JP2021113701A - Inner surface shape measurement device - Google Patents

Abstract

To provide a device and method for acquiring a light trail image without generating ghost images by using a shield member so as to contactlessly measure an inner surface shape of an object using optical means.SOLUTION: The reason why ghost images appear in a light trail image acquired by an inner surface measurement device is that light trails reflected inside a transparent tube reach a light receiving member. A light trail image can be acquired without generating ghost images by installing a light-absorbing shield member in a path of internal reflection light to the light receiving member on a central axis G of the transparent tube.SELECTED DRAWING: Figure 1

Description

The present invention is a method for non-contactly measuring the internal shape of an industrial product having an internal space such as various pipes or an engine block, a pipe in a complex, or a biological organ such as the oral cavity of the human body, and measurement using the method. Regarding the device.

The measurement of the internal shape of various objects is in high demand in many industrial fields such as the measurement of the inner diameter of various pipes and the measurement of the internal shape of engines, etc., and has the same needs as those of Patent Document 1. There is a precedent case. However, since the conventional device does not take measures against stray light and is affected by the internal reflection on the inner surface side of the transparent tube, a ghost image is generated in the light trail image. There was a problem that the ghost image deteriorated the quality of measurement.

JP-A-2007-285891 Japanese Unexamined Patent Publication No. 2015-0459193

The present invention is an apparatus and method for acquiring a light trail image that does not generate a ghost image even if there is internal reflection from a transparent tube, and measuring the shape of the inner surface of an object in a non-contact manner by using optical means. The challenge is to provide. That is, an image sensor such as a CCD (hereinafter referred to as CCD) illuminates the inside of the object with a sheet-shaped band of light, and removes the influence of stray light on the cross section (inner surface) of the object that is so-called light-cut by the sheet-shaped light. It is the present invention to provide a measuring device for quantifying the inner diameter, internal shape, outer shape, etc. of the object by a computer (also referred to as an image sensor), and to provide a method using this device. Is the issue.

The present invention
(1) Calculate the distance between the reference position of the photographing optical system and the inner surface of the measurement target from the coordinate data of the photographed light trail image and the fixing member that combines the light projecting member, the light receiving member, the tubular member, and the shielding member into one rigid body. An inner surface shape measuring device characterized by having a means for calculating a distance.
(2) Measurement target in an industrial product having an internal space such as various pipes and engine blocks, a pipe in a complex, or a device for measuring the inner surface shape of a biological organ such as the oral cavity of a human body. A means of irradiating a light beam by spreading it in a disk shape at a predetermined position of the above, and a cross-sectional light trail of the object obtained by sectioning the inner surface of the object to be measured by the irradiated light beam, and at the same time, internally reflecting by a shield. A method for measuring an inner surface shape, which comprises a photographing means for preventing and a distance calculating means for calculating a distance between a reference position of a photographing optical system and an inner surface to be measured from coordinate data of a captured light trail image.
Is.

The projection member is a member having means for irradiating a sheet-shaped light band (hereinafter referred to as sheet-shaped light Sb) by spreading a light beam in a disk shape at a predetermined position to be measured. The composition of the projection member consists of a light source unit that emits collimated laser beam ls, a conical mirror or conical prism that generates a band of light (collectively referred to as eM), and a component that fixes the light source unit and eM. The light source unit is a device that irradiates a collimated point light source near the apex of eM from the direction of the conical axis, and may have the following two structures. 1) A structure that uses a semiconductor laser whose diameter is smaller than that of a cylindrical member. 2) A structure in which the light source body is located outside the device for measuring the inner surface shape, but is guided by a single-mode optical fiber. Further, the wavelength of the light source used may be any wavelength that can be observed by the light receiving member, and does not have to be a specific wavelength.

The conical mirror may be a so-called conical mirror having an angle of 90 °, or a component obtained by hollowing out and mirror-coating a conical material having a direct point angle of 90 °. Further, the conical prism is a component obtained by hollowing out a cone having a direct point angle of 90 ° in a transparent cylindrical material such as glass. The diameter of the eM needs to be smaller than the diameter of the cylindrical member, and is preferably larger than the diameter of the collimated point light source of the light source portion. Since the angle of the apex of eM is 90 °, the sheet-like light Sb reflects the point light source from the direction of the conical axis near the apex, so that a flat sheet-like light band having the same normal as the conical axis is formed. Will be generated.

The light receiving member is a so-called image sensor, such as a CCD camera or a digital camera. The element inside may be an image sensor having a two-dimensional array. Since the opening of the image sensor is arranged inside one end of the cylindrical member, it needs to be smaller than the diameter of the cylindrical member, but there is no other size limitation on the light receiving member. It is desirable that the optical axis of the image sensor coincides with the central axis of the cylindrical member described below, and it is desirable that the installation position of the light receiving member coincides with the normal direction of the plane of the sheet-shaped light Sb.

The cylindrical member is a transparent tube made of cylindrical glass or transparent resin. The installation position is between the light projecting member and the light receiving portion, and it is desirable that the optical axis passing through the center of the image sensor of the light receiving member and the cylindrical center axis G coincide with each other. Due to this structure, the scattered light generated by the light beam sheet Sb generated from the light projecting member hitting the object always passes over the cylindrical member at least once before reaching the light receiving member. The diameter of the cylindrical member needs to be larger than the diameter of the light projecting member or the size of the image sensor of the light receiving member, but there is no upper limit to the diameter size.

The shielding member is an elongated rod. The installation position is connected to the fixing member, and it is desirable that the surface of the shielding member is made of a material having high absorbance or low reflectance and transmittance. The shape is put in the cylindrical member, but the cross-sectional shape is not limited to a cone, a cylinder, a prism, a pyramid, a cylinder, and the like. The length will be described later.

The fixing member is a member that is grouped as one rigid body, but at least three or more are required in the device. It is a member for fixing the projection member and the cylindrical member, the light receiving member and the cylindrical member, and the shielding member and the projection member or the cylindrical member. It is necessary that the material is rigid enough to keep the positional relationship of each part unchanged, but there are no other restrictions on the material or size conditions.
From now on, a part composed of a light projecting member, a light receiving member, a tubular member, a shielding member and a fixing member that is integrated into one rigid body will be referred to as a sensor head part (sH). The reference position O of the sensor head portion sH is the intersection of the central axis G of the cylindrical material and the plane formed by the sheet-shaped light Sb, and is the reference position of the photographing optical system. The point O does not have to be the same as the vertex of eM.

The inner surface shape measuring method characterized by providing a distance calculating means for calculating the distance between the reference position of the photographing optical system and the inner surface to be measured from the coordinate data of the photographed light trail image will be described. In calculating the distance, it consists of two parts: a part that calculates the shape of one cross section from a light trail image of one shot with a computer, and a part that combines the shapes of those cross sections with a computer. In addition, the computer and the sensor head unit sH are connected by an interface such as bluetooth or USB to acquire a light trail image.

A part for calculating the shape of one cross section from a one-shot light trail image by a computer will be described. The sheet-shaped light Sb hits the inner surface of the measurement target, and the light is scattered from the hit point. The image obtained by acquiring an image of the scattered light by the light receiving member is a light trail image captured as a cross section of the inner surface of the measurement target. Since the light receiving member and the cylindrical member are installed axisymmetrically with respect to the central axis G of the cylindrical material, the distance calculation means can explain the circumference of the central axis by the same means if a specific one direction is explained. The distance calculation method will be described when the axis G is parallel to the horizon and the sheet beam is in the vertical direction.
Now, the sheet-shaped light Sb emitted from the light receiving member 1 in the vertical direction hits point A on the measurement target, and the scattered light is captured (photographed) by the light receiving member, and the angle φ expected at that time is can get. As a result, if the distance between the light receiving member and the light projecting member is set to l, the shape of the triangle is determined from one side, the right angle, and the other angle φ in the right triangle, and the distance OA from the origin O = r can be calculated.

When the sheet-shaped light Sb to be irradiated is not perpendicular to the axis G and is tilted, even if the sheet-shaped light Sb is tilted, the distance OA can be calculated by obtaining the tilt value θ in advance by a three-dimensional measuring device or the like. .. This is because, assuming that the center position of the light receiving portion is C, ∠AOC and distance OC are known, and since ∠OCA is obtained from photography, the values of the three sides of the triangle and the angle are fixed.

Next, a method of obtaining an inner surface shape by collecting a plurality of cross sections will be described. This portion may be omitted in a device for which the inner surface shape of one cross section is acceptable. The sensor head unit is attached to an encoder or the like and is attached to a uniaxial or multi-axis movement slider that can specify the position and direction, or is attached to an articulated robot. In the case of a moving slider, it is desirable to install it so that the moving axis of one moving slider is parallel to the G axis, and align the origin of the moving slider with the reference position O of the photographing optical system. In the case of an articulated robot, it is desirable to align it with the direction of the cylindrical axis and the G axis at the tip of the joint.

The shape of one cross section obtained by determining the position and direction of the sensor head portion and acquiring the light trail image at that timing can be converted into a coordinate system such as an electric slider or a coordinate system of an articulated robot. .. That is, the coordinates are transformed by multiplying the shape of one cross section by the rotation matrix that takes into account the shift amount of the X, Y, and Z coordinates. By repeating this for a plurality of cross sections and stacking them, internal surface shape measurement data can be obtained.

Next, a photographing means for preventing internal reflection by a shield will be described. First, the mechanism by which the light entering the cylindrical member becomes stray light and causes a ghost image on the light receiving member on the central axis G will be described. Sb emitted from the projection member hits the measurement target and scatters. The ghost image does not appear unless the light travels from the measurement pair to the light receiving member at the shortest distance. On the other hand, it is reflected at each interface of the cylindrical member, and when there is a path other than the shortest, it becomes a ghost image.
In order to make this phenomenon easy to understand, it will be described with reference to FIG. Here, the wall thickness of the cylinder is an infinitely thin transparent tube. This is because the light trail is refracted while passing through the transparent tube, but since the glass tubes are parallel, there is no change in the angle between the incident light and the transmitted light on the glass tube, so there is no problem in explaining the mechanism. Because.

Now, it is easy to understand if the image sensor has an infinitesimal area and is a cylindrical tube with a sufficiently long cylindrical length, and the trajectory of light is seen from the bottom of the cylinder. When light is reflected, the angle of incidence and the angle of reflection are the same, so if the light is reflected without passing through the central axis G of the cylindrical member of Sb1 in FIG. 2 (b), the center of the cylinder no matter how many times it is reflected. It does not pass on the axis G. In this case, the stray light does not enter the image sensor. On the other hand, once Sb2 in FIG. 2B passes through the cylindrical central axis G and is reflected, it always passes on the cylindrical central axis G again before being reflected again. If the position where the stray light passes on the central axis is exactly the bottom surface of the cylinder, there is an image sensor, and the stray light is detected and a ghost image is obtained.

Consider also a light receiving member having a finite size. In fact, the size of the image sensor has a finite size such as 1 inch. In addition, the objective lens is often attached in front of the image sensor, and at the position immediately before the objective lens, light is received in a range several times that of the image sensor. When the light receiving range is set to the radius Δ immediately before the light receiving member 2, it is clear that it is desirable that the cross section of the shielding member has a cross-sectional shape larger than a circle having a radius Δ. This is because the angle of incidence and the angle of reflection are equal, so the closest position of the central axis G of Sb1 in FIG. 2 (b) and the closest position of the incident light are the same as the closest position of the reflected light, and Δ from the central axis G. This is because it does not come within.

If the length of the light-shielding member penetrates both ends of the cylindrical member, the ghost image can be completely removed, but it is not necessary to penetrate it. If there is a gap between the light-shielding member and the light-receiving member, the light trail passing through the gap is internally reflected. When this gap is narrow, the reflection angle is small and the reflectance is small, so that ghost light trails are virtually not generated. The length of the gap width is related to the reflectance inside the transparent tube, and the wider the width, the higher the reflectance, and the length of the light-shielding member within the range where the reflectance is 5% or less is desirable.

The ghost image does not appear in the light trail image obtained by irradiating the measurement target from the projection member and the scattered light by the light receiving member.

The side view which showed the apparatus structure in the internal shape measurement of this invention. A side view (a) and a bottom view (b) illustrating a light trail during internal reflection in a cylindrical tube. A photograph of the prototype of the present invention taken from the side. The light trail image (a) obtained by the prototype of the present invention and the light trail image (b) obtained by the conventional device to be compared. The side view explaining the member which generates the sheet beam light in the projection member 1. Conical mirror (a) Conical prism (b) An example of the measurement result of the inner surface. Example (a) of one cross section and measurement example (b) obtained by sliding

The present invention will be described with reference to examples.

The prototype of FIG. 3 will be described with the following mechanical configuration. It consists of a cylindrical sensor unit with an outer diameter of Φ20 mm and a total length of 170 mm and a PC. The floodlight member consists of a conical mirror with a bottom surface of φ5 mm and a semiconductor laser that emits a green output of 5 W with a diameter of 5 mm. The light receiving member consists of an ARTCAM-022 MINI camera with a lens with a diagonal angle of view of 142 ° attached to the S mount, and this camera is connected to a PC (NEC Lavie LZ2750 / S) with a USB cable. The cylindrical member is a transparent acrylic resin with an outer diameter of φ20 mm × 70 mm and a thickness of 1.5 mm. The shielding member is an alumite-treated aluminum rod with a diameter of 5 mm and a length of 55 mm.

The first fixing member fixes the semiconductor laser and the aluminum rod. The second fixing member fixes between the camera and the transparent acrylic resin. The third fixing member corresponds to the portion 6 in FIG. 3, sandwiching the semiconductor laser, and fixing the projection member and the inside of the transparent acrylic resin tube. The inclination of the axis G and the plane beam Sb is installed within 90 ° to 4'.
FIG. 4A is an image obtained by inserting the prototype of FIG. 3 into a white paper cup and acquiring a light trail image. For comparison, FIG. 4 (b) shows an image obtained by inserting a light trail image into a white paper cup with the device before the present invention. It is clear that the presence of the shielding member does not generate a ghost image in the light trail image.

FIG. 6A is an example of calculating the distance between the reference position of the photographing optical system and the inner surface of the measurement target from the coordinate data of the photographed light trail image. FIG. 6B shows the measurement results obtained by attaching the inner surface shape measuring device of the present invention to an electric slider (KXL06075-C1-C5A manufactured by Suruga Seiki Co., Ltd.).

The present invention is as described above, and the inside surface of an industrial product having an internal space such as various pipes and engine blocks, a pipe in a complex, or a biological organ such as the oral cavity of a human body is measured. In measuring the cross-sectional shape of the above, a light beam is irradiated in a disk shape at a predetermined position on the inner surface to be measured, and a light trail showing the inner surface shape due to the irradiation light is photographed by an imaging sensor to accumulate image data of the light trail. However, since the distance between the reference position of the imaging system and the inner surface of the measurement target is calculated from the accumulated light trail image data to measure the shape of the inner surface, various targets are not limited to the industrial and consumer fields. Since the shape of the inner surface (cross section) of the surface can be easily measured without contact, it is extremely useful in industry.

1 Projection member
2 Light receiving member
3 Inner surface of measurement target
4 transparent tube
5 Shielding member
6 Fixture member
Central axis of G4
Sb sheet-like light
Sb1 Sheet-like light that does not pass through the central axis
Sheet-like light passing through the Sb2 central axis
One point where A3 and Sb meet
One point on the inner surface of P4
Distance between the center position δ 2 and 5 of the image sensor in C 2
O Distance between device origin r O and object to be measured
Radius of cylindrical tube of R04
Lb collimated laser beam
eM Conical Mirror or Conical Prism

Claims (2)

Calculate the distance between the reference position of the imaging optical system and the inner surface of the measurement target from the coordinate data of the captured light trail image and the fixing member that combines the light projecting member, light receiving member, tubular member, and shielding member into one rigid body. An inner surface shape measuring device characterized by having means. In a device that measures the inner surface shape of an industrial product having an internal space such as various tubes or engine blocks or a biological organ such as the oral cavity of a human body as a measurement target, a light beam is spread in a disk shape at a predetermined position of the measurement target. The means for irradiating the target, the means for photographing the cross-sectional light trail of the object obtained by sectioning the inner surface of the object to be measured by the irradiated light beam, and the means for preventing internal reflection by a shield, and the photographed light trail image. An inner surface shape measuring method including a distance calculating means for calculating a distance between a reference position of a photographing optical system and an inner surface to be measured from coordinate data.

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