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Title:
CONTINUOUS ELECTRONIC ZOOM FOR AN IMAGING SYSTEM WITH MULTIPLE IMAGING DEVICES HAVING DIFFERENT FIXED FOV
Document Type and Number:
WIPO Patent Application WO/2010/116367
Kind Code:
A1
Abstract:
A method for continuous electronic zoom in a computerized image acquisition system, the system having a wide image acquisition device and a tele image acquisition device having a tele image sensor array coupled with a tele lens having a narrow FOV, and a tele electronic zoom. The method includes providing a user of the image acquisition device with a zoom selecting control, thereby obtaining a requested zoom, selecting one of the image acquisition devices based on the requested zoom and acquiring an image frame, thereby obtaining an acquired image frame, and performing digitally zoom on the acquired image frame, thereby obtaining an acquired image frame with the requested zoom. The alignment between the wide image sensor array and the tele image sensor array is computed, to facilitate continuous electronic zoom with uninterrupted imaging, when switching back and forth between the wide image sensor array and the tele image sensor array.

Inventors:
GOLAN CHEN (IL)
KIPNIS BORIS (IL)
Application Number:
PCT/IL2010/000281
Publication Date:
October 14, 2010
Filing Date:
April 06, 2010
Export Citation:
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Assignee:
NEXTVISION STABILIZED SYSTEMS (IL)
GOLAN CHEN (IL)
KIPNIS BORIS (IL)
International Classes:
G02B15/15
Foreign References:
US20060139475A12006-06-29
US20060023074A12006-02-02
US20060125937A12006-06-15
US6611289B12003-08-26
US20050030407A12005-02-10
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Claims:
WHAT IS CLAIMED IS:

I . In a computerized image acquisition system, having multiple optical image acquisition devices each with a fixed field of view (FOV), a method for continuous electronic zoom comprising the steps of: a) providing a first image acquisition device including: i) a first image sensor array coupled with a first lens having a first FOV; and ii) a first electronic zoom; b) providing a second image acquisition device including: i) a second image sensor array coupled with a second lens having a second FOV; and ii) a second electronic zoom; wherein at least a portion of the environment, viewed from within said second FOV of said second image acquisition device, overlaps the environment viewed from within said first FOV of said first image acquisition device; c) electronically calibrating the alignment between said first image sensor array and said second image sensor array, whereby determining an X-coordinate offset and a Y- coordinate offset of the correlation between said first image sensor array and said second image sensor array. d) providing a user of the image acquisition device with a zoom selecting control, thereby obtaining a requested zoom; e) selecting one of said image acquisition devices based on said requested zoom; f) acquiring an image frame with said selected image acquisition device, thereby obtaining an acquired image frame; and g) performing digitally zoom on said acquired image frame, thereby obtaining an acquired image frame with said requested zoom, wherein said calibrating of said alignment between said first image sensor array and said second image sensor array, facilitates continuous electronic zoom with uninterrupted imaging, when switching back and forth between said first image sensor array and said second image sensor array.

2. The method as in claim 1, wherein the computerized image acquisition system is configured to provide zooming functions selected from the group consisting of a bin function and a skip function; wherein said selecting of said image acquisition device includes selecting the parameters of said bin and/or skip functions; and wherein said method further includes the step of applying said selected bin/skip functions, with said selected parameters, to said acquired image frame, before said performing of said digital zoom step.

3. The method as in claims 1 or 2, wherein said image sensor arrays are focused to the infinite.

4. The method as in claims 1 or 2, wherein said first lens is a focus adjustable lens.

5. The method as in claims 1 or 2, wherein said second lens is a focus adjustable lens.

6. The method as in claims 1 or 2, wherein said second lens is a zoom lens.

7. The method as in claim 1 , where said electronic calibration of said alignment between said first image sensor array and said second image sensor array, further determines a Z-coordinate rotational offset of the correlation between said first image sensor array and said second image sensor array.

8. The method as in claims 1 and 7, wherein said electronic calibration is performed with sub- pixel accuracy.

9. The method as in claim 1, wherein said electronic calibration step is performed on each pair of adjacently disposed image sensor arrays.

10. The method as in claim 1 , wherein said first image acquisition device and said second image acquisition device are coupled with a mutual front lens and a beam splitter, wherein one portion of the light reaching said beam splitter is directed towards said first image sensor array and the remainder portion of the light reaching said beam splitter is directed towards said second image sensor array.

1 1. The method as in claim 1, wherein the angle of view of said first FOV is wider than the angle of view of said second FOV.

12. The method as in claim 1 , wherein said first image sensor array is a color sensor and said second image sensor array is a monochrome sensor, wherein a colored image frame is acquired by said first image sensor array; wherein a monochrome image frame is acquired by said second image sensor array; and wherein said colored image frame and said monochrome image frame are fused to form a high resolution colored image frame.

13. The method as in claim 12, wherein said fusion of said colored image frame and said monochrome image frame includes the step of computing color values for the pixels of said monochrome image frame from the respective pixels of said colored image frame.

14. The method as in claim 12, wherein the angle of view of said first FOV is wider than the angle of view of said second FOV.

15. The method as in claim 12, wherein the angle of view of said first FOV is substantially equal to the angle of view of said second FOV.

16. The method as in claim 13, wherein said computing of color values is performed in sub pixel accuracy.

Description:
CONTINUOUS ELECTRONIC ZOOM FOR AN IMAGING SYSTEM WITH MULTIPLE IMAGING DEVICES HAVING DIFFERENT FIXED FOV

RELATED APPLICATION The present application claims the benefit of US provisional application

61/167,226 filed on April 7 l , 2009, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates to an electronic zoom for imaging systems, and more particularly, the present invention relates to a continuous electronic zoom for an image acquisition system, the system including multiple imaging devices having different fixed FOV.

BACKGROUND OF THE INVENTION AND PRIOR ART

Digital zoom is a method of narrowing the apparent angle of view of a digital still or video image. Electronic zoom is accomplished by cropping an image down to a centered area of the image with the same aspect ratio as the original, and usually also interpolating the result back up to the pixel dimensions of the original. It is accomplished electronically, without any adjustment of the camera's optics, and no optical resolution is gained in the process. Typically some information is lost in the process.

In video streams (such as PAL. NTSC, SECAM, 656, etc.) the image resolution is known, and by using image sensors having substantially higher resolution, one can perform lossless electronic zoom. The ratio between the image sensor resolution and the output resolution dictates the lossless electronic zoom range. For example, having a 5 Megapixel, 2592X1944, image sensor array and an output resolution frame of 400X300 yields maximal lossless electronic zoom of 6.48:

2592/400 = 6.48, 1944/300 = 6.48. Typically, a camera with a large dynamic zoom range requires heavy and expensive lenses, as well as complex design. Electronic zoom does not need moving mechanical elements, as does optical zoom.

There is a need for and it would be advantageous to have image sensors, having static, light weight electronic zoom and a large lossless zooming range.

SUMMARY OF THE INVENTION

The present invention describes a continuous electronic zoom for an image acquisition system, having multiple imaging devices each with a different fixed field of view (FOV). Using two (or more) image sensors, having different fixed FOV, facilitates a light weight electronic zoom with a large lossless zooming range. For example, a first image sensor has a 60° angle of view and a second image sensor has a 60° angle of view. Therefore. Wide_FOV= Narrow_FOV*6. Hence, switching between the image sensors provide a lossless electronic zoom of 6 2 = 36. This lossless electronic zoom is also referred to herein, as the optimal zoom:

Optimal Zoom = (Wide FOV/Narrow FOV) 2 .

It should be noted that to obtain similar zoom (X36) by optical means, for an output resolution frame of 400X300, the needed image sensor array is:

36*400 = 14400, 36*300 = 10800.

14400*10800 = 155,520,000.

Hence, to obtain a zoom of X36 by optical means, for an output resolution frame of 400X300, one needs a 155 Megapixel, 14400X10800, image sensor array.

According to teachings of the present invention, there is provided a method for continuous electronic zoom in a computerized image acquisition system, the system having multiple optical image acquisition devices each with a FOV. The method includes providing a first image acquisition device having a first image sensor array coupled with a first lens having a first FOV, typically a wide FOV , and a first electronic zoom. The method further includes providing a second image acquisition device having a second image sensor array coupled with a second lens having a second FOV, typically a narrow FOV, and a second electronic zoom. Typically, the angle of view of the first FOV is wider than the angle of view of the second FOV. At least a portion of the environment, viewed from within the second FOV of the second image acquisition device, overlaps the environment viewed from within the first FOV of the first image acquisition device. The method further includes computing the alignment between the first image sensor array and the second image sensor array, whereby determining an X-coordinate offset, a Y-coordinate offset and optionally, a Z-rotation offset of the correlation between the first image sensor array and the second image sensor array. The method further includes the steps of providing a user of the image acquisition device with a zoom selecting control, thereby obtaining a requested zoom, selecting one of the image acquisition devices based on the requested zoom, acquiring an image frame with the selected image acquisition device, thereby obtaining an acquired image frame, and performing digitally zoom on the acquired image frame, thereby obtaining an acquired image frame with the requested zoom. The calibration of the alignment, between the first image sensor array and the second image sensor array, facilitates continuous electronic zoom with uninterrupted imaging, when switching back and forth between the first image sensor array and the second image sensor array. Preferably the electronic calibration is performed with sub-pixel accuracy. Optionally, the computerized image acquisition system is configured to provide zooming functions selected from the group consisting of a bin function and a skip function. The selecting of the image acquisition device includes selecting the parameters of the bin and/or skip functions, wherein the method further includes the step of applying the selected bin/skip functions to the acquired image frame, before the performing of the digital zoom step.

In variations of the present invention, the image sensor arrays are focused to the infinite.

Optionally, the first lens is a focus adjustable lens. Optionally, the second lens is a focus adjustable lens. Optionally, the second lens is a zoom lens. In image acquisition systems having more than two imaging devices, the electronic calibration step is performed on each pair of adjacently disposed image sensor arrays.

In variations of the present invention, the first image acquisition device and the second image acquisition device are coupled with a mutual front lens and a beam splitter, wherein one portion of the light reaching the beam splitter is directed towards the first image sensor array and the remainder portion of the light reaching the beam splitter is directed towards the second image sensor array.

In embodiments of the present invention, the first image sensor array is a color sensor and the second image sensor array is a monochrome sensor, wherein a colored image frame is acquired by the first image sensor array, a monochrome image frame is acquired by the second image sensor array, wherein the colored image frame and the monochrome image frame are fused to form a high resolution colored image frame. In preferred embodiments of the present invention, the angle of view of the first FOV is wider than the angle of view of the second FOV. However, in variation of the present invention, the angle of view of the first FOV is substantially equal to the angle of view of the second FOV.

Optionally, the fusion of the colored image frame and the monochrome image frame includes the step of computing color values for the high resolution pixels of the monochrome image frame from the respective low resolution pixels of the colored image frame. Optionally, the computing of color values is performed in sub pixel accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will become fully understood from the detailed description given herein below and the accompanying drawings, which are given by way of illustration and example only and thus not limitative of the present invention, and wherein:

FIG. 1 is a block diagram illustration of another zoom control sub-system for an image acquisition system, according to variations of the present invention;

FIG. 2 is a schematic flow diagram chart that outlines the successive steps of the continuous zoom process, according to embodiments of the present invention; FIG. 3 is a block diagram illustration of a zoom control sub-system for an image acquisition system, according to variations of the present invention;

FIG. 4 is a schematic flow diagram chart that outlines the successive steps of the continuous zoom process, according to variations of the present invention, include using bin/skip functions;

FIG. 5a and 5b illustrate examples of beam splitter configurations for image acquisition systems, according to embodiments of the present invention;

FIG. 6 is a block diagram illustration of a camera system, according to embodiments of the present invention, including a color image sensor having wide FOV and a color image sensor having narrow FOV; and

FIG. 7 is a block diagram illustration of another zoom control sub-system for a color image acquisition system, according to variations of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the host description or illustrated in the drawings.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of the invention belongs. The methods and examples provided herein are illustrative only and not intended to be limiting.

It should be noted that in general, the present invention is described, with no limitations, in terms of an image acquisition system having two image acquisition devices. But the present invention is not limited to two image acquisition devices, and in variations of the present invention, the image acquisition system can be similarly embodied with three image acquisition devices and more.

Reference is made to Figure 1, which is a block diagram illustration of a zoom control sub-system 100 for an image acquisition system, according to preferred embodiments of the present invention. Zoom control sub-system 100 includes multiple image sensors, each with a fixed and preferably different FOV, configured to provide continuous electronic zoom capabilities with uninterrupted, when switching back and forth between the image sensors.

Zoom control sub-system 100 includes a tele image sensor 110 coupled with a narrow lens 120 having a predesigned FOV 140, a wide image sensor 112 coupled with a wide lens 122 having a predesigned FOV 142, a zoom control module 130 and an image sensor selector 150. An object 20 is viewed from both tele image sensor 110 and wide image sensor 112, whereas the object is magnified in tele image sensor 110 with respect to wide image sensor 112, by a predesigned factor. In the optimal configuration, the FOV of wide image sensor 112 can be calculated by multiplying the FOV of tele image sensor 110 by the optimal zoom of image sensors 110 and 112. Tele image sensor 110 and wide image sensor 112 are adjacently disposed, such that at least a portion of the environment viewed from within the narrow FOV of tele image acquisition device 110 overlaps the environment viewed from within the wide FOV of wide image acquisition device 112.

Before using zoom control sub-system 100, an electronically calibrating is performed to determine the alignment offsets between wide image sensor array 110 and tele image sensor array 112. Typically, since the spatial offsets between wide image sensor array 110 and tele image sensor array 112 are fixed, the electronic calibration step is performed one time, after the manufacturing of the image acquisition system and before the first use. The electronic calibration yields an X-coordinate offset, a Y- coordinate offset and optionally, a Z-coordinate rotational offset of the correlation between wide image sensor array 110 and tele image sensor array 112. Preferably, all three aforementioned offset values are computed in sub-pixel accuracy. It should be noted that for image acquisition systems with more than two image sensors, the electronic calibration step is performed on each pair of adjacently disposed image sensor arrays.

Zoom control circuit 130 receives a required zoom from an operator of the image acquisition system, and selects the relevant image sensor (110 and 112) by activating image sensor selector 150 position. The relevant camera zoom factor is calculated by zoom control unit 130. An aspect of the present invention is to provide methods facilitating continuous electronic zoom capabilities with uninterrupted imaging, performed by an image acquisition system having multiple image sensors, each with a fixed and preferably different FOV. The continuous electronic zoom with uninterrupted imaging is also maintained when switching back and forth between adjacently disposed image sensors.

Reference is also made to Figure 2, which is a schematic flow diagram chart that outlines the successive steps of an example continuous zoom process 200. according to embodiments of the present invention, performed on image acquisition system, having a zoom control sub-system such as zoom control sub-system 100. Process 200 includes the flowing steps:

Step 210: providing a wide image acquisition device and a tele image acquisition device.

Multiple optical image acquisition devices can be used, but for description clarity, with no limitation, the method will be described in terms of two image acquisition devices: wide image acquisition device and a tele image acquisition device.

Both image acquisition devices (110 and 112) include an image sensor array coupled with a lens (120 and 122, respectively), providing a fixed FOV (tele FOV 140 and wide FOV 142. respectively). Preferably, wide FOV 142 is substantially wider than narrow FOV 140.

The image acquisition devices are adjacently disposed, such that at least a portion of the environment, viewed from within narrow FOV 140 of the tele image acquisition device 110, overlaps the environment viewed from within the wide FOV 142 of wide image acquisition device 112. Step 220: determining alignment offsets.

Before using zoom control sub-system 100, an electronically calibrating is performed to determine the alignment offsets between wide image sensor array 110 and tele image sensor array 112. Typically, since the spatial offsets between wide image sensor array 110 and tele image sensor array 112 are fixed, the electronic calibration step is performed one time, after the manufacturing of the image acquisition system and before the first use. The electronic calibration yields an X-coordinate offset and a Y-coordinate offset of the correlation between wide image sensor array 110 and tele image sensor array 112. Preferably, the X-coordinate offset and the Y-coordinate offset are computed in sub-pixel accuracy. It should be noted that for image acquisition systems with more than two image sensors, the electronic calibration step is performed on each pair of adjacently disposed image sensor arrays.

Step 230: zoom selection.

A user of the image acquisition selects the required zoom. Step 240: selecting an image acquisition device. The zoom control 130 selects an image acquisition device with the having a zoom more proximal to the requested zoom.

Step 250: acquiring an image frame.

An image frame is acquired by the selected image acquisition device. Step 260: resampling the acquired image frame to the requested zoom. The zoom control 130 computes the zoom factor between the fixed zoom of the selected image acquisition device and the requested zoom. Based on the computed factor, zoom control 130 performs electronic zoom on the acquired image frame to meet the requested zoom.

Reference is made back to Figure 1 and referring also to Figures 5a and 5b, which illustrates examples of beam splitter configurations for image acquisition systems, according to embodiments of the present invention. In variations of the present invention, wide image acquisition device 112 and tele image acquisition device

110 are coupled with a mutual front lens 570 and a beam splitter 580, wherein one portion of the light reaching beam splitter 580 is directed towards wide image sensor array 112 and the remainder portion of the light reaching beam splitter 580 is directed towards tele image sensor array 110. In Figure 5a, the beam splitter configuration includes a wide angle lens 572, to provide image sensor 510 a wider FOV with respect to image sensor 512. In Figure 5b, the beam splitter configuration includes wide angle lens 572, to provide image sensor 510 a wide FOV, and a narrow angle lens 574, to provide image sensor 512 a narrow FOV, relative to the FOV of image sensor 512. Reference is now made to Figure 3, which is a block diagram illustration of zoom control sub-system 300 for an image acquisition system, according to some embodiments of the present invention. Zoom control sub-system 300 includes an image sensor 310 having a lens module 320 with a fixed focal length lens or a zoom lens, a zoom control module 330 and a digital-zoom module 340. An object 20 is captured by image sensor 310 through lens module 320. Zoom control unit 330 calculates the most optimal values for image sensor 310, binning/skip factors and continuous digital-zoom values that are provided to digital-zoom unit 340. Setting the binning/skip factor and windowing of image sensor 310 allows to keep a suitable frame refresh rate, while digital-zoom unit 340 provides continuous zoom.

A binning function, which function is optionally provided by the sensor array provider, is a zoom out function that merges 2x2, or 4x4, or 8x8 pixels pixel array, or any other square array of pixels, into a single pixel, whereby reducing the image frame dimensions. The binning function may be refined by using algorithms such as "bi- linear" interpolation, "bi-cubic" interpolation and other commonly used digital zoom algorithms. A skip function, which function is optionally provided by the sensor array provider, is a zoom out function that allows skipping pixels while reading frame out, whereby reducing the image frame dimensions and decrease the image acquisition time. In variations of the present invention, zoom control sub-system 100 of a image acquisition system includes the binning/skip function capabilities as in zoom control sub-system 300.

Reference is also made to Figure 4, which is a schematic flow diagram chart that outlines the successive steps of an example continuous zoom process 400, according to embodiments of the present invention, performed on image acquisition system, having a zoom control sub-system such as zoom control sub-system 100.

Process 400 includes the flowing steps:

Step 410: providing a wide image acquisition device and a tele image acquisition device. Multiple optical image acquisition devices can be used, but for description clarity, with no limitation, the method will be described in terms of two image acquisition devices: wide image acquisition device and a tele image acquisition device.

Both image acquisition devices (110 and 112) include an image sensor array coupled with a lens (120 and 122, respectively), providing a fixed FOV (tele FOV 140 and wide FOV 142, respectively). Preferably, wide FOV 142 is substantially wider than narrow FOV 140.

The image acquisition devices are adjacently disposed, such that at least a portion of the environment, viewed from within narrow FOV 140 of the tele image acquisition device 110, overlaps the environment viewed from within the wide FOV 142 of wide image acquisition device 112.

Step 420: determining alignment offsets.

Before using zoom control sub-system 100, an electronically calibrating is performed to determine the alignment offsets between wide image sensor array 110 and tele image sensor array 112. Typically, since the spatial offsets between wide image sensor array 110 and tele image sensor array 112 are fixed, the electronic calibration step is performed one time, after the manufacturing of the image acquisition system and before the first use. The electronic calibration yields an X-coordinate offset, a Y-coordinate offset and optionally, a Z- coordinate rotational offset of the correlation between wide image sensor array 110 and tele image sensor array 112. Preferably, all three aforementioned coordinate offset values are computed in sub-pixel accuracy. It should be noted that for image acquisition systems with more than two image sensors, the electronic calibration step is performed on each pair of adjacently disposed image sensor arrays. Step 430: zoom selection.

A user of the image acquisition selects the required zoom. Step 435: bin/skip function selection.

The zoom control 130 selects the bin/skip function, typically provided by the image sensor provider, bringing the combination of the optical zoom and the binning/skip magnification selection, to a zoom value most proximal to the requested zoom. Step 440: selecting an image acquisition device.

The zoom control 130 selects an image acquisition device, bringing the combination of the optical zoom and the binning/skip magnification selection, to a zoom value most proximal to the requested zoom. Step 450: acquiring an image frame.

An image frame is acquired by the selected image acquisition device.

Step 460: performing electronic zoom on the acquired image frame to meet the requested zoom.

The zoom control 130 computes the zoom factor between the fixed zoom of the selected image acquisition device, combined with the selected by bin/skip factor, and the requested zoom. Based on the computed factor, zoom control 130 performs electronic zoom on the acquired image frame to meet the requested zoom.

Reference is now made to Figure 6, which is a block diagram illustration of a camera system 600, according to embodiments of the present invention, including a color image sensor 612 having wide FOV 642 and a monochrome image sensor 610 having narrow FOV 640. The angle of view of wide FOV 142 is typically wider than the angle of view of narrow FOV 140. In some variations of the present invention, the angle of view of wide FOV 142 is substantially equal to the angle of view of narrow FOV 140.

A principal intention of the present invention includes providing a camera system 600 and a method of use thereof, wherein the output image frame 650 has the resolution of image sensor 610, having narrow FOV 640, and the color of image sensor 612, having wide FOV 642. Reference is now made to Figure 7, which is a block diagram illustration of another zoom control sub-system 700 for a color image acquisition system, according to variations of the present invention. A colored image frame 632 is acquired by wide image sensor array 612, and a monochrome image frame 630 is acquired by narrow image sensor array 610. When image sensor selector 750 closes contact 752, monochrome image sensor 610 is bypassed and only color image sensor 612 having is in operation.

When image sensor selector 750 closes contact 754, both monochrome image sensor 610 and color image sensor 612 are in operation, whereas image frames are acquired by monochrome image sensor 610 and color of image sensor 612, synchronously. Fusion module 660 extracts the color information from color image frame 632 and fuses the extracted color information with monochrome image frame

630 to form a high resolution, colored image frame 650. The fusion includes computing color values for the high resolution pixels of monochrome image frame 630 from the respective low resolution color image frame 632. Preferably, the computation and alignment of the color values is performed in sub pixel accuracy.

In some variations of the present invention, the output colored image frame 650 is provided with RGB information. In other variations of the present invention, fusion module 760 transmits the Y information, obtained from monochrome image sensor 610 covered with color (Cr, Cb) information obtained from color image sensor 612. The color information obtained from color image sensor 612 via a color space. Then, fusion module 760 merges the Y information, obtained from monochrome image sensor 610, and the color (Cr, Cb) information. Then, color space conversion module 770 converts the image back to an RGB color space, creating colored output image frame 650. Optionally, the (Y, Cr, Cb) image information is transmitted in separate channels to an image receiving unit, bypassing color space conversion module 770.

The invention being thus described in terms of embodiments and examples, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.