JPH071294A - Optical type work shape measuring device in numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To perform precise measurement of the shape of even a work formed in a complicated shape by a method wherein a light receiving part forms a telecentric optical system and is fixed to the tool hold rest of a numerically controlled machining tool. CONSTITUTION:A projecting part unit 1 is pulled out from a moving-aside position where the projecting part unit makes contact with a light receiving part unit 2 and positioned in a measurement position. By outputting a measuring unit positioning command signal from a control device for measuring a shape to a numerically control device, a motor is driven. Based on a work W fixed to a work fixing stand 52, a light receiving part unit 2 and a projecting part unit 1 following the light receiving part unit are positioned in a manner to match with the measurement portion thereof. In the positioning, since the light receiving part unit 2 is fixed to a tool hold rest 56, a movement operation function which the tool hold rest 56 has is utilized to a maximum. Even when the work W has a complicated shape, such as a screw and a hob, positioning is effected according to the measurement portion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerically controlled machine tool which optically measures the shape of the machined workpiece while it is still attached to the numerically controlled machine tool. The present invention relates to an optical workpiece shape measuring device.

[0002]

2. Description of the Related Art As is well known, a numerically controlled machine tool (NC machine tool) is widely used in which a machine operation is commanded by digitized information to automatically machine a workpiece. When machining a work piece with a numerically controlled machine tool, the work piece may not be machined to the desired shape due to wear of the tool or deformation caused by contact between the tool and the work piece. . Therefore, for example, when manufacturing a tool having a complicated shape such as a tapered end mill or a hob by grinding, generally, a numerical control machine tool (in this case, an NC tool grinder is used) is used. A method of removing a work piece and measuring the shape of the work piece after processing using a universal projector or a measuring device such as a contact type shape measuring device is used. Then, when the processing amount such as the grinding amount is insufficient, rework is performed.

By the way, in the above method in which the workpiece is detached from the numerically controlled machine tool and measured, a mounting error is likely to occur when the workpiece is mounted on the numerically controlled machine tool again after the measurement, and the mounting is troublesome. It takes work efficiency.

Therefore, conventionally, it has been attempted to optically measure the shape of the processed workpiece while it is still attached to the numerically controlled machine tool. For example, as a device therefor, the workpiece is machined. A non-contact online measuring device for measuring the outer diameter of an object is disclosed in JP-A-1-289606. FIG. 7 is a diagram showing a configuration of a conventional non-contact online measuring device provided in a numerically controlled lathe.

In FIG. 7, reference numeral 100 denotes a numerically controlled lathe body, a headstock 101 is supported on a bed 102, and a headstock 103 is rotatably supported on the headstock 101. A chuck 104 is attached to the tip of the main shaft 103 to hold the workpiece W. Reference numeral 105 denotes a tool base, and the tool base 105 includes a vertical tool feed base 106 that can move back and forth in the spindle axis direction, and a horizontal tool feed base 107 that can move forward and backward in a direction orthogonal to the spindle axis direction. The ball screw 108 and the servomotor 109 are driven to feed the sheet. A turret 110 is rotatably supported by the horizontal tool feed base 107 and holds a plurality of cutting tools (tools) 112 and a connecting rod 235 described later. Reference numeral 140 denotes an NC device, which gives a drive signal to the servo motor 109 or the like in order to move the tool base 105 or the like according to the input command information.

The non-contact online measuring device 200 is equipped so that it can be moved in and out laterally with respect to the spindle axis located in the machining area. As shown in the figure, 2
A first track 217 whose both ends are supported by the columns 216a and 216b and which extends in the main axis direction is provided, and a first slider 218 which is movable back and forth along the first track 217 is provided on the first track 217. The first slider 218 is provided with a second track 219 extending laterally with respect to the main axis. The second end of the piston rod of the fluid cylinder 221 fixed to the tip of the second track 219
A second slider 222 that is movable in the vertical direction in the figure along a track 219 is fixed. And this second
An optical outer diameter measuring instrument 223, which will be described later, is attached to the slider 222. Further, an opening is provided in the upper part of the lathe body cover 115 so that the optical outer diameter measuring instrument 223 can approach and separate from the workpiece W, and the opening is closed by the operation of the liquid cylinder 233. An opening / closing cover 234 for releasing or the like is provided.
Reference numeral 238 denotes an outer diameter detection control device, which moves the optical outer diameter measuring instrument 223 from a retracted position to a predetermined position in the lathe body cover 115, and corrects a bite position based on an outer diameter measurement value of the workpiece W. It is for giving the working data to the NC device 140.

FIG. 8 is an external view of the optical outer diameter measuring device shown in FIG. 7, and FIG. 9 is a configuration explanatory view of the optical outer diameter measuring device shown in FIG. The optical outer diameter measuring instrument 223 is of a laser light scanning type having a light projecting portion and a light receiving portion, and as shown in FIG. 9, the laser light from the semiconductor laser 224 is converted into a polygon mirror 225 and a reflecting mirror 226. Deflection scan by,
Further, after being converted into parallel scanning light by the collimator lens 227, the parallel scanning light is condensed by a condensing lens (light receiving lens) 228 in order to detect a shadow portion of the workpiece W, and a photodetector (light receiving The element) 229 is adapted to be converted into an electric signal. The semiconductor laser 224, the polygon mirror 225, the reflection mirror 226, and the collimator lens 227 form a light projecting unit, and the condenser lens 228 and the photodetector 229 form a light receiving unit. While the workpiece W is positioned between the collimator lens 227 and the condenser lens 228 and the parallel scanning light is scanning the workpiece W, the light is blocked by the workpiece W and is transmitted to the photodetector 229. Not reach The product of the interruption time and the scanning speed at which this light is not detected is calculated by a calculator (not shown) to measure the outer diameter dimension of the workpiece W.

The operation of the non-contact online measuring device 200 will be described. After the trial cutting or finishing is completed, the tool base 105 is retracted to a predetermined position. Liquid cylinder 23
3 is operated to move the opening / closing cover 234, and then the fluid cylinder 221 is operated to move the optical outer diameter measuring instrument 223 together with the second slider 222 from the retracted position to a predetermined position in the lathe body cover 115. Then, the tool base 105 is moved in the direction of the headstock 101 to connect the optical outer diameter measuring instrument 223 (the main body part of the non-contact online measuring device 200) and the tool base 105 via the connecting rod 235. After that, the tool base 105 is moved forward, the optical outer diameter measuring instrument 223 is moved to the position of the workpiece W to be measured and positioned, and the outer diameter dimension of the workpiece W is measured. There is.

[0009]

However, in the above-mentioned conventional apparatus, since the optical outer diameter measuring instrument used is a laser beam scanning type instrument having a mechanical drive unit such as a polygon mirror rotation motor, a numerical value is obtained. Since there is a risk that the mechanical drive part will rattle due to mechanical vibration during machining with a controlled machine tool and measurement accuracy will decline, the above-mentioned complicated retracting mechanism is provided and an optical outer diameter measuring instrument is used during machining. Is retracted, the optical outer diameter measuring instrument is connected to the tool mount (tool post) at the time of measurement, and the optical outer diameter measuring instrument is positioned with respect to the workpiece by advancing the tool mount. Therefore, it is not possible to use the movement operation function of the tool mount to the maximum due to the above retracting mechanism, and the positional relationship between the workpiece and the optical outer diameter measuring instrument during measurement is limited. Measurement target Type and measured the site of engineering products there has been a problem that is limited.

The present invention has been made to solve the above problems, and has a light projecting portion and a light receiving portion, and a workpiece mounted on a numerically controlled machine tool has a light projecting portion and a light receiving portion. The optical workpiece shape measurement in a numerically controlled machine tool that measures the shape of the workpiece based on the shaded area due to the fact that the light from the light projecting part is blocked by being located between This is an optical work piece shape in a numerically controlled machine tool that can be applied to the shape measurement of a work piece having a complicated shape such as a screw or a hob in a device, and can accurately measure the work piece shape. The purpose is to provide a measuring device.

[0011]

In order to achieve the above object, an optical workpiece shape measuring apparatus in a numerically controlled machine tool according to the present invention is provided with a light projecting section for irradiating light and a light projecting section for projecting light. And a light receiving section for detecting an intensity of light after passing through a work piece which is irradiated and attached to the numerically controlled machine tool, and which serves as an electric signal, and is located between the light projecting section and the light receiving section. In an optical workpiece shape measuring device in a numerically controlled machine tool, wherein the shape of the workpiece is measured based on the shaded portion due to the light from the light projecting part being blocked by the workpiece. , The light-receiving unit, a light-collecting element, a pinhole plate in which a minute hole is located at a rear focal point of the light-collecting element when viewed from the light incident side, and an image sensor arranged behind the pinhole plate. Composed by and
It is characterized by being fixedly mounted on the tool mount of a numerically controlled machine tool.

[0012]

In the optical workpiece shape measuring apparatus according to the present invention, the light and dark of the light emitted from the light projecting portion and passing through the workpiece mounted on the numerically controlled machine tool is sensed and converted into an electric signal. The light receiving section is composed of a condensing element, a pinhole plate in which a minute hole is located at a rear focal point of the condensing element when viewed from the light incident side, and an image sensor arranged in the rear side of the pinhole plate. Since it is configured as a telecentric optical system, only the light that is parallel to the optical axis of the light receiving portion and is incident on the condensing element is extracted through the minute holes of the pinhole plate. As a result, the light detected by the image sensor becomes equivalent to the projection of the parallel light even if the parallel light is not produced by the light projecting unit, and the light is detected based on the shadow portion on the image sensor. The shape of a work piece can be measured. Since the light-receiving unit is configured in the telecentric optical system in this way, the light-emitting region of the light-emitting unit is equal to or larger than the aperture of the light-receiving unit condensing element, and there is no extreme unevenness in the light amount distribution. It suffices to be positioned in front of the light receiving unit with the interval between them, and the measurement accuracy does not deteriorate even if the light projecting unit vibrates to some extent due to the positioning movement operation during measurement. Therefore, the light-receiving unit that senses the light and darkness of the light emitted from the light-projecting unit and passes through the workpiece to generate an electric signal is fixed to the tool mount of the numerically controlled machine tool by configuring the telecentric optical system. As a result, highly accurate measurement that is strong against external vibration can be realized. Since the light receiving part is fixedly mounted on the tool mount of the numerically controlled machine tool, the moving function of the tool mount can be used to the maximum during measurement, which allows the workpiece to have complicated shapes such as screws and hobs. Even if it is held, the light receiving unit can be positioned according to the measurement site.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of a four-axis numerically controlled grinding machine equipped with the optical workpiece shape measuring apparatus of the present invention, and FIG. 2 is a plan view of FIG.
It is a side view of the axial numerical control grinder seen from the arrow A.

In FIG. 1 and FIG. 2, 50 is a four-axis numerical control grinder main body, and a left and right moving table 51 slides on the bed (not shown) of the main body 50 in the left-right direction (X-axis direction) in FIG. It is possible. A workpiece fixing base 52 is fixed on the left and right moving table 51, and the workpiece W is attached to the workpiece fixing base 52 via an arbor 53. A front-rear moving table 54 is provided on the bed (not shown) so as to be slidable in the vertical direction (Y-axis direction) in FIG.

An up-and-down moving table 55 is provided on the forward-backward moving table 54 so as to be vertically movable in the up-down direction (Z axis direction) of FIG. A swivel base 5 that can support and swivel around the Z-axis
7 is provided. A rotary grindstone T as a tool is attached to the tool mount 56 via a support member. The left-right moving table 51 is moved in the X-axis direction by the motor MX, the front-back moving table 54 is moved in the Y-axis direction by the motor MY, and the vertical moving table 55 is moved in the Z-axis direction by the motor MZ. And again
The swivel base 57 is rotated by the motor MC about the Z axis. These motors MX, MY, MZ,
As shown in FIG. 4, the MC is connected to the numerical control device 58 via drive units DUX, DUY, DUZ, DUC, respectively, and when the workpiece W is machined, the workpiece W and the rotary grindstone T are connected to each other. Is driven to rotate by a drive signal output from the numerical control device 58 in accordance with the machining data given in advance so that the contact surface of the rotary grindstone T and the workpiece W are controlled. It is supposed to be done.

Reference numeral 1 denotes a light projecting unit which accommodates a light projecting unit, which will be described later, for irradiating light when measuring the shape of the workpiece, and 2 denotes the light and darkness of the light emitted from the light projecting unit 1 and passing through the workpiece. The light receiving unit is a light receiving unit that houses a light receiving unit to be described later that serves as an electrical signal. While the light receiving unit 2 is fixed to the tool mounting base 56, the retracting arm 3 can be moved back and forth in the Y-axis direction by a motor ML (not shown) on the side surface of the light receiving unit 2 fixed to the tool mounting 56. The light projecting unit 1 is fixed to the tip of the retracting arm 3 while being positioned in front of the light receiving unit 2. During processing, the retractable arm 3
Is retracted and the light projecting unit 1 is pulled in contact with the light receiving unit 2, so that the light projecting unit 1 is retracted so as not to disturb the processing.

FIG. 3 is a diagram for explaining an example of the configuration of the light projecting section and the light receiving section of the optical workpiece shape measuring apparatus according to the present invention. As shown in FIG.
The light projecting unit housed in is composed of a lamp (for example, a halogen lamp) 1a and a diffusion plate 1b arranged in front of the lamp 1a, and serves as a light source having a planar spread and a uniform light amount. The light receiving section housed in the light receiving section unit 2 has a condenser lens 2a as a condenser element and a pinhole in which a microscopic hole is arranged at a focal point on the rear side of the condenser lens 2a when viewed from the light incident side. It is composed of a plate 2b and a one-dimensional CCD line sensor 2c as an image sensor arranged on the rear side of the pinhole plate 2b. The light receiving unit housed in the light receiving unit 2 can be easily integrated into a compact body and is resistant to external vibration.

In this way, the optical system of the light receiving portion is constructed as a telecentric optical system, so that only the light which is parallel to the optical axis of the light receiving portion and is incident on the condenser lens 2a passes through the minute holes of the pinhole plate 2b. After passing, it is detected by the CCD line sensor 2c. Therefore, when the workpiece W to be measured is located between the light projecting unit 1 and the light receiving unit 2, only the component of the shadow formed by the workpiece W that is parallel to the optical axis of the light receiving unit. Image by CCD line sensor 2
It will be captured by c. Here, as shown in FIG. 3, the outer diameter of the workpiece W is D, and the CCD line sensor 2c
The length of the upper shadow is d, the focal length of the condenser lens 2a is f, and the distance between the pinhole plate 2b and the CCD line sensor 2c is L.
Then, the relational expression of D = (d × L) / f is established between them. Therefore, in the example of the outer diameter measurement shown in FIG.
The outer diameter D of the workpiece W is obtained by detecting the shadow length on the CD line sensor 2c based on the output signal from the CCD line sensor 2c and performing the calculation by the calculator 4 according to the above relational expression. When a currently available one-dimensional CCD line sensor with a pixel size of 7 μm and about 5000 to 10,000 pixels is used, by performing signal processing such as complementary calculation on the output signal from the CCD line sensor, A measurement resolution of 1 μm can be obtained.

FIG. 4 is a block diagram showing the electrical construction of the optical workpiece shape measuring apparatus of the present invention when applied to the 4-axis numerically controlled grinding machine of FIG. In FIG.
Reference numeral 4 denotes the arithmetic unit described above. The arithmetic unit 4 is connected to the CCD line sensor 2c of the light receiving section housed in the light receiving section unit 2, and the workpiece W is processed based on the output signal from the CCD line sensor 2c. To obtain the shape of. Reference numeral 5 is a shape measuring control device.

The shape measuring control device 5 positions the measuring device for positioning the light receiving unit 2 with respect to the workpiece W mounted and fixed on the workpiece fixing base 52 at the time of measurement. The command signal is applied to the numerical controller 58 described above. This measuring instrument positioning command signal is based on machining data about the workpiece W read from the numerical controller 58 and previously known position data indicating the positional relationship between the rotary grindstone T on the tool mount 56 and the light receiving unit 2. It has been calculated.
Further, the shape measurement control device 5 has a memory for storing and storing the shape measurement data input from the calculator 4 while giving a calculation command signal to the calculator 4 for each measurement of each measurement site. Data necessary for correction processing of the workpiece W is created from the shape measurement data and the processing data, and the correction processing data is given to the numerical controller 58. Further, from the shape measuring control device 5 to the drive unit DUL
When the motor ML is rotated by the drive signal given to, the above retracting operation is performed when the light projecting unit 1 is processed. Reference numeral 6 is a liquid crystal type measurement data display for displaying the shape measurement data. As described above, the optical workpiece shape measuring apparatus according to this embodiment has the retracting mechanism for the light projecting unit including the light projecting unit 1, the light receiving unit 2, the retracting arm 3, the calculator 4, and the shape. It is composed of a measurement control device 5 and a liquid crystal type measurement data display 6.

Next, the operation will be described. First, upon receiving a measurement start signal from the outside, the shape measurement control device 5 outputs a drive signal to the drive unit DUL. As a result, the light projecting unit 1 is pulled out from the retracted position in contact with the light receiving unit 2 and positioned at the measurement position. Then, the measuring device positioning command signal is given from the shape measuring control device 5 to the numerical control device 58, whereby each of the motors MX,
MY, MZ, and MC are driven, and the light receiving unit 2 and the light projecting unit 2 are moved to follow the workpiece W fixed to the workpiece fixing base 52 in accordance with the measurement site. The partial unit 1 is positioned. At the time of this positioning, since the light receiving unit 2 is fixedly mounted on the tool mount 56, the moving operation function of the tool mount 56 can be utilized to the maximum extent. Even if it has a complicated shape, it can be positioned according to the measurement site, and it can be applied to various workpieces. In addition, when the tooth thickness of the screw or the hob is measured, it is necessary to operate the swivel base 57 and measure the tooth thickness from an oblique direction in a plan view along the tooth.

Then, the arithmetic unit 4 calculates the workpiece W based on the output signal from the CCD line sensor 2c and the optical magnification.
The dimension of the measurement site of the, for example, the tooth thickness of the hob which is a tool is determined. In this case, since the light receiving unit is configured in the telecentric optical system, even if the light projecting unit 1 vibrates to some extent by the positioning movement operation at the time of measurement, the measurement accuracy is not deteriorated, and the vibration resistant high unit is provided. Accuracy measurement can be realized. The shape measurement data obtained by the calculator 4 is stored and stored in the shape measurement control device 5. Then, in the same manner, in order to perform the next measurement, the light receiving unit 2 and the light emitting unit 1 are positioned according to the measurement site, and the measurement is performed.

When measuring the two-dimensional shape of the work piece, a shadow image of the work piece is formed in a direction (Z-axis direction in FIG. 1) perpendicular to the direction in which the CCD line sensor 2c of the light receiving section is arranged. The measurement may be repeated while moving the tool mount 56 (light receiving unit 2) or the work piece thereof at each minute movement step interval so as to move.
The CCD line sensor 2c detects not only the shadow length of the shadow image of the workpiece but also the edge position of the shadow image. Therefore, the edge position of the shadow image is arranged at every minute movement step interval. The two-dimensional shape of the work piece is required. In this case, by using a two-dimensional CCD sensor as an image sensor, of course,
It is possible to reduce the above repeated measurement operation.

FIG. 5 is a view for explaining another example of the structure of the light receiving portion of the optical workpiece shape measuring apparatus according to the present invention. As shown in FIG. 5, a light receiving unit of the telecentric optical system may be configured by using an aspherical reflecting mirror 2a 'instead of the condenser lens 2a of FIG. 3 as a condenser element.
2'is a light receiving unit.

FIG. 6 is a view for explaining another example of the structure of the light projecting section of the optical workpiece shape measuring apparatus according to the present invention. When the type of the workpiece is determined and the measurable direction of the measurement site is fixed, the light projecting unit may be completely separated from the light receiving unit as shown in FIG. Good. In the example shown in FIG. 6, a light projecting unit including a plurality of lamps 1a ′ and a curved diffuser plate 1b ′ is housed in each of the above-described measurable directions and outside the four-axis numerical control grinder main body 50. The light unit 1'is arranged. With such a configuration in which the light projecting portion is separated, the retracting mechanism during processing can be made simpler.

[0026]

As described above, according to the optical workpiece shape measuring apparatus in the numerically controlled machine tool of the present invention, the light projecting section for irradiating light and the numerically controlled machine for irradiating from the light projecting section. A light-receiving part that senses light and darkness of light after passing through the work piece attached to the machine to generate an electric signal, and the work piece is positioned between the light projecting part and the light-receiving part. In the optical workpiece shape measuring device configured to measure the shape of the workpiece based on the shaded portion due to the light from the light projecting portion being blocked, the light receiving portion is configured as a telecentric optical system. Since it is fixed to the tool mount of the numerically controlled machine tool, even if the light projecting part vibrates to some extent by the positioning movement operation at the time of measurement, the measurement accuracy is not deteriorated. Moreover, the tool mount has Since the dynamic operation function can be used to the maximum extent, even if the workpiece has a complicated shape such as a screw or a hob, the light receiving section can be positioned according to the measurement site. When measuring the shape of a machined workpiece while it is still attached to a numerically controlled machine tool, the shape of a workpiece with a complicated shape can be measured and can be accurately performed. .

[Brief description of drawings]

FIG. 1 is a plan view of a 4-axis numerical control grinding machine equipped with an optical workpiece shape measuring device of the present invention.

FIG. 2 is a side view of the four-axis numerically controlled grinder of FIG.

FIG. 3 is a diagram for explaining a configuration example of a light projecting unit and a light receiving unit of the optical workpiece shape measuring apparatus according to the present invention.

FIG. 4 is a block diagram showing an electrical configuration of the optical workpiece shape measuring apparatus of the present invention when applied to the four-axis numerically controlled grinding machine of FIG.

FIG. 5 is a diagram for explaining another configuration example of the light receiving section of the optical workpiece shape measuring apparatus according to the present invention.

FIG. 6 is a view for explaining another configuration example of the light projecting section of the optical workpiece shape measuring apparatus according to the present invention.

FIG. 7 is a diagram showing a configuration of a conventional non-contact online measuring device provided in a numerically controlled lathe.

8 is an external view of the optical outer diameter measuring device shown in FIG.

9 is a structural explanatory view of the optical outer diameter measuring device shown in FIG.

[Explanation of symbols]

1, 1 '... Projector unit 1a, 1a' ... Lamp 1
b ... Diffusion plate 1b '... Curved diffusion plate 2, 2' ... Light receiving unit 2a ... Condensing lens 2a '... Aspherical reflecting mirror 2
b ... Pinhole plate with micro holes 2c ... CCD line sensor 3 ... Retreat arm 4 ... Calculator 5 ... Shape measurement controller 6 ... Liquid crystal type measurement data display 50 ... 4-axis numerical control grinder main body 51 ... Left and right Moving table 52 ...
Workpiece fixing base 53 ... Arbor 54 ... Longitudinal movement table 55 ... Vertical movement table 56 ... Tool mounting base 57 ... Revolving base 58 ... Numerical control device W ... Workpiece T ... Rotating grindstones MX, MY, MZ, MC, ML ... Motors DUX, D
UY, DUZ, DUC, DUL ... Drive unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sato Yamaguchi 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Kobe Steel Research Institute, Kobe Research Institute (72) Inventor Yuji Kusakabe Uozumi Town, Akashi City, Hyogo Prefecture Kanegasaki Nishi-Oike 179-1 Kobe Steel Co., Ltd. Akashi Factory (72) Inventor Kenji Kawamoto Uozumi-cho, Akashi-shi, Hyogo Prefecture Kanegasaki Nishi-Oike 179-1 Kobe Steel Akashi Factory (72) Inventor Yoshifumi Kawabuchi Hyogo Prefecture 179-1 Kanegasaki Nishioike, Uozumi-cho, Akashi-shi Kobe Steel Co., Ltd. Akashi factory

Claims (1)

[Claims] 1. A light projecting section for irradiating light, and a light receiving section for sensing the brightness of light after passing through a workpiece, which is irradiated from the light projecting section and attached to a numerically controlled machine tool, as an electric signal. A shape of the workpiece based on a shadowed portion due to the light being shielded by the workpiece located between the light projecting portion and the light receiving portion. In the optical workpiece shape measuring apparatus for a numerically controlled machine tool, which is configured to measure, the light receiving section is arranged with a light collecting element and a micro hole at the rear focus of the light collecting element when viewed from the light incident side. An optical cover for a numerically controlled machine tool characterized by comprising a pinhole plate arranged and an image sensor arranged at the rear side of the pinhole plate, and fixed on a tool mount of the numerically controlled machine tool. Workpiece shape measuring device.