Optical polymer films and methods for casting the same

An example system is configured to photocure a photocurable material to form a polymer film. The system includes a first chuck configured to support a first substantially planar mold, a second chuck configured to support a second substantially planar mold, and an actuable stage coupled to the first chuck and/or the second chuck. The actuable stage is configured to position the first chuck and/or the second chuck so that the first and second molds are separated by a gap. The system also includes a sensor arrangement for obtaining measurement information indicative of a distance between the first and second molds and/or a pressure between the first and second chucks at each of at least three locations. The system also includes a control module configured control the gap between the first and second molds based on the measurement information.

TECHNICAL FIELD

This disclosure relates to optical polymer films.

BACKGROUND

Optical imaging systems, such as wearable imaging headsets, can include one or more eyepieces that present projected images to a user. Eyepieces can be constructed using thin layers of one or more highly refractive materials. As examples, eyepieces can be constructed from one or more layers of highly refractive glass, silicon, metal, or polymer substrates.

In some cases, an eyepiece can be patterned (e.g., with one or more light diffractive nanostructures), such that it projects an image according to a particular focal depth. For an example, to a user viewing a patterned eyepiece, the projected image can appear to be a particular distance away from the user.

Further, multiple eyepieces can be used in conjunction to project a simulated three-dimensional image. For example, multiple eyepieces—each having a different pattern—can be layered one atop another, and each eyepiece can project a different depth layer of a volumetric image. Thus, the eyepieces can collectively present the volumetric image to the user across three-dimensions. This can be useful, for example, in presenting the user with a “virtual reality” environment.

To improve the quality of a projected image, an eyepiece can be constructed such that unintended variations in the eyepiece are eliminated, or otherwise reduced. For example, an eyepiece can be constructed such that it does not exhibit any wrinkles, uneven thicknesses, or other physical distortions that might negatively affect the performance of the eyepiece.

SUMMARY

System and techniques for producing polymer film are described herein. One or more of the described implementations can be used to produce polymer film in a highly precise, controlled, and reproducible manner. The resulting polymer films can be used in a variety of variation-sensitive applications in which extremely tight tolerances on film dimensions are desired. For instance, the polymer films can be used in optical applications (e.g., as a part of eyepieces in an optical imaging system) in which material homogeneity and dimensional constraints on the order of optical wavelengths or smaller.

In general, polymer films are produced by enclosing a photocurable material (e.g., a photopolymer or light-activated resin that hardens when exposed to light) between two molds, and curing the material (e.g., by exposing the material to light).

However, during the curing process, the material may expand or contract within the molds. As a result, the film may become distorted (e.g., wrinkled, stretched, or compressed). Further, if the molds are not kept precisely parallel to each other, the film may have an uneven thickness across its extent. Accordingly, the film may be less suitable for use in variation-sensitive applications.

To improve the quality and consistency of the film, the position of the two molds can be precisely controlled, such that the molds are kept parallel to each other as the material is being cured. Further, during the curing process, the position of the molds can be adjusted to account for physical changes in the photocurable material. For example, if a particular photocurable material is known to contract at a particular rate, during the curing process, the two molds can be progressively drawn towards each other to account for the contraction. Thus, the space between the molds more closely matches the volume of the photocurable material throughout the curing processes. As a result, the photocurable material has a more even thickness, and is less likely to become distorted.

In some cases, the position of each mold can be detected using sensors (e.g., capacitive sensors and/or pressure sensors) mounted on or near the molds. Information from the sensors can be used to adjust the position of each mold relative to the other (e.g., using an actuable stage).

The quality and consistency of film can be further improved by reducing the presence of bubbles or trapped air between the two molds. In some cases, bubbles or trapped air can be reduced by depositing the photocurable material in a first mold, then drawing a second mold towards the first mold until the second mold contacts the photocurable material. The second mold can be skewed (e.g., rotated, bowed, and/or bent) relative to the first mold, such that any air between the two molds can escape as the molds are drawn together. Subsequently, the molds can be reoriented relative to one another (e.g., in a parallel orientation) prior to curing.

In general, in an aspect, a system for photocuring a photocurable material to form a polymer film includes a first chuck configured to support a first substantially planar mold having a first mold surface during use of the system, and a second chuck configured to support a second substantially planar mold having a second mold surface during use of the system. The second chuck includes a least a portion adjacent the second mold that is substantially transparent to one or more wavelengths of radiation suitable for photocuring the photocurable material. The system also includes an actuable stage coupled to the first chuck and/or the second chuck. The actuable stage is configured, during use of the system, to position the first chuck and/or the second chuck so that the first and second mold surfaces face each other and are separated by a gap. The system also includes a sensor arrangement for obtaining measurement information indicative of a distance between the first and second mold surfaces at each of at least three locations and/or a pressure between the first and second chucks at each of at least three locations during use of the system. The system also includes a control module communicatively coupled to the actuable stage. The control module is configured, during use of the system, to receive the measurement information and to control the gap between the first and second mold surfaces based on the received measurement information.

In some implementations, the second chuck can be formed from a material transparent to the one or more wavelengths of the radiation.

In some implementations, the one or more wavelengths of the radiation can include at least one of an ultraviolet wavelength or a visible wavelength.

In some implementations, the system can further include a radiation source. The radiation source can be configured, during use of the system, to direct the radiation to a region between the first mold surface and the second mold surface.

In some implementations, the first chuck can include a first substantially flat chuck surface. The second chuck can include a second substantially flat chuck surface facing the first chuck surface.

In some implementations, a flatness of the first chuck surface and a flatness of the second chuck surface each deviate from a flatness of an ideal flat surface by 100 nm or less.

In some implementations, at least one of the first chuck surface or the second chuck surface can be a polished or lapped surface.

In some implementations, the actuable stage can be configured, during use of the system, to translate the first chuck and/or second chuck with respect to at least one dimension.

In some implementations, the actuable stage can be configured, during use of the system, to translate the first chuck and/or second chuck with respect to three orthogonal dimensions.

In some implementations, the actuable stage can be configured, during use of the system, to rotate the first chuck and/or second chuck about at least one axis.

In some implementations, the actuable stage can be configured, during use of the system, to rotate the first chuck and/or second chuck about three orthogonal axes.

In some implementations, the sensor arrangement can include at least one capacitive sensor disposed on the first chuck and/or the second chuck.

In some implementations, the sensor arrangement can include a plurality of capacitive sensors disposed on the first chuck and/or the second chuck.

In some implementations, at least a portion of the first chuck and/or at least a portion of the second chuck can be electrically conductive.

In some implementations, the sensor arrangement can include at least one pressure sensor. Each pressure sensor assembly can be configured, during use of the system, to determine a pressure applied to a corresponding mechanical spacer disposed between the first chuck and the second chuck.

In some implementations, each mechanical spacer can be disposed on one of the first chuck, the second chuck, the first mold, or the second mold.

In some implementations, the sensor arrangement can include a plurality of pressure sensors. Each pressure sensor assembly can be configured, during use of the system, to determine a pressure applied to a corresponding mechanical spacer disposed between the first chuck and the second chuck

In some implementations, the system can further include a vacuum assembly. The vacuum assembly can be configured, during use of the system, to apply vacuum pressure to the first mold to secure the first mold to the first chuck and/or apply vacuum pressure to the second mold to secure the second mold to the second chuck.

In some implementations, controlling the gap between the first and second mold surfaces can include positioning the first chuck and/or the second chuck such that the first mold surface is skewed with respect to the second mold surface, and subsequent to positioning the first chuck and/or the second chuck such that the first mold surface is skewed with respect to the second mold surface, moving the first chuck towards the second chuck.

In some implementations, positioning the first chuck and/or the second chuck such that the first mold surface is skewed with respect to the second mold surface can include positioning the first chuck and/or the second chuck such that an angular displacement between the first mold surface and the second mold surface is between approximately 1° and 10°.

In some implementations, controlling the gap between the first and second mold surfaces can include positioning the first chuck and/or the second chuck, such that the first mold surface and the second mold surface are substantially parallel.

In some implementations, controlling the gap between the first and second mold surfaces can include positioning the first chuck and/or the second chuck, such that an angular displacement between the first mold surface and the second mold surface is less than 10 μrad.

In some implementations, controlling the gap between the first and second mold surfaces can include moving the first chuck towards or away from the second chuck during photocuring of the photocurable material.

In some implementations, the first chuck can be moved towards or away from the second chuck continuously during photocuring of the photocurable material.

In some implementations, the first chuck can be moved towards or away from the second chuck intermittently during photocuring of the photocurable material.

In general, in another aspect, a method of casting a polymer film by photocuring a photocurable material can include dispensing the photocurable material onto a first surface of a first mold, positioning the first mold and a second mold such that the first surface and a second surface of the second mold are separated by a gap, obtaining measurement information indicative of a distance between the first and second molds at each of at least three locations and/or a pressure at each of at least three locations between the first and second molds during use of the system, and controlling the gap between the first and second molds surfaces based on the measurement information.

In some implementations, the method can further include directing, to the photocurable material, one or more wavelengths of radiation suitable for photocuring the photocurable material.

In some implementations, the one or more wavelengths of the radiation can include at least one of an ultraviolet wavelength or a visible wavelength.

In some implementations, the measurement information can be obtained using one or more capacitive sensors.

In some implementations, the measurement information can be obtained using three or more capacitive sensors.

In some implementations, obtaining the measurement information can include determining, using one or more pressure sensors, a pressure applied to each of one or more mechanical spacers disposed between the first and second molds and/or along a periphery of the first and second molds.

In some implementations, obtaining the measurement information can include determining, using three or more pressure sensors, a pressure applied to each of three or more mechanical spacers disposed between the first and second molds and/or along a periphery of the first and second molds.

In some implementations, the method can further include arranging the first mold relative to a second mold in a first configuration. In the first configuration, the first surface of the first mold can face the second surface of the second mold and can be skewed with respect to the second surface, and the photocurable material can contact the second surface of second mold.

In some implementations, in the first configuration, an angular displacement between the first surface of first mold and the second surface of second mold can be between approximately 1° and 10°.

In some implementations, in the first configuration, the second surface of second mold can be bowed with respect to the first surface.

In some implementations, the second surface of the second mold can be bowed by applying pressure to a central portion of the second mold.

In some implementations, in the first configuration, an angular displacement between the first surface of first mold and the second surface of second mold can be between approximately 1° and 10°, and the second surface of second mold can be bowed with respect to the first surface.

In some implementations, the method can further include, subsequent to arranging the first mold and the second mold in the first configuration, arranging the first mold and the second mold in a second configuration. In the second configuration, the first surface and the second surface can be substantially parallel.

In some implementations, the method can further include, subsequent to arranging the first mold and the second mold in the first configuration, arranging the first mold and the second mold in a second configuration. In the second configuration, an angular displacement between the first surface and the second surface can be less than 10 μrad.

In some implementations, the method can further include, subsequent to arranging the first mold and the second mold in the second configuration, directing, to the photocurable material, one or more wavelengths of radiation suitable for photocuring the photocurable material.

In some implementations, the method can further include, while directing the radiation to the photocurable material, decreasing or increasing the distance between the first and second molds over a period of time.

In some implementations, the distance between the first and second molds can be decreased or increased continuously over the period of time.

In some implementations, the distance between the first and second molds can be decreased or increased intermittently over the period of time.

One or more of the implementations described herein can provide various benefits. For example, in some cases, implementations described herein can enable the production of polymer film in a highly precise, controlled, and reproducible manner. The resulting polymer films can be used in a variety of variation-sensitive applications (e.g., as a part of eyepieces in an optical imaging system). Further, polymer films can be produced such that wrinkles, uneven thicknesses, or other unintended physical distortions are eliminated or otherwise reduced. This can be useful, for example, as the resulting polymer film exhibits more predictable physical and/or optical properties.

DETAILED DESCRIPTION

System and techniques for producing polymer film are described herein. One or more of the described implementations can be used to produce polymer film in a highly precise, controlled, and reproducible manner. The resulting polymer films can be used in a variety of variation-sensitive applications (e.g., as a part of eyepieces in an optical imaging system).

In some implementations, polymer films can be produced such that wrinkles, uneven thicknesses, or other unintended physical distortions are eliminated or otherwise reduced. This can be useful, for example, as the resulting polymer film exhibits more predictable physical and/or optical properties. For example, polymer films produced in this manner can diffract light in a more predictable and consistent manner, and thus, may be more suitable for use a high resolution optical imaging system. In some cases, optical imaging systems using these polymer films can produce sharper and/or higher resolution images than might otherwise be possible with other polymer films.

An example system100for producing polymer film is shown inFIG. 1. The system100includes an actuable stage102, chucks104aand104b,a sensor assembly106, light source108, a vacuum system110, and a control module112.

During operation of the system100, two molds114aand114bare secured to the chucks104aand104b,respectively. A photocurable material (e.g., a photopolymer or light-activated resin that hardens when exposed to light) is deposited into the mold114a.The mold114ais moved into proximity with mold114b,such that the curable material is enclosed by the molds114aand114b.The curable material is then cured (e.g., by exposing the curable material to light from the light source108), forming a thin film having one or more features defined by the molds114and114b.After the curable material has been cured, the mold114ais moved away from the mold114b,and the film is extracted.

The actuable stage102is configured to support the chuck104a,manipulate the chuck104ain one or more dimensions, and control a gap region150between the chucks104aand104b.

For instance, in some cases, the actuable stage102can translate the chuck104aalong one or more axes. As an example, the actuable stage102can translate the chuck104aalong an x-axis, a y-axis, and/or a z-axis in a Cartesian coordinate system (i.e., a coordinate system having three orthogonally arranged axes). In some cases, the actuable stage102can rotate or tilt the chuck104aabout one or more axes. As an example, the actuable stage102can rotate the chuck104aalong an x-axis (e.g., to “roll” the chuck104a), a y-axis (e.g., to “pitch” the chuck104a), and/or a z-axis (e.g., to “yaw” the chuck104a) in a Cartesian coordinate system. Translation and/or rotation with respect to one or more other axes are also possible, either in addition to or instead of those described above.

In some cases, the actuable stage102can manipulate the chuck104aaccording to one or more degrees of freedom (e.g., one, two, three, four, or more degrees of freedom). For instance, the actuable stage102can manipulate the chuck104aaccording to six degrees of freedom (e.g., translation along an x-axis, y-axis, and z-axis, and rotation about the x-axis, y-axis, and z-axis). Manipulation according to one or more other degrees of freedom is also possible, either in addition to or instead of those described above.

In some cases, the actuable stage102can include one or more motor assemblies configured to manipulate the chuck104aand control the gap region150. For example, the actuable stage102can include a base portion116containing a motor assembly118, and an articulating portion120configured to support the chuck104. The motor assembly118can be configured to manipulate the articulating portion120using the motor assembly118, thereby repositioning and/or reorienting the chuck104a.

In the example shown inFIG. 1, the actuable stage102is mechanically coupled to the chuck104a,and controls the gap region150by manipulating the chuck104a.Further, the chuck104bis held stationary (e.g., by supports134). In practice, however, the chuck104balso can be manipulated to control the gap region150. For example, in some implementations, the system100can include a second actuable stage configured to manipulate the chuck104b,either instead or in combination with the actuable stage102shown inFIG. 1.

The chucks104aand104bare configured to provide a stable mounting surface for the molds114aand114b,respectively. In some cases, the chucks104aand104bcan be configured such that the molds114aand114bcan be physically mounted to the chucks104aand104b,respectively, through a vacuum mechanism. As an example, as shown inFIG. 1, the chuck104acan define a series of vacuum channels132athat extend through the chuck104a,and the chuck104bcan define a series of vacuum channels132bthat extend through the chuck104b.The vacuum channels132aand132bcan be coupled to a vacuum system110configured to generate a total or partial vacuum within the channels132aand132b.This results in a suction pressure that secures the molds114aand114bto the chucks104aand104b,respectively. The vacuum system110can be configured to selectively generate vacuum in the channels132aand132b,such that the molds114aand114bcan be reversibly mounted to dismounted from the chucks104aand104b.

In some cases, the surfaces of chucks104aand104bthat face each other can each be substantially flat. For example, the chuck104acan include a substantially flat surface122a,and the chuck104bcan have substantially flat surface122b,upon which a respective mold can be mounted. A substantially flat surface can be, for example, a surface that deviates from a flatness of an ideal flat surface (e.g., a perfectly flat surface) by 100 nm or less. In some cases, the surface122aand/or the surface122bcan be polished or lapped such that they are substantially flat. A substantially flat surface can be beneficial, for example, as it enables the molds114aand114bto be mounted in a consistent manner to the chucks104aand104b,such that they can be positioned relative to one another with a high degree of precision by the actuable stage102.

The molds114aand114bcollectively define an enclosure for the photocurable material. For example, the molds114aand114b,when aligned together, can define a hollow mold region, within which the photocurable material can be deposited and cured into a film. The molds114aand114bcan also define one or more structures in the resulting film. For example, the molds114aand114bcan include one or more protruding structures that impart a corresponding channel in the resulting film. As another example, the molds114aand114bcan include one or more channels that impart a corresponding protruding structure in the resulting film. In some cases, the molds114aand114bcan define a particular shape and pattern, such that the resulting film is suitable for use as an eyepiece in an optical imaging system (e.g., such that the film has one or more light diffractive nanostructures that impart particular optical characteristics to the film).

The sensor assembly106is configured to determine the position and/or orientation of the chucks104aand104brelative to one another, such that the system100can precisely control the relative position and/or orientation of the chucks104aand104band control the gap region150. As an example, the sensor assembly106can determine whether the surfaces122aand122bare parallel to each other. As another example, the sensor assembly106can determine that the surfaces122aand122bare inclined with respect to each other, and determine the axis or axes of inclination. As another example, the sensor assembly106can determine the relative distance at one or more locations along the surfaces122aand122b.

In some cases, the sensor assembly106can determine the orientation of the chucks104aand104brelative to one another by measuring the distance between the surfaces122aand122bat three or more locations along the surfaces122aand122b.For example, the sensor assembly106can determine a first distance between a point A1and a point A2on chucks104aand104b,respectively, a second distance between a point B1and a point B2on chucks104aand104b,respectively, and a third distance between a point C1and a point C2on chucks104aand104b,respectively. If the set of points A1, B1, and C1and the set of points A2, B2, and C2are each non-linear, then the first, second, and third distances can be used to determine the orientation of the surfaces122aand122brelative to one another. Further, although an example having three pairs of points is described, in some cases, the sensor assembly106can determine the distance between any number of point pairs (e.g., one pair of points, two pairs of points, three pairs of points, or more), and the pairs of points can be arranged in any orientation (e.g., linearly positioned, non-linearly positioned, or according to any other pattern).

In some cases, a distance between the surfaces122aand122bcan be measured using a capacitive sensor assembly. For example,FIG. 1shows a sensor assembly106having a capacitive sensor124amounted to the surface122bof the chuck104b.The area126aof the surface122afacing the capacitive sensor124ais electrical conductive (e.g., the chuck104bcan be either entirely composed of an electrically conductive material, or composed of an electrically conductive material at least along the area126a). The capacitive sensor124ameasures the capacitance, and based on the measured capacitance, determines the distance between the surfaces122aand122bat this first location. Similarly,FIG. 1also shows a capacitive sensor124bmounted to the surface122bof the chuck104b.The area126bof the surface122afacing the capacitive sensor124ais also electrical conductive (e.g., the chuck104bcan be either entirely composed of an electrically conductive material, or composed of an electrically conductive material at least along the area126b). Likewise, the capacitive sensor124bmeasures the capacitance, and based on the measured capacitance, determines the distance between the surfaces122aand122bat this second location. Although two capacitive sensors124aand124bare shown for illustrative purposes inFIG. 1, in practice, a system100can include any number of capacitive sensors, each configured to measure a distance between the chucks104aand104bat a particular location.

AlthoughFIG. 1depicts the capacitive sensors124aand124bas being mounted to the chuck104b,this need not be the case. For example, in some cases, one or more capacitive sensors can be mounted on the chuck104a,and each of those capacitive sensors can have a corresponding electrically conductive area on the surface122bof chuck104bfacing it. Further, in some cases, capacitive sensors can be distributed across both the chuck104aand104b.Further still, in some cases, one or more capacitive sensors can be distributed across one or both of the molds114aand114b,and have corresponding electrically conductive areas on the molds114aand114bfacing it.

In some cases, the distance between the surfaces122aand122bcan be measured using a pressure sensor assembly. For example,FIG. 1shows a sensor assembly106having a pressure sensor128amounted to the mold114aand beneath a mechanical spacer130a.When the mold114aand114bare brought together, the mechanical spacer130apresses against the mold114b,causing a pressure to be applied to the mechanical spacer130a.The pressure sensor128ameasures the pressure applied to the mechanical spacer130a,and based on the measured pressure, determines the distance between the surfaces122aand122bat this first location. Similarly,FIG. 1also shows a pressure sensor128bmounted to the mold114aand beneath a mechanical spacer130b.The pressure sensor128bmeasures the pressure applied to the mechanical spacer130b(e.g., due to the contact between the mechanical spacer130band the mold114b), and based on the measured pressure, determines the distance between the surfaces122aand122bat this second location. Although two pressure sensors128aand128b(at corresponding mechanical spacers130aand130b) are shown for illustrative purposes inFIG. 1, in practice, a system100can include any number of pressure sensors and/or mechanical spacers, each configured to measure a distance between the chucks104aand104bat a particular location. Further, a system100can include one or more capacitive sensors and one or more pressure sensors in combination to measure the distance between the chucks104aand104b.

AlthoughFIG. 1depicts the pressure sensors128aand128band mechanical spacers130aand130bas being mounted to the mold114a,this need not be the case. For example, in some cases, one or more pressure sensors and/or mechanical spacers can be mounted on the mold114b.Further, in some cases, pressure sensors and/or mechanical spacers can be distributed across both the mold114aand the mold114b.Further still, in some cases, one or more pressure sensors and/or mechanical spacers can be distributed across one or both of the chucks104aand104b.

The light source108is configured to generate one or more wavelengths of radiation suitable for photocuring the photocurable material. The one or more wavelengths can differ, depending on the type of photocurable material used. For example, in some cases, a photocurable material (e.g., a UV-curable liquid silicone elastomer such as

Poly(methyl methacrylate) or Poly(dimethylsiloxane)) can be used, and correspondingly the light source can be configured to generate radiation having a wavelength in a range from 315 nm to 430 nm to photocure the photocurable material. In some cases, one or more of the chucks104aand104band molds114aand114bcan be transparent, or substantially transparent to the wavelengths of radiation suitable for photocuring the photocurable material, such that radiation from the light source108can pass through the chuck104a,the chuck104b,the mold114a,and/or the molds114band impinge upon the photocurable material.

The control module112is communicatively coupled to the actuable stage102and the sensor assembly106, and is configured to control the gap region150based on measurements received from the sensor assembly106. For instance, the control module112can receive measurements regarding gap region150(e.g., the distance between the chuck104aand104bat one or more locations) from the sensor assembly106, and reposition and/or reorient one or both of the chucks104aand104bin response.

As an example, based on measurements received from the sensor assembly106, the control module112can determine that the chucks104aand104bare misaligned (e.g., the surfaces122aand122bare not parallel to each other). This misalignment might also result in a misalignment between the molds114aand114b.If the photocurable material is photocured when the molds114aand114bare misaligned, the resulting film may exhibit wrinkles, uneven thickness, or other physical distortions that might negatively affect the performance of the film in its intended application. Accordingly, the control module112can correct the misalignment (e.g., by repositioning the chuck104aand/or104bsuch that the surfaces122aand122bare substantially parallel to each other).

As an example, based on measurements received from the sensor assembly106, the control module112can determine that the chucks104aand104bare improperly spaced (e.g., the surfaces122aand122bare too close or too distant from each other). This improper spacing might also result in an incorrect spacing between the molds114aand114b.If the photocurable material is photocured when the molds114aand114bare improperly spaced, the resulting film may have dimensions that deviate from their intended dimensions, which might negatively affect the performance of the film in its intended application. Accordingly, the control module112can correct the spacing (e.g., by repositioning the chuck104aand/or104bsuch that the surfaces122aand122bare properly spaced from one another).

In some cases, the photocurable material can expand or contract during the photocuring process. If the position of the molds114aand114bare not adjusted during photocuring, the resulting film might be distorted (e.g., wrinkled, stretched, compressed, or otherwise distorted). To improve the quality of the film, the control module112can adjust the gap region150during the photocuring process (e.g., while the light source108is generating radiation and/or between sessions of radiation), such that the space between the molds114aand114bis adjusted to account for expansion and/or contraction. In some cases, the control module112can adjust the gap region continuously during the photocuring process. In some cases, the control module112can adjust the gap region intermittently during the photocuring process.

The manner in which the gap region150is adjusted can differ, depending on the implementation. In some cases, the amount and rate of material expansion or contraction can be experimentally determined based on various factors, such as the type of photocurable material used, the dimensions of the mold region, the type of radiation used, the strength of that radiation, and so forth. Accordingly, the control module112can be configured to expand and/or contract the gap region150at a particular empirically determined amount and rate, such that the material expansion and contraction is accounted for (e.g., by contracting the gap region when the material contracts, and expanding the gap region when the material expands). This can beneficial, for example, in reducing or eliminating distortions in the resulting film, thereby increasing its quality.

In some cases, the control module112can be configured to expand and/or contract the gap region150by moving one or both chucks relative to one another. In some cases, the gap region can be changed continuously over a period of time (e.g., continuously during the photocuring process), or intermittently over the period of time (e.g., intermittently during the photocuring process).

In some cases, the control module112can also be communicatively coupled to and control the vacuum system110and/or the light source108. For example, the control module112can be communicatively coupled to the vacuum system110, and can control the operation of the vacuum system110(e.g., to selectively apply vacuum pressure to reversibly secure the molds114aand114bto the chucks104aand104b,respectively). As another example, the control module112can be communicatively coupled to the light source108, and can control the operation of the light source108(e.g., to selectively apply radiation as a part of the photocuring process).

FIGS. 2A -2Fdepict an example photocuring process using the system100.

As shown inFIG. 2A, a mold114ais mounted to the chuck104a(e.g., through a vacuum pressure applied by the vacuum system110), and a corresponding mold114bis mounted to the chuck104b(e.g., through a vacuum pressure applied by the vacuum system110). A portion of photocurable material202is deposited into the mold114.

After the photocurable material202is deposited into the mold114, the system can perform a “pre-wetting” procedure. During the pre-wetting procedure, the chuck104aand the mold114aare positioned in proximity to the chuck104band the mold114b,such that such that the photocurable material202contained within the mold114acontacts the mold114b.Thus, the mold114bis “wetted” by the photocurable material202. Further, as the molds114aand1114bare drawn together, one mold (e.g., mold114b) is skewed relative to the other (e.g., mold114a). Due to this skewed orientation, air is less likely to be trapped between the mold114aand114bwhen the molds114aand114bare brought together, thereby eliminating or otherwise reducing the presence of bubbles or trapped air. The chucks104aand104bcan be subsequently adjusted such that they are parallel to one another, and the molds114aand114bare no longer skewed.

An example pre-wetting procedure is shown inFIGS. 2B-2D. As shown inFIG. 2B, the actuable stage102skews the chuck104arelative to the chuck104b(e.g., by rotating the chuck104a), such that the surface122aof the chuck104ais inclined with respect the surface122bof the chuck104bby an angle α. Accordingly, a mold surface206aof the mold114a(e.g., a top surface of the mold114acontacting photocurable material202) and a mold surface206bof the mold114b(e.g., the bottom surface of the mold114bthat will contact photocurable material202) are skewed relative one another.

For ease of illustration, a line204parallel of the surface122bis shown inFIG. 2B. In some cases, the angle a can be between approximately 1° and 10°.

As shown inFIG. 2C, the actuable stage102moves the chuck104aupward, such that the mold114aand mold114bare in proximity to one another. In this position, the mold114aand mold114bare oriented such that the photocurable material202contained within the mold114acontacts the mold114b.As described above, the relative position and/or orientation of the chucks104aand104b(and/or the relative position and/or orientation of the molds114aand114b) can be determined using a sensor assembly106and the control module112).

As shown inFIG. 2D, the actuable stage102repositions the chuck104arelative to the chuck104b,such that the surface122aof the chuck104ais substantially parallel to the surface122bof the chuck104b,and such that the mold surface206aof the mold114ais substantially parallel to the mold surface206bof the mold114b.In some cases, an angle between the two surfaces122aand122b,and/or the angle between the two mold surfaces206aand206b,can be less than 1°. In some cases, an angle of 2″ of arc or less (e.g., 10 μrad or less) may be particularly suitable for fabricating optical polymer films (e.g., 0.1 μm or thinner optical polymer films used in eyepieces).

As described above, by first skewing the chuck104arelative to the chuck104b,then positioning the chuck104asuch that such that the photocurable material202contained within the mold114acontacts the mold114b,and subsequently adjusting the chuck104aand104bsuch that they are parallel to each other, the occurrence of bubbles trapped within the molds114aand114bcan be eliminated or otherwise reduced. For instance, in the example depicted inFIG. 2C, bubbles between the molds114aand114bwill travel towards the left and exit the mold region rather than being trapped between the molds. Thus, the resulting film is less like to have distortions and other structural defects.

As shown inFIG. 2E, the light source108generates one or more wavelengths of radiation suitable for photocuring the photocurable material, and directs it to the photocurable material202in the mold region between the molds114aand114b.This hardens the photocurable material, resulting in a film.

As described above, the photocurable material can expand or contract during the photocuring process. To improve the quality of the film, the control module112can adjust the gap region during the photocuring process (e.g., while the light source108is generating radiation and/or between sessions of radiation), such that the space between the molds114aand114bis adjusted to account for expansion and/or contraction. For example, as shown inFIG. 2F, the mold114acan be moved nearer the mold114bduring photocuring to account for contractions in the photocurable material during the photocuring process. AlthoughFIG. 2Fdepicts mold114amoving near the mold114b,this need not be the case. In some implementations, the mold114bcan also move, either instead of or in addition to mold114a.

As noted above, the amount and rate of material expansion or contraction can be experimentally determined based on various factors, and the control module112can be configured to expand and/or contract the gap region at a particular empirically determined amount and rate, such that the material expansion and contraction is accounted for.

As an example, an experiment can be conducted by curing a specific photocurable material specific conditions. The specific conditions could pertain to, for instance, the particular amount of photocurable material used in the photocuring process, the particular shape and size of the molds used to cure the material, the spectral composition and/or the intensity of the radiation used to cure the material, the length of time in which the photocurable light is exposed to the radiation, and/or any other factors that could influence the photocuring process. As the photocurable material is cured, the photocurable material is monitored to determine any changes in volume. These measurements can be obtained at discrete time points throughout the photocuring process (e.g., once every second, once every minute, or according to some other pattern), and/or obtained continuously or substantially continuously over the course of the photocuring process, to determine the expansion and/or contraction of the photocurable material over time.

Subsequently, the control module112can be configured to expand and/or contract the gap region based on these time dependent measurements. For example, if the same photocurable material is to be cured using the same parameters as those in the experiment, the control module112can expand and/or contract the gap region in a time-dependent manner, such that the volume of the gap region is similar to that of the photocurable material.

Further, multiple experiments can be conducted using the same photocurable material and parameters (e.g., so that the expansion and/or contraction of the photocurable material can be estimated more accurately). Further, experiments can be conducted using a different photocurable material and/or different parameters (e.g., to estimate the expansion and/or contraction of different photocurable materials and/or under different conditions).

In the example process shown inFIG. 2A-E, the molds are skewed relative to one another by rotating one chuck relative to the other. However, this need not be the case. In some implementations, the molds can be skewed relative to one another by bending or bowing one or more of the molds.

As an example,FIGS. 3A -3Fdepict another example photocuring process using the system100.

As shown inFIG. 3A, a mold114ais mounted to the chuck104a(e.g., through a vacuum pressure applied by the vacuum system110), and a corresponding mold114bis mounted to the chuck104b(e.g., through a vacuum pressure applied by the vacuum system110). A portion of photocurable material202is deposited into the mold114.

After the photocurable material202is deposited into the mold114, the system can perform a “pre-wetting” procedure in which the mold114ais skewed relative to the mold114b(e.g., by bending or bowing the mold114a), and positioned in proximity to the mold114bsuch that such that the photocurable material202contained within the mold114acontacts the mold114b.The mold114aand114bcan subsequently be adjusted such that they are parallel to one another or unbent relative to one another. As above, this pre-wetting process can be useful, for example, as it can eliminate or otherwise reduce the presence of bubbles or trapped air when the molds114aand114bare brought together.

An example pre-wetting procedure is shown inFIGS. 3B-3D. As shown inFIG. 3B, the actuable stage102skews the mold114arelative to the mold114b(e.g., by bowing or bending the mold114a), such that the mold surface206aof the mold114ais not parallel with the mold surface206bof the mold114b.In some cases, the mold114acan be bent such that one portion of the mold114a(e.g., a center portion of surface206a) is higher than another portion of the mold114a(e.g., a peripheral portion of surface206a) by approximately 0.05 mm to 0.2 mm.

In some cases, the mold114acan be bowed or bent by selectively applying vacuum pressure along the periphery of the mold114a, while selectively applying positive air pressure along the center of the mold114a.As an example, as shown inFIG. 3B, the vacuum system110can apply vacuum pressure in vacuum channels along the periphery of the mold114(e.g., vacuum channels302a-band302e-f), while also applying positive air pressure in vacuum channels along the center of the mold114a(e.g., vacuum channels302cand302d). As a result, the periphery of the mold114ais secured to the chuck104avia a suction force, while the center of the mold114ais forced away from the chuck104adue to positive air pressure.

In some cases, the mold114acan be bowed or bent using mechanical mechanisms. For example, in some cases, the periphery of the mold114acan be gripped by a bracket or mount, and the center of the mold114acan be pushed upward by a riser, actuator, lever, or other mechanism. In some cases, the vacuum system110can be used in conjunction with mechanical mechanisms to bow or bend the mold114a.

As shown inFIG. 3C, the actuable stage102moves the chuck104aupward, such that the mold114aand mold114bare in proximity to one another. In this position, the mold114aand mold114bare oriented such that the photocurable material202contained within the mold114acontacts the mold114b.As described above, the relative position and/or orientation of the chucks104aand104b(and/or the relative position and/or orientation of the molds114aand114b) can be determined using a sensor assembly106and the control module112).

As shown inFIG. 3D, the actuable stage102deskews the mold114arelative to the mold114b(e.g., unbows or unbends the mold114a), such that the surface206aof the mold114ais substantially parallel to the surface206bof the mold114b.In some cases, an angle between the two surfaces206aand206bcan less than 1°. In some cases, the flatness of the surfaces206aand206bcan be such that each surface varies from an ideal flat surface by 100 nm or less (e.g., between 20 nm to 100 nm, or less). In some cases, an angle of 2″ of arc or less (e.g., 10 μrad or less) and/or a variation in flatness of 100 nm or less may be particularly suitable for fabricating thin optical polymer films (e.g., 0.1 μm or thinner optical polymer films used in eyepieces).

In some cases, the mold114acan be unbowed or unbent by applying vacuum pressure and/or discontinuing the application of positive air pressure along some or all of the mold114a.As an example, as shown inFIG. 3D, the vacuum system110can apply vacuum pressure in vacuum channels302a-f.As a result, the mold114ais secured to the chuck104avia a suction force, and the mold114ais unbent.

In some cases, the mold114acan be unbowed or unbent using mechanical mechanisms. For example, in some cases, the periphery of the mold114acan be gripped by a bracket or mount, and the center of the mold114acan be released or pulled downward by a riser, actuator, lever, or other mechanism. In some cases, the vacuum system110can be used in conjunction with mechanical mechanisms to unbow or unbend the mold114a.

As described above, by first skewing the mold114arelative to the mold114b,then positioning the mold114asuch that such that the photocurable material202contained within the mold114acontacts the mold114b,and subsequently adjusting the mold114aand114asuch that they are parallel to each other, the occurrence of bubbles trapped within the molds114aand114bcan be eliminated or otherwise reduced. For instance, in the example depicted inFIG. 3C, bubbles between the molds114aand114bwill travel towards the periphery of the molds and exit the mold region rather than being trapped between the molds. Thus, the resulting film is less like to have distortions and other structural defects.

As shown inFIG. 3E, the light source108generates one or more wavelengths of radiation suitable for photocuring the photocurable material, and directs it to the photocurable material202in the mold region between the molds114aand114b.This hardens the photocurable material, resulting in a film.

As described above, the photocurable material can expand or contract during the photocuring process. To improve the quality of the film, the control module112can adjust the gap region during the photocuring process (e.g., while the light source108is generating radiation and/or between sessions of radiation), such that the space between the molds114aand114bis adjusted to account for expansion and/or contraction. For example, as shown inFIG. 3F, the mold114acan be moved nearer the mold114bduring photocuring to account for contractions in the photocurable material during the photocuring process. As noted above, the amount and rate of material expansion or contraction can be experimentally determined based on various factors, and the control module112can be configured to expand and/or contract the gap region at a particular empirically determined amount and rate, such that the material expansion and contraction is accounted for.

In some cases, a mold can be both rotated and/or bowed as a part of a pre-wetting procedure. Further, althoughFIGS. 2A-Fand3A-F show a single mold114abeing skewed relative to mold114b(e.g., rotated, bowed, or bent relative to the mold114b), in practice, mold114balso can be skewed (e.g., rotated, bowed, or bent), either instead of or in addition to the mold114a.

An example film400is shown inFIG. 4A. In this example, the film400was produced without a pre-wetting process, and without controlling the gap region between molds (either before or during the curing processing). As shown inFIG. 4A, the film400is distorted, and includes defects such as wrinkles and uneven thickness (e.g., wrinkles402, visible as a distorted reflection).

Another example film450is shown inFIG. 4B. In this example, the film450was produced with a pre-wetting process, and by controlling the gap region between molds (both before or during the curing processing). As shown inFIG. 4B, the film450is substantially less distorted than film400, exhibits fewer or substantially no wrinkles, and is significantly more even in thickness. Accordingly, the film450may be more suitable for use in variation-sensitive applications (e.g., as a part of eyepieces in an optical imaging sy stem).

In the example systems shown inFIGS. 1, 2A-2F, and 3A-F, each system provides a single “station” for producing polymer film. For instance, each system can be used to produce a single polymer film at a time. Upon completion of a polymer film, the polymer film can be collected from the system, and the system can begin production of a new polymer film.

However, in practice, a system need not be limited to a single station (e.g., limited to producing a single polymer film at a time). For example, in some cases, a system can provide multiple stations, each of which can be used to produce a respective polymer film. Further, each of the stations can be operated in conjunction. This can be beneficial, for example, as it enables a system to produce polymer film more quickly and/or efficiently (e.g., by simultaneously producing multiple polymer films in a parallelized manner).

As an illustrative example, a system500is shown inFIGS. 5A(top view) and5B (side view). The system500includes a rotatable platform502having multiple stations504a-gcircumferentially distributed about the platform502. Each station504a-gcan be operated simultaneously to produce a respective polymer film. In some cases, each station504a-gcan include some or all of the components of the system100shown inFIGS. 1, 2A-2F, and 3A-F. For ease of illustration, components of each station504a-ghave been omitted inFIGS. 5A and 5B.

In some cases, each station can include one or more actuable stages for adjusting the relative positions or orientations of a pair of chucks. For example, as shown inFIG. 5B, a station504acan include an actuable stage506ato position a chuck508arelative to a chuck508b.As another example, the station504acan include an actuable stage506bto position the chuck508brelative to the chuck508a.

In some cases, one or both of the actuable stages506aand506bcan be similar to the actuable stage102described above. For example, in some cases, the actuable stages506aand506bcan manipulate the chucks508aand508baccording to one or more degrees of freedom. In some cases, one actuable stage can be used to adjust a chuck according to one or more particular degrees of freedom, while another actuable stage can be used to adjust another chuck according to one or more other degrees of freedom. As an example, the actuable stage506acan be used to translate the chuck508ain the x and y directions, while the actuable stage506bcan be used to translate the chuck508bin the z direction and rotate the chuck508babout the x and y axes (e.g., to tilt the chuck508b). In practice, other combinations are also possible, depend on the implementation. Similarly, each of the other stations504b-galso can include one or more actuable stages to adjust the relative positions or orientations of its respective pair of chucks.

Further, each station can include a heating element and/or a cooling element to control the temperature of materials (e.g., photocurable materials) at that station. For instance, as shown inFIG. 5B, the station504acan include a heating element510to apply heat to the chuck508a,and a cooling element512to cool the chuck508a.This can be useful, for example, in facilitating the photocuring process. For example, heat can be applied to a photocurable material to promote annealing. Example heating elements include flexible electric strip heaters, and thermoelectric coolers. As another example, the photocurable material can be cooled after annealing, such that it can be more easily collected. Example cooling elements include thermoelectric coolers and liquid-based coolers. Other temperature-dependent processes can also be performed. Similarly, each of the other stations504b-galso can include one or more heating elements and/or cooling elements.

Further, the system500can rotate the rotatable platform502to reposition the stations504a-g.For instance, the system500can include can include an axle514positioned along a central axis516of the rotatable platform502. The system500can rotate the axle514(e.g., using a motor module518) to rotate the platform502and reposition the stations504a-g.

The rotatable platform502can provide several benefits. For example, as described with respect toFIGS. 2A-2F and 3A-F, a polymer film can produced by performing several different steps in a sequence. Further, each step can be performed using particular components of the system. The rotatable platform502enables certain components of the system to be used across several different stations504a-g,thereby reducing the complexity and/or cost of implementing, operation, and maintaining the system. For instance, a particular component can be positioned next to the rotatable platform502at a particular position, and the rotatable platform502can rotate such that a particular station is positioned in proximity to that component. Once the station is properly positioned, the component can be used to perform a particular step of the production process. After completion of the step, the rotatable platform502can be rotated such that a different station is positioned in proximity to the component, and the component can be used to repeat the step on the new station. Further, this process can be repeated one or more times across one or more additional stations. In this manner, one or more common components can be used to perform particular steps across multiple different stations.

As an example, as shown inFIG. 5A, the system500can include a dispensing module520ain proximity to Position1of the rotatable platform502(currently occupied by the station504a), a curing module520bin proximity to Position2(currently occupied by the station504b), and a collection module520cin proximity to Position7(currently occupied by the station504g).

During operation of the system500, the dispensing module520adispenses materials into the station at Position1. For instance, the dispensing module520acan include one or more pumps, pipettes, or other dispensing mechanisms for depositing photocurable material into a station's mold.

After the photocurable material is dispensed, the rotatable platform502is rotated (e.g., counter-clockwise) such that the station at Position1is repositioned at Position2. Once the station is repositioned, the curing module520bcures the photocurable material. For instance, the curing module520bcan include one or more light sources configured to generate one or more wavelengths of radiation suitable for photocuring photocurable material. The photocurable material in the station at Position2can be exposed to this radiation to facilitate curing into a polymer film.

After the photocurable material is dispensed, the rotatable platform502is rotated (e.g., counter-clockwise) such that the station at Position2is repositioned at Position3. When a station is in this position, the photocurable material can be subjected to temperature-dependent processes. For instance, the photocurable material can be heated (e.g., using a heating element510) to promote annealing.

As the rotatable platform502continues to rotate, the station is subsequently repositioned to Position4, then to Position5, and then to Position6. At each of these positions, the photocurable material can continue to be subjected to temperature-dependent processes. For example, the photocurable material can be additionally heated (e.g., using the heating element510). As another example, the photocurable material can be cooled (e.g., using the cooling element512) to end the annealing process and/or facilitate collection of the polymer film.

As the rotatable platform502continues to rotate, the station is subsequently repositioned to Position7. Once the station is repositioned, the collection module520ccollects the polymer film from the station. For instance, the collection module520ccan include one or more robotic manipulation mechanisms configured to separate the polymer film from the mold, and extract the polymer film from the station.

As described above, each of the stations can be operated in conjunction to simultaneously produce multiple polymer films in a parallelized manner. For example, each of the stations504a-gcan be sequentially rotated across the Positions1-7to perform each of the steps for producing polymer film in a sequence. Further, although seven stations504a-gare shown inFIG. 5A, this is merely an illustrative example. In practice, there are can any number of stations (e.g., one, two, three, four, five, etc.).

The system500can also have a control module550to control the operation of the system500. For example, the control module550can be communicatively coupled to the motor module518to control the rotation of the rotatable platform502, the dispensing module520ato control the dispensing of materials, the curing module520bto control the application of radiation, and/or the collection module520cto control the collection of polymer films. The control module550can also be communicatively coupled to one or more the stations504a-gto control their operations (e.g., to control the actuable stages, the heating and cooling elements, etc.).

In the example shown inFIG. 5B, each station includes a respective actuable stage dedicated to manipulating the lower chuck at that station. For example, as shown inFIG. 5B, the station504acan include an actuable stage506afor specifically manipulating the lower chuck508a.However, this need not be the case. In some cases, a single actuable stage can be used to manipulate lower chucks across multiple different stations. For example, an actuable stage can be positioned at a particular position with respect to the rotatable platform502(e.g., one of Position1-7), and can be configured to manipulate the lower chucks of whichever station is positioned at that particular position. As the rotatable platform502is rotated, the actuable stage can manipulate the lower chucks of different stations as they move into through that position. In this manner, a single actuable stage can be used to manipulate the lower chucks across multiple different stations, without requiring that each station include a separate actuable stage.

As an example, as shown inFIG. 6, a single actuable stage602can be used to manipulate the lower chucks of multiple different stations. In this example, the rotatable platform502defines an aperture604at each of the positions of the stations. Further, at each position, a lower chuck606is positioned over the aperture604. The dimensions of the lower chuck606are larger than those of the aperture604(e.g., larger diameter, width, and/or length), such that the lower chuck606does not fall through the aperture604. Once a particular station is positioned over the actuable stage602, the actuable stage602can be moved upward through the aperture604to push the lower chuck606in an upward direction (e.g., to translate the lower chuck606along the z direction). Further, the actuable stage602can be laterally to translate the lower chuck606across one or more additional directions (e.g., to translate the lower chuck606along the x and/or y directions). The actuable stage602can be retracted, and the rotatable platform502can be rotated to position another lower chuck over the actuable stage602.

In some cases, a system can include multiple different rotatable platforms to facilitate the production of polymer films. As an example,FIG. 7shows a system700for simultaneously producing multiple polymer films. The system700can be similar to the system500shown inFIG. 5A, and can include one or more of the components shown inFIG. 5A(for ease of illustration, various components are omitted, such as the dispensing module, curing module, control module, etc.). However, in this example, the system includes two rotatable platforms702aand702b.The rotatable platforms702aand702bare interconnected by two conveyors704aand704b(e.g., conveyor belts, rollers, tracks, etc.). Further, several stations706a-rare positioned on the rotatable platforms702aand702band/or the conveyors704aand704b.During operation of the system700, the rotatable platforms702aand702brotate (e.g., counter-clockwise) to reposition each of the stations706a-rwith respect to one or more other components of the system (e.g., a collection module708, a dispensing module, a curing module, etc.). Further, stations706a-rcan be transferred between the rotatable platforms702aand702busing the conveyors704aand704b.This can be beneficial, for example, as it enables the system700to simultaneously handle a larger number of stations.

In some cases, the system700can include heating regions and/or cooling regions to control the temperature of materials (e.g., photocurable materials) at one or more stations. As an example, the system700can include a heating region710ato apply heat to stations as they pass through the heating region710a(e.g., to promote annealing). Example heating regions include chambers or areas heated by ultraviolent and/or infrared curing lamps, or other heating elements. As another example, the system700can include a cooling region710bto cool the stations as they pass through the cooling region710b(e.g., so that polymer films can be more easily collected). Example cooling regions include chambers or areas cooled by force air cooling mechanisms or other cooling elements. Other temperature-dependent processes can also be performed using one or more heating regions and/or cooling regions.

Although several stations706a-rare shown inFIG. 7, this is merely an illustrative example. In practice, there are can any number of stations (e.g., one, two, three, four, five, etc.). Further, although two rotatable platforms702aand702band two conveyors704aand704bare shown inFIG. 7, this is also merely an illustrative example. In practice, there are can any number of rotatable platforms and/or conveyors (e.g., one, two, three, four, five, etc.).

An example process800for casting a polymer film by photocuring a photocurable material is shown inFIG. 8.

A photocurable material is dispensed onto a first surface of a first mold (step810).

After a photocurable material is dispensed onto the first surface of the first mold, the first mold and a second mold are positioned such that the first surface and a second surface of the second mold are separated by a gap (step820).

After the first and second molds are positioned, measurement information is obtained regarding the first and second molds (step830). The measurement information can include information indicative of a distance between the first and second molds at each of at least three locations and/or a pressure at each of at least three locations between the first and second molds during use of the system.

In some cases, the measurement information can be obtained using one or more capacitive sensors. In some cases, the measurement information can be obtained using three or more capacitive sensors.

In some cases, obtaining the measurement information can include determining, using one or more pressure sensors, a pressure applied to each of one or more mechanical spacers disposed between the first and second molds and/or along a periphery of the first and second molds. In some cases, obtaining the measurement information can include determining, using three or more pressure sensors, a pressure applied to each of three or more mechanical spacers disposed between the first and second molds and/or along a periphery of the first and second molds.

The gap between the first and second molds surfaces is controlled based on the measurement information (step840).

One or more wavelengths of radiation suitable for photocuring the photocurable material are directed to the photocurable material (step850). In some cases, the one or more wavelengths of the radiation can include at least one of an ultraviolet wavelength or a visible wavelength.

In some cases, the process800can also include arranging the first mold relative to a second mold in a first configuration. In the first configuration, the first surface of the first mold faces the second surface of the second mold and is skewed with respect to the second surface, and the photocurable material contacts the second surface of second mold.

In some cases, in the first configuration, an angular displacement between the first surface of first mold and the second surface of second mold can be between approximately 1° and 10°.

In some cases, in the first configuration, the second surface of second mold can be bowed with respect to the first surface. For example, one portion of one surface (e.g., a center portion of that surface) can differ in height from another portion of that surface (e.g., a peripheral portion of that surface) by approximately 0.05 mm to 0.2 mm.

The second surface of the second mold can be bowed by applying pressure to a central portion of the second mold.

In some cases, in the first configuration, an angular displacement between the first surface of first mold and the second surface of second mold can be between approximately 1° and 10°, and the second surface of second mold can be bowed with respect to the first surface.

In some cases, subsequent to arranging the first mold and the second mold in the first configuration, the first mold and the second mold can be arranged in a second configuration. In the second configuration, the first surface and the second surface can be substantially parallel. In some cases, in the second configuration, an angular displacement between the first surface and the second can be less than 1°0. In some cases, an angle of 2″ of arc or less (e.g., 10 μrad or less) and/or a variation in flatness of 100 nm or less may be particularly suitable for fabricating optical polymer films (e.g., 0.1 μm or thinner optical polymer films used in eyepieces).

In some cases, subsequent to arranging the first mold and the second mold in the second configuration, one or more wavelengths of radiation suitable for photocuring the photocurable material can be directed to the photocurable material. Further, while directing the radiation to the photocurable material, the distance between the first and second molds can be increased or decreased over a period of time (e.g., by moving one or both chucks relative to one another). In some cases, the distance between the first and second molds can be decreased or increased continuously over the period of time (e.g., continuously during the photocuring process). In some cases, the distance between the first and second molds can be decreased or increased intermittently over the period of time (e.g., intermittently during the photocuring process). In some cases, a position of at least one of the first mold or the second mold can be adjusted using a rotatable platform.

Some implementations of subject matter and operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. For example, in some implementations, the control modules112and/or550can be implemented using digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations of one or more of them. In another example, the processes shown inFIGS. 2A-F,3A-F,5A-E,6,7and8can be implemented, at least in part, using digital electronic circuitry, or in computer software, firmware, or hardware, or in combinations of one or more of them.

Some implementations described in this specification can be implemented as one or more groups or modules of digital electronic circuitry, computer software, firmware, or hardware, or in combinations of one or more of them. Although different modules can be used, each module need not be distinct, and multiple modules can be implemented on the same digital electronic circuitry, computer software, firmware, or hardware, or combination thereof.

Some implementations described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on computer storage medium for execution by, or to control the operation of, data processing apparatus. A computer storage medium can be, or can be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

FIG. 9shows an example computer system900that includes a processor910, a memory920, a storage device930and an input/output device940. Each of the components910,920,930and940can be interconnected, for example, by a system bus950. The processor910is capable of processing instructions for execution within the system900. In some implementations, the processor910is a single-threaded processor, a multi-threaded processor, or another type of processor. The processor910is capable of processing instructions stored in the memory920or on the storage device930. The memory920and the storage device930can store information within the system900.

The input/output device940provides input/output operations for the system900. In some implementations, the input/output device940can include one or more of a network interface devices, e.g., an Ethernet card, a serial communication device, e.g., an RS-232 port, and/or a wireless interface device, e.g., an 802.11 card, a 3G wireless modem, a 4G wireless modem, etc. In some implementations, the input/output device can include driver devices configured to receive input data and send output data to other input/output devices, e.g., keyboard, printer and display devices960. In some implementations, mobile computing devices, mobile communication devices, and other devices can be used.