Equipment and methods for time-lapse astrophotography

Abstract

Method for capturing a time-lapse image sequence, wherein the method: moving an image recording device (10) into an initial orientation prior to taking a first multiple of photographs; and This includes taking an initial set of photographs, with each photograph of the initial set of photographs being taken as follows: the opening of a shutter (12) of an image recording device (10); while the shutter (12) of the image-taking device (10) is open, the movement of the image-taking device (10) to reduce the movement of a celestial body or celestial coordinate in the field of view of the image-taking device (10); closing the shutter (12) of the image recording device (10) and includes moving the image acquisition device (10) back to its initial orientation.

Description

Related applications

[0001] This application claims the benefit of priority to U.S. Application No. 14 / 315884, filed June 26, 2014, which is incorporated herein by reference in its entirety. Technical area

[0002] This invention relates to time-lapse photography. Particular aspects of this invention provide apparatus and methods for capturing time-lapse image sequences of celestial bodies. background

[0003] Devices and methods for time-lapse photography are known. A method for automatically tracking and photographing celestial objects is disclosed in EP 2 566 149 A1. The method of automatically tracking and photographing a celestial object includes inputting latitude information at a shooting location, recording azimuth angle information, recording elevation angle information, and inputting information about the orientation of a photographic device and the focal length of a photographic optical system. The method further comprises calculating the amounts of movement of the object relative to the photographic device to fix the image of the celestial object with respect to the predetermined image area of ​​an image capturing device using all of the input information.Furthermore, the method includes obtaining a photographic image by moving at least one of the predetermined image area and the image of the celestial object based on the calculated relative movement amounts.

[0004] An example of an electronic camera is disclosed in US 5 365 269 A. Therein, an optical image of an astronomical scene through a telescope is focused onto a CCD photosensor array to produce successive electronic pixel images of the scene, which are registered and combined to produce an accumulated image substantially free of fringes caused by the Earth's rotation.

[0005] WO 2013 085 399 A1 describes a motion control device for a camera and methods for using the device. The device includes a camera mount and a linear motion assembly connected to a drive mechanism. This configuration causes the drive mechanism and camera mount to move linearly along a line or path. The device is used to record time-delay sequences and allows operation over any desired path length along the line. Furthermore, the device is portable and can be used with other camera accessories.

[0006] Typically, time-lapse photography involves taking a sequence of photographs or images at time-spaced points in time (the time between successive images defining a frame rate) so that the captured images can be displayed at a playback speed faster than the frame rate. For example, a sequence of time-lapse images may be captured at a frame rate of 1 frame / s and played back at a playback speed of 30 frames / s. Using time-lapse photography, changes in an object that occur over relatively long periods of time can be captured and played back at much shorter periods of time, thereby depicting the object's changes over time.

[0007] Celestial bodies (e.g., stars) are difficult to photograph because many are relatively dark. To achieve a satisfactory exposure for a photograph of a celestial body, a relatively long exposure time can be used. However, celestial bodies move relative to Earth, and consequently, photographing celestial bodies with a relatively long exposure time will result in blur.

[0008] There is a general desire for techniques to capture time-lapse image sequences of celestial bodies. Summary

[0009] The following embodiments and their aspects are described and illustrated in connection with devices and methods that are intended to be exemplary and illustrative and not limiting in scope. In various embodiments, one or more of the problems described above have been reduced or eliminated, while other embodiments are directed to other improvements.

[0010] One aspect of the invention provides a method for capturing a time-lapse image sequence. The method comprises capturing a first plurality of photographs. Capturing each photograph of the first plurality of photographs comprises: opening a shutter of an image capturing device; while the shutter of the image capturing device is open, moving the image capturing device so as to reduce the movement of a celestial body or coordinate within the field of view of the image capturing device; closing the shutter of the image capturing device; and moving the image capturing device to a subsequent orientation.

[0011] Another aspect of the invention provides a method for capturing a time-lapse image sequence. The method comprises: providing a motorized mount that is controllably movable, the motorized mount supporting an image capture device; moving the mount to align the image capture device in a home orientation; and repeating, for each of a plurality of photographs comprising the time-lapse image sequence: (a) opening a shutter of the image capture device and, while the shutter is open during an exposure period, moving the mount and the image capture device carried by the mount to compensate for the Earth's rotation; (b) closing the shutter of the image capture device at the end of the exposure period; and (c) moving the mount to align the image capture device in the home orientation before a next photograph.

[0012] Another aspect of the invention provides a method for capturing a time-lapse image sequence. The method comprises: providing a motorized mount that is controllably movable, the motorized mount supporting an image capture device; moving the mount to align the image capture device to an initial orientation; and repeating, for each of a plurality of photographs comprising the time-lapse image sequence: (a) opening a shutter of the image capture device and, while the shutter is open during an exposure period, moving the mount and the image capture device carried by the mount to compensate for the Earth's rotation; (b) closing the shutter of the image capture device at the end of the exposure period; and (c) moving the mount to align the image capture device to a subsequent orientation prior to a next photograph.

[0013] Another aspect of this invention provides a computer program product. The computer program product comprises a non-transitory medium carrying a set of machine-readable instructions that, when executed by a processor of the mount for an imaging device, cause the mount and the imaging device carried by the mount to perform the methods described herein.

[0014] Another aspect of the invention provides a mount for an imaging device comprising a processor configured to cause the mount and the imaging device carried by the mount to perform the methods described herein.

[0015] In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent upon reference to the drawings and upon studying the following description. Short description of the drawings

[0016] Exemplary embodiments are illustrated in the designated figures of the drawings. The embodiments and figures disclosed herein are to be considered as illustrative rather than restrictive. The Fig. 1A and Fig. 1B are, respectively, a perspective view and a schematic representation of a mount for an imaging device and an imaging device carried by the mount for capturing time-lapse image sequences of celestial bodies according to an exemplary embodiment of the invention. Fig. 1C is a schematic diagram of a mount for an imaging device and an imaging device carried by the mount for capturing time-lapse image sequences of celestial bodies according to another exemplary embodiment of the invention. Fig. 2 is a schematic representation of a method for capturing time-lapse image sequences of celestial bodies according to an exemplary embodiment of the invention. Fig. 3 is a schematic representation of a method for capturing “moving perspective” time-lapse image sequences of celestial bodies according to an exemplary embodiment of the invention. Fig. 4 is a schematic representation of a method for capturing “multiple exposure” time-lapse image sequences of celestial bodies according to an exemplary embodiment of the invention. Description

[0017] In the following description, specific details are set forth in order to provide a better understanding to those skilled in the art. However, well-known elements are not shown or described in detail in order to avoid unnecessarily obscuring the disclosure. Accordingly, the description and drawings should be regarded in an illustrative rather than a restrictive sense.

[0018] The Fig. 1A and Fig. 1B are, respectively, a perspective view and a schematic representation of a mount 20 for an image capture device and an image capture device 10 (e.g., a camera) carried by the mount 20 for capturing time-lapse image sequences of celestial bodies according to an exemplary embodiment. The image capture device 10 includes a shutter 12, an optical input system 13, a shutter control input 14, and an image sensor 16. The image capture device 10 may include a camera, another type of device (e.g., a mobile phone, a tablet, a laptop, a telescope, or another type of electronic or optical device) equipped with an image capture device and / or the like. As is known in the art, the image capture device 10 may include numerous other components. For brevity, these components are shown in the Fig. 1A or Fig. 1B and are not described in detail herein.

[0019] The image capture device 10 captures images by collecting light on the image sensor 16. When the shutter 12 is open, the light is directed to the image sensor 16 through the optical input system 13, which typically includes one or more lenses, mirrors, and / or other optical devices. When the shutter 12 is closed, the light cannot reach the image sensor 16. The image sensor 16 is sensitive to light and can form an image when light strikes it. The shutter 12 can be used (at least in part) to control the amount of light reaching the image sensor 16 by adjusting the exposure period or exposure time (i.e., the length of time the shutter 12 remains open to capture a particular image). The image capture device 10 includes a shutter control input 14 that can electronically control the operation of the shutter 12, as explained in detail below.The image capture device 10 may be characterized by an optical axis 15. The optical axis 15 may be an imaginary line along which the light propagates through the optical input system 13 and / or the image capture device 10, and may indicate the orientation of the image capture device 10. The optical axis 15 may traverse the center of curvature of the lenses and / or mirrors in the optical input system 13 of the image capture device 10.

[0020] The mount 20 includes an optional tripod 20A, mounting elements 24 for connecting to and supporting the image capture device 10, one or more motors 21 for adjusting the orientation of the image capture device 10 carried thereon and / or the optical axis 15 of the image capture device 10, a shutter control interface 25 for controlling the shutter 12 of the image capture device 10 via the shutter control input 14, and a controller 22 for controlling the motors 21 and the shutter control interface 25. As described in more detail below, the controller 22 may be configured to cause the mount 20 and the image capture device 10 carried on the mount 20 to acquire time-lapse image sequences of celestial bodies.

[0021] In another in Fig. 1C, an external shutter control device 26 is provided. The external shutter control device 26 may, but need not necessarily, be physically separate from the image capture device 10 and the mount 20. The external shutter control device 26 may comprise a relatively simple shutter control device 26 or part of a comparatively more sophisticated device (e.g., a remote control or a computer-based controller) for controlling the image capture device 10. The external shutter control device 26 may transmit shutter control information (e.g., via a wired or wireless interface) to the shutter control input 14.In some exemplary embodiments, the external shutter control device 26 may be operable to send "shutter open" and "shutter closed" signals to the shutter control input 14, thereby causing the image capture device 10 to open and close the shutter 12. The mount 20 may include a receiver 27 configured to receive shutter control information (e.g., shutter open and shutter closed signals) from the external shutter control device 26 (e.g., via a wired or wireless connection). As explained in more detail below, the controller 22 may be configured to cause the motors 21 to change the orientation of the image capture device 10 based on the shutter control information received from the external shutter control device 26.For example, in some embodiments, when the receiver 27 receives a shutter-open signal, the controller 22 may be configured to cause the motors 21 to change the orientation of the image capture device 10 (e.g., to track a celestial body and / or celestial coordinate, as explained in more detail below); and when the receiver 27 receives a shutter-closed signal, the controller 22 may be configured to cause the motors 21 to move the orientation of the image capture device 10 to its initial orientation or a subsequent orientation (as explained in more detail below).

[0022] The controller 22 can cause the imaging device 10 to capture a plurality of photographs that together form a time-lapse image sequence. For each photograph of the plurality of photographs, the controller 22 can control the shutter 12 of the imaging device 10 (via the shutter control interface 25 and the shutter control input 14) to open for a desired exposure period (e.g., a period of 1 to 180 seconds in some embodiments, or 30 to 120 seconds in some embodiments). For each photograph, while the shutter of the imaging device 10 remains open during the exposure period, the controller 22 can cause the motors 21 of the mount 20 to change the orientation of the imaging device 10 (e.g., to change the orientation of its optical axis 15).More specifically, the controller 22 may cause the mount 20 to move the imaging device 10 such that the orientation of its optical axis 15 compensates for (or counteracts) the rotation of the Earth relative to the celestial sphere.

[0023] Such movement of the image capture device 10 and / or its optical axis 15 to compensate for the Earth's rotation may be referred to as automatic tracking. Performed with sufficient precision, such automatic tracking movement of the image capture device 10 and / or its optical axis 15 may be used to cause a selected celestial body and / or celestial coordinate to remain substantially stationary within the field of view of the image capture device 10—i.e., to cause the optical axis 15 of the image capture device to track a celestial body and / or a corresponding celestial coordinate.When the optical axis 15 of the imaging device 10 is aligned with a specific celestial body, this automatic tracking movement of the imaging device 10 can reduce or eliminate the blurring effect otherwise caused by the movement of the specific celestial body within the field of view of the imaging device 10 during the exposure period. After each photograph has been taken, the controller 22 can cause the motors 21 of the mount 20 to move the imaging device 10 and / or its optical axis 15 back to their original orientation before repeating the process for a subsequent photograph in the time-lapse image sequence. The imaging device 10 can thereby capture multiple photographs, which can be stored and played back as a time-lapse image sequence.

[0024] The controller 22 (and / or components thereof) may typically comprise hardware, software, firmware, or a combination thereof. In the illustrated embodiment, the controller 22 is embodied as an integrated controller including one or more processors and a suitable user interface 28, which may include user input devices, displays, and / or the like (not shown). In some embodiments, the controller 22 may be embodied on a programmed computer system including one or more processors and a user interface, which may include user input devices, displays, and / or the like. Processor(s) embodying the controller 22 may comprise any suitable processor(s), including, but not limited to, microprocessors, digital signal processors, graphics processors, field programmable logic arrays, and / or the like.The components of controller 22 may be combined or subdivided, and the components of controller 22 may include subcomponents shared with other components of controller 22. The components of controller 22 may be physically separated from each other. In some embodiments, controller 22 is not necessarily part of mount 20, and mount 20 may be controlled by a remote control or the like.

[0025] As discussed above, the motors 21 may be connected (or otherwise operable) to change the orientation of the imaging device 10 and / or its optical axis 15. In some embodiments, the motors 21 may be connected (or otherwise operable) to pivot the imaging device 10 and / or its optical axis about one or more axes. The controller 22 may be configured to control the movement of the motors 21 and, in turn, the movement of the imaging device 10 carried on the mount 20 and / or its optical axis 15. For example, the controller 22 may utilize feedback (e.g., from suitable sensor(s) (not shown) such as encoders and / or the like) to control the movement of the motors 21. Further, or alternatively, the motors 21 may comprise stepper motors, which may be controlled without feedback sensors.Motor control circuits, their components, and their operation are generally known to those skilled in the art. For the sake of brevity, the details of these motor control circuits will not be described further herein.

[0026] In some embodiments, the mount 20 comprises an altitude-azimuth (or Altaz) mount 20. The motors 21 of an Altaz mount 20 are connected, and the mount 20 is otherwise configured or configurable to pivot the imaging device 10 and / or its optical axis 15 about a first azimuthal (or vertical) axis parallel to the direction of Earth's gravity (i.e., extending between the Earth's center and the zenith) and a second altitude (or horizontal) axis parallel to the horizon and orthogonal to the azimuthal axis. Desirably, the Altaz mount 20 is calibrated so that its altitude and azimuthal axes are correctly aligned.The controller 22 may be configured to cause the motors 21 of the Altaz mount 20 to move the image pickup device 10 and / or its optical axis 15 about both the altitude axis and the azimuthal axis, thereby effecting the automatic tracking movement discussed above.

[0027] In some embodiments, the mount 20 comprises an equatorial mount 20. The motor(s) 21 of an equatorial mount 20 are connected, and the mount 20 is otherwise configured or configurable to pivot the imaging device 10 and / or its optical axis 15 about a first polar (or right ascension) axis parallel to the Earth's rotation axis and a second declination axis orthogonal to the polar axis. Desirably, the equatorial mount 20 is calibrated such that its polar and declination axes are correctly aligned. This may be referred to as polar alignment. Upon such calibration of the mount 20, the controller 22 may be configured to control the one or more motors 21 (e.g.,Right ascension motor) of the equatorial mount 20 to effect the automatic tracking movement by moving the image pickup device 10 and / or its optical axis 15 only about the right ascension axis.

[0028] In the illustrated embodiment, the mount 20 includes a user interface 28 (e.g., a graphical, menu-driven, and / or textual user interface). The user interface 28 need not be implemented solely on the mount 20. In some embodiments, the user input 28 includes a wireless or wired interface for transmitting data to and from an external device (e.g., a laptop, a smartphone, a tablet, and / or the like), and the external device may provide a suitable user interface. The user interface 28 may be used to transmit a variety of information and / or commands to the mount 20 and / or from the mount 20 to the user interacting with the user interface 28. By way of non-limiting example, such information includes: • an initial orientation of the image capture device 10 and / or its optical axis 15. This initial orientation may be provided, for example, by specifying a particular celestial body (e.g., a star, etc.) or a particular celestial coordinate. Furthermore, or alternatively, this information may be provided by manipulating the mount 20 (e.g., using the appropriate buttons (not shown) on the user interface 28) such that the particular celestial body or the particular celestial coordinate is located in the center of the field of view, and then indicating (e.g., pressing another appropriate button on the user interface 28) that the current location should be the initial orientation; • the location of the mount 20 on the Earth's surface, dates, and time. In some embodiments, the mount 20 may obtain this information directly from a global positioning system unit, a calendar, and a clock; • a specific celestial body or celestial coordinate to be tracked; • Image data obtained from the image pickup device 10; • the exposure time for a “long exposure” photograph (see explanation below); • the exposure time for a ‘short-exposure’ photograph (see explanation below); • the number of photographs to be taken in a time-lapse sequence; • the length of time to wait between photographs; • the exposure time for each photograph; • the final alignment of the image pickup device 10 (in the case of a moving perspective time-lapse image sequence); • the trajectory of movement of the image pickup device 10 between the initial orientation and the final orientation (in the case of a moving perspective time-lapse photography); • Data, operating instructions and / or the like that may be stored in the data memory 29; and / or • the like.

[0029] The mount 20 may include a data storage 29. The data storage 29 may include machine-executable instructions and / or data. The controller 22 may be configured to locate and execute the machine-executable instructions and to transmit and / or read data to the data storage 29.

[0030] The data memory 29 may contain or be programmed to contain a variety of machine-executable instructions and / or data, including, but not limited to: • Formulas and / or algorithms for converting between different types of coordinate systems; • the celestial coordinates of various celestial bodies; • machine-executable instructions for controlling the motors 21 to change the orientation of the image pickup device 10 (e.g., so that it tracks a specific celestial body or a specific celestial coordinate); • machine-executable instructions for using the shutter control interface 25 to control the shutter 12 of the image capture device 10 via the shutter control input 14; and / or • include the like.

[0031] Fig. 2 is a schematic representation of a method 100 for capturing a time-lapse image sequence according to a particular embodiment. The method 100 may be performed at least in part by the controller 22, which may utilize the mount 20 and the imaging device 10 carried by the mount 20 to effect the method 100. To explain the method 100, this description assumes that the mount 20 and the imaging device 10 are appropriately calibrated for automatic tracking, as is known in the art.

[0032] The method 100 begins in optional segment 105, which includes obtaining one or more parameters associated with the time-lapse image sequence to be generated. These parameters may be entered by a user, for example, via the user interface 28. These parameters may include, but are not limited to: the exposure period for each photograph in the time-lapse image sequence; the interval between consecutive photographs (i.e., the image acquisition time) in the time-lapse image sequence; the total duration of the time-lapse image sequence; the number of photographs in the time-lapse image sequence; the output orientation for each photograph in the time-lapse image sequence, and / or the like. Segment 105 is not required. In some cases, one or more default parameters may be used, in which case the default parameters are used instead of the user-entered parameters.In some embodiments, as discussed in detail below, the initial orientation may be obtained for each photograph in segment 110.

[0033] The method 100 then proceeds to segment 110, which includes moving the image capture device 10 and / or its optical axis 15 to a home orientation. Segment 110 may include moving the image capture device 10 to its home orientation using the motors 21. In some embodiments, segment 110 may be performed in part by a user. For example, as part of segment 110, a user may interact with the user interface 28 to cause the motors 21 to move the image capture device 10 to a home orientation and may then interact with the user interface 28 to establish the current location as the home orientation.In some embodiments, segment 110 may be executed by the controller 22, which utilizes the motors 21 to controllably move the image capture device 10 to an initial orientation, where the initial orientation may be obtained by the controller 22 from a user (via the user interface 28) as part of segment 110 or as one of the parameters of segment 115. In some embodiments, the initial orientation of segment 110 may be specified with respect to a celestial body, a particular set of celestial coordinates (e.g., the celestial coordinates of a celestial body), and / or the like. For example, the mount 20 may comprise a so-called go-to mount 20, in which a user may select a celestial body or celestial coordinate (e.g.,via the user interface 28), and the mount 20 can controllably move the imaging device 10 such that its optical axis 15 is oriented toward the selected celestial body or celestial coordinate, and / or such that the selected celestial body or celestial coordinate is located within the field of view of the imaging device 10 (e.g., typically centered).

[0034] The method 100 then proceeds to segment 120, which includes opening the shutter 12 of the imaging device 10. The mount 20 may cause the shutter 12 of the imaging device 10 to open by sending appropriate commands and / or signals to the shutter control input 14 via the shutter control interface 25. Segment 120 includes maintaining the shutter 12 in its open configuration for an exposure period. As discussed above, the exposure period may be one of the time-lapse parameters of segment 105. In some embodiments, the shutter 12 remains open until the shutter control input 14 has received the appropriate commands and / or signals.In some embodiments, the commands and / or signals provided from the shutter control input 14 via the shutter control interface 25 are tilt commands that tilt the shutter 12 between an open and / or closed configuration. In some embodiments, a user can condition the imaging device 10 (e.g., a controller (not shown) of the imaging device 10) with an exposure period via a suitable user interface (not shown) on the imaging device 10. In some embodiments, the mount 20 can communicate the exposure period to the imaging device 10 via the shutter control interface 25 and the shutter control input 14.Once the imaging device 10 is provided with the exposure period, the mount 20 can send only a single command / signal (or a single sequence of commands / signals) to the imaging device 10 (via the shutter control interface 25 and the shutter control input 14), causing the imaging device 10 to open its shutter 12 for the desired exposure period. This is not required. In some embodiments, the mount 20 (e.g., the controller 22) controls the exposure period independently of the imaging device 10 by sending appropriate signals and / or commands (via the shutter control interface 25 and the shutter control input 14) to open the shutter 12 and subsequently close the shutter 12 (see segment 130 below).The control 22 of the mount 20 can use the exposure period to determine how long the selected celestial body or coordinate should be tracked (see below).

[0035] Also in segment 120, while the shutter 12 is open, the controller 22 causes the motors 21 of the mount 20 to controllably and automatically move the image capture device 10 and / or its optical axis 15 (e.g., change its orientation)—for example, to track a celestial body or celestial coordinate such that the celestial body or celestial coordinate remains substantially stationary within the field of view of the image capture device 10. The celestial body or celestial coordinate to be automatically tracked while the shutter 12 is open in segment 120 may be selected by the user via the user input 28 (e.g., as part of the segments 105 or 110 discussed above).The celestial body or celestial coordinate to be automatically tracked while the shutter 12 is open in segment 120 may be the celestial body or celestial coordinate located at the center of the field of view (or at another position in the field of view) of the image capture device 10 when the image capture device 10 is in its initial orientation of segment 110.

[0036] In some embodiments, the automatic tracking movement effected by mount 20 while shutter 12 is open in segment 120 does not keep the celestial body or celestial coordinate completely stationary within the field of view of imaging device 10, but rather reduces the movement of the celestial body or celestial coordinate within the field of view of imaging device 10 or minimizes the movement of the celestial body or celestial coordinate within the field of view of imaging device 10 to an acceptable level. This "imperfect" automatic tracking may reduce the blurring effect caused by the movement of the celestial body within the field of view of imaging device 10 while shutter 12 remains open to an acceptable level, but may not completely eliminate it.

[0037] To effect the movement of segment 120, mount 20 may cause image capture device 10 and / or its optical axis 15 to controllably pivot about one or more axes. In some embodiments, mount 20 may pivot image capture device 10 and / or its optical axis 15 about only one axis while shutter 12 is open in segment 120. For example, if mount 20 is an equatorial mount, the automatic tracking movement of segment 120 may be effected by controller 22 causing motors 21 to pivot image capture device 10 and / or its optical axis 15 about only the polar (e.g., right ascension) axis. In some embodiments, mount 20 may pivot image capture device 10 and / or its optical axis 15 about multiple axes while shutter 12 is open in segment 120.For example, if mount 20 is an Altaz mount, the automatic tracking movement of segment 120 may be effected by controller 22, which causes motors 21 to pivot image acquisition device 10 and / or its optical axis 15 about the elevation axis and the azimuthal axis. In some embodiments where mount 20 is an Altaz mount, a mechanical / optical field derotator may be used to correct the field rotation that occurs with Altaz mounts. In some embodiments where mount 20 is an Altaz mount, field derotation software may be used to correct the field rotation.

[0038] In some embodiments and / or situations (e.g., where the motion of a particular celestial body (e.g., a planet) exhibits a different motion than diurnal periodic motion), the controller 22 may determine (e.g., calculate or search) how the motors 21 should move the imaging device 10 and / or its optical axis 15 in segment 120 to keep the celestial body or celestial coordinate substantially stationary within the field of view of the imaging device 10. The controller 22 may access information regarding the trajectories of various celestial bodies and / or coordinates from a data store (e.g., the data store 29), which in turn receives this information via the user interface 28.

[0039] In some embodiments and / or situations, the controller 22 causes the mount 20 and the imaging device 10 carried thereon to track the celestial body in “real time” by monitoring the captured image data so that the location of a celestial body within the field of view of the imaging device 10 (e.g., in the captured image data) and the orientation of the imaging device 10 can be adjusted so that the celestial body remains approximately stationary within the field of view of the imaging device 10.

[0040] At the end of the exposure period, the method 100 transitions from segment 120 to segment 130, which includes closing the shutter 12 of the imaging device 10. As discussed above, in some embodiments, the imaging device 10 automatically closes the shutter 12 after a configurable exposure period. For example, the imaging device 10 may be configured to close the shutter 12 after a user-configurable exposure period using a suitable user interface (not shown), or the imaging device 10 may be configured by the mount 20 (via the shutter control interface 25 and the shutter control input 14) to close the shutter 12 after a user-configurable exposure period.In some embodiments, the mount 20 controls the exposure period independently of the image capture device 10 and transmits appropriate signals and / or commands to close the shutter 12 in segment 130 via the shutter control interface 25 and the shutter control input 14. Likewise, in segment 130, the mount 20 stops tracking the celestial body or celestial coordinate.

[0041] In specific embodiments, tracking of the celestial body or celestial coordinate in segment 120 may occur for at least 25%, 50%, 75%, 95%, 99%, or 100% of the time during which the shutter 12 remains open in segment 120. In some embodiments, tracking begins shortly before the shutter 12 opens in segment 120 and ends shortly after the shutter 12 closes in segment 130.

[0042] In some embodiments, the shutter 12 may remain open for 1, 5, 10, 30, 60, 120, or 180 seconds.

[0043] After the shutter 12 closes in segment 130, the method 100 proceeds to segment 140, which includes evaluating exit-loop criteria to determine whether the current photograph is the last photograph in the time-lapse image sequence. For example, the exit-loop criteria of segment 140 may include, without limitation, evaluating whether a desired number of photographs have been taken for the time-lapse image sequence, whether a desired total duration of the time-lapse image sequence has been reached, and / or the like. The exit-loop criteria of segment 140 may be embodied as one of the time-lapse parameters of segment 105. If the request of segment 140 determines that the time-lapse image sequence should end (yes branch of segment 140), the method 100 ends in segment 145.

[0044] If, on the other hand, the request of segment 140 determines that another photograph should be taken (No branch from segment 140), then the method 100 proceeds to segment 150, in which the mount 20 moves the image capture device 10 and / or its optical axis 15 back to the initial orientation of segment 110 (e.g., the controller 22 causes the motors 21 to move the image capture device 10 back to the initial configuration of segment 110). From segment 150, the method 100 proceeds to the optional segment 160, in which the image capture device 10 and the mount 20 wait for the start of the next image acquisition time before proceeding to segment 120 and repeating the image acquisition process. It is understood that the image acquisition time (i.e.,The time between the start of successive photographs in a time-lapse image sequence is not the same as the exposure period (the time during which the shutter 12 is open during a particular photograph). Typically, the image acquisition time is longer than the exposure period. In some embodiments, the image acquisition time may be, for example, 15, 30, 60, 120, or 300 seconds. After waiting segment 160, the method 100 proceeds to segment 120 and repeats the image acquisition process by opening the shutter 12 and causing the image capture device 10 to move, as discussed above.

[0045] In some embodiments, the order of two or more segments 140, 150 and 160 may be reversed.

[0046] As discussed above, in a typical application of method 100, the image acquisition process of segments 120 and 130 may be repeated N times to capture a corresponding number N of photographs and form a time-lapse image sequence comprising N images. The number N may be a time-lapse parameter of segment 105. The number N may also be derived from other parameters (e.g., time-lapse parameters other than those of segment 105), such as the total time of the time-lapse image sequence divided by the image acquisition time. In some embodiments, N may be 50, 100, 300, 500, 1000, or 5000. The capture of these N photographs in method 100 may be stored (e.g., in data storage 29) and played back as a time-lapse image sequence.

[0047] Fig. 3 is a schematic illustration of a method 200 for capturing a "moving perspective" time-lapse image sequence according to a particular embodiment. The method 200 may be performed at least in part by the controller 22, which may utilize the mount 20 and the image capture device 10 carried by the mount 20 to effect the method 200. In method 200, the procedures involved in segments 210, 220, 230, 240, 245, and 260 may be analogous to, or substantially similar to, the procedures of segments 110, 120, 130, 140, 145, and 160, respectively, of method 100.Optional step 205 may differ from step 105 in that optional step 205 may include providing a moving perspective trajectory or path that may include or otherwise define numerous orientations for image capture device 10 and / or its optical axis 15.

[0048] Segment 240 of method 200 differs from segment 140 of method 100 in that in segment 240, the image capture device 10 is moved to a next or subsequent orientation along a perspective path. In some embodiments, the initial orientation of segment 210 and a group of one or more subsequent orientations of segment 250 of the image capture device 10 and / or its optical axis 15 may define or identify a perspective path. In other embodiments, the perspective path may define the initial orientation of segment 210 and the group of one or more subsequent orientations of segment 250. The perspective path and / or the orientations of segments 210, 250 may be selected by the user via user input 28 (e.g., as part of the time-lapse parameters of segment 205, as discussed above).The perspective path may be the shortest path between the initial orientation and the final orientation (e.g., a "straight-line" path) or a shaped path between the initial orientation and the final orientation (e.g., a "curved" path following a sinusoidal, parabolic, or polynomial path; a "piecewise linear" path; and / or the like). The orientations of the segments 210, 250 may be equally spaced along the perspective path.

[0049] Fig. 4 is a schematic representation of a method 300 for capturing a "multiple exposure" time-lapse image sequence according to a particular embodiment. The method 300 may be performed at least in part by the controller 22, which may utilize the mount 20 and the image capture device 10 carried by the mount 20 to effect the method 300. In method 300, the procedures involved in segments 310, 320, 330, 340, 345, 350, and 360 may be analogous to, or substantially similar to, the procedures of segments 110, 120, 130, 140, 145, 150, and 160, respectively, of method 100. Optional step 305 may differ from step 105 in that optional step 305 may include providing a short exposure period for a short exposure photograph that may be used in segment 315, as explained in detail below.

[0050] Occasionally, not all objects in the field of view of the image capture device 10 will move in the same trajectory. For example, the field of view of the image capture device 10 may include, without limitation: stars that move in a first (diurnal) trajectory relative to the image capture device 10; a planet (or comet) that moves in a second (non-diurnal) trajectory relative to the image capture device 10; and a mountain (that does not move relative to the image capture device 10). Method 300 may attempt to compensate for this effect.

[0051] In segment 315, a short-exposure photograph is taken. In some embodiments, the controller 22 may cause the image capture device 10 to take a short-exposure photograph in segment 315 simply by opening and closing the shutter 12 using the appropriate signals and / or commands transmitted via the shutter control interface 25 and the shutter control input 14. The short-exposure photograph may have a short exposure period that is shorter than the exposure period of the photographs taken in segments 320-330 ("long-exposure photographs"). In some embodiments, the user may configure the short exposure period of segment 315 as part of segment 305, as discussed above. In some embodiments, the user may configure the short exposure period via a user interface (not shown) of the image capture device 10.In some embodiments, the user may configure the short exposure period via user input 28 of mount 20. In some embodiments, multiple different short exposure periods may be used in correspondingly multiple iterations of segment 315. In some embodiments, the short exposure photograph may have a short exposure period that is 1 / 1000, 1 / 500, 1 / 250, 1 / 125, 1 / 60, 1 / 30, 1 / 15, 1 / 8, 1 / 4, 1 / 2, or 1 second.

[0052] In the illustrated embodiment of Fig. 4, the short-exposure photograph of segment 315 is taken in each iteration of the loop of method 300 (e.g., in each iteration of segments 315-360). As mentioned above, the short-exposure photographs of segment 315 may not all have the same short exposure periods. In some embodiments, the imaging device 10 or mount 20 includes a light meter (not shown) or otherwise receives data from a light meter, and the short exposure period of each short-exposure photograph of segment 315 is selected based on a reading of the light meter.

[0053] In some optional embodiments (in Fig. 4 with the dotted line), the short-exposure photograph of segment 315 need not be taken in every loop of method 300. For example, in some embodiments, only a single short-exposure photograph of segment 315 is taken in a first iteration of the loop of method 300, after which method 300 loops to segment 320. In some embodiments, the short-exposure photographs of segment 315 may be taken once for every multiple (e.g., once for every 2 or 3) iterations of the loop of method 300.

[0054] Each of the long-exposure photographs from segment 320 can be combined with a corresponding short-exposure photograph from segment 315 to create a corresponding composite photograph. As discussed above, there can be a one-to-one correspondence between long-exposure photographs and short-exposure photographs, or multiple long-exposure photographs can be combined with a corresponding short-exposure photograph in a multiple-to-one correspondence. The multiple composite photographs can then form the time-lapse image sequence generated by method 300 and can be stored or played back as a multiple-exposure time-lapse image sequence.

[0055] Each pair of long-exposure and short-exposure photographs can be combined in any suitable manner. For example, photo editing software can be used to create a composite photograph that includes the long-exposure image of the stars and the short-exposure image of the planet and the mountain. In some embodiments, the photo editing software can be used to create a composite photograph that includes the long-exposure image of celestial bodies (e.g., stars, etc.) and the short-exposure image of terrestrial objects (e.g., landscapes, trees, mountains, oceans, etc.).

[0056] The invention may also be provided in the form of a program product. The program product may comprise any medium carrying a series of computer-executable signals comprising instructions which, when executed by a mount (e.g., mount 20), cause the mount to perform a method of the invention. The program products according to the invention may be in a wide variety of forms. The program product may, for example, comprise physical (non-volatile) media such as magnetic data carriers including floppy disks, hard disk drives, optical data carriers including CD-ROMs, DVDs, electronic data carriers including ROMs, Flash RAM, or the like. The instructions may be present on the program product in encrypted and / or compressed formats.

[0057] When reference is made above to a component (e.g., a controller, a microprocessor, etc.), unless otherwise stated, reference to that component (including reference to a "tool") should be construed to include, as equivalents of that component, any component that performs the function of the described component (i.e., is functionally equivalent), including components that are not structurally equivalent to the disclosed structure that performs the function in the illustrated exemplary embodiments of the invention.

[0058] While numerous exemplary aspects and embodiments have been discussed herein, those skilled in the art will recognize certain modifications, permutations, additions, and subcombinations thereof. For example: • The apparatus and methods described herein are not limited to time-lapse image sequences of celestial bodies; non-celestial bodies can also be tracked. • In some embodiments, the shutter control interface 25 of the mount 20 may be Fig. 1B may include a shutter actuator that can physically actuate the shutter 12 of the image capture device 10. Other than physically actuating the shutter 12, such a shutter actuator may function similarly to the shutter control interface 25 described herein. • In the above-described embodiment of Fig.1C, the receiver 27 is described as receiving shutter control information from an external shutter control device 26. In some embodiments, the receiver 27 may receive similar information from the image capture device 10 regarding when the shutter 12 opens and / or closes. For example, the shutter control input 14 of the image capture device 10 and the receiver 27 may include two-way communication interfaces for transmitting such information.

[0059] It is therefore intended that the following appended claims and the claims introduced below be construed to embrace all such modifications, rearrangements, additions, and subcombinations as being within their true spirit and scope.

Claims

[1] A method for capturing a time-lapse image sequence, the method comprising: moving an image pickup device (10) to an initial orientation prior to taking a first plurality of photographs; and comprising taking a first plurality of photographs, wherein taking each photograph of the first plurality of photographs: opening a shutter (12) of an image recording device (10); while the shutter (12) of the image pickup device (10) is open, moving the image pickup device (10) to reduce the movement of a celestial body or a celestial coordinate in the field of view of the image pickup device (10); closing the shutter (12) of the image recording device (10) and moving the image pickup device (10) back to the initial orientation. [2] The method of claim 1, wherein moving the image capturing device (10) to reduce the movement of the celestial body or celestial coordinate in the field of view of the image capturing device (10) comprises moving the image capturing device (10) to keep the celestial body or coordinate substantially stationary in the field of view of the image capturing device (10). [3] The method of claim 1, wherein moving the image pickup device (10) to reduce the movement of the celestial body or celestial coordinate in the field of view of the image pickup device (10) comprises changing the orientation of an optical axis (15) of the image pickup device (10) to track the relative movement between the Earth and the celestial body or celestial coordinate. [4] The method of claim 1, wherein moving the image pickup device (10) to reduce the movement of the celestial body or celestial coordinate in the field of view of the image pickup device (10) comprises changing the orientation of an optical axis (15) of the image pickup device (10) to track the relative movement between the Earth and the celestial sphere. [5] The method of claim 1, wherein moving the image pickup device (10) to reduce the movement of the celestial body or celestial coordinate in the field of view of the image pickup device (10) comprises changing the orientation of an optical axis (15) of the image pickup device (10) to automatically track the celestial body or celestial coordinate. [6] The method of claim 1, wherein the subsequent orientations of the first plurality of photographs are on a perspective path from an initial orientation to a final orientation. [7] The method of claim 6, wherein the subsequent orientations of the first plurality of photographs define the perspective path from the initial orientation to the final orientation. [8] The method of claim 6, wherein the perspective path comprises a rectilinear path. [9] The method of claim 6, wherein the perspective path comprises a curved path. [10] The method of claim 1, comprising taking a short-exposure photograph, the short-exposure photograph having a shorter exposure period than the exposure period of at least one photograph of the first plurality of photographs. [11] A method according to claim 10, comprising keeping the image recording device (10) stationary during the taking of the short-exposure photograph. [12] A method according to claim 10, comprising selecting the exposure period for the short-time exposure photography based on the reading of a light meter. [13] The method of claim 10, comprising combining the short exposure photograph with at least one photograph of the first plurality of photographs to provide at least one composite photograph. [14] The method of claim 13, wherein combining the short-exposure photograph with the at least one photograph of the first plurality of photographs comprises combining an image of a terrestrial object from the short-exposure photograph with an image of a celestial body from the at least one photograph of the first plurality of photographs. [15] The method of claim 1, comprising taking a second plurality of photographs corresponding to the first plurality of photographs, wherein: each photograph of the second plurality of photographs is taken immediately before or after its corresponding photograph of the first plurality of photographs; each photograph of the second plurality of photographs has an exposure period that is shorter than the exposure period of its corresponding photograph of the first plurality of photographs. [16] The method of claim 15, comprising combining each photograph of the second plurality of photographs with its corresponding photograph of the first plurality of photographs to provide a third plurality of composite photographs. [17] The method of claim 1, wherein taking each photograph of the first plurality of photographs comprises waiting for an image capture time to elapse before taking a subsequent one of the first plurality of photographs. [18] The method of claim 17, wherein waiting for the image capture time to elapse before taking the subsequent one of the first plurality of photographs comprises waiting at least 5 seconds. [19] A computer program product comprising a non-transitory medium carrying a series of machine-readable instructions which, when executed by a processor of a mount (20) for an image capture device (10), cause the mount (20) and the image capture device (10) carried by the mount (20) to carry out the method of claim 1. [20] Mount (20) for an image pickup device (10), comprising a processor configured to cause the mount (20) and the image pickup device (10) carried by the mount (20) to perform the method of claim 1. [21] A method for recording a time-lapse image sequence, the method comprising: providing a motorized mount (20) which is controllably movable, the motorized mount (20) carrying an image pickup device (10); moving the mount (20) to align the image pickup device (10) in an initial orientation; repeating for each of a multitude of photographs that make up the time-lapse sequence: opening a shutter (12) of the image pickup device (10) and, while the shutter (12) is open during the exposure period, moving the mount (20) and the image pickup device (10) carried by the mount (20) to compensate for the Earth's rotation; closing the shutter (12) of the image recording device (10) at the end of the exposure period; and moving the mount (20) to align the image pickup device (10) to the initial orientation before a next photograph.

Images