Dual aperture zoom digital camera

Abstract

A dual-aperture zoom digital camera operable in both still and video modes. The camera includes Wide and Tele imaging sections with respective lens/sensor combinations and image signal processors and a camera controller operatively coupled to the Wide and Tele imaging sections. The Wide and Tele imaging sections provide respective image data. The controller is configured to combine in still mode at least some of the Wide and Tele image data to provide a fused output image from a particular point of view, and to provide without fusion continuous zoom video mode output images, each output image having a given output resolution, wherein the video mode output images are provided with a smooth transition when switching between a lower zoom factor (ZF) value and a higher ZF value or vice versa, and wherein at the lower ZF the output resolution is determined by the Wide sensor while at the higher ZF value the output resolution is determined by the Tele sensor.

Claims

1. A multiple aperture zoom digital camera, comprising: a) a Wide imaging section that includes a Wide sensor and a fixed focal length Wide lens with a Wide field of view (FOV), the Wide imaging section operative to output a Wide image; b) a Tele imaging section that includes a Tele sensor and a fixed focal length Tele lens with a Tele FOV that is narrower than the Wide FOV, the Tele imaging section operative to output a Tele image; and c) a camera controller operatively coupled to the Wide and Tele imaging sections and configured, when providing video output images, to: reduce an image jump effect seen in the video output images when switching from a Wide image to a Tele image by shifting the Tele image relative to the Wide image according to a distance of an object in a Tele image region of interest (ROI), and/or reduce an image jump effect seen in the video output images when switching from a Tele image to a Wide image by shifting the Wide image relative to the Tele image according to a distance of an object in a Wide image ROI.

2. The camera of claim 1, wherein the camera controller is further configured, when providing the video output images, to reduce the image jump effect seen in the video output images by matching scale between the Wide and Tele images when switching from the Wide image to the Tele image or vice versa.

3. The camera of claim 1, wherein the camera controller is further configured, when providing video output images, to match brightness and color between the Wide image and the Tele images when switching from a Wide image to a Tele image or vice versa.

4. The camera of claim 1, wherein the switching is between a lower zoom factor (ZF) value and a higher ZF value or vice versa, wherein each Wide image and Tele image has a respective output resolution, wherein at the lower ZF value the output resolution is determined by the Wide sensor and wherein at the higher ZF value the output resolution is determined by the Tele sensor.

5. The camera of claim 4, wherein the camera controller includes a user control module for receiving user inputs and a sensor control module for configuring each sensor to acquire the Wide and Tele images based on a user input that includes a camera mode and the zoom factor.

6. The camera of claim 4, wherein the camera controller is further configured to use, at the higher ZF, secondary information from the Wide imaging section, for providing video output images during switching between a lower ZF value and a higher ZF value to reduce discontinuities in the video output images.

7. The camera of claim 4, wherein the camera controller is further configured to use at the lower ZF, secondary information from the Tele imaging section, for providing video output images during switching between a higher ZF value and a lower ZF value to reduce discontinuities in the video output images.

8. The camera of claim 1, wherein the Tele lens includes a ratio of total track length (TTL)/effective focal length (EFL) smaller than 1.

9. The camera of claim 8, wherein the camera controller is further configured to combine, when in still mode, at least some of the Wide and Tele image data to provide a fused output image.

10. The camera of claim 9, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that a rolling shutter starts substantially the same time for both sensors.

11. The camera of claim 9, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that same points of the object in each view are obtained substantially simultaneously.

12. The camera of claim 8, wherein the camera controller is further configured to provide from the captured images an image with a shallow depth of field.

13. The camera of claim 12, wherein the camera controller is further configured to combine, when in still mode, at least some of the Wide and Tele image data to provide a fused output image.

14. The camera of claim 13, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that a rolling shutter starts substantially at the same time for both sensors.

15. The camera of claim 13, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that same points of the object in each view are obtained substantially simultaneously.

16. The camera of claim 12, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that a rolling shutter starts substantially at the same time for both sensors.

17. The camera of claim 12, wherein the camera controller is further configured to synchronize the Wide and Tele sensors so that same points of the object in each view are obtained substantially simultaneously.

18. The camera of claim 12, where the shallow depth of field images are suited for portrait photos.

19. A method for providing a digital video output in a multiple aperture zoom digital camera, comprising steps of: a) providing a Wide imaging section that includes a Wide sensor and a fixed focal length Wide lens with a Wide field of view (FOV), the Wide imaging section operative to output a Wide image; b) providing a Tele imaging section that includes a Tele sensor and a fixed focal length Tele lens with a Tele FOV that is narrower than the Wide FOV, the Tele imaging section operative to output a Tele image; and c) when providing video output images, utilizing a camera controller operatively coupled to the Wide and Tele imaging sections to reduce an image jump effect seen in the video output images when switching from a Wide image to a Tele image by shifting the Tele image relative to the Wide image according to a distance of an object in a Tele image region of interest (ROI), and/or to reduce an image jump effect seen in the video output images when switching from a Tele image to a Wide image by shifting the Wide image relative to the Tele image according to a distance of an object in a Wide image ROI.

20. The method of claim 19, wherein the reducing the image jump effect seen in the video output images further includes reducing the image jump by matching scale between the Wide and Tele images when switching from a Wide image to a Tele image or vice versa.

21. The method of claim 19, wherein the utilizing a camera controller to reduce an image jump effect seen in the video output images further includes utilizing the controller to match brightness and color between the Wide and Tele images when switching from a Tele image to a Wide image or vice versa.

22. The method of claim 19, wherein the switching is between a lower zoom factor (ZF) value and a higher ZF value or vice versa, wherein each Tele image and Wide image has a respective output resolution, wherein at the lower ZF value the output resolution is determined by the Wide sensor and wherein at the higher ZF value the output resolution is determined by the Tele sensor.

23. The method of claim 22, further comprising using a user control module to receive user inputs and using a sensor control module to configure each image sensor to acquire the Wide and Tele images based on a user input that includes a camera mode and a zoom factor.

24. The method of claim 19, further comprising during switching between a lower zoom factor (ZF) value and a higher ZF value, generating the video output images while using, at the higher ZF, secondary information from the Wide imaging section, thereby reducing discontinuities in the video output images.

25. The method of claim 19, further comprising during switching between a higher zoom factor (ZF) value and a lower ZF value generating the video output images while using, at the lower ZF, secondary information from the Tele imaging section, thereby reducing discontinuities in the video output images.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Non-limiting examples of embodiments disclosed herein are described below with reference to figures attached hereto that are listed following this paragraph. The drawings and descriptions are meant to illuminate and clarify embodiments disclosed herein, and should not be considered limiting in any way.

(2) FIG. 1A shows schematically a block diagram illustrating a dual-aperture zoom imaging system disclosed herein;

(3) FIG. 1B is a schematic mechanical diagram of the dual-aperture zoom imaging system of FIG. 1A:

(4) FIG. 2 shows an example of Wide sensor, Tele sensor and their respective FOVs;

(5) FIG. 3 shows a schematically embodiment of CMOS sensor image grabbing vs. time;

(6) FIG. 4 shows schematically a sensor time configuration which enables sharing one sensor interface using dual sensor zoom system;

(7) FIG. 5 shows an embodiment of a method disclosed herein for acquiring a zoom image in capture mode;

(8) FIG. 6 shows an embodiment of a method disclosed herein for acquiring a zoom image in video/preview mode;

(9) FIG. 7 shows a graph illustrating an effective resolution zoom factor;

(10) FIG. 8 shows one embodiment of a lens block in a thin camera disclosed herein;

(11) FIG. 9 shows another embodiment of a lens block in a thin camera disclosed herein.

DETAILED DESCRIPTION

(12) FIG. 1A shows schematically a block diagram illustrating an embodiment of a dual-aperture zoom imaging system (also referred to simply as digital camera or camera) disclosed herein and numbered 100. Camera 100 comprises a Wide imaging section (sub-camera) that includes a Wide lens block 102, a Wide image sensor 104 and a Wide image processor 106. Camera 100 further comprises a Tele imaging section (sub-camera) that includes a Tele lens block 108, a Tele image sensor 110 and a Tele image processor 112. The image sensors may be physically separate or may be part of a single larger image sensor. The Wide sensor pixel size can be equal to or different from the Tele sensor pixel size. Camera 100 further comprises a camera fusion processing core (also referred to as controller) 114 that includes a sensor control module 116, a user control module 118, a video processing module 126 and a capture processing module 128, all operationally coupled to sensor control block 110. User control module 118 comprises an operational mode function 120, a region of interest (ROI) function 122 and a zoom factor (ZF) function 124.

(13) Sensor control module 116 is connected to the two sub-cameras and to the user control module 118 and used to choose, according to the zoom factor, which of the sensors is operational and to control the exposure mechanism and the sensor readout. Mode choice function 120 is used for choosing capture/video modes. ROI function 122 is used to choose a region of interest. As used herein, ROI is a user defined as a sub-region of the image that may be exemplarily 4% or less of the image area. The ROI is the region on which both sub-cameras are focused on. Zoom factor function 124 is used to choose a zoom factor. Video processing module 126 is connected to mode choice function 120 and used for video processing. Still processing module 128 is connected to the mode choice function 120 and used for high image quality still mode images. The video processing module is applied when the user desires to shoot in video mode. The capture processing module is applied when the user wishes to shoot still pictures.

(14) FIG. 1B is a schematic mechanical diagram of the dual-aperture zoom imaging system of FIG. 1A. Exemplary dimensions: Wide lens TTL=4.2 mm and EFL=3.5 mm; Tele lens TTL=6 mm and EFL=7 mm; both Wide and Tele sensors inch. External dimensions of Wide and Tele cameras: width (w) and length (l)=8.5 mm and height (h)=6.8 mm. Distance d between camera centers=10 mm.

(15) Following is a detailed description and examples of different methods of use of camera 100.

(16) Design for Continuous and Smooth Zoom in Video Mode

(17) In an embodiment, in order to reach high quality continuous and smooth optical zooming in video camera mode while reaching real optical zoom using fixed focal length sub-cameras, the system is designed according to the following rules (Equations 1-3):
Tan(FOV.sub.Wide)/Tan(FOV.sub.Tele)=PL.sub.Wide/PL.sub.video(1)
where Tan refers to tangent, while FOV.sub.Wide and FOV.sub.Tele refer respectively to the Wide and Tele lens fields of view (in degrees). As used herein, the FOV is measured from the center axis to the corner of the sensor (i.e. half the angle of the normal definition). PL.sub.Wide and PL.sub.video refer respectively to the in-line (i.e. in a line) number of Wide sensor pixels and in-line number of output video format pixels. The ratio PL.sub.Wide/PL.sub.video is called an oversampling ratio. For example, in order to get full and continuous optical zoom experience with a 12 Mp sensor (sensor dimensions 40003000) and a required 1080p (dimension 19201080) video format, the FOV ratio should be 4000/1920=2.083. Moreover, if the Wide lens FOV is given as FOV.sub.Wide=37.5.sup.0, the required Tele lens FOV is 20.2.sup.0 The zoom switching point is set according to the ratio between sensor pixels in-line and the number of pixels in-line in the video format and defined as:
Z.sub.switch=PL.sub.Wide/PL.sub.video(2)

(18) Maximum optical zoom is reached according to the following formula:
Z.sub.max=Tan(FOV.sub.Wide)/Tan(FOV.sub.Tele)*PL.sub.Tele/PL.sub.video(3)
For example: for the configuration defined above and assuming PL.sub.tele=4000 and PL.sub.video=1920, Z.sub.max=4.35.

(19) In an embodiment, the sensor control module has a setting that depends on the Wide and Tele FOVs and on a sensor oversampling ratio, the setting used in the configuration of each sensor. For example, when using a 40003000 sensor and when outputting a 19201080 image, the oversampling ratio is 4000/1920=2.0833.

(20) In an embodiment, the Wide and Tele FOVs and the oversampling ratio satisfy the condition
0.8*PL.sub.Wide/PL.sub.video<Tan(FOV.sub.Wide)/Tan(FOV.sub.Tele)<1.2*PL.sub.Wide/PL.sub.video.(4)
Still Mode Operation/Function

(21) In still camera mode, the obtained image is fused from information obtained by both sub-cameras at all zoom levels, see FIG. 2, which shows a Wide sensor 202 and a Tele sensor 204 and their respective FOVs. Exemplarily, as shown, the Tele sensor FOV is half the Wide sensor FOV. The still camera mode processing includes two stages: (1) setting HW settings and configuration, where a first objective is to control the sensors in such a way that matching FOVs in both images (Tele and Wide) are scanned at the same time. A second objective is to control the relative exposures according to the lens properties. A third objective is to minimize the required bandwidth from both sensors for the ISPs; and (2) image processing that fuses the Wide and the Tele images to achieve optical zoom, improves SNR and provides wide dynamic range.

(22) FIG. 3 shows image line numbers vs. time for an image section captured by CMOS sensors. A fused image is obtained by line (row) scans of each image. To prevent matching FOVs in both sensors to be scanned at different times, a particular configuration is applied by the camera controller on both image sensors while keeping the same frame rate. The difference in FOV between the sensors determines the relationship between the rolling shutter time and the vertical blanking time for each sensor. In the particular configuration, the scanning is synchronized such that the same points of the object in each view are obtained simultaneously.

(23) Specifically with reference to FIG. 3 and according to an embodiment of a method disclosed herein, the configuration to synchronize the scanning includes: setting the Tele sensor vertical blanking time VB.sub.Tele to equal the Wide sensor vertical blanking time VB.sub.Wide plus half the Wide sensor rolling shutter time RST.sub.Wide; setting the Tele and Wide sensor exposure times ET.sub.Tele and ET.sub.Wide to be equal or different; setting the Tele sensor rolling shutter time RST.sub.Tele to be 0.5*RST.sub.Wide; and setting the frame rates of the two sensors to be equal. This procedure results in identical image pixels in the Tele and Wide sensor images being exposed at the same time

(24) In another embodiment, the camera controller synchronizes the Wide and Tele sensors so that for both sensors the rolling shutter starts at the same time.

(25) The exposure times applied to the two sensors could be different, for example in order to reach same image intensity using different F# and different pixel size for the Tele and Wide systems. In this case, the relative exposure time may be configured according to the formula below:
ET.sub.Tele=ET.sub.Wide.Math.(F#.sub.Tele/F#.sub.Wide).sup.2.Math.(Pixel size.sub.Wide/Pixel size.sub.Tele).sup.2(5)
Other exposure time ratios may be applied to achieve wide dynamic range and improved SNR. Fusing two images with different intensities will result in wide dynamic range image.

(26) In more detail with reference to FIG. 3, in the first stage, after the user chooses a required zoom factor ZF, the sensor control module configures each sensor as follows:

(27) 1) Cropping index Wide sensor:
Y.sub.Wide start=1/2.Math.PC.sub.Wide(11/ZF)
Y.sub.Wide end=1/2.Math.PC.sub.Wide(1+1/ZF)
where PC is the number of pixels in a column, and Y is the row number

(28) 2) Cropping index Tele sensor:

(29) If ZF>Tan (FOV.sub.Wide)/Tan (FOV.sub.Tele), then
Y.sub.Tele start=1/2.Math.PC.sub.Tele(1(1/ZF).Math.Tan(FOV.sub.Tele)/Tan(FOV.sub.Wide))
Y.sub.Tele end=1/2.Math.PC.sub.Tele(1+(1/ZF).Math.Tan(FOV.sub.Tele)/Tan(FOV.sub.Wide))
If ZF<Tan (FOV.sub.Wide)/Tan (FOV.sub.Tele), then
Y.sub.Tele start=0
Y.sub.Tele end=PC.sub.Tele

(30) This will result in an exposure start time of the Tele sensor with a delay of (in numbers of lines, relative to the Wide sensor start time):
(1ZF/((Tan(FOV.sub.Wide)/Tan(FOV.sub.Tele))).Math.1/(2.Math.FPS)(6)
where FPS is the sensor's frame per second configuration. In cases where ZF>Tan (FOV.sub.Wide)/Tan (FOV.sub.Tele), no delay will be introduced between Tele and Wide exposure starting point. For example, for a case where Tan (FOV.sub.Wide)/Tan (FOV.sub.Tele)=2 and ZF=1, the Tele image first pixel is exposed 1/4.Math.(1/FPS) second after the Wide image first pixel was exposed.

(31) After applying the cropping according to the required zoom factor, the sensor rolling shutter time and the vertical blank should be configured in order to satisfy the equation to keep the same frame rate:
VB.sub.Wide+RST.sub.Wide=VB.sub.Tele+RST.sub.Tele(7)

(32) FIG. 3 exemplifies Eq. (7), One way to satisfy Eq. (7) is to increase the RST.sub.Wide. Controlling the RST.sub.Wide may be done by changing the horizontal blanking (HB) of the Wide sensor. This will cause a delay between the data coming out from each row of the Wide sensor.

(33) Generally, working with a dual-sensor system requires multiplying the bandwidth to the following block, for example the ISP. For example, using 12 Mp working at 30 fps, 10 bit per pixel requires working at 3.6 Gbit/sec. In this example, supporting this bandwidth requires 4 lanes from each sensor to the respective following ISP in the processing chain. Therefore, working with two sensors requires double bandwidth (7.2 Gbit/sec) and 8 lanes connected to the respective following blocks. The bandwidth can be reduced by configuring and synchronizing the two sensors. Consequently, the number of lanes can be half that of a conventional configuration (3.6 Gbit/sec).

(34) FIG. 4 shows schematically a sensor time configuration that enables sharing one sensor interface using a dual-sensor zoom system, while fulfilling the conditions in the description of FIG. 3 above. For simplicity, assuming the Tele sensor image is magnified by a factor of 2 compared with the Wide sensor image, the Wide sensor horizontal blanking time HB.sub.Wide is set to twice the Wide sensor line readout time. This causes a delay between output Wide lines. This delay time matches exactly the time needed to output two lines from the Tele sensor. After outputting two lines from the Tele sensor, the Tele sensor horizontal blanking time HB.sub.Tele is set to be one Wide line readout time, so, while the Wide sensor outputs a row from the sensor, no data is being output from the Tele sensor. For this example, every 3.sup.rd line in the Tele sensor is delayed by an additional HB.sub.Tele. In this delay time, one line from the Wide sensor is output from the dual-sensor system. After the sensor configuration stage, the data is sent in parallel or by using multiplexing into the processing section.

(35) FIG. 5 shows an embodiment of a method disclosed herein for acquiring a zoom image in still mode. In ISP step 502, the data of each sensor is transferred to the respective ISP component, which performs on the data various processes such as denoising, demosaicing, sharpening, scaling, etc, as known in the art. After the processing in step 502, all following actions are performed in capture processing core 128: in rectification step 504, both Wide and Tele images are aligned to be on the epipolar line; in registration step 506, mapping between the Wide and the Tele aligned images is performed to produce a registration map; in resampling step 508, the Tele image is resampled according to the registration map, resulting in a re-sampled Tele image; in decision step 510, the re-sampled Tele image and the Wide image are processed to detect errors in the registration and to provide a decision output. In more detail, in step 510, the re-sampled Tele image data is compared with the Wide image data and if the comparison detects significant dissimilarities, an error is indicated. In this case, the Wide pixel values are chosen to be used in the output image. Then, in fusion step 512, the decision output, re-sampled Tele image and the Wide image are fused into a single zoom image.

(36) To reduce processing time and power, steps 506, 508, 510, 512 could be bypassed by not fusing the images in non-focused areas. In this case, all steps specified above should be applied on focused areas only. Since the Tele optical system will introduce shallower depth of field than the Wide optical system, defocused areas will suffer from lower contrast in the Tele system.

(37) Zoom-in and Zoom-Out in Still Camera Mode

(38) We define the following: TFOV=tan (camera FOV/2). Low ZF refers to all ZF that comply with ZF<Wide TFOV/Tele TFOV. High ZF refers to all ZF that comply with ZF>Wide TFOV/Tele TFOV. ZFT refers to a ZF that complies with ZF=Wide TFOV/Tele TFOV. In one embodiment, zoom-in and zoom-out in still mode is performed as follows:

(39) Zoom-in: at low ZF up to slightly above ZFT, the output image is a digitally zoomed, Wide fusion output. For the up-transfer ZF, the Tele image is shifted and corrected by global registration (GR) to achieve smooth transition. Then, the output is transformed to a Tele fusion output. For higher (than the up-transfer) ZF, the output is the Tele fusion output digitally zoomed.

(40) Zoom-out: at high ZF down to slightly below ZFT, the output image is a digitally zoomed, Tele fusion output. For the down-transfer ZF, the Wide image is shifted and corrected by GR to achieve smooth transition. Then, the output is transformed to a Wide fusion output. For lower (than the down-transfer) ZF, the output is basically the down-transfer ZF output digitally zoomed but with gradually smaller Wide shift correction, until for ZF=1 the output is the unchanged Wide camera output.

(41) In another embodiment, zoom-in and zoom-out in still mode is performed as follows:

(42) Zoom-in: at low ZF up to slightly above ZFT, the output image is a digitally zoomed, Wide fusion output. For the up-transfer ZF and above, the output image is the Tele fusion output.

(43) Zoom-out: at high ZF down to slightly below ZFT, the output image is a digitally zoomed, Tele fusion output. For the down-transfer ZF and below, the output image is the Wide fusion output.

(44) Video Mode Operation/Function

(45) Smooth Transition

(46) When a dual-aperture camera switches the camera output between sub-cameras or points of view, a user will normally see a jump (discontinuous) image change. However, a change in the zoom factor for the same camera and POV is viewed as a continuous change. A smooth transition is a transition between cameras or POVs that minimizes the jump effect. This may include matching the position, scale, brightness and color of the output image before and after the transition. However, an entire image position matching between the sub-camera outputs is in many cases impossible, because parallax causes the position shift to be dependent on the object distance. Therefore, in a smooth transition as disclosed herein, the position matching is achieved only in the ROI region while scale brightness and color are matched for the entire output image area.

(47) Zoom-in and Zoom-Out in Video Mode

(48) In video mode, sensor oversampling is used to enable continuous and smooth zoom experience. Processing is applied to eliminate the changes in the image during crossover from one sub-camera to the other. Zoom from 1 to Z.sub.switch is performed using the Wide sensor only. From Z.sub.switch and on, it is performed mainly by the Tele sensor. To prevent jumps (roughness in the image), switching to the Tele image is done using a zoom factor which is a bit higher (Z.sub.switch+Zoom) than Z.sub.switch. Zoom is determined according to the system's properties and is different for cases where zoom-in is applied and cases where zoom-out is applied (Zoom.sub.inZoom.sub.out). This is done to prevent residual jumps artifacts to be visible at a certain zoom factor. The switching between sensors, for an increasing zoom and for decreasing zoom, is done on a different zoom factor.

(49) The zoom video mode operation includes two stages: (1) sensor control and configuration, and (2) image processing. In the range from 1 to Z.sub.switch, only the Wide sensor is operational, hence, power can be supplied only to this sensor. Similar conditions hold for a Wide AF mechanism. From Z.sub.switch+Zoom to Z.sub.max only the Tele sensor is operational, hence, power is supplied only to this sensor. Similarly, only the Tele sensor is operational and power is supplied only to it for a Tele AF mechanism. Another option is that the Tele sensor is operational and the Wide sensor is working in low frame rate. From Z.sub.switch to Z.sub.switch+Zoom, both sensors are operational.

(50) Zoom-in: at low ZF up to slightly above ZFT, the output image is the digitally zoomed, unchanged Wide camera output. For the up-transfer ZF, the output is a transformed Tele sub-camera output, where the transformation is performed by a global registration (GR) algorithm to achieve smooth transition. For higher (than the up-transfer), the output is the transfer ZF output digitally zoomed.

(51) Zoom-out: at high ZF down to slightly below ZFT, the output image is the digitally zoomed transformed Tele camera output. For the down-transfer ZF, the output is a shifted Wide camera output, where the Wide shift correction is performed by the GR algorithm to achieve smooth transition, i.e. with no jump in the ROI region. For lower (than the down-transfer) ZF, the output is basically the down-transfer ZF output digitally zoomed but with gradually smaller Wide shift correction, until for ZF=1 the output is the unchanged Wide camera output.

(52) FIG. 6 shows an embodiment of a method disclosed herein for acquiring a zoom image in video/preview mode for 3 different zoom factor (ZF) ranges: (a) ZF range=1:Z.sub.switch; (b) ZF range=Z.sub.switch:Z.sub.switch+Zoom.sub.in: and (c) Zoom factor range=Z.sub.switch+Zoom.sub.in:Z.sub.max. The description is with reference to a graph of effective resolution vs. zoom value (FIG. 7). In step 602, sensor control module 116 chooses (directs) the sensor (Wide, Tele or both) to be operational. Specifically, if the ZF range=1:Z.sub.switch, module 116 directs the Wide sensor to be operational and the Tele sensor to be non-operational. If the ZF range is Z.sub.switch:Z.sub.switch+Zoom.sub.in, module 116 directs both sensors to be operational and the zoom image is generated from the Wide sensor. If the ZF range is Z.sub.switch+Zoom.sub.in:Z.sub.max, module 116 directs the Wide sensor to be non-operational and the Tele sensor to be operational. After the sensor choice in step 602, all following actions are performed in video processing core 126. Optionally, in step 604, color balance is calculated if two images are provided by the two sensors. Optionally yet, in step 606, the calculated color balance is applied in one of the images (depending on the zoom factor). Further optionally, in step 608, registration is performed between the Wide and Tele images to output a transformation coefficient. The transformation coefficient can be used to set an AF position in step 610. In step 612, an output of any of steps 602-608 is applied on one of the images (depending on the zoom factor) for image signal processing that may include denoising, demosaicing, sharpening, scaling, etc. In step 614, the processed image is resampled according to the transformation coefficient, the requested ZF (obtained from zoom function 124) and the output video resolution (for example 1080p). To avoid a transition point to be executed at the same ZF, Zoom can change while zooming in and while zooming out. This will result in hysteresis in the sensor switching point.

(53) In more detail, for ZF range 1: Z.sub.switch, for ZF<Z.sub.switch, the Wide image data is transferred to the ISP in step 612 and resampled in step 614. For ZF range=Z.sub.switch:Z.sub.switch+Zoom.sub.in, both sensors are operational and the zoom image is generated from the Wide sensor. The color balance is calculated for both images according to a given ROI. In addition, for a given ROI, registration is performed between the Wide and Tele images to output a transformation coefficient. The transformation coefficient is used to set an AF position. The transformation coefficient includes the translation between matching points in the two images. This translation can be measured in a number of pixels. Different translations will result in a different number of pixel movements between matching points in the images. This movement can be translated into depth and the depth can be translated into an AF position. This enables to set the AF position by only analyzing two images (Wide & Tele). The result is fast focusing.

(54) Both color balance ratios and transformation coefficient are used in the ISP step. In parallel, the Wide image is processed to provide a processed image, followed by resampling. For ZF range=Z.sub.switch+Zoom.sub.in:Z.sub.max and for Zoom factor>the color Z.sub.switch,+Zoom.sub.in, balance calculated previously is now applied on the Tele image. The Tele image data is transferred to the ISP in step 612 and resampled in step 614. To eliminate crossover artifacts and to enable smooth transition to the Tele image, the processed Tele image is resampled according to the transformation coefficient, the requested ZF (obtained from zoom function 124) and the output video resolution (for example 1080p).

(55) FIG. 7 shows the effective resolution as a function of the zoom factor for a zoom-in case and for a zoom-out case Zoom.sub.up is set when we zoom in, and Zoom.sub.down is set when we zoom out. Setting Zoom.sub.up to be different from Zoom.sub.down will result in transition between the sensors to be performed at different zoom factor (hysteresis) when zoom-in is used and when zoom-out is used. This hysteresis phenomenon in the video mode results in smooth continuous zoom experience.

(56) Optical Design

(57) Additional optical design considerations were taken into account to enable reaching optical zoom resolution using small total track length (TTL). These considerations refer to the Tele lens. In an embodiment, the camera is thin (see also FIG. 1B) in the sense that is has an optical path of less than 9 mm and a thickness/focal length (FP) ratio smaller than about 0.85. Exemplarily, as shown in FIG. 8, such a thin camera has a lens block that includes (along an optical axis starting from an object) five lenses: a first lens element 802 with positive power and two lenses 804 and 806 and with negative power, a fourth lens 808 with positive power and a fifth lens 810 with negative power. In the embodiment of FIG. 8, the EFL is 7 mm, the TTL is 4.7 mm, f=6.12 and FOV=20.sup.0. Thus the Tele lens TTL/EFL ratio is smaller than 0.9. In other embodiments, the Tele lens TTL/EFL ratio may be smaller than 1.

(58) In another embodiment of a lens block in a thin camera, shown in FIG. 9, the camera has a lens block that includes (along an optical axis starting from an object) a first lens element 902 with positive power a second lens element 904 with negative power, a third lens element with positive power 906 and a fourth lens element with negative power 908, and a fifth lens element 910 with positive or negative power In this embodiment, f=7.14, F#=3.5, TTL=5.8 mm and FOV=22.7.sup.0.

(59) In conclusion, dual aperture optical zoom digital cameras and associate methods disclosed herein reduce the amount of processing resources, lower frame rate requirements, reduce power consumption, remove parallax artifacts and provide continuous focus (or provide loss of focus) when changing from Wide to Tele in video mode. They provide a dramatic reduction of the disparity range and avoid false registration in capture mode. They reduce image intensity differences and enable work with a single sensor bandwidth instead of two, as in known cameras.

(60) All patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present disclosure.

(61) While this disclosure has been described in terms of certain embodiments and generally associated methods, alterations and permutations of the embodiments and methods will be apparent to those skilled in the art. The disclosure is to be understood as not limited by the specific embodiments described herein, but only by the scope of the appended claims.