Patent Description:
Embodiments of the present disclosure are generally directed to a configurable fixture for cutting shapes. More specifically, embodiments are directed to a configurable fixture that is used to cut eyepieces from a (e.g., plastic) wafer, a fixture employing multiple pins of different lengths to support and/or stabilize the wafer, and an inlay of the desired shape to be cut.

In general, innovative aspects of the subject matter described in this specification can be included in one or more embodiments of an apparatus for cutting a wafer into one or more shapes, the apparatus being defined in claim <NUM>.

One or more embodiments can optionally include one or more of the following features.

In some embodiments, a thickness of the inlay and a length of the short pins provide a cutting trench for the laser.

In some embodiments, the fixture further includes a second floor below the first floor; the first floor and the second floor each include a second array of ventilation holes; and the fixture further includes a cavity, below the second floor, which connects to the second array of ventilation holes and to an air duct.

In some embodiments, the apparatus further includes a cover that rests on the wafer and on the long pins.

In some embodiments, the cover includes a gap in a region of the cover that corresponds to the position of the inlay.

In some embodiments, the inlay includes a recess; and the short pegs contact the inlay in the recess.

In some embodiments, cutting eyepieces from a wafer includes positioning the wafer in a fixture and laser cutting the wafer into a shape that corresponds to a shape of an inlay to yield a cut portion of the wafer. The fixture includes a floor defining an array of pin holes configured to hold a plurality of pins, and an inlay that rests on short pins of the plurality of pins. The inlay defines holes that receive medium pins of the plurality of pins to stabilize the inlay from moving in a direction parallel to the first floor. The wafer rests on long pins of the plurality of pins, and the cut portion of the wafer rests on the inlay.

In some embodiments, a vacuum may be applied to the floor to remove, from the fixture, debris generated by the laser cutting.

In some embodiments, the wafer may be positioned in direct contact with the inlay. A plastic film may be adhered to the wafer before laser cutting the wafer.

In some embodiments, a space defined by the fixture beneath the wafer is present along a cutting line of the laser. The space may reduce a reflection of the laser cutting the wafer.

In some embodiments, the short pins prevent bowing of the inlay during the laser cutting of the wafer.

In some embodiments, the laser cutting is achieved in in conjunction with a computer numerically controlled laser cutter.

It is appreciated that aspects and features in accordance with the present disclosure can include any combination of the aspects and features described herein. That is, aspects and features in accordance with the present disclosure are not limited to the combinations of aspects and features specifically described herein, but also include any combination of the aspects and features provided.

The details of one or more embodiments of the present disclosure are set forth in the accompanying drawings and the description below.

Embodiments of the present disclosure are directed to a fixture used in the manufacture of an eyepiece, to cut the eyepiece to a particular shape. Embodiments of the present disclosure are also directed to a method of using the fixture to cut the eyepiece to have the desired shape. Embodiments are directed to a configurable fixture to align, hold, and protect a plastic sheet (referred to herein as a wafer) while a laser cutting apparatus is cutting one or more eyepieces out of the wafer. During the cutting, the fixture protects the eyepieces from reflected laser light by providing voids around the laser cutting lines, and by supporting each eyepiece near its perimeter. The fixture can be quickly rearranged for different eyepieces, different eyepiece shapes, and/or different plastic sheet sizes.

The fixture includes components that help align the surface of the wafer to the laser cutting apparatus, and that hold it in place while the cutting is being performed. The fixture protects the eyepieces from laser light reflection, while also protecting the eyepieces from damage on the edges and the interior of eyepiece. The fixture prevents laser marks on the transparent, plastic eyepieces by reducing and/or eliminating laser reflection off of metal components. The fixture also enables reconfiguration of tool components to laser cut different eyepiece shapes, wafer layouts, different wafer sizes (e.g., wafer diameters and/or widths of <NUM>, <NUM>, etc., wafer thicknesses of <NUM> - <NUM>, etc.), and/or eyepiece quantities, without high machining costs and long lead times.

The fixture can be used in conjunction with a computer numerically controlled (CNC) laser cutter, which enables laser cutting of the wafers. In some instances, the wafers may have grating patterns applied to them prior to cutting, such that the cut eyepieces carry the grating patterns that are suitable for use in an optical device as described below. The fixture is configured to align the wafer relative to the laser cutting tool coordinate system. In some embodiments, the plastic wafer can be molded to include a repeatable, circular diameter edge with a notch that can be used to align the wafer relative to the laser cutting tool coordinate system. In some examples, wafer gratings can be aligned visually to pockets in the inlay. For example, the exit pupil expander (EPE) grating can be aligned to a rectangular pocket in the inlay.

The fixture also supports and holds the wafer in place before, during, and after cutting. The fixture can be rearranged for different plastic eyepiece shapes, wafer layouts, and quantities. Various techniques can be employed to stabilize the wafer. For example, the inlay can support the wafer from below, while the vacuum pulls the wafer into contact with the inlay. In some cases, such as with high air flow from the laser or weaker vacuum due to openings in the partition on the pins, the wafer can be affixed temporarily (e.g., using tape) to the cutting fixture to reduce the chance of slipping. In some embodiments, a thin mechanical clamp can be employed to hold the wafer to the fixture.

Embodiments provide various technical improvements and technical advantages over previously available technology. For example, the fixture described herein produces clearer, more transparent eyepieces, because there are deep trenches rather than metal components near the laser cutting beam's travel path. The fixture also provides significant advantages by accommodating product design and/or wafer layout changes, given that the amount of long-lead machined parts that would be needed cost less and have a shorter lead time than the custom cutting inlays that were previously used.

In some examples, the wafer that is being cut into one or more eyepieces has been previously processed to add grating(s) to the wafer, such that the cut eyepiece(s) can include various eyepiece grating regions with different diffraction gratings to achieve various optical effects. Such regions can include an orthogonal pupil expander (OPE) region, an EPE region, and an in-coupling grating (ICG) region. When the eyepiece is included as a component of a virtual reality headset, augmented reality headset, or other suitable apparatus, a projector of the apparatus may project image light onto the ICG region of an eyepiece layer. The ICG region can couple the image light from the projector into a planar waveguide that propagates the light in a direction toward the OPE region. The waveguide may propagate the image light in the horizontal direction through internal reflection. The OPE region can include a diffractive grating that multiplies and redirects the image light toward the EPE region. For example, the OPE region may multiply the light in an orthogonal direction and direct the multiplied light to various portions of the EPE region. The EPE region can include a (e.g., different) diffractive grating that out-couples and directs at least a portion of the light, in a direction outward from the plane of the eyepiece layer, and/or toward the human viewer's eye. For example, the EPE grating can direct light at an angle that is substantially perpendicular to the plane of the eyepiece layer, and/or at some other angle such as a <NUM> degree angle relative to the plane of the eyepiece layer. In this fashion, an image projected by the projector may be received and viewed by the viewer's eye. For mixed reality (e.g., augmented or virtual reality) diffraction grating waveguide displays, EPE and OPE regions are used to display an image with an expanded pupil area. Additional configurations are possible wherein the OPE and EPE functions are overlaid, combined, or otherwise superimposed to occupy a single region of the eyepiece on one or both sides.

Although examples herein describe a fixture that can be used to cut shapes from a wafer of plastic, other suitable materials may also be cut using the fixture. For example, a fixture can be used to reduce contamination when cutting glass, crystalline ceramic (e.g., Neo), and/or sapphire. Use of the fixture can also reduce lead time and cost for research and development (R&D) fixtures compared to use of a custom inlay for each wafer design.

<FIG> depicts an example fixture <NUM> for cutting eyepiece shapes from a wafer of plastic or other suitable material, according to embodiments of the present disclosure. A floor of the fixture <NUM> can include any suitable number of holes <NUM>, some of which are configured to hold pins <NUM> that extend upward from the floor. At least some of the holes <NUM> may provide for air flow to support an exhaust ventilation feature of the fixture <NUM>, to carry away debris that is generated during the laser cutting of the plastic. Holes <NUM> used to hold pins are referred to herein as pin holes. Holes used for ventilation are referred to herein as ventilation holes. In some embodiments, a first floor <NUM> of the fixture <NUM> may include both pin holes and ventilation holes. A second floor <NUM>, below the first floor <NUM> and flush against it, may include ventilation holes that are substantially aligned with the ventilation holes of the first floor <NUM>. In some instances, the second floor <NUM> may not include the pin holes, thus providing a surface on which the pins <NUM> may rest as the pins <NUM> are supported by the pin holes through the first floor <NUM>. A cavity <NUM> beneath the second floor <NUM> may allow air from above to flow through the ventilation holes, through the cavity <NUM>, and out of the fixture <NUM> through a duct <NUM>. This ventilation system allows air to carry away debris (e.g., plastic debris caused by the cutting) out of the fixture <NUM>, thus reducing the likelihood that the debris will cause damage or degradation to the eyepieces being cut. In some examples, the pin holes are smaller in diameter than the ventilation holes. The ventilation system can also provide a suction effect for maintaining a position of the wafer during cutting. Accordingly, the vacuum can hold the wafer and carry away debris below the wafer. A separate vacuum, with weaker force can also be used above the wafer, in some embodiments.

In some examples, the ventilation holes provide air flow and the pin holes may not provide air flow, given that the pin holes <NUM> extend through the first floor <NUM> and not second floor <NUM>, and are not in communication with duct <NUM>. The pin holes may penetrate the first floor and/or be approximately <NUM> deep, and the ventilation holes may penetrate the first floor and the second floor. In some examples, both types of holes may provide at least some ventilation capability. For example, smaller ventilation holes may be included in the second floor <NUM> that are substantially aligned and/or coincident with larger pin holes <NUM> in the first floor <NUM>.

According to the invention, different lengths of pins <NUM> are used to provide different function and support and/or stabilize different components. The pins <NUM> may be the same, or substantially similar, in diameter, such that any pin <NUM> may be placed in pin hole <NUM>, thus providing for easy change of configuration of the fixture <NUM>. The long pins <NUM> can support the wafer <NUM> (e.g., a plastic substrate) or a vacuum cover <NUM>. Medium pins <NUM> can be used to align an inlay <NUM> (e.g., a machined aluminum eyepiece template, in the shape of the eyepiece to be cut) in the horizontal plane, preventing movement of the inlay <NUM> in x- and y-direction with the fixture (e.g., where the x-y plane is substantially parallel to the floor(s) of the fixture). In some embodiments, aluminum is used for the template because it is cleanroom compatible, and can be anodized black. Other cleanroom compatible metals that can be coated and/or colored black could also be used, including but not limited to steel or stainless steel painted black, or titanium with a black coating.

The inlay <NUM> includes holes or indentations that the medium pins <NUM> fit into, to stabilize the inlay <NUM> in the horizontal plane and prevent movement of the inlay <NUM> before, during, and after cutting. The short pins <NUM> support the inlay <NUM> from below, in the vertical direction. For clarity, the short pins are not shown in the example of <FIG>. The pins <NUM> can be arranged in the floor <NUM> in the pin holes <NUM>. The wafer <NUM> to be cut rests on top of the inlay <NUM> and the top of long pins <NUM>, which are substantially level. Areas of the fixture <NUM> that are not supporting the wafer <NUM> may be covered with a thin, plastic vacuum cover <NUM>, the shape of which can be quickly and cheaply customized using scissors or other suitable tools.

When the components are assembled in preparation for cutting, the wafer <NUM> rests on top of the long pins <NUM>. Shorts pins <NUM> are placed to support the inlay(s) <NUM>, with the inlay(s) <NUM> being placed under the wafer <NUM>. The medium pins <NUM> stabilize the inlay(s) <NUM> in the x-y plane as described above. In this example view, the cutting laser is looking down onto the assembly. Any suitable length of the short, medium, and long pins <NUM> can be employed. For example, the long pins <NUM> may each be <NUM> long, the short pins <NUM> may each be <NUM> long, and the medium pins <NUM> may be each <NUM> long (within acceptable tolerance of variation in the lengths). The pins <NUM> may have substantially the same cross-sectional shape and same diameter, to provide for flexibility in the configuration of the apparatus to hold different numbers and shapes of inlays <NUM> and to cut different numbers and shapes of eyepieces out of the wafer <NUM>. In some examples, the inlay <NUM> is flush against the wafer <NUM> to provide for more accurate cutting by the laser. If there were any clearance between wafer <NUM> and inlay <NUM>, the wafer <NUM> may flex if it were not fully supported by the inlay <NUM> from below. In some configurations, the laser cutting apparatus may cut a shape that is substantially the same as the shape of the inlay <NUM>, although the laser cutting may be controlled independently of the inlay <NUM> shape (e.g., by a computer controlling the laser). The cutting laser may be programmed to follow the perimeter of the inlay <NUM>, or just outside of the perimeter of the inlay <NUM>, such that inlay <NUM> represents the shape of the eyepiece that is to be cut out from the wafer <NUM>.

The (e.g., rectangular) vacuum cover <NUM> over the assembly can be placed to provide a stronger vacuum suction over the exhaust area, and to ensure that that applied vacuum is pulling on all portions of the cover <NUM>. The cover <NUM> may have a gap over each position where an eyepiece is to be cut from the wafer, with a gap between the edge of the inlay <NUM> to the edge of the gap in the cover <NUM>. In some examples, this gap may be minimized to provide stronger vacuum.

Cutting plastic with a laser generates a cloud of debris. The debris is scattered everywhere, and can land on the plastic part that has been warmed by the laser. The debris may permanently stick to the plastic part as it cools, and is not easily removed once the plastic cools. In some examples, to avoid debris, a rigid plastic (i.e. PMMA) sheet is placed under the wafer <NUM> to provide a barrier for the debris. By using such a sheet, there is less clearance between the wafer <NUM> and the rigid plastic sheet that provides a barrier. Also, a (e.g., thin) sheet of plastic may be placed on top of the wafer <NUM> as another debris barrier. By using a thin sheet, it may be easier for the laser to cut through the top sheet and continue cutting the wafer <NUM>. In some examples, the three sheets can be taped together using polyimide tape or any tape that is easily removed.

In some embodiments, an approximately <NUM> thick piece of PMMA can be used underneath the wafer. Alternatively, instead of the plastic sheet, a thin plastic film such as a semiconductor dicing tape product (e.g., including PVC film and adhesive) can be used under the plastic wafer and on top of the wafer. Semiconductor dicing tape can be used on both sides to protect the wafer from cutting debris.

Previously available solutions included shapes or surfaces that caused reflections of the laser light onto the plastic being cut. Such reflections caused marks to be etched into the surface of the plastic, leaving flaws in the cut eyepieces that could negatively impact eyepiece performance. The fixture <NUM> described herein uses materials that are less reflective (e.g., anodized aluminum) and/or surfaces that tend to scatter the laser light (e.g., round pins), reducing or eliminating such reflections.

The fixture <NUM> provides for a space beneath the plastic that is being cut. That space is also referred to as a trench. For optimal cutting, the depth of the trench (e.g., the amount of clearance that is open under the wafer that is being cut) is approximately <NUM>-<NUM> for plastic cutting. The trench is present along the cutting line where the laser is cutting the plastic, and has sufficient depth to reduce reflection.

The short pins <NUM> provide support for the interior of the inlay <NUM> and hold up the center to prevent bowing of the inlay <NUM> and the wafer portion on top of the inlay <NUM>. The cover <NUM> is present to ensure strong vacuum suction and prevent the wafer from sliding around. In one example, the wafer <NUM> size is approximately <NUM> square, and the cover <NUM> is approximately <NUM> square fitting within the fixture <NUM> as shown in the figures.

In some embodiments, but not according to the invention, the short pins may not be used, and the inlay(s) <NUM> may rest on the floor <NUM> of the fixture <NUM>. In such examples, the inlay(s) <NUM> may be machined thick enough to provide the appropriate trench depth for cutting. In general, the trench depth is the thickness of the inlay <NUM> plus the length of the short pins (if used).

In some embodiments, the wafer <NUM> may have a protective film that is in place on the wafer <NUM> (on one or both sides of the wafer) while the wafer is being cut. Use of the film may further prevent debris from coalescing on the warm plastic, causing a whitening effect along the edge of the eyepiece. In some examples, the fixture <NUM> may be made of aluminum which has been anodized to reduce reflection of the laser light toward the eyepiece being cut. The pins may be made of stainless steel, (e.g., anodized) aluminum, or any other suitable material. In one example, the spacing between holes <NUM> in the floor(s) is <NUM> between pin holes, and <NUM> between ventilation holes, in both x- and y-direction. The holes may be placed sufficiently close to one another to provide suitable flexible in arranging the pins to support different shapes and numbers of inlays <NUM> for eyepiece cutting.

Embodiments can employ any suitable spacing between pin holes and/or ventilation holes, and may employ any suitable number of pins in the inlay to provide appropriate support and stabilization. For example, spacing of <NUM>-<NUM> between the holes <NUM> can be used. Any number of sets of two of the medium length pin (e.g., <NUM> long) can be used to set the x and y location of the inlay. Any number of sets of four of the shortest length pin (e.g., <NUM> long) can be used to support the z position of the inlay. Accordingly, a set of six pins minimum may be used to support and stabilize the inlay.

According to the invention, the medium pins <NUM> are set into holes in the inlay <NUM>, to prevent the inlay <NUM> from moving in the x-y plane. The short pins <NUM> support the inlay <NUM> from below. In some embodiments, one or both sides of the inlay <NUM> may have a recess cut out of the interior of the inlay <NUM>, such that the inlay <NUM> has a lip around its perimeter. This recess serves to minimize contact between the inlay <NUM> and the wafer <NUM>, to minimize any scraping of and damage to the gratings in the eyepiece portion of the wafer <NUM> that might be caused by contact with the inlay <NUM>. The inlay <NUM> also helps keep the eyepiece portion of the wafer flat, so that the vacuum pulling on the wafer <NUM> does not deform the eyepiece portion that is being cut out.

The trench underneath the cutting lines may be defined by the grid of pins <NUM> placed relative to the inlay <NUM>. The pins <NUM> along the cutting contour may be removed to provide the trench such that holes near a perimeter of the inlay <NUM> are empty. The trench depth can be a function of pin length and inlay thickness, as described above. The grid of pin holes can be machined such that each hole has a sliding fit with the pin, to provide for easy insertion and removal of the pins to and from the pin holes. The fixture <NUM> provides that the pins can be arranged in any appropriate number of combinations to support inlay(s) and wafer, and to provide the appropriate deep trenches for cutting. The inlay(s) <NUM> are moveable and readily replaceable, and have a minimized footprint for reduced cost and lead time.

<FIG> depicts an example fixture <NUM> for cutting eyepiece shapes, according to embodiments of the present disclosure. <FIG> shows a view of the fixture <NUM> more from above, with the templates <NUM> placed for different eyepiece shapes to be cut. The wafer sits on top of the inlays <NUM> as discussed above, and the cover <NUM> sits on top of the wafer <NUM>.

<FIG> depicts a portion of an example fixture <NUM>, according to embodiments of the present disclosure. <FIG> shows the pins <NUM> of varying length and position supporting the inlay <NUM> and wafer <NUM>, and stabilizing the inlay <NUM> against movement. <FIG> also shows the different types of holes <NUM>, including an array of ventilation holes 118A and an array of pin holes 118B, where the ventilation holes may extend through all layers of the floor and the pin holes may extend only partially through the floor.

<FIG> depict an example fixture <NUM> being used in an example cutting apparatus <NUM>, according to embodiments of the present disclosure. <FIG> depicts fixture <NUM> placed below the laser cutting apparatus <NUM>, with a direction of the cutting laser shown by the arrow <NUM>. <FIG> is a closer view of the fixture <NUM> beneath the cutting laser <NUM>. <FIG> provides a different close view of the fixture <NUM> beneath the cutting laser <NUM>, with the inlay <NUM> arranged accordingly to the outline of the eyepiece to be cut. As shown in <FIG>, the wafer from which eyepieces are cut can be significantly larger than the inlay size in some embodiments. In such configurations, one of skill in the art will appreciate that the wafer itself may serve as the vacuum cover <NUM> (e.g., as shown in <FIG>).

<FIG> depicts an example fixture <NUM>, according to embodiments of the present disclosure, where an inlay <NUM> is supported by pins <NUM> inserted into holes in a floor of the fixture <NUM>. As shown in this example, a wafer <NUM> is positioned over the inlay <NUM> in preparation for cutting out an eyepiece around the outside perimeter of the wafer material.

As discussed above, previously available techniques left an undesired etching on the eyepiece, caused by laser light reflected off surfaces of the previously used fixture. <FIG> depicts an example eyepiece <NUM> manufactured according to such previously available techniques, with an undesirable artifact of etching left by the manufacturing process. In <FIG>, a honeycomb (e.g., hex-shaped) pattern <NUM> can be seen along the edges of the EPE and OPE. A cloudy appearance <NUM> can also be seen along the part edge, even where no gratings are present. This can be caused by the laser having reflected off the previously used stainless steel honeycomb fixture and burned away the gratings in the visible honeycomb pattern. This results in crooked, wavy, and/or hex-shaped OPE and EPE edges, such that the eyepiece may not meet requirements for quality.

<FIG> depict example eyepieces <NUM>, <NUM>, respectively, manufactured according to embodiments of the present disclosure. Eyepiece <NUM> shows an example eyepiece that is cut while not having the protective film, leading to the whitening <NUM> around the edge caused by implanted debris. Eyepiece <NUM> shows an example eyepiece that is cut while the protective film is on the wafer, thus preventing the edge whitening.

<FIG> depict example fixture <NUM>, according to embodiments of the present disclosure. Fixture <NUM> includes a dotted overlay that shows an outer boundary of the cover <NUM> described above. As shown in this example, the cover <NUM> may sit on each of the edges of the fixture <NUM> to provide suitable vacuum. <FIG> includes a dotted overlay <NUM> that shows the inner cutout of the cover <NUM> to illustrate a boundary of the gap <NUM> between the cover <NUM> and an outer perimeter of a wafer that may be present over each of the eyepieces to be cut, as described above. In this example, the cover is overlaid on the wafer so that there is some overlap at the outside edges of the wafer. The wafer rests directly on the inlay and pins. The thin vacuum cover rests on top of the wafer, with a cutout portion to make the cutting profile available to the laser.

<FIG> and <FIG> depict example fixture <NUM>, according to embodiments of the present disclosure. In this example, the fixture <NUM> includes ribs <NUM> that support two plates that each include the (e.g., <NUM>) ventilation holes, with one of the two plates also including the (e.g., <NUM>) pin holes as well. The pins could contact the bottom of this enclosure, and/or contact the ribs depending on the location. The pin height may vary depending on whether the pins are placed into holes to contact the bottom of the enclosure or the rib.

While this specification contains many specific details, these details should not be construed as limitations on the scope of the disclosure or of what may be claimed, but rather as examples of features that are associated with particular embodiments. Certain features that are described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment.

Claim 1:
An apparatus for cutting a wafer (<NUM>) into one or more shapes, characterized in that the apparatus comprises:
a fixture (<NUM>) including a first floor (<NUM>), wherein the first floor includes an array of pin holes ;
a plurality of pins (<NUM>) held in the array of pin holes, the plurality of pins (<NUM>) comprising:
long pins;
medium pins; and
short pins;
an inlay (<NUM>) that rests on the short pins (<NUM>), wherein the inlay (<NUM>) includes holes or indentations that receive the medium pins (<NUM>) to stabilize the inlay (<NUM>) from moving in a direction parallel to the first floor; and
a laser,
wherein, in use, the long pins are configured to support the wafer (<NUM>) and the short pins are configured to support the inlay while the laser cuts, from the wafer (<NUM>), a shape that corresponds to the inlay (<NUM>), and such that the cut portion of the wafer (<NUM>) rests on the inlay (<NUM>).