Article having a birefringent surface for use as a blur filter

Abstract

An optical low pass filter or blur filter, and method of making the filters, using an article having a birefringent surface for refracting incoming light when used with an image sensor. The birefringent surface of the article, such as a film, is structured or tilted such that, when the blur filter is placed within an optical path between a lens and the image sensor, the birefringent surface causes refraction of a light signal in the optical path into multiple light signals each being incident upon different sub-pixels within the pixels in the image sensor to prevent or reduce artifacts, such as undesirable color moire effects, in the resulting digital image.

Description

technical field

[0001] The present invention relates to an article having a birefringent surface inclined with respect to an optical path, and a method of manufacturing the article, wherein the article is used as a blur filter for use with an image sensor. The article has a surface having at least one electromagnetically anisotropic birefringent geometric feature for refracting an electromagnetic signal, such as an optical signal. Background technique

[0002] Photo color distortion and color fringing that occur in digital imaging are caused by the interaction between the image mode and the image color sensor mode. These adverse effects are produced by sharp edges (indicating abrupt changes in color) and repetitive image features at the scale of a single pixel sensor. Since the real-world pattern spacing will never exactly match that of the digital sensor pattern, overly heavy colors will vary across the space of the image with the magnitude of the phase difference between ...

Examples

Embodiment 1

[0135] Example 1 - Preparation of Oriented Microstructured Films

[0136] Polyethylene terephthalate (PET) with an intrinsic viscosity (I.V.) of 0.74 (available from Eastman Chemical Company, Kingsport, Tennessee, USA) was used in this example.

[0137] The PET pellets were dried to remove residual moisture and loaded into the extruder hopper under a nitrogen purge. PET was extruded in the extruder and the melter assembly connected thereto up to a temperature profile of 232°C to 282°C at the die (where the die was set at 282°C). The pressure of the melter assembly is continuously monitored and averaged at the last of a plurality of monitoring locations located along the melter assembly, and the die is then brought in close proximity to the tool on which the polymer film will be formed (the tool Simultaneously, the opposite first surface of the film is structured).

[0138] The tool was a structured ribbon of nickel alloy of unknown composition (manufactured by 3M Company) wi...

Embodiment 2

[0145] Embodiment 2--double-layer microstructured fuzzy filter

[0146] To create the microstructure in film 1, the unoriented (amorphous state) cast PEN material was directly cut into the following dimensions by diamond turning on a lathe before stretching: pitch of prisms on one surface of the film is about 89 microns, the apex angle is about 86°, one side of its cross-sectional triangle is inclined at 4° with respect to the horizontal line of the film substrate, and the side opposite to the side is inclined at 0° with respect to the vertical line, and Its depth is 6.5 microns. The obtained film was uniaxially stretched under the condition that the stretch ratio was 3, and the prismatic replication surface had the following dimensions and characteristics after stretching: the pitch was 49.8 microns, the apex angle was about 86°, and its cross-section was triangular. One side was inclined at 4° with respect to the horizontal of the film substrate and the opposite side was in...

Embodiment 3

[0152] Example 3 - two-dimensional (2D) controllable beam splitting

[0153] Before stretching, the film sample had a prismatic surface structure with an apex angle of about 90°, one side of its cross-sectional triangle inclined at 30° with respect to the horizontal line of the film substrate, and The opposite side is inclined at 30° relative to the vertical, and the prism pitch is 25 microns.

[0154] The film sample is uniaxially stretched under the condition that the uniaxial stretching ratio is 6, and the prismatic replication surface obtained after stretching has the following dimensions and characteristics: the pitch is 14.1 microns, and the apex angle is about 92°, which One side of the cross-sectional triangle was inclined at 28° relative to the horizontal of the film substrate and the opposite side was inclined at 30° relative to vertical, and had a depth of about 3.6 microns. Refractive index was measured on the back side of the stretched film using a Metricon prism...

technical field

[0001] The present invention relates to an article having a birefringent surface inclined with respect to an optical path, and a method of manufacturing the article, wherein the article is used as a blur filter for use with an image sensor. The article has a surface having at least one electromagnetically anisotropic birefringent geometric feature for refracting an electromagnetic signal, such as an optical signal. Background technique

[0002] Photo color distortion and color fringing that occur in digital imaging are caused by the interaction between the image mode and the image color sensor mode. These adverse effects are produced by sharp edges (indicating abrupt changes in color) and repetitive image features at the scale of a single pixel sensor. Since the real-world pattern spacing will never exactly match that of the digital sensor pattern, overly heavy colors will vary across the space of the image with the magnitude of the phase difference between ...

Examples

Embodiment 1

[0135] Example 1 - Preparation of Oriented Microstructured Films

[0136] Polyethylene terephthalate (PET) with an intrinsic viscosity (I.V.) of 0.74 (available from Eastman Chemical Company, Kingsport, Tennessee, USA) was used in this example.

[0137] The PET pellets were dried to remove residual moisture and loaded into the extruder hopper under a nitrogen purge. PET was extruded in the extruder and the melter assembly connected thereto up to a temperature profile of 232°C to 282°C at the die (where the die was set at 282°C). The pressure of the melter assembly is continuously monitored and averaged at the last of a plurality of monitoring locations located along the melter assembly, and the die is then brought in close proximity to the tool on which the polymer film will be formed (the tool Simultaneously, the opposite first surface of the film is structured).

[0138] The tool was a structured ribbon of nickel alloy of unknown composition (manufactured by 3M Company) wi...

Embodiment 2

[0145] Embodiment 2--double-layer microstructured fuzzy filter

[0146] To create the microstructure in film 1, the unoriented (amorphous state) cast PEN material was directly cut into the following dimensions by diamond turning on a lathe before stretching: pitch of prisms on one surface of the film is about 89 microns, the apex angle is about 86°, one side of its cross-sectional triangle is inclined at 4° with respect to the horizontal line of the film substrate, and the side opposite to the side is inclined at 0° with respect to the vertical line, and Its depth is 6.5 microns. The obtained film was uniaxially stretched under the condition that the stretch ratio was 3, and the prismatic replication surface had the following dimensions and characteristics after stretching: the pitch was 49.8 microns, the apex angle was about 86°, and its cross-section was triangular. One side was inclined at 4° with respect to the horizontal of the film substrate and the opposite side was in...

Embodiment 3

[0152] Example 3 - two-dimensional (2D) controllable beam splitting

[0153] Before stretching, the film sample had a prismatic surface structure with an apex angle of about 90°, one side of its cross-sectional triangle inclined at 30° with respect to the horizontal line of the film substrate, and The opposite side is inclined at 30° relative to the vertical, and the prism pitch is 25 microns.

[0154] The film sample is uniaxially stretched under the condition that the uniaxial stretching ratio is 6, and the prismatic replication surface obtained after stretching has the following dimensions and characteristics: the pitch is 14.1 microns, and the apex angle is about 92°, which One side of the cross-sectional triangle was inclined at 28° relative to the horizontal of the film substrate and the opposite side was inclined at 30° relative to vertical, and had a depth of about 3.6 microns. Refractive index was measured on the back side of the stretched film using a Metricon prism...

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