Image processor and face detector using the same

• US 20050265626A1
• Filed: 04/04/2005
• Published: 12/01/2005
• Est. Priority Date: 05/31/2004
• Status: Active Grant

• Current Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Endo, Junpei, Furukawa, Satoshi, Ikari, Motoo, Hagio, Kenichi
• Granted Patent: US 7,948,524 B2
• Time in Patent Office: Days
• US Class Current: 382/274
• CPC Class Codes: G06V 40/161 Detection; Localisation; Normalisation
• CPC Class Codes: H04N 23/611 where the recognised objects include parts of the human body
• CPC Class Codes: H04N 23/71 Circuitry for evaluating the brightness variation
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 23/76 by influencing the image signals

Abstract

An image processor is provided, which has the capability of detecting an object such as a human face from an image taken against the sun with high accuracy. An image signal provided from an image pickup unit is adjusted at an analog gain by an image adjuster. An output of the image adjuster is converted into a digital image data, and stored in a memory. A feature of the object is extracted from this digital image data to detect an object area in the image. When the object area is not detected, an analog-gain controller sends an analog-gain control signal to the image adjuster in a feedback manner-such that the image signal provided from the image pickup unit is adjusted at a different analog gain. Thus, the treatment of detecting the object area is repeated at different analog gains.

Claims

1. An image processor comprising:

image pickup means configured to take an image of an object;

an image adjuster configured to adjust an image signal provided from said image pickup means at an adjustment level;

an A/D converter configured to convert an output of said image adjuster into a digital image data;

an object detector configured to extract a feature of said object from said digital image data to detect an object area in the image; and

an adjustment-level controller for sending an adjustment-level control signal to said image adjuster in a feedback manner such that the image signal provided from said image pickup means is adjusted at a different adjustment level when the object area is not detected by said object detector.

2. The image processor as set forth in claim 1 further comprising a brightness adjuster for determining a brightness of the object area detected by said object detector, and allowing said adjustment-level controller to send to said image adjuster the adjustment-level control signal determined such that the brightness becomes a predetermined brightness.

3. The image processor as set forth in claim 1, wherein the adjustment level is provided by an analog gain.

4. The image processor as set forth in claim 1, wherein the adjustment level is provided by a speed of an electronic shutter of said image pickup means.

5. The image processor as set forth in claim 1, wherein said adjustment-level controller determines the adjustment-level control signal by switching a first control period where the adjustment level is provided by a speed of an electronic shutter of said image pickup means, and a second control period where the adjustment level is provided by an analog gain.

6. The image processor as set forth in claim 1 further comprising a brightness detector for detecting a brightness of an entire image pickup area taken by said image pickup unit, and wherein said adjustment-level controller determines a change amount of the adjustment-level control signal according to the brightness.

7. The image processor as set forth in claim 1, wherein said object detector extracts the feature of a face as said object from said digital image signal to detect a face area as said object area.

8. The image processor as set forth in claim 1, wherein said object detector comprises a reference-data memory for storing a template image of said object, and an object-area detecting portion for comparing said digital image data with said template image to calculate a degree of correlation therebetween, and determining an area having a higher degree of correlation than a threshold value as said object area.

9. The image processor as set forth in claim 1 further comprising outline extracting means for extracting an outline of said object, and wherein said object detector detects the object area when the outline of said object is extracted by said outline extracting means.

10. The image processor as set forth in claim 1 further comprising light-source determining means for determining whether a light source illuminating said object is the sun, and said object detector detects the object area when the light source is determined as the sun by said light-source determining means.

11. The image processor as set forth in claim 1, further comprising illumination-intensity measuring means for determining an illumination intensity of an image pickup area taken by said image pickup means, and light irradiating means for irradiating an auxiliary light to the image pickup area when the illumination intensity is smaller than a predetermined value.

12. The image processor as set forth in claim 1, wherein said adjustment-level controller sends to said image adjuster an initial adjustment-level control signal such that the image signal provided from said image pickup means is initially adjusted at an initial adjustment level that is an intermediate value between maximum and minimum values of a changeable range of said adjustment level, and wherein said adjustment-level controller determines the adjustment-level control signal from an adjustment-level control range set according to an average brightness of an entire area of the image adjusted at the initial adjustment level.

13. The image processor as set forth in claim 1, wherein said adjustment-level controller sends to said image adjuster an initial adjustment-level control signal such that the image signal provided from said image pickup means is initially adjusted at an initial adjustment level that is a maximum value of a changeable range of said adjustment level, and wherein said adjustment-level controller determines the adjustment level control signal such that the adjustment level changes from the maximum value toward a minimum value of the changeable range in a step-by-step manner.

14. The image processor as set forth in claim 2, wherein when a plurality of object areas are detected in the image by said object detector, said brightness adjuster determines the brightness of the object area having the largest area.

15. The image processor as set forth in claim 2, wherein when a plurality of object areas are detected in the image by said object detector, said brightness adjuster determines an average brightness of the object areas, and wherein said adjustment-level controller determines the adjustment-level control signal such that the average brightness becomes to a predetermined brightness.

16. The image processor as set forth in claim 2, wherein when a plurality of object areas are detected in the image by said object detector, said brightness adjuster assigns a weight to the brightness depending on size of said object area, and calculates a weighted average of the brightness, and wherein said adjustment-level controller determines the adjustment-level control signal such that the weighted average becomes to a predetermined value.

17. A face detector comprising:

image pickup means configured to take an image including a face as an object;

an image adjuster configured to adjust an image signal provided from said image pickup means at an adjustment level that is at least one of an analog gain and a speed of an electronic shutter of said image pickup means;

an A/D converter configured to convert an output of said image adjuster into a digital image data;

a face-area detector configured to extract a feature of said face from said digital image data to detect a face area in the image;

an adjustment-level controller for sending an adjustment-level control signal to said image adjuster in a feed-back manner such that the image signal provided from said image pickup means is adjusted at a different adjustment level when the face area is not detected by said face-area detector; and

a brightness adjuster for determining a brightness of the face area detected by said face-area detector, and allowing said adjustment-level controller to send to said image adjuster the adjustment-level control signal determined such that the brightness becomes a predetermined brightness.