Method of automatically tracking and photographing celestial objects and photographic apparatus employing this method

• US 8,447,071 B2
• Filed: 05/24/2011
• Issued: 05/21/2013
• Est. Priority Date: 05/25/2010
• Status: Expired due to Fees

• Current Assignee: PENTAX RICOH IMAGING COMPANY, LTD.
• Original Assignee: Pentax Ricoh Imaging Americas Corporation (Ricoh Company Limited)
• Inventors: Ohta, Makoto
• Primary Examiner(s): BHATNAGAR, ANAND P
• Application Number:
  US13/114,320
• Publication Number:
  US 20110293139A1
• Time in Patent Office: 728 Days
• Field of Search: 382/100, 382/103, 382/106, 348/135, 348/143, 348/144, 348169-172, 342/118, 342/139, 342/140
• US Class Current: 382/103
• CPC Class Codes: G01S 3/7867 Star trackers navigation using star trackers G01C21/025
• CPC Class Codes: G06V 10/757 Matching configurations of points or features
• CPC Class Codes: H04N 23/61 based on recognised objects

Abstract

A method of automatically tracking and photographing a celestial object, includes inputting latitude information, photographing azimuth angle information and photographing elevation angle information of a photographic apparatus; inputting star map data of a certain range including data on a location of a celestial object from the latitude information, the photographing azimuth angle information and the photographing elevation angle information; calculating a deviation amount between a location of the celestial object that is imaged in a preliminary image obtained by the photographic apparatus and the location of the celestial object which is defined in the input star map data; correcting at least one of the photographing azimuth angle information and the photographing elevation angle information using the deviation amount; and performing a celestial-object auto-tracking photographing operation based on the corrected at least one of the photographing azimuth angle information and the photographing elevation angle information.

Claims

1. A method of automatically tracking and photographing an arbitrarily-selected celestial object, comprising:

performing a preliminary photographing operation by directing a photographic apparatus toward the celestial object;

inputting latitude information, photographing azimuth angle information and photographing elevation angle information of said photographic apparatus obtained during said preliminary photographing operation;

inputting star map data of a range corresponding to the input said latitude information, said photographing azimuth angle information and said photographing elevation angle information;

calculating a deviation amount between a location of the celestial object that is imaged in a preliminary image obtained by said preliminary photographing operation and a location of the celestial object which is defined in the input said star map data;

correcting at least one of said photographing azimuth angle information and said photographing elevation angle information using said deviation amount; and

performing a celestial-object auto-tracking photographing operation based on the corrected said at least one of said photographing azimuth angle information and said photographing elevation angle information.

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

obtaining a preliminary image by performing a preliminary photographing operation using said photographic apparatus, which is directed toward the celestial object;

calculating a location of the celestial object that is imaged in the obtained said preliminary image;

inputting photo date information, latitude information, photographing azimuth angle information and photographing elevation angle information of said photographic apparatus obtained during said preliminary photographing operation;

inputting star map data of a range corresponding to the input said photo date information, said latitude information, said photographing azimuth angle information and said photographing elevation angle information;

calculating a deviation amount, in a predetermined coordinate system, between the calculated said location of the celestial object that is imaged in said obtained preliminary image and said location of the celestial object which is defined in the input said star map data;

correcting at least one of said photographing azimuth angle information and said photographing elevation angle information using said deviation amount; and

performing said celestial-object auto-tracking photographing operation based on corrected said at least one of said photographing azimuth angle information and said photographing elevation angle information.

3. The method according to claim 2, further comprising:

calculating a posture of said photographic apparatus that is achieved when said preliminary photographing operation is performed using said deviation amount,

wherein said performing of said celestial-object auto-tracking photographing operation comprises performing said celestial-object auto-tracking photographing operation based on said posture of said photographic apparatus.

4. The method according to claim 2, further comprising:

inputting information on the focal length of said photographing optical system,

wherein said calculating of said location of the celestial object comprises calculating said location of the celestial object in said predetermined coordinate system in said preliminary image from the focal length information, said date information, said latitude information, said photographing azimuth angle information and said photographing elevation angle information.

5. The method according to claim 2, wherein said photographic apparatus comprises an azimuth angle sensor and a gravity sensor, from which said photographing azimuth angle information and said photographing elevation angle information are input, respectively.

6. The method according to claim 2, wherein said photographic apparatus comprises a GPS unit, from which said latitude information is input.

7. The method according to claim 2, wherein said star map data includes data on right ascensions and declinations of celestial objects including the celestial object which is to be photographed.

8. The method according to claim 7, wherein said predetermined coordinate system is an X-Y coordinate system on said imaging plane,

wherein said method further comprises:

converting coordinates of the celestial object data which is provided in said star map data to coordinates on said imaging plane; and

calculating a photographing azimuth angle and a photographing elevation angle of each of the celestial objects from said latitude information, hour angles of the celestial objects, which are obtained by converting said right ascensions, and said declinations of the celestial objects according to the following equations;

A=arctan(sin H/(cos ε

×

tan δ

−

sin ε

×

cos H))

h=arcsin(sin ε

×

sin δ

+cos ε

×

cos δ

×

cos H)

wherein A designates said photographing azimuth angle,

h designates said photographing elevation angle,

ε

designates said latitude,

H designates said hour angle of each of the celestial objects, and

δ

designates said declination of each of the celestial objects.

9. The method according to claim 8, further comprising:

calculating a difference Δ

A between said photographing azimuth angle ‘

A’

determined from said star map data and input said photographing azimuth angle As and a difference Oh between said photographing elevation angle h determined from said star map data and input said photographing elevation angle hs from the following equations;

Δ

A=A−

As

Δ

h=h−

hs,

wherein a center of said imaging plane is defined as an arithmetic image center point O; and

calculating coordinates (X, Y) using said focal length information f from the following equations (I) and (II);

X=f×

tan(arccos(sin²(hs+Δ

h/2)+cos²(hs+Δ

h/2)×

cos(Δ

A))) 

 

(I)

Y=f×

tan Δ

h 

 

(II).

10. The method according to claim 9, further comprising:

converting a position of each celestial object obtained in said preliminary image to an amount of coordinate movement (Δ

X, Δ

Y) on said imaging plane according to the following equations;

Δ

X=f×

tan(arccos(sin²(hs+Δ

h/2)+cos²(hs+Δ

h/2)×

cos(Δ

α

)

Δ

Y=f×

tan Δ

h.

11. The method according to claim 10, further comprising:

calculating amounts of positional deviations Δ

X and Δ

Y of said each celestial object from a corresponding celestial object in said star map data in horizontal and vertical directions, respectively, and

calculating, based on said amounts of positional deviations Δ

X and Δ

Y thus calculated, an amount of deviation Δ

h of said photographing elevation angle that is obtained upon said preliminary photographing operation being performed from said arithmetic image center point and an amount of deviation Δ

A of said photographing azimuth angle that is obtained upon said preliminary photographing operation being performed from said arithmetic image center point according to the following equations;

Δ

h=arctan(Δ

Y/f)

Δ

A=arccos((cos(arctan(Δ

X/f))−

cos²(hs+arctan(Δ

Y/f)/2))/cos²(hs+arctan(Δ

Y/f)/2)).

12. The method according to claim 2, further comprising calculating an azimuth-angle-direction driving speed dA/dt, an elevation-angle-direction driving speed dh/dt and an rotational driving speed dθ

/dt when moving said predetermined imaging area in said horizontal and vertical directions and rotating said predetermined imaging area in a rotational direction from the following equations (i), (j) and (k) so that said image of the celestial object that is formed on said imaging surface via said photographing optical system becomes stationary relative to said predetermined imaging area of said imaging surface during said celestial-object auto-tracking photographing operation;

dA/dt=sin ε

−

cos ε

×

tan h×

cos A 

 

(i)

dh/dt=sin A×

cos E 

 

(j)

dθ

/dt=−

cos A×

cos ε

/cos h. 

 

(k)

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

an inputter which obtains a preliminary image by directing said photographic apparatus toward an arbitrarily-selected celestial object and performing a preliminary photographing operation using said photographic apparatus, and inputs photo date information, latitude information, photographing azimuth angle information and photographing elevation angle information of said photographic apparatus obtained during said preliminary photographing operation;

an image-sensor mover which linearly moves said image sensor in directions orthogonal to an optical axis of said photographing optical system and rotates said image sensor about said optical axis; and

a controller which controls operations of said photographic apparatus,

wherein said controller inputs star map data of a range corresponding to the input said photo date information, said latitude information, said photographing azimuth angle information and said photographing elevation angle information;

calculates a deviation amount between said location of the celestial object that is obtained from said preliminary image and said location of the celestial object which is defined in the input said star map data;

corrects at least one of said photographing azimuth angle information and said photographing elevation angle information using said deviation amount; and

performs said celestial-object auto-tracking photographing operation based on corrected said at least one of said photographing azimuth angle information and said photographing elevation angle information.