Workpiece measuring device

Abstract

The utility model discloses a workpiece measuring device, which comprises an area light source, a shading plate and a double telecentric lens, the shading plate is provided with a light through hole, and the size of the light through hole is slightly larger than the overall size of a workpiece. The device is low in cost; the combination of a common area light source and a shading plate is adopted to replace a traditional expensive parallel light source or collimating lens system, so that the cost of the optical measuring device is greatly reduced. The large-size area light source is used for providing illumination, the light shielding plate with the customized aperture is matched, a large workpiece can be covered, measurement of a large workpiece is achieved, and the bottleneck that the aperture of a traditional parallel light source is limited is broken through. The physical shielding limits the divergence angle of the light source, converts the surface light source into the quasi-parallel light beam, screens out the nearly parallel light through the light shielding plate, ensures that only paraxial light is allowed to pass through, reduces the interference of oblique light, enables the projection edge of the measured workpiece to be clear without ghosting, guarantees the measurement precision, and does not depend on a complex optical element.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical measurement technical field especially relates to a work piece measuring device. BACKGROUND

[0002] In optical measurement, in order to obtain clear and accurate measurement result, often need to use parallel light source to illuminate work piece. Ideal parallel light source can provide nearly parallel light irradiation, make the projection of work piece have no distortion, facilitate accurate measurement its size and shape. Traditional parallel light source usually adopts parallel light tube, collimating lens or special optical system to generate parallel light beam. However, this kind of parallel light source often has the characteristics of small effective aperture, high cost.

[0003] In addition, in order to measure larger size parts, the required parallel light source aperture must also increase (such as Figure 1 Indicated), but the existing large aperture parallel light source 1 manufacture is complex, and the price is high. This makes the traditional measuring device difficult to meet the demand of optical measurement to larger parts or large area range. As a result, in actual production, when measuring large work piece, either cannot obtain enough parallel light illumination covering the whole work piece, or needs to invest high cost to purchase special large parallel light equipment. Some existing alternative scheme is to use large area area light source (such as LED flat lamp) to illuminate work piece directly. However, the light emitted by ordinary area light source is not parallel, but irradiates object from various angles. For the application needing high precision size measurement, non-parallel light irradiation can cause the edge of projection to be blurred or appear double image, that is, "half shadow" effect, so that the measurement result is inaccurate, such as Figure 2 Indicated. This projection anomaly is mainly caused by the oblique light rays generated by the light source area far away from work piece in area light source. When the size of work piece is larger, the light from different positions of area light source can form different projection positions at the edge of object, cause the projection contour to be virtual, and it is difficult to accurately determine the real boundary.

[0004] Therefore, it is necessary to develop a work piece measuring device to solve the above problems. UTILITY MODEL CONTENT

[0005] The utility model discloses a work piece measuring device to solve the above problems.

[0006] The utility model discloses the following technical scheme to realize the above-mentioned purpose:

[0007] A work piece measuring device, comprising:

[0008] Area light source;

[0009] Light shield plate;Light shield plate is provided with the light transmission hole, and the size of light transmission hole is slightly larger than the external contour size of work piece;

[0010] The double telecentric lens is arranged on the same straight line with the area light source, the light shield, the workpiece and the double telecentric lens.

[0011] Preferably, the centroid of the workpiece, the centroid of the area light source, the centroid of the light passing hole and the centroid of the double telecentric lens are arranged on the same straight line.

[0012] Further, the size of the light passing hole is 2%-5% larger than the size of the workpiece.

[0013] Preferably, the size of the area light source is larger than the size of the light passing hole.

[0014] Preferably, the light shield is arranged close to the area light source.

[0015] Preferably, the area light source is parallel to the light shield.

[0016] The utility model discloses the beneficial effect lies in:

[0017] Low cost: the combination of ordinary area light source and light shield replaces the traditional expensive parallel light source or collimating lens system, greatly reduces the cost of optical measuring device.

[0018] Large area illumination: using large size area light source to provide illumination, cooperating with the light shield of custom aperture, can cover large workpiece, realizes the measurement to larger workpiece, breaks through the bottleneck of traditional parallel light source aperture limitation.

[0019] Clear projection: physical shielding limits the divergence angle of light source, converts the area light source into quasi-parallel light beam, filters out the nearly parallel light through the light shield, ensures that only the near-axis light is allowed to pass, reduces the interference of oblique light, makes the projection edge of the measured workpiece clear without ghosting, ensures the measurement accuracy, and does not rely on complex optical elements.

[0020] Simple and reliable structure: simple structure design, no need for precise optical alignment, convenient implementation and maintenance, high reliability. The light shield can be replaced with different apertures or shapes according to needs, suitable for various measurement tasks, and has strong flexibility. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the prior art when a large parallel light source is used;

[0022] Figure 2 It is a schematic diagram of the prior art when the area light source directly irradiates the workpiece to produce blurred projection;

[0023] Figure 3 It is a structural schematic diagram of the present application;

[0024] Figure 4 It is a schematic diagram of the present application when the area light source irradiates the workpiece to produce clear projection.

[0025] Legend: 1-parallel light source, 2-workpiece, 3-double telecentric lens, 4-area light source, 5-shade, 6-light hole. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without making creative efforts fall within the scope of the present application.

[0028] It should be noted that: similar reference numbers and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0029] In the description of the present application, it should be understood that the terms "upper", "lower", "inner", "outer", "left", "right" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly placed when the product of the present application is used, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0030] In addition, the terms "first", "second" and the like are only used for differentiation in description, and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "provided", "connected" and the like should be understood broadly, for example, "connected" can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements. Those of ordinary skill in the art can understand the specific meaning of the above terms in the present application according to the specific circumstances.

[0032] The utility model discloses a workpiece measuring device, which comprises a workpiece 2, a surface light source 4, an opaque light shield 5 and a double telecentric lens 3.

[0033] As shown in the drawings, a workpiece measuring device comprises: Figure 3

[0034] a surface light source 4;

[0035] an opaque light shield 5, wherein the light shield 5 is provided with a light transmission hole 6, and the size of the light transmission hole 6 is slightly larger than the outer contour size of the workpiece 2;

[0036] a double telecentric lens 3, wherein the surface light source 4, the light shield 5, the workpiece 2 and the double telecentric lens 3 are sequentially arranged on the same straight line.

[0037] In the present application, the light transmitted through the light transmission hole 6 is used to irradiate the workpiece 2, so that the light distribution on the workpiece 2 is approximately parallel, thereby preventing the projection abnormality caused by the oblique light rays away from the workpiece 2 region of the surface light source 4. In the present application, the double telecentric lens is controlled by the object image conjugate parallel light path and the telecentricity, combined with the image side pupil matching and constant magnification, to eliminate the parallax and distortion, realize the linear mapping of the object image size, and can perform the sub-pixel precision size measurement of μm level. The double telecentric lens is also widely used in semiconductor wafer defect detection, FPD micro-circuit measurement, precise gear size online measurement and transparent material internal defect analysis.

[0038] In some embodiments, when multiple objects are measured at the same time, the light shield 5 is provided with a plurality of light transmission holes 6 corresponding to the multiple objects.

[0039] In some embodiments, the light shield 5 is of a replaceable structure, so that the light shield 5 with different aperture or shape can be selected according to different workpieces 2.

[0040] In some embodiments, the center of the workpiece 2, the center of the surface light source 4, the center of the light transmission hole 6 and the center of the double telecentric lens 3 are arranged on the same straight line.

[0041] In some embodiments, the aperture of the light transmission hole 6 is set according to the maximum size of the workpiece 2, and the size of the light transmission hole 6 is 2%-5% larger than the outer contour size of the workpiece 2. Such a structure design ensures that only the light rays from the central region of the surface light source 4 can irradiate the workpiece 2 through the light transmission hole 6. Due to the limitation of the light transmission hole 6, the light rays in the surface light source 4 far from the edge are shielded, and only the light rays close to the optical axis can transmit through the light transmission hole 6 to form a light beam with small angle distribution, realizing the irradiation effect of an approximately parallel light source. The workpiece 2 produces a clear projection profile under the irradiation of such a light beam, avoiding the projection blur or distortion caused by the oblique light when the ordinary surface light source 4 directly irradiates.

[0042] In some embodiments, the size of the surface light source 4 is larger than the size of the light transmission hole 6.

[0043] ​In some embodiments, the light shield 5 is placed close to the area light source 4. The purpose of this arrangement is to block most of the edge light of the area light source 4, so as to reduce the influence of the aperture size on the light divergence angle, and only allow the light from the central region of the area light source 4 to pass through the light passing hole 6 to irradiate the workpiece 2.

[0044] In some embodiments, the area light source 4 is parallel to the light shield 5.

[0045] In some embodiments, the area light source 4 is an LED flat light source or a uniform area light source (fluorescent plate), the light shield 5 is made of metal sheet, black plastic plate or other non-transparent and rigid materials, and the inner side of the light shield 5 is a light-absorbing black surface to reduce stray light.

[0046] During measurement, most of the light emitted by the area light source 4 is blocked by the light shield 5, and only the light from the central region passes through the light passing hole 6 to form a nearly parallel light beam irradiating on the workpiece 2. Since the light passing hole 6 is slightly larger than the workpiece 2, the incident angle of the light irradiating on the edge of the object is limited, so that a clear projection contour is formed on the receiving plane behind the workpiece 2. As shown in Figure 4 , the projected edge of the workpiece 2 is clear and almost consistent with the actual size. Without the light shield 5 (as shown in Figure 2 ), the light from the entire surface of the area light source 4 will irradiate the workpiece 2, and the light of different angles will form overlapping images on the receiving plane, resulting in a blurred area or offset in the projected edge, which increases the measurement error. The embodiment avoids the above problems through a simple structure and can meet the needs of general large workpiece 2 contour size measurement.

[0047] On the basis of the basic structure, the embodiment further describes the optimization method of the size of the light passing hole 6 and the installation distance. For different sizes of workpieces 2 and different measurement accuracy requirements, the degree of approximation of parallel light can be optimized by adjusting the distance between the light shield 5 and the workpiece 2 and the diameter of the light passing hole 6. Generally speaking:

[0048] If a more nearly parallel light effect is desired, the diameter of the light passing hole 6 can be appropriately reduced or the distance between the light shield 5 and the workpiece 2 can be increased. Reducing the aperture will reduce the angle range of the passing light, making the light beam more collimated, but will also reduce the transmitted light intensity; increasing the distance between the light shield 5 and the workpiece 2 will make the light passing through the light passing hole 6 more parallel in angle when reaching the workpiece 2. However, it needs to be balanced that too large distance may require a stronger light source brightness to ensure sufficient illumination intensity.

[0049] Generally, the aperture can be calculated approximately as follows: assuming the maximum angle error of the object edge projection is θ, and the distance between the light shield 5 and the workpiece 2 is L, the diameter D of the light passing hole 6 can be set as approximately: D ≈ d_obj + 2L tan(θ), where d_obj is the maximum size of the workpiece 2. Through this formula, the aperture size can be determined according to the measurement accuracy requirement (i.e. the size of θ). For example, if the angle of the projection light deviating from the vertical direction is not more than 2°, the distance L between the light shield 5 and the workpiece 2 is 500 mm, and the width d_obj of the workpiece 2 is 200 mm, the diameter D of the light passing hole 6 is calculated to be about 200 + 2500 tan(2°) = 200 + 2500*0.01 = 200 + 25 = 225 mm. This means that setting the aperture to 225 mm can meet the accuracy requirement.

[0050] The light shield 5 should generally be installed as close to the area light source 4 as possible, so as to make use of the large light emitting area of the area light source 4, while ensuring that the light passing through the hole is uniform enough. If the light shield 5 is too far from the area light source 4, the effective light source area is effectively reduced, which can reduce the illumination. Therefore, in actual assembly, the light shield 5 can be directly fixed or closely installed on the surface of the area light source 4 to obtain the best effect.

[0051] Through the above optimization method, the present application can balance between the parallel light effect and the light intensity according to the specific measurement requirement, both ensuring the measurement accuracy and maintaining sufficient brightness.

[0052] This embodiment illustrates the method of customizing the light shield 5 according to different measurement objects, and the application expansion of the present application in other optical measurements. For workpieces 2 with irregular shapes or specific purposes, different shapes of light passing holes 6 can be customized:

[0053] Hole shape customization: if the planar projection of the workpiece 2 is approximately rectangular, elliptical or other non-circular shapes, the light passing hole 6 can be designed in a similar shape (such as a rectangular hole, an elliptical hole), which is slightly larger than the corresponding size of the object outline. In this way, the useless light can be more effectively shielded, the light utilization efficiency is increased, and at the same time, all object edges are ensured to be approximately parallelly illuminated. If multiple objects need to be measured at the same time, multiple light passing holes 6 can also be provided on the same light shield 5, each hole corresponding to the position of an object, so as to realize the simultaneous parallel light illumination of a group of objects.

[0054] Materials and structures: the light shield 5 should be made of materials with smooth surface and good rigidity, to ensure the shape and size of the light hole 6 stable, not due to gravity or heat deformation. In addition, the inside of the light shield 5 (towards the light source side) is preferably black to reduce the scattering of light at the edge of the hole. The connection of the light shield 5 and the bracket can be designed to be detachable, so as to quickly replace the light shield 5 with different aperture or shape. For example, it can be designed as a slot type frame, allowing different hole plates to be inserted for use.

[0055] Application extension: the method of the present application can be applied to other optical measurement or imaging scenarios in addition to the transmission type profile measurement (i.e. the light source is on one side of the object and the receiving screen is on the other side to measure the projection of the object). For example, it can be used in reflective measurement as illumination: when parallel incident light is needed to eliminate the effect of uneven surface on reflective measurement, the light shield hole light source of the present application can be placed on the same side of the workpiece 2 for illumination, to irradiate the object surface with approximately parallel light, thereby improving the accuracy of reflective light measurement. In addition, in experiments that need to simulate the parallel light irradiation of the sun, a large area light source with a light shield hole can also be used to simulate the sunlight, thereby reducing the experimental cost.

[0056] The above is only the preferred embodiment of the present application, it should be pointed out that for those skilled in the art, without departing from the technical principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A workpiece measuring device, characterized in that, include: Surface light source; visor; The light-blocking plate is provided with light-transmitting holes, the size of which is slightly larger than the outer dimensions of the workpiece. Double telecentric lens; The surface light source, the light shield, the workpiece, and the dual telecentric lenses are arranged sequentially on the same straight line.

2. The workpiece measuring device according to claim 1, characterized in that, The centroids of the workpiece, the surface light source, the light aperture, and the dual telecentric lenses are all placed on the same straight line.

3. The workpiece measuring device according to claim 1, characterized in that, The size of the light-transmitting hole is 2% to 5% larger than the outer dimensions of the workpiece.

4. The workpiece measuring device according to claim 1, characterized in that, The size of the surface light source is larger than the size of the light-passing aperture.

5. The workpiece measuring device according to claim 1, characterized in that, The light-shielding plate is placed close to the surface light source.

6. The workpiece measuring device according to claim 1, characterized in that, The surface light source is parallel to the light shield.

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