Predictive autofocusing system
A system for providing a predictive autofocus prior to capturing an image of an iris of a subject. A sequence of images of the subject may be taken with a visible light sensitive camera. A speed and/or location of the subject may be estimated from the images. An encounter may be when the subject is within focus of the camera or, in other words, a focus distance and subject distance coincide. The focus may be determined in accordance with an intensity variance determination of the subject in the image, and more particularly of a subject's eye within a window of an image. Upon an encounter, an image of the iris of the eye may be captured with an infrared sensitive camera.
1. A method for autofocusing comprising:
taking a sequence of images of a subject with a camera;
extracting image data from a window surrounding an eye of the subject in each image, where the image data includes an intensity variance of an area in each image;
analyzing the image data from each image in real time;
determining the subject's position and speed based on the image data, where a change of intensity variance between images of the sequence of images is used to determine the subject's speed;
estimating a first time of an encounter of the subject from the position and speed determined from the images;
computing one or more encounters subsequent to the first time of an encounter; and
taking an image of the subject at one or more times of an encounter; and
wherein an encounter indicates that at least a portion of the subject is within a focus of the camera.
2. The method of claim 1 , wherein computing an encounter is based on intensity variance of an area in the window centered on the eye.
3. The method of claim 2 , wherein an encounter is achieved when either just the focus or the subject moves, or both the focus and the subject move.
4. The method of claim 3 , wherein upon at least one encounter, the camera takes an image of an iris of the eye.
5. The method of claim 4 , wherein the image of the iris is taken under infrared light.
6. The method of claim 5 , wherein the camera comprises one or more sensors for taking the sequence of images of a subject and for taking the image of an iris.
7. A predictive autofocusing system comprising:
a camera for taking images of a subject; and
a processor connected to the camera; and
wherein the processor is configured to process each of a series of images from the camera individually and in real time, the processor is configured to analyze the images and determine a position and speed of the subject, and to estimate the time of a future encounter in which the subject will be within a focus of the camera, based on the position and speed of the subject; and
wherein the processor is configured to extract intensity variance data from an area of an eye of the subject in each image and the speed of the subject is determined based on the intensity variance data extracted from each image.
8. The system of claim 7 , wherein the processing of images is for determining intensity variance of an area of an eye of the subject to determine whether an amount of focus of the eye in the images is sufficient for an encounter.
9. The system of claim 7 , wherein upon an encounter, an image of an iris of an eye of the subject can be captured by the camera.
10. The system of claim 9 , wherein an encounter is achieved by movement of either the subject or the focus of the camera, or of both the subject and a focus of the camera.
11. The system of claim 9 , wherein the camera is for taking images of the subject in visible light for focusing, and for capturing an image of the iris in infrared light.
12. A method for focusing comprising:
taking images with a camera of a subject, where each image has image data of a window encompassing an eye of the subject and the image data comprises an intensity variance of an imaged feature of the subject;
estimating a position and/or speed of the subject relative to the camera from the intensity variance of the imaged feature of the subject in each of the images;
computing a time of an encounter from the position and/or speed of the subject relative to the camera, wherein the encounter is at a time when the subject will be within focus of the camera; and
taking an image of the subject upon the time of an encounter.
13. The method of claim 12 , wherein the intensity variance of the imaged feature of the subject is an intensity variance proximate to the eye of the imaged subject.
14. The method of claim 13 , wherein an encounter is indicated when the intensity variance is at a certain level.
15. The method of claim 14 , wherein an image of the eye is acquired during an encounter.
16. The method of claim 15 , wherein the images having the image data are taken in visible light and the image of the eye is taken in infrared light.
17. The method of claim 14 , further comprising deciding whether to move the focus to obtain an encounter, or have the subject move within a depth of the focus, or both.