Image pickup apparatus and lens device

An image pickup apparatus having a construction which enhances the degree of freedom in layout and enables size reduction. The image pickup apparatus includes a lens barrel, and an upper barrier group and a lower barrier group that open and close a front face of the lens barrel. The upper and lower barriers are rotated about respective upper and lower barrier rotary shafts disposed on a plane perpendicular to an optical axis of the lens barrel. A first spur gear and a second spur gear connected thereto are provided on a side of the lens barrel. A member transmits the rotation of the first spur gear driven by a motor to the lower barrier group, and another member transmits the rotation of the second spur gear to the upper barrier group.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image pickup apparatus and a lens device, which are provided with a barrier for protecting the front face of a lens barrel.

2. Description of the Related Art

Conventionally, there have been proposed various types of barriers each for opening/closing the front face of a camera, so as to protect a photographic lens of the camera.

In image pickup apparatuses provided with barriers of the above-mentioned kind, most of the barriers have conventionally been configured to vertically or laterally open/close flat plates disposed in front of a lens barrel, as disclosed in Japanese Patent Laid-Open Publication No. 2006-98486.

Further, Japanese Patent Laid-Open Publication No. 2002-258133 discloses a technique in which a barrier, which is divided into an upper part and a lower part, is opened and closed along a dome-shaped path about a point on the axis of the lens barrel.

FIGS. 28A and 28Bare perspective views of a conventional barrier mechanism disclosed in Japanese Patent Laid-Open Publication No. 2002-258133.FIG. 28Ashows a state in which a barrier is closed, andFIG. 28Bshows a state in which the barrier is open. This barrier is formed into a spherical shell shape having a center at a point on the optical axis of a lens (i.e. the point on the axis of the lens barrel). Further, as mentioned hereinbefore, the barrier is divided into an upper half barrier62aand a lower half barrier, and these barriers can be rotated about respective rotary shafts (one of which is denoted by68m) which are supported on bearings provided in laterally symmetrical relation on the opposite sides of the lens barrel and have the same rotational axis perpendicular to the optical axis and extending through the point on the optical axis.

Further, on the front face of the lens barrel, there is provided an opening/closing ring21for opening and closing the barrier, in a manner rotatable about the optical axis of the lens. When the opening/closing ring21is rotated, the upper half barrier62aand the lower half barrier operate in respective opposite directions with respect to the optical axis, whereby the barrier is opened and closed.

However, in the above-described conventional barrier, the upper half barrier and the lower half barrier are configured to rotate about the same rotational axis, there arises the following problem: In a case where for further size reduction, the upper half barrier and the lower half barrier are each further divided in two, i.e. the barrier is comprised of four barrier blades, a rotary shaft provided at each of the left and right sides of the lens barrel requires a thickness corresponding to the four barrier blades. Therefore, the thickness of the barrier forms an obstacle to size reduction.

Furthermore, the barrier constructed as above needs a large rotary ring for driving the upper half barrier and the lower half barrier on the front side of the lens barrel, which lowers the degree of freedom in layout, and also becomes an obstacle to size reduction.

SUMMARY OF THE INVENTION

The present invention provides an image pickup apparatus and a lens device having a construction which enhances the degree of freedom in layout and enables size reduction.

In a first aspect of the present invention, there is provided an image pickup apparatus including a lens barrel, and a barrier that rotates about a barrier rotary shaft provided on a plane perpendicular to an optical axis of the lens barrel, for opening and closing a front face of the lens barrel, wherein the barrier is divided into at least a first barrier and a second barrier, the image pickup apparatus comprising a first gear provided on a side of the lens barrel, a second gear connected to the first gear and configured to rotate in a direction opposite to a direction of rotation of the first gear, a first transmission member configured to transmit the rotation of the first gear to thereby cause the first barrier to rotate, and a second transmission member configured to transmit rotation of the second gear to thereby cause the second barrier to rotate in a direction opposite to a direction of the rotation of the first barrier.

With the arrangement of the image pickup apparatus according to the first aspect of the present invention, the first transmission member transmits the rotation of the first gear provided on the side of the lens barrel to thereby cause the first barrier to rotate, and the second transmission member transmits the rotation of the second gear to thereby cause the second barrier to rotate in the direction opposite to the direction of the rotation of the first barrier. This makes it unnecessary to provide a rotary ring on a front side of the lens barrel, which increases the degree of freedom in layout, and also contributes to size reduction.

In an image pickup apparatus according to an embodiment of the first aspect, the first barrier rotates about a first barrier rotary shaft, and the second barrier rotates about a second barrier rotary shaft. Therefore, it is possible to reduce thickness along the rotary shafts, which also contributes to size reduction.

In an image pickup apparatus according to an embodiment of the first aspect, the first gear and the second gear module are of the same module and have the same number of teeth. Therefore, by driving one of the first and second gears, it is possible to drive the first and second barriers in respective directions opposite to each other.

In an image pickup apparatus according to an embodiment of the first aspect, the center of the rotation of the first gear coincides with an axis of the first barrier rotary shaft, and/or the center of rotation of the second gear coincides with an axis of the second barrier rotary shaft. Therefore, it is possible to realize an efficient barrier mechanism which is small in transmission loss of a driving force.

In an image pickup apparatus according to an embodiment of the first aspect, a rabbet which is superposed on the first barrier in an optical axis direction when the barrier is in a closed state is formed in the second barrier, and at the rabbet, the second barrier is positioned closer to an object than the first barrier. Therefore, it is possible to make the appearance in the barrier closed state of the image pickup apparatus look natural.

In an image pickup apparatus according to an embodiment of the first aspect, the second barrier in which the rabbet is formed is rotated to a position in the closed state of the barrier earlier than the first barrier. This makes it possible to prevent the rabbet from being undesirably caught.

In an image pickup apparatus according to an embodiment of the first aspect, the second transmission member transmits rotation of the second gear driven by a drive section, via an elastic member, thereby causing the second barrier to rotate. Therefore, it is possible to absorb a play in rotation and a phase displacement between the gears, which are inevitable to gear operation, as well as to effect preloading in the open and closed state of the barrier.

In a second aspect of the present invention, there is provided a lens device that is used in an optical apparatus, and includes a lens barrel, and a barrier that rotates about a barrier rotary shaft provided on a plane perpendicular to an optical axis of the lens barrel, for opening and closing a front face of the lens barrel, wherein the barrier is divided into at least a first barrier and a second barrier, the lens device comprising a first gear provided on a side of the lens barrel, a second gear connected to the first gear and configured to rotate in a direction opposite to a direction of rotation of the first gear, a first transmission member configured to transmit the rotation of the first gear to thereby cause the first barrier to rotate, and a second transmission member configured to transmit rotation of the second gear to thereby cause the second barrier to rotate in a direction opposite to a direction of the rotation of the first barrier.

With the arrangement of the lens device according to the second aspect of the present invention, it is possible to obtain the same advantageous effects as provided by the image pickup apparatus of the first aspect of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described in detail below with reference to the accompanying drawings showing an embodiment thereof. An image pickup apparatus according to the embodiment is applied to a video camera.

FIGS. 1 and 2are views of essential parts of the video camera according to the embodiment of the present invention.FIGS. 1 and 2show a lens barrel and a barrier section in side view. The lens barrel has a photographic lens provided in the front thereof. The barrier section protects the front face of the lens barrel.FIG. 1shows a barrier closed state, whileFIG. 2shows a barrier open state. In the present embodiment, an object side of the photographic lens provided in the lens barrel101is defined as a front side.FIG. 3is a perspective view of the lens barrel and the barrier section in the barrier open state of the video camera, as viewed obliquely from the front of the video camera.

In front of the photographic lens, barrier groups102and103for forming the dome-shaped barrier section having a smoothly curved surface corresponding to a convex surface of the photographic lens from its periphery to a front surface are arranged such that the barrier groups102and103can be driven about barrier rotary shafts104projecting from a side surface of the lens barrel101. The barrier rotary shafts104extend on a plane perpendicular to an optical axis of the lens barrel101.

The barrier groups102and103can be selectively driven into the closed state for fully covering the lens front as shown inFIG. 1, and into the open state for allowing effective light flux to enter the photographic lens, as shown inFIG. 2.

The barrier rotary shafts104are formed by an upper barrier rotary shaft104a(first barrier rotary shaft) and a lower barrier rotary shaft104b(second barrier rotary shaft), which are disposed at respective locations symmetrical with respect to the optical axis of the lens as viewed from the side of the video camera. As will be described hereinafter with reference toFIG. 13, barrier rotary shafts204similar to these barrier rotary shafts104are provided on an opposite side of the lens barrel101.

In the present embodiment, the upper barrier group102(first barrier group) and the lower barrier group103(second barrier group) forming the dome-shaped barrier section are each formed by two barrier blades. In other words, the dome-shaped barrier section is formed by the four barrier blades in total. In the present embodiment, a barrier102aof the upper barrier group102and a barrier103aof the lower barrier group103for covering a central part of the lens around the optical axis in the closed state will be referred to as “the central barrier”, and barriers102band103bfor covering the outer part of the lens will be referred to as “the outer barrier (second driven barrier)”.

FIG. 4is an exploded perspective view of the barrier section. The central barrier102aand the outer barrier102bhave a hole402and a hole403formed through respective ends thereof, for having the upper barrier rotary shaft104arotatably fitted therein. The two upper barriers, i.e. the upper central barrier102aand the upper outer barrier102bhave the upper barrier rotary shaft104ainserted therethrough, and a retaining ring401prevents the two barriers102aand102bfrom falling off the upper barrier rotary shaft104a. Similarly, the two lower barriers, i.e. the lower central barrier103aand the lower outer barrier103bare fitted on the lower barrier rotary shaft104b, and a retaining ring prevents the two barriers103aand103bfrom falling off the lower barrier rotary shaft104b.

The upper barrier group102and the lower barrier group103turn about the upper barrier rotary shaft104aand the lower barrier rotary shaft104b, respectively, through a predetermined angle in respective opposite directions as described hereinafter, whereby a lens opening/closing operation is performed. In short, the upper barrier group102turns upward, and the lower barrier group103turns downward, whereby a lens opening operation is performed.

In the upper barrier group102, with a barrier opening/closing mechanism, described hereinafter, the upper central barrier102ais moved upward to a position superposed on the upper outer barrier102b, and is further moved upward together with the upper outer barrier102bin a state superposed thereon until the upper barrier group102is brought into the open state, as shown inFIG. 2. Similarly, the lower central barrier103aof the lower barrier group103is moved downward to a position superposed on the lower outer barrier103b, and is further moved downward together with the lower outer barrier103bin the superposed thereon until the lower barrier group103is brought into the open state. For this reason, in each of the upper and lower barrier groups, the central barrier disposed inward of the associated outer barrier is required to rotate through a larger rotational angle than the outer barrier, for opening or closing of the barrier section.

Next, a description will be given of the barrier opening/closing mechanism. As shown inFIG. 4, the central barrier102awhich is required to rotate through a larger rotational angle for opening/closing the barrier section has the end thereof formed with a slot404. On the other hand, the outer barrier102bhas a shaft405projecting laterally from the end thereof. The shaft405is engaged with the slot404in a manner turnable within the same.

FIG. 5is a view showing the position of the upper barrier group102in the barrier closed state of the video camera.FIG. 6is a view showing the position of the upper barrier group102in an intermediate state in which only the central barrier is operating.FIG. 7is a view showing the position of the upper barrier group102in the barrier open state of the video camera. Hereafter, a description will be mainly given of a barrier mechanism for the upper barrier group102, and the description applies to a barrier mechanism for the lower barrier group103.

The diameter of the slot404formed in the end of the central barrier102ais slightly larger than that of the shaft405extending from the end of the outer barrier102b. The slot404has a shape that enables the central barrier102ato rotate about the upper barrier rotary shaft104athrough an angle corresponding to the difference between a rotational angle required for opening and closing the outer barrier102band a rotational angle required for required for opening and closing the central barrier102a.

For example, in the present example, the rotational angle required for opening the central barrier is set to 39°, and the rotational angle required for opening the outer barrier is set to 24°. Therefore, the slot404has a shape which enables the central barrier102ato rotate through 15° which is the difference between the two angles (39°−24°=15°. The shaft405is formed on the end of the outer barrier such that the shaft405is positioned in an end of the slot404in the end of the central barrier in the barrier closed state of the video camera.

The slot404and the shaft405are formed in the central barrier102aand on the outer barrier102b, respectively, at the locations matching the above conditions, whereby the barrier section can be formed such that the outer barrier102bis driven in accordance with the operation of the central barrier102a, and when the video camera is in the barrier open state, the barrier group102is in a barrier-superposed state.

More specifically, in the barrier mechanism of the present embodiment, when the central barrier102arotates through 15° from the barrier closed state (seeFIG. 5) to enter the intermediate state (seeFIG. 6), the shaft405of the outer barrier102bcomes into contact with the other end of the slot404in the central barrier102a. Thereafter, the upper barrier group102rotates through 24° with the central barrier102aand the outer barrier102bsuperposed one upon the other, into the barrier open state (seeFIG. 7).

The central and outer barriers of the upper and lower barrier groups are caused to perform the motions described above about the upper and lower barrier rotary shafts by a drive section, described hereinafter, whereby the barrier opening/closing operation is performed.

The above-described construction makes it possible to realize a space-saving dome-shaped barrier section. Thus, the four separate barriers are divided into two barrier groups each formed by two barriers, and the two rotary shafts are provided for the respective barrier groups, whereby it is possible to reduce the thickness of the barrier section along the rotary shaft to thereby achieve size reduction.

FIG. 8is a cross-sectional view of the shape of the barrier groups forming the dome-shaped barrier section.FIG. 8shows a cross section taken in the vertical direction orthogonal to the optical axis. Between contact surfaces of the central barrier102aand the outer barrier102badjacent to each other and between those of the central barrier103aand the outer barrier103b, there are formed required minimum clearances, respectively, so as to realize space saving of the barrier section by causing the barriers to be superposed one upon the other in the barrier open state of the video camera. The barrier groups form a dome-shaped face with the barrier rotary shafts104(104aand104b) as respective centers.

The front surfaces of the respective central barriers102aand103aof the barrier section in the present embodiment are curved with the center of curvature located at one point104c(indicated by a mark “X” inFIG. 8) on the optical axis.

For example, as shown inFIG. 9, assuming that the surfaces of the respective barriers of each barrier group are formed into a dome shape with the associated barrier rotary shaft104aor104bas its center, the front surface of the barrier section as an appearance surface have a recess formed in the central portion thereof and hence look unnatural.

To solve this problem, in the present embodiment, the central barrier of each of the barrier groups is formed to have the front surface thereof curved with the center of curvature located at the point104con the optical axis, as shown inFIG. 8. This makes it possible to prevent a recess from being formed in the central portion of the barrier section to thereby make the appearance of the barrier section look natural in the barrier closed state of the video camera.

Further, the barrier group in the present embodiment is configured such that in the barrier open state of the video camera, the central barrier is positioned in front of the outer barrier in a superposed state, and in the barrier closed state of the same as well, an outer end of the central barrier and an inner end of the outer barrier are superposed one upon the other in front of the lens. Thus, even when a load is applied toward the central portion of the lens in the barrier closed state of the video camera, it is possible to receive the load by the two barriers, so that the lens can be protected more securely.

FIG. 10is a schematic view of the arrangement of the lens barrel101and the barrier groups102and103.FIG. 11is a perspective view of essential parts of the barrier mechanism in the barrier open state of the video camera. In the barrier mechanism of the present embodiment, the lens barrel101is formed with outer barrier receiving parts1001aand1001b. Each of the receiving parts1001aand1001bhas a shape offset from the rear surface of the associated outer barrier by a slight clearance required for driving. A static pressure load applied to the barriers in the barrier closed state of the video camera can be received by the receiving parts1001aand1001b. This makes it possible to protect a front lens101aof the lens barrel101more securely without scratching the same.

Further, a rib801(802) having a height approximately equal to the thickness of the central barrier102a(103a) is formed on the outer end of the outer barrier102b(103b).

FIG. 12is a cross-sectional view of the arrangement of the lens barrel101, the barrier groups102and103, and a body cover1201. The body cover1201is required to accommodate a barrier opening/closing path. For this reason, a clearance1202between the body cover1201and the front surface of each outer barrier is determined by each of the central barriers102aand103awhich move along an outermost path. In short, the clearance1202created in the barrier closed state of the video camera is approximately equal to a distance between the front surface of the out barrier and the front surface of the central barrier. Therefore, the rib801(802) having the height approximately equal to the thickness of the central barrier102a(103a) is formed on the outer end of the outer barrier102b(103b), whereby it is possible to hide the clearance in the barrier closed state of the video camera to thereby improve the appearance of the video camera.

FIG. 13is an exploded perspective view of the lower central barrier103aand a barrier arm1504. The central barrier103ais formed with a hole1502for connection with the barrier arm1504connected to a drive source described hereinafter. A shaft1504aprojecting from an end of the barrier arm1504is fitted in the hole1502of the central barrier103avia a sheet metal member1601having the barrier rotary shaft104bafter inserting the shaft1504athrough an elongated arcuate hole1601aof the sheet metal member1601, whereby the barrier arm1504and the central barrier103aare unitized.

This construction applies to the upper central barrier102aand a barrier arm1304(seeFIG. 14). More specifically, the central barrier102ais formed with a hole1302for connection with the barrier arm1304. A shaft1304aprojecting from an end of the barrier arm1304is fitted in the hole1302of the central barrier102avia a sheet metal member1602having the barrier rotary shaft104aafter inserting the shaft1304athrough an elongated arcuate hole1602aof the sheet metal member1602, whereby the barrier arm1304and the central barrier102aare unitized.

The barrier arm1504(1304) connected to the drive source, described hereinafter, is connected to the central barrier103a(102a) as described above, so that in the assembling process, it is possible to assemble the C-shaped central barrier103a(102a) after checking the operation of the drive source, to thereby reduce occurrence of assembly failure.

FIG. 14is an exploded perspective view of a shaft-associated assembly portion including the upper barrier rotary shaft104a. Further,FIG. 15is a cross-sectional view of the shaft-associated assembly portion including the upper barrier rotary shaft104a. This shaft-associated assembly portion is basically comprised of portions of the upper barrier group102, the barrier arm1304, a gear-equipped member1306, described hereinafter, and a toggle spring1305as an elastic member.

The barrier arm1304is provided in a coaxially rotatable relation with the upper barrier rotary shaft104a. On one surface of the sheet metal member1602from which the upper barrier rotary shaft104aprojects, the upper central barrier102aand the outer barrier102bare placed one upon the other by having the upper barrier rotary shaft104ainserted therethrough, and the retaining ring401is fitted on the barrier rotary shaft104ato prevent the central barrier102aand the outer barrier102bfrom coming off.

On the other surface of the sheet metal member1602, there are mounted the barrier arm1304that has the upper barrier rotary shaft104ainserted therein, the gear-equipped member1306, referred to hereinafter, and the toggle spring1305, referred to hereinafter, and a retaining ring1309is fitted on the barrier rotary shaft104ato prevent the members1304,1305, and1306from coming off.

The member1306mounted on the upper barrier rotary shaft104ahas a spur gear1306a(seeFIG. 16) which rotates about the upper barrier rotary shaft104a. The pitch diameter of the spur gear1306a(first gear) is set to a value equal to a distance between the two barrier rotary shafts104aand104b. The barrier arm1304, the member1306, and the toggle spring1305are examples of transmission members for transmitting rotation of the spur gear1306ato the upper barrier group102having the upper barrier rotary shaft104ainserted therethrough.

A shaft-associated assembly portion including the lower barrier rotary shaft104bis also provided with a member1307having a spur gear1307a(second gear) which rotates about the center of rotation of the lower barrier group103, and is identical in construction to the shaft-associated assembly portion including the upper barrier rotary shaft104a(seeFIG. 19). The member1307is an example of a second transmission member for transmitting rotation of the spur gear1307ato the lower barrier group103having the lower barrier rotary shaft104binserted therethrough.

The spur gear1307aof the member1307, which rotates about the center of rotation of the lower barrier group103, also has a pitch diameter set to the value equal to the distance between the two barrier rotary shafts104aand104b. The spur gears1306aand1307amounted on the respective upper and lower barrier rotary shafts104aand104band connected to each other are of the same module and have the same number of teeth.

With this construction, it is possible to drive one of the adjacent spur gears1306aand1307aconnected to each other, to thereby rotate the upper and lower barrier groups102and103about the respective barrier rotary shafts104aand104bin opposite directions, respectively. As a consequence, the upper barrier group102and the spur gear1306aconnected to the drive source, described hereinafter, can be rotated coaxially, which makes it possible to realize an efficient barrier mechanism which is capable of reducing loss in driving force transmission.

Further, the gear-equipped member1306and the barrier arm1304mounted on the upper barrier rotary shaft104ahave respective projecting arms1306band1304bformed at respective locations circumferentially displaced from the barrier rotary shaft104a.

FIG. 16is a perspective view of the shaft-associated assembly portion including the upper barrier rotary shaft104a. As described hereinbefore, this shaft-associated assembly portion is provided with the gear-equipped member1306, the barrier arm1304, and the toggle spring1305. In the barrier mechanism of the present embodiment, the gear-equipped member1306is inserted through a coil1305aof the toggle spring1305and is thereby equipped with the coil1305a. At this time, arms1305bof the toggle spring1305extending as opposite end portions of the same are positioned in a manner sandwiching the projecting arm1306bof the spur gear1306aand the projecting arm1304bof the barrier arm1304.

Thus, the central barrier102amade integral with the barrier arm1304and the gear-equipped member1306are connected to each other via the toggle spring1305as an elastic member, whereby a play in rotation and a phase displacement between the gears, which are inevitable to gear operation, are absorbed. Further, it is possible to preload the toggle spring1305in both the barrier open state and the barrier closed state, as described hereinafter.

Next, a description will be given of preloading of the toggle spring1305in the barrier closed state of the video camera.FIG. 17is a view of the upper barrier group102and the shaft-associated assembly portion including the upper barrier rotary shaft104ain the barrier closed state of the video camera before the toggle spring1305is preloaded.FIG. 18is a view of the upper barrier group102and the shaft including the upper barrier rotary shaft104ain the barrier closed state of the video camera when the toggle spring1305is preloaded.

When the gear-equipped member1306and the barrier arm1304driven in unison with the central barrier102arotate through an angle corresponding to a rotational angle required by the central barrier102a, the central barrier102ais brought into contact with a stopper1701formed on the lens barrel101, as shown inFIG. 17. This stops the driving of the central barrier102aand the barrier arm1304.

Thereafter, when the gear-equipped member1306is further rotated from theFIG. 17state in which the driving of the barrier arm1304is stopped, the winding of the toggle spring1305is tightened as shown inFIG. 18. This preloads the toggle spring1305in a barrier closing direction. Preloading of the toggle spring1305charging in a barrier opening direction is performed by reversing the operation. The lower barrier group103is identical in construction to the upper barrier group102, and therefore it is possible to generate a preloaded force of the toggle spring1305in both the barrier open state and the barrier closed state.

With the construction described hereinbefore, by driving one of the spur gears, it is possible to drive the four barrier blades (the central barriers102aand103aand the outer barriers102band103b) of the barrier section such that the barriers102aand102band the barriers103aand103bare rotated in the respective opposite directions, to thereby open or close the barrier section.

FIG. 19is a perspective view of a member which rotates about the lower barrier rotary shaft104b. InFIG. 19, a one-dot-chain line e indicates the axis of the lower barrier rotary shaft104b. In the present embodiment, the gear-equipped member1307which rotates about the lower barrier rotary shaft104bis formed as a double-geared wheel in which the spur gear1307aand a first worm wheel1307ewhich rotates about the same rotational axis as that of the spur gear1307aare integrated with each other. The member1307transmits a driving force from a motor2001as the drive source to the lower barrier group103having the lower barrier rotary shaft104binserted therein.

FIG. 20is a perspective view of a gear section of the motor as the drive source. The motor2001is electrically connected to a control circuit board, referred to hereinafter, via a flexible printed wiring board, not shown. When electric power is supplied via the flexible printed wiring board, the shaft of the motor2001performs rotation. The rotary shaft of the motor2001has a second worm gear2003mounted thereon.

The first worm wheel1307eis driven by a first worm gear2002. The first worm gear2002has a double-geared structure formed by a worm section2002aand a wheel section2002b. The first worm gear2002is driven by the second worm gear2003supported on the shaft of the motor2001.

In this case, the rotary shaft of the worm section2002aonly has to extend in a direction orthogonal to the rotary shaft of the first worm wheel1307e. Therefore, the motor2001can be connected to the first worm wheel1307ewhich rotates about the lower barrier rotary shaft104b, via a combination of at least two worm gears and a wheel, which makes it possible to enhance the degree of freedom in positioning the motor.

FIG. 21is a view showing the positional relationship between the gear-equipped member1307and the drive section holder106during assembly thereof.FIG. 22is a perspective view showing how the gear-equipped member1307is mounted to the drive section holder106. An arrow g inFIG. 22indicates an assembling direction.

As shown inFIG. 21, the first worm wheel1307ewhich rotates about the lower barrier rotary shaft104bhas an outer peripheral portion thereof formed with recesses1307g,1307h, and1307i. On the other hand, the drive section holder106has protrusions106a,106b, and106cformed on an inlet thereof at locations corresponding to the respective recesses1307g,1307h, and1307i. Each recess and each protrusion associated therewith are shaped such that they are associated with each other, like a key and a keyhole, in positional relation, when assembled. In the barrier mechanism of the present embodiment, the recesses and the protrusions fit to each other in the barrier closed state of the video camera.

Further, in the barrier mechanism of the present embodiment, the barrier section is mounted to the drive section holder106as follows: Components including the gear-equipped member1307are assembled to the sheet metal member1601having the lower barrier rotary shaft104binserted therethrough, whereby the components, the sheet metal member1601, and the lower barrier rotary shaft104bare formed into a unit. Then, the unit is mounted in the drive section holder106in the direction indicated by the arrow g inFIG. 22. At this time, since the recesses and the protrusions mentioned above are provided, it is possible to assemble the barrier section such that the gear-equipped member1307is in a phase corresponding to the barrier closed state in the inlet of the drive section holder106.

Further, in the barrier section of the present embodiment, first, the lower barrier group103is driven in accordance with rotation of the gear-equipped member1307driven by the motor2001as the drive source. On the other hand, the upper barrier group102, which is driven by the gear-equipped member1306for rotation, starts to operate at least simultaneously with driving of the lower barrier group103or with a delay of a time period corresponding to a play in rotation between the gears.

To cope with this problem, in the barrier section of the present embodiment, the central barrier103aof the lower barrier group103has a portion formed with a rabbet105which is superposed on an associated portion of the central barrier102aof the upper barrier group102in the optical axis direction, in the barrier closed state of the video camera. In particular, the rabbet105is formed such that the central barrier103aof the lower barrier group103is positioned in front (i.e. on an object side).

In the barrier section of the present embodiment, the lower barrier group103starts to operate earlier than the upper barrier group102as mentioned before. Therefore, by forming the rabbet105in the central barrier103aof the lower barrier group103such that it is positioned forward, whereby the rabbet is prevented from being undesirably caught.

FIG. 23is a view of shaft-associated assembly portions located on an opposite side of the lens barrel from the shaft-associated assembly portions including the above-mentioned barrier rotary shafts104. On the opposite side of the lens barrel101from the above-described barrier rotary shafts104, there are provided barrier rotary shafts204for supporting the barrier groups102and103in a manner capable of driving them. Each barrier rotary shaft204shares the same axis with the associated barrier rotary shaft104.

The barrier rotary shafts204are formed by an upper barrier rotary shaft204aand a lower barrier rotary shaft204b. Each of the upper central and outer barriers102aand102bhas an end thereof rotatably connected to the upper barrier rotary shaft204a. Further, the upper central barrier102ais formed with a guide hole205e, and a pin205ffor engagement with the guide hole205eprojects from the upper outer barrier102b. With this construction, the amount of rotation of the upper central barrier102awith respect to the upper outer barrier102bis restricted to a predetermined amount.

Similarly, each of the lower central and outer barriers103aand103bhas an end thereof rotatably connected to the lower barrier rotary shaft204b. Further, the lower central barrier103ais formed with a guide hole205g, and a pin205hfor engagement with the guide hole205gprojects from the lower outer barrier103b. With this construction, the amount of rotation of the lower central barrier103awith respect to the lower outer barrier103bis restricted to the predetermined amount.

The drive source is connected to the barrier rotary shafts104as described hereinbefore, but the barrier rotary shafts204on the opposite side from the barrier rotary shaft104are not connected to the drive source. Therefore, the upper barrier rotary shaft204aand the lower barrier rotary shaft204bonly serve to rotatably support the upper barrier group102and the lower barrier group103, respectively. It is to be understood that the barrier rotary shafts204may be also connected to the drive source, similarly to the barrier rotary shafts104, and the barrier rotary shafts104and204may be driven in synchronism with each other to perform the opening/closing operation of the barrier section.

Next, a description will be given of the operation of the video camera provided with the dome-shaped barrier section constructed as described above.FIG. 24is a transparent view of the internal construction of the video camera in the barrier open state thereof.FIG. 25is a transparent view of the internal construction of the video camera in the barrier closed state thereof. A video camera body2301contains the lens barrel101, an image display device2302, a control circuit board2303, and so forth. Disposed in front of the built-in lens is the dome-shaped barrier section which is capable of opening/closing the front of the lens by the mechanism described hereinbefore.

The video camera of the present embodiment converts an image of an object captured by the built-in lens barrel101into signal charges by an image pickup element (not shown) disposed at a focal position of an optical system, i.e. at a location rearward of the lens barrel101. The signal charges are converted into digital signals of luminance and color difference signals by an image processing circuit contained on the control circuit board2303, and the digital video data obtained by the conversion is stored in a memory on the control circuit board2303.

Then, the digital video data on the object, which is stored in the memory, is periodically read out following instructions from a control CPU on the control circuit board2303to be displayed in real time on a liquid crystal panel of the image display device2302. Further, the video data is compressed, as required, to be recorded in a recording device mounted on the control circuit board2303.

FIG. 26is a perspective view of the appearance of the video camera as viewed from the front thereof.FIG. 27is a perspective view of the appearance of the video camera as viewed from the rear thereof. A power button2601is provided on an upper surface of the video camera, and a trigger button2602is provided on a rear surface of the same. Whenever the power button2601is pressed, the power of the video camera is switched on or off. Further, whenever the trigger button2602is pressed, it is possible to start or terminate recording.

On the image display device2302, there is provided a shooting/reproduction switching button2603. Whenever the shooting/reproduction switching button2603is pressed, mode switching is performed between a shooting mode of the video camera and a reproduction mode for enabling check on picked-up video images.

The barrier section of the present embodiment can be opened/closed by the barrier mechanism described hereinbefore. Whenever the shooting/reproduction switching button2603is pressed after the power having been turned on by depression of the power button2601, an electric signal is sent from the control circuit board2303to the motor2001, and a barrier opening/closing operation is performed. Particularly, the video camera of the present embodiment is controlled such that the barrier section is held in its closed state in modes other than the shooting mode in the power-on state.

According to the image pickup apparatus of the present embodiment, with the configuration of the dome-shaped barrier section, it is not required to provide a rotary ring on a front side of the lens barrel. This increases the degree of freedom in layout, and also contributes to reduction of the size of a video camera.

Further, the upper barrier is driven about the upper barrier rotary shaft, and the lower barrier is driven about the lower barrier rotary shaft. This makes it possible to achieve space saving by reducing the thickness along the direction of the rotary shaft, which contributes to downsizing.

Further, by driving one of the upper and lower spur gears, the upper and lower barriers can be driven in respective directions opposite to each other.

Further, the respective rotational axes of the upper and lower spur gears coincide with the respective axes of the upper and lower barrier rotary shafts, respectively. Therefore, it is possible to realize an efficient barrier mechanism which is small in transmission loss of a driving force.

Further, as described hereinabove, the front surface of the central barrier is formed to be curved with the center of curvature located at a point on the optical axis. This makes it possible to prevent a recess from being formed in the central portion of the barrier section to thereby make the appearance of the barrier section look natural in the barrier closed state of the apparatus.

Therefore, a rabbet is formed in the central barrier of the lower barrier, which starts to be driven earlier than the central barrier of the upper barrier. This prevents the rabbet from being undesirably caught.

Further, the lower spur gear which is driven by the motor is connected to the lower barrier via a toggle spring. This makes it possible to absorb a play and a phase displacement between the gears, which are inevitable to gear operation. Further, it is possible to preload the toggle spring in both the barrier open state and the barrier closed state.

Further, as described hereinbefore, the barrier section is configured such that in the barrier open state, the central barrier is positioned in front of the outer barrier in a superposed state, and in the barrier closed state, an outer end of the central barrier and an inner end of the outer barrier are superposed one upon the other in front of the lens. Thus, even when a load is applied toward the central portion of the lens in the barrier closed state, it is possible to receive the load by the two barriers, so that the lens can be protected more securely.

It should be noted that the present invention is not limited to the arrangement of the above-described embodiment, but any suitable arrangement may be employed insofar as it can attain the functions of the embodiment.

For example, although in the above-described embodiment, both of the upper and lower barrier groups are configured such that the center of rotation of the spur gear thereof coincides with the axis of the barrier rotary shaft, only one of the upper and lower barrier groups may be configured such that the center of rotation of the spur gear thereof coincides with the axis of the barrier rotary shaft.

Further, although in the above-described embodiment, the barrier groups vertically open and close when the video camera is set in its normal position, this is not limitative, but the present invention can also be applied to a construction in which the barrier groups open and close laterally, for example.

Although in the above-described embodiment, the image pickup apparatus is described by taking the video camera as an example, the present invention is also applicable to a film camera, a digital video camera, a digital SLR (single-lens reflex camera), etc. Further, the present invention can be applied not only to the above-mentioned image pickup apparatus, but also to various kinds of optical apparatuses including a monitoring apparatus, a telescope, and a microscope.

Further, in the above-described embodiment, the lens barrel is integrally built in the video camera body to form the video camera, but the lens barrel may be included in a lens device that can be removably attached to the body of an optical apparatus, such as an image pickup apparatus.

This application claims the benefit of Japanese Patent Application No. 2008-327912, filed Dec. 24, 2008, which is hereby incorporated by reference herein in its entirety.