WO2018111644A1 - Imaging method for low contrast features - Google Patents

Abstract

A microscope system includes a light source, a spatial light modulator, a lens and a beam splitter aligned along an illumination axis, and a camera and objective aligned along an imaging axis. The beam splitter is also aligned along the imaging axis. The spatial light modulator is configured to spatially modulate light emitted by the light source to produce an arrangement of light and dark areas.

Description

IMAGING METHOD FOR LOW CONTRAST FEATURES

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/435,671, filed December 16, 2016, which is incorporated by reference in its entirety.

BACKGROUND

L Discussion of the Related Art

There is a need to place identification marks on transparent components (e.g., formed of glass, sapphire, a polymer such as polycarbonate, etc.) during the manufacturing process to track single pieces and lots through production processes for quality assurance purposes. Tracking units through the process allows manufacturers to identify specific production steps that introduce quality non-conformance defects and make corrections. The challenge in applying an identification mark on or in a transparent component (e.g., a transparent window) is that, after production, it should not be noticeable by an end-user of the product (e.g., who might have purchased a phone or watch with such an identification mark). One means to accomplish this is to make such an identification mark quite small. Exemplary identification marks can include QR codes (e.g., with a 200 x 200 micron size, composed of dots two microns in size), a bar code (e.g., composed of parallel lines of adjoining or overlapping dots), or the like or any combination thereof. The dots of an identification mark can be created by laser disturbance of the glass material, and can be made so small and of such low contrast, that a human observer is, at least, highly unlikely to notice them.

In some cases, it is customary to coat one surface of the transparent component with a lightly-colored (e.g., white) paint. However, especially when there is a white paint coating on one side of the transparent component, the identification mark can become essentially invisible to a light microscope. Embodiments discussed in greater detail below provide a method and system for creating high contrast images of such identification marks.

SUMMARY

Another embodiment of the present invention can be characterized as a method of detecting a mark embedded within a region of a transparent component. The transparent component can be characterized as having a first surface and a second surface opposite the first surface and a light-colored coating formed on the second surface below the embedded mark. The method can include acts of projecting a pattern of light and dark regions through the region of the transparent component and onto the coating and capturing an image of the embedded mark and the projected pattern.

Another embodiment of the present invention can be characterized as a microscope system that includes a light source, a spatial light modulator, a lens and a beam splitter aligned along an illumination axis, and a camera and objective aligned along an imaging axis. The beam splitter is also aligned along the imaging axis. The spatial light modulator is configured to spatially modulate light emitted by the light source to produce an arrangement of light and dark areas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate identification marks embedded within a transparent component, according to one embodiment, in different positions relative to a projected field stop pattern.

FIG. 3 illustrates one embodiment of a system for detecting identification marks, such as the identification marks shown in FIGS. 1 and 2.

FIG. 4 illustrates one embodiment of reticle used in projecting a field stop pattern.

DETAILED DESCRIPTION

Example embodiments are described herein with reference to the accompanying drawings. Unless otherwise expressly stated, in the drawings the sizes, positions, etc., of components, features, elements, etc., as well as any distances therebetween, are not necessarily to scale, but are exaggerated for clarity. In the drawings, like numbers refer to like elements throughout. Thus, the same or similar numbers may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, even elements that are not denoted by reference numbers may be described with reference to other drawings.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be recognized that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range, as well as any sub-ranges therebetween. Unless indicated otherwise, terms such as "first," "second," etc., are only used to distinguish one element from another. For example, one node could be termed a "first node" and similarly, another node could be termed a "second node", or vice versa.

Unless indicated otherwise, the term "about," "thereabout," etc., means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. Spatially relative terms, such as "below," "beneath," "lower," "above," and "upper," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature, as illustrated in the FIGS. It should be recognized that the spatially relative terms are intended to encompass different orientations in addition to the orientation depicted in the FIGS. For example, if an object in the FIGS, is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. An object may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

According to one embodiment discussed herein, a low contrast identification mark that is embedded within a transparent component (e.g., formed of a material such as glass, sapphire, polymeric material such as polycarbonate, etc.) is detected by placing a patterned reticle of alternating light and dark areas at a field stop of a light microscope (see, e.g., FIGS. 3 and 4). Within the light microscope, the patterned reticle creates a high contrast view of embedded identification mark in transparent components with a brightly painted underside. When the light passing through the field stop of a microscope uniformly illuminates the painted bottom side of such a glass, the light diffuses in all directions and "washes-out" the code. By placing the patterned reticle at or near the field stop and selectively illuminating the object with bright and dark areas, some light reflects off the painted surface and illuminates components (e.g., dots) of the embedded identification mark (e.g., provided as a QR code, a bar code, etc.), yet the background of the painted area under such dots remains dark, thus generating contrast. In the bright areas, the identification code is also visible as the surrounding areas are dark and the dots tend not to be "washed-out" as light is only reflecting back from directly under them, not from a wide variety of angles. For example, in FIG. 1, dark line of a field stop pattern, projected by a light microscope incorporating a patterned reticle as described above, is slightly out of focus below an identification mark embedded within a transparent component (e.g., a clear glass window) that has an underside coated with white paint, which brings contrast to the pattern. Referring to FIG. 1, the identification mark 100 is composed of a plurality of dots 100a. The identification mark 100 is about 200 x 200 microns in size, and the dots 100a have a maximum size of about 2 microns. As shown in FIG. 2, the identification mark 100 is visible against the projected field stop pattern even in the corner of the field of view of the light microscope.

FIG. 3 is a view schematically illustrating an embodiment of a light microscope (also referred to herein as a system for detecting identification marks, or an identification mark detection system) configured to project the field stop pattern discussed above. Referring to FIG. 3, the identification mark detection system 300 may include an objective 302 (e.g., a brightfield microscope objective), a beam splitter 304, a lens tube 306 (e.g., including a relay lens), a camera 308 (e.g., a digital camera), a first set of lenses 310 (note: the first set of lenses 310 may consist of a single lens, or multiple lenses), a field stop 312, the patterned reticle (herein illustrated at 314), a second set of lenses 316 (note: the second set of lenses 316 may consist of a single lens, or multiple lenses), an aperture stop 318, a focusing lens 320, and a light source 322.

As exemplarily illustrated in FIG. 3, the first set of lenses 310, the field stop 312, the patterned reticle 314, the second set of lenses 316, the aperture stop 318, the focusing lens 320, and the light source 322 can be characterized as being aligned together along an illumination axis (not shown). The beam splitter 304 can reflect light transmitted along the illumination axis (i.e., from the light source 322) into the objective 302, where it is focused onto/into the transparent component 324. The objective 302, lens tube 306 and camera 308 can be characterized as being aligned together along an imaging axis (not shown). Light reflected from the transparent component 324 into the objective 302 can be transmitted through the beam splitter 304 along the imaging axis to the camera 308. Thus, the beam splitter 304 is aligned along the illumination and imaging axes. Constructed as described above, the focusing lens 320 functions to collect and collimate light emitted by the light source 322 (i.e., illumination light). From the focusing lens 320, the illumination light is eventually transmitted through the patterned reticle 314. The identification mark detection system 300 is thus configured to project the field stop pattern (e.g., as discussed above) through a transparent component 324 (e.g., formed of clear glass, sapphire, or a polymeric material such as polycarbonate). The transparent component 324 includes an upper surface 324a, which is transparent (or at least substantially transparent) to light projected by the identification mark detection system 300 (e.g., from the objective 302). The transparent component 324 also includes a lower surface 324b that is coated with a light-colored coating (e.g., white paint). Such a coating is not shown in FIG. 3. The field stop pattern is projected through the upper surface 324a, through the interior of the transparent component 324, and onto the coating coated onto the lower surface 324b of the transparent component 324.

Notwithstanding the construction described above, it should be appreciated that the identification mark detection system 300 may be constructed differently. For example, one or both of the field stop 312 and the aperture stop 318 may be omitted from the identification mark detection system 300. In another example, the second set of lenses 316 may be omitted from the identification mark detection system 300. In another example, the first set of lenses 310 may be moved so as to be interposed between the field stop 312 and the patterned reticle 314. In another example, and although not illustrated in FIG. 3, the identification mark detection system 300 may optionally include a diffuser arranged on the opposite side of the focusing lens 320 from the light source 322 (e.g., such that the focusing lens 320 is interposed between the light source 322 and the diffuser). In one embodiment, the diffuser can be provided as a holographic diffuser. The diffuser may act to make the light transmitted by the focusing lens 320 slightly less collimated, and slightly more uniform.

In one embodiment, and although not shown, the identification mark detection system 300 may optionally include a focus adjustment mechanism operative to move the focus point of the identification mark detection system 300 from above to below (or vice- versa) an

identification mark embedded within the transparent component 324. In one embodiment, the focus adjustment mechanism may be provided as a variable focus lens, a variable radius mirror, a mechanical stage, or the like or any combination thereof. When provided as a variable focus lens or a variable radius mirror, the focus adjustment mechanism may be incorporated into the identification mark detection system 300 at any suitable or desired location (e.g., interposed between the objective 302 and beam splitter 304). When provided as a mechanical stage, the focus adjustment mechanism may be operative to support and move the objective 302 (e.g., relative to the transparent component 324), to support and move the transparent component 324 (e.g., relative to the objective 302), or the like or any combination thereof.

In one embodiment, the patterned reticle 314 is a stationary fixture within the

identification mark detection system 300. In an alternative embodiment, however, the patterned reticle 314 may be moveable within the identification mark detection system 300. In this alternative embodiment, the identification mark detection system 300 may include a motion stage (e.g., a motorized motion stage) coupled to the patterned reticle 314 and configured to move the patterned reticle 314 (e.g., such that the light and dark areas of the patterned reticle 314 move along a direction transverse to an optical axis of the second set of lenses 316).

In view of the discussion provided above, the field stop pattern projected by the identification mark detection system 300 can be considered as being derived from the pattern of light and dark areas of the patterned reticle 314. In another embodiment, the projected field stop pattern can be derived from an electrically- or optically-addressable spatial light modulator (e.g., a micro-mirror array, a liquid crystal light valve, or the like), generically referred to herein as an "addressable spatial light modulator." In this case, the identification mark detection system 300 can include the addressable spatial light modulator instead of, or in addition to, the patterned reticle 314. Generally, the addressable spatial light modulator is operative to generate and vary an arrangement of light and dark areas that can ultimately form the field stop pattern projected by the identification mark detection system 300. To the extent that a field stop pattern projected by the identification mark detection system 300 can be considered as being derived from the pattern of light and dark areas of the patterned reticle 314 or derived from a pattern created by the addressable spatial light modulator, each of the patterned reticle 314 and the addressable spatial light modulator can be generically referred to as a "spatial light modulator."

Although not illustrated, the identification mark detection system 300 may further include a computer (e.g., a general purpose computer) coupled to an output of the camera 308 (i.e., when the camera 308 is provided as a digital camera). In this case, the camera 308 may generate image data corresponding to imagery (e.g., captured from light reflected from the transparent component 324 and transmitted through to the camera 308 through the objective 302, the beam splitter 304 and lens tube 306) and the computer may be configured (e.g., with appropriate image processing hardware and/or software) to process the image data to detect the presence of an identification mark embedded within the transparent component 324. The computer may further be configured to generate and output detection data based upon the processing of the image data.

In one embodiment, the first set of lenses 310 is designed such that chromatic aberration is emphasized so that colors of the human-visible spectrum of light reflected back from the transparent component 324 are spread over a range of expected positions of an embedded mark within the transparent component 324. In this embodiment, the relay lens in the lens tube 306 is designed to converge the spread colors of the human- visible spectrum of light onto a sensor of the digital camera 308.

Although not illustrated, the identification mark detection system 300 may further include a controller communicatively coupled to the computer (e.g., to an I/O port, a USB port, etc., of the computer), to an input of the focus adjustment mechanism, to an input of the camera 308 (e.g., in the case the that the camera 308 is a digital camera), to an input of the motorized motion stage (which, in turn, is coupled to the patterned reticle 314) and/or of the addressable spatial light modulator, or the like or a combination thereof, and be configured to control an operation of any of the components to which it is coupled.

For example, in one embodiment, the controller be configured to control the operation of the focus adjustment mechanism (e.g., to move the focus point of the identification mark detection system 300 as discussed above). The controller may further be configured to control an operation of the computer or the camera 308 (i.e., to capture imagery of light reflected from the transparent component 324) after the focus point of the identification mark detection system 300 has been moved. In one embodiment, the focus point of the identification mark detection system 300 can be repeatedly moved by an incremental distance, and imagery can be captured each time the focus point has been moved. By alternately moving the focus point and capturing the resulting imagery, the computer can process the image data to determine the focus point where the embedded mark is present within the transparent component 324.

In another example embodiment, the controller may be configured to control the operation of the motorized motion stage (which, in turn, is coupled to the patterned reticle 314) and/or of the addressable spatial light modulator so as to shift the pattern or light and dark areas of a field stop pattern projected by the identification mark detection system 300. The controller may further be configured to control an operation of the computer or the camera 308 (i.e., to capture imagery of light reflected from the transparent component 324) after the pattern of light and dark areas of the projected field stop pattern has been shifted. In one embodiment, the pattern of light and dark areas of the projected field stop pattern has been shifted can be repeatedly shifted by an incremental distance, and imagery can be captured each time the pattern has been shifted. Generally, the incremental distance can be in a range from 0.1 μιη (or about 0.1 μιη) to 10 μιη (or about 10 μιη) (e.g., 0.2 μιη, 0.5 μιη, 0.8 μιη, 1 μιη, 2 μιη, 4 μιη, 5 μιη, 8 μιη, 9 μιη, etc., or between any of these values). By alternately shifting the pattern and capturing the resulting imagery, imagery of each region of the embedded mark can be captured with backgrounds of varying brightness levels. Image data corresponding to this captured imagery can thus facilitate, at the computer, accurate and reliable detection of an embedded mark within the transparent component 324. The process of capturing imagery at varying brightness levels, as discussed above, can be performed after the determining focus point where the embedded mark is present within the transparent component 324.

Generally, the controller includes one or more processors configured to control one or more operations of the focus adjustment mechanism generate the aforementioned control signals upon executing instructions. A processor can be provided as a programmable processor (e.g., including one or more general purpose computer processors, microprocessors, digital signal processors, or the like or any combination thereof) configured to execute the instructions.

Instructions executable by the processor(s) may be implemented software, firmware, etc., or in any suitable form of circuitry including programmable logic devices (PLDs), field- programmable gate arrays (FPGAs), field-programmable object arrays (FPOAs), application- specific integrated circuits (ASICs) - including digital, analog and mixed analog/digital circuitry - or the like, or any combination thereof. Execution of instructions can be performed on one processor, distributed among processors, made parallel across processors within a device or across a network of devices, or the like or any combination thereof. In one embodiment, the controller includes tangible media such as computer memory, which is accessible (e.g., via one or more wired or wireless communications links) by the processor. As used herein, "computer memory" includes magnetic media (e.g., magnetic tape, hard disk drive, etc.), optical discs, volatile or non- volatile semiconductor memory (e.g., RAM, ROM, NAND-type flash memory, NOR-type flash memory, SONOS memory, etc.), etc., and may be accessed locally, remotely (e.g., across a network), or a combination thereof. Generally, the instructions may be stored as computer software (e.g., executable code, files, instructions, etc., library files, etc.), which can be readily authored by artisans, from the descriptions provided herein, e.g., written in C, C++, Visual Basic, Java, Python, Tel, Perl, Scheme, Ruby, etc. Computer software is commonly stored in one or more data structures conveyed by computer memory.

The foregoing is illustrative of embodiments and examples of the invention, and is not to be construed as limiting thereof. Although a few specific embodiments and examples have been described with reference to the drawings, those skilled in the art will readily appreciate that many modifications to the disclosed embodiments and examples, as well as other embodiments, are possible without materially departing from the novel teachings and advantages of the invention. Accordingly, all such modifications are intended to be included within the scope of the invention as defined in the claims. For example, skilled persons will appreciate that the subject matter of any sentence, paragraph, example or embodiment can be combined with subject matter of some or all of the other sentences, paragraphs, examples or embodiments, except where such combinations are mutually exclusive. The scope of the present invention should, therefore, be determined by the following claims, with equivalents of the claims to be included therein.

Claims

WHAT IS CLAIMED IS:

1. A method of detecting a mark embedded within a region of a transparent component, the transparent component having a first surface and a second surface opposite the first surface and a light-colored coating formed on the second surface below the embedded mark, the method comprising:

projecting a pattern of light and dark regions through the region of the transparent component and onto the coating; and

capturing an image of the embedded mark and the projected pattern.

2. A microscope system, comprising:

a light source, a spatial light modulator, a lens and a beam splitter aligned along an illumination axis; and

a camera and objective aligned along an imaging axis,

wherein the beam splitter is also aligned along the imaging axis,

wherein the spatial light modulator is configured to spatially modulate light emitted by the light source to produce an arrangement of light and dark areas.

3. The microscope system of claim 2, wherein the spatial light modulator includes a patterned reticle.

4. The microscope system of claim 3, further comprising a motorized stage coupled to the patterned reticle, wherein the motorized state is configured to move the patterned reticle along a direction transverse to the illumination axis.

5. The microscope system of claim 2, wherein the spatial light modulator includes an addressable spatial light modulator.

6. The microscope system of claim 2, further comprising a focus adjustment mechanism configured to adjust a position of a focus point of the microscope system.