Patent ID: 12259542

DETAILED DESCRIPTION

Briefly, an optical viewfinder assembly or system (or “optical viewfinder”) is described that is particularly well suited for use in a head of a walk around or character costume. It can be positioned between a view slit or aperture (e.g., any opening in an otherwise opaque shell or head structure of a costume) and an expected position of an eye or eyes of a person wearing the costume (e.g., a wearer or a performer). The optical viewfinder is used to view an upright image of the view taken at (and through) the costume head's eyes or view slit.

In one useful embodiment, the optical viewfinder may include a lens that is located at the costume's view slit, and the view of the outside world from the perspective of this incoming (or aperture or objective) lens is redirected 90 degrees (and flipped) in some cases by a roof pentaprism to form an upright image onto a diffusing screen. The viewer or performer looks at the image on the screen after it is bounced off a 45-degree mirror and through an eyepiece (or output lens). The eyepiece is configured to place the image at “infinity” and allows comfortable viewing of the diffusing screen close to the eye of the viewer. The 45-degree mirror makes the viewpoints of the eye and the aperture or objective lens in the same direction, just offset a distance vertically (e.g., a vertical offset distance from the aperture/eye slit and the location of the wearer's eyes). The viewer/wearer sees a 1:1 upright image of the outside world (or one that is magnified if desired by changing the ratio of the objective and eyepiece lenses) from the offset viewpoint at the costume head's eyes or view slit. Two systems, one for each eye, may be used to provide stereoscopic viewing so the viewer can see the world outside the costume head in 3D.

FIG.3is a side sectional view illustrating schematically a costume head300including a first embodiment of an optical viewfinder assembly350of the present description. The costume head300includes an outer or structural shell or helmet310defining in interior space311for receiving the head306of a human performer/actor305(or wearer of a costume including the head300). The costume's shell310(which is spherical in this non-limiting example) includes an aperture or view slit312, which allows light309from the space outside head300to enter the interior space311of the shell310. In this example, the performer's head306is positioned within the interior space311such that their eyes308are vertically aligned with the view slit312but, due to the large size of the head's shell310the view slit312is separated a relatively large distance, dDepth Sep., in depth from the view slit312(e.g., one to several inches or more separation is common in costume heads).

In this implementation, the optical viewfinder assembly350is disposed or positioned between the view slit312and the expected location of the viewer's eyes308when they are wearing the head300. In typical use, the slit312, the assembly350, and the eye's308are aligned or generally coplanar. The optical viewfinder assembly350is configured to function to move the viewpoint of the eye or eyes308to the location of the view slit312(or its outlet into the space311) or to eliminate the depth separation distance, dDepth Sep., to provide a larger field of view with incoming light309. To this end, the assembly350may include components to form a non-inverting optical relay.

In one embodiment as shown inFIG.3, the assembly350includes a first or aperture lens352positioned at or proximate (e.g., within 1 inch) of the view slit312(or its outlet into the space311) and a second lens354proximate (e.g., within 3 inches) to the eye or eyes308of the performer305. The lenses352,354are arranged to be aligned or to be coaxial and function, in part, to provide focus so that the eye308perceives the light309as if at the aperture/view slit312. Further, the lenses352,354, which may be an objective lens and a field or eye piece lens, respectively, act to “flip-the-flip” (or to flip the flip provided by the first lens352) so that the view provided to the eyes308of the performer305is not inverted (i.e., so the assembly350is a non-inverting optical relay). A separate set of these components may be provided in the assembly350to provide light concurrently to both eyes308of the performer305for stereoscopic viewing of the surrounding environment.

FIG.4is a side sectional view, similar to that ofFIG.3, illustrating schematically a costume head400including a second embodiment of an optical viewfinder assembly460of the present description. The costume head400again includes an outer or structural shell or helmet410defining in interior space411for receiving the head406of a human performer/actor405(or wearer of a costume including the head400). The head shell410(which is spherical in this non-limiting example) includes an aperture or view slit412, which allows light409from the space outside head400to enter the interior space411of the shell410. In this example, the performer's head406is positioned within the interior space411such that their eyes408are vertically offset a distance, dVert. Sep., from the view slit412(or from a horizontal plane extending through the center of the slit412or from the bottom/lower edge of the slit412). Further, as was the case for head300ofFIG.3, due to the large size of the head's shell410, the view slit412is separated a relatively large distance, DDepth.Sep., in depth from the view slit412(e.g., one to several inches or more separation is common in costume heads).

In this implementation, the optical viewfinder assembly460is disposed or positioned between the view slit412and the expected location of the viewer's eyes408when they are wearing the head400. The optical viewfinder assembly460is configured to function to move the viewpoint of the eye or eyes408to the location of the view slit412(or its outlet from the space411) or up and forward to the view slit412(i.e., to eliminate or reduce the depth separation distance, dDepth Sep., and the vertical separation distance, dVert. Sep., to provide a larger field of view with incoming light409. To this end, the assembly450may include components to form a non-inverting optical periscope.

In one embodiment as shown inFIG.4, the assembly460includes a first or aperture lens462positioned at or proximate (e.g., within 1 inch) of the view slit412(or its outlet into the space411), and this may be provided as an objective lens. The assembly460further includes an optical relay that provides the flip of the image from the first/input lens462, and, as shown, the relay may include a pair of spaced-apart 45-degree mirrors464(such as roof pentaprisms or pentamirrors), a downstream field lens466, and a third 45-degree mirror (such as a fold mirror or the like). The non-inverting optical periscope460may further include an eyepiece or output lens469receiving light from the relay and positioned proximate (e.g., within 3 inches) to the eye or eyes308of the performer305, and the lens/eyepiece469may be configured or chosen to re-collimate the light409so that it is sensed by the eye408as being at infinity. A separate set of these components may be provided in the assembly460to provide light concurrently to both eyes408of the performer405for stereoscopic viewing of the surrounding environment.

In some cases, it may be desirable to increase the size of the eye box provided to the performer inside the costume head.FIG.5is a schematic side view of a portion of a costume head500with a third embodiment of an optical viewfinder assembly520of the present description, which may be used in place of the assembly350ofFIG.3. Particularly, the assembly520may be disposed or positioned within a shell of the costume head500so as to be between a view slit/aperture510in the head's shell and an expected location of a performer's eye508(when they are wearing the head500), and, as discussed with reference toFIG.3, this eye location is vertically aligned with the view slit510but offset in depth some distance so that it is desirable to move the view point to coincide with the location of the slit510. Further, though, the optical viewfinder520may be configured to increase the size of the eye box in which the eye508is to be positioned during use of the costume head500.

To achieve these two functional goals, the assembly520includes an inverting prism522positioned at or proximate to the outlet of the view slit/aperture510to receive incoming light506such as light reflected off an object504in the surrounding space (space outside the head500). Downstream of the inverting prism522(e.g., a Pechan-Schmidt or Dove prism), an objective lens524is provided that flips the image and focuses the light from the prism522onto a screen526(e.g., a diffusing screen element such as a field lens with ground glass on an image or focal plane, a transparent OLED to allow presentation of augmenting data/information and/or images to the performer, and the like). An image527is displayed upon or visible by the eye508on the screen526(which may be 1 to 3 inches or more from the eye508), and the screen526is useful for increasing the size of the eye box containing the eye508. An eyepiece or output lens528is provided between the screen526and the location of the eye508to re-collimate the light506from the screen526so that the screen image527appears at infinity. One screen526may be used for both eyes508or the optical components of the assembly520may be duplicated to provide stereoscopic viewing.

FIG.6is a schematic side view of a portion of a costume head600with a fourth embodiment of an optical viewfinder assembly620of the present description, which may be used in place of the assembly460ofFIG.4. The assembly620may be disposed or positioned within a shell of the costume head600so as to be between a view slit/aperture610in the head's shell and an expected location of a performer's eye608(when they are wearing the head600), and, as discussed with reference toFIG.4, this eye location is vertically offset some distance with the view slit610and offset in depth some distance so that it is desirable to move the view point forward and upward to coincide with the location of the slit610. Further, the optical viewfinder620is configured to increase the size of the eye box in which the eye608is positioned during use of the costume head600.

To achieve these functional goals, the assembly or periscopic viewfinder620includes a first or aperture lens622(e.g., an objective lens) positioned at or proximate to the outlet of the view slit/aperture610that initially receives the incoming light606that passes through the slit610(e.g., light reflected off of the surfaces of an object604in the space about the costume head600). The lens622focuses the light onto a first 45-degree mirror624(e.g., a pentaprism or pentamirror), which directs the light downward into the interior head space (e.g., toward the lower vertical position of the eye608). The reflected light passes through a pair of spaced apart lenses626and628to provide proper image orientation and that act to focus the light onto a screen630so as to display/create an image634on the screen630of the object604. Light associated with the displayed image634is then reflected off a second 45-degree mirror636to pass through a fourth or output lens638proximate (e.g., 1 to 3 inches from) the performer's eye608. The lens638acts to re-collimate the light so the image634is perceived by the performer as being at infinity.

In some periscope implementations (e.g., when the eye is vertically offset from the aperture), it is desirable to increase the field of view (fov) without the need for or use of larger optics (or optics taking up more space in the costume head). In this regard,FIG.7is a schematic side view of a portion of a costume head700with a fifth embodiment of an optical viewfinder assembly710of the present description, which may be used in place of the assembly460ofFIG.4or assembly620ofFIG.6. The assembly710may be disposed or positioned within a shell of the costume head700so as to be between a view slit/aperture705in the head's shell and an expected location of a performer's eye708(when they are wearing the head700), and, as discussed with reference toFIGS.4and6, this eye location is vertically offset some distance with the view slit705and offset in depth some distance so that it is desirable to move the view point forward and upward to coincide with the location of the slit705. Further, the optical viewfinder710is configured to increase the fov without larger optics.

To achieve these functional goals, the assembly or periscopic viewfinder710includes a first or aperture lens711(e.g., an objective lens) and a relay720including lenses721,722, and723, an inverting fold-mirror (penta-mirror or the like)724, a scattering screen736, and a mirror eyepiece740including a beam-splitter742and a concave mirror741. The first objective lens711is positioned at or proximate to the outlet of the view slit/aperture705that initially receives the incoming light706that passes through the slit705(e.g., light from the space outside the head700). The lens711focuses the light, from a field of view angle, α, forming an image of the outside scene of width, w, onto an optical relay721,722, and723that directs the light downward into the costume head toward the vertical location of the eye708, and the optical relay720may take the form of lenses721,722, and723with a fold mirror (e.g., a pent-prism)724positioned therebetween.

The optical relay720directs the light from the objective lens711onto a screen736so as to display/create an enlarged image on the screen736(e.g., up to a size 2 w or larger). Additional optional modulators, such as an emissive transparent OLED or an absorbing liquid crystal display (LCD)735may be collocated at the screen736to provide augmented imagery or to provide occlusion effects. Each point on the screen736is scattered through an angle, β′, which is larger than the initial beam angle, β, focused by objective lens711through its small aperture. The scattering from screen736makes each point on screen appear as if it was collected from a larger aperture or objective lens (although with less light intensity).

Light associated with any displayed image is then reflected off another 45-degree beamsplitter742, and it is collimated by concave mirror741so that it passes through the beamsplitter742to the viewer's eye708. The combination of beamsplitter742and concave mirror741form a reflective eyepiece, also known as bird-bath objective. The beamsplitter742may be provided with a polarization selective mirror and a ¼-wave retarder so that polarized light may efficiently pass through the system without light loss associated with a 50/50 beamsplitter. An off-axis parabolic reflector or a refractive lens could also be used as the eyepiece. Reflective mirrors may have smaller focal length to aperture size ratios than refractive lenses and do not suffer from chromatic aberrations.

The light from the small aperture but short focal length objective711forms a small image of width, w, and small divergence, β, but with a large field of view, α. The small width, w, and small divergence, β, allows smaller size optics to relay the image to the screen736. The relay also enlarges the image at screen736to a larger width (e.g., 2 w) but with even smaller divergence, β′. However, the screen scatters the light from each point increasing the divergence to β″. The eyepiece optics740accepts the light from the screen736and collimates the light for the eye708. The reflective eyepiece optics740also folds the light 90 degrees and provides a desirable image flip to provide an upright image to the viewer.

The field of view, α′, provided to the eye708by the eyepiece optics740is related to the image width (e.g., 2 w) on the screen736(or aperture of the eyepiece) and the focal length of the eyepiece optics740. The eyebox (or the region where the eye708may see a complete image) is governed by the aperture, focal length, and divergence. The focal length to aperture ratio (f/#) may be chosen for the eyepiece740to be equal to that of the objective lens711so the field of view, α′, provided to the viewer is the same as the field of view, α′, at the slit705. Since the image at the screen736formed by the relay720(and accepted by the eyepiece740) is larger than the image formed by the objective711, the focal length of the eyepiece740should be proportionally longer so the eyepiece and objective have the same focal length to aperture ratio (f/#) and field of view.

The reflective eyepiece740has a proportionally much larger aperture than the objective711to accept the larger divergence, β″, from the scattering screen736. Hence, the eyepiece740provides a larger eyebox than would be possible without the scattering screen736. The eyepiece740, which is positioned proximate to (e.g., 1 to 3 inches from) the performer's eye708. The eyepiece lens740collimates a wide screen image with a large divergence, which allows the viewer to see a natural wide field of view image in a large eyebox through a compact system.

Although the invention has been described and illustrated with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example, and that numerous changes in the combination and arrangement of parts can be resorted to by those skilled in the art without departing from the spirit and scope of the invention, as hereinafter claimed.

For example, one or more of the optical viewfinders ofFIGS.3-7may be implemented using fold mirrors with optical power (e.g., like a concave mirror or an off-axis parabolic mirror) in place of separate lenses and/or fold mirrors. This would reduce weight and may also reduce chromatic aberrations associated with lenses. As one specific exemplary implementation, the system400ofFIG.4may be modified by combining the lens462and one of the fold mirrors464into a single tilted concave mirror or an off-axis parabolic mirror. A similar modification may be provided to replace or implement the mirror468and the eyepiece469inFIG.4.

The optical viewfinder ofFIGS.3-7is all optical, and the world view through the optics has no latency or other video-related defects (e.g., blooming, saturation, and the like) associated with video see-through camera-based displays. Without electronics, the all-optical viewfinder is robust and future proof. The designed system also has no total optical power so there is no magnification, with a 1:1 image, allowing proper judgment of size and distance (except for the vertical offset from the periscope). The costumed performer can naturally see 3D to judge distances allowing them to comfortably and confidently walk around in and interact with the real world environment. Lack of magnification and the viewing of the scene on a diffusing screen also prevents light sources from being concentrated into the eye.