Patent Description:
Analog NV systems function by receiving low levels of light and intensifying the received light using an image intensifier. The image intensifier has a photocathode that emits electrons in response to incident photons. The emitted electrons are accelerated through a vacuum tube and directed towards a microchannel plate that amplifies the signal by multiplying the number of electrons. The multiplied electrons then strike a phosphor screen, and, via the phenomenon of luminescence, the phosphor screen emits photons in response to radiant energy (e.g., the electrons). The luminescent light from the phosphor screen is coupled through a series of optics to the user. For example, the luminescent light may be coupled through an inverting fiber optic to an eyepiece where the user can view the illuminated phosphor screen, thus allowing the user to see the objects.

Analog NV systems can include an overlay display that transmits a direct-view, intensified image through the overlay display and emits display light representing a display image from the overlay display to thereby generate a combined image with the display image superimposed over the direct-view, intensified image. The Overlay display can be used to convey various information to the user, such as temperatures, distances, indicators marking objects, situational awareness messages, messages from other users, etc..

Analog NV systems, however, are not optimized for use with an overlay display, which presents challenges if the intensifier module from a legacy analog NV system is being upgraded to an intensifier module that includes an overlay display. For example, many legacy systems use an intensifier module having a curved exit surface to reduce the number of lens elements in an eyepiece. Such a configuration is beneficial because it reduces the weight of the legacy system and thereby reduces the torque on the user's neck, among other advantages. The curved exit surface poses a challenge for adding an overlay display because fabrication on a curved surface is difficult (e.g., semiconductor fabrication processes are typically performed on flat, planar surfaces, which are advantageous for photolithography).

Other solutions attempt to address the curved exit surface problem by introducing additional optical elements (e.g., one or more additional lenses) that would allow the overlay display to be fabricated on a flat surface. However, these additional optical elements must be squeezed into the limited space allotted for the intensifier module. In legacy systems, the space allotted for the intensifier module is already severely constrained, and shortening the intensifier module to accommodate both the overlay display and the additional optical element(s) presents a significant design challenge for the intensifier module. Accordingly, an improved configuration of an intensifier module with overlay display is desired for backwards compatibility with legacy analog NV systems.

Independently of making intensifier modules backwards compatible with legacy systems, the improved configuration of the intensifier module can be advantageous in its own right. For example, the improved configuration may have reduced mass and a reduced moment of inertia relative to prior intensifier module configurations. Reducing the moment of inertia results in less torque on a user's neck, which reduces neck strain and fatigue.

From the prior art <CIT> is known which discloses an image display apparatus using a diffraction lens. Said image display apparatus includes a display panel for displaying an image and a display panel for dividing the image of the display panel into a plurality of viewports. From the plurality of viewports, the image is recognized as a three-dimensional image using the optical principles of the Fresnel zone plate and a diffraction lens. From <CIT> an enhanced vision system is disclosed which includes a first optic subsystem and a transparent photodetector subsystem. The first optic subsystem includes a passive device such as simple or compound lenses, active devices such as low-light enhancing image intensifiers, or a combination of passive and active devices. The transparent photodetector subsystem receives the visible image exiting the first optic subsystem and converts a portion of the electromagnetic energy in the visible image to a signal communicated to image analysis circuitry. On a real-time or near real-time basis, the image analysis circuitry detects and identifies structures, objects, and/or individuals in the visible image. From <CIT> a hybrid imaging system is known. Said system incorporates conventional optical elements and metasurface elements. The document further discloses a system and a method for integrating apertures with metasurface elements and refractive optics. From <CIT> a multilayer optical element for controlling light is disclosed. The element comprises a plurality of layers arranged along an optical axis, each layer having a plurality of nanostructures. Size and spacing between the nanostructures is selected to provide a resonant response to an optical field at different wavelengths for different layers. From "<NPL>, a metasurface application to realize a compact near-eye display system for augmented reality with a wide field of view is disclosed.

One embodiment illustrated herein includes an optical device that includes a semiconductor chip having a first surface that receives direct-view light and transmits the direct-view light through the transparent regions of the optical device. The optical device further includes a plurality of electro-optical circuits formed on the semiconductor chip. The plurality of electro-optical circuits includes light emitters configured to output display light, and the transparent regions being arranged between respective light emitters of the light emitters. The plurality of electro-optical circuits also includes a planar, diffractive lens arranged to induce a phase curvature on the display light and to induce a same phase curvature on the direct-view light as on the display light.

Another embodiment illustrated herein is a method of processing light in an intensifier module. The method includes receiving, at an intensifier, light from an environment and generating intensified light representing an intensified image of the environment, the intensified light having a first phase curvature upon exiting the intensifier. The method further includes transmitting the intensified light through a transparent overlay display, and emitting display light from the transparent overlay display to superimpose a display image over the intensified image, the display light having a second phase curvature that matches the first phase curvature of the intensified light. The method further includes inducing, using a planar, diffractive lens, a third phase curvature on the display light and the intensified light transmitting the luminescent light within the first range of wavelengths through the one or more detectors. The method further includes transmitting the display light and the intensified light with the third phase curvature to an eye piece comprising lenses.

As discussed above, an analog night vision (NV) system can include both an intensified image and an overlay image, such as the image from an overlay/heads-up display. This combined image can be generated using an intensifier module having an integrated overlay display. Legacy analog NV systems can be provided with intensifier modules that do not include the overlay display functionality, and, therefore, it would be advantageous to upgrade these legacy NV systems by replacing the legacy intensifier modules with a higher-functionality intensifier module that does include the overlay display functionality. For example, in a legacy system that has an intensifier module without an overlay display, the legacy intensifier module may be removed and replaced with an intensifier module having an integrated overlay display to provide the improved functionality of displaying information (e.g., text, pictograms, or other symbolic information) using an overlay display.

However, a challenge for such a replacement is that the intensifier module in the legacy system may have a curved exit surface. That is, the intensified image exiting the intensifier module may have a curved focal plane (e.g., a curved phase front of the exiting light). Having a curved focal plane at the exit of the intensifier module is advantageous because so doing may reduce the number of lens elements in the eyepiece of the analog NV system. For example, the last optical element in the legacy intensifier module may be a fiberoptic inverting element. By grinding and polishing the exit surface of the fiberoptic inverting element this element acts as a lens, causing a phase curvature of the exiting light thereby reducing by one the number of lenses in the eyepiece of the analog NV system.

Although it is straightforward to fabricate a curved surface on a fiberoptic inverting element, fabricating an overlay display on a curved surface presents several challenges. Accordingly, the overlay display that is integrated with an intensifier module will typically be flat or planar. For example, the overlay display may be fabricated using a crystalline based circuit (e.g., a circuit fabricated on a single crystal silicon wafer) for driving the respective pixels of the overlay display. The lithographic processes used to fabricate the driving circuit and the overlay display are less challenging on a non-curved substrate. Additionally, the overlay display may be flat because it is fabricated using a flat cover glass.

Combining a flat overlay display with an intensifier module having a curved exit surface is not desirable because the display image generated by the overlay display will have a different focal point than the intensified image generated by the intensifier module. For example, the intensified light from the intensifier module (e.g., from the curved exit surface of the fiberoptic inverting element) will have a different phase curvature than the display light generated by the flat overlay display. Thus, if the eyepiece is optimized/focused to make the intensified image clear, the display image will be out of focus. Alternatively, if the display image is in focus, the intensified image will be out of focus.

Several approaches may be used to enable the integration of a flat overlay display with an intensifier module. First, the fiberoptic inverting element can be fabricated with a flat, rather than curved, exit face. Thus, the phase curvature will be flat both for the intensified light exiting the fiberoptic inverting element and for the display light emitted from the overlay display. Because the phase curvature is the same for both the intensified light and the display light, the same setting for the eye piece of the NV system will cause both the intensified light and the display light to be in focus.

However, if the eye piece of the NV system is specified to work for incoming light having a non-flat phase curvature, then the light exiting the overlay display can pass through an optical element (e.g., a lens) before entering the eyepiece, and this optical element/lens can apply the specified non-flat phase curvature. That is, the specified non-flat phase curvature can be imposed on the combination of the intensified light and the display light, after the combined light exits the overlay display and before the combined light enters the eye piece. For example, a refractive lens may be arranged between the overlay display and the eyepiece. Alternatively, a planar optical element (e.g., a diffractive lens, such as a metamaterial diffractive lens) is arranged between the overlay display and the eyepiece to provide the specified focal plane curvature.

Alternatively, the eyepiece can be modified to accommodate the combined light entering the eyepiece having a flat phase curvature. For example, a refractive lens may be added to the entrance of the eyepiece.

Returningto the above solution of arranging a planar optical element in the intensifier module after the overlay display, there are several advantages of using a planar optical element, as opposed to a refractive lens. First, the planar optical element can be very thin, and therefore does not adversely affect the diopter range of the eye piece. Second, because the planar optical element can be thin, it does not consume the space needed for other elements in the intensifier module. Third, the planar optical element is flat like the overlay display, making it straightforward to integrate the planar optical element with the overlay display. Additionally, the planar optical element may have little mass, thereby reducing the torque on a user's neck. Fourth, by imposing the desired focal plane curvature within the volume allotted for an intensifier module, the planar optical element makes the integrated intensifier module backward compatible with legacy analog NV systems that are designed to have a curved focal plane for light exiting the intensifier module. Indeed, in some embodiments, an NV system can be upgraded by removing the legacy intensifier module and replacing it with an integrated intensifier module.

Referring now to <FIG>, a non-limiting example of a NV system is illustrated. In particular, <FIG> illustrate a PVS - <NUM> NV system <NUM>. In the example illustrated, the NV system <NUM> includes a housing <NUM>. As will be illustrated in more detail below in other figures, the housing <NUM> houses an image intensifier module <NUM> in an intensifier housing <NUM>. The NV system <NUM> further includes an objective <NUM> which receives light reflected and/or generated in an environment. The objective <NUM> includes optics such as lenses, waveguides, and/or other optical components for receiving and transmitting light to the image intensifier module <NUM>. The NV system <NUM> further includes an eyepiece <NUM>. The eyepiece <NUM> includes optics for focusing images created by the NV system <NUM> into the eye of the user.

<FIG> illustrate the image intensifier module <NUM>, according to one example. The image intensifier module <NUM> includes an image intensifier <NUM> without an overlay display. For example, the illustrated intensifier module <NUM> in <FIG> may be the legacy image intensifier that is replaced when upgrading to an improved image intensifier having the overlay display functionality. The light from the image intensifier module <NUM> is captured by the eyepiece <NUM> and directed to the user.

The image intensifier module <NUM> receives the input light <NUM>, which has been transmitted through the objective <NUM> to the image intensifier module <NUM>. The input light <NUM> may be, for example, dim light from a nighttime environment that would be challenging if not impossible to see unaided with the naked eye.

The objective directs the input light <NUM> into the image intensifier <NUM>. The image intensifier <NUM> may include functionality for amplifying the received image so that the image that can be viewed by the user. In the illustrated embodiment, this amplification is accomplished using a photocathode <NUM>, a microchannel plate <NUM>, and a phosphor screen <NUM>. The photocathode <NUM> absorbs incident photons and outputs electrons in response. The electrons may pass through an optional ion barrier film <NUM>. Electrons from the photocathode <NUM> are transmitted to the microchannel plate <NUM>, which multiplies the number of electrons. The multiplied electrons then strike a phosphor screen <NUM>, which absorbs the energy from electrons generating photons in response. The phosphor screen <NUM> converts the radiant energy of the multiplied electrons to luminescent light via the phenomenon of luminescence. Accordingly, the phosphor screen <NUM> glows due to electrons from the microchannel plate <NUM> striking the phosphor screen <NUM>, creating an intensified image that represents the image of the input light <NUM>. A fiber-optic element <NUM> carries the intensified light <NUM> (with the intensified image) to the eyepiece <NUM> of the NV system where it is output to the user.

The size of the intensifier module <NUM> is restricted by the dimensions of the intensifier housing <NUM>. As shown in <FIG>, in certain embodiments, the respective elements of the intensifier module <NUM> are packaged in a cylinder that can be secured in the intensifier housing <NUM>. To add additional elements and functionality to the intensifier module <NUM>, some of the elements in the intensifier module <NUM> (as discussed in more detail below) can be shortened to make room for the additional elements without increasing the overall size of the cylindrical packaging, thereby allowing the intensifier module <NUM> with improved functionality to fit within the dimensions of the intensifier housing <NUM>.

Further modifications may be used to ensure that intensifier module <NUM> with improved functionality matches the specifications of a legacy intensifier module <NUM> that is being replaced. For example, a legacy intensifier module <NUM> may use a spherically curved focal plane that is implemented in image intensifier tubes via a radius curvature on the fiberoptic inverting element at the exit surface. For example, the radius curvature on the fiberoptic inverting element may be provided via grinding and polishing the fiberoptic inverting element. This curved focal plane allows for a lens to be omitted from the eyepiece assembly for reduced size and weight. To replace this legacy intensifier module with a replacement intensifier module <NUM> having improved functionality, it is preferably that the replacement intensifier module <NUM> generates light having the same curved focal plane, such that the replacement intensifier module <NUM> can be used without modification of the eyepiece <NUM>. For example, if the replacement intensifier module <NUM> has a flat focal plane rather than the same curved focal plane, then the diopter range of the NV system might be adversely affected.

<FIG> illustrate an analog NV system having an intensifier module <NUM> with an overlay display <NUM>, according to one embodiment. The fiber optic element <NUM> has a flat exit face, and the overlay display <NUM> is flat. A refractive lens <NUM> is provided in the intensifier housing to provide a curved focal plane. Thus, combination of the refractive lens <NUM> with the intensifier module <NUM> illustrated in <FIG> may replace the intensifier module <NUM> illustrated in <FIG>. To avoid redundant descriptions, elements in <FIG> are not repeated for those elements that function the same in <FIG> as in <FIG>.

The overlay display <NUM> generates display light <NUM>, which is superimposed with the intensified light <NUM>. For example, the overlay display <NUM> may include functionality for displaying information to a user. Such information may include graphical content, including text, images, superimposed thermal image data and the like. <FIG>, which is discussed below, illustrates an example of an image in which a micro display <NUM> superimposed text, symbols, and other information over an intensified image that includes trees and clouds. Additional details regarding certain embodiments of the NV system <NUM> and the overlay display <NUM> are provided in <CIT>, titled "Backside Etch Process for Transparent Silicon Oxide Technology".

The refractive lens <NUM> may be a meniscus lens, for example. The refractive lens <NUM> may be fabricated using a material having a high index of refraction. lens (meniscus or similar) can do the curvature correction. The refractive lens <NUM> may apply a same phase curvature to the intensified light <NUM> as would be applied by the curved exit face of the fiber optic element <NUM> illustrated in <FIG>, for example. In certain embodiments, the refractive lens <NUM> may extend beyond the end of the tube volume housing (i.e., beyond the intensifier housing <NUM>, limiting the diopter range of the eyepiece <NUM>. In certain embodiments, the refractive lens <NUM> occupies some space in the intensifier housing <NUM>, and consequently, other elements in the intensifier module <NUM> are made more compact to allow for the occupied by the refractive lens <NUM>. For example, the fiber optic element <NUM> may be an inverter and can be made shorter by using a faster twist pitch for the fiber optic waveguides performing the inversion. Further, in certain embodiments, the power supply (not shown) may be shortened to accommodate for the space occupied by the refractive lens <NUM>.

<FIG> illustrate an analog NV system having an intensifier module <NUM> with an overlay display <NUM> and a planar lens <NUM>, according to one embodiment. Again, redundant descriptions are omitted. The fiber optic element <NUM> has a flat exit face, and the overlay display <NUM> and planar lens <NUM> are respectively fabricated on flat substrates. The planar lens <NUM> induces a phase curvature on the display light <NUM> and the intensified light <NUM>. The planar lens <NUM> performs a similar function as the refractive lens <NUM>, except the planar lens <NUM> can be substantially thinner than the refractive lens <NUM>. Consequently, the size of the other elements in the intensifier module <NUM> need not be decreased to allow for the space occupied by the planar lens <NUM> because the space occupied by the planar lens <NUM> is minimal. For example, the planar lens <NUM> may prevent violating the diopter range controls, and the planar lens <NUM> may not require the power supply volume and position to be altered.

In certain embodiments, the planar lens <NUM> induces a spherical phase curvature. The planar lens <NUM> may induces a positive phase curvature that causes the light to converge as it propagates from the planar lens <NUM> towards the eye piece <NUM>.

Preferably, the planar lens <NUM> will be a metamaterial diffractive lens. <FIG> illustrates a refractive lens and several examples of planar, diffractive lenses. The planar lenses are diffractive optical elements and are illustrated by several examples including, e.g., a binary amplitude plate, a two-material binary phase plate, a single-material binary phase plate, a multizone phase plate, a kinoform/Fresnel lens, and a metamaterial lens. The binary amplitude plate alternates opaque and transparent regions to achieve a lensing effect. The binary phase plates achieve lensing by alternating regions having a relative π-phase shift. The multi-zone phase plate achieves lensing using the same principle as the binary phase plates, except there are more than two types of regions and the discrete phase shifts between zones is more finely divided (e.g., with four zones the relative phase shift will be π/<NUM>). The kinoform/Fresnel lens applies a continuum of phase zones with discrete transitions when the phase reaches 2π.

The metamaterial diffractive lens uses nanofabricated structures to realize the desired phase shifts (and/or amplitude variations) with respect to position. The metamaterial diffractive lens may use sub-wavelength structures. For example, the metamaterial diffractive lens may use plasmonic resonant type structures. Alternatively or additionally, the metamaterial diffractive lens may use nanofin structures that are rotated by a systematically increasing angle to achieve the desired phase shift (e.g., in a geometric phase type metamaterial lens or metalens for short). Additionally, the metamaterial diffractive lens may use a propagation phase type metalens in which the phase profile is realizes by modifying the diameters of nanopillars with respect to position. The metamaterial diffractive lens can use any micro or nano fabricated structure or combination thereof to achieve a phase profile that acts as a lens, including those discussed in<NPL>); and <NPL>.

<FIG> illustrate respective embodiments of the analog NV system <NUM> in which the intensifier module <NUM> includes an integrated overlay display <NUM>. In <FIG>, the intensifier module <NUM> is integrated with an overlay display <NUM>, but does not include a planar lens <NUM>. Accordingly, a refractive lens <NUM> is provided in the intensifier housing <NUM> after the intensifier module <NUM>. The intensifier module <NUM> is shortened to allow for the space occupied by the refractive lens <NUM> in the intensifier housing <NUM>.

In <FIG>, the intensifier module <NUM> is integrated with an overlay display <NUM>, and is integrated with a planar lens <NUM>. Accordingly, a refractive lens <NUM> is not provided in the intensifier housing <NUM> after the intensifier module <NUM>. The intensifier module <NUM> is not shortened because there is no need to allow for space occupied by the refractive lens <NUM> in the intensifier housing <NUM>.

Referring now to <FIG>, in certain non-limiting embodiments, the overlay display <NUM> may include active silicon areas, which are illustrated as active silicon islands <NUM> (e.g., native silicon islands). The active silicon islands <NUM> can be used to fabricate transistors, such as MOSFETs by doping the silicon (Si) with spatially varying concentrations donor and acceptor atoms. Further, the MOSFETs may be fabricated using intermetal and dielectric layers <NUM> that include insulators (e.g., oxides and dielectrics) and metal traces <NUM>. In certain embodiments, the MOSFETs may provide (but are not limited to providing) logic functions and/or control functions (e.g., to control turning on/off the LEDs in the OLED stack <NUM>).

In the example illustrated in <FIG>, each of the active silicon islands represents a pixel of the overlay display <NUM>. Thus, by powering various LEDs in the OLED stack <NUM> using the transistors in the active silicon islands, a display image can be created by the overlay display <NUM> and output to a user. For example, a display image may be created by outputting the display light <NUM>, as illustrated in <FIG>, discussed below. In <FIG>, the intensified light <NUM> enters the overlay display <NUM> from the bottom, passes through the oxide <NUM> and then through the other layers before exiting the overlay display <NUM> through the cover glass <NUM>. The display light <NUM> is generated in the OLED and, like the intensified light <NUM>, the display light <NUM> exits through the cover glass <NUM>. After exiting through the cover glass, both the display light <NUM> and the intensified light <NUM> are transmitted to the eyepiece <NUM> of the NV system <NUM>, and then to the user.

Whereas the pixels (i.e., Si island <NUM>, metal traces <NUM>, and OLEDs in the OLED stack <NUM>) substantially attenuate the intensified light <NUM>, transparent regions between the pixels are at least partially transparent to the intensified light <NUM>. Accordingly, the intensified light <NUM> is transmitted through the transparent regions between the pixels of the overlay display <NUM>. In contrast, the active Si islands <NUM> and the metal traces <NUM> substantial block the intensified light <NUM>.

<FIG> illustrates a top-down view of a portion of an overlay display <NUM> in which the opaque regions (e.g., regions including the active Si islands <NUM> and metal traces <NUM>) are configured with transparent region <NUM> between the opaque regions. The active Si islands <NUM> and metal traces <NUM> may be configured as electronic components (such as MOSFETs) to provide logic functions and to provide control functions for the control of pixels in an overlay display <NUM>. Additionally, the circuitry of the controller logic (i.e., the circuitry determining the relative intensities of the pixels) may also be located in the opaque regions. The active Si islands <NUM> and metal traces <NUM> substantially block the intensified light <NUM>, but the intensified light <NUM> may be transmitted through the transparent region <NUM> between the Si islands <NUM> and metal traces <NUM>.

<FIG> illustrates an example of an image in which an overlay display <NUM> superimposes text and other graphical symbols over an amplified image of a nightscape that includes trees and clouds. As discussed above, the overlay display <NUM> may include functionality for displaying information to a user. Such information may include graphical content, including text, images, superimposed thermal image data and the like. The overlay display <NUM> outputs display light <NUM> which can be sent to the eyepiece. Thus, an image such as that illustrated in <FIG> is presented to the user in the NV system <NUM>.

In the examples above it should be noted that although not shown various alternatives can be implemented. For example, in any of the embodiments illustrated, a backside fill may be used or may be omitted. Alternatively, or additionally, while the active areas have been shown as being substantially square in nature, it should be appreciated that the active areas may be rectangular or other appropriate shapes.

The discussion above refers to a number of methods and method acts that may be performed.

Claim 1:
An optical device comprising:
a semiconductor chip having a first surface that receives direct-view light and transmits the direct-view light through the transparent regions (<NUM>) of the optical device,
a plurality of electro-optical circuits formed on the semiconductor chip, including
light emitters (<NUM>) configured to output display light, and the transparent regions (<NUM>) being arranged between respective light emitters of the light emitters; and
a planar, diffractive lens (<NUM>) arranged to induce a phase curvature on the display light (<NUM>) and to induce a same phase curvature on the direct-view light as on the display light.