Lens interchangeable camera with protection cover

A digital still camera includes a camera body. A lens unit is retained on the camera body in a removable manner. A protection cover is secured to the camera body, and movable between a closed position and an open position, wherein the protection cover, when in the closed position, closes an exposure opening formed in the camera body, and when in the open position, opens the exposure opening. Cover moving transmission levers set the protection cover in the open position when the lens unit is retained on the camera body, and set the protection cover in the closed position when the lens unit is removed from the camera body. Furthermore, bayonet claw portions engage the lens unit with the camera body. The transmission levers are actuated in response to movement of the bayonet claw portions. A compression coil spring biases the protection cover toward the closed position.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a lens interchangeable camera. More particularly, the present invention relates to a lens interchangeable camera having a camera body and a lens unit for mounting on the camera body, and capable of preventing entry of dust or other wanted material even at the time of exchange.

2. Description Related to the Prior Art

A digital still camera is widely used, and includes an image pickup device or CCD image sensor for photographing an image. A lens interchangeable type of camera includes a camera body and a lens unit secured to the camera body in a removable manner. A mount mechanism is disposed in the camera body for connection with the lens unit. An exposure opening is formed in the center of the mount mechanism for entry of object light from the lens unit into the camera body. When the lens unit is removed from the camera body for exchange, inner elements of the camera body appear through the exposure opening. If dust enters the exposure opening and deposits on a sensor surface of the image pickup device in the camera body, image quality of recorded images will be lowered. A user must handle the lens unit carefully and exchange the lens unit rapidly by considering

JP-A 6-167670 discloses a camera having a photographing optical system movable between a front position and a rear position. When a protection cover for protection from dust is moved to the closed position, the photographing optical system is moved to the rear position. When the protection cover is moved to the open position, the photographing optical system is moved to the front position. The protection cover in the closed position is used for preventing deposition of dust by covering the photographing optical system.

However, environment of various conditions is possible in exchange of the lens unit, for example an outdoor condition, a dirty condition with much dust even in an indoor state. Dust or other unwanted material may enter the camera body through the exposure opening in the exchange no matter how quickly a user handles the lens unit. A camera in JP-A 6-167670 is a type different from a lens interchangeable type. Although dust is prevented from depositing on the photographing optical system in the document, there is no prevention of entry of dust in the camera body.

SUMMARY OF THE INVENTION

In view of the foregoing problems, an object of the present invention is to provide a lens interchangeable camera having a camera body and a lens unit for mounting on the camera body, and capable of preventing entry of dust or other wanted material even at the time of exchange.

In order to achieve the above and other objects and advantages of this invention, a lens interchangeable camera includes a camera body. A lens unit is retained on the camera body in a removable manner. A protection cover is secured to the camera body, and movable between a closed position and an open position, wherein the protection cover, when in the closed position, closes an exposure opening formed for entry of object light from the lens unit into the camera body, and when in the open position, opens the exposure opening. A cover moving mechanism sets the protection cover in the open position when the lens unit is retained on the camera body, and sets the protection cover in the closed position when the lens unit is removed from the camera body.

Furthermore, a retaining mechanism engages the lens unit with the camera body. The cover moving mechanism includes a transmission member, actuated in response to movement of the retaining mechanism, for moving the protection cover to the open position.

Furthermore, a support mechanism supports the protection cover movably between the closed and open positions. A biasing mechanism biases the protection cover toward the closed position.

The retaining mechanism includes a bayonet channel formed in the camera body. A bayonet claw portion is disposed to project from the lens unit, for engagement with the bayonet channel. The transmission member includes first and second lever ends, the first lever end is secured to the protection cover, and the second lever end is pressed by the bayonet claw portion.

The bayonet claw portion is constituted by at least first and second bayonet claw portions disposed in a rotationally symmetric manner with one another. The protection cover is constituted by at least first and second protection cover panels. The first protection cover panel is associated with the first bayonet claw portion and moves in a predetermined direction. The second protection cover panel is associated with the second bayonet claw portion, is disposed adjacent to the first protection cover panel, and moves in reverse to the predetermined direction, to define a space in cooperation with the first protection cover panel.

In one preferred embodiment, a lens detecting sensor detects retention of the lens unit on the camera body. The cover moving mechanism is actuated according to a detection result of the lens detecting sensor, sets the protection cover in the open position when the retention is detected, and sets the protection cover in the closed position in case of lack of detected retention.

Furthermore, a selection switch is shiftable selectively in a manual mode position and an automatic mode position. The selection switch, when set in the manual mode position, causes the cover moving mechanism to set the protection cover in either of the closed and open positions irrespective of the detection result of the lens detecting sensor, and when the in the automatic mode position, operates the cover moving mechanism according to the detection result of the lens detecting sensor.

The manual mode position is constituted by first and second positions, and the selection switch, when in the first position, sets the protection cover in the closed position, and when in the second position, sets the protection cover in the open position.

The cover moving mechanism further includes an endless belt having the protection cover secured thereto. There are first and second pulleys which the endless belt is engaged with to extend between. A motor rotates the first pulley to move the protection cover by turning about the endless belt.

The protection cover is constituted by first and second protection cover panels disposed adjacent to one another. The endless belt includes a first belt portion, disposed to extend between the first and second pulleys, for sliding the first protection cover panel in a predetermined direction. A second belt portion is disposed to extend along the first belt portion to extend, for sliding the second protection cover panel in reverse to the predetermined direction.

The cover moving mechanism further includes at least one transmission gear for transmitting rotation of the motor to the first pulley. The endless belt is a timing belt, and the first and second pulleys are timing pulleys.

Furthermore, a second endless belt is disposed opposite to the endless belt with reference to the exposure opening, for supporting ends of the first and second protection cover panels movably. There are third and fourth pulleys which the second endless belt is engaged with to extend between.

Furthermore, a bayonet type of retaining mechanism engages the lens unit with the camera body.

In one aspect of the invention, a lens interchangeable camera comprising a camera body. A lens unit is retained on the camera body in a removable manner. A transparent protection cover is secured to the camera body, for closing an exposure opening formed for entry of object light from the lens unit into the camera body.

InFIGS. 1 and 2, a digital still camera2is illustrated as a lens interchangeable camera. The digital still camera2includes a camera body5, and a lens unit6or lens assembly as lens barrel fitted on the camera body5in a removable manner. InFIG. 2, a bayonet mount8as bayonet type of retaining mechanism is disposed at a rear end of the lens unit6. A mount mechanism9as bayonet type of retaining mechanism is disposed on a front side of the camera body5, and receives engagement of the bayonet mount8. For the engagement of the mount, at first the lens unit6is moved in the optical axis direction to couple the bayonet mount8with the mount mechanism9. Then the lens unit6is rotated in one direction at a given angle, for tight fitting. In the embodiment, a bayonet mount including plural bayonet claw portions is used. Furthermore, a mount in the invention may be a screw mount well known in the art. Note that the lens unit6is one of plural lens units prepared with different values of focal lengths. InFIG. 1, the lens unit6stands fitted on the camera body5. InFIG. 2, the lens unit6is away from the camera body5.

A lens barrel10of the lens unit contains a photographing optical system including a plurality of lenses/lens groups. A cam mechanism, helicoid mechanism and the like are incorporated in the lens barrel10. When a command signal is output by the camera body5, a focus lens/lens group in the optical system is moved in the optical axis direction to adjust the focus. Also, the bayonet mount8includes bayonet claw portions11and12or bayonet lugs, and electrical contacts13at the rear end of the lens unit6. Note that the numbers of the bayonet claw portions11and12and the electrical contacts13may be changed suitably for the purpose.

The camera body5is in a box form with a small thickness, namely in a shape of a quadrilateral prism, or in a form of a pentaprism type or a shape of SLR type known in the art. An upper side of the camera body5is provided with a power button15, a selection wheel16for image pickup modes, and a shutter release button17. A memory card slot is formed in a lateral face of the camera body5. A card slot lid19is fitted to close the card slot. A rear side of the camera body5is provided with an LCD display panel, a zoom button, a cross-shaped button, an eyepiece and the like.

InFIG. 2, the front of the camera body5has the mount mechanism9for engagement with the lens unit6. Also, a flash light source20is disposed in the front of the camera body5. The mount mechanism9has bayonet channels21and22, electrical contacts23, an exposure opening25, and a protection cover31for closing the opening. The bayonet channel21is positioned in the mount mechanism9to receive the bayonet claw portion11. InFIG. 3, the bayonet channel21includes an insertion opening21aand a retaining slot21b. The insertion opening21areceives insertion of the bayonet claw portion11. The retaining slot21breceives the bayonet claw portion11upon its rotation in the clockwise direction at a predetermined angle for firm retention. Similarly, the bayonet channel22includes an insertion opening22aand a retaining slot22b.

When the lens unit6is rotated, the bayonet claw portions11and12are rotationally shifted from the insertion position ofFIG. 3to the lock position ofFIG. 4. The lens unit6becomes secured to the camera body5. Then the electrical contacts23touch the electrical contacts13of the bayonet mount8, to connect the lens unit6with the camera body5electrically.

The exposure opening25has a quadrilateral shape in the center of the mount mechanism9, and causes object light from the lens unit6to pass toward the inside of the camera body5. InFIG. 2, an image pickup device or CCD image sensor30is disposed behind the exposure opening25inside the camera body5. The protection cover31in the camera body5is movable between a closed position to close the exposure opening25and an open position away from the exposure opening25. InFIGS. 3 and 4, a cover moving mechanism35moves the protection cover31to the closed and open positions. Note that the exposure opening25may have a shape different from the quadrilateral shape, for example circular shape.

InFIG. 3, the protection cover31is constituted by an upper protection cover panel32and a lower protection cover panel33. A lower surface32aof the upper protection cover panel32is a convex surface. An upper surface33aof the lower protection cover panel33is a concave surface. The protection cover31is movable between a closed position and an open position, and when in the closed position ofFIG. 3, closes the exposure opening25with the front of the protection cover panels32and33on the inner side of the camera body5. The lower surface32aof the upper protection cover panel32is received in the upper surface33aof the lower protection cover panel33according to the corresponding shapes when in the closed position. The protection cover31, when in the open position ofFIG. 4, opens the exposure opening25by the upward shift of the upper protection cover panel32and the downward shift of the lower protection cover panel33away from the exposure opening25.

InFIGS. 3 and 4, the cover moving mechanism35includes transmission levers or rods40and41having two lever ends, support plates42for guide, guide rollers43and compression coil springs44and45. The transmission lever40is connected with the upper protection cover panel32. The transmission lever41is connected with the lower protection cover panel33. A first end of the transmission lever40is fixed to a side of the upper protection cover panel32. A second end of the transmission lever40is positioned on the rear of the bayonet channel21. A first end of the transmission lever41is fixed to a side of the lower protection cover panel33. A second end of the transmission lever41is positioned on the rear of the bayonet channel22. When the bayonet claw portions11and12are inserted in respectively the insertion openings21aand22a, the lens unit6is rotated in the clockwise direction at a predetermined angle. Then an end of the bayonet claw portions11and12contacts the transmission levers40and41.

The support plates42guide movement of the protection cover panels32and33in the vertical direction. The support plates42are so disposed that the protection cover panels32and33are located between those, and extend parallel with one another to keep the protection cover panels32and33movable exactly in the opposite directions. Guide channels (not shown) are formed in the support plates42to extend in their longitudinal direction. The guide rollers43are set in the guide channel, and keep the protection cover panels32and33movable vertically. The guide rollers43keep those positioned in the optical axis direction without a shift.

A camera chassis or frame47is included in the camera body5, and is provided with one end of the compression coil spring44secured thereto. A second end of the compression coil spring44is secured to an upper surface of the upper protection cover panel32. A first end of the compression coil spring45is secured to the camera chassis47. A second end of the compression coil spring45is secured to the lower protection cover panel33. Thus, the compression coil spring44biases the upper protection cover panel32in the downward direction. The compression coil spring45biases the lower protection cover panel33in the upward direction. While the lens unit6does not lie on the camera body5, the protection cover31is kept by the compression coil springs44and45in the closed position ofFIG. 3to close the exposure opening25.

The operation of the embodiment is described now. InFIG. 2, the lens unit6is separate from the camera body5. The protection cover31is in the closed position and closes the exposure opening25. SeeFIG. 3. To fit the lens unit6on the camera body5, at first the bayonet claw portions11and12or bayonet lugs are inserted in the insertion openings21aand22a, before the lens unit6is rotated in the clockwise direction as viewed in the front elevation. Thus, the bayonet claw portions11and12are rotationally shifted from the insertion position to the lock position. At the same time, end faces of the bayonet claw portions11and12contact the transmission levers40and41. During application of the rotational force to the transmission levers40and41, the support plates42cause the protection cover panels32and33vertically to move straight. When the bayonet claw portions11and12rotate to the lock position, the protection cover panels32and33shift to the open position ofFIG. 4against the bias of the compression coil springs44and45. Object light from a photographing optical system becomes incident upon a sensor surface of the image pickup device or CCD image sensor30in the camera body5.

Handling of the camera body5is very easy, as the protection cover31is shifted from the closed position to the open position upon securing of the lens unit6. Also, the exposure opening25is kept open while the lens unit6is fitted on the camera body5. No accidental closing occurs, because the protection cover31is prevented from setting in the closed position.

The removal of the lens unit6from the camera body5is referred to. The lens unit6is rotated counterclockwise as viewed in the front. At first, the transmission levers40and41are caused by the bias of the compression coil springs44and45to press the end surfaces of the bayonet claw portions11and12. The upper protection cover panel32moves down while the lower protection cover panel33moves up. The bayonet claw portions11and12rotate from the lock position to the insertion position, to shift the protection cover31from the open position to the closed position. Thus, the exposure opening25becomes closed by the protection cover panels32and33in a light tight manner, as the lower surface32ais combined or engaged with the upper surface33ato shield light.

Therefore, dust can be prevented from entry into the camera body5during exchange of the lens unit6, because the protection cover31closes the exposure opening25upon removal of the lens unit6. Also, the lower surface32aof the upper protection cover panel32and the upper surface33aof the lower protection cover panel33have concave and convex forms, or patterned forms of recesses and projections. When the protection cover31is in the closed position, the concave surface or recesses are engaged with the convex surface or projections, to prevent entry of dust between the protection cover panels32and33. The guide rollers43of the protection cover panels32and33are set inside a guide channel. The protection cover31can continue to close the exposure opening25tightly without a gap even when pressure is applied to the protection cover31from the side of the lens unit6.

The cover moving mechanism35of the above embodiment mechanically shifts the protection cover31. InFIGS. 5-7, another preferred embodiment having a sensor for the lens unit6is illustrated. Elements similar to the above embodiments are designated with identical reference numerals.

InFIG. 5, a selection switch50is disposed on the front of the camera body5, and sets a selected one of an automatic mode and a manual mode. In the automatic mode, the protection cover31can shift to the open position only after detection of mounting of the lens unit6. In the manual mode, priority is given to preference of a user, to set the protection cover31in a selected one of the open and closed positions according to a manual input of the user. The automatic mode is described hereinafter with reference toFIG. 5according to a setting of the selection switch50.

InFIG. 6, a cover moving mechanism51is disposed behind the mount mechanism9to shift the protection cover31between the closed and open positions. The cover moving mechanism51includes an endless belts or timing belts53with teeth, timing pulleys54with teeth, and a motor55.

The timing pulleys54are disposed near to upper and lower ends of the protection cover panels32and33. A first one of the timing pulleys54is disposed on the upside. A second one of the timing pulleys54is disposed on the downside. Each of the endless belts or timing belts53extends from the first to the second of the timing pulleys54in a turnable manner. An example of the material for the timing belt53is rubber, elastomer or other elastic compounds. Teeth of the timing belt53are arranged regularly, and are meshed with teeth of the timing pulleys54. Flanges are formed with the timing pulleys54, are indicated in the solid line in the drawing, and keep the timing belt53in mesh with the timing pulleys54without a drop.

A fastener60with a screw or the like is provided on each of two sides of the upper protection cover panel32. A fastener61is provided on each of two sides of the lower protection cover panel33. The fastener60is in a quadrilateral shape, and attaches the upper protection cover panel32to a first belt portion62of the endless belt or timing belt53nearer to the protection cover31. The fastener61is in an L shape, and attaches the lower protection cover panel33to a second belt portion64of the timing belt53farther from the protection cover31. The fastener61has a shape not contacting the first belt portion62of the timing belt53. Note that the shapes of the fasteners60and61are not limited. Examples of fastening of the fasteners60and61to the timing belt53are retention with a screw, adhesive agent and other known methods.

The motor55is contained in a lower portion of the camera body5. A motor gear65is connected with an output shaft of the motor55. A transmission gear66is meshed with the motor gear65. One of the timing pulleys54is concentrically positioned on the transmission gear66. When the motor55is energized, the endless belt or timing belt53is driven to turn about by the motor gear65, the transmission gear66and the timing pulleys54in cooperation. As the fasteners60and61are connected with the timing belt53, the motor55rotates in the direction of the arrow A inFIG. 6to move up the upper protection cover panel32and move down the lower protection cover panel33. Also, the motor55rotates in the direction of the arrow B inFIG. 7to move down the upper protection cover panel32and move up the lower protection cover panel33. An L-shaped guide (not shown) is disposed in a moving region of the protection cover panels32and33for contacting their side surface and rear surface. The guide regulates movement of the protection cover panels32and33in relation to the horizontal directions and optical axis direction. When the protection cover31is set in the closed position, the exposure opening25is closed by the front portions of the protection cover panels32and33.

A lens detecting sensor67is disposed on the camera body5for detecting presence of the lens unit6. Examples of the lens detecting sensor67include a limit switch of a small type, a proximity sensor and the like. The lens detecting sensor67detects the bayonet claw portion12in the lock position.

A closed position detector or sensor68and an open position detector or sensor69are incorporated in the camera body5. Examples of those include a limit switch of a small type, a proximity sensor and the like in a manner similar to the lens detecting sensor67. When the closed position detector68detects the fastener61on the lower protection cover panel33, the protection cover31is found set in the closed position. When the open position detector69detects the fastener61, the protection cover31is found set in the open position. Note that a target portion detectable by the closed position detector68and the open position detector69may be positioned in a manner distinct from the fastener61of the embodiment.

Operation of circuits in shifting the protection cover31in the closed and open positions is described. InFIG. 8, a controller70controls elements in the digital still camera2. Various circuits are connected to the controller70, including the selection switch50, the motor55, the lens detecting sensor67, the closed position detector68and the open position detector69.

Upon the selective setting of the automatic mode, the controller70controls various elements according to an automatic mode program. The selection switch50is set in a selected one of the open and closed positions, so the controller70drives the motor55. The controller70, if the selection switch50is set for the open position, shifts the protection cover31to the open position, and if the selection switch50is set for the closed position, shifts the protection cover31to the closed position. Note that the motor55is inactive if the protection cover31is in the open position after selective setting of opening the protection cover31. Also, the motor55is inactive if the protection cover31is in the closed position after selective setting of closing the protection cover31.

When the bayonet claw portion12is shifted from the insertion position ofFIG. 6to the lock position ofFIG. 7, the lens detecting sensor67detects the bayonet claw portion12, and sends a detection signal to the controller70. The controller70evaluates the output of the lens detecting sensor67, and determines that the lens unit6is fitted on the camera body5in response to the detection signal.

InFIG. 6, when the protection cover31is in the closed position, the closed position detector68detects the fastener61, and sends a first detection signal to the controller70. The controller70responsive to the first detection signal detects that the protection cover31is in the closed position.

InFIG. 7, when the protection cover31is in the open position, the open position detector69detects the fastener61, and sends a second detection signal to the controller70. The controller70responsive to the second detection signal detects that the protection cover31is in the open position.

The motor55is controlled by the controller70. The motor55rotates the motor gear65in the direction of the arrow A ofFIG. 6, to shift the protection cover31from the closed position to the open position. Also, the motor55rotates the motor gear65in the direction of the arrow B ofFIG. 7, to shift the protection cover31to the closed position.

In operation, the selection switch50is set for the automatic mode. This is for the use of the digital still camera2. SeeFIG. 5. While the lens unit6is separate from the camera body5, the protection cover31closes the exposure opening25. The controller70receives a first detection signal from the closed position detector68.

When the bayonet claw portion12shifts from the insertion position to the lock position by fitting the lens unit6on the camera body5, the lens detecting sensor67detects the bayonet claw portion12to send a detection signal to the controller70. The lens unit6is found fitted on the camera body5by the controller70, which drives the motor55.

The controller70causes the motor55to rotate in the direction of the arrow A inFIG. 6. The endless belt or timing belt53causes the fastener60to move up the upper protection cover panel32, and causes the fastener61to move down the lower protection cover panel33. When the protection cover panels32and33shift to the open position, the open position detector69detects the fastener61, to send a second detection signal to the controller70. The controller70stops the motor55upon receipt of the second detection signal. Thus, entry of dust into the camera body5is avoided during exchange of the lens unit6, because the protection cover31shifts to the open position only after fitting the lens unit6on the camera body5.

When the lens unit6, to be removed from the camera body5, is rotated in the counterclockwise direction, then the bayonet claw portion12moves from the locking position to the insertion position. There is no detection of the lens detecting sensor67for the bayonet claw portion12. No detection signal is input to the controller70. Thus, the lens unit6is found removed from the camera body5by the controller70, which controls the motor55.

The controller70causes the motor55to rotate in the direction of the arrow B inFIG. 7. The endless belt or timing belt53moves down the upper protection cover panel32, and moves up the lower protection cover panel33. When the protection cover panels32and33shift to the closed position, the open position detector69detects the fastener61, to send a first detection signal to the controller70. The controller70stops the motor55upon receipt of the first detection signal. Thus, entry of dust into the camera body5is avoided during exchange of the lens unit6, because the protection cover31shifts to the closed position shortly before removing the lens unit6from the camera body5.

The use of the selection switch50is specifically effective in the maintenance of the camera body5. When the manual mode is set by use of the selection switch50, the protection cover31can be intentionally set in the open position. Accordingly, the handling of the digital still camera2can be easy.

In the present embodiment, the timing belts53are two belts on the right and left sides. However, only one timing belt in connection with the motor55can be used on the right side in the drawing. On the left side, a mechanism for supporting the protection cover panels32and33may be a free timing belt turnable in a separate manner from the motor55, a friction belt with pulleys without teeth, or the like.

InFIG. 9, another preferred camera is illustrated, in which a transparent protection cover75is stationary, and closes the exposure opening25.

Examples of materials for the transparent protection cover75and glass, resin and other transparent substances. The protection cover75is fitted in the exposure opening25from the inside of the camera body5and kept fixed. Thus, the inside of the camera body5is kept enclosed. The protection cover75also has a sufficient thickness for preventing flexing or damage even when pressure is applied to the protection cover75from the side of the lens unit6. Dust is prevented from entry in the exposure opening25while the lens unit6is removed from the camera body5.

As the transparent protection cover75closes the lens mount of the camera body5hermetically, entry of droplets of water or other material can be prevented during exchange of the lens unit6. If dust deposits on the surface of the protection cover75, it is possible to eliminate the dust by blowing compressed gas, wiping with a brush, or the like.

Unlike the transparent protection cover75directly fitted in the exposure opening25, it is possible to fit the protection cover75on the inside or outside of the exposure opening25. Note that the protection cover75is so positioned as to ensure the connection of the electrical contacts23on the mount mechanism9with the electrical contacts13on the bayonet mount8.

In the above embodiments, the protection cover panels32and33are vertically movable. However, the protection cover31can be constructed in various modified manners. For example, panels of the protection cover31may be movable horizontally in opposite directions. Also, a plurality of blades may constitute the protection cover31, and may shift toward and away from the center of the exposure opening25in the manner similar to a mechanical shutter of a multi blade type.

Although the camera of the above embodiments is a digital still camera, a camera of the invention may be a camera for use with photo film as silver halide photosensitive material.