Optical tool reference and apparatus for determining an orientation and / or a relative position of cameras to each other

Abstract

Optical tool reference (200) for determining an orientation and / or position of at least one first camera (410) relative to at least one second camera( 510) for aligning one or more components, such as a die, with one or more substrates, before an attachment or joining such as a bonding.

Description

[0001] Besi Switzerland AG, Hinterbergstr. 32a, CH - 6312 Steinhausen, Switzerland

[0002] Optical tool reference and apparatus for determining an orientation and / or a relative position of cameras to each other

[0003] Cross reference to related Application

[0004] The International application claims the priority of DE 102023 133 895.1 filed on 2023-12-04; this application is incorporated by reference herein in its entirety.

[0005] Technical Field

[0006] The present disclosure relates to an optical tool reference for determining at least one orientation and / or position of at least one first camera relative to at least one second camera, and an apparatus comprising one or more optical reference tools. In particular, the apparatus may be arranged to use one or more determined orientations and / or positions for aligning one or more components, such as a die, with one or more substrates, before an attachment or joining such as a bonding.

[0007] State of the Art

[0008] From the state-of-the-art, similar apparatus and components are known, such as US 2021 / 0195816. This document discloses an apparatus comprising a bond head with a component gripper, a first drive system for moving a carrier over relatively long distances, a second drive system which is attached to the carrier for moving the bond head back and forth between a nominal working position and a stand-by position, a drive attached to the bond head for rotating the component gripper or a rotary drive for rotating the substrate about an axis, at least one substrate camera attached to the carrier and at least one component camera. Either the second drive system is also designed to perform high-precision correction movements with the bond head, or a third drive system is provided to perform high-precision correction movements with the substrate. At least one reference mark is attached to the bond head or the component gripper. In systems that use two or more cameras for alignment, frequent calibration may be required to be able to compare or combine measurement results made by different cameras, particularly when comparing or combining measurements from a substrate camera (or look-down camera) with measurements from a component camera (a look-up camera). The solution described in US 2021 / 0195816 arranges the at least one reference mark to be measurable using the substrate camera and using the component camera, allowing the two camera measurement systems to share a common reference point. However, there is an increasing need to further reduce unwanted offsets between camera measurement systems as the attachment accuracy to be consistently achieved increases greatly.

[0009] Technical Problem to be solved

[0010] It is an object of this disclosure to provide an improved optical reference tool.

[0011] Solution

[0012] This technical problem is solved by technical means according to the independent claims. Technically advantageous embodiments are the subject of the dependent claims, the description and the drawings.

[0013] Description of the Invention

[0014] Advantageously, an optical tool reference is provided for determining at least one orientation and / or position of one or more first cameras relative to one or more second cameras, the optical tool reference comprising: a mark carrier with a first carrier surface and a second carrier surface, wherein the second carrier surface is opposite to the first carrier surface. The optical tool reference comprises one or more first reference marks on or proximate the first carrier surface, and one or more second reference marks on or proximate the second carrier surface. The mark carrier comprises one or more imaging portions. The one or more first reference marks are arranged to allow one or more first images to be made by the one or more first cameras through the one or more imaging portions if the one or more first cameras are facing the second carrier surface. The one or more second reference marks are arranged to allow one or more second images to be made through the one or more imaging portions by the one or more second cameras if the one or more second cameras are facing the first carrier surface. The one or more first images are arranged to provide a first orientation and / or position of the one or more first cameras relative to the one or more first reference marks. The one or more second images are arranged to provide a second orientation and / or position of the one or more second cameras relative to the one or more second reference marks.

[0015] Advantageously, an average refractive index (n) of the imaging portions is approximately 2, or in the range of 1 .0 to 3.0; or 1 .5 to 2.5; or 1 .7 to 2.3; or 1 .75 to 2.25; or 1.8 to 2.2; or 1.85 to 2.15; or 1.9 to 2.1 ; or 1.95 to 2.05.

[0016] Advantageously, the one or more first reference marks are arranged to allow one or more further images to be made by the one or more second cameras if the one or more second cameras are facing the first carrier surface to provide a further orientation and / or position of the one or more second cameras relative to the one or more first reference marks.

[0017] Advantageously, the one or more second reference marks are arranged to allow one or more further images to be made by the one or more first cameras if the first camera is facing the second carrier surface to provide a further orientation and / or position of the one or more first cameras relative to the one or more second reference marks.

[0018] Advantageously, the one or more first reference marks and the one or more second reference marks are arranged to allow one or more further images to be made by the one or more second cameras if the one or more second cameras are facing the first carrier surface to provide a further orientation and / or position of the one or more second cameras relative to the optical tool reference.

[0019] Advantageously, the one or more second reference marks are arranged to form with the one or more first reference marks one or more patterns, wherein the one or more patterns are arranged to be recognizable in the further images.

[0020] Advantageously, the one or more second reference marks and the one or more first reference marks are arranged to be separated in the further images.

[0021] Advantageously, the one or more first reference marks and the one or more second reference marks are arranged to allow one or more further images to be made by the one or more first cameras if the one or more first cameras are facing the second carrier surface to provide a further orientation and / or position of the one or more first cameras relative to the optical tool reference.

[0022] Advantageously, the one or more first reference marks are arranged to form with the one or more second reference marks one or more patterns, wherein the one or more patterns are arranged to be recognisable in the further images.

[0023] Advantageously, the one or more first reference marks and the one or more second reference marks are arranged to be separated in the further images.

[0024] Advantageously, the optical tool reference comprises two or more first reference marks, wherein the two or more first reference marks being arranged to be substantially different in the one or more first images; and the one or more first images being arranged to provide a reference mark orientation and / or a reference mark position.

[0025] Advantageously, the optical tool reference comprises two or more second reference marks, wherein the two or more second reference marks being arranged to be substantially different in the one or more second images; and the one or more second images being arranged to provide a reference mark orientation and / or a reference mark position.

[0026] Advantageously, the optical tool reference comprises one or more code marks, arranged to allow one or more code images to be made by a camera of the one or more code marks, wherein the one or more code images are arranged to provide one or more parameters of the one or more code marks selected from the group comprising: an orientation, a position, a parameter, a value, a number, or any combination thereof.

[0027] Advantageously, the one or more imaging portions comprise a material selected from the group comprising: a glass, a Lanthanum dense flint glass, a crystal, a plastic, a semiconductor, silicon, a liquid, a metal, or any combination thereof.

[0028] Advantageously, the mark carrier is comprised in a portion of a component, a substrate, a wafer, a mask, a lens, a mirror, a filter, a diffractive optic, a phase plate, a diffuser, a micro-lens array, a waveplate, a zone plate, a plate, a thin plate, a plane parallel plate, a beam divider, a beam combiner, a beam splitter, an image sensor, a prism, a cube, a right-angle prism, a grating, a retroreflector, a quarter-wave plate, a half-wave plate, a tool fiducial, a gripper fiducial, a substrate fiducial, a component fiducial, a grating, a scale, a dichroic filter, a polarizing filter, or any combination thereof.

[0029] Advantageously, an apparatus is provided for aligning one or more components with one or more substrates before attaching, the apparatus comprising: a pick and place actuator arranged to be disposed at an attaching position, the pick and place actuator comprising a gripper for releasably attaching to the one or more components. The apparatus comprises: a feeding unit for providing one or more substrates to the attaching position. The one or more substrates comprise one or more substrate marks. The apparatus comprises one or more optical tool references described herein, arranged to allow an orientation and / or position of one or more cameras relative to one or more other cameras to be determined. The apparatus comprises one or more first cameras, arranged as one or more look-up cameras for making the one or more first images of the one or more first reference marks. The apparatusd comprises one or more second cameras, arranged as one or more look-down cameras for making the one or more second images of the one or more second reference marks.

[0030] Advantageously, the apparatus is arranged to determine a first orientation and / or position of the one or more first cameras relative to the one or more first reference marks using the one or more first images, to determine a second orientation and / or position of the one or more second cameras relative to the one or more second reference marks using the one or more second images and to determine at least one camera alignment correction using the first orientation and / or position with the second orientation and / or position.

[0031] Advantageously, a method is provided for aligning one or more components with one or more substrates before attaching, the method comprising the steps of providing a gripper arranged to be disposed at an attaching position, the gripper being arranged for releasably attaching to the one or more components. The method comprises providing one or more optical tool references as described herein, arranged to allow an orientation and / or position of one or more cameras relative to one or more other cameras to be determined. The method comprises providing one or more substrates to the attaching position, wherein the one or more substrates comprise one or more substrate marks. The method comprises using one or more look-down cameras to make one or more images of one or more optical tool references. The method comprises determining a first orientation and / or position using the one or more first images of the one or more first reference marks. The method comprises using one or more look-up cameras to make one or more images of the one or more optical tool references. The method comprises determining a second orientation and / or position using the one or more second images of the one or more second reference marks. The method comprises determining a camera alignment correction using the first orientation and / or position with the second orientation and / or position. The method comprises moving the gripper to the attaching position. The method comprises at the attaching position using the one or more look-down cameras to make one or more substrate mark images of the one or more substrate marks. The method comprises determining a substrate mark orientation and / or position using the one or more substrate mark images of the one or more substrate marks. The method comprises determining a substrate mark alignment correction using the substrate mark orientation and / or position.

[0032] Advantageously, the method comprises further the steps of determining the first orientation and / or position of the one or more first cameras relative to the one or more first reference marks using the one or more first images. The method comprises determining the second orientation and / or position of the one or more second cameras relative to the one or more second reference marks using the one or more second images. The method comprises determining at least one camera alignment correction using the first orientation and / or position with the second orientation and / or position.

[0033] Further advantages and characteristics result from the following figures, including

[0034] FIG. 1 , which depicts a schematic front view of the relevant parts of an apparatus for aligning one or more components with one or more substrates before and / or during attaching;

[0035] FIG. 2, which depicts a schematic side view of the relevant parts of the pick and place actuator of an apparatus for aligning one or more components with one or more substrates before and / or during attaching; FIG. 3A, which depicts a schematic cross-section of a look-down camera for making images of one or more reference marks comprised in an optical reference tool;

[0036] FIG. 3B, which depicts a schematic cross-section of a look-up camera for making images of one or more reference marks in an optical reference tool;

[0037] FIG. 4A, which depicts a schematic cross-section through an optical reference tool;

[0038] FIG. 4B, which depicts a schematic cross-section through a tilted portion of an optical reference tool;

[0039] FIG. 5A, FIG. 5B and FIG. 5C which depict one or more patterns arranged to be recognizable in one or more images;

[0040] FIG. 6A, FIG. 6B, FIG. 6C which depict one or more patterns arranged to be recognizable in one or more images;

[0041] FIG. 7, which depicts a schematic cross-section of a look-down camera and a lookup camera, both for making images of one or more reference marks comprised in an optical reference tool; and

[0042] FIG. 8A to 80, which depict schematic cross-section views of the lines of sight of a look-down camera and a look-up camera through a tilted portion of an optical reference tool.

[0043] Detailed description of the figures

[0044] In the figures, a first axis 910, a second axis 920 and a third 930 axis are depicted. The first axis 910 is perpendicular to the second axis 920, and the third axis 930 is perpendicular to both the first axis 910 and the second axis 920. During use, the first axis 910 is assumed to direct in an Y direction, the second axis 920 is assumed to direct in an X direction and the third axis 930 is assumed to direct in a Z direction. Conventionally, in use, the axes in the corresponding directions are therefore named as Y-axis 910 and X-axis 920 and are substantially horizontal, horizontal or approximately horizontal.

[0045] Functionally, the X-axis 920 and Y-axis 910 may be interchanged. Conventionally, in use, the axis in the corresponding direction is therefore named as Z-axis 930 and is substantially vertical, vertical or approximately vertical. To clarify the description of the different components, the figures depict parts in these conventional orientations. To clarify the description of the different components, some relative terms have been used, such as upper, side and base to match this convention, “for” should be interpreted as “suitable for”.

[0046] The apparatus described in this disclosure may arranged by a skilled person to operate at different deviations from the conventional orientations and nominal coordinate axes.

[0047] FIG. 1 depicts a schematic cross-section, shown from a side, of relevant parts of an apparatus 100 suitable for aligning one or more components 600 with one or more substrates 300 before and / or during attaching according to any of the methods disclosed herein. More particularly, the apparatus 100 is shown looking towards a plane comprising the X-axis 920, nominally indicated as having a positive direction from left to right, and comprising the Z-axis 930, nominally indicated as having a positive direction from bottom to top. The Y-axis 910 is nominally depicted as having a positive direction into the drawing plane from the viewer's perspective.

[0048] For example, the apparatus 100 may be an attachment apparatus such as a die bonding apparatus. Typically dies are rectangular in shape, but rounded or trapezoidal shapes are also possible.

[0049] In general, a degree of alignment may be corrected if at least a small degree of relative movement is possible in one or more directions between a component and a substrate, which may be possible during an initial stage of attaching. This relative movement may be approximately linear along one or more axes 910, 920, 930 and / or rotational around one or more axes 910, 920, 930. No significant degree of alignment is possible after one or more components 600 have been rigidly attached with a substrate 600.

[0050] The one or more substrates 300 comprise one or more substrate marks (or substrate alignment targets), suitable for determining a orientation and / or position of the one or more substrates 300, whereby one or more components 600 may be mounted and attached with a precision in the micrometer range or sub-micrometer range. The one or more substrate marks may be any suitable alignment target. For example, a substrate mark may be one or more physical features of at least a portion of a substrate, one or more optical characteristics of at least a portion of a substrate, at least a portion of a fiducial, or any combination thereof. The methods and apparatus described herein for aligning one or more components 600 is not limited to dies. For example, a component may be a die, a semiconductor package, a chip, a flip chip, an integrated circuit, a further substrate, an optical element, an electronic element, an electro-optical element, or any combination thereof. For example, one component may be attached to one substrate. For example, one or more components 600 may be attached to one substrate. For example, one component may be attached to one or more substrates 300.

[0051] During one or more steps of the methods described herein, the apparatus may be preconfigured to perform one or more predetermined operations to improve throughput. Additionally or alternatively, the apparatus may be preconfigured to control one or more operations during use.

[0052] The one or more substrates 300 may be one or more metallic substrates, also described as one or more lead frames, where one or more components 600 are soldered onto islands arranged one after the other and optionally next to one another. However, the methods and apparatus described herein are not limited to lead frames - the one or more substrates 300 may be any object having one or more attachable face and one or more device or attaching position. For example, a substrate may be a metallic substrate, a substrate strip, a lead frame, a wafer, a further component, or any combination thereof. The one or more substrates 300 may also be described as one or more media.

[0053] FIG. 1 depicts the apparatus 100 comprising a pick and place actuator 150, an optional feeding unit 120 for providing the one or more components 600, and an optional further feeding unit 140 for providing the one or more substrates 300. The feeding unit 120 is positioned at a loading position 820 for component loading, and may comprise a component handling system, such as a wafer or tape. The further feeding unit 140 is positioned at an attaching position 800 for component attaching. Optionally, the apparatus 100 may be configured as a bonding apparatus by suitable modifications, including configuring the pick and place actuator 150 as a bond head.

[0054] FIG. 1 depicts an example of a pick and place drive, comprising a first drive system 111 for a drive member 130, and a second drive system 112 for the pick and place actuator 150. The second drive system 112 is attached to the drive member 130. Any suitable drive configuration may be included in the apparatus 100. For example, the first drive system 111 may be arranged to move the drive member 130 positively and negatively along the X-axis 920, and the second drive system 112 may be arranged to move the pick and place actuator 150 positively and negatively along the Y-axis 910, whereby the pick and place actuator 150 may be moved between the loading position 820 and the attaching position 800.

[0055] As depicted in FIG. 1 , the apparatus includes one or more first cameras 410 arranged as one or more look-up cameras, and further includes one or more second cameras 510 arranged as one or more look-down cameras. In the context of this disclosure, look-up means that the camera is approximately pointed in the positive direction of the Z-axis 930. In the context of this disclosure, look-down means that the camera is approximately pointed in the negative direction of the Z-axis 930. The one or more look-up cameras 410 are arranged to make images of an attaching surface of a component during attachment to the gripper 160, whereby a skilled person may also refer to it as a component camera 410. The one or more look-down cameras 510 comprises one or more illumination radiation source 530. The one or more look-down cameras 510 are arranged to illuminate an attaching surface of one or more substrates 300 and arranged make images of the one or more substrates, whereby a skilled person may also refer to it as a substrate camera 510. In this example, the one or more first cameras 410 and the one or more second cameras 510 are depicted respectively in a look-up and look-down configuration. However, embodiments of an optical tool reference 200 described herein will operate in any orientation. Additionally, it is not necessary for the one or more first cameras 410 and the one or more second cameras 510 to face each other in a direct line or to be perpendicular to the optical tool reference 200. Operation of an optical tool reference 200 as described herein may be performed in any arrangements that allow the cameras to each image one or more reference marks.

[0056] Each camera 410, 510 is arranged as an optical imager, and comprises one or more image sensors (not depicted), and comprises one or more optical elements (not depicted). The one or more image sensors may use any suitable optical detection technique, such as CMOS. Where necessary, optical beam paths may be deflected using one or more suitably-configured deflecting mirrors (not depicted). The radiation detectors may be arranged for detecting any convenient wavelengths, such as a UV (ultra-violet) wavelength, a visible wavelength, an IR (infra-red) wavelength, or any combination thereof.

[0057] FIG. 1 depicts an example of an apparatus comprising one or more look-down cameras 510. In the example depicted, the one or more look-down cameras 510 are attached to the drive member 130 of the pick and place drive.

[0058] As depicted in FIG. 1 , the pick and place actuator 150 comprises a component gripper 160, arranged to releasably attach to one or more components 600 during use, and to retain the attachment during movements of the pick and place actuator 150 and / or the gripper 160. The gripper 160 is, for example, vacuum-operated whereby a degree of suction may be used to retain one or more components 600 in the gripper 160. The gripper 160 is arranged to be rotatable about the Z-axis 930.

[0059] The apparatus 100 is arranged to provide at least a portion of an attaching process (not depicted) at the attaching position 800. During the at least a portion of the attaching process, the one or more components 600 are in contact with the one or more substrates 300, allowing one or more attaching operations to be performed on at a least a portion of the one or more attaching surfaces (not depicted) of the one or more components 600 and / or one or more substrates 300. The one or more attaching surfaces are typically at least a portion of a mutual region of contact between the one or more components 600 and / or one or more substrates 300.

[0060] In the example depicted in FIG. 1 and FIG. 2, the range of motion of the second drive system 112 is typically small or very small compared to the range of motion of the first drive system 111. The second drive system 112 is arranged to move the pick and place actuator 150 to one or more processing positions, and arranged to provide high-precision correction movements of the pick and place actuator 150 in two different directions 910, 920. For this purpose, it is sufficient if the range of motion of the second drive system 112 is relatively long in along the X-axis 920, and relatively short along the Y axis 910. short in the other horizontal direction . The range of motion along the X-axis 920 may be a few tens of millimeters, for example 20 mm or 30 mm or more, the range of motion along the Y-axis 910 may be only a few micrometers. The apparatus 100 is arranged at the attaching position 800 to move one or more components 600, attached to the gripper 160, along the Z-axis 930 towards one or more substrates 300, and to keep a position of close proximity between an attaching surface of the one or more components 600 and an attaching surface of the substrate 300 while images are made. For example, the average separation between the component attaching surface and the substrate attaching surface is 50 - 200 pm.

[0061] FIG. 2 depicts a schematic cross-section, shown from a side, of the pick and place actuator 150 already described in relation to FIG. 1. More particularly, the pick and place actuator 150 is shown looking towards a plane comprising the Y-axis 910, nominally indicated as having a positive direction from left to right, and the Z-axis 930, nominally indicated as having a positive direction from bottom to top. The X-axis 920 is nominally depicted as having a positive direction out of the drawing, towards the viewer. As depicted in FIG. 2, one or more components 600 are retained by the gripper 160.

[0062] The pick and place actuator 150 comprises one or more look-down cameras 510 arranged to make one or more images of an attaching surface of the one or more substrates 300. The one or more look-down cameras 510 depicted in the example of FIG. 2 is arranged to make one or more images of one or more optical tool references 200 (or tool references). In other words, the one or more optical tool references 200 are positioned in the look-down camera field-of-view 540.

[0063] The one or more tool references 200 are positioned on an optical axis 520 of the one or more look-down cameras 510. The one or more tool references 200 are arranged to allow an orientation and / or position of the gripper 160 to be determined by the one or more look-down cameras 510. For example, the one or more tool references 200 may be comprised in the pick and place actuator 150, attached to the pick and place actuator 150, comprised in the gripper 160, attached to the gripper 160, or any combination thereof.

[0064] Optionally, the one or more look-down cameras 510 may comprise one or more illumination radiation sources 530, arranged to provide illumination radiation suitable for making images of one or more portions of the one or more tool references 200. Preferably, at least one optical tool reference 200 is arranged to receive and to at least partially transmit radiation from one or more look-up cameras and / or from one or more look-down cameras. Additionally, or alternatively, an optical tool reference 200 may comprise an illumination radiation source, arranged to provide radiation for one or more camera images.

[0065] As depicted in FIG. 1 and FIG. 2, the apparatus 100 is arranged such that the one or more tool references 200 may be imaged by the one or more look-up cameras 410. For example, imaging by the one or more look-up cameras 410 may occur at the same positions of the pick and place actuator 150 as imaging by the one or more look-down cameras 510. For example, imaging by the one or more look-up cameras 410 may occur at overlapping positions of the pick and place actuator 150 as imaging by the one or more look-down cameras 510. For example, imaging by the one or more look-up cameras 410 may occur at different positions of the pick and place actuator 150 as imaging by the one or more look-down cameras 510. For example, imaging by the one or more look-up cameras 410 may occur at the same moment in time as imaging by the one or more look-down cameras 510. For example, imaging by the one or more look-up cameras 410 may occur at different moments in time as imaging by the one or more look-down cameras 510. For example, imaging by the one or more look-up cameras 410 may occur at overlapping moments in time as imaging by the one or more look-down cameras 510.

[0066] In the example depicted in FIG. 1 and FIG. 2, the first drive system 111 is arranged to transport the pick and place actuator 150 over relatively long distances, namely from the loading position 820, where the pick and place actuator 150 and gripper 160 receive one or more components 600 from the feeding unit 120, to the attaching location 800, where the pick and place actuator 150 and gripper 160 place the one or more components 600 on one or more substrates 300. The requirements for the position accuracy of the first drive system 111 are relatively modest, a position accuracy of + / - 10 pm is usually sufficient. In the example depicted in FIG. 1 , the first drive system 111 is designed as a so-called “gantry” with two or more mechanically highly stable axes of motion, of which two axes of motion allow movements of the drive member 130 along axis 910 and along axis 920, both axes running perpendicular to each other.

[0067] Typically, movements of the pick and place actuator 150 along the Z-axis 930 are required to remove a component 600 from the feeding unit 120, and also to place the component 600 in an intended attaching position on one or more substrates 300. This movement along the Z-axis 930 may be performed in many different ways, such as providing the first drive system 111 with a third, stable or highly stable axis of motion arranged to provide movement along the Z-axis 930 of the drive member 130. Additionally or alternatively, the second drive system 112 may be provided with an additional, high-precision drive arranged to provide movements of the pick and place actuator 150 along the Z-axis 930. Additionally or alternatively, the pick and place actuator 150 may comprise a high-precision drive arranged to provide movements of the gripper 160 along the Z-axis 930.

[0068] In the example depicted in FIG. 1 and FIG. 2, the second drive system 112 is arranged to move the pick and place actuator 150 between processing positions, and also to enable high-precision correction movements of the pick and place actuator 150 in two different directions along the axis 910 and / or along the axis 920.

[0069] In the example depicted in FIG. 2, the pick and place actuator 150 optionally comprises a drive 113 for the rotation of the component gripper 160 around the Z- axis 930. Additionally or alternatively, the feeding unit 120 may be arranged to rotate one or more components 600 about the Z-axis 930 to reduce or eliminate at least a degree of angular error. Additionally or alternatively, the further feeding unit 140 may be arranged to rotate one or more substrates 300 about the Z-axis 930 to reduce or eliminate at least a degree of angular error.

[0070] FIG. 3A depicts a schematic cross-section, shown from a side, of an example of a look-down camera 510 arranged for making images of one or more reference marks comprised in the optical reference tool 200. Similarly, FIG. 3B depicts a schematic cross-section, shown from a side, of an example of a look-up camera 410 arranged for making images of one or more reference marks comprised in the optical reference tool 200. Similarly, FIG. 7 depicts a schematic cross-section, shown from a side, of an example of a look-up camera 410 and an example of a look-down camera 510 arranged for making images at different times, at the same time, and / or approximately simultaneously, of one or more reference marks comprised in the optical reference tool 200. More particularly, the one or more cameras are shown looking towards a plane comprising the Y-axis 910, nominally indicated as having a positive direction from left to right, and the Z-axis 930, nominally indicated as having a positive direction from bottom to top. The X-axis 920 is nominally depicted as having a positive direction out of the drawing, towards the viewer.

[0071] The optical tool reference 200 comprises a mark carrier 250 portion with a first carrier surface 251 , and a second carrier surface 252. The second carrier surface 252 is arranged to be opposite to the first carrier surface 252. The optical reference tool 200 comprises one or more first reference marks 261 on or proximate the first carrier surface 251 , and comprises one or more second reference marks 262 on or proximate the second carrier surface 252. Optionally, the first carrier surface 251 and the second carrier surface 252 may be approximately parallel in one or more regions where the one or more reference marks 261 , 262 are located.

[0072] As depicted in FIG. 3B, the optical reference tool 200 is arranged to determine a first orientation and / or position of the one or more look-up cameras 410 relative to the one or more first reference marks 261. As depicted in FIG. 3A, the optical reference tool 200 is arranged to determine a second orientation and / or position of the one or more one or more look-down cameras 510 relative to the one or more second reference marks 262. As depicted in FIG. 7, the optical reference tool 200 is arranged to perform the determinations depicted in FIG.3A and / or the determinations depicted in FIG. 3B.

[0073] The determinations in FIG. 3A and FIG. 3B may thus be performed at different times, at similar times, at the same time, or approximately simultaneously, or any combination thereof. It may be advantageous to perform the determinations at similar times, at the same time, or approximately simultaneously, whereby at least one environmental condition, such as a temperature, a humidity or a pressure, for both determinations are similar, the same, or identical.

[0074] Subsequently, at least one first orientation and / or position may be used with at least one second orientation and / or position to determine at least one camera alignment correction. This correction may be applied in software and / or hardware to modify and / or adapt at least one optical and / or physical characteristic of at least one optical component.

[0075] The one or more first reference marks 261 are arranged to allow one or more first images to be made by the one or more look-up cameras 410 through the one or more imaging portions if the one or more look-up cameras 410 are facing the second carrier surface 252 as depicted in FIG. 3B and FIG. 7. The one or more second reference marks 262 are arranged to allow one or more second images to be made through the one or more imaging portions by the one or more look-down cameras 510 if the one or more look-down cameras 510 are facing the first carrier surface 251 as depicted in FIG. 3A and Fig. 7. As depicted in FIG. 3B and FIG. 7, the optical reference tool 200 is positioned in a field-of-view 440 of the one or more look-up cameras 410, with a portion of the optical reference tool 200 on a look-up optical axis or plane 420. The one or more look-up cameras 410 are arranged to collect radiation directed towards the one or more look-up cameras 410. The one or more look-up cameras 410 are arranged to make one or more first images of the one or more first reference marks 261 . The one or more first images are arranged to provide a first orientation and / or position of the one or more look-up cameras 410 relative to the one or more first reference marks 261 . In this example, the apparatus 100 is therefore arranged to determine the first orientation and / or position of the one or more look-up cameras 410 relative to the one or more first reference marks 261 using the one or more first images.

[0076] As depicted in FIG. 3A and FIG. 7, the optical reference tool 200 is positioned in a field-of-view 540 of the one or more look-down cameras 510, with a portion of the optical reference tool 200 on a look-down optical axis 520. The one or more lookdown cameras 510 are arranged to collect radiation directed towards the one or more look-down cameras 510. The one or more look-down cameras 510 are arranged to make one or more second images of the one or more second reference marks 262. The one or more second images are arranged to provide a second orientation and / or position of the one or more look-down cameras 510 relative to the one or more second reference marks 262. In this example, the apparatus 100 is arranged to determine the second orientation and / or position of the one or more one or more look-down cameras 510 relative to the one or more second reference marks 262 using the one or more second images.

[0077] The cameras 410, 510 comprise one or more image sensors using any suitable optical detection technique, such as CMOS. In the context of this closure, directing should be understood as making use of one or more physical and / or optical properties to determine, to a substantial degree, an optical path of beam. For example, directing may be reflecting, diffracting, transmitting or any combination thereof.

[0078] FIG. 4A depicts an enlarged schematic cross-section through the optical reference tool 200 depicted in FIG. 3A, FIG. 3B and FIG. 7. More particularly, the optical reference tool 200 is shown looking towards a plane comprising the Y-axis 910, nominally indicated as having a positive direction from left to right, and the Z-axis 930, nominally indicated as having a positive direction from bottom to top. The X-axis 920 is nominally depicted as having a positive direction out of the drawing, towards the viewer.

[0079] As depicted in the example of FIG. 4A, the optical reference tool 200 comprises the mark carrier 250 with one or more imaging portions. In example of FIG. 4A, the mark carrier 250 is approximately homogenous with contiguous imaging portions 255 making up most of the mark carrier 250. For example, the mark carrier 250 may be at least a portion of a glass plate.

[0080] In general, if a mark carrier 250 is tilted with respect to a camera optical axis 420, 520, measurements made by the cameras 410, 510 may have an unwanted offset depending on the thickness of the one or more imaging portions, the refractive index of materials used in the one or more imaging portions, and a tilt angle of the mark carrier 250 from a camera optical axis 420, 520. If these parameters are known, a predetermined offset may be applied to provide a suitable correction.

[0081] In practice, however, unexpected and undetected tilts may occur due to, for example, mechanical tolerances, thermal drifts, manufacturing limitations, inaccuracy of motion drives, and / or actuator movement. These unwanted tilts may cause unexpected and undetected offsets in the camera measurement results. FIG. 4B depicts an enlarged schematic cross-section through a tilted portion of a mark carrier 250. FIG. 4B depicts the one or more first reference marks 261 on or proximate the first carrier surface 251 being arranged to allow one or more first images to be made by one or more look-up cameras (not depicted), facing the second carrier surface 252, through one or more imaging portions of the mark carrier 250. Additionally or alternatively, the one or more first reference marks 261 on or proximate the first carrier surface 251 may be arranged to allow one or more further images to be made by one or more look-down cameras (not depicted), facing the first carrier surface 251 , directly and without passing through a substantial imaging portion of the mark carrier 250. FIG. 4B further depicts the one or more second reference marks 262 on or proximate the second carrier surface 252 arranged to allow one or more second images to be made by one or more look-down cameras (not depicted), facing the first carrier surface 251 , through one or more imaging portions of the mark carrier 250. Additionally or alternatively, the one or more second reference marks 262 on or proximate the second carrier surface 252 may be arranged to allow one or more further images to be made by one or more look-up cameras (not depicted), facing the second carrier surface 252, directly and without passing through a substantial imaging portion of the mark carrier 250. In the schematic depiction of FIG. 4B, the mark carrier 250 has an average thickness mark carrier thickness 270, and is arranged at an average mark carrier tilt angle 255 which has been exaggerated for this explanation. The mark carrier tilt angle 255 is an average angular deviation from an axis or plane perpendicular to an optical axis or plane (not depicted). In general, the optical and physical characteristics of the imaging portions of the mark carrier 250 cause a measurement offset, or measurement error, due to refraction.

[0082] FIG. 8A to 8C depict enlarged schematic cross-section views of the lines of sight of one or more look-down cameras 510 and one or more look-up cameras 410 through a tilted portion of a further mark carrier 1250. The further mark carrier 1250 is the same as the mark carrier 250 depicted in FIG. 4A and 4B, except for a different arrangement of reference marks 261 , 262. FIG. 8A depicts the one or more look-up cameras 410 being arranged on a look-up camera optical axis or optical plane 420 facing the second carrier surface 252.. FIG. 8A further depicts the one or more lookdown cameras 510 being arranged on a look-down camera optical axis or optical plane 520 facing the first carrier surface 251 . In the schematic depiction of FIG. 8A, the further mark carrier 1250 has an average thickness mark carrier thickness 270, and is arranged at an average mark carrier tilt angle 255 which has been exaggerated for this explanation. The mark carrier tilt angle 255 is an average angular deviation from an axis or plane perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520. In the example depicted in FIG. 8A, the one or more first reference marks 261 on or proximate the first carrier surface 251 are arranged to allow one or more further images 555 to be made by the one or more look-down cameras 520, facing the first carrier surface 251 , directly and without passing through a substantial imaging portion of the further mark carrier 1250. Similarly, the one or more second reference marks 262 on or proximate the second carrier surface 252 are arranged to allow one or more further images 455 to be made by one or more look-up cameras 410, facing the second carrier surface 252, directly and without passing through a substantial imaging portion of the further mark carrier 1250. In FIG. 8A, at least one of the first reference marks 261 and at least one of the second reference marks 262 are both arranged on a mutual axis or plane 265, arranged to be approximately perpendicular to the first carrier surface 251 and / or the second carrier surface 252. The mutual axis or plane 265 is thereby arranged to locate the at least one first reference mark 261 and the at least one second reference mark 262 on the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 if the further mark carrier 1250 is arranged approximately perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520. The further mark carrier 1250 is arranged approximately perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 if the average mark carrier tilt angle 255 is approximately zero. If the average mark carrier tilt angle 255 is approximately zero, a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is also approximately zero. As depicted in FIG. 8A, the average mark carrier tilt angle 255 is significantly greater than zero, whereby a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is also significantly greater than zero. In general, one or more optical and / or physical characteristics of the imaging portions of the mark carrier 250 cause a measurement offset or measurement error 290, between an orientation and / or position of the at least one first reference marker 261 n relative to the at least one second reference marker 262. In the example depicted in FIG. 8A, the measurement offset 290 is determined to a high degree by an average mark carrier thickness 270 and average mark carrier tilt angle 255.

[0083] FIG. 8B depicts the one or more look-up cameras 410 being arranged on a look-up camera optical axis or optical plane 420 facing the second carrier surface 252. FIG. 8B further depicts the one or more look-down cameras 510 being arranged on a look- down camera optical axis or optical plane 520 facing the first carrier surface 251 . In the example depicted in FIG. 8B, the look-down camera optical axis or plane 520 is deflected by refraction to a deflected look-down camera axis or plane 525. In the schematic depiction of FIG. 8B, the further mark carrier 1250 has an average thickness mark carrier thickness 270, and is arranged at an average mark carrier tilt angle 255 which has been exaggerated for this explanation. The mark carrier tilt angle 255 is an average angular deviation from an axis or plane perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520. In the example depicted in FIG. 8B, the one or more second reference marks 262 on or proximate the second carrier surface 252 are arranged to allow one or more second images 550 to be made by the one or more look-down cameras 520, facing the first carrier surface 251 , through a substantial imaging portion of the further mark carrier 1250. The one or more second reference marks 262 on or proximate the second carrier surface 252 are further arranged to allow one or more further images 455 to be made by one or more look-up cameras 410, facing the second carrier surface 252, directly and without passing through a substantial imaging portion of the further mark carrier 1250. In FIG. 8B, none of the first reference marks are depicted. The further mark carrier 1250 is arranged approximately perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 if the average mark carrier tilt angle 255 is approximately zero. If the average mark carrier tilt angle 255 is approximately zero, a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is also approximately zero. As depicted in FIG. 8B, the average mark carrier tilt angle 255 is significantly greater than zero, whereby a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is also significantly greater than zero. “Significantly greater than zero” means generally known a tilt deviation of a minimum of 1 millidegree, 0.001 degree [m°] for the shown example.

[0084] In general, one or more optical and / or physical characteristics of the imaging portions of the mark carrier 250 cause a measurement offset or measurement error 290, between an orientation and / or position of the at least one first reference marker 261 relative to the at least one second reference marker 262. In the example depicted in FIG. 8B, the measurement offset 290 is determined to a high degree by an average mark carrier thickness 270, an average mark carrier tilt angle 255 and an average refractive index of the imaging portions of the further mark carrier 250. For example, an average refractive index of the imaging portions depicted in FIG. 8B may be approximately 1 .5.

[0085] FIG. 8C depicts the one or more look-up cameras 410 being arranged on a look-up camera optical axis or optical plane 420 facing the second carrier surface 252. FIG. 8C further depicts the one or more look-down cameras 510 being arranged on a look-down camera optical axis or optical plane 520 facing the first carrier surface 251 . In the schematic depiction of FIG. 8C, the further mark carrier 1250 has an average thickness mark carrier thickness 270, and is arranged at an average mark carrier tilt angle 255 which has been exaggerated for this explanation. The mark carrier tilt angle 255 is an average angular deviation from an axis or plane perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520. In the example depicted in FIG. 8C, the one or more second reference marks 262 on or proximate the second carrier surface 252 are arranged to allow one or more second images 550 to be made by the one or more look-down cameras 520, facing the first carrier surface 251 , through a substantial imaging portion of the further mark carrier 1250. Similarly, the one or more first reference marks 261 on or proximate the first carrier surface 251 are arranged to allow one or more first images 450 to be made by one or more look-up cameras 410, facing the second carrier surface 252, through a substantial imaging portion of the further mark carrier 1250. In FIG. 8C, at least one of the first reference marks 261 and at least one of the second reference marks 262 are both arranged on a mutual axis or plane 265, arranged to be approximately perpendicular to the first carrier surface 251 and / or the second carrier surface 252. The mutual axis or plane 265 is thereby arranged to locate the at least one first reference mark 261 and the at least one second reference mark 262 on the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 if the further mark carrier 1250 is arranged approximately perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520. The further mark carrier 1250 is arranged approximately perpendicular to the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 if the average mark carrier tilt angle 255 is approximately zero. If the average mark carrier tilt angle 255 is approximately zero, a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is also approximately zero. As depicted in FIG. 8C, the average mark carrier tilt angle 255 is significantly greater than zero. In the example depicted in FIG. 8C, an average refractive index of the imaging portions is approximately 2, whereby the look-up camera optical axis or plane 420 is deflected by refraction to a deflected look-up camera axis or plane 425, and whereby the look-down camera optical axis or plane 520 is deflected by refraction to a deflected look-down camera axis or plane 525. In the example depicted in FIG. 8C, a measurement error or offset 290 between the look-up camera optical axis or plane 420 and / or the look-down camera optical axis or plane 520 is approximately zero. In general, one or more optical and / or physical characteristics of the imaging portions of the mark carrier 250 cause a measurement offset or measurement error 290, between an orientation and / or position of the at least one first reference marker 261 relative to the at least one second reference marker 262. In the example depicted in FIG. 8C, the measurement offset 290 is determined to a high degree by an average mark carrier thickness 270 and average mark carrier tilt angle 255. However, according to equation (5) as shown below, the measurement offset 290 is approximately zero because both the one or more first images 450 and the one or more second images 550 are created using radiation which has passed through approximately the same thickness 270 of an imaging portion of the mark carrier 250 with an average refractive index of n=approximately 2 at, in particular, approximately the same mark carrier tilt angle 255. Using n=2 as for example of a Lanthanum dense flint glass, the measurement offset 290 is zero according to equation (5) as shown below.

[0086] It may therefore be advantageous to use one or more imaging portion of a mark carrier 250 or a further mark carrier 1250 with an average refractive index close to 2 to reduce one or more measurement errors or offset 290 caused by significant average mark carrier tilt angles 255.

[0087] For example, if imaging portions of a mark carrier 250 or further mark carrier 1250 are comprised in a glass plate, with an average thickness 270 of 3 mm and an average tilt 255 of I milli-degrees, the average optical axis or plane offset 290, as depicted in FIG. 8B, is expected to scale linearly with different average thicknesses 270 and / or different average tilt angles 255. In general, the largest average tilt angle 255 which may need to be compensated is approximately 2 degrees. The average optical axis or plane offset 290, as depicted in FIG. 8B, also varies depending on an average refractive index (n) of the imaging portions of the mark carrier 250, and can be calculated:

[0088] Fig. 4C depicts a modified version of Fig. 4B, where the average optical axis or plane offsets 290 for the cameras are considered together, and not separately..

[0089] Consideration of this combined measurement offset may be particularly advantageous in applications where a measurement system of the one or more lookup cameras is to be aligned or calibrated with a measurement system of the one or more look-down cameras, for example as depicted in FIG. 7. By providing a degree of alignment or calibration, measurements made with one measurement system may thereby be accurately converted and / or transformed to equivalent measurements in the other measurement system.

[0090] For example, if imaging portions of a mark carrier 250 are comprised in a glass plate, with an average thickness 270 of 3 mm and an average tilt 255 of 1 milli-degrees, the average optical axis or plane offset 290, as depicted in FIG. 8C, is expected to scale linearly with different average thicknesses 270 and / or different average tilt angles 255. In general, the largest average tilt angle 255 which may need to be compensated is approximately 2 degrees. The average optical axis or plane offset 290, as depicted in FIG. 8C, also varies depending on an average refractive index (n) of the imaging portions of the mark carrier 250 or further mark carrier 1250, and can be calculated as follows:

[0091] Surprisingly, in the example depicted in FIG. 8C, the measurement offsets are arranged to at least partially cancel each other out. By using a symmetrical measurement arrangement, wherein the imaging radiation for each camera passes through the one or more imaging regions with a refractive index (n) of close to 2, measurement offsets 290 are cancelled out to a high degree. For example, an average refractive index (n) of the imaging portions of the mark carrier 250 may be approximately 2, or in the range of 1 .0 to 3.0; or 1 .5 to 2.5; or 1 .7 to 2.3; or 1 .75 to 2.25; or 1.8 to 2.2; or 1.85 to 2.15; or 1.9 to 2.1 ; or 1.95 to 2.05.

[0092] In configurations with a refractive index of approximately 2, the measurement offsets 290 are almost completely cancelled out. An average distance between the measured optical center of the one or more first reference marks 261 and the measured optical center of the one or more second reference marks 262 remain approximately the same as an average tilt angle 255 of the mark carrier 250 is varied. This reduction in the average optical axis or plane offset 290 is therefore performed automatically if the optical tool reference 200 is used according to the embodiment depicted in FIG. 7. and is close to zero for a wide ranges of average tilt angles 255 of the mark carrier 250. Additionally, if the key optical and physical characteristics of both imaging portions used are approximately the same, such as approximately the same average thickness 270, automatic compensation is maintained to a high degree. This may be advantageous in making the measurement setup less sensitive to thermal, dynamical, and / or mechanical drift.

[0093] The one or more imaging portions of the mark carrier 250 may be comprised in one or more glass plates. The one or more reference markers 261 , 262 may be formed as one or more structures on the first carrier surface 251 and on the second carrier surface 252. Commonly used glasses may have an average refractive index (n) between 1 .46, for example, for fused silica or Quartz, and approximately 1 .7, for flint glass. However, any suitable glass may be used, for example one or more glasses with an average refractive index (n) of up to approximately 2.2. In particular, having an average refractive index of approximately 2 provides an average optical axis or plane offset 290 error close to zero for a wide ranges of tilt angles. For example, a refractive index of n=2, in particular approximately 2+1- 0,006 or more preferably 2.03 or 2.01 or 2.005, or specifically for example n= 2,02204, may be provided by including a specific Lanthanum dense flint glass, in particular with material properties as follows in the given tables in the one or more imaging portions: If S represents a (geometric) offset of the reference 261 , 262 marks due to a tilt, then:

[0094] S = d * sin(alpha) (1 ) where d is an average thickness 270 of a mark carrier 250 at the one or more imaging portions; and alpha 255 is an average tilt angle of the mark carrier 250 with respect to an optical axis 420, 520 of a camera 410, 510.

[0095] The measurement offset of a look-down camera 510 and a look-up camera 410 is approximately the same due to the symmetry of the measurement arrangement. If K represents a measurement offset of a camera 410, 510 due to refraction of the one or more imaging regions, then:

[0096] K = d * sin(alpha) * (1 - cos(alpha) I sqrt(n2- sin(alpha)2) ) (2) where n is the refractive index of the material and the glass is surrounded by air (n of air is 1).

[0097] If E represents the total error E of the measurement arrangement, then:

[0098] E = S - 2 K (3)

[0099] A Taylor expansion (related to K) then reveals:

[0100] Cos(alpha) / sqrt(n2- sin(alpha)2) = 1 / n + O(alpha2) (4)

[0101] Assuming that n = 2, and ignoring second order terms, the total error E may be approximated to:

[0102] E = S - 2 * d * sin(alpha) * (1 - 1 / 2) = 0 (5) which is close to zero.

[0103] The one or more first reference marks 261 are provided on or proximate the first carrier surface 251 , and the one or more second reference marks 262 are provided on or proximate the second carrier surface 252. In example of FIG. 4A, the reference marks 261 , 262 are provided on a portion of the opposite surfaces 251 , 252 of a glass plate. However, one or more reference marks 261 , 262 may be at least partially embedded or at least partially recessed in a portion of a surface of the mark carrier 250. Optionally, one or more reference marks 261 , 262 may be fully embedded in a portion of a surface of the mark carrier 250. The one or more first reference marks 261 are arranged to allow one or more first images to be made by the one or more look-up cameras 410 through the one or more imaging portions if the one or more look-up cameras 410 are facing the second carrier surface 252 as depicted in FIG. 3B and FIG. 7. The one or more second reference marks 262 are arranged to allow one or more second images to be made through the one or more imaging portions by the one or more look-down cameras 510 if the one or more look-down cameras 510 are facing the first carrier surface 251 as depicted in FIG. 3A and FIG. 7. The imaging regions are therefore at least partially transparent to the radiation used for making the first images and / or the second images. The one or more first images and the one or more second images may be made at different times, at the same time and / or simultaneously. Optionally one or more reference marks 261 , 262 may be arranged to provide at least one orientation and / or position of a mark carrier 250, 1250.

[0104] For example, transparent imaging regions may be provided in a metal layer, such as chrome, which has been deposited onto a surface of a glass platelet. Additionally, the one or more reference marks 261 , 262 may be provided by selective etching or masking of a metal layer, such as chrome, which has been deposited onto a surface of a glass platelet. The material used for the mark carrier 250, 1250, such as a glass, must be sufficiently transparent to the radiation used for the first images and / or the second images. The material used for the mark carrier 250, 1250 is preferably selected to have a low degree of absorption of the radiation imaged. The material used for the mark carrier 250, 1250 is preferably selected to have a low or very low coefficient of thermal expansion.

[0105] The one or more reference marks 261 , 262 may comprise one or more shapes suitable for determining an orientation and / or position. For example, one or more crosses, one or more annular rings, one or more openings, one or more rectangles, one or more squares, one or more corners, one or more edges, one or more lines, one or more circles, one or more ovals, one or more ellipses, or any combination thereof.

[0106] Optionally, the mark carrier 250 may be comprised in a portion of a component 600, and at least a portion of the radiation used to make images comprises an infra-red wavelength, t may be advantageous to arrange the one or more first reference marks 261 and the one or more second reference marks 262 to allow one or more further images to be made by the one or more look-down cameras 510 if the one or more look-down cameras 510 are facing the first carrier surface 251 as depicted in FIG. 3A and FIG. 7. These further images comprising both first reference marks 261 and second reference marks 262 may provide one or more further orientations and / or positions of the one or more look-down cameras 510 relative to the optical tool reference 200.

[0107] Additionally or alternatively, it may be advantageous to arrange the one or more first reference marks 261 and the one or more second reference marks 262 to allow one or more further images to be made by the one or more look-up cameras 410 if the one or more look-down cameras 410 are facing the second carrier surface 252 as depicted in FIG. 3B and FIG. 7. These one or more further images comprising both first reference marks 261 and second reference marks 262 may provide one or more further orientations and / or positions of the one or more look-up cameras 410 relative to the optical tool reference 200.

[0108] In some configurations, using the further images comprising both one or more first reference marks 261 and one or more second reference marks 262 may cause reference marks 261 , 262 at similar positions in the further images to overlap to an unwanted degree resulting on a degree of shadowing of one group of reference marks by another group of reference marks. It may be advantageous to arrange the one or more first reference marks 261 to be separated in the further images by providing an offset in the reference mark pattern with respect to the one or more second reference marks 262.

[0109] FIG. 5A, FIG. 5B and FIG. 5C depict examples of one or more patterns arranged to be recognizable in one or more images. For example, as depicted in FIG. 5A, a plurality of approximately circular first reference markers 261 on or proximate a first carrier surface 251 , arranged in an approximately equidistant matrix of first reference markers 261 . The plurality of first reference markers 261 are arranged in one or more overlapping crosses. As depicted in FIG. 5B, a plurality of approximately circular second reference markers 262 on or proximate a second carrier surface 252, arranged in an approximately equidistant matrix of second reference markers 262. The plurality of second reference markers 262 are arranged in one or more overlapping diagonal crosses. One or more images may be made of one or more first reference markers 261 or one or more second reference markers 262. Additionally or alternatively, one or more images may be made of one or more first reference markers 261 and one or more second reference markers 262 as depicted in FIG. 5C. This may be advantageous because at least one optical and / or physical characteristic, such as a tilt of the mark carrier 250, may be determined by measuring an average distance between one or more first reference markers 261 and one or more adjacent second reference markers 262 Similarly, at least one optical and / or physical characteristic of the mark carrier 250 may be determined at one or more positions across the mark carrier 250.

[0110] In some configurations, it may be advantageous to arrange the one or more first reference marks 261 with the one or more second reference marks 262 to form one or more patterns, wherein the one or more patterns are arranged to be recognizable to a desired degree in one or more of the further images..

[0111] FIG. 6A, FIG. 6B, FIG. 6C depict examples of one or more patterns arranged to be recognizable in one or more images. For example, as depicted in FIG. 6A, a plurality of approximately circular first reference markers 261 and a plurality of approximately ring-shaped (annular) first reference markers 261 on or proximate a first carrier surface 251 . The plurality of first reference markers 261 are arranged in alternating rows and alternating columns of approximately circular / approximately annular first reference markers 261 . As depicted in FIG. 6B, a plurality of approximately annular second reference markers 262 and a plurality of approximately circular second reference markers 262 on or proximate a second carrier surface 252. The plurality of second reference markers 262 are arranged in alternating rows and alternating columns of approximately annular / approximately circular second reference markers 262. One or more images may be made of one or more first reference markers 261 or one or more second reference markers 262. Additionally or alternatively, one or more images may be made of one or more first reference markers 261 and one or more second reference markers 262 as depicted in FIG. 6C, where approximately circular first reference markers 261 are arranged approximately in the center of approximately annular second reference markers 262. Also, approximately circular second reference markers 262 are arranged approximately in the center of approximately annular first reference markers 262. These can also be described as bulls-eye configurations. This may be advantageous because at least one optical and / or physical characteristic, such as a tilt of the mark carrier 250, may be determined by measuring an average distance between one or more first reference markers 261 and one or more central or peripheral second reference markers 262. Similarly, at least one optical and / or physical characteristic of the mark carrier 250 may be determined at one or more positions across the mark carrier 250.

[0112] As depicted in the example of FIG. 3A and FIG. 7, the one or more look-down cameras 510 may optionally comprise one or more illumination radiation source 530, arranged to provide illumination radiation suitable for being directed towards the one or more optical tool references 200, suitable for being received by at least a portion of the first surface 251 of the mark carrier 250, suitable for being transmitted by one or more imaging portions of the mark carrier 250, suitable for being received by at least a portion of the second surface 252 of the mark carrier 250, suitable for being received by one or more second reference marks 262, and suitable for being reflected back towards the one or more look-down cameras 510 by one or more optical feature of the one or more optical tool references 200.

[0113] As depicted in the example of FIG. 3B and FIG. 7, the one or more look-up cameras 410 may optionally comprise one or more illumination radiation source 430, arranged to provide illumination radiation suitable for being directed towards the one or more optical tool references 200, suitable for being received by at least a portion of the second surface 252 of the mark carrier 250, suitable for being transmitted by one or more imaging portions of the mark carrier 250, suitable for being received by at least a portion of the first surface 251 of the mark carrier 250, suitable for being received by one or more first reference marks 261 , and suitable for being reflected back towards the one or more look-up cameras 410 by one or more optical feature of the one or more optical tool references 200.

[0114] As described above, the one or more look-up cameras 410 are arranged to determine a first orientation and / or position of the one or more look-up cameras 410 relative to the one or more first reference marks 261 , which may be further used to determine a first orientation and / or position of the one or more look-up cameras 410 relative to the one or more tool references 200.

[0115] Optionally, the one or more look-up cameras 410 may be further arranged to determine a component orientation and / or position. Optionally, the determination may be performed before attachment to the gripper 160, during attachment to the gripper 160 or after attachment to the gripper 160. To assist with the determination, the one or more components 600 may comprise one or more component marks (or component alignment targets), which are not depicted. Any suitable component mark may be used. For example, a component mark may be a physical feature of at least a portion of a component, an optical characteristic of at least a portion of a component 600, at least a portion of a fiducial, or any combination thereof. The first orientation and / or position may be further used to determine a further orientation and / or position of the component relative to the one or more tool references 200 and / or relative to the one or more first reference marks 261 .

[0116] In the example depicted in FIG. 1 , the one or more look-up cameras 410 are arranged at the component inspection position 810 of the apparatus 100, and the pick and place actuator 150, on its way from the loading position 820 to the attaching position 800, is moved above the one or more look-up cameras 410 and one or more image is made. Optionally, the pick and place actuator 150 is slowed down or stopped to allow the one or more images to be made.

[0117] Additionally, or alternatively, one or more look-up cameras may be attached to the drive member 130. For example, either one or more look-up cameras or a pick and place actuator is attached to the drive member 130 by means of a retractable and extendable swivel mechanism. The one or more look-up cameras or the pick and place actuator, respectively, may then be retracted into an image capture position while moving from the loading position 820 to the attaching position 800, so that one or more images per look-up camera may be made during the move. For the loading of one or more components 600 and for recording images with the one or more lookdown cameras 410 and for placing the one or more components 600, the one or more look-up cameras 410 are preferably extended or rotated into a stand-by position, and the pick and place actuator 150 is similarly extended or rotated into its working position.

[0118] As described above, the one or more look-down cameras 510 are arranged to determine a second orientation and / or position of the one or more look-down cameras 510 relative to the one or more second reference marks 262, which may be further used to determine a second orientation and / or position of the one or more look-down cameras 510 relative to the one or more tool references 200.

[0119] Optionally, the one or more look-down cameras 510 may be further arranged to determine a substrate mark orientation and / or position of a substrate mark in a portion of a substrate on which a component 600 is to be placed and attached. Optionally, the determination may be performed before attaching of a component to a substrate, during attaching of a component to a substrate or after attaching of a component to a substrate. The second orientation and / or position may further be used to determine a further position and / orientation of the one or more substrate marks relative to the one or more tool references 200 and / or relative to the one or more second reference marks 262.

[0120] The apparatus 100 described above in relation to FIG. 1 and FIG. 2, and all the variations and embodiments described herein, are suitable for performing the methods disclosed herein. These methods include a method for aligning one or more components 600 with one or more substrates 300 before attaching, the method comprising: providing a gripper 160 arranged to be disposed at an attaching position 800, the gripper 160 being arranged for releasably attaching to the one or more components 600; providing one or more optical tool references 200 as described herein, arranged to allow an orientation and / or position of one or more cameras relative to one or more other cameras to be determined; providing one or more substrates 300 to the attaching position 800, wherein the one or more substrates 300 comprise one or more substrate marks 340; using one or more look-down cameras 510 to make one or more images of one or more optical tool references 200; determining a first orientation and / or position using the one or more first images of the one or more first reference marks 261 ; using one or more look-up cameras 410 to make one or more images of the one or more optical tool references 200; determining a second orientation and / or position using the one or more second images of the one or more second reference marks 262; determining a camera alignment correction using the first orientation and / or position with the second orientation and / or position; moving the gripper 160 to the attaching position 800; at the attaching position 800 using the one or more look-down cameras 510 to make one or more substrate mark images of the one or more substrate marks 340; determining a substrate mark orientation and / or position using the one or more substrate mark images of the one or more substrate marks 340; determining a substrate mark alignment correction using the substrate mark orientation and / or position.

[0121] Optionally, the method may comprise: determining the first orientation and / or position of the one or more first cameras 410 relative to the one or more first reference marks 261 using the one or more first images; determining the second orientation and / or position of the one or more second cameras 510 relative to the one or more second reference marks 262 using the one or more second images; and determining at least one camera alignment correction using the first orientation and / or position with the second orientation and / or position. The embodiments described above refer to methods for attaching one or more components 600 and one or more substrates 300 using an attaching apparatus 100 to provide an example. The alignment methods and alignment and attaching apparatus described above may be adapted using obvious modifications to provide any further processing methods and respectively any further processing apparatus.

[0122] The pick and place actuator 150 is depicted in FIG. 2 as an assembly, with an approximate cross-sectional extent indicated by a dashed line. Many functions and features are described in this disclosure as being comprised in a pick and place actuator, or attached to a pick and place actuator, or associated with a pick and place actuator, but these should be taken as mere examples. A skilled person may configure and arrange one or more of these functions and features to be only partially comprised in a pick and place actuator, or only partially attached to a pick and place actuator, or only partially associated with a pick and place actuator.

[0123] A skilled person also realises that one or more optical tool references as described herein may be operated in any type of apparatus where two or more measurements systems are to be calibrated or aligned using two or more optical imaging devices arranged to make images of opposite sides of an optical tool reference. List of Reference Numbers

[0124] 100 component attaching apparatus

[0125] 111 first drive system

[0126] 112 second drive system

[0127] 113 gripper rotation drive

[0128] 115 drive guide

[0129] 120 feeder unit

[0130] 130 drive member

[0131] 140 further feed unit

[0132] 150 pick and place actuator

[0133] 160 component gripper

[0134] 200 optical tool reference or tool reference

[0135] 250 mark carrier

[0136] 251 first carrier surface

[0137] 252 second carrier surface

[0138] 255 average mark carrier tilt angle

[0139] 261 first reference mark

[0140] 262 second reference mark

[0141] 265 mutual axis or plane of reference marks

[0142] 270 average mark carrier thickness

[0143] 290 average optical axis or plane offset

[0144] 300 substrate

[0145] 340 substrate mark

[0146] 410 look-up camera or component camera or first camera

[0147] 420 look-up camera optical axis or optical plane

[0148] 425 deflected look-up camera optical axis or optical plane

[0149] 430 illumination radiation source for a look-up camera

[0150] 440 look-up camera field-of-view

[0151] 450 first image to be made by one or more look-up cameras

[0152] 455 further image to be made by one or more look-up cameras

[0153] 510 look-down camera or substrate camera or second camera

[0154] 520 look-down camera optical axis or optical plane

[0155] 525 deflected look-down camera optical axis or optical plane

[0156] 530 illumination radiation source for a look-down camera

[0157] 540 look-down camera field-of-view

[0158] 550 second image to be made by one or more look-down cameras

[0159] 555 further image to be made by one or more look-down cameras

[0160] 600 component

[0161] 800 attaching position

[0162] 810 component inspection position

[0163] 820 loading position

[0164] 910 first axis in Y direction

[0165] 920 second axis in X direction

[0166] 930 third axis in Z direction

[0167] 1250 further mark carrier

Claims

Patentanspriiche1 . Optical tool reference (200) for determining at least one orientation and / or position of one or more first cameras (410) relative to one or more second cameras (510), the optical tool reference (200) comprising:- a mark carrier (250) with a first carrier surface (251 ) and a second carrier surface (252), wherein the second carrier surface (252) is opposite to the first carrier surface (252);- one or more first reference marks (261 ) on or proximate the first carrier surface (251 ), and- one or more second reference marks (262) on or proximate the second carrier surface (252); wherein the mark carrier (250) comprises one or more imaging portions; wherein the one or more first reference marks (261 ) are arranged to allow one or more first images (450) to be made by the one or more first cameras (410) through the one or more imaging portions if the one or more first cameras (410) are facing the second carrier surface (252); wherein the one or more second reference marks (262) are arranged to allow one or more second images (550) to be made through the one or more imaging portions by the one or more second cameras (510) if the one or more second cameras (510) are facing the first carrier surface (251 ); wherein the one or more first images are arranged to provide a first orientation and / or position of the one or more first cameras (410) relative to the one or more first reference marks (261 ); and wherein the one or more second images are arranged to provide a second orientation and / or position of the one or more second cameras (510) relative to the one or more second reference marks (262).

2. Optical tool reference (200) according to claim 1 , wherein an average refractive index (n) of the imaging portions is approximately 2, or in the range of 1 .0 to 3.0; or 1 .5 to 2.5; or 1 .7 to 2.3; or 1 .75 to 2.25; or 1.8 to 2.2; or 1.85 to 2.15; or 1.9 to 2.1 ; or 1.95 to 2.05.

3. Optical tool reference (200) according to any preceding claim, wherein the one or more first reference marks (261 ) are arranged to allow one or more furtherimages (555) to be made by the one or more second cameras (510) if the one or more second cameras (510) are facing the first carrier surface (251 ) to provide a further orientation and / or position of the one or more second cameras (510) relative to the one or more first reference marks (261 ).

4. Optical tool reference (200) according to any preceding claim, wherein the one or more second reference marks (262) are arranged to allow one or more further images (455) to be made by the one or more first cameras (410) if the first camera (410) is facing the second carrier surface (252) to provide a further orientation and / or position of the one or more first cameras (410) relative to the one or more second reference marks (262).

5. Optical tool reference (200) according to any preceding claim, wherein the one or more first reference marks (261 ) and the one or more second reference marks (262) are arranged to allow one or more further images (555) to be made by the one or more second cameras (510) if the one or more second cameras (510) are facing the first carrier surface (251 ) to provide a further orientation and / or position of the one or more second cameras (510) relative to the optical tool reference (200).

6. Optical tool reference (200) according to claim 5, wherein the one or more second reference marks (262) are arranged to form with the one or more first reference marks (261) one or more patterns, wherein the one or more patterns are arranged to be recognizable in the further images (555).

7. Optical tool reference (200) according to claim 5, wherein the one or more second reference marks (262) and the one or more first reference marks (261 ) are arranged to be separated in the further images (555).

8. Optical tool reference (200) according to any preceding claim, wherein the one or more first reference marks (261 ) and the one or more second reference marks (262) are arranged to allow one or more further images (455) to be made by the one or more first cameras (410) if the one or more first cameras (410) are facing the second carrier surface (252) to provide a further orientation and / or position of the one or more first cameras (410) relative to the optical tool reference (200).

9. Optical tool reference (200) according to claim 8, wherein the one or more first reference marks (261 ) are arranged to form with the one or more second reference marks (262) one or more patterns, wherein the one or more patterns are arranged to be recognisable in the further images (455).

10. Optical tool reference (200) according to claim 8, wherein the one or more first reference marks (261 ) and the one or more second reference marks (262) are arranged to be separated in the further images (455).11 . Optical tool reference (200) according to any preceding claim, wherein the optical tool reference (200) comprises two or more first reference marks (261 ), wherein the two or more first reference marks (261 ) being arranged to be substantially different in the one or more first images; and the one or more first images being arranged to provide a reference mark orientation and / or a reference mark position.

12. Optical tool reference (200) according to any preceding claim, wherein the optical tool reference (200) comprises two or more second reference marks (262), wherein the two or more second reference marks (262) being arranged to be substantially different in the one or more second images; and the one or more second images being arranged to provide a reference mark orientation and / or a reference mark position.

13. Optical tool reference (200) according to any preceding claim, wherein the optical tool reference (200) comprises one or more code marks, arranged to allow one or more code images to be made by a camera of the one or more code marks, wherein the one or more code images are arranged to provide one or more parameters of the one or more code marks selected from the group comprising: an orientation, a position, a parameter, a value, a number, or any combination thereof.

14. Optical tool reference (200) according to any preceding claim, wherein the one or more imaging portions comprise a material selected from the group comprising: a glass, a Lanthanum dense flint glass, a crystal, a plastic, a semiconductor, silicon, a liquid, a metal, or any combination thereof.

15. Optical tool reference (200) according to any preceding claim, wherein the mark carrier (250) is comprised in a portion of a component (600), a substrate (300), a wafer, a mask, a lens, a mirror, a filter, a diffractive optic, a phase plate, a diffuser, a micro-lens array, a waveplate, a zone plate, a plate, a thin plate, a plane parallel plate, a beam divider, a beam combiner, a beam splitter, an image sensor, a prism, a cube, a right-angle prism, a grating, a retroreflector, a quarter-wave plate, a half-wave plate, a tool fiducial, a gripper fiducial, a substrate fiducial, a component fiducial, a grating, a scale, a dichroic filter, a polarizing filter, or any combination thereof.

16. Apparatus (100) for aligning one or more components (600) with one or more substrates (300) before attaching, the apparatus (100) comprising: o a pick and place actuator (150) arranged to be disposed at an attaching position (800), the pick and place actuator (150) comprising a gripper (160) for releasably attaching to the one or more components (600);- the apparatus (100) comprising: o a feeding unit (140) for providing one or more substrates (300) to the attaching position (800), wherein the one or more substrates (300) comprise one or more substrate marks (340); o one or more optical tool references (200) according to any one of the claims 1 to 15, arranged to allow a orientation and / or position of one or more cameras relative to one or more other cameras to be determined; o one or more first cameras (410), arranged as one or more look-up cameras for making the one or more first images of the one or more first reference marks (261 ); and o one or more second cameras (510), arranged as one or more lookdown cameras for making the one or more second images of the one or more second reference marks (262).

17. Apparatus according to claim 16, wherein the apparatus (100) is arranged to determine a first orientation and / or position of the one or more first cameras (410) relative to the one or more first reference marks (261 ) using the one or more first images, to determine a second orientation and / or position of the one or more second cameras (510) relative to the one or more second reference marks (262) using the one or more second images and to determine at leastone camera alignment correction using the first orientation and / or position with the second orientation and / or position.

18. Method for aligning one or more components (600) with one or more substrates (300) before attaching, the method comprising the steps of- providing a gripper (160) arranged to be disposed at an attaching position (800), the gripper (160) being arranged for releasably attaching to the one or more components (600);- providing one or more optical tool references (200) according to any one of claims 1 to 15, arranged to allow an orientation and / or position of one or more cameras relative to one or more other cameras to be determined;- providing one or more substrates (300) to the attaching position (800), wherein the one or more substrates (300) comprise one or more substrate marks (340);- using one or more look-down cameras (510) to make one or more images of one or more optical tool references (200);- determining a first orientation and / or position using the one or more first images of the one or more first reference marks (261 );- using one or more look-up cameras (410) to make one or more images of the one or more optical tool references (200);- determining a second orientation and / or position using the one or more second images of the one or more second reference marks (262);- determining a camera alignment correction using the first orientation and / or position with the second orientation and / or position;- moving the gripper (160) to the attaching position (800);- at the attaching position (800) using the one or more look-down cameras (510) to make one or more substrate mark images of the one or more substrate marks (340);- determining a substrate mark orientation and / or position using the one or more substrate mark images of the one or more substrate marks (340);- determining a substrate mark alignment correction using the substrate mark orientation and / or position.

19. Method according to claim 18, wherein the method comprises further the steps of- determining the first orientation and / or position of the one or more first cameras (410) relative to the one or more first reference marks (261 ) using the one or more first images;- determining the second orientation and / or position of the one or more second cameras (510) relative to the one or more second reference marks (262) using the one or more second images; and- determining at least one camera alignment correction using the first orientation and / or position with the second orientation and / or position.

Images