JP2012089960A - Camera equipped with camera shake preventing mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera equipped with a camera shake preventing mechanism allowing a user to easily photograph with only a camera body, thus capable of solving problems in which an equatorial telescope is significantly large sized and inconvenient to carry, and a setting takes labor and time even though photographing without a light trail is possible because tracking of a star motion in synchronous with a diurnal motion of the heavenly body is possible if the equatorial telescope is used when photographing the heavenly body with a long-time exposure.SOLUTION: The camera equipped with the camera shake preventing mechanism comprises processes of: performing a long-time photographing as a preliminary photographing before an actual photographing; calculating a rotation axis and a motion aspect of a subject from a light trail of the obtained photographed image; and driving a camera shake correction at the time of actual photographing so as to cancel a motion of the subject during photographing by using the calculated value.

Description

  The present invention relates to control of a camera shake correction function during long exposure.

  In recent years, an increasing number of cameras have a camera shake correction mechanism for the purpose of reducing camera shake of a photographer. The camera opens the shutter when the release switch is pressed, and closes the shutter when the image sensor and the film are exposed to obtain a necessary amount of light. Camera shake is caused by the movement of the camera from when the shutter is opened until it is closed. The slower the shutter speed, the more noticeable the camera shake is due to the longer shutter opening time. In order to alleviate this, the movement of the camera is detected using a sensor such as a gyro, and the subject image is moved so as to cancel the movement during exposure, as if the subject image is not moving. What plays this role is the image stabilization mechanism.

  There are an optical type (lens shift type) and a sensor shift type as a camera shake correction mechanism in a digital camera. There are optical shift methods such as a lens shift method and a vari-angle method, but a lens shift method is often used. In the lens shift method, a part of the photographic lens is moved on the imaging element by moving the lens in the vertical and horizontal directions (decentering the optical axis) in a plane orthogonal to the photographic lens optical axis (a plane parallel to the imaging surface). The position of the formed subject image can be moved. In addition, the vari-angle method has a prism that can change the apex angle in the photographic lens optical system, and the subject image formed on the image sensor can be moved by moving the apex angle in the same way as the lens shift system. It is something to be made. In the sensor shift method, the position where the subject image is captured is moved by moving the sensor vertically and horizontally in a plane perpendicular to the optical axis of the photographing lens. The amount of movement of the subject image on the sensor is calculated from the focal length of the photographic lens by detecting the amount of movement of the camera in the vertical and horizontal directions using a gyro.

  These functions are intended to correct up / down / left / right image blur in a plane perpendicular to the optical axis of the photographic lens. Furthermore, the rotation is centered in the plane perpendicular to the optical axis of the photographic lens. Some have a mechanism for rotating the image sensor around the optical axis of the photographic lens with respect to direction blur.

  Next, regarding celestial photography, when photographing celestial objects, exposure to a long time such as 30 seconds or 1 minute is often performed due to the small amount of light from the stars. As the celestial body moves in a diurnal motion in accordance with the rotation of the earth, the stars do not become point images but become light trails when exposed for a long time. In order to prevent this, there are cases where photographing is performed using what is called an equator.

  The equatorial mount is designed to be able to track the movement of a celestial object that moves in a diurnal motion, and an astronomical telescope and camera are installed on it. The equatorial mount has two rotation axes: the ecliptic axis that moves with the rotation of the earth (moving along the east and west of the heavens) and the axis of declination (moving along the north and south of the heavens). ing. These axes are aligned with the direction and angle of the celestial North Pole (≈ North Star) using the scope provided for the equatorial mount, and then the red meridian and declination axes are rotated to the direction of the desired star. To follow the diurnal motion of the celestial body, only the red meridian axis needs to be rotated. There is also a motor that automatically rotates the red meridian axis and automatically tracks the celestial body so that it rotates about one round in 24 hours.

  Further, according to what is proposed in Patent Document 1, the total exposure time is determined from the brightness of the subject, the exposure time is divided into N exposures, and the images are translated and overlapped to obtain one sheet. This is an image.

JP2003-259184

  When shooting celestial objects with long exposures, the equatorial mount can be used to track the movement of stars in accordance with the diurnal movement of the celestial object, so that it is possible to shoot point images instead of light trails.

  However, the equatorial mount is quite large, and the one with automatic tracking function is even larger, so it is inconvenient to carry around. Also, setting is time consuming and time consuming, and it is very difficult to handle because it cannot be accurately tracked unless it is done correctly.

  In addition, there is a problem that only a part of the captured image can be used even when images are superimposed.

  In a camera equipped with a camera shake correction mechanism, a long-time shooting is performed as a preliminary shooting before the main shooting, and the rotation center and movement aspect of the subject are calculated from the light trace of the obtained shooting image. The camera shake correction is driven so as to cancel the movement of the subject during photographing using the value.

  According to the present invention, astronomical photography can be easily performed using only the camera body without using special equipment such as an equatorial mount. Also, you can enjoy shooting easily because no specialized knowledge is required for the settings.

The figure which shows the 1st Example of this invention Diagram showing camera shake prevention mechanism Figure showing the image of the celestial object A diagram showing the movement of celestial bodies Diagram showing the state of preliminary shooting Figure showing the movement of the celestial body and the state at the time of correction The figure which shows the 2nd Example of this invention Diagram showing the case of correcting only shift blur

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a first embodiment of the present invention. 101 is an MPU that is a central processing unit for controlling the operation of the camera, 102 is a photographing lens group for forming an image of a subject, and 103 is an imaging device that photoelectrically converts an image formed by the photographing lens group , 104 is a camera shake detection device for detecting the camera shake amount, and 105 is a shift camera shake correction device for correcting the camera shake amount detected by the camera shake detection device in the vertical and horizontal directions in the imaging plane. , 106 is a rotational shake correction device for correcting the amount of shake in the rotational direction, 107 is an internal memory for temporarily storing captured images and the like, and 108 is the final image data temporarily stored in the internal memory 107. Removable memory for storage.

  First, the camera shake correction mechanism is as shown in FIG. The imaging device 103 is mounted on the rotation correction stage 206, and the rotation correction stage 206 is rotatably held by the sensor stage 201a. A motor 202 provided on the sensor stage 201a rotates the rotation correction stage 206 via a gear 203. With such a rotational shake correction device 106, it is possible to correct the rotation direction with the center of the imaging screen of the imaging device 103 as the rotation center. The sensor stage 201 includes an X stage 201b that is movably held in a camera body (not shown) and a Y stage 201a that is movably held in an up / down direction on the X stage 201b. The sensor stage 201 can be moved in the vertical and horizontal directions by the actuator 204 that moves the Y stage 201a in the vertical direction (y-axis direction) and the actuator 205 that moves in the horizontal direction (x-axis direction). These sensor stage 201 and actuators 204 and 205 are combined to form a shift blur correction device.

  The camera body 100 is equipped with a shake detection device 104 for detecting the camera shake amount. The shake detection device 104 is a gyro (angular velocity sensor) or a gravity sensor (acceleration sensor), and detects how the camera body 100 is moving. The movement of the camera body 100 detected by the shake detection device 104 is analyzed by the MPU 101, and the shift shake correction device 105 and the rotation shake correction device 106 are operated in the opposite direction to the movement of the camera body 101. As a result, the camera body moves, but the imaging device 103 does not move relative to the subject, and an image without blurring can be captured on the imaging device 103.

  Next, I will talk about astronomical photography. When photographing a celestial body, since the amount of light is small, bulb photography with a shutter opened for a long time is often performed. Since the star seen from the earth is a point light source, it is as shown in Fig. 3 (a). However, when the camera is fixed on a tripod or the like and exposed for a long time, it becomes as shown in FIG. This is due to the relative position of the camera and the star fixed on the earth moving due to the rotation of the earth. This is called the “diurnal motion” of the star and cannot be avoided with a regular tripod. When shooting a bright star in a very short time, the movement can be almost ignored, but if you try to shoot a dark star, it will take a long exposure, so it will become a light trace as shown in Fig. 3 (b) or the light quantity is insufficient This means that even light trails cannot be taken.

  In order to compensate for this, a dedicated celestial platform called the equatorial mount is used to track the star according to the movement of the celestial body moving in the diurnal motion. The equatorial mount has two axes of rotation, which move with the rotation of the earth (moving along the east and west of the heavens) and the axis perpendicular to it (moving along the north and south of the heavens) It is necessary to match the latitude axis. The direction of these two axes changes depending on the place (latitude and longitude) where the celestial object is observed and the observation direction, so it cannot follow the movement of the star unless the two axes are accurately aligned at the observation place. When the two axes are exactly aligned with the declination axis and the meridian axis, the rest is turned to the desired direction using only the rotation of the two axes. To follow the stars, you only need to rotate the ecliptic axis and fix the declination axis. If the red meridian axis is rotated by a motor, automatic tracking can be performed, so that it can also be used for long exposure photography. However, an equatorial mount that can be automatically tracked with a large pedestal is much larger and cannot be easily carried around when shooting. In addition, since setting the axis is not easy, we would like the camera itself to have these functions in order to enjoy astronomical photography easily.

  Therefore, we propose a device that calculates the diurnal motion using the camera shake correction mechanism and automatically tracks it.

  First, fix the camera using a tripod. Detects the movement of the diurnal movement for automatic tracking before performing the main shooting.

  The diurnal motion can be followed by specifying the location of the rotation center of the star. In order to calculate the rotation center, an image exposed for a long time is analyzed. When the camera is fixed and exposed for a long time, a star light trace 402 is recorded as shown in FIG. The captured data is temporarily stored in the internal memory 107 and analyzed by the MPU 101. As shown in FIG. 4, when the light trace 402 is extended into a circle, this center position may be set as the rotation center 403. If there are several light traces in the recorded image, the center of rotation 403 can be obtained more accurately by calculating the average of these centers and taking the average.

The longer the light trace 402, the smaller the error in obtaining the center of rotation, but the longer the light trail 402, the longer the exposure time. Therefore, it is better to change the exposure time depending on the focal length of the lens so that the light trace 402 having a length sufficient to obtain the rotation center 403 can be recorded.
The center of rotation 403 can be calculated if the exposure is performed only once for a long time, but it is not known in which direction the star is rotating. Therefore, after a long exposure, another time is taken and another picture is taken. The second shooting does not need to be performed for a long time like the first shooting, and a short exposure enough to record stars is sufficient. FIG. 5 shows a state in which images of the first long exposure and the second short exposure are superimposed. In this figure, it can be seen that the light trace 404 of the second image is shown on the right side of the light trace 402 during the long exposure. As a result, it can be determined that the rotation direction is clockwise.

  In this way, it is possible to determine the rotation direction by shooting twice, but the rotation direction is determined by the latitude of shooting and the shooting direction. Therefore, the camera can have a means for measuring latitude and azimuth such as GPS (Global Positioning System) and azimuth magnetic needle, or can be determined by inputting by the photographer.

Next, a correction amount for operating the camera shake correction mechanism is calculated from the calculated rotation center 403 and the rotation direction.First, the calculated rotation center 403 of the star as shown in FIG. 0), and the center of the shooting screen 401 is (x ₀ , y ₀ ). A position (x ₂ , y ₂ ) after a point (x ₁ , y ₁ ) of a certain star rotates and moves around the rotation center 403 and after a certain time (angle) has passed. The rotated angle at this time is defined as θ.

Although it can be said that the rotation about the rotation center 403 of the star can be performed, the rotation blur correction device 106 provided in the camera body 100 can only rotate about the screen center (x ₀ , y ₀ ). Therefore, first, it is considered that only the vectors when moving from (x ₁ , y ₁ ) to (x ₂ , y ₂ ) by rotation of the rotational shake correcting device 106 are matched. In this case, the rotational blur correction device 106 has only to move the rotation amount by θ. Assuming that the position moved by θ rotation by the rotational shake correcting device 106 is (x ₃ , y ₃ ), (x ₃ , y ₃ ) can be expressed by the following relational expression.

x ₃ = x ₀ + (x ₁ -x ₀ ) cosθ + (y ₁ -y ₀ ) sinθ
y ₃ = y ₀ + (y ₁ -y ₀ ) cosθ- (x ₁ -x ₀ ) sinθ
The movement of (x ₁ , y ₁ ) → (x ₂ , y ₂ ) can be expressed as follows.

x ₂ = x ₁ cosθ + y ₁ sinθ
y ₂ = y ₁ cosθ- x ₁ sinθ
It is assumed that (x ₃ , y ₃ ) is moved up and down, left and right using the shift blur correction device 105 and moved to (x ₂ , y ₂ ).
_{X = x 2 - x 3 =} x 0 cosθ + y 0 sinθ- x 0
Y = y ₂ -y ₃ = y ₀ cosθ- x ₀ sinθ- y ₀
Therefore, if the rotational shake correction device 106 rotates −θ and the shift shake correction device 105 translates only (−X, −Y), both the moved position and the vector can be matched.
Since θ rotates 360 ° in an amount determined by time, that is, 24 hours (more precisely, 23 hours 56 minutes 4.09 seconds), for example, assuming that the correction operation is performed in steps of 0.1 seconds, 4.17 × 10 ⁻ A rotational movement of ⁴ ° and a shift movement (X, Y) with respect to the rotational movement may be performed. Since the movement of the celestial body is a constant speed movement, the rotational movement amount and the shift movement amount may always be the same amount at the same interval.
The image shot in this manner while being corrected is temporarily stored in the internal memory 107, transferred to and stored in the memory 108 after data conversion.

In this embodiment, the shift blur correction device 105 and the rotation blur correction device 106 are described as being attached to the imaging device 103, but the shift blur correction device 105 may be provided in the photographing lens group 102.
The taking lens group 102 may be removable.

FIG. 7 is a diagram showing a second embodiment of the present invention. The same reference numerals as those in the first embodiment serve the same function.
The difference from the first embodiment is that it does not include a rotational shake correction device. Most of the camera shake correction mechanisms provided in the optical apparatus are equipped with only the shift shake correction device 105.

  Without the rotational shake correction device, vector movement due to rotation cannot be matched as described above, so that even if correction is performed by the shift shake correction device 105, an error occurs. Since the vectors do not match, for example, when a close-up celestial object such as the moon is magnified, a pattern on the ground surface of the moon appears, so that the correction is not effective and the image is taken with rotational blurring. However, if the magnification is low, such as when shooting a celestial object at a long distance, it will not be a problem because it will be captured almost at a point.

  Further, when shooting for a long time, a position error occurs as shown in FIG. First, focusing on the operation of 402a, it is at the position of 402as at the start of exposure. If this carries out a diurnal movement, it will move to the position of 402ae. If only the shift movement is performed in accordance with this 402a, it will be understood that the end point of the locus is deviated by moving from the position of 402bs to the position of 402be with respect to the locus of movement of the celestial body of 402b. The only way to compensate for this is to shorten the shooting time and minimize the amount of movement.

  Therefore, in the case of a device having only the shift blur correction device 105, the shooting time for long-time shooting is set to be shorter than a predetermined amount. In addition, when the size of the celestial object to be photographed is small, rotational blurring is inconspicuous, so that the error can be reduced because the orbit of the celestial object can be approximated by a straight line by increasing the magnification factor. When the celestial body is large, the focal length of the photographic lens group 102 is set to a predetermined value or less in order to make rotation blur inconspicuous, or the focal length is set to be equal to or less than a predetermined value by calculating the image magnification of the celestial object To change. As a result, an error due to rotation can be reduced, and an image can be recorded without any problem.

Then, as mentioned above,
x ₂ = x ₁ cosθ + y ₁ sinθ
y ₂ = y ₁ cosθ- x ₁ sinθ
Just move.

Here, since (x ₁ , y ₁ ) can be any point on the screen because it does not involve rotational movement, considering the shift movement amount (X, Y) with (x ₀ , y ₀ ) as a representative value,
X = x ₀ cosθ + y ₀ sinθ
Y = y ₀ cosθ- x ₀ sinθ
Can be done. As described above, since θ is an amount determined by time, the correction amount can be calculated by determining the correction step.

100 Camera body
101 MPU
102 Shooting lens group
103 Imaging device
104 Shake detection device
105 Shift blur correction device
106 Rotational image stabilizer
107 Internal memory
108 Removable memory
201 Sensor stage
202 motor
203 Gear
204,205 Actuator
206 Rotation correction stage
401 Shooting area
402,404 Light trail
403 center of rotation

Claims (7)

Shooting for a long time as a preliminary shooting before the main shooting, calculating the rotation center (403) and movement aspect of the subject from the light trace of the obtained shooting image, and using the calculated values calculated during the main shooting A camera provided with an anti-shake mechanism, wherein the anti-shake mechanism (105, 106) is driven so as to cancel the movement of the subject.   2. The camera with an anti-shake mechanism according to claim 1, wherein the preliminary photographing is performed twice and the second photographing time is shorter than the first photographing time.   2. The camera shake prevention mechanism includes a mechanism that linearly moves in a biaxial direction perpendicular to the plane of the photographing screen and a mechanism that moves in a rotational direction substantially centered on the screen center. A camera equipped with 2 camera shake prevention mechanisms. The present camera shake prevention mechanism includes a mechanism that moves linearly in two orthogonal directions within the plane of the shooting screen and a mechanism that moves in a rotational direction substantially centered on the screen center. Item 3. A camera provided with the camera shake prevention mechanism according to Item 1 or 2. 3. The main photographing time camera shake prevention mechanism includes a mechanism that linearly moves in two orthogonal directions in the plane of the photographing screen, and the photographing time during the main photographing is set to a predetermined amount or less. Camera with camera shake prevention mechanism. The camera shake prevention mechanism according to claim 1 or 2, wherein the main-shooting-time camera shake prevention mechanism includes a mechanism that linearly moves in two orthogonal directions within the plane of the shooting screen, and the shooting magnification during the main shooting is set to a predetermined amount or less. Camera with prevention mechanism. The camera shake prevention mechanism for the actual shooting time is equipped with a mechanism that moves linearly in two orthogonal directions within the plane of the shooting screen, and if the subject size during the actual shooting is less than a predetermined amount, the focal length of the shooting lens should be increased. A camera provided with the camera shake prevention mechanism according to claim 1 or 2.