WO1993003349A1

WO1993003349A1 - Device for optically scanning the surface of an object whose surface is capable of reflecting or scattering light

Info

Publication number: WO1993003349A1
Application number: PCT/DE1991/000617
Authority: WO
Inventors: Gebhard Birkle
Original assignee: Birkle Sensor Gmbh & Co.
Priority date: 1991-08-01
Filing date: 1991-08-01
Publication date: 1993-02-18

Abstract

A device for optically scanning the surface of an object (1) whose surface is capable of reflecting or scattering light has a light source (2) and a ring-shaped control mirror (7) with a continuous reflecting surface (16). Above the control mirror, in the direction of the main axis (17) and inside the opening angle of the control mirror (7) are arranged a plurality of individual optical lenses that surround the main axis (17) of the control mirror (7), as well as a sensor (4) and an electric evaluation device. After being reflected and/or scattered by the object (1) around its circumference (15), the light (10, 10') is projected onto the reflecting surface (16) of the control mirror (7), is deflected onto the sensor (4) and is evaluated in the evaluating device. The lenses are graded-index rod lenses (5) (GRIN rod-lenses) that reproduce an upright image and form a bundle of lenses adapted to the design of the control mirror (7) and to the cross-sectional profile of the object (1). The light input surfaces of the rod-lenses (5) face the reflecting surface (18) of the control mirror (7) and their light output surfaces are opposite to a ring-shaped, circular or elliptic sensor (4).

Description

^• means for optical scanning the surface of an object,

² whose surface is capable of reflecting or scattering light

3 Technical field: The invention relates to a device for optically scanning the surface of an object, the surface of which is capable of reflecting or scattering light, according to the preamble of claim 1.

Prior Art: From DE-Al-38 22 303, a device for optically scanning the ^one surface has been disclosed a movable object, for reflecting the surface of light or to scatter capable of having a light source and an internally comparable reflected pitched mirror with a circumferential Mirror surface and a centrally arranged through opening for the passage of the object through the desk mirror, in whose direction and within the opening angle above the through opening there is another mirror, as well as with an opto-electronic sensor and an electrical evaluation device. After reflection or scattering on the object, the light falls on the mirror surfaces of the mirrors, is directed onto the sensor and evaluated in the evaluation device. The light source illuminates the object around its circumference in the area of the through opening of the desk mirror in such a way that the light reflected or scattered by the object around the circumference simultaneously falls peripherally onto the mirror surface of the desk mirror. The second mirror has an obliquely inclined, flat mirror surface which directs the light onto an optical system for standing imaging on the sensor, which detects a complete circumferential band which corresponds to a circumferential surface of the object of a predetermined width. Symmetrical lenses can be arranged around the object, which guide the reflected light to the sensor, even with the interposition of optical fibers.

Furthermore, lenses with a graded refractive index (Graded-Index Rod Lenses, abbreviated GRIN rod lenses) are known, also under the name SELFOC lens, which has the shape of a cylindrical rod. The refractive index of such a lens usually has a parabolic course with the

REPLACEMENT LEAF - highest value in the optical axis, which decreases towards the periphery, whereby

² such a lens is an imaging optical element. Such rod lenses

³ can create upright images of an object in the image plane.

* gen (Introduction to Graded-Index Rod Lenses, Fiber Optics Newport Corpora-

* tion, 1986; Naumann / Schröder: Components of Optics, Hanser 1987).

6

⁷ Technical task:

* The invention is based on the object of a device of the above-mentioned

⁹ creation with which the surface of an object of any length, preferably

¹⁰ wise can be scanned during a movement of the object with a simple imaging method adapted to the problem u of the circumferential scanning,

^{12 in} order to obtain an optical image or an image signal of high resolution for the

^{1 to} reproduce a region of a certain width of the circumference of the object w as an illustrated circumferential band,

¹⁵ pass as low a number of optically effective surfaces as possible

¹⁶ should; the device is also intended to be compared with known devices

^{17 have} a smaller and more compact design and be designed more simply. 8 ⁹ Presentation of the invention and its advantages: ⁰ The solution to the problem according to the invention is that the lenses are upright ¹ imaging rod lenses with a graduated refractive index (GRIN rod lenses) in ² form of a lens bundle, which the design of the desk mirror and the transverse ³ adapted to the sectional contour of the object, preferably ring or elliptical, ⁴ , the light entry surfaces of the rod lenses facing the mirror surface of the desk mirror ⁵ and the light exit surfaces being opposed by an annular, circular or elliptical ^6- shaped sensor. 7 Further refinements of the invention are characterized in the subclaims.

REPLACEMENT LEAF The invention has the salient advantage that it is most advantageously suitable for scanning objects with practically any cross-section, which can be translucent, transparent or opaque, but whose surface is able to reflect or scatter light Device by the use according to the invention of a plurality of individual, upright imaging optical rod lenses with a graduated refractive index (GRIN rod lenses) always produces an upright and standing image, so that a region of predeterminable width of the entire circumference of the object or only a part of the same can be obtained with the highest resolution when the object is in motion or at a standstill as an optical image or image signal, for example in the form of an illustrated peripheral band or part of the peripheral band. The surface of the object can reflect regularly or diffusely, the object can have a high or low reflectivity. If the object has irregularities, holes, cutouts, edge damage, breaks, chipping or other anomalies on its surface, this changes the reflection or scattering or the light transmission compared to the normal surface; this change in the reflection or the scatter or the light intensity can be detected according to the invention. The majority of the GRIN rod lenses are advantageously formed by a lens field from.

The row-by-row arrangement of the upright imaging individual lenses in the form of GRIN rod lenses, the images of which merge into an overall image in the image plane, result in the overall image. In contrast to the use of a conventional lens, the GRIN rod lenses, in particular in the form of a rod lens field, produce an image which is circular, ring-shaped or elliptical, etc. This is because the geometric shape of the sensor, for example in the form of a circular line or ellipse or a ring, the sensor being in particular a CCD pixel field sensor, advantageously selects the peripheral image of the object in the image plane. Short image and object widths, a bright image and a compact design can be realized. When producing the

REPLACEMENT LEAF ¹ device according to the invention fall far fewer items, assembly

² and adjustment work. Accordingly, the production is less expensive

³ and the application is less problematic than with circumference testing devices of the state of the art *. In particular, a CCD pixel array-building ⁵ are given as a sensor element the functions of a CCD flat-panel camera in use.

6

⁷ The rod lens field of GRIN lenses and / or the

⁸ sensor to be adapted to the profile or cross-section of the object to be scanned, for example such that the field of components or GRIN lenses is congruent with the profile or cross-section; in the case of an elliptical cross section of the object, the field of the upright imaging optical components or the rod lens field and / or the effective sensor surface is designed elliptically.

On the basis of the imaging laws of rod lenses with a graduated refractive index, an image of the object to be imaged is optically imaged in the image plane and mapped as an upright image on the circular, ring, elliptical or other planar selection sensor. A uniform upright image on the sensor is thus selected via the lens field of the GRIN rod lenses.

Due to the adjustability of the rod lenses with a graduated refractive index and / or the plane mirror in the axial direction relative to one another, an adaptation to a specific object diameter can be achieved.

The device can e.g. B. be designed such that the surface of the objects in free fall or in the running passage, e.g. in the case of a rope, can be detected, thereby ensuring high performance of the device according to the invention with a large throughput of objects or per running meter of object.

REPLACEMENT LEAF Likewise, the device can only be designed for one-sided insertion of an object, so that the object is inserted through an opening for scanning and removed again through the same opening.

Brief description of the drawing, in which: FIG. 1 shows a schematic illustration of a device in a top view along the line CD in FIG. 2, the cover and the sensor in the left half of the image being removed in order to view the GRIN rod lenses in the view of the end faces Figure 2 shows a section through the device for displaying the GRIN rod lenses in a longitudinal view along the line AB in Figure 1 Figure 3 shows a partial section of a desk mirror in the form of a transparent toroid with a semi-transparent mirror surface and with a cylindrical peripheral lens surface for shifting the geometric location the intersection points of all the marginal rays on the surface of the object to be scanned and FIG. 4 a partial section of a further desk mirror in the form of a transparent toroid of a semitransparent mirror surface and with a convex curved peripheral lens surface for the adapted correction of the course of the geometry location of the rays of the light beam on the object in relation to the geometry of the sensor.

WAYS OF IMPLEMENTING THE INVENTION: The figures show a schematic representation of the device, consisting of a prismatic or conical or bowl-shaped mirror body 7, which is made of suitable glasses or metal with a correspondingly mirrored surface as a closed peripheral mirror surface 16 in the form of a desk mirror is.

REPLACEMENT LEAF ¹ The console mirror 7 is arranged within a housing 9, which has a lower

^{2 has} cover 8, on which the desk mirror 7 is placed. The mirror surface 16 of the desk mirror 7 is internally frustoconical or also curved, the main axis of the desk mirror coinciding with the main axis 17 of the device. A through opening 18 runs centrally through the mirror surface 16 or the mirror body 7 in the direction of the main axis 17 of the mirror surface 16, so that the console mirror 7 is designed in a ring shape. Likewise, the lower cover 8 of the housing 9 has a through-opening 13, the two through-openings 13 and 18 of the cover 8 and the desk mirror 7 lying centrally on one another. The console mirror 7 can be arranged to be vertically displaceable in the axial direction of the main axis 17, which is to be indicated by the movement arrow 14. An object can be inserted into and out of the device through the through opening 13 of the lower cover 8 and through the through opening 18 of the desk mirror 7.

The housing 9 has an upper cover 3, which closes the housing 9 like a lid and to which a tube 11 is integrally formed, which is preferably cylindrical and has a through opening 12. The tube 11 projecting into the interior of the housing 9 ends above the lower cover 8, so that a circumferential gap 21 of height a remains between the same and the lower end of the tube 11. The upper cover (3) and the tube (11) can be formed in one piece and, together with the lower cover, the annular holder (6) and the housing (9), are made of plastic.

An annular holder 6 is placed on the tube 11, within which a plurality of individual, upright imaging optical rod lenses 5 with a graduated refractive index (GRIN) are arranged. The rod lenses 5 run close together, preferably parallel to one another, and thus form an annular lens field, which is preferably annularly centered with respect to the main axis 17. In Figure 2, two such rod lenses 5 are in

MARINE LEAF _* Longitudinal section shown, in Figure 1 is a plan view of the Schnitdinie CD in

^{2 of} the left half of the picture shown on the rod lenses, from which it can be seen that these

^{3 are} cylindrical. The lens field of the rod lenses 5 is preferably parallel

^{4 of} the main axis 17 of the device aligned. The bracket 6 together with the

⁵ rod lenses 5 can also be adjusted in height on the tube 11, so that the rod lenses 5 and the desk mirror 7 can be adapted to the object throughput.

⁷ knives are adjustable relative to each other. The lower ends of the rod lenses 5

⁸ are the mirror surface 16 of the desk mirror 7 directly adjacent and within the

⁹ opening angle arranged the same.

Above the upper ends of the rod lenses 5 is an opto-electronic one

² annular sensor 4 arranged, which in a preferred embodiment

^{3 is a} ring-shaped CCD pixel field component and is connected to an electrical evaluation device (not shown). The annular sensor 4 is

^{5 is} preferably arranged on a carrier 3 which is fastened on the inside of the upper cover 3. The focal points of all rod lenses 5 fall on individual CCD elements of the field, which is thus able to detect and image a complete circular ring without software masking.

An object 1, for example a transparent glass tube through which Durchgangsöff- ¹ calculations 12,13 of the covers 3,8 and through the tube 11 and the through opening 18 of the pitched mirror 7 moved through and from a light source 2, a laser light source preferably , illuminated, which is a simple and effective lighting variant. For example, the glass tube is axially illuminated during manufacture, originating from the melt (light conduction); scattered light is detected by the imaging optics at defects. Other objects may require modified and adapted lighting methods.

In the example shown in FIG. 2, the light rays of the light source 2 are incident parallel to the main axis 17. An anomaly of the surface of the object 1

REPLACEMENT LEAF ¹ the light is scattered or reflected or the light intensity is weakened or

² the beam path changes in some other way, whereby the scattered or reflected

³ light rays 10 are thrown through the gap 21 between the end of the tube 11 and the lower cover 8 onto the mirror surface 18 of the desk mirror 7 as soon as the anomaly of the surface is in the region of the gap 21 or crosses this region. The desk mirror 7 deflects the light, which now falls on the lower entry openings of the rod lenses 5 of the lens field, which focus the emerging light beams 10 'and direct them onto the ring-shaped sensor 4, which is connected to an evaluation device (not shown). As a result, a narrow circumferential ring 16 on the object 1 is imaged in a ring on the sensor 4.

If the object 1 is moved in the direction of the main axis 17 of the device during the described scanning process, it is evident that the entire circumferential surface of the object 1 is scanned and reproduced in the sensor 4 as a circular ring or circular line which depicts the illuminated circumferential surface of the object in maps the image plane as an image. If an anomaly on the surface of the object 1 is illuminated when the object 1 passes through the mirror surface 18 at time t, this anomaly is displayed in the circumferential band of the object 1 shown on the pixel field of the sensor 4, so that this object can be sorted out, for example . In the case of a standing object, an upright and standing image is created.

In addition, a silky illumination of the object is also possible, also through the desk mirror, which in this case can be a semi-transparent mirror, which is shown in FIGS. 3 and 4; with regard to further lighting options, reference is made to DE-Al-3822303.

Figures 3 and 4 show ring-shaped desk mirrors 22 and 22 'for side lighting and to avoid imaging errors. Because due to

SPARE BLADE i Curvature of a mirror surface in the tangential direction results in aberrations

² , which is why the marginal rays are reflected on the mirror surface

³ do not cut in a geometric location that lies on the surface of the object, but in a location that lies outside the surface of the object;

⁵ in the case of rotationally symmetrical mirror bodies, the geometric locations are circles.

⁶ Other rays lying between the marginal rays intersect radially on the bundle center lines between the geometric locations, which results in a distortion of the intersection points over the axes of the light bundle. This distortion is most noticeable with a conical mirror, but it also occurs with other mirror shapes that are designed as mirror bodies and in which the mirror surface is curved in one direction.

In FIGS. 3 and 4, the desk mirrors 22 and 22 'each consist of a transparent body in the form of a toroid with the main axis 17, which through an upper surface 23 and 23', a rear, inclined and in the direction of the Oblique flat surface 24 or 24 'facing the light source 2' or 2 ", which is an inner semitransparent mirror surface 24 or 24 ', the mirror of which faces away from the light source 2', 2" and a circumferential one, the main axis 17 of the Desk mirror 22 or 22 'facing surface 25 or 25' is limited. In Figure 3, the surface 25 is cylindrical and represents a cylindrical lens surface; in Figure 4, the surface 25 'is convex. Due to the cylindrical or the convex curvature of the lens surface 25 or 25 ', the image can be adapted to specific requirements of the object or else the geometry of the optoelectronic sensor used. The light sources 2 or 2 'or 2 "can surround the desk mirrors 22 or 22' in a ring, so that the object 1 is illuminated in a uniform ring, for example by means of optical fibers.

In an advantageous embodiment, the curvature of the lens surface facing the center of the mirror body can be in the direction of the main axis of the lens

REPLACEMENT LEAF ¹ mirror body can be changed in such a way that the focal length of the lens

² areas can be changed in order to attach the desk mirror to objects of different

³ trie, especially to adapt to cylindrical objects with different diameters. The desk mirror can be made of flexible, transparent material

⁵ stand and for example with a solid, ring-shaped, transparent perforated

⁶ slices must be covered. Is placed on the perforated disc, symmetrical or asymmetrical

⁷ trisch, a pressure exerted, the desk mirror deforms, whereby due to the * volume reduction the inner, cylindrical lens surface bulges all around

Is and ⁹ with respect to the direction of the major axis convex assumes ⁰ changeable form. 1 Industrial applicability: The device according to the invention is used for scanning objects whose surface has reflective, scattering or properties which otherwise change the light intensity. The device is suitable, on the one hand, for use where a large number of objects, preferably long objects, such as pencils, which can be mass-produced, are to be quickly checked or sorted according to specified quality criteria, and, on the other hand, where a running object is in one piece, for example a braided or knitted rope, whose surface condition including the criterion of its color is to be detected. In particular, the device according to the invention is suitable for examining the surface properties of elongated objects, preferably when moving them, such as lipsticks, screws, nails, pencils, glasses, braided or knitted ropes and others, in order to differentiate according to specified quality criteria. for example, sorting the objects according to surface characteristics.

REPLACEMENT LEAF List of reference numerals:

REPLACEMENT LEAF

Claims

¹ claims:

2

³ 1. Device for optically scanning the surface of an object (1),

Is ⁴ to reflect or scatter light sai surface capable of having a light source ^s (2) and an optical conical, shell or ellipse shaped, inner to

⁶ mirrored desk mirrors (7) with circumferential mirror surface (16) and a

⁷ trically arranged through opening (18) for the passage of the object (1)

⁸ through the console mirror (7), above it in the direction of the main axis (17)

⁹ and within the opening angle of the desk mirror (7) a plurality of

¹⁰ individual optical lenses located, the ring-centered the main axis

¹¹ (17) of the console mirror (7) and an opto-electronic sensor (4),

¹² which is connected to an electrical evaluation device, the light

¹³ (10, 10 ') after reflection and / or scattering on the object (1) around its circumference

¹ (15) thrown onto the mirror surface (16) of the desk mirror (7), onto the sensor (4)

^{15 is} steered and evaluated in the evaluation device, is characterized in that

¹⁷ that the lenses upright imaging rod lenses (5) with graduated refractive

¹⁸ dex (GRIN rod lenses) are in the form of a lens bundle that matches the design of the

¹⁹ console mirror (7) and the cross-sectional contour of the object (1) is adapted, preferably ⁰ or ring-shaped, where the light entry surfaces of the rod lenses ¹ (5) face the mirror surface (18) of the console mirror (7) and the ^second A ring, circular or elliptical sensor (4) ³ faces light exit surfaces. * ⁵ 2. Device according to claim 1, characterized in that ⁶ the rod lenses (5) in a housing (9) with upper and lower cover ⁷ (3.8), each with a passage opening (12, 13) for the passage of the object ( 1) ^{8 are held} within an annular or elliptical holder (6), which are pushed onto a tube (11) for introducing or passing through the object (1)

SPARE BLADE which is fastened to the upper cover (20) of the housing (9) which carries the sensor (4), the tube (11) ending above the desk mirror (7).

3. Apparatus according to claim 1, characterized in that the rod lenses (5) are directed parallel to each other and the same and / or the desk mirror (7) in height parallel to the main axis (17) of the desk mirror (7) are displaceable relative to each other.

4. Apparatus according to claim 1 or 2, characterized in that the upper cover (3) and the tube (11) are integrally formed and together with the lower cover, the annular holder (6) and the housing (9) consist of plastic.

5. The device according to claim 1, characterized in that the sensor is a ring-shaped or circular-shaped CCD pixel field component (4) having one or more pixel field rings.

6. The device according to claim 1, characterized in that for a given cross section of the object, the field of GRIN rod lenses and / or the selecting sensor surface is adapted to the cross section or the profile of the object to be scanned.

7. The device according to claim 1, characterized in that the console mirror is a semitransparent divider mirror and the illumination of the object is carried out by the divider mirror on the object.

8. The device according to claim 1, characterized in that the console mirror is a transparent body in the form of a toroid (22,22 '), the back, the light source (2,2,2 ") facing or facing inclined inclined than inside mirrored mirror surface (24, 24 ') is formed, wherein ¹ the peripheral surface facing the main axis of the desk mirror (17) is designed as a - cylindrical lens surface (25).

3

* 9. Device according to claim 8, characterized in

⁵ that the mirrored mirror surface (24, 24 ') is semi-transparent and

⁶ light sources (2,2 ') surround the toroid (22,22') to the radial side

⁷ Illumination of the object (1) through the semitransparent mirror surface (24, 24 ').

8. The device according to claim 1, characterized in that the main axis (17) of the desk mirror (22 ') facing the circumferential inner surface is designed as a curved lens surface (25').

11. The device according to claim 1, characterized in that the lens surface, based on the direction of the main axis of the desk mirror, is convex or concave.

12. The apparatus according to claim 1, characterized in that the focal length and / or the curvature of the lens surface can be changed in the direction of the main axis of the desk mirror.

REPLACEMENT LEAF