Patent Description:
Conventionally, there has been known an image pickup apparatus equipped with a filter switching mechanism for inserting and removing an infrared blocking filter (infrared cutting filter), an ND filter, and the like into and from an optical path. For example, Japanese Patent Laid-Open <CIT> discloses a filter switching mechanism for inserting and removing a filter frame that holds a filter into and from an optical path by an actuator having a lever.

However, the filter switching mechanism disclosed in <CIT> has a weak holding force for holding (locking) the filter frame at a predetermined position, and the filter may be unintentionally switched when the vibration or impact is applied. On the other hand, if the torque of the actuator is made larger to increase the holding force, the actuator and finally the image pickup apparatus become larger. Any dedicated lock unit for locking the filter frame at the predetermined position will also increase the size of the image pickup apparatus. <CIT> discloses a filter switching device according to the preamble of claim <NUM>. <CIT> discloses further prior art.

The object of the present invention is to overcome the above-mentioned shortcomings in the prior art. The object is solved by an optical apparatus according to claim <NUM>. The compact optical apparatus can move and stably hold (or lock) an optical element.

Further advantageous embodiments are disclosed in the dependent claims.

Referring now to the accompanying drawings, a detailed description will be given of embodiments according to the present invention.

<FIG> is a perspective view of an image pickup apparatus <NUM> as a surveillance camera apparatus according to one embodiment of the present invention. The image pickup apparatus (optical apparatus) <NUM> includes a camera unit (optical apparatus) <NUM>. <FIG> is a perspective view of the camera unit <NUM>, and <FIG> is a sectional view along an optical axis OA of the camera unit <NUM> illustrated in <FIG>. The left side (object side) in <FIG> is called a front side, and the right side is called a rear side. The camera unit <NUM> has a front holder <NUM> and a rear holder <NUM> and has an approximately spherical shape. The camera unit <NUM> has a lens barrel unit (lens or optical apparatus) <NUM>. The lens barrel unit <NUM> is sandwiched and fixed between the front holder <NUM> and the rear holder <NUM>. <FIG> is an exploded perspective view of the lens barrel unit <NUM>.

The lens barrel unit <NUM> includes a lens unit <NUM>, a fixed lens barrel <NUM>, dustproof rubber <NUM>, an image sensor substrate <NUM>, a filter base <NUM>, a filter holding frame <NUM>, an actuator <NUM>, and a gear cover <NUM>, as illustrated in <FIG>.

The lens unit <NUM> holds an image pickup optical system that forms an optical image of an object and includes one or more lenses. One or more lenses may be movable in the optical axis direction (X-axis direction) or unmovable (fixed). The lens may include a focus lens for focusing and a zoom lens (magnification varying lens) for changing a focal length. As illustrated in <FIG>, the lens unit <NUM> has a threaded groove formed on a surface of an attachment portion 11a, and a threaded groove is also formed on an inner surface of an attachment portion 12b of the fixed lens barrel <NUM>. The lens unit <NUM> is fixed into the fixed lens barrel <NUM> through an engagement between the mounting portions 11a and 12b (by screwing the attachment portion 11a into the attachment portion 12b).

The dustproof rubber <NUM> is engaged with the fixed lens barrel <NUM> to provide the dustproof and antivibration. The image sensor substrate <NUM> is a substrate mounted with an image sensor <NUM>, is fixed onto the fixed lens barrel <NUM>, and the dustproof rubber <NUM> is sandwiched between the fixed lens barrel <NUM> and the image sensor substrate <NUM>. The image sensor <NUM> photoelectrically converts an optical image formed via the image pickup optical system, and includes a photoelectric conversion element, such as a CCD and a CMOS.

The filter holding frame <NUM> has a rack 17a on a side surface orthogonal to the Z-axis direction, and holds an infrared cutting filter (optical element) <NUM> for blocking infrared rays and a dummy glass <NUM>. The filter holding frame <NUM> is held by the filter base <NUM> movably in a direction orthogonal to the optical axis of the lens unit <NUM> (Y-axis direction), and the filter base <NUM> is inserted into the Y-axis direction from an opening 12a provided on a side surface of the fixed lens barrel <NUM> and held by the fixed lens barrel <NUM>.

The filter holding frame <NUM> is driven by a driver. More specifically, the driver drives the filter holding frame <NUM> so that the infrared cutting filter <NUM> moves between a position on the optical axis of the image pickup optical system and a position retracted from the optical axis OA. In <FIG>, the infrared cutting filter <NUM> is located on the optical axis. In <FIG>, the dummy glass <NUM> is located on the optical axis. The configuration of the driver will be described later.

The actuator <NUM>, such as a motor, serving as a driving source drives the filter holding frame <NUM> in a direction orthogonal to the optical axis, and is connected to a flexible printed circuit board <NUM>. Reference numeral <NUM> denotes a photointerrupter for detecting the position of the filter holding frame <NUM> in the direction orthogonal to the optical axis, which is mounted on the flexible printed circuit board <NUM>. The gear cover <NUM> holds the actuator <NUM> and rotatably holds the intermediate gear unit <NUM> between the gear cover <NUM> and the fixed lens barrel <NUM>.

The driver includes an actuator <NUM>, a worm (cylindrical worm) <NUM> fixed onto a rotation shaft 20a (<FIG> described later), and the intermediate gear unit <NUM>. The intermediate gear unit <NUM> has a worm wheel (bevel gear) 24a and a pinion (spur gear) 24b, which have a coaxial rotation shaft 24c (<FIG>). Due to the coaxial structure, the image pickup apparatus can be made compact. The worm <NUM> is a screw-shaped gear with a small number of teeth, which is rotated integrally with the rotation shaft 20a by the rotor of the actuator <NUM>. The worm wheel 24a is engaged with the worm <NUM> and forms a worm gear with the worm <NUM>. The pinion 24b is integrated with the worm wheel 24a, and rotates as the worm wheel 24a rotates. The pinion 24b is engaged with a rack 17a formed on the filter holding frame <NUM>.

Due to the above configuration, the driving force of the actuator <NUM> is transmitted to the filter holding frame <NUM> via the worm <NUM>, the intermediate gear unit <NUM>, and the rack 17a. <CIT> uses a lever as a power transmission mechanism to drive the filter holding frame, but this embodiment uses the worm gear including the worm <NUM> and the worm wheel 24a as the power transmission mechanism. The worm gear can suppress the transmission of the rotation from the worm wheel side to the worm side by adjusting the advance (or fast) angle of the groove of the worm <NUM> (self-lock function). In other words, by setting the advance angle of the worm <NUM> to a predetermined value, it becomes possible to increase a load P necessary to rotate the worm <NUM> from the filter holding frame <NUM> side or to perform the self-lock. As a result, by setting the load P larger than the load in the filter inserting/removing direction applied to the filter holding frame <NUM> when the impact or vibration is applied, it is possible to prevent the filter from being unintentionally switched. Since the power transmission mechanism serves as the lock mechanism, the optical apparatus can be made smaller than that including a new lock unit.

Referring now to <FIG>, a description will be given of the filter switching operation according to this embodiment. When a driving signal is input to the actuator <NUM> via unillustrated electric wiring connected to the image sensor substrate <NUM>, the rotor of the actuator <NUM> rotates around the rotation axis. As the rotor of the actuator <NUM> rotates, the worm <NUM> fixed to the rotating shaft 20a and the worm wheel 24a (the intermediate gear unit <NUM>) engaged with it rotate. When the intermediate gear unit <NUM> rotates, the filter holding frame <NUM> moves in the direction orthogonal to the optical axis via the pinion 24b and the rack 17a engaged with the pinion 24b. The driving signal is input into the actuator <NUM> so as to stop when the filter holding frame <NUM> moves by a predetermined movement amount.

<FIG> illustrates that the infrared cutting filter <NUM> is inserted into the optical path (optical axis OA), and <FIG> illustrates that the dummy glass <NUM> is inserted into the optical path. The infrared cutting filter <NUM> and the dummy glass <NUM> are selectively inserted into the optical path by driving the filter holding frame <NUM> in the direction orthogonal to the optical axis indicated by an arrow in <FIG>.

Referring now to <FIG>, a description will be given of an arrangement of the filter holding frame <NUM>, the worm <NUM>, and the intermediate gear unit <NUM>. <FIG> is a perspective view showing the arrangement of the filter holding frame <NUM>, the worm <NUM>, and the intermediate gear unit <NUM>.

A direction of a rotation axis 23A of the worm <NUM> fixed onto the actuator <NUM> is the same as (parallel to) the Y-axis direction which is the driving direction of the filter holding frame <NUM>. Thereby, the image pickup apparatus <NUM> can be made compact. A rotation shaft 24c of the intermediate gear unit <NUM> is approximately the same direction as the optical axis direction (X-axis direction). The intermediate gear unit <NUM> is located farther from the optical axis OA than the rack 17a, and the rotation shaft 23A is located closer to the optical axis OA than the rotation shaft 24A. Due to this arrangement, the filter holding frame <NUM> and its driver can be housed in a small range viewed from the optical axis direction, and the camera unit <NUM> and thus the image pickup apparatus <NUM> can be reduced in size.

<FIG> is a front view of the camera unit <NUM> excluding the front holder <NUM> and the gear cover <NUM> viewed from the object side in the optical axis direction. Since the camera unit <NUM> according to this embodiment has the above compact configuration, as illustrated in <FIG>, the gear unit <NUM>, the actuator <NUM>, and the worm <NUM> are housed in an inner circumference circle 4A of the rear holder <NUM> determined by the length of the filter base <NUM> in the Y-axis direction. Thus, the filter can be stably held with a small configuration even when the vibration or impact is applied.

This embodiment disposes the rotation shaft 23A of the downsized worm <NUM> between the optical axis OA and the rotation shaft 24A of the intermediate gear unit <NUM>, but the present invention is not limited to this embodiment. For example, if the camera unit <NUM> does not have an approximately spherical shape or the like and the camera unit <NUM> may partially protrude, the rotation axis 24A of the intermediate gear unit <NUM> may be disposed between the optical axis OA and the rotation axis 23A of the worm <NUM>.

As described above, this embodiment can provide a compact optical apparatus that can prevent the filter switching mechanism for inserting and removing the filter into and from the optical path from unintentionally switching the filter when the impact or vibration is applied. The optical apparatus according to the present invention includes a lens apparatus such as an interchangeable lens apparatus, an image pickup apparatus such as a surveillance camera and a digital camera, and other optical apparatuses such as an extender. In addition, the optical element is not particularly limited, and may include an optical filter that transmits light of a specific wavelength, various glasses, lenses, and the like. In the worm gear, the worm and the bevel gear (worm wheel) may be in point or line contact. The worm may be a cylindrical worm or a drum-shaped worm. The moving direction of the optical element is not limited, and may include components in the optical axis direction and another direction.

The present invention is not limited to the configuration illustrated in <FIG>. In <FIG>, the worm wheel 24a is provided on the right side (in the -Z axis direction) of the worm <NUM>, but may be provided below the worm <NUM> (in the X-axis direction). In this case, the intermediate gear unit <NUM> is rotated by <NUM>° to the left in <FIG>. In this case, the rack 17a faces the side (in the -X axis direction) of the filter holding frame <NUM> opposite to the actuator <NUM>. As described above, in <FIG>, the optical axis OA and the rotation axis 24c of the pinion 24b are parallel to each other, and when viewed from the optical axis direction, the rotation axis 23A of the worm <NUM> is disposed between them. On the other hand, in the above modification, the rotation axis 24c of the pinion 24b is orthogonal to the optical axis OA and the rotation axis 23A of the worm <NUM>, and the rotation axis 23A of the worm <NUM> is located between the optical axis OA and the center of the pinion 24b (the center in the Z-axis direction and the Y-axis direction).

As described above, the optical apparatus (image pickup apparatus <NUM>, camera unit <NUM>, and lens barrel unit <NUM>) according to this embodiment holds the optical element (infrared cutting filter <NUM>) and includes the filter holding frame <NUM> having the rack 17a, and the driver for driving the holding frame. The driver includes the worm <NUM> rotated by the actuator <NUM>, the worm wheel 24a that forms the worm gear together with the worm <NUM>, and the pinion 24c that rotates with the rotation of the worm wheel 24a and is engaged with the rack 17a. The optical apparatus according to this embodiment can stably hold (lock) the optical element at the predetermined position even when there is an impact etc. by using the self-locking function of the worm gear, thereby preventing the optical element from unintentionally moving.

Claim 1:
An optical apparatus (<NUM>, <NUM>, <NUM>) comprising:
an optical system configured to form an optical image of an object;
a holding frame (<NUM>) configured to hold an optical element (<NUM>) and including a rack (17a); and
a driving means configured to drive the holding frame (<NUM>) such that the optical element (<NUM>) moves between a position on an optical axis of the optical system and a position retracted from the optical axis,
wherein the driving means includes:
a worm (<NUM>) configured to be rotated by an actuator (<NUM>);
a worm wheel (24a) configured to engage with the worm (<NUM>); and
a pinion (24b) configured to be integrally formed with the worm wheel (24a) and to rotate with a rotation of the worm wheel (24a) and engaged with the rack (17a), characterized in that
a rotation axis of the worm (<NUM>) is disposed between the optical axis and a center of the pinion (24b) when viewed from an optical axis direction.