NL2010062B1

NL2010062B1 - Optical device, positioning method, and positioning apparatus.

Info

Publication number: NL2010062B1
Application number: NL2010062A
Authority: NL
Inventors: Yu Xiang; Rao Xuejun; Rao Changhui
Original assignee: Inst Of Optics And Electronics Chinese Academy Of Sciences
Priority date: 2012-06-12
Filing date: 2012-12-27
Publication date: 2018-02-16
Also published as: CN102736140A; NL2010062A; CN102736140B

Abstract

An optical device, a positioning method, and a positioning apparatus are disclosed. In one embodiment, the optical device may comprise a substrate; a lighttransmitting hole provided on the substrate; at least one pointing mark provided on the substrate, and having at least one characteristic which is different between a portion thereof relatively close to the light-transmitting hole and a portion thereof relatively far away from the light-transmitting hole.

Description

OPTICAL DEVICE, POSITIONING METHOD, AND POSITIONING APPARATUS

TECHNICAL FIELD

[0001] The present disclosure relates to the optics field, and particularly, to an optical device, a positioning method, and a positioning apparatus.

BACKGROUND

[0002] A variety of applications, such as optical systems and optical measurements, need optical devices which can diffract light, such as a plate with a micro-hole. For example, measurement of wavefront aberrations of an objective lens system with a relatively large numerical aperture at a high precision desires a Shack-Hartmann sensor with an improved precision. An optimal way to calibrate the Shack-Hartmann sensor in its precision is to adopt an absolute spherical wave. This necessitates generation of a series of spherical wavefronts at a high precision. Such spherical wavefronts can be used as references to measure various errors and physical parameters of the Shack-Hartmann sensor. Effects of those errors on the precision of the Shack-Hartmann sensor should be eliminated. Theoretically, the spherical reference wavefronts can be generated by pinhole diffraction. The smaller is the diameter of the pinhole, the less are errors in the generated spherical wavefronts, resulting in an improved optical quality. Therefore, if the pinhole diffraction is adopted to generate the spherical reference wavefronts, the pinhole generally has a size comparative to the wavelength.

[0003] To properly perform calibration and detection in the Shack-Hartmann system, it is necessary for the pinhole to be installed in the system in such a manner that an incident light beam can be aligned with the pinhole in the order of sub-micron. This requires the pinhole in the order of sub-micron to be positioned at a significantly high precision. However, in such a system, it is impossible to adopt an imaging monitor method because of spatial limitations of the pinhole in the order of sub-micron.

SUMMARY

[0004] The present disclosure aims to provide, among others, an optical device, a positioning method, and a positioning apparatus, by which it is possible to properly position the optical device in an efficient way.

[0005] According to as aspect of the present disclosure, there is provided an optical device, comprising: a substrate; a light-transmitting hole provided on the substrate; at least one pointing mark provided on the substrate, and having at least one characteristic which is different between a portion thereof relatively close to the light-transmitting hole and a portion thereof relatively far away from the light-transmitting hole.

[0006] According to a further aspect of the present disclosure, there is provided a method for positioning a light beam relative to an optical device, comprising: scanning the optical device with the light beam to determine a region where a pointing mark is provided on the optical device; detecting at least one characteristic of the pointing mark in different portions of the pointing mark; determining a tracking direction based on a variation of the at least one characteristic in the different portions; positioning the light beam relative to the optical device to an end of the pointing mark in the tracking direction; and moving the light beam from the end of the pointing mark by a predetermined distance in the tracking direction.

[0007] According to a still further aspect of the present disclosure, there is provided a positioning apparatus, comprising a supporter configured to support a light emitting device configured to emit a light beam, an optical device, and a detector. The detector may be configured to detect the light beam via the optical device. The apparatus may further comprise a moving mechanism configured to be movable and thus enable relative movement between the light emitting device and the optical device. Further, the apparent may comprise a controller configured to control the moving mechanism to move the light beam relative to the optical device so as to: scan the optical device with the light beam to determine a region where a pointing mark is provided on the optical device based on a variation of a light intensity detected by the detector; detect at least one characteristic of the pointing mark in different portions of the pointing mark based on the variation of the light intensity detected by the detector; determine a tracking direction based on a variation of the at least one characteristic in the different portions; position the light beam relative to the optical device to an end of the pointing mark in the tracking direction; and move the light beam from the end of the pointing mark by a predetermined distance in the tracking direction.

[0008] According to embodiments of the present disclosure, it is possible to position the optical device (such as, a plate with a micro-hole in the order of sub-micron) to a proper location in a system utilizing this optical device in an efficient way (especially, without monitoring).

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and other objects, features, and advantages of the present disclosure will become apparent from following descriptions of embodiments with reference to the attached drawings, in which: [0010] Figs. 1(a) and 1(b) are a plan view schematically showing an optical device according to an embodiment of the present disclosure and an enlarged view schematically showing a portion of the optical device, respectively; [0011] Fig. 2 is a plan view schematically showing an optical device according to a further embodiment of the present disclosure; [0012] Fig. 3 is a flow chart schematically showing a method of positioning an optical device in a plane (the x-y plane) perpendicular to an optical axis according to an embodiment of the present disclosure; [0013] Figs. 4(a) and 4(b) are schematic views showing determination of a tracking direction based on a pointing mark and tracking to a micro-hole according to an example; [0014] Fig. 5 is a schematic view showing determination of a tacking direction based on a pointing mark according to a further example; [0015] Fig. 6 is a plan view schematically showing an optical device according to a further embodiment of the present disclosure; [0016] Figs. 7(a) and 7(b) are schematic views showing determination of a tracking direction in the optical device shown in Fig. 6; [0017] Fig. 8 is a plan view schematically showing an optical device according to a further embodiment of the present disclosure; [0018] Fig. 9 is a plan view schematically showing an optical device according to a further embodiment of the present disclosure; [0019] Fig. 10 is a flow chart schematically showing a method of 3-dimensionally positioning an optical device according to an embodiment of the present disclosure; [0020] Figs. 11(a) and 11(b) are schematic views showing coarse positioning in a direction (the z-direction) of an optical axis based on a knife-edge method according to an example; [0021] Figs. 12(a) and 12(b) are schematic views showing fine positioning in a direction (the z-direction) of an optical axis based on a light intensity according to an example; and [0022] Fig. 13 is a schematic view showing a configuration of a positioning apparatus according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to attached drawings. However, it is to be understood that these descriptions are illustrative and not intended to limit the present disclosure. Further, in the following, known structures and technologies are not described to avoid obscuring the present disclosure unnecessarily.

[0024] In the drawings, various structures according to the embodiments are schematically shown. However, they are not drawn to scale, and some features may be enlarged while some features may be omitted for sake of clarity. Moreover, shapes and relative sizes and positions of features or regions shown in the drawings are also illustrative, and deviations may occur due to manufacture tolerances and technique limitations in practice. Those skilled in the art can also devise features/regions of other different shapes, sizes, and relative positions as desired.

[0025] To properly position an optical device, such as a plate with a micro-hole (which is usually designed to be light-transmitting, and thus can be called as a “light-transmitting hole” if so), a “directional” pointing mark can be provided on the optical device according to some embodiments of the present disclosure. Here, so-called “directional” means that the pointing mark may have a characteristic or an optical property varying in a certain direction. Especially, the characteristic or optical property can vary in a direction directed to the micro-hole. That is, the pointing mark may have at least one characteristic or optical property which is different between a portion thereof relatively close to the micro-hole and a portion thereof relatively far away from the micro-hole. Such variation may be monotonie, for example. An orientation of the pointing mark and thus a tracking direction directed to the micro-hole can be determined based on the varying characteristic or optical property.

[0026] According to an embodiment, such a pointing mark may be optically detectable due to, for example, its optical property/properties different from that/those of component(s) (for example, a substrate of the optical device) around it. Therefore, the positioning mark can be identified based on different optical responses of the substrate and the pointing mark to an incident light beam (due to their different optical properties). For example, the substrate can be provided as blocking light, while the pointing mark can be provided as transmitting light. In this case, the incident light beam can be applied to one side of the optical device, and a corresponding optical response (for example, an intensity of transmitted light) can be detected on an opposite side and then used to identify the pointing mark. According to a further embodiment, the pointing mark can have a different reflectivity from that of the substrate, so that it can be identified based on an intensity of reflected light (and thus an intensity of transmitted light, because a sum of the intensity of the reflected light and the intensity of the transmitted light remains substantially constant and is approximately equal to an intensity of the incident light, without considering light absorption).

[0027] The varying characteristic of the pointing mark may comprise its width, for example. In this case, the orientation of the pointing mark can be determined based on different widths of the pointing mark in its different portions, which can be determined by scanning. For example, the optical device can be scanned by the incident light beam in a scanning direction. Edges of the pointing mark can be determined based on the optical responses (such as intensities of transmitted light as described above) of the pointing mark and the substrate to the incident beam. As a result, a width of the pointing mark in the scanning direction is derived. Further, a further width of the pointing mark in the same scanning direction at a further position can be derived by a further scan. In this way, the orientation of the pointing mark can be determined based on differences in the widths at those two positions.

[0028] According to an example, the pointing mark may have its width decreasing in the direction directed to the micro-hole. In this case, if a width at a position is greater than a further width at a further position, then a direction from the position to the further position can be determined as the orientation of the pointing mark, vice versa.

[0029] The pointing mark needs not to be continuous, and can be discrete. For example, the pointing mark may have several segments separated from each other. In this case, the tracking direction can be determined in a segment, and then a further segment next to this one can be arrived at by tracking in the tracking direction, and so on, until arriving at an end of the pointing mark.

[0030] According to an embodiment, it is possible to provide one or more pointing marks on the substrate. In a case where a plurality of pointing marks are provided, ends of the respective pointing marks can be placed at a substantially same distance from the micro-hole (specifically, its geometrical center or center of gravity). As a result, if the tracking is conducted along whatever one of the pointing marks to the end of this pointing mark, the micro-hole (specifically, its geometrical center or center of gravity) can be reached by further advancing by the same distance in the tracking direction. In this case, the plurality of pointing marks (specifically, their ends) are placed on a circle around the micro-hole. In addition, the plurality of pointing marks can be substantially evenly distributed around the circle. Thus, it is possible to find by scanning one of the pointing marks quickly irrespective of an initial position on the optical device from which the scanning is performed.

[0031] According to an embodiment, the pointing mark may comprise a portion for coarse tracking and a portion for fine positioning. The portion of the pointing mark for coarse tracking may be continuous with the portion of the pointing mark for fine positioning. The varying characteristic of the pointing mark may vary more gently in the portion for coarse tracking than in the portion for fine positioning. The portion of the pointing mark for fine positioning may be closer to the micro-hole than the portion of the pointing mark for coarse tracking. In this way, positioning can be performed at a relatively low precision (i.e., at a relatively low distance resolution) for the portion of the pointing mark for coarse tracking, but at a relatively high precision (i.e., at a relatively high distance resolution) for the portion of the pointing mark for fine tracking. As a result, on one hand it is possible to track quickly through the portion of the pointing mark for coarse tracking at the relatively low precision to the proximity to the micro-hole, and on the other hand it is possible to position the optical device (or, the micro-hole) at a high precision by tracking in the portion of the pointing mark for fine positioning at the relatively high precision.

[0032] According to an embodiment, in addition to the pointing mark for determining the tracking direction, there may be further a positioning mark provided on the optical device, for more precisely positioning the light beam relative to the optical device in tracking. For example, the positioning mark is provided to be associated with the pointing mark. Specifically, each pointing mark may have a positioning mark associated therewith. The positioning mark may have (at least) two edges parallel to a direction and provided on opposite sides of a straight line passing through the micro-hole (specifically, it geometrical center or center of gravity) in the direction. Thus, it is possible to position the light beam onto the straight line passing through the micro-hole (specifically, its geometrical center or center of gravity) based on positions of the two edges of the positioning mark in tracking.

[0033] In this case, scanning and tracking can be carried out as follows. Specifically, the optical device may be scanned by the incident light beam in a scanning direction, and respective edges of the pointing and positioning marks can be determined based on their transmissions of the light beam. As a result, respective widths of the pointing and positioning marks in the scanning direction can be derived. Further, further widths of the pointing and positioning marks in the same scanning direction can be derived by scanning at a further position.

[0034] In this way, the orientation of the pointing mark can be determined based on the difference in the widths of the pointing mark at those two positions. For example, if the pointing mark has its width at one position greater than that at a further position, then a direction from the one position to the further position can be determined as the orientation of the pointing mark, vice versa.

[0035] On the other hand, positioning of the light beam can be determined based on the positioning mark. For example, if the two edges of the positioning mark are at the same distances from the straight line passing through the micro-hole, the light beam can be positioned midway between the two edges (i.e., a center of the width of the positioning mark).

[0036] Fig. 1(a) is a plan view showing an example optical device. As shown in Fig. 1(a), the optical device 100 comprises a substrate 102 and a hole 104 provided on the substrate 102. The substrate 102 may comprise any suitable material, such as resin. In this example, the substrate 102 is formed to be opaque (by, for example, coating an opaque film on a transparent resin base), and the hole 104 is formed to be a light-transmitting hole (by, for example, opening the hole in the opaque film). It is apparent that the substrate 102 and the hole 104 can be provided in other forms. The hole 104 has a very small size, for example, in the order of a wavelength of light adopted in the optical device (such as sub-micron or even shorter), and thus is called as “micro-hole.” Generally, such a micro-hole can be hardly recognized by a CCD camera or human eyes. Therefore, it is a challenging task to properly position the optical device in assembling the optical device into a system using this device (by, for example, aligning the micro-hole with an optical axis of the system).

[0037] In the example of Fig. 1(a), the optical device 100 is shown as having a square shape. However, it is to be noted that the present disclosure is not limited thereto. For example, the optical device may have other shapes such as rectangle and circle.

Further, in Fig. 1 the micro-hole 104 is shown as having a circle shape, but it can have various shapes suitable for manufacturing, including regular shapes such as ellipse, square, rectangle, and triangle, or irregular shapes.

[0038] Pointing marks 106 are provided on the substrate 102. The pointing marks 106 may comprise light-transmitting areas provided on the substrate 102 (by, for example, opening the areas in the opaque film). Thus, the pointing marks 106 and the substrate 102 have different transmittances (in this example, the substrate 102 blocks light, while the pointing marks 106 transmit light). As a result, it is possible to optically measure (or, identify) the pointing marks 106 relative to the substrate 102.

[0039] In the example shown in Fig. 1, the pointing marks 106 each have a width monotonically decreasing in a direction directed to the micro-hole 104, and thus are “directional.” Further, in the example shown in Fig. 1, the width decreases linearly in the direction directed to the micro-hole 104. However, the present disclosure is not limited thereto. For example, the width may decrease in a curve of second or higher order, an exponential curve, and the like.

[0040] The pointing marks 106 each may be divided into a portion 1061 for coarse tracking and a portion 1062 for fine positioning based on variation of the width. In the example shown in Fig. 1, the width varies more gently in the portion 1061 for coarse tracking than in the portion 1062 for fine positioning. In an example application, the respective portions 1062 for fine positioning may begin from 2pm distant from the microhole (specifically, its geometrical center or center of gravity), and thus are located within a Φ4μηι circle centered at the micro-hole (specifically, its geometrical center or center of gravity), as shown by the dot-and-dash line in Fig. 1. Further, in the example shown in Fig. 1, the portions 1062 for fine positioning each have a dot-like end. Such a dot-like end facilitates more precisely determining a distance from the end to the micro-hole (specifically, its geometrical center or center of gravity).

[0041] In the example shown in Fig. 1, the pointing mark is divided into two portions with different trends in variation (i.e., the portion 1061 for coarse tracking which varies relatively gently in width and the portion 1062 for fine positioning which varies relatively rapidly in width). However, the present disclosure is not limited thereto. For example, the pointing mark may comprise a single portion with a uniform trend in variation, or more portions with different trends in variation.

[0042] It is to be noted that the present disclosure is not limited to a variation in width. For example, the pointing mark may have a “directional” transmittance. Specifically, the transmittance of the pointing mark may vary, for example, monotonically increases or monotonically decreases, in the direction directed to the micro-hole.

[0043] In the example of Fig. 1, four pointing marks 106 in a symmetrical arrangement are shown. However, it is possible to provide any other suitable number of pointing marks on the optical device, for example, more or less than four, or even only one. Further, in a case where a plurality of pointing marks are provided, the present disclosure is not limited to the symmetrical arrangement, which, though, is preferred. It is also feasible that the plurality of pointing marks are arranged asymmetrically. Furthermore, in the example of Fig. 1, the four pointing marks are shown in the same shape, which, however, is not necessary.

[0044] The end (for example, the dot-like end) of the pointing mark 106 is at a certain distance from the micro-hole 104 (specifically, its geometrical center or center of gravity). This distance can be determined in manufacturing the optical device to be, for example, 500nm. In the case where there are several pointing marks 106, each of the pointing marks 106 may have its end at a substantially same distance from the micro-hole 104.

[0045] Fig. 1(b) is an enlarged view showing a portion taken from the optical device shown in Fig. 1(a). As shown in Fig. 1(b), the portion 100' of the optical device comprises the micro-hole 104 and the pointing marks arranged around the micro-hole 104. The pointing marks each may comprise the portion 1061 for coarse tracking and the portion 1062 for fine positioning which is continuous with the portion 1061. It is to be noted that the portion 1062 for fine positioning is not necessarily continuous with the portion 1061 for coarse tracking. Instead, there may be a gap between the two portions. The portion for fine positioning and the micro-hole may have relatively high positional and formal precision, for example, in the order of nanometer, which can be ensured by manufacturing apparatuses and processes. The portion for coarse tracking may have relatively low positional and formal precision, for example, in the order of micron.

[0046] In the example of Fig. 1, the pointing mark 106 is shown in a continuous arrangement. However, the present disclosure is not limited thereto. The pointing mark 106 can be provided in a discrete arrangement. For example, it may include several segments separated from each other. Fig. 2 shows an example optical device 200 in such an arrangement. The optical device 200 comprises a substrate 202 and a micro-hole 204 provided on the substrate 202. Further, pointing marks 206 are provided around the micro-hole 204. Each of the pointing marks 206 includes segments 2061 and 2062 separated from each other.

[0047] Fig. 3 is a flow chart showing a method for positioning an optical device according to an embodiment of the present disclosure.

[0048] As shown in Fig. 3, at block 302, scanning is performed with an incident light beam on the optical device, to identify a pointing mark provided thereon. For example, the incident light beam may be emitted from a light emitting device in a system utilizing the optical device, and preferably is a converging beam. The light beam may have its optical axis aligned with a systemic optical axis. Further, the scanning can be conducted by moving the optical device. For example, the optical device can be moved by a translation device which can effect two-dimensional translation in a plane (the x-y plane) perpendicular to the optical axis (the z-direction).

[0049] Prior to the scanning, an initial scanning point can be set (now shown in the flow chart of Fig. 3). For example, the optical device can be (manually) adjusted in its orientation on the x-y plane, so that a straight ling passing through an end of the pointing mark and the micro-hole (specifically, its geometrical center or center of gravity) is substantially parallel to a translation axis of the translation device, for example, the x-axis, which can be used later as a tracking direction. Specifically, the straight line and the translation axis (e.g., the x-axis) may have an included angle within a certain range, for example, smaller than 2°. Further, the initial scanning point can be set near the pointing mark, so that it is possible to quickly find the pointing mark by the scanning.

[0050] Here, the substrate and the pointing mark may have different optical responses to the incident light beam due to their different optical properties. Thus, a region where the pointing mark is located can be determined based on the optical responses. For example, in the optical device as shown in Fig. 1, the region where the pointing mark is located can be determined based on intensities of light transmitted through the substrate and the pointing mark. The light intensities can be detected by a detector provided on an opposite side of the optical device to the incident light beam. The detector may comprise an array of CCD sensors. (In an example application of a Shack-Hartmann system, the system itself comprises an array of CCD sensors provided opposite to a light emitting device.) For example, it can be determined that the incident light beam reaches the pointing mark if the intensity of the transmitted light becomes greater than a threshold.

[0051] Reference may be made to Fig. 4(a), which shows a portion of the optical device shown in Fig. 1 or 2. Assume that the initial scanning point is located on an opaque area of the substrate, and that the incident light beam scans downwards in a track 408 along the other translation axis (for example, the y-axis, normal to the x-axis) of the translation device (in the example shown in Fig. 4(a), the scanning direction 402 is parallel to the y-axis). When the light scans to point A located on an edge of the pointing mark, the intensity of the transmitted light detected by the detector increases. Here, a position where the intensity of the transmitted light becomes above a threshold (“a first threshold”) is recorded as A (xa, ya). The intensity of the transmitted light above the threshold indicates that the pointing mark is detected.

[0052] It is apparent that the initial scanning point is not necessarily located on the opaque area of the substrate. If the initial scanning point is located on the area of the pointing mark, then the pointing mark can be identified immediately (based on the intensity of the transmitted light) without any more scanning. Further, the scanning is performed not necessarily downwards (in the -y-direction), but can be performed upwards (in the +y-direction) instead.

[0053] Returning back to Fig. 3, after the pointing mark is identified, at block 304, at least one characteristic of the pointing mark can be detected in different portions thereof to determine a tracking direction. For example, variation of the at least one characteristic in the different portions of the pointing mark can be derived by scanning, and the tracking direction can be determined based on the variation. In a case where the varying characteristic is a width and the width decreases towards the micro-hole, a direction in which the width decreases can be determined as the tracking direction.

[0054] Reference may be made again to Fig. 4(a). First, a width (“a first width”) at the track 408 is derived. Specifically, after the position of A is determined as described above, the light continues to scan downwards (in the -y-direction) along the scanning direction 402. When the light scans to point B located on a further edge of the pointing mark, the intensity of the transmitted light detected by the detector decreases. Here, a position where the intensity of the transmitted light becomes below a threshold (“a second threshold”) is recorded as B (xb, yb). Here, the first threshold and the second threshold can be the same or different, and can be set experimentally. In this way, the first width at the track 408 can be calculated as a distance |AB| between A and B based on A (xa, ya) and B (Xb, Yb).

[0055] Then, the incident light beam is moved relative to the optical device, so that the incident light beam is moved by a certain distance along the tracking direction (the x-direction in Fig. 4) to a further track 410. A width (“a second width”) of the pointing mark at the track 410 can be derived by scanning (in the same scanning direction, i.e., in the y-direction). The scanning can be conducted as described above. For example, points A' and B' on the edges of the pointing mark can be determined (based on the intensity of the transmitted light) by scanning in +/-y direction, and the second width at the track 410 can be calculated as a distance |A'B'| between A' and B' based on A' (xa\ ya') and B' (xb\ yb').

[0056] When the width |AB| at the track 408 and the width |A'B'| at the track 410 are derived, the tracking direction can be determined based on the variation in the width. For example, in a case where the pointing mark has its width decreasing in the direction directed to the micro-hole, then the tracking direction can be determined as a direction from the track 408 to the track 410 (i.e., the +x-direction) if |AB| > |A'B'|. Or otherwise, the tracking direction can be determined as a direction from the track 410 to the track 408 (i.e., the -x-direction) if |AB| < |A'B'|.

[0057] When moving from the track 408 to the track 410, it is preferable to move from a special position at the track 408 along the tracking direction 404. Here, so called “special position” may refer to a position where the scanning track intersects a straight line which passes through the end of the pointing mark and coincides with the direction directed to the micro-hole. The special position can be determined based on, at least partially, the configuration of the pointing mark (especially, the configuration of the varying characteristic), and the arrangement of the pointing mark relative to the micro-hole.

[0058] For example, in the example shown in Fig. 4(a), the pointing mark has its longitudinal axis consistent with the direction directed to the micro-hole, and is symmetrical with respect to the longitudinal axis. In this case, the special position at each scanning track can determined as a midpoint of the width at this track. Specifically, the midpoint C (xc, yc) of the first width may be determined as xc = (xb-xa)/2, yc = (yb-ya)/2; and the midpoint C' (Xc', yc') of the second width may be determined as xc' = (xb'-xa')/2, yc' = (yb'-ya')/2.

[0059] It is to be noted that the special position is not limited to the midpoint of the width. For example, in the example shown in Fig. 5, the pointing mark has its longitudinal axis consistent with the direction directed to the micro-hole, and the width at the scanning track has a portion above the longitudinal axis and a portion below the longitudinal axis at a ratio of 2:1. In this case, the special position at each scanning track can be determined as a position at 2/3 or 1/3 of the width at this scanning track, which depends on whether the scanning is conducted from above the pointing mark or from below the pointing mark (depending on the initial scanning point).

[0060] Returning back to Fig. 3, at block 306, tracking is performed with the incident beam in the tracking direction determined at block 304 until the end of the pointing mark. The tracking can be conducted in the manner as described above in conjunction with Fig. 4. For example, the light beam advances from one track to a further track in the tracking direction. Each time when the light beam moves from the one track to the further track, it is possible that it moves from a midpoint of the one track to (substantially a midpoint of) the further track in the tracking direction. When the light advances to the end of the pointing mark, the intensity of the transmitted light decreases. Here, a position where the intensity of the transmitted light decreases below a threshold can be recorded as the end of the pointing mark.

[0061] Reference may be made to Fig. 4(b), which shows a portion of the optical

device shown in Fig. 1 or 2. As described above, in the tracking process, edge points A and B on the track 408 and thus a midpoint C therebetween may be determined by scanning in the scanning direction 402, and then the light beam moves from the midpoint C to a further track (not shown) in the tracking direction. Such a process is repeated. When the light beam reaches the end T, the intensity of the transmitted light decreases. A position where the intensity of the transmitted light decreases below a threshold can be recorded as the end T(xt, yt).

[0062] Returning back to Fig. 3, when the light beam tracks to the end of the pointing mark, at block 308, relative movement of the incident light beam and the optical device continues so that the incident light beam moves further from the end T(xt, yt) by a predetermined distance D in the tracking direction to arrive at the micro-hole (specifically, its geometrical center or center of gravity O). This distance D is determined in manufacture of the optical device. Optionally, further scanning can be performed from the point O within a half radius of the micro-hole in a radial direction (for example, upwards, downwards, leftwards, or rightwards), to achieve better positioning (for example, to position the light beam where the intensity of the transmitted light is maximal).

[0063] Thus, the optical device is positioned so that the incident light beam can pass through the micro-hole.

[0064] In the case where the pointing mark includes the portion for coarse tracking and the portion for fine positioning as shown in Fig. 1, it is possible for the light beam to scan and track through the portion of the pointing mark for coarse tracking by a translation device with a relatively low precision (or a relatively low translation resolution), while scan and track through the portion of the pointing mark for fine positioning by a translation device with a relatively high precision (or a relatively high translation resolution), and finally arrive at the micro-hole.

[0065] In the above positioning method, it is necessary to adjust the tracking direction to be substantially parallel to the straight line passing through the end of the pointing mark and the micro-hole (specifically, its geometrical center or center of gravity), so that the tracking direction and the straight line has an included angle within a certain range, for example, smaller than 2°. That is, the tracking direction is substantially determined (for example, in the x-direction), and the pointing mark is used to determine whether the tracking should conducted from one end to the other end (for example, in the +x-direction) or from the other end to the one end (for example, in the -x-direction) along the tracking direction.

[0066] To achieve positioning without monitoring, further positioning mark(s) may be provided. Fig. 6 is a plan view showing an example optical device with both pointing marks and positioning marks. As shown in Fig. 6, the optical device 600 comprises a substrate 602, and a hole 604 and pointing marks 606 provided on the substrate 602. Reference may be made to the above descriptions in conjunction with Fig. 1 for details of the substrate 602, the hole 604, and the pointing marks 606.

[0067] On the substrate 602, there are positioning marks 608 each associated with each of the pointing marks 606. The positioning marks 608 may have a different optical property (for example, transmittance) from that of the pointing marks 606, and thus is optically recognizable with respect to the pointing marks 606. Each of the positioning marks 608 has two parallel edges 6081 and 6082. The edges 6081 and 6082 may be provided so that they are parallel to a direction and are located on opposite sides of a straight line passing through the micro-hole (especially, its geometrical center or center of gravity) in the direction (which straight line coincides with the dash-and-dot line in the example shown in Fig. 6(a)). Preferably, the straight line also passes through an end (especially, a dot-like end) of the pointing mark 606.

[0068] This optical device 600 can be positioned also by the method shown in Fig. 3. Hereinafter, descriptions will be given to differences in positioning the optical device 600.

[0069] Specifically, at block 302, scanning is performed with an incident light beam on the optical device, to identify a pointing mark provided thereon. In this case, there is no need to adjust the optical device in its orientation on the x-y plane in advance. That is, the optical device can be placed on the x-y plane in any orientation.

[0070] After the pointing mark is identified, at block 304, at least one characteristic of the pointing mark can be detected in different portions thereof to determine a tracking direction. In the process, a positioning mark associated with the pointing mark is further identified, to position the light beam. Here, descriptions are given with respect to an example where the varying characteristic is a width and the width decreases towards the micro-hole.

[0071] Reference may be made to Fig. 7(a), which shows a portion of the optical device 600 as shown in Fig. 6, and also shows a situation when the scanning of the optical device 600 is just started. Because the orientation of the optical device on the x-y plane is not adjusted in advance as stated above, a scanning direction 702 may cross the pointing mark and the positioning mark at an arbitrary angle. Assume that the incident light beam scans downwards along a track 708 in the scanning direction 702, and points A1 and B1 on edges of the pointing mark and points A2 and B2 on edges of the positioning mark are identified based on an intensity of transmitted light. Thus, a first width of the pointing mark at the track 708 can be determined as a distance |A1 B11 between A1 and B1, and a first width of the positioning mark at the track 708 can be determined as a distance |A2B2| between A2 and B2.

[0072] Then, the incident light beam is moved relative to the optical device, so that the incident light beam is moved by a certain distance along a direction 704 crossing the scanning direction to a further track 710. Further scanning ban be conducted along the track 710 (with the scanning direction 702 unchanged). For example, points AT and BT on the edges of the pointing mark and points A2' and B2' on the edges of the positioning mark can be identified (based on the intensity of the transmitted light) by the scanning. Thus, a second width of the pointing mark at the track 710 can be determined as a distance |A1'B1'| between AT and BT, and a second width of the positioning mark at the track 710 can be determined as a distance |A2'B2'| between A2' and B2'.

[0073] When the width |A1B1| of the pointing mark at the track 708 and the width |A1'BT| thereof at the track 710 are derived, the tracking direction can be determined based on a variation in the width. For example, the tracking direction can be determined as a direction from the track 708 to the track 710 if |A1B1| > |A1'B1'|. Or otherwise, the tracking direction can be determined as a direction from the track 710 to the track 708 if |A1B1| < |A1'BT|.

[0074] On the other hand, the light beam can be positioned based on the positioning mark in the tracking process. Specifically, when moving from the track 708 to the track 710, it is preferable to move from a special position at the track 708 along the tracking direction 704. Here, so called “special position” may refer to a position where the scanning track intersects the above described straight line (which is parallel to the edges of the positioning mark and passes through the micro-hole (especially, its geometrical center of center of gravity)). For example, if the edges of the positioning mark are equally distant from the straight line, the special position can be a midpoint of the width of the positioning mark.

[0075] Further, the tracking direction can be adjusted based on the positioning mark. Specifically, as shown in Fig. 7(b), the tracking direction can be adjusted to be a direction 704' from a midpoint C of the width |A2B2| to a midpoint C' of the width |A2'B2'| (or a reverse direction, which depends on the magnitude of the width |A1 B11 and the width |A1'BT|). Then, the scanning direction can be adjusted to 702' perpendicular to the tracking direction 704'. In this case, when the light beam advances from the track 708 to the track 710, the advancing direction is substantially directed to the micro-hole (specifically, its geometrical center or center of gravity). During the tracking process, the tracking direction can be corrected continuously based on the special position (for example, the midpoint of the width) of the positioning mark on each track.

[0076] Fig. 8 is a plan view showing a further example optical device with both pointing marks and positioning marks. As shown in Fig. 8, the optical device 800 comprises a substrate 802, and a hole 804 and pointing marks 806 provided on the substrate 802. Reference may be made to the above descriptions in conjunction with Fig. 1 for details of the substrate 802, the hole 804, and the pointing marks 806. On the substrate 802, there are positioning marks 808 each associated with each of the pointing marks 806. The example shown in Fig. 8 differs from that shown in Fig. 6 in that each of the positioning marks 808 is provided outside its associated pointing mark 806.

[0077] Fig. 9 is a plan view showing a still further example optical device with both pointing marks and positioning marks. As shown in Fig. 9, the optical device 900 comprises a substrate 902, and a hole 904 and pointing marks 906 provided on the substrate 902. Reference may be made to the above descriptions in conjunction with Fig. 1 for details of the substrate 902, the hole 904, and the pointing marks 906. On the substrate 902, there are positioning marks 908 each associated with each of the pointing marks 906. The example shown in Fig. 9 differs from that shown in Fig. 6 or 8 in that each of the positioning marks 908 is separated from its associated pointing mark 906.

[0078] It is to be understood by those skilled in the art that relative positioning between the pointing marks and the positioning marks can be provided in any suitable configurations, but not limited to those described above. Further, in the above examples, the positioning mark is provided symmetrically with respect to the longitudinal axis of its associated pointing mark. However, the present disclosure is not limited thereto. For example, the positioning mark may have its longitudinal axis offset from that of its associated pointing mark.

[0079] According to the method described above with reference to Fig. 3, it is possible to position the optical device properly on the plane (the x-y plane) perpendicular to the optical axis (the z-axis). According to a further embodiment, it is possible to further incorporate a process for z-direction positioning, so as to achieve 3-dimensional positioning in the x-y-z system. Preferably, the optical device is positioned onto a focal plane of the incident light beam in the z-direction, so that the converging light beam can substantially entirely pass through the micro-hole.

[0080] Fig. 10 is a flow chart showing a 3-dimensional positioning method according to an example of the present disclosure.

[0081] As shown in Fig. 10, at block 1002, coarse positioning in the z-direction can be conducted. The coarse positioning in the z-direction can be carried out based on a knife-edge method. In the following, the principle of the knife-edge method will be described with reference to Figs. 11(a) and 11(b).

[0082] As shown in Fig. 11(a), an incident light beam emitted from a light source passes through an optical unit 1102 to form a converging beam, which converges into a light spot on a focal plane. A detector 1106 (for example, an array of CMOS sensors) is provided opposite to the light source, to detect the incident light beam. The incident light beam impinges on the detector 1106 and thus creates a light receiving region 1106-1 on the detector 1106. If a light blocking object 1104 is placed in the light path, then a portion of the incident light beams is blocked, resulting in a shading region 1106-2 on the detector 1106. If the light blocking object 1104 is placed closer to the light source relative to the focal plane, movement of the light blocking object 1104 in a direction (in the x-y plane) perpendicular to the optical axis (the z-direction) will cause the shading region 1106-2 move in a reverse direction.

[0083] On the other hand, as shown in Fig. 11(b), if the light blocking object 1104 is placed further from the light source relative to the focal plane, movement of the light blocking object 1104 in a direction (in the x-y plane) perpendicular to the optical axis (the z-direction) will cause the shading region 1106-2' opposite to the light receiving region 1106-1' move in the same direction.

[0084] In this way, it is possible to determine whether the light blocking object is closer to or further from the light source relative to the focal plane based on the knife-edge method. Then, based on the determination, the light blocking object can be moved accordingly so that it substantially coincides with the focal plane at a precision, for example, up to micron.

[0085] In carrying out coarse positioning in the z-direction based on the knife-edge method, an edge of a pointing mark can be used as a “knife edge.” Specifically, scanning can be performed in a direction (for example, in the x- or y-direction) in the x-y plane, to find the edge of the pointing mark. Then, positioning can be performed with this edge based on the knife-edge method. For example, the incident light beam is transmitted though the pointing mark on one side of the edge to form a light receiving region on the detector, and on the other hand, is blocked by the substrate on the other hand of the edge to cause a light shading region on the detector. The optical device can be moved, and the relative position (closer to the light source or further from the light source) of the optical device to the focal plane can be determined based on the movement direction of the shading region.

[0086] Returning back to Fig. 10, after the coarse positioning in the z-direction, x-y positioning can be performed. The x-y positioning can be conducted as described above with reference to Fig. 3. Specifically, at block 1004, x-y coarse tracking can be performed, where the light beam tracks to a position in proximity to the micro-hole by means of the portion of the pointing mark for coarse tracking (at a precision of, for example, micron). At block 1006, x-y fine positioning can be performed, where the light beam is positioned to the micro-hole by means of the portion of the pointing mark for fine positioning (at a precision of, for example, nanometer).

[0087] Next, at block 1008, fine positioning in the z-direction can be performed. According to an example, the fine positioning in the z-direction can be carried out based on the intensity of the transmitted light. In principle, the intensity of the transmitted light reaches its peak when the optical device coincides completely with the focal plane (in which state the incident light beam entirely passes through the micro-hole due to the x-y positioning).

[0088] Specifically, reference may be made to Fig. 12(a), which shows the focal plane O, a plane A closer to the light source relative to the focal plane O, and a plane B further from the light source relative to the focal plane O. The intensity of the light transmitted through the micro-hole has different distributions when the optical device is located on the plane O, the plane A, and the plane B, respectively. Fig. 12(b) shows those distributions of the intensity of the transmitted light. Specifically, as shown in Fig. 12(b), a distribution profile 1202 of the intensity of the transmitted light has a narrowest width and thus its energy most concentrated when the optical device is located on the focal plane O; a distribution profile 1204 has a wider width when the optical device is located on the plane A; and a distribution profile 1206 has a widest width when the optical device is located on the plane B. Therefore, it is possible to determine whether the optical device (substantially) coincides with the focal plane O or not at a precision, for example, up to nanometer.

[0089] Returning back to Fig. 10, after the fine positioning in the z-direction, the method can return to block 1006, for further adjustment of the x-y fine positioning (by, for example, moving the optical device so that the incident beam moves within a half radius of the micro-hole in a radial direction to search for a position where the intensity of the transmitted light reaches its peak), to make the incident beam and the optical device (or, the micro-hole) be coaxial with each other more precisely.

[0090] Although in the example shown in Fig. 10 the coarse positioning in the z-direction is performed prior to the x-y positioning and the fine positioning in the z-direction is performed posterior to the x-y positioning, the present disclosure is not limited thereto.

The positioning in the z-direction (including the coarse positioning and the fine positioning) can be performed independent of the x-y positioning.

[0091] Fig. 13 shows a positioning apparatus according to an example of the present disclosure. As shown in Fig. 13, the positioning apparatus may comprise a supporter 1308. A light emitting device 1302, an optical device 1304, and a detector 1306 may be installed and thus supported by the supporter 1308. The light emitting device 1302 may comprise a light source 1302-1 configured to emit light. Further, the light emitting device 1302 may comprise an optical unit 1302-3 configured to convert the light emitted from the light source 1302-1 into a converging beam. For example, the light source 1302-1 may comprise a laser as a point light source, and emit light which is converted by the optical unit 1302-3 (including, for example, a collimation lens and a converging lens) into a converging beam. The optical device 1304 may comprise any of the above described optical devices, and comprises a light-transmitting hole 1304-2. The detector 1306 is configured to detect an intensity of the light emitted by the light emitting device and then transmitted through the optical device 1304, and may comprise an array of CCD sensors. On the right side of Fig. 13, a schematic plane view of the detector 1306 is shown.

[0092] The positioning apparatus 1300 comprises at least one moving mechanism 1310 configured to move at least one of the light emitting device 1302 and the optical device 1304 (and also the detector 1306) to achieve relative movement between the light emitting device 1302 and the optical device 1304. The moving mechanism may comprise a 3-dimensional translation stage which can effect translation in the x-, y-, and z-directions.

[0093] The positioning apparatus 1300 further comprises a controller 1312. The controller 1312 may be electrically connected to the moving mechanism 1310 to control the movement of the moving mechanism. Further, the controller 1312 can be further electrically connected to the detector 1306 to receive outputs from the detector 1306.

[0094] The controller 1312 may comprise a microprocessor or a microcontroller, or a computing device such as a computer. The controller 1312 may be programmed to implement any of the positioning methods described herein, such as one shown in Fig. 3 or Fig. 10.

[0095] Specifically, the controller 1312 may be configured to control the moving mechanism 1310 to move the light beam emitted from the light emitting device 1302 relative to the optical device 1304, so as to scan the optical device 1304 with the light beam to find a pointing mark provided on the optical device 1304 based on a variation in the light intensity detected by the detector 1306 (for example, based on a determination that the light intensity increases above a threshold). Further, the controller may be configured to further control the relative movement between the light emitting device 1302 and the optical device 1304 to detect at least one characteristic of the pointing mark in different portions of the pointing mark based on the variation in the light intensity detected by the detector 1306. For example, edges and thus a width of the pointing mark at the respective portions thereof can be determined based on the variation in the light intensity detected by the detector 1306. Then, the controller 1312 may determine a tracking direction based on a variation of the at least one characteristic (for example, the width) in the different portions. Based on the tracking direction, the light beam can advance to the light-transmitting hole 1304-2.

[0096] Further, when the optical device further has positioning mark(s) provided thereon, the controller 1312 may be configured to control the moving mechanism 1310 so as to further identify a positioning mark associated with the pointing mark when detecting the at least one characteristic. Then, in determining the tracking direction, the light beam can be positioned based on positions (of edges of) the positioning mark.

[0097] From the foregoing, it will be appreciated that specific embodiments of the disclosure have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. In addition, many of the elements of one embodiment may be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the technology is not limited except as by the appended claims.

Claims

An optical device comprising: a substrate; a light-transmitting aperture provided on the substrate; at least one pointer marker provided on the substrate with at least one characteristic that differs between a portion thereof relatively close to the light-transmitting aperture and a portion thereof relatively far away from the light-transmitting aperture, wherein the characteristic comprises a width of the pointer marker and varies monotonously in a direction to the illuminating opening.

The optical device of claim 1, wherein the pointer marker comprises a light-transmitting region.

The optical device of claim 1, wherein the width decreases in the direction towards the light-transmitting aperture.

The optical device of claim 1, wherein the pointer marker comprises different segments separated from each other.

The optical device of claim 1, wherein there is a plurality of indicator marks provided on the substrate, wherein the respective ends of the plurality of indicator marks are at a substantially equal distance from the light-transmitting aperture.

The optical device of claim 1, further comprising: at least one positioning marker associated with the at least one pointer marker, each with two edges parallel to one direction, wherein the two edges are provided on opposite sides of a straight line which are in the through the illuminating opening.

The optical device of claim 6, wherein the pointing marker and the positioning marker have different light transmittance factors with respect to each other.

A method for positioning a light beam relative to an optical device, comprising: scanning the optical device with the light beam to determine an area where a pointer mark is provided on the optical device; detecting at least one property of the indicating marker in different parts of the indicating marker, wherein the characteristic comprises a width of the indicating marker and varies monotonously in a direction towards the light-transmitting aperture; determining a tracking direction based on a variation of the at least one property in the different parts; positioning the light beam with respect to the optical device at an end of the indicating marker in the tracking direction; and moving the light beam from the end of the pointer marker over a predetermined distance in the tracking direction.

The method of claim 8, wherein detecting the at least one property of the pointer marker in the various parts of the pointer marker further comprises identifying a positioning marker associated with the pointer marker, wherein the positioning marker has provided two direction-parallel edges to opposite sides of a straight line running in the direction through a light-transmitting aperture, and determining the tracking direction further comprises positioning the light beam based on positions of the two edges of the positioning marker.

The method of claim 9, wherein the pointing marker and the positioning marker comprise light-transmitting regions with different light-transmitting factors relative to each other, and determining the area where the pointing marker is includes determining the area and also identifying the positioning marker based on a intensity of the light beam transmitted through the optical device.

The method of claim 10, wherein detecting the property in the different parts of the pointing marker comprises: positioning the light beam relative to the optical device on a first part of the pointing marker and determining first widths of the pointing and positioning marks along a first direction in the first part; moving the light beam relative to the optical device in a second direction which intersects the first direction to a second part of the pointer marker; and determining the second widths of the pointing and positioning marks along the first direction in the second part.

The method of claim 11, wherein if the first width of the pointer marker is greater than the second width of the pointer marker, a direction from a special position of the first width of the positioning marker to a special position of the second width of the positioning marker as the following direction is determined; or otherwise if the first width of the pointer marker is smaller than the second width of the pointer marker, a direction from a special position of the second width of the positioning marker to a special position of the first width of the positioning marker when the tracking direction is determined.

The method of claim 12, wherein the special position is a center of the width.

The method of claim 8, further comprising: adjusting a relative distance between a light-emitting device that emits the light beam and the optical device along an optical axis for locating the optical device on a focal plane of the light beam.

The method of claim 14, wherein the adjustment along the optical axis comprises: a first adjustment prior to detecting the feature; and a second adjustment after moving the light beam from the end of the pointer marker over the predetermined distance in the tracking direction.

The method of claim 15, wherein the first adjustment is performed based on a separation edge method and wherein the second adjustment is performed based on the intensity of the light beam transmitted through the optical device.

A positioning device, comprising: a support member adapted to support a light-emitting device adapted to emit a light beam, an optical device, and a detector, wherein the detector is adapted to detect the light beam via the optical device; a displacement mechanism adapted to be displaceable and thus allowing relative displacement between the light-emitting device and the optical device; and a control device adapted to control the moving mechanism for moving the light beam relative to the optical device for scanning the optical device with the light beam for determining an area in which an indication marker is provided on the optical device based on a variation of a light intensity detected by the detector; detecting at least one property of the indicating marker in different parts of the indicating marker based on the variation of the light intensity detected by the detector, wherein the characteristic comprises a width of the indicating marker and varies monotonously in a direction towards the light-transmitting aperture; determining a tracking direction based on a variation of the at least one property in the different parts; positioning the light beam relative to the optical device to an end of the pointer marker in the tracking direction; and moving the light beam from the end of the pointer marker over a predetermined distance in the tracking direction.

18. Positioning device according to claim 17, wherein the control device is further adapted to control the displacement mechanism for: further identifying a positioning mark associated with the pointer marker when detecting the at least one property of the pointer marker in the different parts of the pointer marker wherein the positioning marker has two unidirectional edges on opposite sides of a straight line passing through a light-transmitting aperture in the direction; positioning the light beam based on positions of the two edges of the positioning marker when determining the tracking direction.