JP2004118022A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and inexpensive camera. <P>SOLUTION: Effective parts 111a and 112a for moving a lens acting as a focal distance variable lens back and forth in the optical axis direction and extension parts 111b, 111c, 112b and 112c formed so that a rack member is pushed by the projection part of a cam barrel 110 are provided respectively in the cam grooves 111 and 112 of the cam barrel 110. If a microcomputer 150 runs away, it is reset by a watchdog timer or the like and initialized. When it is initialized, HP (Home Position) search is performed, and if a biting state is caused between the rack member 141 and a lead screw 140, such a state is dissolved by driving and rotating the cam barrel 110 so that the rack member 141 may be pushed by the projection part 113. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a camera including a photographing optical system that takes in light from a subject and forms an image on a predetermined photographing surface.
[0002]
[Prior art]
Among cameras, there is a camera in which a lens barrel is extended in response to a zooming operation such as a zoom lever. In such a camera, the lens barrel includes a cam mechanism, and the lens barrel moves back and forth in the optical axis direction when the cam mechanism receives the rotation of the motor in response to the operation of the zoom lever. The lens barrel incorporates a photographing optical system with a variable focal length. When the lens barrel moves back and forth in the optical axis direction, the focal length of the photographing optical system with a variable focal length is adjusted. There is also a focus lens in the photographing optical system, and a lens driving mechanism for moving the focus lens may be provided separately from the cam mechanism.
[0003]
In that case, for example, a rack member having teeth that are screwed into the lead screw is extended to a lens holding frame that holds the focus lens, and the lead lens is rotated to move the focus lens together with the rack member in the optical axis direction. Has been moved to. However, if the microcomputer that controls the motor that rotates the lead screw runs out of control, the lead screw continues to rotate, and the rack member moves to the tip of the lead screw and is provided at the tip of the lead screw. There is a possibility that the rack member collides and the teeth of the rack member ride on the teeth of the lead screw. When such a situation occurs, it is difficult for the lead screw teeth to rotate between the teeth of the rack member and the lead screw teeth, and the lead screw stops rotating even if the lead screw is rotated.
[0004]
In order to avoid such a situation, when the microcomputer runs away and a sticking state occurs, the rack member is brought into contact with the protrusion provided on the partition wall, and then the rack member is swung in the circumferential direction of the lead screw. A technique for separating the teeth of the rack member from the teeth of the lead screw has been introduced (Patent Document 1).
[0005]
[Patent Document 1]
JP-A-6-214282 [0006]
[Problems to be solved by the invention]
However, in Patent Document 1, there is a problem that a mechanism provided for avoiding the above sticking state is complicated, and the lens barrel becomes large and expensive.
[0007]
In view of the above circumstances, an object of the present invention is to provide a small and inexpensive camera.
[0008]
[Means for Solving the Problems]
The camera of the present invention that achieves the above object is a camera that performs photographing by capturing subject light that has entered through a photographing optical system that includes a plurality of lenses and has a variable focal length and adjustable focus.
A cam mechanism comprising a cam cylinder having a cam groove and a cam pin cam-engaged with the cam cylinder for moving at least some of the plurality of lenses for adjusting the focal length;
A first drive source for rotating the cam barrel to adjust the focal length of the photographing optical system and a cam barrel for moving at least one of the plurality of lenses for focus adjustment. A focus adjusting mechanism comprising a lead screw extending in the optical axis direction and a rack member screwed into the lead screw;
A second drive source for driving the lead screw to adjust the focus of the photographing optical system,
The cam cylinder has a protrusion on the inner wall of the cam cylinder that pushes the rack member when the rack member is in a position engaged with the tip of the lead screw.
[0009]
According to the camera of the present invention, even if the microcomputer runs out of control and the rack member and the lead screw are hardly stuck, the cam cylinder is driven to rotate and the rack member is pushed by the projection of the cam cylinder. This increases the possibility that the meshing between the rack member and the lead screw can be restored to the normal meshing state. Thus, it is only necessary to provide a projection for pushing the rack member on the cam barrel that is indispensable for the lens barrel, and since no complicated mechanism is required, the lens barrel and the camera can be downsized. The cost of the camera can be reduced.
[0010]
Here, the protrusion is located at a position where the cam pin is engaged with the tip of the lead screw when the cam pin is led to an extended portion out of the effective portion provided for the focal length of the cam groove. It is preferable that the rack member is pushed and provided at a position that avoids interference with the rack member when the cam pin is guided to the effective portion.
[0011]
Thus, when the projection is in a position that avoids interference with the rack member when guided to the effective portion of the cam pin, the cam cylinder is rotationally driven and the focal length is variable when the cam pin is guided to the effective portion of the cam groove. The focal length is adjusted by moving the lens, and when the cam cylinder is rotated and driven to a position other than its effective portion, the rack member is pushed by the projection when the lead screw and the rack member are difficult to stick. it can.
[0012]
Here, a sensor that detects that the rack member is at a predetermined home position that is lower than the tip of the lead screw;
Even if the lead screw is rotated to return the rack member to the home position, if the rack member is not detected by the sensor within a predetermined time, the rack member that should be engaged with the tip of the lead screw is It is preferable that the first drive source is provided with a drive control unit that drives the cam cylinder so as to push the cam cylinder.
[0013]
When the rack member and the lead screw are hard to be detected in this way and the rack member is not detected within a predetermined time by the sensor, for example, the microcomputer generates a time-over. The microcomputer recognizes that a sticky state has occurred.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0015]
FIG. 1 is an external view of a digital camera showing an embodiment of the present invention. FIG. 1A is a front view, and FIG. 1B is a rear view.
[0016]
As shown in FIG. 1A, the camera 100 of this embodiment is provided with a lens barrel 101. The lens barrel 101 is retracted when shooting is not performed, and is extended when shooting is performed. .
[0017]
FIG. 1A shows a state when the lens barrel 101 is extended. A flash light emitting unit 102 is provided above the lens barrel 101, and flash light is emitted from the flash light emitting unit 102 in accordance with subject brightness. A release button 103 is provided on the upper surface of the camera body, and photographing is performed when the release button 103 is pressed. A finder objective window 104 is also provided.
[0018]
As shown in FIG. 1B, a zoom lever 105 and a display screen 106 are provided on the back surface. The display screen 106 displays a subject image in a direction in which the tip of the lens barrel 101 is directed. When the zoom lever 105 is operated, the lens barrel 101 shown in FIG. 1A is further extended from a predetermined position, and the focal length of some lenses of the photographing optical system is variable. The focal length is adjusted by moving the lens barrel together with the lens barrel. Note that the camera of this embodiment is also provided with a viewfinder eyepiece 107 so that the subject image can be confirmed not only on the display screen 106 but also on the viewfinder.
[0019]
FIG. 2 is a diagram showing the arrangement of the cam barrel 110 and the focus lens drive unit arranged inside the lens barrel 101. 2A is a perspective view of the cam barrel, FIG. 1B is a diagram showing a configuration of a protrusion provided on the cam barrel 110, and FIG. 1C is a lens mirror along the optical axis. It is sectional drawing which cut | disconnected the trunk | drum.
[0020]
As shown in FIG. 2A, the cam cylinder 110 is provided with two cam grooves 111 and 112, respectively, and cam pins 130a and 130b provided in a lens holding frame described later are provided in the cam grooves 111 and 112, respectively. Engaged. These cam grooves have portions 111a and 112a provided in an oblique direction with respect to the optical axis, and portions 111b and 111c provided at both ends of these portions and provided in a direction substantially orthogonal to the optical axis, 112b, 112c. When the cam pins 130a and 130b provided in the lens holding frame move along the cam grooves 111a and 112a provided in the oblique direction, the lens holding frame provided with the cam pins moves back and forth in the optical axis direction together with the lens functioning as a focal length variable lens. Move to. Of these cam grooves, the oblique portions of the cam grooves correspond to the effective portions referred to in the present invention. When the cam pins 130a and 130b move through the effective portions of the cam grooves, the lens acting as a variable focal length lens is moved and the focal length is adjusted. In the following description, this effective portion is described as a variable magnification region. In addition, a portion other than the effective portion, that is, the extended portions 111b, 111c, 112b, and 112c will be described as being outside the zooming range.
[0021]
A protrusion 113 is provided on the inner wall of the cam cylinder 110, and the protrusion 113 is located away from the cam grooves 111 and 112, as shown in FIG. 2B, and parallel to the groove 111c outside the zooming area. Is provided.
[0022]
FIG. 2C shows a state in which the cam barrel 110 is disposed on the lens barrel 101. As shown in FIG. 2C, a moving cylinder 120 is provided on the outer peripheral side of the cam cylinder 110, and a rectilinear groove 121 is provided in the moving cylinder 120. Inside the cam barrel, a lens 130 acting as a lens having a variable focal length is held by a lens holding frame 131. The lens holding frame 130 is provided with the two cam pins 130a and 130b described above, and these cam pins 130a and 130b are respectively engaged with cam grooves 111 and 112 provided in the cam cylinder. Further, the cam pins 130a and 130b are respectively engaged with the rectilinear grooves 121a and 121b of the movable cylinder 120 through the cam grooves 111 and 112, respectively. The rotating cylinder 110 is connected to a motor 152 via a drive transmission unit 155, the motor 152 is driven by a driver 151, and the driver 151 is controlled by the microcomputer 150. When the motor 151 rotates according to an instruction from the microcomputer 150, the rotation is transmitted to the cam cylinder 110 by the drive transmission unit 155, and the cam cylinder 110 is rotationally driven. When the cam cylinder 110 is driven to rotate and the focal length is adjusted, the cam pins 130a and 130b move along the effective portions 111a and 112a of the cam grooves 111 and 112 provided in the cam cylinder 110, respectively, and the lens together with the cam pins 130a and 130b. The holding frame 130 moves along the rectilinear grooves 121a and 121b, and the lens 130c moves back and forth in the optical axis direction together with the lens holding frame 130. This motor 151 corresponds to the first drive source referred to in the present invention.
[0023]
On the other hand, a lead screw 140 is screwed into a rack member 141 provided in the lens holding frame 142 that holds the focus lens 142a. Therefore, when an instruction is issued from the microcomputer 150 to the driver 153 and the motor 154 rotates forward and the lead screw 140 rotates, the teeth of the rack member 141 are screwed on the teeth of the lead screw 140 and together with the rack member 141, the lens holding frame. 142 moves toward the partition 110a side. If the motor 154 rotates in the reverse direction, the rack member 141 is returned to the HP sensor 144 side. Note that one end of the lens holding frame 142 is also engaged with the guide member 143 so that the lens holding frame 142 holding the focus lens 142a is not inclined with respect to the optical axis. In the camera of the present embodiment, an HP (Home Position) sensor 144 is provided on the base side of the lead screw 140 in order to detect the position of the focus lens 142a, and the rack member 141 is driven to the position of the HP sensor 144. When disposed, the microcomputer 150 recognizes the position of the focus lens 142a. That is, the focus lens 142a can be moved by rotating the lead screw 140 with the position at which the rack member 141 crosses the HP sensor 144 as a home position, and the focal point. The HP sensor 144 is composed of a photo interrupter, and the rack member 141 has a portion 141a for operating the photo interrupter. When the portion 141a of the rack member 141 crosses the HP sensor 144 made of a photo interrupter, the output signal of the HP sensor 144 changes. The detection of the home position of the focus lens 142a by detecting the position of the home position in this way is called an HP search. When this HP search is performed and the home position of the focus lens 142a is detected, the focus lens 142a is driven to the focal point with reference to that position.
[0024]
In such a camera 100, the focus lens 142a is driven each time the direction in which the tip of the lens barrel 101 is directed is changed. At this time, for example, after HP search is performed and the home position is determined, the focus lens 142a is driven to the focal point. When the zoom lever 105 is operated here, the cam barrel 110 is driven by the motor 152 and the lens barrel 110 is extended to perform zooming, and the focused subject is enlarged and displayed on the display screen 106. . The motor 154 corresponds to the second drive source referred to in the present invention.
[0025]
However, the microcomputer 150 may run away when the tip of the lens barrel 101 is pointed at the subject and the focus is being adjusted. At this time, the motor 154 may continue to rotate in one direction, and the rack member 141 may be driven to the end of the lead screw 140 and collide with the partition wall 110a. This state is shown in FIG. At this time, a tight contact between the lead screw 140 and the rack member 141 occurs. Since the microcomputer 150 runs out of control, the microcomputer 150 falls into an uncontrollable state, and this sticking state becomes even worse. Therefore, the camera of this embodiment is provided with a hard reset switch (not shown). When this hard reset switch is operated, the microcomputer 150 is reset.
[0026]
When resetting is performed in this way, the microcomputer 150 is initialized and the same operation as when the power is turned on is performed. Naturally, the HP search is also performed at that time. However, when a sticking state between the rack member 141 and the lead screw 140 is generated, the lead screw 140 does not rotate. Since the position of is not detected, the microcomputer will time out.
[0027]
Therefore, in the camera of this embodiment, when the time is over, the cam cylinder 110 is rotationally driven to guide the cam pins 130a and 130b to the outside of the zooming range 111c, the protrusion 113 is positioned near the rack member 141, and the rack member 141 is pushed. Tackling is avoided.
[0028]
FIG. 3 is a configuration block diagram of a signal processing unit in the camera 100.
[0029]
As shown in FIG. 3, the microcomputer 150 includes a CPU 150a, a ROM 150b, and a RAM 150c. The motor 152 for rotating the cam cylinder 110 and the motor 154 for rotating the lead screw 140 are each controlled by the CPU 150a. The ROM 150b stores a program for causing the CPU 150a to perform processing, and the motor 150a rotates or stops according to the procedure of the program. The RAM 150c temporarily stores data when processing is performed according to the procedure of the program, and an instruction is issued from the CPU 150a to each of the drivers 151 and 153 based on the data. The microcomputer 150 including the CPU 150a, the ROM 150b, and the RAM 150c corresponds to the drive control unit referred to in the present invention.
[0030]
In the camera of this embodiment, a stepping motor 154 is used for driving the lead screw 140, and a driving pulse is supplied from the driver 153 to the stepping motor 154 in accordance with an instruction from the microcomputer 150 to rotate at a predetermined angle. Driven. The configuration of the stepping motor 154 will be briefly described, and what will happen when there is a difficult sticking between the lead screw teeth and the rack member teeth.
[0031]
In the case where the above-described difficulty occurs, even if a drive pulse is supplied to the stepping motor 154, the rotor of the stepping motor 154 does not rotate. It is conceivable that the rotor magnets are located between the exciting coils arranged at predetermined angles on the stator side of the stepping motor 154. In the stepping motor 154, drive pulses having different phases are supplied to the respective excitation coils arranged at predetermined intervals, and the excitation coils are excited to form a rotating magnetic field. At this time, a repulsive force / attractive force acts between each excitation coil and each magnet of the rotor, so that the rotor rotates by a predetermined angle. Of course, when the rotation of the motor stops, one of the magnets of the rotor should stop near one of the exciting coils on the stator side. However, when a sticking state occurs, the rotor-side magnet stops between the excitation coils arranged at predetermined intervals on the stator side, and even if the excitation coil is excited by the drive pulse, the rotor magnet There is a possibility that the rotating magnetic field does not work well. When such a situation occurs, the position of each of the rotor magnets is rotated to a position of one of the excitation coils by a predetermined angle so that the rotating magnetic field generated in each of the excitation coils can be successfully applied to the rotor magnet. There is a need.
[0032]
Therefore, in the camera of the present embodiment, the motor 151 is driven based on an instruction from the microcomputer 150 to rotate the cam cylinder 110, and the rack member 141 is pushed by the projection 113 provided on the cam cylinder 110, so that the lead screw 140. Is pushed in the rotation direction of the rotor to move the position of the rotor magnet of the stepping motor 154. That is, when the projection 113 of the cam cylinder 110 pushes the rack member 141, the lead screw 140 is pushed by a predetermined angle to move the position of the magnet of the rotor of the stepping motor 140 to one of the excitation coils. It is a translation. At this time, a clearance is generated between the teeth of the lead screw 140 and the teeth of the rack member 141 to release the contact state between the teeth of the rack member and the teeth of the lead screw, which are balanced by static friction, and rotate the lead screw. Transition to a possible state. At this time, when drive pulses having different phases are applied to the respective excitation coils on the stator side of the stepping motor 154, a predetermined rotating magnetic field is formed by the exciting coil, and the rotor magnet starts rotating by the rotating magnetic field, and the lead screw 140 is rotated. Begins to rotate.
[0033]
FIG. 4 is a flowchart showing a program procedure when the HP search is performed.
[0034]
In step S41, for example, a hard reset switch is operated to perform initialization, and an HP search is performed. This HP search is performed to detect the output signal of the HP sensor 144 by the CPU 150a and drive the focus lens 142a to the focal point with the position as the origin.
[0035]
In step S41, if the home position of the focus lens 142a is not detected within a predetermined time and is determined to be NG, the cam cylinder 110 is driven out of the zooming range in step S42. When the cam cylinder 110 is driven out of this zooming range, the projection 113 of the cam cylinder 110 pushes the rack member 141 in the rotational direction of the lead screw 140 by a predetermined angle. When the rack member 141 is pushed by the projection 113 of the cam barrel 110, the cam barrel 110 is rotationally driven to the zooming range in step S43, so that the rack member 141 is not pushed by the projection 113 of the cam barrel. . When the rack member 141 is impacted by the projection 113 in this way, a driving instruction is issued to the stepping motor 154 and the HP search is performed again. When the HP search is performed in step S44 and the position of the rack member 141 is recognized by the microcomputer 150 by the HP sensor 144, it is determined as OK and the HP search is terminated.
[0036]
If it is determined as NG in step S45, the drive of the motor 154 is stopped, and a focus error occurs and the HP search is terminated.
[0037]
FIG. 5 is a flowchart showing another procedure for returning from the clenched state to the normal meshing state.
[0038]
Although a corresponding effect can be obtained in the flowchart of FIG. 4, when the rack member 141 is pushed by the projection 113 of the cam cylinder 110, a repelling of the lead screw 140 avoids a less effective state.
[0039]
In step S51, the lead screw 140 is reversely rotated before the cam cylinder 110 is rotated out of the zooming range. Here, reverse rotation refers to the direction of returning to the HP sensor 144 side. When the lead screw 140 is driven in the direction to return the rack member 141 to the HP sensor 144 side in step S52, the rack member 141 is pushed by the protrusion 113 when the cam cylinder 110 is rotated outside the zooming range in step S53. In step S54, the cam cylinder 110 is rotationally driven to return the cam pins 130a and 130b to the zooming range, and an HP search is performed in the next step S55. If the home position is detected by the HP sensor 144 in step S55, it is determined as OK and the HP search ends. If it becomes NG in step S55, the drive of the motor is stopped in step S56, a focus error occurs in step S57, and the HP search ends.
[0040]
As a result, a more effective gap can be generated between the teeth of the lead screw and the rack member than in the case of FIG. 4, and the state of the rotor side and the stator side of the stepping motor 153 is improved to improve the rack. The probability that the engagement between the member and the lead screw is restored is increased.
[0041]
As described above, the engagement between the lead screw teeth and the rack member teeth is normally achieved by using the power of the cam cylinder rotation drive by simply providing a protrusion on the inner peripheral surface side of the cam cylinder necessary for the zooming operation. It is possible to return to the correct state. Since the motor that drives the cam cylinder is a motor having a larger power than the motor that drives the lead screw, the rack member can be effectively pushed by the protrusion with a large driving force, and the rotor of the stepping motor While the position is returned to the normal position, the lead screw can be rotated by returning the meshing between the teeth of the lead screw and the teeth of the rack member to the normal state.
[0042]
Since a mechanism for avoiding the sticking state can be provided without providing a complicated mechanism in this way, the number of parts can be reduced as compared with the conventional one and an inexpensive camera can be provided. Even if the lead screw teeth and the rack member teeth are difficult to reach and the lead screw stops rotating, the failure rate can be reduced because the situation is improved simply by operating the hard reset switch. Become a camera with good quality.
[0043]
【The invention's effect】
As described above, according to the camera of the present invention, a small and inexpensive camera can be provided.
[Brief description of the drawings]
FIG. 1 is an external view of a camera according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a lens barrel portion of the digital camera of FIG.
3 is a block diagram showing a configuration of the digital camera of FIG. 1. FIG. 4 is a flowchart when an HP search is performed.
FIG. 5 is another flowchart when an HP search is performed.
[Explanation of symbols]
100 Digital camera 110 Cam cylinder 111 112 Cam groove 111a 112a Cam groove effective part 111b 111c 112b 112c Cam groove extension part 113 Projection part 120 Moving cylinder 130 Lens holding frame 130a 130b Cam pin 140 Lead screw 141 Rack member 142 Lens holding frame 143 Guide member 144 Guide shaft 145 HP sensor 150 Microcomputer 150a CPU
150b ROM
150c RAM
151 Driver 152 Motor (first drive source)
153 Driver 154 Motor (second drive source)

Claims (3)

In a camera that shoots by capturing subject light that has entered through a photographic optical system with a variable focal length and adjustable focus that consists of multiple lenses,
A cam mechanism including a cam cylinder having a cam groove and a cam pin cam-engaged with the cam cylinder for moving at least a part of the plurality of lenses for focal length adjustment;
A first drive source for rotationally driving the cam cylinder to adjust the focal length of the imaging optical system;
A focus screw comprising a lead screw extending in the optical axis direction and a rack member screwed into the lead screw, disposed in the cam barrel, for moving at least one of the plurality of lenses for focus adjustment. An adjustment mechanism;
A second drive source that drives the lead screw to adjust the focus of the photographing optical system;
2. The camera according to claim 1, wherein the cam cylinder has a protrusion on the inner wall of the cam cylinder that pushes the rack member when the rack member is in a position where the rack member is engaged with the tip of the lead screw. The projecting portion is located at a position where the cam pin is engaged with the tip of the lead screw when the cam pin is led to an extended portion that is deviated from an effective portion provided for the focal length of the cam groove. 2. The camera according to claim 1, wherein the camera is provided at a position where a certain rack member is pushed and when the cam pin is guided to the effective portion, the interference with the rack member is avoided. A sensor that detects that the rack member is at a predetermined home position that is lower than a tip of the lead screw;
Even if the lead screw is rotated to return the rack member to the home position, when the rack member is not detected by the sensor within a predetermined time, the rack member that should be engaged with the tip of the lead screw is The camera according to claim 1, further comprising: a drive control unit that causes the first drive source to drive the cam cylinder so as to be pushed by a protrusion.

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