33results about How to "Improve thickness measurement accuracy" patented technology

A structure and method for polishing a device include oscillating a carrier over an abrasive surface (the carrier bringing a polished surface of the device into contact with the abrasive surface, the oscillating allowing a portion of the polished surface to periodically oscillate off the abrasive surface), optically determining a reflective measure of a plurality of locations of the polished surface as the portion of the device oscillates off the abrasive surface and calculating depths of the locations of the polished surface based of the reflective measure.

Method for measuring thicknesses of a film, a foil or a material layer with a measuring head which is spaced away from the film and with which a capacitive thickness measurement is performed, in which an optical distance measurement is performed with a distance measuring device and a distance determined by the optical distance measurement is used in determining the film thickness in the capacitive thickness measurement.

The invention discloses an ultrasonic detection method of scale thickness in a pipeline. The method comprises the following steps of: utilizing double incidences of ultrasonic waves at different angles, establishing simultaneous equations on the basis of propagation velocities of the known ultrasonic wave on the pipe wall and in the filled fluid and the relationship between an incident angle and a refraction angle of the ultrasonic wave by measuring the penetration time of the ultrasonic waves in the pipeline filled with fluid during the double incidences, and further calculating the velocity and the thickness of a scale layer in the pipeline. With the method, the scale thickness can be measured under the condition that the scale characteristic is unknown, the working detection of the pipeline can be achieved, and the method has reliable accuracy and no destructive effect.

The invention provides a method for measuring the thickness of a galvanized layer. A galvanized sheet sample is placed in a coating machine, and a carbon rod is used for spraying the surface of the sample with carbon. The sample is placed in an electronic probe sample chamber which is vacuumized, a backscattered electron image of the sample is observed, the thickness of the galvanized layer takes account for 1 / 2 of the scanned area, the line scanning is adopted from the position far away from the outer layer of the galvanized layer by 1 / 2 of the thickness of the galvanized layer to the position, perpendicular to the galvanized layer, far away from the other layer of the galvanized layer by 1 / 2 of the thickness of the galvanized layer in the direction towards a base body to obtain a component analytic curve, 50% of the maximum strength of the steep side of the measured curve serves as the two boundary points of the galvanized layer, and the thickness of the galvanized layer is measured. Different areas are selected and the average value of a plurality of points is worked out, wherein the average value is the thickness of the galvanized layer. The thickness of the galvanized layer is measured through the component analytic curve of the sample, the boundaries are clear, the error problems caused by the fact that the surface of the sample is rough, the shape of the sample is complex, and the contrast of the sample is not obvious can be effectively solved, and the accuracy of measuring the thickness of the galvanized sheet galvanized layer is improved.

The invention discloses a novel coating thickness gauge probe which comprises an outer casing body and a probe. A through hole is arranged in the front end of the outer casing body. The inner diameter of the through hole is consistent with the outer diameter of the probe. One end of the probe extends out of the outer casing body, and the other end is arranged in the cavity of the outer casing body. The probe is connected with a circuit board which is arranged in the cavity of the outer casing body through a signal wire. The circuit board is connected with the monitoring terminal of a thickness gauge through a signal wire. The novel coating thickness gauge probe further comprises a buffer component which is arranged between the probe and the circuit board, and an air blowing component which comprises an air pipe and a miniature air pump. Air blowing holes are arranged on both sides of the through hole in the front end of the outer casing body. One end of the air pipe is fixed in the air blowing holes, and the other end is communicated with a micro air pump arranged outside the outer casing body. A shielding sheet is fixedly arranged on the inner wall of the outer casing body. According to the invention, the novel coating thickness gauge probe has the advantages of simple structure principle and good buffering effect; the probe is prevented from being damaged; air is blown to the surface of the probe to remove dust; the thickness measurement precision is improved; in addition, the novel coating thickness gauge probe has an electromagnetic shielding function, which further improves the thickness measurement precision.

The invention provides a profile self-adaptive alignment ultrasonic thickness measuring device and a profile self-adaptive alignment ultrasonic thickness measuring method. The profile self-adaptive alignment ultrasonic thickness measuring device comprises a base, a translation device, a rotating device and an ultrasonic measuring head. The base is used for fixing the whole ultrasonic thickness measuring device and determining a base coordinate system of the measuring platform; the translation device is arranged on the base, a rotating device is arranged on the translation device, and the rotating device can translate to any position in a plane parallel to the base on the translation device; the ultrasonic measuring head is installed at the tail end of the rotating device, and a plurality of water immersion ultrasonic probes are installed in the ultrasonic measuring head. According to the method, the surface normal vector of the measured area under the base coordinate system can be calculated. Based on the normal vector and the coordinate of the central measuring point, the translation device movement distance and the rotation angle of the rotation device required when the axis of the central measuring head is perpendicular to the measured surface can be calculated through common kinematics transformation. By controlling the movement and rotation of each shaft, the ultrasonic measuring head is aligned with the normal vector of the curved surface, thereby ensuring the accuracy of ultrasonic thickness measurement.

The invention relates to the technical field of laser processing, in particular to a screen plate thickness measurement method. According to the method, the coordinate of a measurement point on a screen plate breadth is (x,y), firstly a laser displacement sensor is moved to the measurement point through shafting motions, measurement is started and thickness data are obtained. The method further includes the following steps: setting a radius r for representing a position range, moving the laser displacement sensor within the position range of the radius r according to a set path, constantly measuring the thickness of the screen plate in the moving process and storing the data until scanning of the laser displacement sensor is completed and the laser displacement sensor returns to the point (x,y), and eventually indicating the thickness of the measurement point with the average value of the obtained thickness data. According to the technical scheme, the thickness of the measured screen plate is obtained, thickness measurement precision of the SMT screen plate is improved, and errors are reduced.

Disclosed is a method for increasing thickness detection precision of a stainless steel cold-rolling mill. The method is characterized by including the steps that steel grade codes and raw material manufacturers are combined to give serial numbers to steel grades, as for different raw material manufacturers which each steel grade corresponds to, corresponding thickness standard plates are respectively manufactured, and the standard plates are used for calibrating a thickness gauge so as to determine alloy compensation coefficients of the steel grades. Thereby, the different raw material manufacturers can be effectively distinguished, and errors of the detection precision of the thickness gauge due to original same steel grade mark but different raw material manufacturers can be avoided. By means of the method for increasing the thickness detection precision of the stainless steel cold-rolling mill, a control system of an existing stainless steel cold-rolling mill is fully utilized, special transformation and added devices are not required, producing requirements can be met, the thickness detection precision can be greatly improved, and the method is simple, practical and reliable.

The invention provides a device for testing the heat conductivity coefficient and the contact thermal resistance of a gas diffusion layer in a compressed state. The device comprises a heating unit, acooling unit, a heat flow column, a heat insulation cover, a temperature measuring unit, an extensometer and a data processing unit; the heating unit comprises a heat insulation cushion block, a heating water tank and a heating constant-temperature water tank; the cooling unit comprises a cooling water tank with a connector at the top and a cooling constant-temperature water tank; the heat flow column comprises an upper heat flow column and a lower heat flow column, the lower end of the upper heat flow column and the upper end of the lower heat flow column are in threaded connection with replaceable test heads, and a test sample is clamped between the replaceable test heads at the upper and lower ends; the heat insulation cover comprises an upper heat insulation cover and a lower heat insulation cover; the temperature measuring unit comprises a plurality of armored thermal resistors and a miniature thermocouple; and the data processing unit is electrically connected with the temperature measuring unit and the extensometer. The device is simple in structure, is combined with a universal testing machine for use, controls the pressure with high precision, and can test the effective heat conductivity coefficient of the gas diffusion layer in a compressed state.

The invention relates to a single-point ring-shaped measuring method for thickness of a surface mounting technology (SMT) screen. The problem that an error is large when the thickness of an SMT screen is measured in an existing laser micromachining industry is solved. The single-point ring-shaped measuring method for the thickness of the SMT screen comprises the steps of setting variable quantity r which represents radius differences of adjacent round rings and setting the number of collected round rings before measurement; if the coordinate of a measuring point M on screen breadth is M (x, y), firstly moving a laser displacement sensor to the position of the measuring point M through axis movement and then moving the laser displacement sensor with a distance r to the positive direction of an x axis, wherein the measuring point is M (x+r, y); collecting reading numbers of the sensor to obtain thickness data; moving the laser displacement sensor with a distance r along the positive direction of the x axis and obtaining the thickness of a circle according to the method; and repeating the steps until the thicknesses of n round rings are obtained. The problem is solved, and the single-point ring-shaped measuring method for the thickness of the SMT screen can be used in the laser micromachining industry.

The invention discloses a non-contact sample thickness measuring method and device based on the Michelson interference principle. By adjusting the angle between an M1 reflector and a sample plane, the optical path of a laser beam is changed, so that the interference fringe is displaced. Then, according to a formula provided by the invention, the thickness of a to-be-tested sample is obtained by calculation. As the measuring method only needs to control the physical quantity of the angle between the M1 reflector and the sample plane, the measuring error is extremely small, the measuring process is simplified and the accuracy of sample thickness measuring is improved. With regard to the measuring device used for achieving the measuring method, the measuring principle is simple and the high-precision expensive instrument is not required, so that the optical path assembly can be integrated into a one-piece device, and a miniature portable device is designed.

The invention relates to a thickness and planeness measuring method for a surface mounting technology (SMT) screen. The thickness and planeness measuring method for the SMT screen mainly solves the problems that a screen thickness measuring method is single and can not represent the thickness of a specific area in the prior art. The thickness and planeness measuring method for the SMT screen comprises the steps of using a standard block for calibration to confirm the distance between two sensors, laying the screen flat and moving the two coaxial laser displacement sensors to a starting position of the left lower corner of the screen through axis movement, enabling the laser displacement sensors to move along a certain path to achieve scanning of the whole breadth of the screen, collecting distance information among the upper surface and the lower surface and the sensors, and fitting the obtained distances among the upper surface and the lower surface and the sensors and the obtained coordinates into a thickness distribution picture and a fitting curve picture of the upper surface and the lower surface according to coordinates of points and obtained thickness information after the scanning is finished. The problem is solved, and the thickness and planeness measuring method for the SMT screen can be used in a laser micromachining industry.

The invention discloses a method for measuring the thickness of a boundary layer, and themethod is realized based on a pitot tube moving and measuring device and a double-sided visual ranging system. The method comprises the following steps: installing the pitot tube moving and measuring device at a to-be-measured section of a wind tunnel, wherein the pitot tube moving and measuring device comprises a bracket and a pitot tube fixed on the bracket; marking a plurality of mark points on the surface of the pitot tube in the incoming flow direction; moving the pitot tube moving and measuring device; after each movement, measuring a total pressure value and a static pressure value, and measuring the position of each mark point; according to the position of each mark point before and after movement, obtaining the deformation of the pitot tube under the action of aerodynamic force, correcting the total pressure value and the static pressure value, and obtaining the corrected total pressure value and the corrected static pressure value; calculating to obtain a dimensionless speed of the movement; according to the dimensionless speed of each movement, obtaining dimensionless speed distribution in the boundary layer; and selecting a corresponding movement distance when the dimensionless speed is equal to a preset value, and further obtaining the boundary layer thickness of the to-be-measured section.

The invention discloses a running gear of a thickness gauge for a rolling mill. The running gear comprises a rack (1), a gear (2) and a running motor (3), wherein the rack (1) is arranged along the horizontal direction; the gear (2) is meshed with the rack (1); the running motor (3) is used for driving the gear (2); one of the rack (1) and the running motor (3) is fixed on a frame (4) of the rolling machine; and the other one of the rack (1) and the running motor (3) is fixed on the thickness gauge (5) for the rolling mill. In the running gear of the thickness gauge for the rolling mill, a gear rack pair structure consisting of the rack (1) and the gear (2) is used for driving, so the thickness gauge (5) for the rolling mill can run in the horizontal direction, the problem of running instability caused by the cylinder push running mode in the prior art is effectively solved, the running characteristic of the thickness gauge (5) for the rolling mill is optimized, the thickness measuring precision is improved and the product quality is improved. The invention also discloses the thickness gauge for the rolling mill, which adopts the running gear.

The invention discloses an oil film thickness measuring method based on an ultrasonic reflection coefficient real part, and belongs to the field of lubricating state ultrasonic monitoring. The method aims at solving the problem of oil film thickness measurement upper limit of an existing ultrasonic reflection coefficient amplitude method. Firstly, a gap between a friction matrix a and a friction matrix b is an air layer, and ultrasonic reflection signals of an interface between the friction matrix a and the air layer are collected to serve as reference signals; then adding lubricating oil between the friction matrix a and the friction matrix b to form an oil film layer, and collecting an ultrasonic reflection signal of an interface between the friction matrix a and the oil film layer as an oil film reflection signal; respectively carrying out Fourier transform on the reference signal and the oil film reflection signal, and calculating to obtain an oil film layer reflection coefficient; extracting real part information of the reflection coefficient to obtain a reflection coefficient real part; and calculating the thickness of the oil film layer according to the real part of the reflection coefficient and the ultrasonic signal center frequency. According to the method, the upper limit of oil film thickness measurement can be improved by tens of microns, and higher oil film thickness measurement precision is realized.

The invention relates to mica plate sorting, in particular to an automatic mica plate sorting device. The automatic mica plate sorting device comprises a base and further comprises a control unit; a feeding mechanism, a plate taking and conveying mechanism, a measuring mechanism and a material receiving mechanism are arranged on the base, the control unit controls the plate taking and conveying mechanism to take a mica plate from the feeding mechanism, the control unit controls the plate taking and conveying mechanism and the measuring mechanism to measure the thickness of a mica plates, and the control unit controls the plate taking and feeding conveying mechanism and the material receiving mechanism to finish mica plate sorting. According to the automatic mica plate sorting device, the feeding mechanism, the plate taking and conveying mechanism, the measuring mechanism and the material receiving mechanism are controlled through the control center to achieve automatic sorting of the mica plates, automatic measuring and automatic sorting are finished, measuring repetition is good, sorting precision is high, and the sorting interval can be flexibly arranged according to actual needs. Design of four layers of circuit boards is adopted in the control unit, the system stability is improved, a 32 ARM CPU is adopted, and the system processing speed is improved.

The invention provides a multi-channel electromagnetic ultrasonic thickness measuring system, which realizes the high speed acquisition, calculation, storage and display of multi-channel ultrasonic echo data. The system provides high performance and it is cost effective and small in size. It consumes less energy as well. The system comprises an electromagnetic ultrasonic energy transducer, an electromagnetic ultrasonic thickness measuring instrument and a host computer. The electromagnetic ultrasonic thickness measuring instrument comprises a signal excitation and reception module, a signal processing module, and a display module wherein the signal excitation and reception module and the signal processing module are interconnected and the output end of the signal processing module is connected with the display module. The input end of the signal excitation and reception module of the electromagnetic ultrasonic thickness measuring instrument is connected with the signal output end of the electromagnetic ultrasonic energy transducer; the signal processing module and the host computer are interconnected. The signal excitation module includes a pulse signal generating circuit, a driving circuit, a MOS tube, and a transmitting pulse generating circuit wherein the pulse signal generating circuit is connected with the driving circuit, the driving circuit is connected with the MOS tube, the MOS tube is connected with the transmitting pulse generating circuit, and the collector terminal of the MOS tube is connected with a high voltage power supply.

The invention discloses a two-dimensional automatic laser thickness-measurement device, system and method of a tubular component. The thickness-measurement device comprises a base seat, a horizontal moving sliding rail, a horizontal moving sliding table, a long-distance supporting upper-cantilever, a long-distance supporting lower-cantilever, a first laser displacement sensor, a second laser displacement sensor and a rotating chuck supporting structure. The thickness-measurement system includes a moving control module, a data collection module, a data reconstruction module, a display module, awork procedure module and the above device. The thickness-measurement method comprises the steps of: fixing a to-be-detected object; starting the device to rotate the to-be-detected object, and simultaneously moving the horizontal moving sliding table along the horizontal moving sliding rail to the other end of the device; emitting lasers by the laser displacement sensors in opposite directions to complete thickness measurement of an entire tubular structure; and displaying a measurement result and an analysis result by the display module. The device, the system and the method effectively avoid changes which are of distance between the laser sensors and are caused due to an excessive stroke, thus effectively reduce thickness measurement errors, and improve thickness measurement accuracy.

The invention discloses a solder paste thickness measuring bracket which comprises at least a sliding rail, wherein two mutually parallel clamping components are slipperily arranged on the sliding rail, and each clamping component is provided with a locking component. The solder paste thickness measuring bracket disclosed by the invention is simple in structure and convenient to use, and can ensure that a double-sided printed circuit board always keeps in a horizontal state in two thickness measuring processes, thereby preventing the double-sided printed circuit board from being affected by a surface mounted component and then improving the thickness measuring accuracy.

The invention discloses an ultrasonic detection method of scale thickness in a pipeline. The method comprises the following steps of: utilizing double incidences of ultrasonic waves at different angles, establishing simultaneous equations on the basis of propagation velocities of the known ultrasonic wave on the pipe wall and in the filled fluid and the relationship between an incident angle and a refraction angle of the ultrasonic wave by measuring the penetration time of the ultrasonic waves in the pipeline filled with fluid during the double incidences, and further calculating the velocityand the thickness of a scale layer in the pipeline. With the method, the scale thickness can be measured under the condition that the scale characteristic is unknown, the working detection of the pipeline can be achieved, and the method has reliable accuracy and no destructive effect.

The invention relates to a cobalt-rich crusting thickness measuring method based on a multi-beam receiving technology, and belongs to the technical field of geological prospecting. The method utilizes a multi-beam receiving technology, a transmitting linear array and a receiving linear array adopt a T-shaped arrangement mode, the transmitting linear array is parallel to the direction of a measuring line, and the receiving linear array is perpendicular to the direction of the measuring line. The direction of the measuring line is the course of a submersible carrier on which the crusting thickness measuring equipment is mounted; the crusting thickness values in a plurality of beams are primarily measured at a time by using a multi-beam measurement technology; and according to a multi-beam receiving technology, seabed micro-topographic relief is obtained, the incident angle of a signal in each beam is estimated, the crusting thickness obtained by measurement in each beam is further corrected, and the crusting thickness change is tracked by adopting a sequential inertial Bayesian filtering method in combination with the crusting thickness change characteristics so that the measurement precision is improved.

The invention discloses a steel pipe ultrasonic thickness measurement device which comprises a machine frame, a supporting base, a steel pipe tracking assembly and a pipe pressing limiting assembly. The supporting base is installed on the machine frame. The steel pipe tracking assembly is installed on the supporting base, and comprises a tracking device and a detecting device. The tracking device comprises a cylinder, a linear guide rail and a slide block. The detecting device comprises a water tank and an ultrasonic measuring head device. The cylinder and the linear guide rail are both installed on the supporting base. The slide block is installed on the linear guide rail. An output shaft of the cylinder is fixedly connected with the slide block. The slide block is fixedly connected with the water tank so as to drive the water tank to get close to or get away from the pipe pressing limiting assembly. The pipe pressing limiting assembly is installed on the machine frame and used in cooperation with the water tank for clamping and limiting a steel pipe. Through the combination of a steel pipe detection production line actual detection procedure, the water tank is in an initial position when the steel pipe does not enter the detection position, the water tank drives the ultrasonic measuring head device to enter the detection position when the steel pipe enters the detection position, and the high-speed detection during the high-speed movement of the steel pipe can be achieved.

The invention discloses a method for accurately detecting the thickness through an ultrasonic wave equivalent peak value. The method includes the steps of detection of ultrasonic wave echo rising edge arrival time Ts, detection of ultrasonic wave echo falling edge arrival time Tx and calculation of echo peak value time Tf, wherein the thickness of a measured object can be obtained by substituting the echo peak value time Tf into an ultrasonic wave thickness measuring calculation formula S=V*Tf / 2. The invention further discloses a device using the method. The method and the device have the advantages that measuring accuracy is improved, and the error is reduced to 0.001 mm or lower; elements are less influenced by the coupling degree, and measuring stability is improved; the phase error is basically eliminated; miniaturization can be more easily achieved, and the area occupied by a timing chip is about one tenth the area occupied by an existing timing circuit; material difference of the measured object does not influence thickness measurement; spreading of ultrasonic waves can be influenced by the pressure and temperature of an ultrasonic probe, and accuracy can be controlled within the range of 0.02 mm through the method.

The invention provides a measurement device and a measurement method for film thickness, and belongs to the field of photoelectric detection. A laser is used for transmitting laser to be functioned on the surface of a material through a focus lens, so as to generate a laser plasma flashing signal; the laser passes through the focus lens and a band elimination filter, enters a photoelectric detector, and then is converted into a voltage signal processed by a processor through an oscilloscope; when the laser energy is large enough, the laser punctures a film material, appears a pit in a flashing intensity curve of a laser-induced plasma, and a linear relation is formed between the time of appearing the pit and the thickness of the film material. According to the measurement device for the film thickness provided by the invention, expensive micro instruments, such as an AFM (Atomic Force Microscope), cannot be needed, the environmental requirement is lower, no tool contact is caused in an integral measurement process, and the cost of changing the measurement tool can be saved and changed; furthermore, the measurement device is easy to operate and is convenient for a worker to use, and can be integrated on an automatic production line, thereby being likely to be popularized and applied in an industrial field.

The invention relates to a thickness measuring device of a vertical glass edging machine, comprising a bracket, a cylinder mounting frame, a bottom plate, a linear potentiometer and a thickness measuring cylinder, wherein the thickness measuring cylinder is installed on the cylinder mounting frame and is connected with the bracket; the cylinder mounting frame is fixed on the bottom plate; the bracket and the linear potentiometer are fixed on the bottom plate; and the bracket is connected with the linear potentiometer. The thickness measuring device of a vertical glass edging machine disclosed by the invention, has the advantages of simple mechanism, low cost and high thickness measuring precision; and a contact bearing contacts with a glass surface to effectively protect a coating film. The thickness measuring device is installed on a panel on an inlet side of the rack glass of the edging machine to ensure that the position of the grinding wheel can be accurately controlled and regulated in time.

The invention relates to a bilateral malposed differential confocal lens central thickness measurement method and belongs to the technical field of optical precision measurement. According to the invention, in a confocal measurement system, firstly, big and small virtual pinhole detection regions are set by software on an Ellie spot image detected by a CCD and two confocal characteristic curves detected by the big and small virtual pinhole detection regions are sharpened by subtraction processing; secondly, the sharpened confocal characteristic curves are subjected to bilateral malposed differential subtraction processing to obtain axial highly-sensitive differential confocal characteristic curves; then by utilizing the characteristic that zero points of the bilateral malposed differentialconfocal characteristic curves accurately correspond to a focus of the confocal measurement system, high-accuracy fixed-focus locating is carried out on a central thickness measurement vertex position of a measured lens; and finally, by ray tracing compensation calculation, a central thickness of the lens is accurately obtained so as to implement high-accuracy measurement on the central thicknessof the lens. The bilateral malposed differential confocal lens central thickness measurement method has the advantages of high measurement accuracy, high resistance to environment interference, simple structure and the like, and has wide application prospect in the technical field of optical precision measurement.

The invention discloses an electromagnetic ultrasonic transverse wave thickness measuring probe. The probe comprises a shell unit; two magnets set inside the shell unit; an excitation receiving unit which comprises two L-shaped coil frameworks arranged on the two outer sides of the shell unit, two coils fixed to the bottom faces of the L-shaped coil frameworks and correspond to the positions of the magnets respectively, springs which are arranged at the positions, making contact with the shell unit, of the side faces of the L-shaped coil frameworks, and adjusting bolts which are used for fixing the L-shaped coil frameworks and the side surfaces of the shell unit and can adjust the length screwed into the shell unit; the springs are used for pressing the heads of the adjusting bolts and theL-shaped coil frameworks; one end of each of the two coils is connected with an electromagnetic ultrasonic instrument at the same time, and the two coils are used for receiving excitation signals input by the electromagnetic ultrasonic instrument and feeding back echo signals to the electromagnetic ultrasonic instrument so that the electromagnetic ultrasonic instrument can determine the thicknessof a measured component according to the echo signals. The thickness measuring precision can be improved.

The invention provides a coating device which comprises a first ring body, a second ring body and a cross-shaped ruler, the first ring body is provided with a through hole, and the cross-shaped ruler is arranged in the middle of the through hole. The cross-shaped scale is provided with a central origin part, a first positive-axis scale part, a first negative-axis scale part, a second positive-axis scale part and a second negative-axis scale part, and is provided with a first side and a second side; scales are arranged on the first side of the cross-shaped ruler; the center original point part, the first positive-axis scale part, the first negative-axis scale part, the second positive-axis scale part and the second negative-axis scale part are flush on the second side of the cross-shaped scale, and the side faces, parallel to the thickness direction of the first ring body, of the first positive-axis scale part, the first negative-axis scale part, the second positive-axis scale part and the second negative-axis scale part are straight. The second ring body and the first ring body are stacked and connected together in the thickness direction of the first ring body; the second ring body is provided with an accommodating part which is used for the wafer. Therefore, the thickness measurement precision of the coating film can be improved.