Fixed focus camera with lateral sharpness transfer
View Patent ↗A lens includes a depth of field (“DOF”) range and a macro range. The macro range is distinct and separate from the DOF range. The macro range is a near field relative to the DOF range. The DOF range provides a first field of view (“FOV”) while the macro range provides a second FOV that is smaller than the first FOV within the DOF range. The lens transfers sharpness from a peripheral viewing region within the macro range into a central viewing region within the macro range.
1. A method of fabricating a lens for a camera system, comprising:
specifying first mean transfer function (“MTF”) requirements for the lens within a depth of field (“DOF”) range of the lens along a depth axis;
specifying second MTF requirements for the lens outside of the DOF range and within a macro range of the lens along the depth axis, wherein the macro range is distinct and separate from the DOF range, wherein the macro range is a near field relative to the DOF range; and
fabricating a lens having a physical shape or pattern according to the first and second MTF requirements such that the lens has a second in-focus field of view (“FOV”) within the macro range that is smaller than a first in-focus FOV within the DOF range by transferring sharpness from a peripheral viewing region within the macro range into a central viewing region within the macro range.
2. The method of claim 1 , wherein the second MTF requirements specified within the macro range decrease with increasing viewing angle.
3. The method of claim 2 , wherein the first MTF requirements specified within the DOF range are flatter than the second MTF requirements and decrease substantially less than the second MTF requirements with increasing viewing angle.
4. The method of claim 1 , wherein the second MTF requirements are selected such that the lens has sufficient sharpness within the second in-focus FOV of the macro range to facilitate at least one of optical character recognition (“OCR”), bar code scanning, or image recognition.
5. The method of claim 1 , wherein the macro range extends along the depth axis from approximately 20 cm to 40 cm offsets from the lens.
6. The method of claim 5 , wherein the DOF range extends along the depth axis from approximately 60 cm to infinity offsets from the lens.
7. The method of claim 1 , wherein the lens comprises an aspheric refractive lens.
8. The method of claim 1 , wherein the lens comprises a diffractive lens.
9. The method of claim 1 , wherein the lens comprises a fixed focus lens.
10. A non-transitory computer-accessible storage medium that provides instructions that, when executed by a computer, will cause the computer to perform operations for designing a lens for a fixed focus camera system, the operations comprising:
receiving first mean transfer function (“MTF”) requirements for the lens within a depth of field (“DOF”) range of the lens along a depth axis;
receiving second MTF requirements for the lens outside of the DOF range and within a macro range of the lens along the depth axis, wherein the macro range is distinct and separate from the DOF range, wherein the macro range is a near field relative to the DOF range; and
calculating coefficients of an equation describing a physical shape or a pattern for the lens that satisfies the first and second MTF requirements such that the lens has a second in-focus field of view (“FOV”) within the macro range that is smaller than a first in-focus FOV within the DOF range by transferring sharpness from a peripheral viewing region within the macro range into a central viewing region within the macro range.
11. The non-transitory computer-accessible storage medium of claim 10 , wherein the second MTF requirements specified within the macro range decrease with increasing viewing angle.
12. The non-transitory computer-accessible storage medium of claim 11 , wherein specifying the first MTF requirements for the lens within the DOF range of the lens along the depth axis comprises:
specifying a substantially constant MTF over the first in-focus FOV within the DOF range.
13. The non-transitory computer-accessible storage medium of claim 10 , wherein the second MTF requirements are selected such that the lens has sufficient sharpness within the second in-focus FOV of the macro range to facilitate at least one of optical character recognition (“OCR”), bar code scanning, or image recognition.
14. The non-transitory computer-accessible storage medium of claim 10 , wherein calculating the coefficients of the equation describing the physical shape or the pattern for the lens comprises maximizing a Merit Function describing the first and second MTF requirements.