Systems and methods for minimizing aberrating effects in imaging systems
A biometric optical recognition system includes optics, including a wavefront coding mask, for imaging a wavefront of object to be recognized to an intermediate image, and a detector for detecting the intermediate image. A modulation transfer function detected by the detector contains no zeros such that subsequent task based image processing recognizes the object. A biometric recognition system includes optics for imaging a wavefront of an object to be recognized to a first intermediate image, and a detector for detecting the first intermediate image. The optics include a phase changing element configured for modifying the wavefront such that a modulation transfer function characterizing detection of the first intermediate image contains no zeros such that subsequent task based image processing recognizes the object. In an optical imaging system that includes a solid state detector, a phase-modifying element reduces reflected power from electromagnetic energy incident upon the detector without introducing aberrations.
1. A biometric recognition system, comprising:
optics for imaging a wavefront of an object to be recognized to a first intermediate image; and
a detector for detecting the first intermediate image,
wherein the optics includes a phase changing element configured for modifying the wavefront such that a modulation transfer function characterizing detection of the first intermediate image contains no zeros such that subsequent task based image processing recognizes the object.
2. The system of claim 1 , further comprising a decoder, connected with the detector, for implementing the task based image processing.
3. The system of claim 2 , wherein the decoder is operable as an all-pass filter.
4. The system of claim 2 , wherein the decoder is operable as an attenuation filter for magnification of at least one.
5. The system of claim 1 , wherein the optics consist of a single optical element.
6. The system of claim 1 , wherein the first intermediate image comprises features of the object reformatted by a spatial blurring function implemented by the phase changing element.
7. The system of claim 1 ,
the first intermediate image being formed with the object at a first distance from the system, a second intermediate image being formed with the object at a second distance from the system,
wherein a Hamming distance between the first and second intermediate images is less than a Hamming distance between the first and second intermediate images formed by an equivalent system but without the phase changing element, of the object, at the first and second distance from the system.
8. The system of claim 1 , wherein a Hamming distance, between the first intermediate image and a second intermediate image formed by the system of a second object, is greater than a Hamming distance between intermediate images of the first and second objects formed by an equivalent system without the phase changing element.
9. The system of claim 1 , the phase changing element comprising a selected one of circularly symmetric optics, constant profile path optics and rectangularly separable optics.
10. The system of claim 1 , the phase changing element comprising a phase function of the form P(r,theta)=Σa i r i cos(w i theta+phi i ).