Method and apparatus for capturing digital video

Patent No. US11627391 (titled "Method and apparatus for capturing digital video") on Oct 29, 2021. The application was issued on Apr 11, 2023.

'391 is related to the field of digital image processing, specifically addressing the problem of capturing video with a blurred background while keeping a main subject in focus. Traditional photography often struggles with motion blur, especially when capturing moving subjects or when the camera itself is unstable. Existing techniques to sharpen images can introduce artifacts and data loss, while hardware solutions like image stabilization add cost and complexity.

The underlying idea behind '391 is to selectively blur the background of a video while maintaining a sharp focus on the main subject. This is achieved by capturing a sequence of images, identifying the main subject and background, and then creating modified images by combining information from multiple frames. The pixel values in the modified images are calculated to ensure the main subject remains sharp while the background exhibits motion blur, creating a stylized effect.

The claims of '391 focus on a method implemented within an imaging device for capturing and processing video. This involves displaying a preview, capturing a sequence of images, designating a main subject and background through image processing, generating modified images with a sharp subject and blurred background by combining pixel data from multiple source images, assembling these modified images into a final video, and then storing and displaying the result.

In practice, the invention captures multiple frames of a scene. An algorithm then analyzes these frames to differentiate the main subject from the background. This could involve motion analysis, pattern recognition, or user input. The key is that the algorithm understands which parts of the image should be in focus. The modified images are then created by, for example, averaging the pixel values of the main subject across several frames to reduce blur, while averaging the pixel values of the background with an offset to enhance blur.

This approach differs from traditional image stabilization, which aims to eliminate blur entirely. Instead, '391 embraces blur as a creative tool, selectively applying it to the background to emphasize the main subject. This allows for the creation of videos with a shallow depth of field effect, even when using cameras with smaller sensors or in situations where achieving a natural shallow depth of field is difficult. The designation of the main subject through image processing is also a key differentiator, allowing the system to automatically adapt to different scenes and subjects.

How does this patent fit in bigger picture?

Technical Landscape

In the mid-2000s when ’391 was filed, digital image capture was typically implemented using CCD or CMOS sensors that recorded light continuously while a shutter remained open. At a time when systems commonly relied on increasing shutter speeds to mitigate motion blur, hardware constraints made capturing high-quality images in low-light conditions non-trivial due to the resulting loss of light and increased noise. Engineering practices for correcting blur often relied on mechanical lens stabilization or post-capture sharpening filters, which frequently resulted in data loss or increased hardware weight and cost rather than mathematically reversing the motion-induced distortion.

Prosecution Position

The examiner allowed the application because the prior art did not demonstrate the specific method of identifying a primary subject by processing two or more images from a sequence. Specifically, the claims were approved for the technique of calculating new pixel values from multiple source images to create a modified sequence where the chosen main subject is rendered without blur while the background remains blurred, followed by combining these modified images into a final video for storage and display.

Claims

This patent contains 20 claims, of which claims 1, 8, and 15 are independent. The independent claims are directed to a method, an apparatus, and a processor for capturing and processing video by designating a main subject and background, and blurring the background. The dependent claims generally add further specificity or limitations to the independent claims.

Key Claim Terms New

Definitions of key terms used in the patent claims.

Term (Source)	Support for Specification	Interpretation
Background (Claim 1, Claim 8, Claim 15)	This embodiment is illustrated in background is blurred. As a way to align a designated subject, such as the car in this example, pattern recognition and segmentation algorithms may be used that are well known to those skilled in the art, and defined in current literature. Alternatively, a tracking signal that is transmitted from the subject can be used to convey its position.	The area or objects in the sequence of images that are not the main subject, and which are intentionally blurred in the final video.
Blur free (Claim 1, Claim 8, Claim 15)	In another embodiment, the present invention can prevent image distortion due to motion of the imaging device or subject at relatively slow shutter speeds, resulting in a substantially undistorted image. A fourth embodiment of the invention compensates for movement of the imager or the subject by adjusting the position of the image sensor during image capture, according to the inverse of the transfer function describing the imager or subject motion, or both.	A state where the main subject appears sharp and without motion-induced distortion in the modified image.
Main subject (Claim 1, Claim 8, Claim 15)	As a way to align a designated subject, such as the car in this example, pattern recognition and segmentation algorithms may be used that are well known to those skilled in the art, and defined in current literature. Alternatively, a tracking signal that is transmitted from the subject can be used to convey its position. Alternatively, the user can indicate, such as by an indicator in a viewfinder, which object in the field of view is the designated subject to be kept blur-free.	A designated object or area within the sequence of images that is intended to be in focus and free from blur in the final video.
Modified images (Claim 1, Claim 8, Claim 15)	The present invention processes image data in order to correct an image for distortion caused by imager movement or by movement of the subject being imaged. In another embodiment, the present invention can prevent image distortion due to motion of the imaging device or subject at relatively slow shutter speeds, resulting in a substantially undistorted image.	Images derived from the original sequence of images, where pixel values are recalculated to achieve a blur-free main subject and a blurred background.
Sequence of images (Claim 1, Claim 8, Claim 15)	Capturing and recording a photograph, for example by a camera, involves gathering the light reflected or emanating from a subject, passing it through an optical system, such as a series of lenses, and directing it onto a light sensitive recording medium. A typical recording medium in traditional analog photography is a film that is coated with light sensitive material. During processing of the exposed film, the image is fixed and recorded. In digital cameras, the recording medium is typically a dense arrangement of light sensors, such as a Charge-Coupled Device (CCD) or a CMOS sensor.	A series of captured images, represented by pixel data, stored in memory.

Litigation Cases New

US Latest litigation cases involving this patent.

Case Number	Filing Date	Title
3:23-cv-00673	Apr 14, 2023	Clear Imaging Reasearch, LLC v. Apple Inc.

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US11627391

Application Number: US17514486A
Filing Date: Oct 29, 2021
Publication Date: Apr 11, 2023
External Links: Slate, USPTO, Google Patents

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