JP2015052480A - Geometric quantity measuring apparatus and geometric quantity measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a geometric quantity measuring apparatus capable of measuring geometric quantity by using a relatively small reference gauge.SOLUTION: A geometric quantity measuring apparatus 50 for measuring straightness of a workpiece W comprises three distance sensors 9A, 9B and 9C of a first group, which are arranged on a predetermined straight line with a first distance L1 from each other, a sensor head 9 having three distance sensors 9a, 9b and 9c of a second group, which are arranged on the predetermined straight line with a second distance D1 from each other shorter than the first distance L1, and an actuator 8 for table movement which relatively moves the sensor head 9 to the workpiece W along the predetermined straight line.

Description

  The present invention relates to a geometric amount measuring apparatus and a geometric amount measuring method for measuring a geometric amount that is a magnitude of deviation from a reference geometric shape, such as straightness and flatness of an object to be measured.

  Conventionally, a reference gauge having a known shape is used to measure the relative height error at the origins of the three sensors to calibrate the three sensors, and the three sensors that are calibrated and the three-point method are used sequentially. A method for determining the straightness of a measurement object is known (see, for example, Patent Documents 1 and 2).

JP 2010-181195 A JP 2010-197350 A

  However, the larger the size of the reference gauge, the more complicated the manufacture and handling, and the greater the influence of temperature, gravity, etc., the worse the reproducibility.

  In view of the above, there is a need for a geometric amount measuring apparatus and a geometric amount measuring method that can measure a geometric amount using a relatively small reference gauge.

  A geometric amount measuring apparatus according to an embodiment of the present invention is a geometric amount measuring apparatus that measures a geometric amount that is a magnitude of deviation from a reference geometric shape of an object to be measured. At least three first group distance meters arranged at a first distance on a straight line and at least three second group distance meters arranged at a second distance smaller than the first distance on the predetermined line; And a moving mechanism for moving the distance meter support relative to the object to be measured along the predetermined straight line.

  Further, the geometric amount measuring method according to the embodiment of the present invention is a geometric amount measuring method for measuring a geometric amount which is a magnitude of deviation from a reference geometric shape of an object to be measured. , At least three first group distance meters arranged at a first distance on a predetermined straight line, and at least three second group distances arranged at a second distance smaller than the first distance on the predetermined straight line. A distance meter support having a meter and at least one of the objects to be measured are moved such that the distance meter support moves relative to the object to be measured along the predetermined straight line. A moving step, a calibration step of calibrating the at least three second group distance meters using a reference gauge having a known surface shape, and a three-point method or sequential using outputs of the at least three second group distance meters The object to be measured by the three-point method A surface shape deriving step for deriving a surface shape having a length at least twice as long as the first distance, and zero points of the at least three first group distance meters based on the surface shape derived in the surface shape deriving step A zero error determination step for determining an error, and a zero error correction step for correcting a zero error of the at least three first group distance meters by averaging a plurality of zero errors obtained by repeating the zero error determination step a plurality of times And surface shape derivation for deriving the surface shape of the object by the three-point method or the sequential three-point method using the outputs of the at least three first group distance meters whose zero-point errors have been corrected in the zero-point error correction step. Steps.

  By the above-mentioned means, a geometric amount measuring apparatus and a geometric amount measuring method capable of measuring a geometric amount using a relatively small reference gauge are provided.

It is a front view of the surface grinder by which the geometric amount measuring apparatus which concerns on the Example of this invention is mounted. It is a right view of the surface grinder of FIG. It is a bottom view (the 1) of a sensor head. It is a functional block diagram which shows the structural example of the geometric amount measuring apparatus which concerns on the Example of this invention. It is a flowchart which shows the flow of a geometric amount measurement process. It is a figure which shows the positional relationship of a sensor head and a workpiece | work when a sensor head moves relatively with respect to a workpiece | work. It is a table | surface which shows the relationship between the various parameters and various calculation values which a geometric amount measuring apparatus utilizes. It is a bottom view (the 2) of a sensor head.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a front view of a surface grinding machine 100 on which a geometric amount measuring apparatus according to an embodiment of the present invention is mounted, and FIG. 2 is a right side view thereof. The surface grinding machine 100 is mainly composed of a main body bed 1, an X-axis table 2, a vertical-grinding wheel column 3, a vertical-shaft grinding wheel head 4, a grinding wheel head rotating motor 5, a grinding wheel head vertical feed actuator 6, and a grinding wheel head left and right feeding actuator. 7, a table moving actuator 8, a sensor head 9, a display device 10, an input device 11, a control device 12, and a reference gauge 13.

  The main body bed 1 is a pedestal that supports the X-axis table 2 so as to be movable in the X-axis direction. Specifically, the main body bed 1 has a pinion (not shown) that engages with a rack (not shown) attached to the lower surface of the X-axis table 2 on its upper surface.

  The X-axis table 2 is a table that is slid in the X-axis direction on the main body bed 1 by a drive mechanism (not shown), and a workpiece W (for example, a surface plate) that is an object to be ground on its upper surface and is an object to be measured. ). In this embodiment, the X-axis table 2 is driven by a rack and pinion mechanism, but may be driven by another driving mechanism such as a ball screw mechanism.

  The vertical axis grinding wheel column 3 is a device that supports the vertical axis grinding wheel head 4 so as to be movable in the vertical direction (Z-axis direction) and the horizontal direction (Y-axis direction).

  The vertical axis grindstone head 4 is a grindstone head having a grindstone shaft 40 extending in parallel to the vertical direction (Z-axis direction). A grinding wheel 41 is attached to the tip of the grinding wheel shaft 40.

  The grindstone head rotating motor 5 is a motor that rotates the grindstone shaft 40 of the vertical-shaft grindstone head 4, and an AC servomotor is used, for example.

  The grinding wheel head vertical feed actuator 6 is an actuator that drives a vertical movement mechanism for moving the vertical grinding wheel head 4 in the Z-axis direction. In the present embodiment, the grinding wheel head vertical feed actuator 6 is an AC servo motor for rotating a ball screw shaft or a ball screw nut in a ball screw mechanism. Then, as indicated by an arrow AR1 in FIG. 1, the vertical grinding wheel head 4 is moved in the Z-axis direction.

  The grinding wheel head left / right feeding actuator 7 is an actuator that drives a left / right moving mechanism for moving the vertical grinding wheel head 4 in the Y-axis direction. In this embodiment, the grinding wheel head left / right feed actuator 7 is an AC servo motor for rotating a ball screw shaft or a ball screw nut in a ball screw mechanism. Then, as indicated by an arrow AR2 in FIG. 2, the vertical axis grinding wheel head 4 is moved in the Y-axis direction.

  The table moving actuator 8 is an actuator that drives a table moving mechanism for moving the X-axis table 2 in the X-axis direction. In this embodiment, the table moving actuator 8 is an AC servomotor for rotating a ball screw shaft or a ball screw nut in a ball screw mechanism. Then, as indicated by an arrow AR3 in FIG. 1, the X-axis table 2 is moved in the X-axis direction.

  Note that the vertical movement mechanism, the horizontal movement mechanism, and the table movement mechanism may be other mechanisms such as a rack and pinion mechanism.

  The sensor head 9 is a distance meter support that supports a distance meter for measuring the straightness or flatness of the surface of the workpiece W after grinding as an object to be measured, and is attached to the vertical axis grinding stone head 4. In addition, the sensor head 9 is disposed at least three first group distance meters disposed on a straight line parallel to the X axis by a first distance when viewed from above and at a second distance on the same straight line. And at least three second group distance meters. The distance meter constituting the first group distance meter and the second group distance meter may be a non-contact type distance meter such as an optical type, an ultrasonic type, or a laser type, and a contact type such as a transformer type or a scale type. It may be a distance meter. Further, each of the distance meters constituting each group may be the same type or different types. Further, each of the non-contact type distance meters may be attached to the sensor head 9 so that the distance to the surface of the object to be measured is substantially the same according to the effective measurement range or the like. You may attach to the sensor head 9 so that the distance between the surfaces of an object may differ. In the present embodiment, the sensor head 9 includes three first group distance sensors 9A, 9B, 9C that are spaced apart by a first distance, and three that are spaced by a second distance that is smaller than the first distance. Second group distance sensors 9a, 9b and 9c are included. The first group distance sensor 9A and the second group distance sensor 9a are the same one distance sensor.

  The sensor head 9 is detachably attached to the vertical axis grindstone head 4 using a permanent magnet or the like. However, the present invention is not limited to this. For example, the sensor head 9 may be attached to the vertical grinding wheel head 4 in a non-detachable manner. In this case, the sensor head 9 is covered with a dedicated cover when being ground by the surface grinder 100 and is isolated from the external environment.

  FIG. 3 is a bottom view of the sensor head 9 when the sensor head 9 is viewed from the vertically lower side (−Z direction), and shows four arrangement examples of distance sensors.

  In the present embodiment, the distance sensor is a non-contact type laser displacement meter, and the projection beam of the laser displacement meter adopts a line beam shape. Further, the extending direction of the line beam shape is inclined with respect to each of the X-axis direction and the Y-axis direction. In this embodiment, an angle of 45 degrees is formed with respect to each of the X-axis direction and the Y-axis direction. However, the present invention is not limited to this. For example, the extending direction of the line beam shape may be parallel to the X axis or the Y axis. Further, the projected beam of the laser displacement meter may have a spot shape.

  In the first stage of FIG. 3, the sensor head 9 includes three rod-shaped main body portions 9 s and three main body portions 9 s arranged on the straight line parallel to the X axis when viewed from above with a first distance L1. The first group distance sensors 9A, 9B, and 9C, and the three second group distance sensors 9a, 9b, and 9c arranged on the main body portion 9s at intervals of the second distance D1 (<L1) on the same straight line; including. The first group distance sensor 9A and the second group distance sensor 9a are the same one distance sensor. Therefore, the first-stage sensor head 9 in FIG. 3 includes five distance sensors.

  Further, in the second stage of FIG. 3, the sensor head 9 is disposed on the main body 9s at a first distance L1 on a straight line parallel to the X axis when viewed from above and the bar-shaped main body 9s. Three first group distance sensors 9A, 9B, 9C, and three second group distance sensors 9a, 9b, which are arranged on the main body 9s at intervals of the second distance D1 (<L1) on the same straight line. 9c. The first group distance sensor 9A and the second group distance sensor 9a are the same one distance sensor, and the first group distance sensor 9B and the second group distance sensor 9c are the same one distance sensor. Therefore, the sensor head 9 includes four distance sensors in the second stage sensor head 9 of FIG.

  In the third stage of FIG. 3, the sensor head 9 is disposed on the main body 9s at a first distance L1 on a bar-shaped main body 9s and a straight line parallel to the X axis in a top view. Three first group distance sensors 9A, 9B, 9C, and three second group distance sensors 9a, 9b, which are arranged on the main body 9s at intervals of the second distance D1 (<L1) on the same straight line. 9c. The first group distance sensor 9B and the second group distance sensor 9b are the same one distance sensor. Therefore, the third-stage sensor head 9 in FIG. 3 includes five distance sensors.

  In the fourth stage of FIG. 3, the sensor head 9 is spaced by a first distance L1 on a straight body parallel to the X axis when viewed from the top, with a rod-shaped main body 9s and a rod-shaped main body extension 90s. Three first group distance sensors 9A, 9B, and 9C arranged on the main body 9s are arranged on the main body 9s and the main body extension 90s with a second distance D1 (<L1) on the same straight line. Second group distance sensors 9a, 9b and 9c. The first group distance sensor 9A and the second group distance sensor 9c are the same one distance sensor. Therefore, the fourth-stage sensor head 9 in FIG. 3 includes five distance sensors. The main body extension 90s is a member that is detachably attached to the main body 9s in a state where the second group distance sensors 9a and 9b are mounted.

  Here, referring to FIGS. 1 and 2 again, the description of the components of the surface grinding machine 100 will be continued.

  The display device 10 is a device for displaying various information, and is, for example, a liquid crystal display.

  The input device 11 is a device for inputting various information to the surface grinding machine 100, and is, for example, a keyboard, a touch panel, a joystick, a remote controller, or the like.

  The control device 12 is a device for controlling the movement of the surface grinding machine 100, and includes, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a non-volatile random access (NVRAM). Memory) and the like.

  The reference gauge 13 is a reference gauge used for calibration of the distance meter, and has a known surface shape. In this embodiment, the reference gauge 13 is used for calibration (correction of zero point error) of the second group distance sensors 9a, 9b, 9c arranged at intervals of the second distance, and the first gauge larger than the second distance. The first group distance sensors 9A, 9B, 9C arranged at intervals are not used for calibration (zero error correction). Therefore, the length of the reference gauge 13 in the X-axis direction has a minimum length necessary for calibration (correction of zero point error) of the second group distance sensors 9a, 9b, 9c. In this embodiment, the length of the reference gauge 13 in the X-axis direction corresponds to twice the length of the second distance D1, which is the distance between the second group distance sensors, and is the distance between the first group distance sensors. The distance is shorter than twice the distance L1.

  FIG. 4 is a functional block diagram showing a configuration example of the geometric amount measuring apparatus 50 mounted on the surface grinding machine 100. As shown in FIG. The geometric amount measuring device 50 mainly includes a grinding wheel head rotating motor 5, a grinding wheel head vertical feed actuator 6, a grinding wheel head lateral feed actuator 7, a table moving actuator 8, a sensor head 9, a display device 10, and an input device. 11 and a control device 12.

  The control device 12 includes, for example, a grinding control unit 120, a geometric amount measurement control unit 121, and a zero point error determination unit 122 as functional elements. And the control apparatus 12 reads the program corresponding to each functional element from ROM, loads it to RAM, and makes CPU perform the process corresponding to each functional element.

  The grinding control unit 120 is a functional element that controls grinding of the workpiece W by the surface grinding machine 100. Specifically, the grinding control unit 120 determines the operation content of the vertical grinding wheel head 4 with respect to the workpiece W based on various information such as a grinding depth and a grinding width input through the input device 11. Then, the grinding control unit 120 sends a control signal according to the determined operation content at an appropriate timing to the grinding wheel head rotating motor 5, the grinding wheel head vertical feed actuator 6, the grinding wheel head left / right feeding actuator 7, and the table moving actuator. 8, the grinding of the workpiece W by the surface grinding machine 100 is controlled.

  The geometric quantity measurement control unit 121 is a functional element that controls the measurement of the geometric quantity of the workpiece W by the geometric quantity measurement device 50. In this embodiment, the geometric amount measurement control unit 121 determines the operation content of the sensor head 9 with respect to the workpiece W based on various information such as a measurement range and a sampling interval input through the input device 11. Then, the geometric amount measurement control unit 121 sends a control signal corresponding to the determined operation content to each of the grinding wheel head vertical feed actuator 6, the grinding wheel head horizontal feed actuator 7, and the table moving actuator 8 at an appropriate timing. While outputting, the sensor head 9 is moved relative to the workpiece W. The geometric amount measurement control unit 121 acquires distance data using a distance sensor during the relative movement, and records the acquired distance data in the RAM of the control device 12. Thereafter, the geometric amount measurement control unit 121 measures (calculates) the geometric amount of the workpiece W based on the distance data recorded in the RAM. The geometric amount measurement control unit 121 may start calculating the geometric amount after recording all the distance data necessary for calculating the geometric amount of the workpiece W. The intermediate calculation may be started as soon as the distance data necessary for the intermediate calculation included in is acquired. In this embodiment, the geometric amount measurement control unit 121 measures the straightness of the workpiece W by the three-point method or the sequential three-point method based on the distance data acquired by the first group distance sensors 9A, 9B, and 9C. To do.

  Here, with reference to FIG. 5, a process in which the geometric amount measuring apparatus 50 measures the geometric amount of the workpiece W (hereinafter referred to as “geometric amount measurement process”) will be described. FIG. 5 is a flowchart showing the flow of the geometric quantity measurement process. The geometric quantity measurement apparatus 50 performs the geometric quantity measurement according to, for example, a geometric quantity measurement process start command through the input device 11. Execute the process.

  First, the geometric amount measurement control unit 121 of the control device 12 acquires a measurement range and a sampling interval input through the input device 11 (step S1).

  The measurement range is a range on the workpiece W to be subjected to the geometric amount measurement process, and is specified by, for example, the start coordinate Ps (Xs, Ys) and the end coordinate Pe (Xe, Ye). Further, the measurement range may be specified by the measurement length X1 and the measurement width Y1.

  The sampling interval is a sampling interval by each distance sensor and corresponds to the measurement resolution dx in the X-axis direction. In the present embodiment, the sampling interval is, for example, 10 [mm].

  Thereafter, the geometric amount measurement control unit 121 determines the coordinates (Xt, Yt) of the reference position of the sensor head 9 based on the measurement range, and moves the sensor head 9 to the reference position (step S2). Specifically, the geometric amount measurement control unit 121 outputs a control signal to at least one of the grinding wheel head left-right feeding actuator 7 and the table moving actuator 8, and at least the sensor head 9 and the X-axis table 2. One is driven to move the sensor head 9 to the reference position.

  Thereafter, the geometric amount measurement control unit 121 determines a measurement distance along the X-axis direction based on the measurement range, and then outputs a control signal to the table moving actuator 8 and the sensor head 9. Then, the X-axis table 2 (work W) is moved in the + X direction by the measurement distance. During this movement, each of the five distance sensors 9a (9A), 9b, 9c, 9B, and 9C in the sensor head 9 measures the distance at each sampling interval, and the distance data as the measurement result is stored in the RAM of the control device 12. (Step S3).

  Thereafter, when the sensor head 9 reaches the end of the measurement range in the X-axis direction, the geometric amount measurement control unit 121 performs the work by the three-point method or the sequential three-point method based on the distance data recorded in the RAM. The straightness of W is calculated (step S4).

  Thereafter, the geometric amount measurement control unit 121 outputs a control signal to the display device 10 to display the calculated straightness of the workpiece W on the display device 10.

  As described above, in this embodiment, the geometric amount measurement control unit 121 uses the three-point method or the sequential three-point method based on the distance data acquired by each of the first group distance sensors 9A, 9B, and 9C. The straightness of W is measured and displayed. Therefore, it is desirable that the zero error is removed in advance for each of the first group distance sensors 9A, 9B, and 9C.

  Therefore, for example, using a reference gauge whose surface shape F (x) is known, it is considered to obtain the second-order difference value of each distance data of the first group distance sensors 9A, 9B, 9C and remove the zero error. It is done.

The outputs m _9A , m _9B , and m _9C of the first group distance sensors 9A, 9B, and 9C at the positions x, x + L1, and x + 2 × L1 are expressed by equations (1) to (3), respectively, and are second-order differential values. _CG is represented by Formula (4).

なお、Ｌ１は第１群距離センサのセンサ間隔を表し、ｅ_ｚ（ｘ）はＺ方向並進誤差を表し、ｅｐ（ｘ）はピッチング誤差を表す。また、α_９Ｂは第１群距離センサ９Ａから見た第１群距離センサ９Ｂの零点誤差を表し、α_９Ｃは第１群距離センサ９Ａから見た第１群距離センサ９Ｃの零点誤差を表す。

L1 represents the sensor interval of the first group distance sensor, e _z (x) represents the Z direction translation error, and ep (x) represents the pitching error. Α _9B represents the zero point error of the first group distance sensor 9B viewed from the first group distance sensor 9A, and α _9C represents the zero point error of the first group distance sensor 9C viewed from the first group distance sensor 9A.

When the surface shape F (x) is known, alpha _9B based on the above equation (1) to _(4), alpha _9C is derived, obtained by second order integrating the second difference value C _G shape ( A quadratic curve error) is derived as an error shape due to a zero point error. As a result, the influence of the error shape, that is, the zero point error can be removed from any surface shape derived using the outputs of the first group distance sensors 9A, 9B, and 9C and the three-point method or the sequential three-point method.

  However, as the first distance L1, which is the distance (sensor pitch) between the first group distance sensors, is larger, it is more difficult to prepare a reference gauge necessary for calibration (correction of zero error) of the first group distance sensors. become. This is because it is difficult to ensure the reproducibility of the surface shape F (x). Specifically, the larger the reference gauge, the greater the influence of thermal expansion on the temperature change. Also, the larger the reference gauge, the greater the influence of gravity, and it becomes difficult to ensure reproducibility depending on the installation method. In addition, there is a practical problem that the larger the reference gauge, the more difficult the relocation and transportation.

  Thus, it is not realistic to prepare a reference gauge that can calibrate (correct zero point error) the first group distance sensor having a large sensor pitch. Therefore, the geometric amount measuring apparatus 50 enables the zero point error determination unit 122 to calibrate the first group distance sensors 9A, 9B, and 9C (correct the zero point error) without using a large reference gauge.

  The zero point error determination unit 122 is a functional element that determines the zero point error of the first group distance meter. In the present embodiment, the zero point error determination unit 122 uses the surface shape F (x) of the workpiece W derived using the outputs of the second group distance sensors 9a, 9b, 9c and the three-point method or the sequential three-point method. The zero point errors of the first group distance sensors 9A, 9B, 9C are determined. In the second group distance sensors 9a, 9b, 9c, the zero point error is corrected (removed) using the reference gauge 13. This is because the sensor pitch is smaller than those of the first group distance sensors 9A, 9B, and 9C, and the length of the reference gauge 13 is relatively short. However, the second group distance sensors 9a, 9b, and 9c may correct the zero point error using a known calibration method other than the calibration method using the reference gauge 13.

Then, the zero point error determination unit 122 determines the zero point error of the first group distance sensor while using the workpiece W longer than the reference gauge 13 as a large reference gauge. Specifically, the zero-point error determination unit 122 uses the surface shape F (x) of the workpiece W as a large reference gauge, and the second-order difference value of each distance data of the first group distance sensors 9A, 9B, 9C. To eliminate the zero error. This second-order difference value _CW is expressed by Expression (5).

なお、Ｅｒｒ（ｘ）は、ワークＷの表面形状を導き出すための３点法又は逐次３点法に基づく演算の際に第２群距離センサ９ａ、９ｂ、９ｃの測定分解能レベルの偶然誤差が積算されて拡大された量である。また、第２群距離センサ９ａ、９ｂ、９ｃのそれぞれの偶然誤差が正規分布にしたがう場合、それらの加減算によって導出されるＥｒｒ（ｘ）の値も正規分布にしたがう。

Note that Err (x) is calculated by integrating a random error of the measurement resolution levels of the second group distance sensors 9a, 9b, and 9c in the calculation based on the three-point method or the sequential three-point method for deriving the surface shape of the workpiece W. The amount that has been expanded. In addition, when the random errors of the second group distance sensors 9a, 9b, and 9c follow a normal distribution, the value of Err (x) derived by adding and subtracting them also follows the normal distribution.

Here, when the difference between the second difference value C _G shown in Equation second difference value shown in (5) C _W and the formula (4) and second difference values C _T, second difference value C _T, the following equation (6 ).

なお、二階差分値Ｃ_Ｔは、第１群距離センサ９Ａ、９Ｂ、９Ｃのそれぞれの零点からの誤差量の二階差分値を表す。また、二階差分値Ｃ_Ｔでは、第２群距離センサ９ａ、９ｂ、９ｃの測定分解能レベルの偶然誤差が３点法又は逐次３点法に基づく演算の際に拡大されることによって増大する偶然誤差Ｅｒｒ（ｘ）による影響が大きい。一方で、零点誤差α_９Ｂ、α_９Ｃは、測定値のドリフトが生じない限り、位置ｘによらず一定である。そのため、距離の測定が行われる位置ｘ毎に二階差分値Ｃ_Ｔを導き出して平均化することで、偶然誤差Ｅｒｒ（ｘ）を低減させることができる。なお、平均化できる回数をｍ回とすると、偶然誤差Ｅｒｒ（ｘ）は、１／√ｍ倍まで低減される。式（７）は、平均化できる回数ｍの算出方法を表す。なお、Ｗ１は、ワークＷのＸ軸方向の長さを表し、ｄｘは、Ｘ軸方向の測定分解能を表す。

Incidentally, second difference value C _T represents the first group distance sensor 9A, 9B, the second difference value of the error amount from the respective zero point of 9C. Further, the second difference value C _T, the second group distance sensors 9a, 9b, accidental errors random errors of measurement resolution levels 9c is increased by being enlarged in the calculation based on the three-point method or sequential three-point method The effect of Err (x) is large. On the other hand, the zero point errors α _9B and α _9C are constant regardless of the position x unless the measured value drifts. Therefore, for each position x of the distance measurements are carried out by averaging derive second difference value C _T, it is possible to reduce the random error Err (x). If the number of times that averaging can be performed is m, the chance error Err (x) is reduced to 1 / √m times. Expression (7) represents a calculation method of the number m of times that can be averaged. W1 represents the length of the workpiece W in the X-axis direction, and dx represents the measurement resolution in the X-axis direction.

このように、ｍ回の平均化によって式（６）における偶然誤差Ｅｒｒ（ｘ）が低減されることで、偶然誤差Ｅｒｒ（ｘ）の影響を抑えた状態で式（６）における零点誤差α_９Ｂ、α_９Ｃが導き出される。また、偶然誤差Ｅｒｒ（ｘ）の影響を抑えた状態の二階差分値Ｃ_Ｔを二階積分して得られる形状（２次曲線誤差）が零点誤差による誤差形状として導き出される。

In this way, the accidental error Err (x) in the equation (6) is reduced by m times of averaging, so that the zero point error α _9B in the equation (6) is suppressed in a state where the influence of the accidental error Err (x) is suppressed. , Α _9C is derived. Also, second-order differential value C _T a second order integration to obtain the shape of the state of suppressing the influence of the random error Err (x) (2 quadratic curve error) is derived as the error shape by zero error.

  The geometric amount measurement control unit 121 corrects the zero point error by removing this error shape from the surface shape of the workpiece W derived by the three-point method or the sequential three-point method in step S4 described above, and then corrects the workpiece W. Calculate the straightness of.

  Next, with reference to FIG. 6, a process in which the geometric quantity measuring device 50 measures the straightness of the workpiece W will be described. FIG. 6 is a view of the sensor head 9 and the workpiece W as viewed from the + Y side. The positional relationship between the sensor head 9 and the workpiece W when the sensor head 9 moves relative to the workpiece W in the −X direction. Indicates. FIG. 6 shows that the positional relationship shifts from the first stage (uppermost stage) to the fifth stage (lowermost stage) with the passage of time. In the present embodiment, the work W actually moves in the + X direction.

  In the present embodiment, the length W1 of the workpiece W in the X-axis direction is 10000 [mm], and the first distance (sensor pitch) L1 that is the distance between the first group distance sensors 9A, 9B, and 9C is 1000 [ mm], and the second distance (sensor pitch) D1 that is the distance between the second group distance sensors 9a, 9b, 9c is 200 [mm]. The measurement by each distance sensor is performed every time the relative movement distance of the sensor head 9 in the X-axis direction reaches the distance dx as the measurement resolution, and the measurement resolution dx is 10 [mm].

  The first row in FIG. 6 shows a state when the first (first) measurement is performed by the first group distance sensors 9A, 9B, and 9C. At this time, the measurement point by the distance sensor 9A (9a) is at the + X side end point of the workpiece W, and the measurement point by the distance sensor 9B is 1000 mm away from the + X side end point of the workpiece W in the −X direction. The measurement point by the distance sensor 9C is at a point away from the end point on the + X side of the workpiece W by 2000 [mm] in the −X direction. However, at this time, the derivation of the shape of the workpiece W using the measurement values of the second group distance sensors 9a, 9b, and 9c and the three-point method or the sequential three-point method has not been performed yet. In the first row of FIG. 6, the measurement points of the first group distance sensors 9A, 9B, and 9C are represented by white circles on the surface of the workpiece W. The same applies to the second and subsequent stages in FIG.

  The second row in FIG. 6 shows a state when the 200th measurement is performed by the first group distance sensors 9A, 9B, and 9C. At this time, the measurement point by the distance sensor 9A (9a) is located at a point away from the end point on the + X side of the workpiece W by 2000 [mm] in the −X direction. At this time, the geometric amount measuring apparatus 50 uses the measured values of the second group distance sensors 9a, 9b, and 9c and the three-point method or the sequential three-point method from the end point on the + X side of the workpiece W. Surface shapes up to a point of 2000 [mm] can be derived. Then, the geometric amount measuring apparatus 50 is based on the derived surface shape of the workpiece W and the measured values of the first group distance sensors 9A, 9B, and 9C in the first measurement (first stage in FIG. 6). Thus, the first zero error derivation process can be executed. That is, the geometric amount measuring apparatus 50 can execute the zero point error deriving process only when the sensor head 9 is relatively moved by 2000 [mm]. The zero point error deriving process means a calculation process for deriving the zero point errors of the first group distance sensors 9A, 9B, 9C. Further, in the second stage of FIG. 6, a portion of the surface shape of the workpiece W from which the surface shape is derived using the three-point method or the sequential three-point method is represented by a thick solid line. The same applies to the third and subsequent stages in FIG.

  The third row in FIG. 6 shows a state when the 201st measurement is performed by the first group distance sensors 9A, 9B, and 9C. At this time, the measurement point by the distance sensor 9A (9a) is located at a point away from the end point on the + X side of the workpiece W by 2010 [mm] in the −X direction. At this time, the geometric amount measuring apparatus 50 uses the measured values of the second group distance sensors 9a, 9b, and 9c and the three-point method or the sequential three-point method from the end point on the + X side of the workpiece W. The surface shape up to a point of 2010 [mm] can be derived. Then, the geometric quantity measuring device 50 is based on the derived surface shape of the workpiece W and the measured values of the first group distance sensors 9A, 9B, 9C in the second measurement (not shown). The second zero point error deriving process can be executed.

  The fourth row in FIG. 6 shows a state when the 202nd measurement is performed by the first group distance sensors 9A, 9B, and 9C. At this time, the measurement point by the distance sensor 9A (9a) is at a point away from the + X side end point of the workpiece W by 2020 [mm] in the −X direction. At this time, the geometric amount measuring apparatus 50 uses the measured values of the second group distance sensors 9a, 9b, and 9c and the three-point method or the sequential three-point method from the end point on the + X side of the workpiece W. The surface shape up to a point of 2020 [mm] can be derived. Then, the geometric amount measuring device 50 is based on the derived surface shape of the workpiece W and the measured values of the first group distance sensors 9A, 9B, 9C in the third measurement (not shown). A third zero error derivation process can be executed.

  As described above, the geometric amount measuring apparatus 50 moves the sensor head 9 relative to the distance dx (10 [mm]) corresponding to the measurement resolution after the sensor head 9 is relatively moved by 2000 [mm]. The zero point error deriving process can be executed.

  The fifth row in FIG. 6 shows a state when the 1000th measurement is performed by the first group distance sensors 9A, 9B, and 9C. At this time, the measurement point by the distance sensor 9A (9a) is at a point away from the + X side end point of the workpiece W by 10000 [mm] in the −X direction. At this time, the geometric amount measuring apparatus 50 uses the measured values of the second group distance sensors 9a, 9b, and 9c and the three-point method or the sequential three-point method from the end point on the + X side of the workpiece W. The entire surface shape up to the end point on the −X side can be derived. Then, the geometric amount measuring device 50 is based on the derived surface shape of the workpiece W and the measured values of the first group distance sensors 9A, 9B, 9C in the 800th measurement (not shown). The 801th zero error derivation process can be executed.

  Thereafter, the geometric amount measuring apparatus 50 averages the results obtained by the 801 zero error derivation process. Specifically, the zero point error determination unit 122 averages 801 zero point error amounts related to the first group distance sensor 9A to derive one average zero point error amount. The same applies to the first group distance sensors 9B and 9C.

  As described above, the geometric amount measuring apparatus 50 can execute 801 zero error derivation processing when a workpiece W having a length of 10000 [mm] is measured with a measurement resolution of 10 [mm]. Therefore, the geometric amount measuring apparatus 50 can reduce the random error included in each zero point error to about 1/28 (= 1 / √800) by averaging 800 times. This is because, for example, the sensor pitch of the second group distance sensors 9a, 9b, 9c is 200 [mm], and the sensor resolution (accuracy) in the Z-axis direction is 0.02 [μm]. Accumulated when deriving the surface shape of the workpiece W at a distance (2 × L1) corresponding to the distance between the first group distance sensors 9A and 9C by the output of the distance sensors 9a, 9b, 9c and the three-point method or the sequential three-point method. Assuming that the coincidence error is 0.32 [μm] at 3σ, it means that the coincidence error can be reduced to 0.011 [μm] at 3σ by averaging 800 times. That is, it is possible to obtain an effect equivalent to that obtained when a reference gauge that can ensure a reproducibility of 0.011 [μm] is used. As a result, the geometric amount measuring apparatus 50 has a sensor pitch of 1000 [mm] without using a relatively large reference gauge necessary for correcting the zero error of each of the first group distance sensors 9A, 9B, and 9C. In addition, the output of the first group distance sensors 9A, 9B, 9C having a sensor resolution (accuracy) in the Z-axis direction of 0.02 [μm] and a length of 10000 [mm] by the three-point method or the sequential three-point method The accidental error accumulated when deriving the surface shape of the workpiece W can be suppressed to 0.32 [μm] at 3σ.

  Thus, the geometric amount measuring apparatus 50 is necessary for the calibration of the second group distance sensors 9a, 9b, 9c without using a relatively large gauge necessary for the calibration of the first group distance sensors 9A, 9B, 9C. A zero error of the first group distance sensors 9A, 9B, 9C can be corrected with high accuracy using a relatively small gauge. In addition, the workpiece W (for example, several numbers) having a relatively large shape is obtained by using the outputs of the first group distance sensors 9A, 9B, and 9C in which the zero error is corrected in this way and the three-point method or the sequential three-point method. The straightness of the workpiece W) having a meter length can be calculated with high accuracy.

  Here, with reference to FIG. 7, the specific example of the effect by the geometric amount measuring apparatus 50 is demonstrated. FIG. 7 is a table showing the relationship between various parameters used by the geometric quantity measuring apparatus 50 and various calculated values.

Figure 7 shows a first group distance sensor 9A, 9B, precision sigma ₁ of 9C, and, second group range sensors 9a, 9b, the 9c precision sigma ₂ is respectively 0.01 [μm]. Further, the distance (sensor pitch) L1 between the first group distance sensors 9A, 9B, 9C is 1000 [mm], and the distance (sensor pitch) D1 between the second group distance sensors 9a, 9b, 9c is 200 [mm]. Indicates that there is. Further, the length W1 in the X-axis direction of the workpiece W to be measured is 10000 [mm], and the measurement resolution dx in the X-axis direction is 10 [mm].

In this case, the coincidence error σ _N2 of the measured value of the surface shape of the workpiece W derived using the outputs of the second group distance sensors 9a, 9b, 9c and the three-point method or the sequential three-point method is expressed by the following equation: It is represented by (8). Incidentally, the chance error σ _N2 is caused by propagation of the chance error of each sensor resolution level of the second group distance sensors 9a, 9b, 9c in the surface shape of the workpiece W derived by the three-point method or the sequential three-point method. This is an increased chance error. Further, the accidental error σ _N2 becomes 0.159 [μm] when the above-described parameter values are substituted.

そして、偶然誤差σ_Ｎ２は、式（７）によって求められるｍ回の平均化によって、式（９）に示すように、平均化後偶然誤差σ_Ｎ２Ｘとなる。また、平均化後偶然誤差σ_Ｎ２Ｘは、上述のパラメータの値を代入すると、０．００６［μｍ］となる。

The random error sigma _N2 is the m times of averaging as determined by equation (7), as shown in equation (9), and after averaging random error sigma _N2X. Further, the accidental error σ _N2X after averaging becomes 0.006 [μm] when the above-described parameter values are substituted.

また、第１群距離センサ９Ａ、９Ｂ、９Ｃのそれぞれに関する零点誤差と偶然誤差とを重ね合わせた重ね合わせ誤差σ_９Ａ、σ_９Ｂ、σ_９Ｃは、以下の式（１０）で表される。また、重ね合わせ誤差σ_９Ａ、σ_９Ｂ、σ_９Ｃは、上述のパラメータの値を代入すると、０．０１１［μｍ］となる。

Further, superposition errors σ _9A , σ _9B , and σ _{9C obtained} by superimposing the zero point error and the chance error on each of the first group distance sensors 9A, 9B, and 9C are expressed by the following formula (10). The overlay errors σ _9A , σ _9B , and σ _9C are 0.011 [μm] when the values of the above parameters are substituted.

また、第１群距離センサ９Ａ、９Ｂ、９Ｃのそれぞれで検出可能な最小高さｈは、以下の式（１１）で表される。また、最小高さｈは、上述のパラメータの値を代入すると、０．２８７［μｍ］となる。

Further, the minimum height h that can be detected by each of the first group distance sensors 9A, 9B, and 9C is expressed by the following formula (11). Moreover, the minimum height h is 0.287 [μm] when the above-described parameter values are substituted.

また、第１群距離センサ９Ａ、９Ｂ、９Ｃのそれぞれの出力と３点法又は逐次３点法とを用いて導き出されるワークＷの表面形状の偶然誤差σ_Ｎ１は、式（８）に示す第２群距離センサに関する偶然誤差σ_Ｎ２と同様、以下の式（１２）で表される。また、偶然誤差σ_Ｎ１は、上述のパラメータの値を代入すると、０．０９１［μｍ］となる。

Further, the random error σ _N1 of the surface shape of the workpiece W derived by using the outputs of the first group distance sensors 9A, 9B, 9C and the three-point method or the sequential three-point method is expressed by the equation (8). Similar to the accidental error σ _N2 related to the second group distance sensor, it is expressed by the following equation (12). Further, the accidental error σ _N1 becomes 0.091 [μm] when the above-described parameter values are substituted.

なお、第１群距離センサ９Ａの精度σ_１、第２群距離センサ９Ａの精度σ_２、第１群距離センサ９Ａの間隔Ｌ１、第２群距離センサ９Ａの間隔Ｄ１、ワークＷの長さＷ１、Ｘ軸方向の測定分解能ｄｘ等のパラメータは、以下のように決定される。すなわち、形状測定における分解能の仕様そのものとなる検出可能な最小高さｈ、及び、積算された偶然誤差σ_Ｎ１の値が最も小さくなるように決定される。

The accuracy σ ₁ of the first group distance sensor 9A, the accuracy σ _{2 of} the second group distance sensor 9A, the interval L1 of the first group distance sensor 9A, the interval D1 of the second group distance sensor 9A, and the length W1 of the workpiece W The parameters such as the measurement resolution dx in the X-axis direction are determined as follows. That is, the minimum detectable height h that is the resolution specification itself in the shape measurement and the value of the accumulated coincidence error σ _N1 are determined to be the smallest.

  As described above, the geometric amount measuring apparatus 50 uses the three first group distance sensors 9A, 9B, and 9C arranged at a sensor pitch of 1 [m] (= 1000 [mm]), and is approximately 0.3. The straightness of the surface shape of the workpiece W having a length of 10 [m] (= 10000 [mm]) can be measured with a resolution of about [μm].

  With the above configuration, the geometric amount measuring apparatus 50 is a part of the surface shape of the workpiece W based on the output of the second group distance sensor calibrated using the reference gauge 13 and the three-point method or the sequential three-point method. To derive. Further, the geometric amount measuring apparatus 50 calibrates the first group distance sensor using a part of the derived surface shape of the workpiece W. Then, the geometric amount measuring apparatus 50 repeats derivation of a part of the surface shape of the workpiece W and calibration of the first group distance sensor, and averages the accidental errors included in the output of the first group distance sensor. The accidental error included in the output of the first group distance sensor is reduced. Then, the geometric amount measuring apparatus 50 derives the entire surface shape of the workpiece W based on the output of the first group distance sensor and the three-point method or the sequential three-point method in which the influence due to the accidental error is reduced. Specifically, the geometric amount measuring apparatus 50 removes an error shape caused by a zero point error from a shape derived by a three-point method or a sequential three-point method. As a result, the geometric amount measuring apparatus 50 can measure the straightness of the workpiece W having a relatively large shape with high accuracy using the relatively small reference gauge 13.

  For the same reason, the geometric amount measuring apparatus 50 allows the length of the reference gauge 13 used for calibration of the second group distance sensor to be not less than twice the second distance D1, which is the interval between the second group distance sensors. The length is shorter than twice the first distance L1, which is the interval between the first group distance sensors. As a result, the geometric amount measuring apparatus 50 can omit the reference gauge used for calibration of the first group distance sensor. Further, the geometric quantity measuring device 50 can promote the downsizing of the reference gauge 13 used for calibration of the second group distance sensor.

  Further, the geometric amount measuring apparatus 50 can reduce the influence of noise on the measurement value by adopting a laser displacement meter that emits a projection beam having a line beam shape as a distance sensor. This is because a value obtained by averaging the amount of displacement in the line beam having a predetermined width is output as a measurement value at a measurement point at the center of the line beam.

  Further, the geometric amount measuring apparatus 50 adopts a line beam shape inclined at 45 degrees with respect to each of the X-axis direction and the Y-axis direction, so that the influence of noise on the measurement value is measured in the X-direction measurement line and the Y-direction measurement It is possible to prevent biasing to any one of the lines. This is because the grinding mark, which is one of the causes of noise, is easily formed in the extending direction of the object to be measured or its orthogonal direction, that is, the direction parallel to the X axis or the Y axis.

  Next, another embodiment of the sensor head 9 will be described with reference to FIG. FIG. 8 is a bottom view of the sensor head 9 as viewed from three vertically lower structural examples (−Z direction) of the sensor head 9.

  The upper sensor head 9 in FIG. 8 includes a triangular prism main body 9s and three distance sensors 9A, 9B, and 9C arranged on the main body 9s with a distance Db in the direction parallel to the X axis. It includes three distance sensors 9a, 9b, 9c arranged on the main body 9s with a distance Da in the direction parallel to the Y axis. The distance sensor 9A and the distance sensor 9a are the same distance sensor. Therefore, the sensor head 9 includes five distance sensors. The distance Da and the distance Db may be the same value or different values.

  The sensor head 9 in the middle of FIG. 8 includes a main body portion 9s whose bottom surface is a cross-shaped polygonal column and three distance sensors 9A arranged on the main body portion 9s at intervals of a distance Db in a direction parallel to the X axis. , 9B, 9C, and three distance sensors 9a, 9b, 9c arranged on the main body portion 9s at intervals of a distance Da in a direction parallel to the Y axis. The distance sensor 9B and the distance sensor 9a are the same distance sensor. Therefore, the sensor head 9 in the middle stage of FIG. 8 includes five distance sensors, like the sensor head 9 in the upper stage of FIG. The distance Da and the distance Db may be the same value or different values.

  The lower sensor head 9 in FIG. 8 includes a main body portion 9s whose bottom surface is a polygonal column having a T-shape, and three distance sensors arranged on the main body portion 9s with a distance Db in the direction parallel to the X axis. 9A, 9B, and 9C, and three distance sensors 9a, 9b, and 9c arranged on the main body portion 9s at intervals of a distance Da in a direction parallel to the Y axis. The distance sensor 9B and the distance sensor 9a are the same distance sensor. Therefore, the lower sensor head 9 in FIG. 8 includes five distance sensors, similar to the upper and middle sensor heads 9 in FIG. The distance Da and the distance Db may be the same value or different values.

  In the three embodiments of FIG. 8, the five distance sensors are detachably attached to the main body 9s. Therefore, the same sensor arrangement as that of the sensor head 9 shown in the first row of FIG. 3 is obtained by removing the five distance sensors from the main body portion 9s and replacing them with a separately prepared rod-like main body portion as shown by a dotted line in FIG. Can be realized.

  The sensor head 9 of FIG. 8 includes at least three distance sensors arranged at equal intervals in a direction parallel to the X axis and at least three distance sensors arranged at equal intervals in a direction parallel to the Y axis. The measurement of the geometric amount of the workpiece W can be executed more efficiently.

  Specifically, the geometric amount measuring apparatus 50 acquires distance data while moving the sensor head 9 relative to the measurement range on the surface of the workpiece W. That is, the geometric amount measuring apparatus 50 includes distance data of measurement points arranged on each of a plurality of X direction measurement lines parallel to the X axis, and each of the plurality of Y direction measurement lines parallel to the Y axis. Get the distance data of the measurement points on the line. Therefore, the geometric amount measuring apparatus 50 can perform straightness measurement by the three-point method or the sequential three-point method for each of the plurality of X-direction measurement lines and the plurality of Y-direction measurement lines. Flatness measurement can be executed by the three-point method or the sequential three-point method based on the measurement lines arranged in a grid pattern on the surface of the workpiece W. As a result, the geometric amount measuring apparatus 50 can increase the measurement efficiency of the straightness and flatness of the workpiece W.

  As described above, the five distance sensors in FIG. 8 are interchanged between the main body portion and the rod-shaped main body portion in which three distance sensors can be arranged in a direction parallel to each of the X axis and the Y axis. Therefore, the user of the geometric amount measuring apparatus 50 uses the function realized by the main body as shown in FIG. 8 and the function realized by the rod-like main body as shown in FIG. be able to. That is, the user of the geometric amount measuring apparatus 50 can reduce the plurality of functions by preparing a plurality of relatively inexpensive main body portions and allowing the plurality of main body portions to use a relatively expensive distance sensor. Available at cost.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  For example, in the above-described embodiment, the geometric amount measuring apparatus 50 uses a first group distance sensor with a sensor pitch of 1000 [mm], and a workpiece having a length of 10,000 [mm] with a measurement resolution of 1000 [mm]. Measure the straightness of W. However, the present invention is not limited to this configuration. For example, the geometric amount measuring apparatus 50 uses a synthesis method to measure the straightness of a workpiece W having a length of 10,000 [mm] with a measurement resolution less than a sensor pitch such as 10 [mm] or 50 [mm], for example. May be.

  In the above-described embodiment, a configuration in which the sensor head 9 cannot be moved in the X-axis direction is employed. However, a configuration in which the sensor head 9 can be moved in the X-axis direction and the Y-axis direction may be employed.

  Similarly, in the above-described embodiment, the X-axis table 2 (work W) cannot be moved in the Y-axis direction. However, the X-axis table 2 (work W) is moved in the X-axis direction and the Y-axis direction. Possible configurations may be employed.

  Further, in the above-described embodiment, the grinding by the surface grinder 100 and the geometric amount measurement by the geometric amount measuring device 50 are both controlled by the control device 12, but may be controlled by separate control devices. Good. That is, the geometric amount measuring device 50 may include a dedicated control device that is independent from the control device of the surface grinding machine 100.

  In the above-described embodiment, each of the distance sensors mounted on the sensor head 9 measures the distance at a predetermined sampling interval and outputs the measured value. However, the present invention is not limited to this. Each of the distance sensors, for example, applies a low-pass filter or the like to collect a plurality of measurement values while continuously measuring the distance, and outputs the measurement values collected at a predetermined sampling interval. Also good.

  In the above-described embodiment, the geometric amount measuring device 50 is mounted on the surface grinder 100 including the vertical axis grindstone head 4, but may be mounted on the surface grinder including the horizontal axis grindstone head. Further, the geometric amount measuring apparatus 50 may be mounted on another machine tool including a mechanism for moving the sensor head 9 relative to the object to be measured at least in the X-axis direction.

  Moreover, although the geometric amount acquisition apparatus 50 was demonstrated as what is mounted in a surface grinder in the above-mentioned Example, you may mount in another machine tool. Specifically, the geometric amount acquisition apparatus 50 may be mounted on a semiconductor manufacturing apparatus, a liquid crystal panel manufacturing apparatus, or the like.

  DESCRIPTION OF SYMBOLS 1 ... Main body bed 2 ... X-axis table 3 ... Column for vertical-axis whetstone 4 ... Vertical-axis whetstone head 5 ... Motor for whetstone head rotation 6 ... Actuator for whetstone head vertical feed 7. -Grinding wheel head left-right feed actuator 8 ... Table movement actuator 9 ... Sensor head 9A, 9B, 9C ... First group distance sensor 9a, 9b, 9c ... Second group distance sensor 9s -Main body 10 ... Display device 11 ... Input device 12 ... Control device 13 ... Reference gauge 40 ... Grinding wheel shaft 41 ... Grinding wheel 50 ... Geometric measuring device 90s ..Main body extension unit 100 ... Surface grinding machine 120 ... Grinding control unit 121 ... Geometric amount measurement control unit 122 ... Zero error determination unit W ... Workpiece

Claims (6)

A geometric quantity measuring device for measuring a geometric quantity, which is a magnitude of deviation from a reference geometric shape of an object to be measured,
At least three first group distance meters arranged at a first distance on a predetermined straight line and at least three second group distance meters arranged at a second distance smaller than the first distance on the predetermined straight line. A distance meter support having:
A moving mechanism for moving the distance meter support relative to the object to be measured along the predetermined straight line;
Geometric measurement device. Having a reference gauge whose surface shape is known;
A length of the reference gauge is at least twice the second distance and less than twice the first distance;
The geometric amount measuring apparatus according to claim 1, wherein One or two of the at least three first group distance meters arranged at a distance of the first distance is one of at least three second group distance meters arranged at a distance of the second distance. One or two,
The geometric quantity measuring device according to claim 1 or 2, characterized by the above-mentioned. At least one of the at least three first group distance meters arranged at a distance of the first distance is detachable from the distance meter support;
The geometric quantity measuring device according to any one of claims 1 to 3, wherein At least one of at least three second group distance meters arranged at a distance of the second distance is detachable from the distance meter support;
The geometric amount measuring apparatus according to claim 1, wherein the geometric amount measuring apparatus is characterized in that: A geometric amount measuring method for measuring a geometric amount, which is a magnitude of deviation from a reference geometric shape of an object to be measured,
At least three first group distance meters arranged at a first distance on a predetermined straight line and at least three second group distance meters arranged at a second distance smaller than the first distance on the predetermined straight line. And a movement for moving at least one of the distance measuring object support and the object to be measured so that the distance measuring object support moves relative to the object to be measured along the predetermined straight line. Steps,
A calibration step of calibrating the at least three second group rangefinders using a reference gauge having a known surface shape;
A surface shape deriving step for deriving a surface shape at least twice as long as the first distance in the object to be measured by a three-point method or a sequential three-point method using outputs of the at least three second group distance meters; ,
A zero point error determining step of determining zero point errors of the at least three first group distance meters based on the surface shape derived in the surface shape deriving step;
A zero error correction step of correcting a zero error of the at least three first group distance meters by averaging a plurality of zero errors obtained by repeating the zero error determination step a plurality of times;
A surface shape deriving step for deriving a surface shape of the object to be measured by a three-point method or a sequential three-point method using outputs of the at least three first group distance meters whose zero-point errors have been corrected in the zero-point error correction step; ,
A geometrical amount measuring method comprising:

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