glare stop, digital sundial, black hole fence

A window that blocks sunlight but not daylight; A sundial with signs and seasons, months, days, hours, minutes, in digital if you like; An open entryway that keeps light and sound, out and in and trans... All true: Inventions on a theme of sunbeams...

Photochromic glare-stop windows:

Ca 1979, I pondered a theory-extension to the common doublesided complementary-aligned picket fence whereon the slats of one side obscure the openings on the other, and vice versus, so that in alignment the full fence obscured view of the opposite side, but allowed air to pass breezily.

Extending that to its generality---

A window pane with one side a 50% "random" mask (random being any discrete pointillation [pixelation] function having fairly small-scale near-uniform obscuration density of 50% at all angles of view), and the opposite side a high-contrast photochromic sheet, can effectively block intense sunlight beams: each beam filament strafing through the mask thence actuating the photochromic darkening response in its corresponding point on the far side: thus blocking itself---while less intense light at other angles does not so actuate the photochromochemical response: therefor passing through uninhibited (albeit reduced by the total average double-masking to 25%).

In the specific case of sunbeams which on a clear day spread 0.009 rad (0.5 deg=0.6 grad) the pane must be much thinner than 1.000/0.009 the average pointillation mesh size, while the mesh size is lower bounded by optical diffraction, to be overall effectual. Which for the typical sun-relieved occular pupil 3-5 mm, limits window thickness below 10 cm (1 mm mesh) and mesh above 0.01 mm (10x red photon wavelength)---a fair range of standard utility window-thin thickness, 1 mm to 10 cm. NB: If designed for interplanetary use nearer the sun (where it would be more needed) the angular constraint is tighter.

For suntrap glasses, the photochromic electrochemistry must be extremely fast-acting, else each slight movement results in apparent sunburst "solarization".

More practical applications (for slower photochromochemistry) might include "skylight" and southern exposure "picture" windows on homes, employment facilities, space-station Earth-presence windows, vehicle windshields, cars, trucks, aircraft and space-shuttles (the latter being the original intent in design).

Aside the advantage of sunbeam-blocking, suntrap windows may offer advantage against the glare of night-use vehicle headbeams---both stationary and moving. And in special applications may also offer collateral advantage against white-out conditions where the photochromochemistry can be so selected to lesser-responsed obscuration.

Final details to consider in application, are that surrounding any bright source in view is it's penumbra, by angle about the ratio of window thickness to mesh---thus a thicker suntrap is preferred, to minimize the penumbral detilieration of the image.

[detilieration: the manual painting technique of applying cropped overlayers of dark film "tiles" to effect apparent shadows; in lieu of mixing darker paints]

[pointillation: the manual painting technique of applying points of paint, in lieu of brush strokes, to compose a larger image---(cf color video pixelation)]

A sundial with signs and seasons, months, days, hours, minutes:

An artistic (artifact) utilization of similar theory is the construction of a year-round sundial, where a transparent optical (eg. thick window plate) can be hologrammed (here using sunbeam alignment instead of photowavelength properties) to create a projected image beyond it, reading out the month, date, hours, minutes, holidays, in any musable format, digital or analog, even special video-image....

Its alignment is technically challenging for precision and accuracy---and months do crossover (slightly summerward in the northern hemisphere---an asymmetry due to combined sun-Earth distance and Earth inclination to the ecliptic [apparent sun-path plane]---the relatively slight lesser difference in distance at latitudes may be insignificant compared to overall sun-Earth distance in this particular application).

black hole fenceBlack hole fence:

Recalling the arcane statement, "a photon passing through one focus of an elliptical mirror, passes through the other too"

A useful wall construction blocking the passage of light and sound, seeing and hearing, but not persons and airflow, things straight-ballistic but not things turn-controlled, -and is itself-not dark,- is a mirrored entrance that reflects -all- light back to the same side it comes... the bidirectional equivalence of mirroring isolates all light from the other side, and as well that inside, the wall... sort of a tri-ambi/'amtri'/'antri'-trap, light-rift....

Solving the equation for a ballpark fence opening allowing players but not balls through, and applying it to light as well, simplifies to requiring balls from one end-post of the fence-opening to reflect to the opposite next end-post;-- balls in-between reflect back-in-between and thus all balls entering are entrained to leave the same side... An equation is the long-side half ellipse with its end-posts at adjacent foci. This is then chained alternately-in-out-half-ellipses convex mirrored (one in-or-out-side mirrored, suffices: its unused and convex sides may be decorative). The 'ideal' focal-spread allows two-or-more persons side-by-side-or-passing entering/exiting i.e. e ≥ (f=1)/(a=2) = 0.5.

Persons can then enter between the end-posts and turn about an 'S' to exit past the end-post set of the adjacent counter side.

(It is also noteworthy that the mirror bays are cross-traps: A ball thrown as-not-out from any mirror bay reaches the next and successively other mirror bays, chaining-along.)

Practical uses, include, theater foyer-exits, veranda walls, light-efficient open connected halls, by floor-to-ceiling colonnades; fences, LiD-fusion chambers,... needing keeping straight-ballistic objects, light, radiant-heat, sound, balls, atoms, in or out without obstructing passage; Cross-trapping uses include transitioning prep-light-and-sound e.g. accustoming red/annunciating 'welcome to the darkroom'...

(Comparative note: From the ellipse here-used to create a "black hole" in a fence, comes the same equation for one early construction of the hydrogen fusion-detonation device, focusing the output of a fission-detonation device placed at one focus of an ellipsoid, onto a fusion core placed at the other. [There are numerous more constructions])

Such construction, blocks sound fairly well, and light verily well, but wave action allows refractions around edges and corners... still, useful, for theaters, operations-rooms, etc.

A premise discovery under the title,

Grand-Admiral Petry
'Majestic Service in a Solar System'
Nuclear Emergency Management

[1979] 2002, 2018ed