JP2005070800A - Lens barrel and optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate unnecessary static on a last lens group by a photographer when a lens whose last lens group is movable in an optical axis direction (for example, a general four-group zoom in video) is used as an interchangeable lens. To obtain a lens barrel that does not apply pressure.
A lens barrel detachable from a camera body, the lens barrel being provided on a fixed tube, a last lens group housed in the fixed tube, a step motor, and an output shaft of the step motor. In addition, a second screw portion that is provided on a frame that holds the first screw portion and the rearmost lens group and that engages with the first screw portion is used to drive the rearmost lens group in the optical axis direction. Drive means and a transparent plate disposed on the camera body side of the rearmost lens group and fixed to the fixed cylinder.
[Selection] Figure 1

Description

  The present invention relates to a lens barrel that can be removed and replaced with respect to an optical device such as a video camera, a still camera, and a surveillance camera, and an optical device using the lens barrel.

  Conventionally, as a zoom lens used in this type of optical apparatus, a lens group behind the variator lens is used instead of the so-called front lens focus lens in which the front lens group, which has been mainstream until now, is used as a focus lens. So-called inner focus or rear focus for performing focusing is common. By adopting this inner focus lens, it is possible to shoot at a closer distance than the front lens focus lens, and it is easy to configure to focus continuously from just before the lens to an infinite distance especially on the wide side.

  Various lens types of the inner focus lens are known, but FIG. 7 has a four-group configuration, and shows a configuration in which the rearmost lens group is used for focusing. In FIG. 7, 111 is a fixed front lens group, 112 is a variator lens group, 113 is a fixed lens group, and 114 is a focusing (compensation) lens group.

  133 is a guide rod for preventing rotation, 134 is a feed rod of the variator lens group 112, 135 is a fixed barrel, 136 is an aperture unit (here, inserted perpendicular to the paper surface), and 137 is a focus motor. A step motor 138 is an output shaft of the step motor 137, and a male screw 138a for moving the focusing lens group 114 is processed. Reference numeral 139 denotes an internal thread forming portion that meshes with the external thread 138a, and is integrated with the moving frame 140 of the lens 114.

  141, 142 are guide rods for the lens 114, 143 is a rear plate for positioning and pressing the guide rods 141, 142, 144 is a relay holder, 145 is a zoom motor, 146 is a reduction gear unit of the zoom motor 145, 147, 148 Is an interlocking gear, and the interlocking gear 148 is fixed to a zoom feed bar 134.

  Next, the operation will be described. When the step motor 137 is driven, the focus lens 114 moves in the optical axis direction by screw feeding. When the zoom motor 145 is driven, the screw shaft 134 rotates via the interlocking gears 147 and 148, and the variator 2 held by the lens frame 112a screwed with the screw shaft 134 moves in the optical axis direction.

  FIG. 8 shows the positional relationship between the variator lens and the focus lens in the lens barrel configured as described above according to several subject distances. Here, as an example, for each subject of infinite, 2 m, 1 m, 80 cm, and 0 cm, The in-focus position relationship was shown. In this way, in the case of inner focus, the positional relationship between the variator lens and the focus lens differs depending on the subject distance, and therefore the lens group cannot be interlocked with a mechanical structure like the cam ring of the front lens focus lens. Therefore, in the lens barrel having the structure as shown in FIG. 7, blurring occurs only by simply driving the zoom motor 145.

  Therefore, it is essential to optimally control the lens positional relationship as shown in FIG. 8 according to the subject distance. As an example of such control, the present applicant has proposed a method of tracing the locus of the positional relationship between the variator lens and the focus lens according to the subject distance (Patent Documents 1 and 2).

  FIG. 9 shows a block configuration diagram for carrying out the locus tracing method, and reference numerals 111 to 114 denote the same lens groups as those shown in FIG. The position of the variator lens group 112 is detected by the zoom encoder 149. Here, as a type of encoder, for example, a volume encoder configured to slide a brush integrally attached to a variator moving ring on a substrate on which a resistance pattern is printed can be considered.

  Reference numeral 150 denotes an aperture encoder that detects an aperture value. For example, a hall element output provided in an aperture meter is used. Reference numeral 151 denotes a photographing element such as a CCD, 152 denotes a camera processing circuit, and the Y signal is taken into the AF circuit 153. The AF circuit 153 discriminates in-focus and out-of-focus, and in the case of out-of-focus, it is determined whether it is a mae pin or an at-pin, and the degree of out-of-focus. These results are captured by the CPU 154.

  A power-on reset circuit 155 performs various reset operations when the power is turned on. A zoom operation circuit 156 notifies the CPU 154 of the contents when the zoom switch 157 is operated by the operator. Reference numerals 158 to 160 denote memory portions of the trajectory data shown in FIG. 14, which include direction data 158, velocity data 159, and boundary data 160.

  161 is a zoom motor driver, and 162 is a step motor driver. The number of input pulses supplied from the step motor driver 162 to the step motor 137 is continuously counted by the CPU 154, and this count number is an encoder for the absolute position of the focus lens. It is used as.

  With this configuration, the variator lens position and the focus lens position are determined by the zoom encoder 149 and the number of step motor input pulses, respectively, so that one point on the map shown in FIG. 8 is determined.

  On the other hand, the map shown in FIG. 8 is divided by the boundary data 160 into small areas I, II, III,. Here, the shaded area is a region where the lens is prohibited from being arranged. When one point on the map is determined in this way, it is possible to determine the region to which the point belongs in the small region.

  In the speed data and the direction data, the rotational speed direction of the step motor 137 obtained from the trajectory passing through the center of each area is stored for each area. For example, in the example of FIG. 10, the horizontal axis (variator lens position) is divided into 10 zones. If the speed of the zoom motor 145 is set so as to move from the tele end to the wide end in 10 seconds, the passing time of one zone in the zoom direction is 1 second.

  FIG. 11 is an enlarged view of the block III in FIG. 10. A trajectory 164 passes through the center of the block, a trajectory 165 passes through the lower left, and a trajectory 166 passes through the upper right, and each has a slightly different inclination. Here, if the central locus 164 moves at a speed of xmm / 1 sec, it can follow the locus with almost no error.

  When the speed thus obtained is referred to as an area representative speed, this value is stored in the speed memory in accordance with the number of small areas. When this speed is indicated by an arrow 168, the stepping motor speed is set by finely adjusting the representative speed as indicated by arrows 167 and 169 according to the detection result of the automatic focus adjustment device. Further, the direction data is stored in the code data because the rotation direction of the step motor 137 varies depending on the area even in the same tele-to-wide (wide-to-tele) zoom.

  As described above, using the step motor speed obtained by correcting the area representative speed based on the detection result of the automatic focusing device with respect to the area representative speed obtained from the variator lens position and the focus lens position, the zoom motor If the position of the focus lens is controlled by driving the step motor 137 during driving, the focus can be maintained even during zooming even with the inner focus lens.

  Here, in addition to the representative speed indicated by the arrow 168 in FIG. 11, speeds such as arrows 167 and 169 are stored for each block, and a method of selecting three speeds according to the detection result of the automatic focus adjustment device is also presented. Has been.

  In addition to storing the speed as described above, the trajectory passing through one point on the map determined by the current variator lens position and step motor position is calculated, and the method of tracing the trajectory and several trajectories For example, a method of storing a memory as a focus lens position corresponding to the position of the variator lens is used.

  In Patent Document 2, the position of the focus lens with respect to a plurality of variator positions between the wide end and the tele end is stored for a plurality of subject distances, and at the start of zooming, the variator position and the focus lens position at that time are within the map. From that point, at the same focal length, the majepin side is interpolated from the closest stored data and the stored data closest to the atpin side, and each focal length (variator lens position) The method of calculating the focus lens position at) is shown.

FIG. 12 shows a locus near the zoom telephoto end. In Patent Document 2, as stored data, the positions of variator lens positions V _n (tele end), V _n−1 , V _n−2 , and V _{n−3 on} the trajectory indicated by 1 (for example, ∞ focus trajectory). For, information of rr ₁ , rr ₄ , rr ₇ , rr ₉ is stored as the focus lens position. That is, the trajectory passing through the points P ₁ , P ₄ , P ₇ , and P ₁₀ in the map is stored as the ∞ trajectory.

Similarly Vn (telephoto _end), with respect to the position of the _{V n-1, V n-} 2, V n-3, as a focus lens _position, information _{rr 2, rr 5, rr 8} , rr 11 is indicated by II Stored as a trajectory (for example, a focus trajectory of 10 m). Of course, this data is actually created over the entire zoom range from the tele end to the wide end.

Here, when zooming from (V _n , rr), that is, the point P in the map, the closest stored data on the Maepin side at the same variator position from this point, that is, the data on the locus II, and also closest to the atopin side data, i.e., based on data of the locus I, the point _{P a,} P B, determined by interpolation computing the _{P C.} The locus during zooming is determined by determining the focus lens positions with respect to the respective focal lengths V ₀ (wide end), V ₁ V ₂ ... V _n−1 V _n (tele end) during zooming. To do.

Since this is an interpolation operation, the ratio of the distance between the points P ₁ and P and the distance between the points P ₂ and P is, for example, the distance between the points P _A and P ₄ and the points P _A and P _5. It becomes equal to the ratio of the distance between.

  Such a memory relating to speed or a memory relating to position is naturally made based on the optical design value when the manufacturing error is zero.

  The embodiment of the present invention described below is an inner focus lens having a convex / concave / convex / four-group configuration as in this example, and the second lens is a variator lens and the fourth lens is a focus lens. Other configuration examples (for example, the configurations shown in FIGS. 5, 7, and 8 in Patent Document 3) can also be applied.

  In the illustrated example, a DC motor with a gear head is used as the zoom actuator, but a step motor may be used in the same manner as the focus lens. Alternatively, a method may be adopted in which the absolute position of the lens group is known by counting the number of input pulses based on the reset position as in the focus without using a volume as a variator encoder.

In addition, a method using a photo interrupter as a reference position when using such a focus motor, a method using a voice coil type as an actuator of each movable lens group, a method using an ultrasonic motor, etc. are also known. ing.
JP-A-1-280709 JP-A-1-321416 JP-A-3-27011

  Since the conventional lens barrel is configured as described above, when this lens is used as a so-called interchangeable lens that can be exchanged for the camera body, the movable lens group at the end of the removed lens (for example, lens cleaning) It may be easy to touch (including the case of the case of) or a case where a static pressure load is applied depending on the handling.

  In such a state, for example, in the configuration in which the last lens group is moved using the step motor described above, the interlocking mechanism portion of the screw feed portion is damaged, or the interlocking engagement state becomes inappropriate. Or, due to the deformation accompanying the static pressure load of the mechanism that holds the last lens group, this lens group is displaced or tilted from the normal position on the optical axis, so that normal imaging performance can be maintained. Absent. Another problem is that dust, water droplets, etc. may inadvertently enter the lens barrel and cause damage to each mechanism.

  In the present invention, when a lens whose last lens group is movable in the direction of the optical axis is used as an interchangeable lens, the photographer prevents unnecessary static pressure from being applied to the last lens group and damages each mechanism. It is an object of the present invention to provide a lens barrel that can be prevented and an optical apparatus having the same.

  The lens barrel according to the first aspect of the present invention is a lens barrel that is removable from the camera body, and includes a fixed tube, a last lens group housed in the fixed tube, a step motor, and the step. A first screw portion provided on the output shaft of the motor and a second screw portion provided on a frame that holds the last lens group and meshing with the first screw portion, thereby using the second screw portion. And a transparent plate disposed on the camera body side of the rearmost lens group and fixed to the fixed cylinder.

  A lens barrel according to a second aspect of the present invention is a lens barrel that is removable from the camera body, and includes a fixed barrel, a rearmost lens group housed in the fixed barrel, and a rearmost lens. Drive means for driving the group in the direction of the optical axis; and a transparent plate disposed on the camera body side from the rearmost lens group and fixed to the fixed cylinder, wherein the transparent plate is not a low-pass filter. It is said.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the electronic device further comprises an electrical contact for receiving a signal from the camera body when the camera is attached to the camera body, and the driving means is provided via the electrical contact. Then, based on a signal received from the camera body, the last lens group is driven to perform focus adjustment.

  According to a fourth aspect of the present invention, there is provided the variator lens group according to any one of the first to third aspects, wherein the variator lens group is housed in the fixed cylinder and disposed closer to the subject side than the rearmost lens group, and the variator lens group. And a second driving unit that performs zooming by driving the lens in the optical axis direction, and the driving unit drives the last lens group in accordance with zooming to adjust the focus. .

  A fifth aspect of the invention is characterized in that, in the invention of any one of the first to fourth aspects, the transparent plate is an ND filter.

  The invention of claim 6 is the invention of any one of claims 1 to 5, further comprising a pole parallel to the optical axis accommodated in the fixed cylinder, wherein the pole moves the last lens group. It is characterized by guiding.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects, the camera body is a video camera having a color separation prism and three CCDs.

  An optical apparatus according to an eighth aspect of the invention is characterized by using the lens barrel according to any one of the first to seventh aspects.

  According to the present invention, the transparent lens is further arranged on the camera body side of the rearmost lens group of the lens barrel exchangeable with the camera body, and therefore when the lens barrel is removed from the camera body. The last movable lens group is not exposed, and no other object touches the lens, and no static pressure load is applied. Therefore, there is an effect that the lens or the lens driving mechanism can be damaged, or dust and water droplets can be prevented from entering the lens barrel.

  FIG. 1 is a cross-sectional view showing a state in which the lens barrel of the present invention is mounted on the camera side as an optical device, and FIG. 2 is an end view of the lens barrel before mounting. The camera side is assumed to be a so-called 3CCD video camera that has three prisms and obtains an image by separating the colors into, for example, three colors of RGB, but may be another camera.

  On the camera side, a color separation prism 302, a base member 301 that holds the color separation prism 302 and mounts a mount component, and a mount member 306 for an interchangeable lens (here, a bayonet mount is assumed. (It does not matter) CCDs 303 to 305 are provided. In addition, an electrical contact 307 for performing various communications between the microcomputer on the camera side and the microcomputer on the lens side is provided for executing the autofocus function and the auto iris function.

  On the other hand, there are four lens groups of lenses 311 to 314 as the last movable lens group on the lens side. This lens group is configured to be movable in the optical axis direction, and is fixed integrally to the moving cylinder 315. The moving cylinder 315 has a sleeve portion 316 integrally, and is movable in the optical axis direction while being positioned with respect to, for example, the metallic pole part 400. The actuator is not shown here, but this lens group can be moved in the optical axis direction by various actuators as described in the prior art.

  The movable lens groups 311 to 314 are configured in a fixed cylinder (not shown), but a lens-side mount component 308 constituting a bayonet mount is provided at the rear end of the fixed cylinder, The lens can be exchanged between them, and the position is correctly determined when the lens is mounted.

  Reference numeral 318 denotes a lens side contact that contacts the camera side contact 307 for communication between the lens side and the camera side.

  A feature of this embodiment is that a glass holder 309 having a flat glass 310 as a transparent plate is integrally fixed to the lens side mount component 308 from the rear with a claw portion 317. When the lens side is removed from the camera side due to the configuration, the flat glass 310 can be touched by the operator as shown in FIG. 2, but this prevents the movable lens group from being touched and avoids the aforementioned problems. Can do.

  FIG. 3 shows the second embodiment. Instead of adopting the structure of the first embodiment shown in FIG. 1 in which the glass holder 309 is hooked by the claw portion, the glass holder 309 is attached to the fixing ring 319 via the mounting part 308 with a screw 320. It is tightened and fixed using.

  In the first embodiment, a convex portion 308a is provided at the rear end of the mount component 308, and this position is protruded rearward from the rear end surface 331 of the glass holder, so that the lens barrel removed from the camera side is mounted on the mount component 308. In such a case, it is configured to avoid applying a load to the glass holder as much as possible, but in Example 2, since it is fixed with screws, it can be expected to ensure strength than the claw method of FIG. The fixing ring 319 can be a receiving surface when the lens barrel is set up. Therefore, it is necessary to measure the strength of the fixing ring 319 by using, for example, metal.

  FIG. 4 is a block diagram showing an example of an interchangeable lens system showing Embodiment 3 of the present invention. Here, as in the case described above, an example of a zoom lens having a four-group configuration of convex and concave in order from the subject side that is frequently used in video cameras will be described. However, other lens configurations may be used.

  The light from the subject is fixed in the first lens group 111, the variator lens group 112, which is the second lens group for zooming, the aperture 136, the fixed third lens 113, and the focus adjustment function and variable. The red component in the three primary colors passes through the focus lens group 114, which is a fourth lens group that also has a competition mechanism that corrects the movement of the focal plane due to doubling, on the image sensors 303 to 305 such as CCDs, respectively. Imaged.

  Each image on each image sensor is photoelectrically converted and amplified to an optimum level by amplifiers 405, 406, and 407, then input to the camera signal processing circuit 152, converted into a standard television signal, and automatically focused. Information on sliding contact and automatic exposure adjustment is read as data by the main body microcomputer 409.

  The information read by the main body microcomputer 409 is transferred to the lens microcomputer 410 through the camera side contact 307 and the lens side contact 318 together with information (not shown) of each operation switch such as a zoom switch on the camera side. The The lens microcomputer 410 executes a motor control program control program based on various types of information for automatic focus adjustment sent from the main body microcomputer 409, drives the motor 137 with the motor driver 162, and moves the focus lens group 114 in the optical axis direction. Move to to focus.

  Further, the lens microcomputer 410 maintains the focus in accordance with the subject distance stored in the lens microcomputer 410 when the operation is required also according to the information on the state of the zoom switch sent from the main body microcomputer 409. Based on the position data of the variator lens group 112 and the focus lens group 114 for this purpose, a signal is given to the zoom motor driver 161 and the focus motor driver 162 so as to perform an operation of maintaining the focus surface during zooming.

  The zoom motor driver 161 and the focus motor driver 162 drive the zoom motor 145 and the focus motor 137 based on signals from the lens microcomputer 410, respectively, and move the variator lens group 112 and the focus lens group 114 in the optical axis direction. Zoom without moving the focus position.

  Further, the lens microcomputer 410 gives a signal for giving an appropriate exposure to the iris driver 414 based on each information related to exposure adjustment sent from the main body microcomputer 409 and information from the encoder 163 for detecting the aperture state. The iris driver 414 drives the aperture actuator 413 based on the signal from the lens microcomputer 410 to limit the aperture 136 to a state that provides appropriate exposure.

  In this manner, the camera body 419 is provided by providing the microcomputer 409 and the lens microcomputer 410 on the camera side, and the contacts 307 and 318 on both the camera side and the lens side so as to be detachable from the communication paths of the two microcomputers. On the other hand, the lens unit 418 can be attached and detached, and at the same time, automatic focus adjustment, automatic exposure adjustment, and zoom operation similar to those of a general video camera in which a lens and a camera are integrated can be performed without any problems.

  FIG. 5 is a cross-sectional view showing a state in which the flat glass 310 is mounted on the lens barrel showing the fourth embodiment. The glass holder 309 has a female screw 309a attached to the accessory, and the flat glass 310 is screwed onto the female screw 309a. Is attached to a filter frame 321 having a male threaded portion 321a on its outer periphery.

  Here, the flat glass 310 may have various functions such as an ND filter, a color temperature conversion filter, a filter having an effect of obtaining a soft image, a low-pass filter, and the flat glass is formed by the screw portions 309a and 321a. The filter as 310 can be replaced, and can be used properly according to circumstances.

  FIG. 6 shows an example of a variable density ND filter 350 used in place of the flat glass 310. In FIG. 6, 322 and 326 are glass plates, and 323 and 325 are transparent electrodes. Reference numeral 324 denotes a coloring layer, and the layers are sequentially stacked. In this configuration, when a voltage 327 is applied between the transparent electrodes 323 and 325, a variable density ND filter 350 that changes the color of the color developing layer 324 is configured.

  The ND filter 330 may be attached according to either the first or second embodiment.

  As described above, according to each embodiment, in addition to the above-described effect, the transparent plate can be removed, and there is an effect that it can be replaced with an ND filter, a color temperature variable filter, or the like.

  In addition, according to each embodiment, since the ND filter having a variable density is arranged as the transparent plate, there is an effect that the amount of transmitted light can be adjusted.

  In addition, according to each embodiment, since the last lens unit is configured to be movable in the optical axis direction by the guide pole, there is an effect that the lens unit can be moved smoothly.

  In addition, according to each of the embodiments, since it is configured by a convex-concave convex four-group lens, there is an effect that can be implemented for a video lens.

  In addition, according to each of the embodiments, the rearmost position of the mount is configured to protrude from the optical element such as a transparent plate to the camera side. Therefore, even if the lens barrel removed from the camera side is placed with the mount facing down, the optical There is an effect that no inconvenient weight is applied to the element.

  In addition, according to each embodiment, there is an effect that can be implemented for a video camera. In addition, since the lens barrel is used, there is an effect that stable photographing can always be performed.

The longitudinal cross-sectional view which shows the state which mounted | wore with the lens barrel by Example 1 of invention on the camera side Sectional view of the lens barrel before mounting on the camera side FIG. 5 is a longitudinal sectional view showing a state where a lens barrel according to a second embodiment of the present invention is mounted on the camera side. Block diagram showing a replaceable lens system according to Embodiment 3 of the present invention. FIG. 5 is a longitudinal sectional view in which a flat glass is mounted on a lens barrel according to Embodiment 4 of the present invention. Structure diagram of variable ND device according to embodiment 5 of the present invention A longitudinal sectional view showing a conventional lens barrel Figure showing the positional relationship between the variator lens and focus lens in the lens barrel according to the subject distance The block block diagram which implements the locus tracing method of the positional relationship of FIG. Fig. 8 is a diagram divided into small areas One enlarged view of the small region of FIG. Trajectory map near the zoom telephoto end

Explanation of symbols

310 Flat glass (transparent plate)
311 to 314 Movable lens group (last lens group)
330 Convex (end of mount part)
400 Pole parts (pole)

Claims (8)

A lens barrel that is detachable from the camera body, the fixed barrel, the last lens group housed in the fixed barrel, a step motor, and a first motor provided on an output shaft of the step motor Drive means for driving the last lens group in the direction of the optical axis using a second screw part provided on a frame for holding the screw part and the last lens group, and meshing with the first screw part; A lens barrel comprising: a transparent plate disposed on the camera body side of the rearmost lens group and fixed to the fixed barrel. A lens barrel detachable from the camera body, a fixed tube, a last lens group housed in the fixed tube, and a driving means for driving the last lens group in an optical axis direction; And a transparent plate disposed on the camera body side of the rearmost lens group and fixed to the fixed barrel, wherein the transparent plate is not a low-pass filter. The camera further comprises an electrical contact for receiving a signal from the camera body when attached to the camera body, and the driving means is configured to receive the signal from the camera body via the electrical contact based on the signal received from the camera body. 3. The lens barrel according to claim 1, wherein the lens barrel is driven for focus adjustment. A variator lens group housed in the fixed cylinder and disposed closer to the subject side than the rearmost lens group; and a second driving means for performing zooming by driving the variator lens group in the optical axis direction. 4. The lens barrel according to claim 1, wherein the driving unit drives the rearmost lens group with zooming to perform focus adjustment. 5. The lens barrel according to claim 1, wherein the transparent plate is an ND filter. 6. The pole according to claim 1, further comprising a pole parallel to the optical axis accommodated in the fixed cylinder, wherein the pole guides the movement of the last lens group. Lens barrel. The lens barrel according to claim 1, wherein the camera body is a video camera having a color separation prism and three CCDs. An optical apparatus using the lens barrel according to any one of claims 1 to 7.