Optical shutter for miniature cameras
View Patent ↗The invention relates to a shutter for an optical imaging system, e.g. a digital camera. The shutter comprises an interface between a transparent body and a capillary space. Light rays introduced to the active area of the interface are reflected by total internal reflection when the capillary space is filled with a gas. The light rays are transmitted through the interface when the capillary space is rapidly filled with a liquid. Thus, the light rays are either absorbed or reflected towards an image sensor, depending on the state of the shutter. The liquid is delivered to the capillary space through at least one duct which is positioned opposite the active area.
1. A device comprising:
an interface between a transparent body and a capillary space,
at least one fluid reservoir,
an amount of fluid,
one or more fluid displacement elements to displace the amount of fluid between said fluid reservoir and said capillary space in order to change an operating state of the device from a first operating state to a second operating state, and in order to change the operating state of said device from said second operating state back to said first operating state, said first operating state allowing total internal reflection of oblique light rays impinging on an active area of said interface and said second operating state allowing transmission of said oblique light rays through said active area of said interface,
one or more fluid ducts opposite said active area for delivering the amount of fluid to said capillary space,
one or more further ducts for transferring a second fluid from said capillary space when the operating state is changed from the first operating state to the second operating state, and
an absorber configured to absorb the light rays transmitted through said active area of said interface.
2. The device according to claim 1 wherein said displacement elements comprise electrodes configured to electrostatically displace said fluid.
3. The device according to claim 1 wherein said displacement elements are configured to change the internal pressure of at least one fluid reservoir.
4. The device according to claim 3 wherein said internal pressure is adapted to be changed by at least one actuator selected from the group consisting of a piezoelectric actuator, an electromagnetic actuator and an electrostatic actuator.
5. The device according to claim 1 wherein the distance between the amount of fluid and the active area is greater than 0.5 times the width of the active area when the shutter is in the first operating state.
6. The device according to claim 1 wherein said device comprises an electrode arrangement to electrostatically confine the amount of fluid within the boundaries of said active area.
7. An optical device comprising:
imaging optics,
an image sensor, and
an optical shutter,
said optical shutter in turn comprising:
an interface between a transparent body and a capillary space,
at least one fluid reservoir,
an amount of fluid,
one or more fluid displacement elements to displace the amount of fluid between said fluid reservoir and said capillary space in order to change an operating state of said shutter from a first operating state to a second operating state, and in order to change the operating state of said shutter from said second operating state back to said first operating state, said first operating state allowing total internal reflection of oblique light rays impinging on an active area of said interface and said second operating state allowing transmission of said oblique light rays through said active area of said interface,
one or more fluid ducts opposite said active area for delivering the amount of fluid to said capillary space,
one or more further ducts for transferring a second fluid from said capillary space when the operating state is changed from the first operating state to the second operating state, and
an absorber configured to absorb the light rays transmitted through said active area of said interface.
8. The optical device according to claim 7 wherein said optical device is a portable device.
9. The optical device according to claim 7 wherein said optical device comprises wireless data communication capabilities.
10. A method to control optical exposure of an image sensor by a shutter, said shutter comprising an interface between a transparent body and a capillary space, said method comprising:
guiding light rays to an active area of said interface at an oblique angle,
displacing an amount of fluid between at least one fluid reservoir and said capillary space through one or more fluid ducts in order to change an operating state of said shutter from a first operating state to a second operating state, and in order to change the operating state of said shutter from said second operating state back to said first operating state, said first operating state allowing total internal reflection of oblique light rays impinging on the active area of said interface and said second operating state allowing transmission of said oblique light rays through said active area of said interface, at least one of said fluid ducts being opposite said active area,
transferring a second fluid from said capillary space through one or more further ducts when the operating state is changed from the first operating state to the second operating state,
absorbing light rays transmitted through said active area, and
in the first operating state guiding light rays reflected from said active area to said image sensor.
11. The method according to claim 10 , said method further comprising:
setting the shutter to the first operating state,
resetting or activating pixels of the image sensor,
exposing said pixels to the reflected light rays during a predetermined exposure time,
setting the shutter to the second operating state, and
reading signals from said pixels to a memory or to a signal processing unit.
12. An optical exposure controlling means comprising:
an interface between a transparent means and a capillary space,
a fluid storage means,
an amount of fluid,
a fluid displacement means for displacing the amount of fluid between said fluid storage means and said capillary space in order to change an operating state of said exposure controlling means from a first operating state to a second operating state, and in order to change the operating state of said exposure controlling means from said second operating state back to said first operating state, said first operating state allowing total internal reflection of oblique light rays impinging on an active area of said interface and said second operating state allowing transmission of said oblique light rays through said active area of said interface,
one or more fluid guiding means opposite said active area for delivering the amount of fluid to said capillary space,
one or more fluid transferring means for transferring a second fluid from said capillary space when the operating state is changed from the first operating state to the second operating state, and
absorbing means for absorbing the light rays transmitted through said active area of said interface.
13. The exposure controlling means according to claim 12 wherein said displacement means comprise electrodes arranged to electrostatically displace said amount of fluid.