Focusing device

• US 20040257461A1
• Filed: 08/11/2004
• Published: 12/23/2004
• Est. Priority Date: 08/07/2002
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Toyomura, Kouichi
• Granted Patent: US 7,593,054 B2
• Time in Patent Office: Days
• US Class Current: 348/345
• CPC Class Codes: G02B 7/102 controlled by a microcomputer cameras with interchangeable lenses G03B17/14
• CPC Class Codes: G02B 7/28 Systems for automatic generation of focusing signals
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: H04N 23/673 based on contrast or high frequency components of image signals, e.g. hill climbing method

Abstract

A focusing apparatus including a focus signal detection circuit that generates a focus signal indicating the degree of focusing, an in-focus direction decision circuit that generates an in-focus direction signal indicating whether a focusing lens moved for focusing is on a far side or near side viewed from the in-focus position using the generated focus signal at predetermined time intervals, in-focus direction memory for storing the in-focus direction signal generated at predetermined time intervals, and a lens control amount calculation circuit and an in-focus vicinity decision circuit that controls the movement of the focusing lens based on a stored immediately preceding predetermined number of in-focus direction signals according to a predetermined rule.

Claims

1. A focusing apparatus comprising:

focus signal generating means of generating a focus signal indicating the degree of focusing;

in-focus direction signal generating means of generating an in-focus direction signal indicating whether a focusing lens moved for focusing is on a far side or near side viewed from an in-focus position using said generated focus signal at predetermined time intervals;

in-focus direction signal storing means of storing said in-focus direction signal generated at the predetermined time intervals; and

focusing lens movement controlling means of controlling movement of said focusing lens based on said stored immediately preceding predetermined number of in-focus direction signals according to a predetermined rule.

2. The focusing apparatus according to claim 1, wherein said predetermined rule is a rule to reduce the speed of movement of said focusing lens as the difference between (1) the number of in-focus direction signals, out of said stored immediately preceding predetermined number of in-focus direction signals, indicating that said moved focusing lens is on the far side viewed from the in-focus position and (2) the number of in-focus direction signals, out of said stored immediately preceding predetermined number of in-focus direction signals, indicating that said moved focusing lens is on the near side viewed from the in-focus position, is decreased.

3. The focusing apparatus according to claim 2, wherein the movement of said focusing lens is stopped (a) after a predetermined time has elapsed after said difference falls below a predetermined value or (b) after said difference falls below a predetermined value a predetermined number of times consecutively.

4. The focusing apparatus according to claim 3, further comprising:

focus signal level data storing means of storing focus signal level data on the focus signal level of a focus signal when said stored in-focus direction signal is generated;

focusing lens position data storing means of storing focusing lens position data on the position of said focusing lens where a focus signal having a focus signal level at which said focus signal level data is stored is generated; and

focusing lens position correcting means of correcting the position of said focusing lens whose movement is stopped to the position of said focusing lens, of the positions of said focusing lens at which said focusing lens position data is stored, where a focus signal having a maximum focus signal level out of the focus signal levels at which said focus signal level data is stored is generated.

5. The focusing apparatus according to claim 3, wherein only when the focus signal level of said generated focus signal is equal to or higher than a predetermined value, the movement of said focusing lens is controlled based on said stored immediately preceding predetermined number of in-focus direction signals according to said predetermined rule.

6. The focusing apparatus according to claim 3, further comprising focusing lens position detecting means of detecting the position of said moved focusing lens,

wherein the movement of said focusing lens is controlled considering said detected position of the focusing lens.

7. A focusing method comprising:

a focus signal generating step of generating a focus signal indicating the degree of focusing;

an in-focus direction signal generating step of generating an in-focus direction signal indicating whether a focusing lens moved for focusing is on a far side or near side viewed from an in-focus position using said generated focus signal at predetermined time intervals;

an in-focus direction signal storing step of storing said in-focus direction signal generated at the predetermined time intervals; and

a focusing lens movement controlling step of controlling movement of said focusing lens based on said stored immediately preceding predetermined number of in-focus direction signals according to a predetermined rule.

8. A program for causing a computer to execute the focusing method according to claim 7 comprising a focus signal generating step of generating a focus signal indicating the degree of focusing, an in-focus direction signal generating step of generating an in-focus direction signal indicating whether a focusing lens moved for focusing is on a far side or near side viewed from an in-focus position using said generated focus signal at predetermined time intervals, an in-focus direction signal storing step of storing said in-focus direction signal generated at the predetermined time intervals, and a focusing lens movement controlling step of controlling movement of said focusing lens based on said stored immediately preceding predetermined number of in-focus direction signals according to a predetermined rule.

9. A recording medium that stores the program according to claim 8 and can be processed by a computer.