Conical optical combiner

Optical systems and methods are provided, which combine see-through view of the real world and display source images using a conical optical combiner cut to have flat surfaces normal to the viewer line of sight. The conical shape minimizes interferences in the view of the real world as the edges of the optical combiner are tangent to the viewer vision field of view and the inner part of the optical combiner is semitransparent. Additionally, the optical system comprises a beam splitter, a shutter(s) for attenuating or blocking the see-through path and may employ polarizing element to improve the contrast between the scene observation and the projected display and thus enabling selective viewing of either. The system may also be configured to enable diopter adjustment and virtual display distance adjustments.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase Application of PCT International Application No. PCT/IL2018/051250, International Filing Date Nov. 20, 2018, entitled: “A CONICAL OPTICAL COMBINER”, published on May 23, 2019, under PCT International Application Publication No. WO 2019/097522, which claims the priority of Israel Patent Application No. 255795, filed on Nov. 20, 2017, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the field of optical devices, and more particularly, to optical devices combining see through and display visualization.

2. Discussion of Related Art

Optical devices, in particular head-worn devices, often combine real world observation with added displayed images, e.g., in various augmented reality applications. This combination is challenging due to the difference in sources and variable environmental conditions in which such optical devices are expected to operate in.

SUMMARY OF THE INVENTION

The following is a simplified summary providing an initial understanding of the invention. The summary does not necessarily identify key elements nor limit the scope of the invention, but merely serves as an introduction to the following description.

One aspect of the present invention provides an optical system comprising: (i) a display device with associated optics, (ii) an optical combiner comprising a beam splitter and having a flat small base, a large base which is curved with respect to a plane parallel to the small base, wherein the small and large bases are connected by: a first surface configured to mediate between the associated optics of the display device and the beam splitter, and a curved side which is part of a truncated cone having the small base and the plane as bases; wherein the optical combiner together with the display device with associated optics is configured to deliver rays originated from the display device and to form an image to a viewer with pupil plane parallel to the small base, and wherein the optical combiner is transparent to rays reaching from a real world scene entering the optical combiner through the large base and passing through the beam splitter, (iii) a see-through distortion corrector attached to the large base at a curved surface of the see-through distortion corrector, wherein the see-through distortion corrector further has a flat side facing the scene, wherein the curved side, which is part of a truncated cone, is coated with an absorptive coating, the small base and the flat side of the see-through distortion corrector are coated with anti-reflective coatings; and the large base is coated with a partly reflective coating, and (iv) a shutter positioned in front of the see-through distortion corrector, configured to attenuate or block the rays from the real world scene upon actuation.

DETAILED DESCRIPTION OF THE INVENTION

Optical systems and methods are provided, which combine see-through view of the real world and display source images using a conical optical combiner cut to have flat surfaces normal to the viewer line of sight. The conical shape minimizes interferences in the view of the real world as the edges of the optical combiner are tangent to the viewer vision field of view and the inner part of the optical combiner is semitransparent. Additionally, the optical system comprises a beam splitter, a shutter(s) for attenuating or blocking the see-through path and may employ polarizing element to improve the contrast between the scene observation and the projected display and thus enabling selective viewing of either. The system may also be configured to enable diopter adjustment and virtual display distance adjustments.

FIGS. 1A-1Fare high level schematic illustrations of an optical system100, according to some embodiments of the invention.FIGS. 1A-1Fillustrate schematically an optical combiner105in optical system100from the viewer point of view (FIG. 1A) and from side view (FIG. 1B), schematic beam paths illustrating the see-through optical path (FIG. 1C) and the display view optical path (FIGS. 1D, 1E) in optical system100; and optical system100in exploded view (FIG. 1F). Surfaces of elements in optical system100are denoted by numerals105B-E and coatings of these surfaces are denoted correspondingly by numerals105AC-105EC,

Optical system100comprises an image source95such as a display (used herein as a non-limiting example), with associated optics97(shown schematically), optical combiner105which contains a beam splitter104with partly reflective surfaces104A,104B and curved semi reflective element108with partly reflective surfaces108A,108B possibly having coating(s)104AC,104BC,108AC,108BC (respectability as explained below) and having a flat small base105D and a large base105B which is curved with respect to a plane parallel to small base105D. Bases105B,105D are connected by a surface105E and a curved side105C, curved side105C being part of a truncated cone having small base105D and the surface105B as bases. Surface105E is configured to mediate between associated optics97of the image source95and optical combiner105. In certain embodiments (e.g., illustrated schematically inFIG. 1E) associated optics97may be integrated into flat side105E of optical combiner105, forming optical-combiner-integrated associated optics97. This option may be applied in any of the embodiments of system100, depending e.g., on the required field of view and system dimensions.

Optical combiner105is configured to deliver, to a pupil plane90parallel (or close to parallel, deviating e.g., by 1°, 5°, 10° or any intermediate value from the parallel surface) to small base105D, rays (FIG. 1D) from image source95entering optical combiner105through surface105E as well as rays (FIG. 1C) from a real world scene entering optical combiner105through large base105B, passing through beam splitter105A and reaching a pupil plane90.

Optical system100further comprises a see-through distortion corrector110attached to surface108B of curved semi reflective element108is attached to large base105B at a curved surface of see-through distortion corrector110. See-through distortion corrector110further has a flat side110B facing the real-world scene and curved surface on the other side110A, and when attached to large base105B via curved semi reflective element108cancels any optical power of optical system100for rays reaching from the real-world scene to the pupil plane and thus prevents distortions of the real world view.

As illustrated in the exploded view ofFIG. 1F, corresponding coatings may be applied to element surfaces in system100. Curved side105C may be coated with a black (or any other effective) absorptive coating105C. Small base105D and see-through distortion corrector external surface110may be coated with anti-reflective coatings105DC and110BC respectively. Surface105B is possibly coated with semi-reflective coating105BC, and surface105B and the inner surface of distortion corrector110A are possible coated with index matching coatings110AC. Small base105D and surface105E may also be coated with anti-reflective coatings105DC and105EC, respectively. beam splitter104surfaces104A,104B may be coated by anti-reflective and possibly index matching coating104AC,104BC.

In certain embodiments, examples for image source95may comprise micro-displays based on any of the following: OLED (organic light emitting diodes), LED (light emitting diodes), MEMS (micro electromechanical systems), DLP (digital light processing), scanning mirror(s), LCOS (liquid crystal on silicon), LCD (liquid crystal display). System100and/or elements thereof may be made of various materials such various types of glass, of plastic and combinations thereof.

FIGS. 2A and 2Bare high level schematic illustrations of optical combiner105and see-through distortion corrector110in optical system100, according to some embodiments of the invention.FIGS. 2A and 2Bschematically illustrate the geometric relations between the width of top front edge (D1) connecting surface105E and flat small base105D with respect to viewing point91(part of pupil plane90). D2 denotes the width of large base105B (and/or corrector110). ER denotes the eye relief distance, L denotes the length of optical combiner105(illustrated schematically in top view), and the cone angle θ≈atan(0.5·D1/ER). The dimensions of optical combiner105may be adjusted mainly to support the display field of view and provide a required eye relief distance. Optical system100may be configured as a head-worn device (for one or two eyes) with minimum interference and distortion of the real-world view. The outer parts of optical combiner105may be polished to a conic shape to cause minimal cross sectional interferences to the viewer, and may be coated with an absorptive coating to prevent stray light, ghosts and internal reflection. The inner diameter (D1) dimension and outer diameter (D2) dimension of optical combiner105may be determined by the dimensions of optical system100and the required operation guidelines (e.g., field of view, eye relief, weights and the like).

FIGS. 3 and 4are high level schematic illustrations of optical system100with a shutter120, according to some embodiments of the invention. Optical system100may further comprise shutter120positioned in front of see-through distortion corrector110and configured to attenuate or block the rays (FIG. 1C) from the scene upon actuation. Shutter120may be configured to obstruct the see-through path through optical combiner105and may be used to increase the contrast of the displayed image on image source95and/or to help the user distinguish between the images of the scene and the display.

Shutter120may be embedded directly in contact to optical combiner105and/or see-through distortion corrector110, or the shutter may be set at some distance therefrom. The form and/or size may be similar to large base105B and/or corrector110or larger therefrom. Optical system100may comprise two optical combiners105to provide stereo vision. In such case, shutter120may overlap both beam optical combiners105and possibly a gap between them. In certain embodiments, shutter120may be implemented as any of coatings105BC,108AC,108BC,110AC,110BC on large base105B, curved semi reflective element108and/or distortion corrector110(seeFIG. 1F).

Shutter120may be any of an LCD (liquid crystal display) shutter, a polarized LCD shutter, a polymer shutter, an opto-chrome shutter and a mechanical shutter; and may be configured to provide multiple levels of attenuation. For example, shutter120may be operated to partly or fully block the see-through path and/or have multiple levels of transparency. Shutter120may be spatially variable, i.e., have different regions with different levels of attenuation, possibly corresponding to different regions of image source95with respect to their overlapping in beam splitter104.

Shutter120may be configured to be actuated automatically by optical system100, manually by a user of optical system100, by a tracker of the user's head or eyes (and/or a gesture identifying device) and/or by an illumination sensor sensing a scene illumination.

A display polarizing filter125may be positioned between image source95and flat side105E of optical combiner105, with shutter120implemented as a polarizing shutter large base coating105BC, being polarized similar to polarizing shutter120.

According to some embodiments of the present invention, each coating of optical combiner105may be polarized. In some cases, even if the display is not polarized, the coatings are. This is done because the optical elements themselves might render the rays polarized and so they behave differently to angles or direction that the rays come from.

For example, Optical combiner105may be configured with a polarizing beam splitter (PBS)104with corresponding coating104BC,104AC, and the polarizations of display polarizing filter125and polarizing shutter120may be selected to be semi-perpendicular. Beam splitter104may be configured to set a predefined relation between rays from the image generator and from the scene (denoted schematically as inFIGS. 1D and 1C). The inventors have found out that applying polarizing elements as described above may improve the see-through image approximately threefold.

FIG. 5is a high level schematic illustration of optical system100with variable diopter lens and display source distance, according to some embodiments of the invention. Optical system100may be configured to have an adjustable distance (marked D) between image source95and surface105E, and further comprise a variable diopter lens130(the two illustrated parts are parallel adjustable as marked by arrow E) between small side105D and the viewing point (not shown, see viewing point91inFIG. 2B). Variable diopter lens130may be implemented by a flexible lens as well. Adjustable distance D and variable diopter lens130may be adjustable independently and mechanically. Distance D is proportional to the apparent image distance seen by the viewer. Variable diopter lens130effects and corrects both the image and the real world view seen by the viewer. Adjustments of lens130and distance D may be used to adapt optical system100to specific users.

In certain embodiments, denoted schematically inFIG. 5by numeral106A, surface105E and at least a part of optics97may be merged to provide a non-flat side105E with specified optical performance. Moreover, in certain embodiments denoted schematically inFIG. 5by numeral106B, flat small base105D may be configured to be non-flat small base105D to correct possible image distortions and/or aberrations of image source95and/or scene images by optical system100. For example, such distortions and/or aberrations may be related to the forms of large base105B (which may be in certain embodiments flat), see-through distortion corrector110and possibly the surface of non-flat side105E. In certain embodiments, two see-through distortion correctors may be applied, one on large base105B and one on small base105D. The see-through distortion correctors may be configured to correct distortions and/or aberrations in optical system100.