Holographic Polymer Dispersed Liquid Crystal Diffraction Grating
A camera system includes an image sensor assembly and a tunable optical element. The tunable optical element is a holographic polymer dispersed liquid crystal diffraction grating of alternating PDLC layers. The diffraction grating is tunable by applying an electric field to the optical element via a control element. The control element applies a voltage differential to the optical element inducing an electric field which changes the polarization of the PDLC within the optical element. The refractive index of the holographic grating is dependent on the polarization of the liquid crystals within the optical element. Applying the electric field to the tunable element changes the optical properties of the grating.
1 . A camera system including
an image sensor assembly configured to capture images, the image sensor assembly centered about an optical axis;
a tunable optical element for focusing light onto the image sensor assembly, the tunable optical element a substantially rectangular block having a bottom side and a top side centered about the optical axis comprising:
a first plurality of layers of a first material, wherein a first polarization of the first material is controllable by an applied electric field, each layer of the first plurality of layers having a first refractive index controllable by the first polarization of the first material in the first plurality of layers,
a second plurality of layers of a second material, wherein each layer of the second plurality of layers has a second refractive index controllable by a second polarization of the second material in the second plurality of layers,
wherein the first and second plurality of layers are alternately layered in a layer stack of the tunable optical element, and
wherein each of the first and the second plurality of layers have at least one respective arc-shaped cross sections having respective peaks aligned with the optical axis; and
a first control element coupled to the tunable optical element for applying a voltage differential to the first plurality of layers, the voltage differential creating the electric field controlling the first refractive index of the first plurality of layers of the tunable optical element.
2 . The camera system of claim 1 ,
wherein the second polarization of the second plurality of layers is controllable by a second applied electric field; and
wherein the camera system further comprises a second control element coupled to the tunable optical element for applying a second voltage to the second plurality of layers, the second voltage differential creating the second applied electric field controlling the second refractive index of second plurality of layers of the tunable optical element.
3 . The camera system of claim 1 wherein the first control element is coupled to the first plurality of layers and not the second plurality of layers.
4 . The camera system of claim 1 wherein the first control element is coupled to two opposing surfaces of the tunable optical element.
5 . The camera system of claim 1 wherein the first control element is a sheet resistor.
6 . The camera system of claim 1 wherein the first material of the first plurality of layers is a polymer dispersed liquid crystal.
7 . The camera system of claim 2 wherein the second material of the second plurality of layers is a polymer dispersed liquid crystal.
8 . The camera system of 1 comprising a lens tube, the lens tube comprising optical elements that focus light from external the camera body onto the image sensor.
9 . The camera system of 8 wherein the tunable optical element is coupled to the lens tube.
10 . The camera system of 1 wherein the tunable optical element is a diffraction grating.
11 . The camera system of 1 wherein the tunable optical element transmits a first wavelength of light and reflects a second wavelength of light.
12 . The camera system of 1 wherein the tunable optical element transmits light parallel to the optical axis while reflecting light not parallel to the optical axis.
13 . The camera system of 1 wherein the tunable optical element has a first set of optical characteristics when the first voltage is applied to the tunable optical element and a second set of optical characteristics when a different voltage is applied to the tunable optical element.
14 . A tunable optical element comprising:
a first plurality of layers of a first material, wherein a first polarization of the first material is controllable by an applied electric field, each layer of the first plurality of layers having a first refractive index controllable by the first polarization of the first material in the first plurality of layers;
a second plurality of layers of a second material, wherein each layer of the second plurality of layers has a second refractive index controllable by a second polarization of the second material in the second plurality of layers,
wherein the first and second plurality of layers are alternately layered in a layer stack of the tunable optical element;
wherein the tunable optical element that is substantially rectangular block having a bottom side, and a top side centered about an optical axis;
wherein each of the first and the second plurality of layers have at least one respective arc-shaped cross sections having respective peaks aligned with the optical axis; and
a first control element coupled to the tunable optical element for applying a voltage differential to the first plurality of layers, the voltage differential creating the electric field controlling the first refractive index of the first plurality of layers of the tunable optical element.
15 . The tunable optical element of claim 14 ,
wherein the second polarization of the second plurality of layers is controllable by a second applied electric field; and
wherein the camera system further comprises a second control element coupled to the tunable optical element for applying a second voltage to the second plurality of layers, the second voltage differential creating the second applied electric field controlling the second refractive index of second plurality of layers of the tunable optical element.
16 . The tunable optical element of claim 14 wherein the tunable optical element transmits light parallel to the optical axis while reflecting light not parallel to the optical axis.
17 . A camera system including
an image sensor assembly configured to capture images, the image sensor assembly centered about an optical axis;
a tunable optical element for focusing light onto the image sensor assembly, the tunable optical element a substantially rectangular block having a bottom side, and a top side centered about the optical axis comprising:
a first plurality of layers of a first material, wherein a first refractive index of the first material is controllable by an applied electric field, each layer of the first plurality of layers having the first refractive index;
a second plurality of layers of a second material, wherein each layer of the second plurality of layers has a second refractive index;
wherein the first and second plurality of layers are alternately layered in a layer stack of the tunable optical element, and
wherein each of the first and the second plurality of layers have at least one respective arc-shaped cross sections having respective peaks aligned with the optical axis; and
a first control element coupled to the tunable optical element for applying a voltage differential to the first plurality of layers, the voltage differential creating the electric field controlling the first refractive index of the first plurality of layers of the tunable optical element.
18 . The camera system of claim 17 ,
wherein the second refractive index of the second plurality of layers is controllable by a second applied electric field; and
wherein the camera system further comprises a second control element coupled to the tunable optical element for applying a second voltage to the second plurality of layers, the second voltage differential creating the second applied electric field controlling the refractive index of the second plurality of layers of the tunable optical element.
19 . The camera system of claim 17 ,
wherein the first material has a first polarization associated with the first refractive index and the applied electric field controls the first polarization.
20 . The camera system of claim 18 ,
wherein the second material has a second polarization associated with the second refractive index and the second applied electric field controls the second polarization.