# US 10,119,679 B2 · Freeform optical surface for producing sharp-edged irradiance patterns

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- Number: US 10,119,679 B2
- Document ID: US10119679B2
- Status: Granted
- Kind: B2
- Application number: 15/296,162
- Filed: 2016-10-18
- Published: 2018-04-19
- Granted: 2018-11-06
- Earliest claimed: 2016-10-18
- Assignees: Mitsubishi Electric Research Laboratories, Inc.
- Applicants: Mitsubishi Electric Research Laboratories, Inc.
- Inventors: Matthew Brand
- Web page: https://patentgrep.com/patent/US10119679B2

## CPC

- G02B 27/0927: {Systems for changing the beam intensity distribution, e.g. Gaussian to top-hat}
- F21V 5/04: of lens shape
- G02B 3/0037: {characterized by the distribution or form of lenses}
- G02B 3/0043: {Inhomogeneous or irregular arrays, e.g. varying shape, size, height}
- G02B 27/0012: {Optical design, e.g. procedures, algorithms, optimisation routines}
- F21V 5/08: producing an asymmetric light distribution
- F21Y 2115/10: Light-emitting diodes [LED]
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- F21V: FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED

## Abstract

An optic has a freeform optical surface transforming incident light emitted by a zero-étendue light source to form an irradiation pattern including a caustic of light rays focused along a curve. The transverse thickness of the illuminated curve is determined by the diffraction limit of the wavelength of the incident light.

## Claims

### Claim 1

An optic having a freeform optical surface transforming incident light emitted by a zero-étendue light source to form an irradiation pattern including a caustic of light rays focused along a curve, wherein the transverse thickness of the illuminated curve is determined by the diffraction limit of the wavelength of the incident light.

### Claim 2 (depends on 1)

The optic of claim 1, wherein the curve extends in a plane over the entire length of the curve.

### Claim 3 (depends on 1)

The optic of claim 1, wherein the curve extends through a three-dimensional space, such that the curve includes at least two segments lying on different planes.

### Claim 4 (depends on 1)

The optic of claim 1, wherein the curve lies on a surface of a three-dimensional geometrical object.

### Claim 5 (depends on 1)

The optic of claim 1, wherein the irradiation pattern includes one or multiple curves forming at least one or a combination of a pictogram, an ideogram, a sign, a glyph, and a word.

### Claim 6 (depends on 1)

The optic of claim 1, wherein the irradiation pattern includes one or multiple curves forming an asymmetrical low-high beams pattern for illumination of a road surface.

### Claim 7 (depends on 1)

The optic of claim 1, wherein the freeform optical surface is formed by a plurality of shapes adjusted to balance irradiance of the light on each part of the irradiation pattern.

### Claim 8 (depends on 1)

The optic of claim 1, wherein the freeform optical surface is formed by a combination of a plurality of shapes, wherein protuberance of the shapes increases with respect to a distance to an optical axis of the optic.

### Claim 9 (depends on 1)

The optic of claim 1, wherein the curve includes a sequence of segments, each segment has a uniform irradiance along its length.

### Claim 10 (depends on 9)

The optic of claim 9, wherein two neighboring segments have different irradiance.

### Claim 11 (depends on 10)

The optic of claim 10, wherein all segments have an equal length.

### Claim 12 (depends on 1)

The optic of claim 1, wherein the freeform optical surface is formed by a surjection mapping sheets of a space surrounding the optical surface to corresponding points on the curve using a Fermat invariant governing the propagation of the incident light.

### Claim 13 (depends on 1)

A luminaire, comprising:
the optic of claim 1; and
a spatially extended light source arranged in the luminaire to emit the light onto the freeform optical surface to produce the irradiation pattern with the curve with increased width or depth and with sharp-edge boarders preventing spilling of the light outside of the irradiation pattern.

### Claim 14 (depends on 13)

The luminaire of claim 13, wherein the spatially extended light source includes a light-emitting diode (LED).

### Claim 15

A method for fabricating an optic, comprising:
determining a freeform optical surface transforming incident light into an irradiation pattern including a caustic of light rays focused along a curve, wherein, when the freeform optical surface is illuminated by a zero-étendue light source, wherein the transverse thickness of the illuminated curve is the size of an Airy disk at the wavelength of the incident light, and wherein, when the freeform optical surface is illuminated by a spatially extended light source, the curve has sharp-edge boarders preventing spilling of the light outside of the irradiation pattern; and
fabricating the optic having the freeform optical surface.

### Claim 16 (depends on 15)

The method of claim 15, wherein the determining comprises:
determining the freeform optical surface by a surjection mapping sheets of a space surrounding the curve with corresponding points on the curve using a Fermat invariant governing the propagation of the incident light.

### Claim 17 (depends on 15)

The method of claim 15, wherein the irradiation pattern includes multiple curves forming at least one or a combination of a pictogram, an ideogram, a sign, and a glyph.

### Claim 18 (depends on 15)

The method of claim 15, wherein the freeform optical surface is formed by a plurality of shapes adjusted to balance irradiant of the light on each part of the irradiation pattern.

### Claim 19 (depends on 18)

The method of claim 18, wherein the irradiance of the irradiation pattern is uniform.

### Claim 20 (depends on 15)

The method of claim 15, further comprising:
determining the curve by an image-processing a desired irradiation pattern, the image processing includes one or combination of a deblurring, a thresholding, a morphological skeletonization, and a contour-extraction operation.