Waveguide with 2 layers of stack

Abstract

A lightweight laminated optical waveguide uses two plastic substrates with nanostructure gratings and a single glass substrate sandwiched between them. The nanostructure gratings face each other and are each encapsulated within the optical waveguide. The two plastic substrates are each adhesively secured to the central glass substrate rather than to each other to provide sufficient securing strength and to precisely establish and maintain the air gap between the substrates. The thicknesses of the plastic substrates and the glass substrate are selected so that the laminated optical waveguide is lightweight but also has sufficient drop performance. The laminated optical waveguide can be efficiently manufactured since the plastic substrates are bonded to the glass substrate by the adhesive.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 076,583, filed on September 10, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This topic relates to optical waveguides for displays, such as goggle devices for smart glasses and headwear. Background Technology

[0004] Optical waveguides can be formed using techniques that can generate defects. Attached Figure Description

[0005] The accompanying drawings depict one or more implementations by way of example only and not limitation. In the drawings, the same reference numerals denote the same or similar elements.

[0006] Figure 1 A stacked optical waveguide with two glass substrates fixed to each other is shown;

[0007] Figure 2 A stacked optical waveguide with two plastic substrates is shown, each plastic substrate being fixed to a glass substrate sandwiched between the plastic substrates; and

[0008] Figure 3 A flowchart illustrating a method for fabricating stacked optical waveguides is shown. Detailed Implementation

[0009] This disclosure includes examples of lightweight stacked optical waveguides using two plastic substrates with nanostructured gratings and a single glass substrate sandwiched between them. The nanostructured gratings face each other and are each encapsulated within the optical waveguide. The two plastic substrates are each bonded to a central glass substrate rather than to each other to provide sufficient fixation strength and precisely establish and maintain the air gap between the substrates. The thicknesses of the plastic and glass substrates are chosen to make the stacked optical waveguide lightweight but also to provide sufficient drop performance. The stacked optical waveguide can be fabricated efficiently because the adhesive bonds the plastic substrates to the glass substrate.

[0010] Further objects, advantages, and novel features of the example will be set forth in part in the description which follows, and will become partly apparent to those skilled in the art upon study of the description and the accompanying drawings, or may be learned by production or operation of the example. The objects and advantages of this subject matter may be realized and obtained by means and combinations of methods, means, and combinations particularly pointed out in the appended claims.

[0011] In the following detailed description, numerous specific details are illustrated by way of example to provide a thorough understanding of the relevant teachings. However, it will be clear to those skilled in the art that the teachings can be practiced without such details. In other examples, well-known methods, processes, components, and circuits have been described in a relatively higher-level manner, without detail, to avoid unnecessarily obscuring multiple aspects of the teachings.

[0012] As used herein, the term "connection" means any logical, optical, physical, or electrical connection, link, etc., that transmits a signal or light generated or provided by one system element to another connected element. Unless otherwise described, connected elements or devices are not necessarily directly connected to each other and can be separated by intermediate parts, elements, or transmission media that can be modified, manipulated, or carry light or signals.

[0013] The orientation of the goggle device, associated components, and any complete device combining an eye scanner and a camera (such as those shown in any of the accompanying drawings) is given by way of example only for illustrative and discussion purposes. In operation for a particular variable optical processing application, the goggle device may be oriented in any other direction suitable for the specific application of that goggle device, such as up, down, side, or any other orientation. Moreover, within the scope used herein, any directional terms, such as front, back, inside, outside, facing, left, right, lateral, longitudinal, up, down, upper, lower, top, bottom, and side, are used by way of example only and do not limit the orientation or orientation of any optical device or components of an optical device constructed as otherwise described herein.

[0014] Now refer in detail to the examples shown in the accompanying drawings and discussed below.

[0015] refer to Figure 1 The stacked optical waveguide 10 can utilize two glass substrates 12 and 14, each having a single cover plate substrate 16. The stacked optical waveguide 10 is suitable for use as an image display, such as a see-through display for goggles including smart glasses and head-mounted devices. Each of the optically clear glass substrates 12 and 14, and the cover plate 16, is spaced apart from each other at their edges by an adhesive 18 to form air gaps 20 and 22 to achieve the necessary optical stacking and to encapsulate the optical nanostructure grating 24 for reliability purposes. Plastic substrates are desirable from the perspective of product weight and drop performance. However, precisely mimicking the glass substrate waveguide stack 10 with plastic substrates introduces a lamination problem between the two plastic substrates—that is, laminating two “soft” substrates together with air gaps while maintaining a constant gap between them.

[0016] refer to Figure 2This disclosure provides an improved stacked optical waveguide 30 to achieve a waveguide stack using two plastic substrates 32 and 34 and a single “rigid” glass cover plate 36, thereby providing advantages in product weight and reliability. Both plastic substrates 32 and 34 are lighter than the glass substrate 36, providing a lighter stacked optical waveguide 30. Each of the plastic substrates 32 and 34 is bonded at its edges to the opposite side of the glass cover plate 36 sandwiched between them by adhesive 38, thereby forming air gaps 40 and 42 between them, as shown. Each of the plastic substrates 32 and 34 is optically transparent and has a corresponding optical nanostructure grating 44 facing the glass cover plate 36 and facing each other. This eliminates the difficulty of bonding the two soft plastic substrates 32 and 34 together, which posed a challenge in maintaining a constant air gap between them, necessary for acceptable waveguide performance with an acceptable modulation transfer function (MTF). The flexible plastic substrates 32 and 34 are each fixed to the rigid glass substrate 36 on each side for support during manufacturing. This design provides a “constant thickness” glass substrate 36 that acts as a physical spacer and support between the two plastic substrates, governing the spacing, rather than stacking the two flexible substrates 32 and 34 opposite each other, which would “flip” and potentially cause changes in the interlayer gaps.

[0017] Furthermore, this disclosure allows the glass substrate 36 to be separated from the waveguide function itself because the glass substrate 36 does not include the optical nanostructure grating 24. This allows the use of conventional chemically strengthened glass for the glass substrate 36 (e.g., (Glass). This, in turn, allows for the use of thinner glass in the glass substrate 36, which helps reduce product weight while maintaining product drop performance through the use of chemically strengthened glass.

[0018] The chemically strengthened glass substrate 36 also contributes to product performance from the drop angle, which is the distance at which the device can be dropped and functionally withstand the impact of a drop. Since typical waveguide glass substrates are not chemically strengthened, the drop angle poses a risk. Furthermore, by having each of the waveguide structures 32 and 34 face the glass substrate 36 and be sealed with adhesive 38, excellent reliability is achieved, and the nanostructured grid 44 is encapsulated within the stack and not exposed to the environment.

[0019] In one example, the thickness of the glass substrate 36 can be between 300 micrometers and 1000 micrometers, and each plastic substrate can have a thickness between 50 micrometers and 1000 micrometers. The thickness of the adhesive 38 can be between 50 and 100 micrometers, and therefore the spacing between air gaps 40 and 42 can be between 50 and 100 micrometers. However, no limitations should be inferred on these thicknesses. These dimensions are formed to provide good drop performance while limiting the weight of the stacked optical waveguide 30.

[0020] refer to Figure 3 The flowchart of a method 300 for forming a stacked optical waveguide 30 is shown.

[0021] At frame 302, corresponding plastic substrates 32 and 34 are formed using conventional processing techniques. A corresponding nanostructured grating 44 provides waveguides for light to pass through and form an image display. A glass substrate 36 is also formed, and may be chemically strengthened glass, which further contributes to product performance from a drop angle.

[0022] At frame 304, the plastic substrate 32 is fixed to the glass substrate 36 at the edge of the substrate using adhesive 38. The plastic substrate 32 is oriented such that the corresponding nanostructured grid 44 faces the glass substrate 36. The adhesive establishes the thickness of the corresponding gap 42.

[0023] At frame 306, the plastic substrate 34 is fixed to the glass substrate 36 at the edge of the substrate using adhesive 38. The plastic substrate 34 is also oriented such that the corresponding nanostructured grid 44 faces the glass substrate 36. The adhesive establishes the thickness of the corresponding gap 40.

[0024] It should be understood that the terms and expressions used herein have their general meanings unless otherwise specified herein, consistent with the specific meanings of these terms and expressions in relation to the relevant field of investigation and research. Relational terms such as "first" and "second" may be used merely to distinguish one entity or action from another, without necessarily requiring or implying any actual such relationship or order between these entities or actions. The terms "comprise," "comprising," "includes," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes or comprises a list of elements or steps includes not only those elements or steps but may also include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "an" or "a" does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes that element.

[0025] Unless otherwise stated, any and all measurements, values, ratings, locations, amplitudes, sizes, and other specifications set forth in this specification (including in the following claims) are approximate and imprecise. These quantities are intended to have a reasonable range consistent with the functions they relate to and with the conventions of the field to which they belong. For example, unless expressly stated otherwise, parameter values, etc., may deviate from the quantities by up to ±10%.

[0026] Furthermore, as can be seen in the above specific embodiments, for the purpose of simplification, the various features are combined in the various examples. The method of this disclosure should not be construed as reflecting an intention to require more features than are expressly stated in each claim. Rather, as reflected in the following claims, the subject matter to be protected lies in fewer than all features of any single disclosed example. Therefore, the following claims are thus incorporated into the specific embodiments, wherein each claim exists independently as a separately claimed subject matter.

[0027] While the foregoing has described what is considered the best model and other examples, it should be understood that various modifications may be made therein, and the subject matter disclosed herein can be implemented in different forms and examples, and these can be applied to many applications, of which only a few have been described herein. The appended claims are intended to claim protection for any and all modifications and variations that fall within the true scope of this concept.

Claims

1. A stacked optical waveguide, comprising: Glass substrate; A first plastic substrate having a first optical structure, the first plastic substrate being fixed to and spaced apart from the glass substrate; as well as A second plastic substrate having a second optical structure is fixed to and spaced apart from the glass substrate, such that the glass substrate is located between the plastic substrates. The optical structures face each other.

2. The waveguide according to claim 1, wherein, The optical structure includes an optical grid.

3. The waveguide according to claim 1, wherein, The plastic substrates are all fixed to the glass substrate using adhesive.

4. The waveguide according to claim 1, wherein, Both the plastic substrate and the glass substrate are optically transparent.

5. The waveguide according to claim 1 further includes an air gap between the plastic substrate and the glass substrate.

6. The waveguide according to claim 1, wherein, The plastic substrate is softer than the glass substrate.

7. The waveguide according to claim 1, wherein, The plastic substrates are all lighter than the glass substrates.

8. The waveguide according to claim 1, wherein, The glass substrate is chemically hardened.

9. The waveguide according to claim 8, wherein, The thickness of the glass substrate is between 50 and 100 micrometers.

10. A method for processing stacked optical waveguides, comprising: A first plastic substrate is fixed to a glass substrate, the first plastic substrate having a first optical structure, and the first plastic substrate being spaced apart from the glass substrate; as well as A second plastic substrate is fixed to the glass substrate. The second plastic substrate has a second optical structure. The second plastic substrate is spaced apart from the glass substrate, such that the glass substrate is located between the plastic substrates. The optical structures face each other.

11. The method according to claim 10, wherein, The optical structure includes an optical grid.

12. The method according to claim 10, wherein, The fixing includes using an adhesive to fix the plastic substrate to the glass substrate.

13. The method according to claim 10, wherein, Both the plastic substrate and the glass substrate are optically transparent.

14. The method of claim 10, further comprising forming an air gap between the plastic substrate and the glass substrate.

15. The method according to claim 10, wherein, The plastic substrate is softer than the glass substrate.

16. The method of claim 10, wherein, The plastic substrates are all lighter than the glass substrates.

17. The method according to claim 10, wherein, The glass substrate is chemically hardened.

18. The method according to claim 17, wherein, The thickness of the glass substrate is between 50 and 100 micrometers.

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