CN-116348707-B - Compact head mounted display system with small input aperture and large output aperture

CN116348707BCN 116348707 BCN116348707 BCN 116348707BCN-116348707-B

Abstract

An optical device comprises a first light-transmissive substrate having at least two parallel major surfaces, a light-wave input aperture, a light-wave output aperture located beside one of the major surfaces of the substrate, a light-wave output pupil, a light-wave input element for coupling a light wave having a field of view and a central light wave into the substrate for total internal reflection from the major surfaces of the substrate, and at least one reflective surface having an active area and located between the two major surfaces of the light-transmissive substrate for coupling light waves out of the substrate, wherein light waves trapped inside the substrate are reflected at least twice by the active area of the reflective surface before being coupled out of the substrate, substantially between first and second reflectance from the reflective surface, then reflected from the reflective surface and through the output aperture towards the output pupil. An optical device for transmitting light waves is also provided.

Inventors

Y. Amidine

Assignees

奥里姆光学有限公司

Dates

Publication Date: 20260505
Application Date: 20210801
Priority Date: 20200803

Claims (12)

1. An optical device, comprising: A first light-transmitting substrate having at least two parallel major surfaces; A light wave input hole; a light wave output aperture located beside one of the major surfaces of the substrate; The light wave outputs pupils; A light wave input element for coupling a light wave having a field of view and a central light wave into the substrate to achieve total internal reflection from a major surface of the substrate, and At least a first reflective surface having an active area and being located between two major surfaces of said light transmissive substrate for coupling light waves out of said substrate, Wherein the first reflective surface is configured to have a critical angle with respect to light waves trapped inside the substrate and is oriented inside the substrate such that for an entire field of view light waves trapped inside the substrate are reflected by an active area of the first reflective surface at least first and second reflections, substantially between first and second reflectances from the first reflective surface, from one of the major surfaces, then from the first reflective surface and through the output aperture in the direction of the output pupil, and For the entire field of view, the angle of incidence of the coupled light wave at the first reflective surface is above the critical angle at the first reflection and below the critical angle at the second reflection, the light wave incident at the first reflective surface at the second reflection being split by the first reflective surface into two parts, a part of the light wave being coupled out of the first light-transmissive substrate in the direction of the output pupil without any redirecting element and another part passing through the first reflective surface.
2. The optical device of claim 1, wherein an optical adhesive having a lower refractive index than the refractive index of the light transmissive substrate is applied at the first reflective surface, and the critical angle is determined by a ratio between the refractive index of the substrate and the optical adhesive, respectively.
3. The optical device of claim 1, further comprising a second reflective surface, wherein a portion of the light wave passing through the first reflective surface propagates inside the first light transmissive substrate and is coupled out towards the output pupil through the second reflective surface.
4. The optical device of claim 2, wherein light waves trapped inside the substrate reflect from the input element and the first reflective surface the same number of reflections.
5. The optical device of claim 3, wherein light waves trapped inside the substrate after a single reflection from the input element are totally reflected by the second reflective surface at a first reflectance and reflected from the second reflective surface toward the output pupil portion at a second reflectance.
6. The optical device of claim 1, wherein the first reflective surface is configured such that a central wave of the field of view is coupled out of the substrate substantially normal to a major surface of the substrate.
7. The optical apparatus of claim 4, wherein the input element is partially reflective to light waves arriving directly from the input aperture and totally reflective to light waves reflected once from the input element and once from one of the major surfaces of the substrate.
8. The optical device of claim 7, wherein the light waves from the input aperture partially pass through the input surface toward the output aperture of the optical device.
9. An optical device for transmitting light waves, comprising: A first light-transmitting substrate having at least two parallel major surfaces and at least one edge; A light wave input hole; A light wave output hole located beside one of the major surfaces of the first light-transmitting substrate; The light wave outputs pupils; A first input surface for coupling light waves having a first field of view and a central light wave into the first light-transmitting substrate to achieve total internal reflection from a major surface of the first light-transmitting substrate, an At least a first reflective surface having an active area and being located between two major surfaces of said first light transmissive substrate for coupling light waves out of said first light transmissive substrate, Wherein the first input surface is configured to have a critical angle with respect to light waves trapped inside the first light-transmissive substrate and is oriented inside the first light-transmissive substrate such that light waves coupled into the first light-transmissive substrate through the input aperture substantially normal to a major surface of the first light-transmissive substrate are reflected by the first input surface at least first and second reflections before being coupled into the first light-transmissive substrate and are reflected from one of the major surfaces substantially between first and second reflections from the first input surface, For the entire field of view, the angle of incidence of the coupled light wave on the first input surface being below the critical angle on the first reflection and above the critical angle on the second reflection, the light wave incident on the first reflection surface at the first reflection being split by the first reflection surface into two parts, a part of the light wave passing through the first input surface and being coupled out of the first light-transmissive substrate through the output aperture and another part being reflected by and coupled into the first light-transmissive substrate, and Wherein light waves trapped inside the first light-transmissive substrate are reflected at least twice by the active area of the first reflective surface before being coupled out of the first light-transmissive substrate through the output aperture substantially normal to the major surface of the first light-transmissive substrate, and light waves passing through the input aperture substantially normal to the major surface of the first light-transmissive substrate are reflected once by the first input surface before being coupled into the first light-transmissive substrate.
10. The optical device of claim 9, further comprising: A second light-transmitting substrate having at least two parallel major surfaces and at least one edge; a second input surface for coupling light waves having a second field of view into the second light-transmitting substrate to achieve total internal reflection from a major surface of the second light-transmitting substrate, an At least a second reflective surface having an active area and being located between two major surfaces of said second light-transmitting substrate for coupling light waves out of said second light-transmitting substrate, Wherein light waves coupled into the second light-transmitting substrate from the input aperture substantially normal to a major surface of the second light-transmitting substrate are reflected at least twice by the second input surface before being coupled into the second light-transmitting substrate and substantially between first and second reflectivities from the second input surface from one of the major surfaces, and the first and second light-transmitting substrates are optically attached at edges, and the first and second input surfaces of the first and second light-transmitting substrates are disposed adjacent to each other.
11. The optical device of claim 9, wherein an optical adhesive having a lower refractive index than the refractive index of the light transmissive substrate is applied at the input surface, and the critical angle is determined by a ratio between the refractive indices of the optical adhesive and the light transmissive substrate, respectively.
12. The optical device of claim 9, wherein a portion of the light wave passing through the first input surface is coupled out of the first light-transmissive substrate through the output aperture in the direction of the output pupil.

Description

Compact head mounted display system with small input aperture and large output aperture Technical Field The present invention relates to substrate-based light wave guiding optical devices, and in particular to devices comprising a reflective surface carried by a light-transmissive substrate. The invention may be implemented to advantage in a large number of imaging applications such as head-mounted and head-up displays as well as cellular telephones, compact displays and 3-D displays. Background One of the important applications for compact optics is in Head Mounted Displays (HMDs), where the optical module acts as both an imaging lens and a combiner, where a two-dimensional display is imaged to infinity and reflected into the eye of the observer. The display may be obtained directly from a Spatial Light Modulator (SLM), such as a Cathode Ray Tube (CRT), a Liquid Crystal Display (LCD), an organic light emitting diode array (OLED), a scanning source, and the like, indirectly via a relay lens or fiber optic bundle. The display comprises an array of elements (pixels) imaged to infinity by a collimating lens and transmitted into the eye of the observer by means of a reflective or partially reflective surface acting as a combiner for non-see-through and see-through applications, respectively. Conventional free space optical modules are typically used for these purposes. As the desired field of view (FOV) of the system increases, such conventional optical modules become larger, heavier, and more cumbersome, and thus, impractical even for medium performance devices. This is therefore a major drawback for all kinds of displays but especially in HMDs where the system should be as light and compact as possible. The need for compactness has led to several different complex optical solutions, all of which are still insufficiently compact for most practical applications on the one hand, and all of which suffer from major drawbacks in terms of manufacturability, price and performance on the other hand. The teachings included in international patent publication nos. WO2017/141239, WO2017/141240, WO2017/141242, WO2019/077601 and WO2020/157747 are incorporated herein by reference. Disclosure of Invention The present invention facilitates the provision of a compact substrate for HMD applications and the like. The present invention allows a relatively wide FOV along with a relatively large Eye Movement Box (EMB) value. The resulting optical system supplies a large high quality image that also accommodates large movements of the eye. The optical system according to the invention is particularly advantageous because it is substantially more compact than prior art implementations, however, it can even be easily incorporated into optical systems having various specialized configurations. It is therefore a broad object of the invention to alleviate the drawbacks of prior art compact optical display devices and to provide other optical components and systems with improved performance according to specific requirements. Thus, according to the present invention there is provided an optical device comprising a first light transmissive substrate having at least two parallel major surfaces, an input aperture, an output aperture alongside one of the major surfaces of the substrate, an output pupil, an input element for coupling light waves having a field of view and a central light wave into the substrate to achieve total internal reflection from the major surfaces of the substrate, and at least one planar reflective surface having an active area and located between the two major surfaces of the light transmissive substrate for coupling light waves out of the substrate, wherein light waves trapped inside the substrate are reflected at least twice by the active area of the reflective surface before being coupled out of the substrate, substantially between first and second reflectance from the reflective surface, then reflected from the reflective surface and directed towards the output pupil through the output aperture. There is further provided in accordance with the present invention an optical device for transmitting light waves, comprising a first light-transmissive substrate having at least two parallel major surfaces and at least one edge, an input aperture, an output aperture alongside one of the major surfaces of the substrate, an output pupil, an input surface for coupling light waves having a first field of view and a central light wave into the substrate to achieve total internal reflection from the major surfaces of the substrate, and at least one planar reflective surface having an active area and located between the two major surfaces of the light-transmissive substrate for coupling light waves out of the substrate, wherein light waves coupled into the substrate substantially normal to the major surfaces of the substrate through the input aperture are reflected at least twice by the input surface and substantially between fi