Apparatus and method for storing and reading digital images

• US 20010022862A1
• Filed: 01/19/2001
• Published: 09/20/2001
• Est. Priority Date: 01/20/2000
• Status: Active Grant

• Current Assignee: Axis AB (Canon Inc.)
• Original Assignee: Axis AB (Canon Inc.)
• Inventors: Alm, Carl-Axel
• Granted Patent: US 6,829,395 B2
• Time in Patent Office: Days
• US Class Current: 382/305
• CPC Class Codes: H04N 19/507 using conditional replenishment
• CPC Class Codes: H04N 7/183 for receiving images from a single remote source

Abstract

An apparatus for storing digital images has a storage device [(134, 136) ] for storing a current reference image and a plurality of differential images, and an image processing device [(132) ] coupled to the storage device. The image processing device receives an individual digital image, determines a difference between the individual image and the current reference image, and stores this difference as a differential image in the storage device. The apparatus also has reference image updating means [(132)] for determining when to generate a new reference image, for generating the new reference image, for replacing the current reference image with the new reference image, and for storing the new reference image as current reference image in the storage device [(134, 136)].

Claims

1. An apparatus (130;

230) for storing digital images (300), comprising a storage device (134, 136;

234, 236) capable of storing a current reference image (310) and a plurality of differential images (320), and an image processing device (132, 244) coupled to the storage device, wherein the image processing device is adapted to receive an individual digital image (300), determine a difference between the individual image and the current reference image (310), and store this difference as a differential image (320) in the storage device, characterized by;

reference image updating means (132;

232, 244) for determining when to generate a new reference image (310), for generating the new reference image, for replacing the current reference image with the new reference image, and for storing the new reference image as current reference image in the storage device (134, 136;

234, 236).

2. An apparatus as in

claim 1

, wherein the image processing device (132;

244) is adapted to compress the differential image (310) before supplying it to the storage device (134, 136;

234, 236).

3. An apparatus as in

claim 1

or

2

, wherein the image processing device (132;

244) is adapted to store a reference to the current reference image (310) together with each differential image (320) in the storage device (134, 136;

234, 236).

4. An apparatus as in any of claims 1-3, wherein the storage device comprises a magnetic or optical storage device, preferably a hard disk (134;

234).

5. An apparatus as in

claim 4

, wherein the differential images (320) are stored in the magnetic or optical storage device (134;

234).

6. An apparatus as in any of claims 1-5, wherein the storage device comprises an electronic memory (136;

236), preferably a random access memory (RAM).

7. An apparatus as in

claim 6

, wherein the current reference image (310) is stored in the electronic memory (136;

236).

8. An apparatus as in

claim 6

or

7

, wherein old reference images, which have been replaced by a new reference image and are no longer a current reference image, are stored in the magnetic or optical storage device (134;

234).

9. An apparatus as in any of claims 1-8, wherein the reference image updating means (132;

232, 244) is adapted to generate a new reference image (310), when a predetermined time period has lapsed, since the current reference image was produced.

10. An apparatus as in any of claims 1-8, wherein the reference image updating means (132;

232, 244) is adapted to generate a new reference image (310), when a differential image (300) is larger than a predetermined number of bytes.

11. An apparatus as in any preceding claim, wherein the image processing device (132;

244) comprises a programmable logic processor, preferably a microprocessor or a digital signal processor.

12. An apparatus as in

claim 11

, wherein the reference image updating means (132;

232, 244) is implemented by a programmable logic processor.

13. An image reading apparatus (130;

230), comprising a storage device (134, 136;

234, 236) capable of storing a current reference image (310) and a plurality of differential images (320), and an image processing device (132;

244) coupled to the storage device, wherein the image processing device is adapted to read an individual differential image (320) from the storage device and produce a non-differential image (300) by adding the individual differential image to the current reference image (310), characterized in that;

the storage device (134;

234) is adapted to store a plurality of reference images (310), as well as for each individual differential image (320) an identifying reference to one of the reference images; and

the image processing device (132;

244) is adapted, when reading an individual differential image from the storage device, to read a particular one of the reference images, as identified by the identifying reference, and use this particular reference image as current reference image when producing the non-differential image.

14. An image reading apparatus as in

claim 13

, wherein the storage device comprises a first storage medium (136;

236) for storing the current reference image (310) and a second storage medium (134;

234) for storing the plurality of reference images (310) as well as the plurality of differential images (320).

15. An image reading apparatus as in

claim 14

, wherein the first storage medium is an electronic memory (136;

236), preferably a random access memory (RAM), and wherein the second storage medium is a magnetic or optical storage device, preferably a hard disk (134;

234).

16. A method (400) of storing digital images, wherein an individual digital image (300) is received, a difference is determined between the individual image and a current reference image (310), and this difference is stored as a differential image (320), characterized by the steps of:

determining (600) when to generate a new reference image (310),

producing (500) the new reference image, and

replacing the current reference image with the new reference image.

17. A method as in

claim 16

, wherein the step (600) of determining when to generate a new reference image (310) is performed by checking whether a predetermined time period has lapsed, since the current reference image was produced.

18. A method as in

claim 17

, wherein the step (600) of determining when to generate a new reference image (310) is performed by checking whether a differential image (320) is larger than a predetermined number of bytes.

19. A method as in any of claims 16-18, wherein the step (500) of producing the new reference image (310) is performed by:

receiving (520) a plurality of digital images (300),

calculating (530) average pixel values for pixels at corresponding positions in the plurality of digital images, and

forming the new reference image by assigning the calculated average pixel values to the pixels of the new reference image.