The present invention relates to a device for providing tilt and shift of lenses for cameras, cameras having tilt and shift capability for lenses and image sensors and also to a method of performing correction of digital images.
In several situations a photographer needs to take pictures of objects having planes that are not directly in the plane of focus, meaning that the subject plane is not correctly orientated in the image plane. This could for instance be a photograph of a pizza taken in perspective, an aerial photo of a landscape or a high building. These images may suffer from distortion, e.g. in an image of a high building the sides of the building may seem to converge at the top.
One solution to this is based on the so-called Scheimpflug principle. This may involve tilting, shifting and rotation of the lens relative to the image plane.
The above principle has been implemented in view cameras. A view camera comprises a flexible bellows which forms a light-tight seal between two adjustable standards one of which holds a lens, and the other a viewfinder or a photographic film holder. The bellows is a flexible, accordion-pleated box, which encloses the space between the lens and film, and has the ability to flex to accommodate the movements of the standards. The front standard is a board at the front of the camera which holds the lens and, usually, a shutter. At the other end of the bellows, the rear standard is a frame which holds a ground glass, used for focusing and composing the image before exposure, which is replaced by a holder containing the light-sensitive film, plate, or image sensor for exposure. The front and rear standards can move in various ways relative to each other, unlike most other types of camera, giving control over focus, depth of field and perspective.
The photographer taking the picture then positions the camera and manipulates the front end to obtain a focus plane that coincides with the object plane of the object to be photographed. Especially when using this sort of technique in combination with a digital camera there is a need for knowing the position of the lens relative to the image plane in the camera so that the image may be compensated correctly.
This may be achieved by a device according to an aspect of the present invention wherein the device may comprise a frame having a first part defining a first plane and a second part defining a second plane, the first part configured to be mounted to a camera body and the second part configured to be mounted to a lens, the second part being movable relative to the first part, and a sensor configured to transmit a sensor signal to a processor, the position of the second plane relative to the first plane being determined based on the sensor signal, the processor being configured to calculate an image correction parameter based on the position information, the image correction parameter being used for correcting optical errors in a recorded image due to the position of the lens relative to the image plane, the optical errors including vignetting, distortion, aberration or a combination thereof.
The device may be used as an adaptor allowing a lens to be tilted, shifted and/or rotated relative to a camera housing.
Further more, an aspect of the present invention relates to a digital camera including a digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens mount for receiving a lens, the lens configured to be movable relative to the housing, and a sensor configured transmit a sensor signal transmit a sensor signal to a processor, the position of the lens relative to the housing being determined based on the sensor signal, the processor being configured to calculate an image correction parameter based on the position information, the image correction parameter being used for correcting optical errors in a recorded image due to the position of the lens relative to the image plane, the optical errors including vignetting, distortion, aberration or a combination thereof.
An aspect of the present invention relates to a digital camera including a digital image sensor in a camera housing, the digital image sensor being movably mounted in the camera housing, an image plane defined in the housing by the digital image sensor, the digital camera further comprising a lens mount for receiving a lens, the lens mount fixing the lens to the camera housing, and a sensor configured transmit a sensor signal transmit a sensor signal to a processor, the position of the digital image sensor relative to the housing being determined based on the sensor signal, the processor being configured to calculate an image correction parameter based on the position information, the image correction parameter being used for correcting optical errors in a recorded image due to the position of the lens relative to the image plane, the optical errors including vignetting, distortion, aberration or a combination thereof.
An aspect of the present invention relates to a digital camera including a digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens mount for receiving a lens, the lens configured to be movable relative to the housing, and a sensor configured transmit a sensor signal to a processor, the position of the lens relative to the housing being determined based on the sensor signal, a correction parameter calculated based on the sensor signal, the correction parameter being used for correcting focal settings while the lens is moved relative to the image plane.
An aspect of the present invention relates to a method of performing correction of digital images comprising the steps of obtaining a digital image using a digital camera having digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens, the lens configured to be movable relative to the housing, and a sensor configured to detect the position of the lens relative to the housing, the sensor configured to transmit position information in electronic form to a processor, and performing image correction using position data from the sensor.
The present invention will now be discussed in more detail with reference to the appended figures in which:
The basic Scheimpflug principle utilized in the present invention is explained using a view-camera type. The present invention may also be utilized in cameras of other types.
The view camera 10 also comprises a front end 14 holding a lens 16. The front 14 and rear 12 standards may move in various ways relative to each other, unlike most other types of camera, giving control over focus, depth of field and perspective.
A bellows 18 forms a light-tight seal between the two ends 12 and 14. The bellows 18 is a flexible, accordion-like pleated box and has the ability to flex to accommodate the movements of the two standards 12 and 14.
The view camera 10 is attached to or mounted on a support 20. The support is usually in the form of a tripod.
As indicated by the arrows at 22 the front standard 14 is able to be moved in all directions. The front end or standard 14 is moved relative to the rear standard or end 12.
For detecting and/or registering the position of the front end 14 relative to the rear end 12 a sensor is provided, not illustrated here. The sensor provides an electrical signal representing the position of the front end 14 relative to the rear end 12.
The axis of the lens 16 is normally perpendicular to the plane of the film in the rear standard 12. Changing the angle between axis and film by tilting the lens 16 standard 14 backwards or forwards is called lens tilt or simply tilt. Tilt is especially useful in landscape photography. By using the Scheimpflug principle, the plane of focus may be changed so that any plane can be brought into focus. When the film plane and lens plane are parallel, as is the case for most 35 mm cameras, the plane of focus will also be parallel to these two planes. If, however, the lens plane is tilted with respect to the film plane, the plane of sharp focus will also be tilted according to geometrical and optical properties. This is illustrated and explained with reference to
Altering the angle of the lens standard 14 in relation to the rear standard 12 plane by swiveling it from side to side is called swing. Swing is similar to tilt, but in the horizontal axis. Swing may be used to achieve sharp focus along the entire length of a picket fence, for example
Shift is a very important movement especially in architectural photography.
Generally, the lens is moved vertically, i.e. either up or down, along the plane parallel to the rear end 12 in order to change the portion of the image that will be captured on the film or image sensor.
The main effect of vertical shift is to eliminate converging parallels when photographing tall buildings. If a camera without movements is pointed at a tall building, the top will be cut off; if the camera is tilted upwards to get it all in, the film plane will not be parallel to the building, and the building will seem narrower at the top than the bottom; lines which are parallel in the object will converge in the image. To avoid this apparent distortion, a wide-angle lens will get more of the building in, but will include more of the foreground and alter the perspective. A camera with vertical shift front allows a lens to be raised to include the top of the building without tilting the camera.
The object 40 is in focus. The object 40 is imaged onto the image plane 46 as illustrated by the line 44. This allows an object to be in focus over a distance that is not parallel to the image plane 46. The point 48 is called the Scheimpflug intersection point.
The adaptor 56 comprises two parts 62 and 64. At the part 62 the lens mount 58 is positioned. At the part 64 the lens mount 60 is positioned. The part 64 is movable relative to the part 62. When the adaptor 56 is mounted on a camera body the part 62, and the lens mount 58 is parallel to the image plane in the camera body. A lens mounted at the lens mounting 60 may then be moved relative to the camera body via the adaptor 56 thereby providing tilt and shift functionality.
The adaptor 56 further comprises a magnifying device, not seen here, for enlarging or magnifying the light spot from a lens. When a lens is moved, i.e. tilted and/or shifted, the light coming from the lens hits or intersects an image recording medium differently from when the lens is positioned without tilt and/or shift. Therefore the light spot from the lens is enlarged. Images could be recorded without the enlargement, but it is advantageous that the spot is enlarged, as it is contemplated to provide better images compared to adaptors not having an enlargement device. The enlargement or magnifying device may also be a separate component coupled to the adaptor. In the embodiment shown in
The adaptor 56 comprises a first knob or wheel 66. The wheel 66 allows a photographer to shift the part 64 of the adaptor 56 upwards relative to the part 62. When the wheel 66 is turned a toothed wheel engages a rack or cog railway 68. The rack or cog railway 68 is straight as illustrated. This provides shift in directions parallel to the image plane of a camera that the adaptor 56 is connected to or mounted on.
The adaptor 56 comprises a second knob or wheel 70. The wheel 70 allows a photographer to tilt the part 64 of the adaptor 56 relative to the part 62. When the wheel 70 is turned a toothed wheel engages a rack or cog railway 72. The rack or cog railway 72 is curved as illustrated. This provides tilt relative to the image plane of a camera that the adaptor 56 is connected to or mounted on.
The adaptor 56 comprises a visual indicator 74. The visual indicator 74 provides an indication to a photographer how much and in which direction the adaptor 56 is shifted. The visual indicator 74 comprises a scale 76 and a protruding part 78 used to visually indicate a position on the scale 76.
Also seen in
The three directions of movement, i.e. tilt, shift and rotation, may be combined by a photographer to achieve a desired positioning of the object plane.
In an advantageous embodiment of the present invention the photographer sets a desired focus and then manipulates the lens using the adaptor or camera according to the present invention. The adaptor includes sensors for registering the position of the adaptor, and thus also the lens. When the photographer has set a desired focus he or she may operate the camera to maintain that focus. The camera then registers the focus setting of the lens and the position of the lens relative to the camera. After the photographer changes the orientation of the lens, the camera may then calculate how to set the focus to maintain the same focus point as before.
In
One reason to be interested in knowing the position of a lens relative to an image plane in a camera is that in digital cameras pixel vignetting may be a problem. Pixel vignetting is caused by angle-dependence of the digital sensors, i.e. CMOS or CCD sensor. Light incident on the sensor at a right angle produces a stronger signal than light hitting it at an oblique angle. The image recorded by the sensor may also be affected by light of different wavelength hitting the sensor in oblique angles. The sensors are usually designed to be lighted by a lens optical axis perpendicular to the plane of the sensor, i.e. the image plane of the camera. The angle-dependence of the digital sensor is not the same for every frequency. Surprisingly it has been found that the information from the sensor may improve and/or speed up image processing.
Knowing how the lens is orientated relative to the digital image sensor in a camera allows image processing software, either in the camera or in post production, to correct the image accordingly. This is contemplated to allow compensation of color degradation over the image or the like. Other types of compensation include distortion or aberration in the image.
The above is contemplated to allow performing correction of digital images comprising the steps of obtaining a digital image using a digital camera having digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens, the lens configured to be movable relative to the housing, and a sensor configured to detect the position of the lens relative to the housing, the sensor configured to transmit position information in electronic form to a processor, and performing image correction using position data from the sensor.
Other advantageous embodiments of the present invention includes an embodiment where the sensor detect position of the second plane relative to the first plane by detecting distance to a point on the second plane. In a presently preferred embodiment the sensor may detect an amount of movement, e.g. by detecting turns on a wheel, sprocket or the like.
In a further advantageous embodiment the sensor may be a magnetic sensor, a resistive sensor, an optical sensor, a capacitive sensor or the like.
Additionally or in combination therewith the sensor may be connected to camera and sensor data may be recorded with image data in the camera.
Still further position data may be stored in a memory device positioned within or connected to the camera. The memory device may be a volatile memory device or in the alternative a non-volatile memory device. Examples include flash memory, hard drives, RAM devices, DPRAM devices, optical drives or any other type of memory device or combination of memory devices.
In a further embodiment of the present invention position data may stored as meta-data in the image file. The image files may be stored in a variety of formats. Examples include file types such as JPG, JPEG, Exif, JFIF, TIFF or Raw image format. In some embodiments multiple files are stored for each image captured by the digital image sensor, e.g. a JPEG image file and a RAW image file.
Even further advantageously an image processor is configured to perform correction of an image based on information received from the sensor or sensors, the correction including vignetting, distortion, aberration or a combination thereof. The image processor may be positioned in the camera or in an external device where the image processor receives an image file and sensor data from the camera.
In an even further advantageous embodiment the device may comprise one or more sensors for detecting all degrees of freedom of the second plane relative to the first plane, including rotation, tilt, shift and/or swing.
In some embodiments the digital image sensor may be a CMOS or CCD device. The digital image sensor may have a 3:2, 4:3, 16:9 form or aspect ratio. Alternatively images from the image sensor may be processed to any form or aspect ratio. The form or aspect ratio is considered as a relation between two sides in a rectangular image.
Also the image correction may comprise correction for vignetting, distortion, aberration or a combination thereof.
Advantageously position data is obtained for three directions and used during the image correction. Additionally correction may be performed for a multitude of frequency intervals and a plurality of angles.
Further advantageously movement from one position of the lens to a different position is followed by using position data to calculate a new focus setting so that focus is maintained before an image is recorded.
Sensors detecting the amount of movement of the legs or connectors 102 are included. The information may be sent or transmitted to be stored in or with image data, e.g. as meta data as described above. Also sensor or sensors detecting and/or registering the movement of the image sensor the parallel to the plane 100 is included. Data from this or these sensors may be stored similarly.
The above advantages and features may be combined and used in any of the aspects of the present invention.
The present invention may relate to the following points
1. A device comprising:
a frame having a first part defining a first plane and a second part defining a second plane, the first part configured to be mounted to a camera body and the second part configured to be mounted to a lens, the second part being movable relative to the first part, and
a sensor configured to detect the position of the second plane relative to the first plane, the sensor configured to transmit position information in electronic form to a processor.
2. A digital camera including a digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens mount for receiving a lens, the lens configured to be movable relative to the housing, and
a sensor configured to detect the position of the lens relative to the housing, the sensor configured to transmit position information in electronic form to a processor.
3. A digital camera including a digital image sensor in a camera housing, the digital image sensor being movably mounted in the camera housing, an image plane defined in the housing by the digital image sensor, the digital camera further comprising a lens mount for receiving a lens, the lens mount fixing the lens to the camera housing, and
a sensor configured to detect the position of the digital image sensor relative to the housing, the sensor configured to transmit position information in electronic form to a processor.
4. The device or digital camera according to any of the points 1-3, wherein the sensor is a magnetic sensor, a resistive sensor, an optical sensor, a capacitive sensor or the like.
5. The device or digital camera according to any of the points 1-4, wherein the sensor connected to camera and sensor data is recorded with image data in the camera.
6. The device or digital camera according to any of the points 1-5, wherein position data is stored in a memory device positioned within or connected to the camera.
7. The device or digital camera according to any of the points 1-6, wherein data is stored as meta-data in the image file.
8. The device or digital camera according to any of the points 1-7, wherein an image processor is configured to perform correction of an image based on information received from the sensor or sensors, the correction including vignetting, distortion, aberration or a combination thereof.
9. The device or digital camera according to any of the points 1-8, wherein the device comprises one or more sensors for detecting all degrees of freedom of the second plane relative to the first plane, including rotation, tilt, shift and/or swing.
10. The device or digital camera according to any of the points 1-9, wherein the image sensor is a CMOS, CCD device or the like.
11. A method of performing correction of digital images comprising the steps of:
obtaining a digital image using a digital camera having digital image sensor in a camera housing, an image plane defined in the housing at the digital image sensor, the digital camera further comprising a lens, the lens configured to be movable relative to the housing, and a sensor configured to detect the position of the lens relative to the housing, the sensor configured to transmit position information in electronic form to a processor, and
performing image correction using position data from the sensor.
12. The method according to point 11, wherein the image correction comprises correction for vignetting, distortion, aberration or a combination thereof.
13. The method according to point 11 or 12, wherein position data is obtained and used during the image correction.
14. The method according to any of the points 11-13, wherein correction is performed for a multitude of frequency intervals and a plurality of angles.
15. The method according to any of the points 11-14, wherein the method comprises movement from one position of the lens to a different position is followed by using position data to calculate a new focus setting so that focus is maintained before an image is recorded.
Number | Date | Country | Kind |
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08011675.9 | Jun 2008 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/DK09/00160 | 6/26/2009 | WO | 00 | 4/4/2011 |