness) of the surface, the greater will be the reflected flux and the signal that appears in the photodetector.

The signal received from the reflected beam in the photodetector is compared with reference signals received in advance from surfaces with a known roughness, and with which of them coincides in magnitude, such a roughness will have a test surface.

The roughness meter (figure 1) contains a light emitter, such as a laser 1, a defocusing device, such as a lens 2, a focusing device, such as a lens 3, a photodetector 4, such as a photodiode, photo amplifier 5, comparator 6, circuit "And" 7, the controlled surface of the part 8, a ramp generator 9, a pulse generator of a reference frequency 10, a binary pulse counter 11, a decoder 12, a memory device for reference codes 14, a comparison device 13 (digital), an indication device 15.

The roughness meter works as follows.

The emitter 1, in particular a laser, forms an incident beam and directs it to a defocusing device 2, for example a lens (if the laser beam is defocused, then device 2 is not required). Then the laser (or any other) beam falls on the controlled surface of the part 8 at any angle, providing reflection of part of the incident radiation. Part of the energy of this ray is reflected from the area of the ray incident on the surface of the ray (the cross-sectional shape of the reflected ray repeats the shape of the spot of the ray incident on the surface, whether it is ellipsoidal or any other).

The energy of the reflected flux can be very small, the radiation source 1 can be a light source with a very weak energy, with scattering in space. Therefore, a focusing device 3 is installed in the path of the reflected flux, which collects the energy scattered in the reflected beam at the focus where the photodetector 4 is located, for example, a photodiode. However, in this case, the magnitude of the electric voltage (or current) generated by the energy of this reflected and focused light flux may turn out to be small, therefore, after the photodetector, a voltage amplifier (or current) 5 is installed in the roughness meter, which ensures the operation of all subsequent device elements .

In the proposed roughness meter, the principle of the time-pulse conversion is used, based on the conversion of the measured voltage value U _x from the output of the amplifier 5 into a time interval, followed by coding of this interval by sequential counting into a pulse train. The voltage value U _x by comparing it with a comparator 6 with a linearly varying voltage U _{1 of the} generator 9 (see figure 2, the sloping straight line; the horizontal line is U _x ) is converted into a voltage pulse U _{2 of} duration Δt, which is fed to the circuit "And" 7, where it is encoded into a packet of short pulses of a generator 10 pulses of an exemplary frequency U ₃ . The count of the number of pulses "n" in the packet is carried out in a binary pulse counter 11, where the signal U4 is supplied from the circuit "And" 7

where C is a coefficient characterizing the rate of change of voltage U (t), i.e. U ₁ in the generator of a ramp voltage 9;

T ₀ , f ₀ - period and frequency of the output voltage U _{3 of} the pulse generator of the reference frequency 10.

(m - целое число), можно получить показания значений напряжения U_x в требуемых единицах измерения (В, мВ и т.д.). Затем в дешифраторе 12 этот сигнал дешифрируется и поступает в устройство сравнения (цифровое) 13, куда одновременно с этим сигналом приходят сигналы с устройства памяти эталонных кодов (заранее сняты с эталонов шероховатости). Сравнивая эти сигналы, и когда сигнал с дешифратора 12 сравняется (или будет близок) к одному из эталонных сигналов с устройства памяти эталонных кодов, то с выхода устройства сравнения 13 на устройство индикации 15 подается сигнал в виде номера класса чистоты (шероховатости), например «5» - высвечивается на индикаторе.The equation shows that the number of pulses "n" is proportional to the voltage U _x from the amplifier 5. Choosing the proportionality coefficient

(m is an integer), you can get readings of the voltage values U _x in the required units of measurement (V, mV, etc.). Then, in the decoder 12, this signal is decrypted and fed to the comparator (digital) 13, where signals from the memory device of the reference codes come simultaneously with this signal (previously removed from the roughness standards). Comparing these signals, and when the signal from the decoder 12 is equalized (or will be close) to one of the reference signals from the memory device of the reference codes, then from the output of the comparison device 13 to the display device 15 a signal is sent in the form of a class number of cleanliness (roughness), for example, " 5 ”- is displayed on the indicator.

Using the claimed invention allows to expand the range of tested parts (you can check the surface of parts of any size), improves working conditions and increases labor productivity, makes it possible to create a small-sized and lightweight roughness meter that could be used in any conditions, including field ones, with disassembly and without disassembly of products (in working position).

Information sources

1. USSR author's certificate No. 11104356, cl. G01B 5/28, publ. 09/29/1982

2. USSR copyright certificate No. 1608419, cl. G01B 5/28, publ. 11/29/1988

3. Vasiliev A.S. Fundamentals of metrology and technical measurements. - M .: Mechanical Engineering, 1980. - S.180-183.

Claims (1)

A roughness meter comprising a light emitter, a photodetector of a reflected signal, characterized in that a laser is used as a light emitter, the meter further comprising defocusing the beam incident on the test surface of the part and focusing the beam reflected by this surface; a photodiode is used as a photodetector of the reflected flow; signal amplifier from the photodiode; a comparator comparing the voltage supplied to it from the amplifier with a ramp of the generator and generating a voltage pulse; the “I” circuit encoding a pulse arriving at it from the comparator into a packet of short pulses of a generator of a reference frequency; a binary pulse counter that counts the number of pulses in a packet; pulse decoder; a memory device for reference codes, where values of signals from known roughness standards are recorded in advance; a digital comparison device comparing the signal received from the surface to be monitored with the reference signals; an indication device where the roughness value of the controlled surface of the part is displayed, and the signal generated in the photodiode enters the amplifier, from the amplifier output to the comparator input, and from the comparator output to the “I” circuit, then to the input of the binary pulse counter, then to the input the decoder, from the output of the decoder - to the input of the digital comparison device, where signals from the memory device of the reference codes come simultaneously with this signal, and from the output of the digital comparison device - to the input of the display device.

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