Method of automatically tracking and photographing celestial objects, and celestial-object auto-tracking photographing apparatus

• US 8,761,460 B2
• Filed: 06/12/2012
• Issued: 06/24/2014
• Est. Priority Date: 06/17/2011
• Status: Active Grant

• Current Assignee: PENTAX RICOH IMAGING COMPANY, LTD.
• Original Assignee: Pentax Ricoh Imaging Americas Corporation (Ricoh Company Limited)
• Inventors: Ohta, Makoto
• Primary Examiner(s): Drennan, Barry
• Assistant Examiner(s): Mistry, Oneal R
• Application Number:
  US13/494,196
• Publication Number:
  US 20120321132A1
• Time in Patent Office: 742 Days
• Field of Search: None
• US Class Current: 382/118
• CPC Class Codes: G02B 23/16 Housings; Caps; Mountings; Supports, e.g. with counterweight
• CPC Class Codes: H04N 23/6811 based on the image signal
• CPC Class Codes: H04N 23/684 performed by controlling the image sensor readout, e.g. by controlling the integration time
• CPC Class Codes: H04N 23/687 by shifting the lens or sensor position
• CPC Class Codes: H04N 23/69 Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming

Abstract

A method of automatically tracking and photographing a celestial object, which moves due to diurnal motion, while moving an imaging area on an imaging surface of an image sensor so that an image of the celestial object becomes stationary, includes calculating theoretical linear movement amounts and a theoretical rotational angle amount of the imaging area per a specified time; obtaining a movable-amount data table which stores data on actual linearly-movable amounts and an actual rotatable amount of the imaging area; and setting an exposure time for completing a celestial-object autotracking photographing operation while moving the imaging area within the range of movement thereof by comparing the theoretical linear movement amounts and the theoretical rotational angle amount with the actual linearly-movable amounts and the actual rotatable amount of the imaging area stored in the movable-amount data table.

Claims

1. A method of automatically tracking and photographing a celestial object, which moves relative to a photographic apparatus due to diurnal motion, while moving an imaging area on an imaging surface of an image sensor so that an image of said celestial object, which is formed on said imaging surface of said image sensor via a photographing optical system, becomes stationary relative to said imaging area of said imaging surface during a tracking and photographing operation, said method comprising:

calculating, based on information on motion of said celestial object image on said imaging area, theoretical linear movement amounts of said imaging area in directions orthogonal to an optical axis per a specified period of time and a theoretical rotational angle amount of said imaging area about an axis parallel to said optical axis per said specified period of time;

obtaining a movable-amount data table which stores data on actual linearly-movable amounts of said imaging area in said directions orthogonal to said optical axis from a reference posture position of said imaging area and an actual rotatable amount of said imaging area about said axis parallel to said optical axis from said reference posture position in a range of movement of said imaging area; and

setting an exposure time for completing a celestial-object auto-tracking photographing operation while moving said imaging area within said range of movement thereof by comparing said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time with said actual linearly-movable amounts and said actual rotatable amount of said imaging area that are stored in said movable-amount data table, respectively.

2. The method according to claim 1, wherein said calculating of said theoretical linear movement amounts and said theoretical rotational angle amount comprises calculating said theoretical linear movement amounts and said theoretical rotational angle amount at each step while stepwisely increasing said specified period of time,

wherein said setting of said exposure time comprises:

sequentially determining whether or not said theoretical linear movement amounts and said theoretical rotational angle amount at said each step exceed said actual linearly-movable amounts and said actual rotatable amount that are stored in the movable-amount data table, respectively; and

setting said exposure time to a shorter time than said specified period of time at a specific step upon determining that at least one of said theoretical linear movement amounts and said theoretical rotational angle amount at said specific step exceeds said actual linearly-movable amounts and said actual rotatable amount, which are stored in said movable-amount data table, respectively.

3. The method according to claim 2, wherein said setting of said exposure time comprises setting said specified period of time at one step before said specific step as said exposure time upon determining that at least one of said theoretical linear movement amounts and said theoretical rotational angle amount at said specific step exceeds said actual linearly-movable amounts and said actual rotatable amount which are stored in said movable-amount data table, respectively.

4. The method according to claim 1, further comprising:

shifting an initial position of said imaging area before commencement of movement thereof in accordance with said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time.

5. The method according to claim 4, wherein said shifting of said initial position of said imaging area comprises shifting said initial position of said imaging area before commencement of movement thereof by linear movement amounts and a rotational angle amount in a direction opposite to a direction in the case of said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time.

6. The method according to claim 1, wherein said range of movement of said imaging area in a plane orthogonal to said optical axis is virtually partitioned and arranged into a matrix with a predetermined number of rows and a predetermined number of columns so that said movable-amount data table stores an actual rotatable amount of said imaging area in each partition in said matrix.

7. A celestial-object auto-tracking photographing apparatus for automatically tracking and photographing a celestial object, which moves relative to said celestial-object auto-tracking photographing apparatus due to diurnal motion, while moving an imaging area on an imaging surface of an image sensor so that an image of said celestial object, which is formed on said imaging surface of said image sensor via a photographing optical system, becomes stationary relative to said imaging area of said imaging surface during a tracking and photographing operation, said celestial-object auto-tracking photographing apparatus comprising:

a movement data calculator which calculates, based on information on motion of said celestial object image on said imaging area, theoretical linear movement amounts of said imaging area in directions orthogonal to an optical axis per a specified period of time and a theoretical rotational angle amount of said imaging area about an axis parallel to said optical axis per said specified period of time;

a movable-amount data table which stores data on actual linearly-movable amounts of said imaging area in said directions orthogonal to said optical axis from a reference posture position of said imaging area and an actual rotatable amount of said imaging area about said axis parallel to said optical axis from said reference posture position in a range of movement of said imaging area; and

an exposure time setter which sets an exposure time for completing a celestial-object auto-tracking photographing operation while moving said imaging area within said range of movement thereof by comparing said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time with said actual linearly-movable amounts and said actual rotatable amount of said imaging area that are stored in said movable-amount data table.

8. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said movement data calculator calculates said theoretical linear movement amounts and said theoretical rotational angle amount at each step while stepwisely increasing said specified period of time,

wherein said exposure time setter sequentially determines whether or not said theoretical linear movement amounts and said theoretical rotational angle amount at said each step exceed said actual linearly-movable amounts and said actual rotatable amount, which are stored in the movable-amount data table, respectively, and sets said exposure time to a shorter time than said specified period of time at a specific step upon determining that at least one of said theoretical linear movement amounts and said theoretical rotational angle amount at said specific step exceeds said actual linearly-movable amount and said actual rotatable amount, which are stored in said movable-amount data table, respectively.

9. The celestial-object auto-tracking photographing apparatus according to claim 8, wherein said exposure time setter sets said specified period of time at one step before said specific step as said exposure time upon determining that at least one of said theoretical linear movement amounts and said theoretical rotational angle amount at said specific step exceeds said actual linearly-movable amount and said actual rotatable amount, which are stored in said movable-amount data table, respectively.

10. The celestial-object auto-tracking photographing apparatus according to claim 7, further comprising an imaging area shifter which shifts an initial position of said imaging area before commencement of movement thereof in accordance with said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time.

11. The celestial-object auto-tracking photographing apparatus according to claim 10, wherein said imaging area shifter shifts said initial position of said imaging area before commencement of movement thereof by linear movement amounts and a rotational angle amount in a direction opposite to a direction of said theoretical linear movement amounts and said theoretical rotational angle amount of said imaging area per said specified period of time.

12. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said range of movement of said imaging area in a plane orthogonal to said optical axis is virtually partitioned and arranged into a matrix with a predetermined number of rows and a predetermined number of columns, and said movable-amount data table stores an actual rotatable amount of said imaging area in each partition in said matrix.

13. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said imaging area corresponds to an entire imaging area of said image sensor, and

wherein said celestial-object auto-tracking photographing apparatus further comprises an image sensor mover which linearly moves said image sensor in said directions orthogonal to said optical axis and rotates said image sensor about said axis that is parallel to said optical axis based on said theoretical linear movement amounts and said theoretical rotational angle amount that are calculated by said movement data calculator.

14. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said imaging area corresponds to a trimmed imaging area defined by electronically trimming a part of an entire imaging area of said image sensor, and

wherein said celestial-object auto-tracking photographing apparatus further comprises an imaging area mover which linearly moves said trimmed imaging area in said directions orthogonal to said optical axis and rotates said trimmed imaging area about said axis that is parallel to said optical axis based on said theoretical linear movement amounts and said theoretical rotational angle amount that are calculated by said movement data calculator.

15. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said imaging area corresponds to a trimmed imaging area defined by electronically trimming a part of an entire imaging area of said image sensor, and

wherein said celestial-object auto-tracking photographing apparatus further comprises a mover which moves said celestial object image relative to said celestial-object auto-tracking photographing apparatus by decentering part of said photographing optical system and rotates said trimmed imaging area about said axis that is parallel to said optical axis based on said theoretical linear movement amounts and said theoretical rotational angle amount that are calculated by said movement data calculator.

16. The celestial-object auto-tracking photographing apparatus according to claim 7, wherein said imaging area corresponds to a trimmed imaging area defined by electronically trimming a part of an entire imaging area of said image sensor, and

wherein said celestial-object auto-tracking photographing apparatus further comprises a mover which linearly moves said image sensor in said directions orthogonal to said optical axis and rotates said trimmed imaging area about said axis that is parallel to said optical axis based on said theoretical linear movement amounts and said theoretical rotational angle amount that are calculated by said movement data calculator.