Phase gratings with odd symmetry for lensed optical sensing
AssigneeRambus Inc.
InventorsPatrick R. Gill, David G. Stork
Life of this patent
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Abstract
A sensing device with an odd-symmetry grating projects near-field spatial modulations onto a closely spaced photodetector array. Due to physical properties of the grating, the spatial modulations are in focus for a range of wavelengths and spacings. The spatial modulations are captured by the array, and photographs and other image information can be extracted from the resultant data. Used in conjunction with a converging optical element, versions of these gratings provide depth information about objects in an imaged scene. This depth information can be computationally extracted to obtain a depth map of the scene.
Claims21
A camera for sensing incident light within a wavelength band of interest, the camera comprising:
- an optical element operable to converge the incident light;
- an array of pixels spaced from the optical element and defining a focal plane in a path of the converged incident light;
- and
- a phase grating in the path of the converged incident light and spaced from the array of pixels to cast an interference pattern on the array of pixels, the phase grating spaced from the array of pixels by more than fifteen microns and including:
- boundaries of odd symmetry separating stepped features on opposite sides of each boundary, the stepped features on the opposite sides of each boundary offset from the array by half of a wavelength within the wavelength band of interest, plus an integer multiple of the wavelength, to produce curtains of destructive interference at the array of pixels.
A method of imaging a scene comprised of objects at different distances, the method comprising:
- passing light from the objects through a converging optical element and onto a diffractive optical element, the light from points on the objects at different distances producing blur spots of different sizes on the diffractive optical element;
- passing the blur spots of different sizes through the diffractive optical element, each blur spot producing a pattern of spatial modulations sized in proportion a defocus of the blur spot;
- and
- computationally inverting the spatial modulations to produce an image of the scene.
An imaging device comprising:
- a converging optical element in a path of incident light in a wavelength band of interest;
- a phase grating defining a transverse plane to receive the incident light from the converging optical element, the phase grating including:
- first segments to induce first phase delays of the incident light;
- second segments between the first segments, the second segments to induce second phase delays of the incident light, the second phase delays differing from the first phase delays by half a wavelength of light within the wavelength band of interest;
- wherein:
- adjacent pairs of the first and second segments of a first width W1 define lines of symmetry;
- pairs of the first segments of the first width W1 are separated by ones of the second segments of a second width W2 greater than the first width W1;
- and
- pairs of the second segments of the first width W1 are separated by ones of the first segments of the second width W2.
Dependencies are inferred from the claim text.