Edge profile detection

A system includes a light source, a detector, and a processor. The light source is configured to emit light onto a target. The detector is configured to receive light interaction between the emitted light and the target. The processor is configured to receive the light interaction between the emitted light and the target and further configured to process the light interaction to determine an edge profile associated with the target.

SUMMARY

Provided herein is a system including a light source, a detector, and a processor. The light source is configured to emit light onto a target. The detector is configured to receive light interaction between the emitted light and the target. The processor is configured to receive the light interaction between the emitted light and the target and further configured to process the light interaction to determine an edge profile associated with the target. These and other features and advantages will be apparent from a reading of the following detailed description.

DESCRIPTION

Before various embodiments are described in greater detail, it should be understood that the embodiments are not limiting, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein.

It should also be understood that the terminology used herein is for the purpose of describing the certain concepts, and the terminology is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood in the art to which the embodiments pertain.

Prevalence of technology such as smartphones, hard drives, etc., has increased the need to cut material such as glass with stringent form factor requirements. For example, glass may be cut based on stringent form factors to provide touch screen capabilities for smartphones. Similarly, newer hard drive technology may use glass as a substrate, and such glass cut with stringent form factors.

With respect to the hard drive industry, deployment of Heat Assisted Magnetic Recording (HAMR) technology includes a substrate material change to glass consistent with thermal transfer properties of the HAMR writing process. In addition, the more mature Perpendicular Media Recording (PMR) based magnetic storage can benefit using glass given the modulus and the density being very similar to aluminum used in most of the cloud storage products currently. By adopting glass media, a thinner substrate can be used, therefore allowing the disk packing density to be increased resulting in a larger capacity drive.

Although for certain smartphone applications, re-cutting a sheet of glass to the round disk shape used in today's hard drives would suffice. Unfortunately though, the touchscreen technology for smartphones as well as the hard drive technology are moving toward form factors and requirements, e.g., the principal surface, dimension metrics, roughness, etc., that are difficult to meet using mechanical cutting. New techniques can be used to address the stringent form factors with respect to dimensions, roughness, etc. For example, a U.S. patent application Ser. No. 15/702,619, filed on Sep. 12, 2017, entitled “Laser Beam Cutting/Shaping A Glass Substrate”, a U.S. patent application Ser. No. 15/729,042, filed on Oct. 10, 2017, entitled “Shaping A Glass Substrate After Cutting”, and a U.S. patent application Ser. No. 15/792,279, filed on Oct. 24, 2017, entitled “Edge Polishing A Glass Substrate After Cutting” discuss various methods to cut and shape the glass, and are incorporated herein by reference in their entirety.

Accordingly, a desire has now arisen to detect the edge profile of the glass after it is cut in order to determine whether it meets the required dimensions, roughness, etc. Embodiments described herein leverage a new contrast based metrology to accurately determine edge symmetry, dimensional deviations and vibration signatures. It is appreciated that although the embodiments described in the subsequent figures are described with respect to determining edge symmetry, dimensional deviations and vibration signatures of disks in hard drive, the system may be used for non-hard drive applications as well, e.g., touchscreen, etc. As such, any discussion of the embodiments with respect to hard drive disks is for illustration purposes and should not be construed as limiting the scope of the embodiments.

In some embodiments, a system includes a light source, a detector, and a processor. The light source is configured to emit light onto a target. The detector is configured to receive light interaction between the emitted light and the target. The processor is configured to receive the light interaction between the emitted light and the target and further configured to process the light interaction to determine an edge profile associated with the target.

Referring now toFIGS. 1A-1H, an exemplary edge profile detection system and simulation results therefrom according to one aspect of the present embodiments is shown. Referring specifically toFIG. 1A, a system for detecting edge profile of a glass according to one aspect of the embodiments is shown. The system includes a light source110, a spindle140, a detector130, and a processor150. It is appreciated that the spindle140may be configured to mount a target120, e.g., a disk, glass, etc. thereon and rotate.

In some embodiments, the light source110is configured to emit light onto the target120being held and/or rotated by the spindle140. Emitted light from the light source110interacts with the target120. Light from the light source110and/or light interaction with the target120is received by the detector130. The detector130provides data associated with the received light, e.g., light from the light source110and/or light interaction with the target120, to the processor150for processing. The processor150processes the received data and determines the necessary edge fidelity and resolution that corresponds to the edge profile geometries of the target120.

More specifically, the light source110is configured to emit light to the periphery, e.g., edges, outer diameter, etc. of the target120. The light source110may be a laser source, a collimated light source, a light emitting diode (LED) source, a monochromatic light source, achromatic light source, etc. In some embodiments, the light source110emits light that is coherent light. However, it is appreciated that non-coherent light may be used and an error correction circuitry may be used to compensate for errors associated with use of non-coherent light. In some embodiments, the light emitted from the light source110may have a narrow illumination angle. The light emitted from the light source110interacts with the target120, e.g., light interacts with the edges of the target120. The light interaction may include light reflection, light refraction, light diffraction, etc. resulting from interaction with the target120. In some embodiments, the light emitted from the light source110may interact with the edges of the target120and as a result changes optical characteristic of the light, e.g., wavelength may be change, polarization may be changed, etc. It is appreciated that some of the light emitted from the light source110may not interact directly with the edges or inner part of the target120.

The target120is mounted on the spindle140and the spindle140rotates. In some embodiments, the spindle rotates at a constant speed and as it rotates the detector130captures the light received from the target120. In some embodiments, the target120is mounted on the spindle140such that target120is positioned parallel to optical axis of the light emitted from the light source110. In other words, the target120may be positioned and held by the spindle140such that the light emitted from the light source110is tangential to the edges of the target120in order to provide an edge on view of the tangential portion of the target120thickness. It is, however, appreciated that in some embodiments, a different configuration may be used.

The light emitted from the light source110whether interacting with the target120directly or not is received by the detector130. In some embodiments, the detector130receives the light from the light source110and/or from the light interacting with the target120. The target120may cast a shadow on the detector130. The detector130may capture light contrast between the casted shadow to a portion that does not include the shadow. As such, the data captured by the detector130once processed by the processor150provides the necessary edge fidelity and resolution corresponding to the edge profile geometries. It is appreciated that in some embodiments, the detector130may include a CMOS, a Charge-Coupled Device (CCD) camera, etc. In other words as light, e.g., collimated light, is illuminated to the target120, e.g., disk edge, a mask or shadow is formed on the detector130, e.g., CCD camera, CMOS, etc. The image possesses useful characteristic of high contrast from the target120, e.g., disk edge, masking or blocking a portion of the light, e.g., collimated light.

The processor150, e.g., a computer, Application Specific Integrated Circuit (ASIC), Field Programmable Gate Array (FPGA), a central processing unit (CPU), etc., receives the captured data by the detector130. In some embodiments, the processor150may utilize image processing to determine an edge profile associated with the target. For example, the processor150may determine edge symmetry, dimensional deviations and vibration signatures associated with the edge profile of the target120. In some embodiments, the processor150is configured to use light gradient to determine the edge profile associated with the target120. Light gradient may be a vector of steepest ascent or descent of light contrast. Light gradient may be defined as

The light gradient due to mask/contrast imaging provides the necessary edge fidelity and resolution for tracking edge profile geometries. Enhancement of edge resolution below the diffraction limit of light is achieved by light scattering and diffraction of light at the edge. In some embodiments, the edge profile may be derived by computing a 2D derivative, also known as the gradient. In this embodiment, a convolutional kernel may be employed that combines the gradient calculation with filtering.

It is appreciated that the methodology described above may be performed for each captured image. In some embodiments, one image is captured for a small rotation angle until the target120, e.g., disk, sample completes a full revolution. Sample resolution may be controlled by the number of images taken per 360 degrees of rotation. In some embodiments, 5000 or so images provide circumferential accuracy exceeding 1 milli-Radian (mR). It is appreciated that additional resolution can be achieved by increasing the number of images captured per revolution. For example, 20000 images provides circumferential resolutions better than 250 uR or 12 um for a 47 mm radius disk. Given the number of captured images, the processing may be performed in near real-time.

Referring now toFIG. 1B, an exemplary image captured by detector130is shown. The captured image illustrates the shadow cast by the target120. Referring now toFIG. 1C, an edge profile152as determined by the processor150is shown. It is appreciated that the arrows illustrate the light gradient from the inner diameter of the target120toward its periphery and outer diameter. Referring now toFIG. 1D, a determination of the light profile154, by the processor150, from inner diameter of the target120to the outer diameter of the target120is shown. Furthermore, derivative light profile156, as determined by the processor150, is shown. The derivative light profile156illustrates the derivate light profile from the inner diameter of the target120to the outer diameter of the target120. It is noteworthy that the ringing, as illustrated, may be due to edge interferences of the light, e.g., collimated light, etc.

Referring now toFIG. 1E, analysis for each captured image is shown. It is appreciated that the sharpest increase/decrease158in contrast may correspond to the edge boundary of the target120. Each image is processed to determine the point corresponding to the edge boundary of the target120. Once every captured image is processed for the full revolution of the target120, the points may be connected to form the edge profile associated with the target120.

Referring now toFIGS. 1F-1H, a different illustration of the light gradient (light contrast) is shown. It is appreciated that line159, for each of theFIGS. 1F-1H, corresponds to light contrast going from the inner diameter of the target120, e.g., disk, toward its outer diameter. A top down view reveals geometric anomalies from the intended edge profile.

Referring now toFIG. 2, another exemplary edge profile detection system according to one aspect of the present embodiments is shown.FIG. 2is substantially similar to that ofFIG. 1A. In this embodiment, a telecentric lens210is coupled to the light source110and a telecentric lens220is coupled to the detector130. It is appreciated that although two telecentric lenses are used, in some embodiments only one telecentric lens may be used. For example, in some embodiments, the telecentric lens210may be used without using the telecentric lens220and vice versa. It is appreciated that the telecentric lens210may be used to enhance light collimation and to further improve light source uniformity. It is further appreciated that the telecentric lens220may be used to enhance accuracy and improve angle of detection.

Referring now toFIGS. 3A-3B, an interference pattern for determining edge profile using monochromatic light source according to one aspect of the present embodiments is shown. The interference pattern shown is based on the system as described inFIG. 1Awhere a monochromatic light source110is used. It is appreciated that in some embodiments, the monochromatic light source (expanded laser beam) enhances interference patterns that are observed, as shown inFIG. 3A. Referring now toFIG. 3B, the light intensity on the y-axis is shown. The light intensity for points on the target120are shown on the x-axis moving from the inner diameter of the target120toward its outer diameter120and beyond.

Referring now toFIG. 4, an exemplary edge profile for a disk using gradient derivative processing according to one aspect of the present embodiments is shown. The average and/or median410for the light contrast for each captured point is illustrated. As illustrated, symmetry and/or curvature anomalies may be identified, as shown by the average and/or median410for the light contrast for the target120. The average and/or median410may represent the edge profile of the target120. Furthermore, the thickness420for the edge profile of the target120may be rendered. For example, the thickness420may represent the surface of the target120. The wall430profile of the target120may also be rendered and may be calculated using the average and/or median410. It is appreciated that other metrics of interest for the edge profile symmetry may similarly be calculated and rendered.

Referring now toFIG. 5, a 3-D rendition of the edge profile according to one aspect of the present embodiments is shown. It is appreciated that the captured images with the appropriate edge trajectory determined by the methods described above may be used to form a continuous 3D edge profile. It is appreciated that the illustrated perspective view provides height and deformation information associated with the target120edge profile. The 3-D image may be rendered on a display device (not shown). Thus, edge features and defects associated with the target120may be inspected and analyzed.

Referring now toFIG. 6, a flow diagram for detecting edge profile according to an alternate aspect of the present embodiments is shown. At step610, the target, e.g., target120, is mounted on a spindle, e.g., spindle140. It is appreciated that the target may be mounted on the spindle parallel to optical axis of the emitted collimated and coherent light. At step620, collimated and coherent light may be emitted from a light source, e.g., light source110, onto the target. At step630, the target may be rotated, e.g., using the spindle140. It is appreciated that the spindle may rotate the target at a constant speed.

At step640, the light emitted from the light source interacts with the target, e.g., edges of the target as described inFIGS. 1A-5, and it is received, e.g., by a detector130. The light interaction may include light reflection, light diffraction, light refraction from the target, or any combination thereof. The light interaction is the result of the collimated and coherent light being emitted onto the target as the target is being rotated by the spindle. Light interaction includes a shadow resulting from the collimated and coherent light being emitted onto the target. At step650, data associated with the light interaction and the shadow is processed and used to determine an edge profile associated with the target. For example, a light gradient may be applied in order to determine the edge profile of the target. It is appreciated that the edge profile may include edge symmetry, dimensional deviations, thickness, and vibration signatures associated with the edge profile of the target. In some embodiments, the processed information associated with the edge profile may be rendered on a display. For example, a 3-dimensional profile of the edge profile may be rendered on a display.

While the embodiments have been described and/or illustrated by means of particular examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear to persons having ordinary skill in the art to which the embodiments pertain, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the concepts described herein. The implementations described above and other implementations are within the scope of the following claims.