Vertical compensation in a moving camera

• US 6,781,623 B1
• Filed: 07/13/2000
• Issued: 08/24/2004
• Est. Priority Date: 07/19/1999
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Thomas, David
• Primary Examiner(s): Christensen, Andrew
• Assistant Examiner(s): GENCO, BRIAN C
• Application Number:
  US09/615,117
• Time in Patent Office: 1,503 Days
• Field of Search: 348/208.99, 348/208.1, 348/208.2, 348/208.4, 348/208.5, 348/208.6, 348/208.7, 345/649, 345/651, 345/655, 345/656, 345/657, 382/293, 382/294, 382/295, 382/296
• US Class Current: 348/208.4
• CPC Class Codes: H04N 2007/145 Handheld terminals
• CPC Class Codes: H04N 23/63 by using electronic viewfinders
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display

Abstract

A hand-held device comprising a housing (10) shaped and dimensioned to allow the device to be hand held, a display (12) secured to the housing for displaying moving pictures on a frame-by-frame basis, and a camera (16, 18) having an optical axis (O) extending generally away from the display to image a person who is viewing the display. The hand-held device further comprises a sensor (20) configured to determine a rotational angle between an alignment axis (V) of the hand-held device and a reference alignment axis in real space. Alternative embodiments use a reference alignment axis obtained on the basis of data content of the images, as determined by image processing techniques. In this way, subjective picture quality can be improved by compensating for vertical mis-alignment of the image content of the frames obtained by the camera.

Claims

1. An image processing apparatus, comprising:

a digital signal processor for processing a sequence of image frames collectively forming a motion picture, wherein the digital signal processor is arranged to;

determine a vertical alignment axis for each frame of the sequence from an analysis of the data content of that frame, wherein the analysis includes the digital signal processor arranged to;

identify perpendicular lines between data objects in the frame; and

evaluate the intersection of the perpendicular lines to determine the vertical alignment axis in the frame;

apply a rotational transform to each frame to map the vertical alignment axis determined by the analysis onto a fixed alignment axis of the frame; and

output the sequence of image frames thus transformed to compensate for vertical misalignment of the data content of the frames.

2. An image processing apparatus according to claim 1, further comprising:

(a) a housing shaped and dimensioned to allow the device to be hand held;

(b) a camera arranged in the housing so as to define an optical axis extending away from the housing, the camera including a detector comprising an array of light sensitive elements for obtaining respective pixels of an image frame and an output of an electronic signal corresponding to plural image frames; and

(c) the digital signal processor arranged in the housing and operatively connected on the output of the camera to apply rotational transformations to frames obtained by the camera, thereby to compensate for vertical misalignment of the data content of the frames.

3. An image processing apparatus according to claim 2, further comprising:

(d) a drive for removably receiving a data carrier which, when loaded in the drive, is in operative communication with the digital signal processor to allow storage of the sequence of image frames after transformation to compensate for vertical misalignment of the data content of the frames.

4. An image processing apparatus according to claim 2, further comprising:

(d) a data carrier arranged in operative communication with the digital signal processor to allow storage of the sequence of image frames after transformation to compensate for vertical misalignment of the data content of the frames; and

(e) an output connected to the data carrier to allow sequences of image frames stored in the data carrier to be output from the device.

5. An image processing apparatus according to claim 1, further comprising:

(a) an input stage for receiving image frames;

(b) a display connected to the input stage so as to display image frames received by the input stage as a motion picture; and

(c) the digital signal processor operatively connected between the input stage and the display, thereby to output to the display a sequence of image frames transformed to compensate for vertical misalignment of the data content of the frames received at the input stage.

6. An image processing apparatus according to claim 1, further comprising:

a receiver for receiving sequences of image frames;

the digital signal processor arranged to receive sequences of image frames from the receiver; and

a transmitter for outputting a sequence of image frames transformed by the image processing apparatus to compensate for vertical misalignment of the data content of the frames received at the input stage.

7. An image processing method, comprising:

receiving a sequence of image frames taken by a camera;

determining a vertical alignment axis for each frame of the sequence from an analysis of data content of that frame, the analysis comprising;

identifying perpendicular lines between data objects in the frame; and

evaluating the intersection of the perpendicular lines to determine the vertical alignment axis in the frame;

applying a rotational transform to each frame through an angle determined from misalignment between the vertical alignment axis and a fixed alignment axis of the frame; and

outputting the sequence of image frames thus transformed to compensate for vertical misalignment of the image content of the frames.

8. A method according to claim 7, wherein the perpendicular lines are identified by using a contrast technique to isolate boundaries of the data objects.