JP2535013B2 - Variable focus camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a so-called varifocal camera capable of switching a plurality of focal lengths by switching an optical system.

(Background of the Invention) Conventionally, various varifocal cameras capable of switching the focal length of a taking lens have been proposed. However, these variable power methods are methods in which the sub optical system (conversion lens) is inserted after the main optical system moves along the optical axis.

(Problems to be Solved by the Invention) In the variable magnification type variable focus camera in which the sub optical system (conversion lens) is inserted on the optical axis, a mechanism for inserting the sub optical system is required. In addition, the mechanism has a problem that the sub-optical system must be accurately inserted on the optical axis, so that the mechanism is complicated, and it is difficult to adjust the optical axis in the manufacturing process. Further, when the sub optical system is inserted, there is a problem that the F value (value indicating the brightness) of the lens is significantly increased and the lens becomes dark.

The present invention has been made in view of the above problems, and an object thereof is to eliminate the need for a sub-optical system, a simple mechanism, easy adjustment in the manufacturing process, and an F value of a lens at each focus that does not change much. It is an object of the present invention to provide a varifocal camera that can quickly and accurately switch the focal length.

(Means for Solving Problems) The present invention for solving the above problems is a variable focus camera capable of switching to a plurality of focal lengths by moving a plurality of lenses along an optical axis, and a fixed barrel. A cam barrel rotatably supported by the fixed barrel, a movable lens frame for holding the plurality of lenses, and a focal length engraved on one of the fixed barrel and the cam barrel. A moving region for moving and a plurality of focusing regions continuously provided in the moving region, and a cam groove with which the moving lens frame engages, and provided on the other of the fixed barrel and the cam barrel,
A linear guide means for guiding the movable lens frame in parallel along the optical axis, a motor for rotationally driving the cam barrel, and the movable lens frame engaged with the cam groove, the movable region and the plurality of focusings. Detecting where in the area, the detection means that outputs the detection result, and drive control of the motor in the moving area and the plurality of focusing areas based on the detection result of the detection means. And at least in the moving area, the control means for driving the motor is faster than the plurality of focusing areas.

(Operation) In the variable focus camera of the present invention, when the cam barrel is rotated with respect to the fixed barrel by the motor, the moving lens frame holding the moving lens is moved along the optical axis by the cam groove and the straight guide means. Then, the zooming and focusing are performed. At this time, the control means performs drive control of the motor in the moving area and the focusing area based on the detection result of the detecting means indicating where the moving lens frame exists in the moving area and the focusing area, and at least,
In the moving area, the motor is driven faster than in the focusing area.

Therefore, the motor is driven at a high speed only in the moving region that is unrelated to the positioning accuracy of the focusing, so that the positioning accuracy does not deteriorate despite the quick switching of the focal length. Therefore, the focal length can be switched quickly and accurately.

(Example) Next, the Example of this invention is described using drawing.

FIG. 1 is a perspective view showing an embodiment of the present invention. In the figure,
Reference numeral 1 is a fixed body fixed to the camera body, and 2 is a cam body rotatably supported by the fixed body 1. The cam barrel 2 has a cam groove 3 for moving the first lens group and a cam groove 4 for moving the third lens group.
Are engraved in pairs. A photographing lens 5 is arranged in the fixed barrel 1, and the lens arrangement is shown in FIGS. 2 and 3.

The taking lens 5 in this embodiment includes a first lens group 5a, a second lens group 5b, a third lens group 5c and a master lens system 5e. FIG. 2 shows the lens arrangement on the telephoto (tele) side.
Focusing with this long focal length is performed by moving only the first group lens 5a along the optical axis. Further, FIG. 3 shows the lens arrangement on the wide angle side, and from the state of FIG. 2 showing the telephoto side, the first lens group 5a and the third lens group 5c, which are moving lenses, are arranged along the optical axis of the camera. It is moving toward the body. Focusing with this short focal length is performed by moving only the first lens group 5a along the optical axis. Further, between the third group lens 5c and the master lens 5e,
A diaphragm mechanism 6 is provided.

Returning to FIG. 1, the explanation will be continued. The fixed barrel 1 is a main body 1a that rotatably supports a cam barrel 2, a second lens group fixed barrel 1b that holds a second lens group 5b, and a master lens fixed barrel that holds a master lens 5d. Composed of 1c. As the linear guide means, a first group lens moving linear guide groove 1d extending in parallel to the optical axis is provided on the left side and the right side of the main body 1a in the drawing, and an optical guide is provided on the upper and lower parts of the drawing. A third group lens moving linear guide groove 1e extending parallel to the axis is provided. The first group lens 5a is held by a first group lens frame 7 which is a movable lens frame, and the first group lens frame 7 is fitted into the main body 1a of the fixed barrel 1. Then, the first lens group frame 7
Is provided with a cam pin 7a having a small friction coefficient, and the cam pin 7a is engaged with the first group lens moving linear guide groove 1d and the first group lens cam groove 3. The third lens group 5c is held by a third lens group frame 8 which is a moving lens frame, and the third lens group frame 8 is arranged in the second lens group fixed barrel portion 1b. A through groove 1f for a third lens group is formed in the upper and lower parts of the second lens group fixing barrel portion 1b in the drawing, and the third lens group through groove 1f is formed.
The supporting portion 8a of the group lens frame 8 is inserted through the third group lens through groove 1f, and further, the cam pin 8b having a small friction coefficient provided in the supporting portion 8a has the third group lens moving linear guide groove 1e and the third group lens moving groove 1f. Three
It is engaged with the cam groove 4 for moving the group lens. Also, the cam body 2
At the base of the cam body gear part with a rack engraved in the circumferential direction
2a is provided. Reference numeral 9 is a DC motor for driving the cam barrel, which rotates the motor 9 via a reduction gear train 10 meshing with a pinion 9b of an output shaft 9a of the motor 9 for driving the cam barrel and the cam barrel gear portion 2a. The dynamic output is transmitted to the cam barrel 2 so that the cam barrel 2 rotates. Cam body gear part 2a of cam body 2
An encoder substrate 11 provided with a predetermined print pattern is fixed to the fixed cylinder 1 in the vicinity. The cam body 2 is provided with a protrusion 2b, and the encoder substrate 11 is provided on the protrusion 2b.
A brush 12 which is slidably contacted with is attached.

Next, with reference to FIG. 4 showing a developed configuration diagram of the cam barrel 2,
The cam groove 3 for moving the first lens group and the cam groove 4 for moving the third lens group will be described. The first group lens moving cam groove 3 has three parts: a wide focusing area 3a, a variable magnification area 3b continuously provided to the wide focusing area 3a, and a tele focusing area 3c continuously provided to the variable magnification area 3b. It consists of parts. Similarly, the cam groove 4 for moving the third lens group is also wide,
Focusing area 4a, the wide focusing area
It is composed of three parts, a variable power region 4b continuously provided with 4a and a tele-focusing region 4c continuous with the variable power region 4b.
When the cam barrel 2 rotates, the first group lens frame 7 having the cam pins 7a guided by the first group lens moving cam groove 3 and engaged with the first group lens moving cam groove 3 is formed.
The (first lens group 5a) moves in the optical axis direction (indicated by an arrow). Also, guided by the third lens group moving cam groove 4,
The third lens group frame 8 (third lens group 5c) having a cam pin 8b that engages with the third lens group moving cam groove 4 also moves in the optical axis direction. Here, the variable power region 3b of the first group lens moving cam groove 3 and the variable power region 4b of the third group lens moving cam groove 4 are inclined with respect to the optical axis, and the inclination is the cam barrel. By rotating 2 the first lens group 5a and the third lens group 5c
And are selected to move in the optical axis direction from the telephoto lens arrangement to the wide-angle lens arrangement (or vice versa) by a predetermined amount.
Further, the wide focusing area 3a and the tele focusing area 3c of the cam groove 3 for moving the first lens group are inclined with respect to the optical axis direction. , Have been chosen to move the amount needed to focus. Further, the wide focusing region 4a and the tele focusing region 4c of the third lens group lens moving cam groove 4 are parallel to the rotation direction of the cam barrel 2 in FIG. Even if it moves, the third lens group 5c does not move.
By doing so, it is possible to rotate the cam barrel 2 to continuously perform wide focusing, zooming, and tele focusing.

Next, the means (encoder) 13 for detecting the rotation of the cam barrel 2 will be described with reference to FIGS. As shown in FIG. 5, the encoder board 11 provided on the fixed barrel 1 is
Line-shaped conductive patterns 11a, 11b, 11c, and 11d of the book are provided. And these line-shaped patterns
Four conductive sliding contact branches 12a, 12 are provided on 11a, 11b, 11c and 11d.
The brush 12 having b, 12c, and 12d is configured to slide and move from the wide focusing area to the tele focusing area via the zooming area as the cam body 2 rotates. Furthermore, the sliding contact branches 12a, 12b, 12c and 12d of the brush 12
The base ends of are connected. Terminals I, II, III are provided at one end of each pattern 11a, 11b, 11c and 11d of the encoder board 11.
And IV are provided and their terminals I, II, III and IV are connected to the circuit shown in FIG. Terminal I is terminal a,
It is connected to the anode of a DC power supply B of V (v) via a resistor R _I. Terminal II is connected to an anode of a DC power supply B via the terminal b, the resistance R _II. Terminal III is grounded. The terminal IV is connected to the anode of the DC power supply B via the terminal c and the resistor R _III . The cathode of the DC power source B is grounded, like the terminal III. When such a circuit is connected, the outputs at terminals a, b and c are as shown in FIG. The output at the terminal c in the wide focusing area and the tele focusing area is a pulse. This is because the pattern 11d of the encoder substrate 11 has a comb-shaped portion in the wide focusing area and the tele focusing area.
This is because it is 11e and 11f. In this embodiment, the pitch of the comb teeth 11e of the wide focusing area and the comb teeth 11f of the tele focusing area and the number of steps of the comb teeth are different, and the pitch of the tele focusing area is narrower, or, The number of steps of comb teeth is also increasing. Then, by detecting the outputs of the terminals a, b and c of the encoder 13, it is possible to detect in which area the cam barrel 2 is located.

Next, the drive circuit of this embodiment will be described with reference to FIG. In the figure, 13 is an encoder for detecting in which area the cam barrel 2 is, 14 is a phase difference detection method,
Distance measuring element for detecting the defocus direction and defocus amount, 15 is a tele / wide magnification changeover switch, 16 is a motor power supply, 17 is information from the encoder 13, distance measuring element 14 and magnification changeover switch 15. Then, the control circuit controls the motor 9 based on these pieces of information. This control circuit 17
Controls the motor 9 shown in FIG. 9 in each region. (A) is a control method of the motor 9 in the variable power region.
At this time, the motor 9 is driven at a high speed by a constant voltage.
(B) is a control method of the motor 9 in the wide focusing region (focusing region of short focal length). At this time, the motor 9 is driven at a low speed by the pulse voltage, but the positioning accuracy is improved as compared with the constant voltage driving described above. (C) is a control method of the motor 9 in the tele focusing area (focusing area of long focal length). At this time, the motor 9 is driven at a low speed by the pulse voltage as in the wide focusing region, but since the depth of focus becomes shallower in the telephoto mode than in the wide angle mode, the duty ratio is made smaller than (B) and the wide focusing mode is set. The driving speed is lower than that of the area, and the positioning accuracy is further improved.

Next, the operation of the above configuration will be described. First, the magnification changeover switch 15 is operated to switch between telephoto and wide-angle. Then
The control circuit 17 drives the motor 9 at a constant voltage to rotate the cam barrel 2 until the lens system enters the tele-focusing region or the wide-focusing region. Next, the information on the defocus direction and the defocus amount of the subject is taken into the control circuit from the distance measuring element 14. The control circuit 17 uses the position information of the cam barrel 2 from the encoder 13 and the defocus direction and the defocus amount information from the distance measuring element 14 described above to determine how much the cam barrel 2 should be rotated in which direction. The system calculates whether or not to focus, and based on the calculation result, the motor 9 is driven by the above-mentioned pulse voltage, and the cam barrel 2 reaches the in-focus position.
Rotate.

According to the above configuration, since the lens system of the multifocal camera of the present embodiment does not have the sub optical system, the mechanism is simple, the adjustment in the manufacturing process is easy, and the F value of the lens at each focus does not change so much. Further, the information from the encoder 13, the distance measuring element 14, and the magnification changeover switch 15 is taken into the control circuit 17, and the motor 9 is controlled based on these information, whereby the autofocus can be realized. Further, in the focusing area and the magnification changing area, the driving speed of the motor 9 can be freely set by setting the driving voltage of the motor 9 to a pulse voltage, and the comb teeth 11e and 11f of the pattern 11d in the focusing area can be set. By changing the pitch and the number of steps of the comb teeth, the control method and accuracy of the motor 9 can be arbitrarily changed according to the focal length of the lens system.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the fixed barrel 1 has the first group lens moving linear guide groove 1d and the third group lens moving linear guide groove 1e formed therein, and the cam barrel 2 has the first group lens moving cam groove 3d. Although the cam groove 4 for the third lens group is formed, on the contrary, the cam grooves for moving the first lens group and the third lens group are formed in the fixed barrel 1 and the cam barrel 2 is formed.
The present invention can be realized by engraving the linear guide grooves for moving the first lens group and the third lens group. The cam pins 7a and 8b that engage with the linear guide groove and the cam groove may be rollers.
Further, a rod installed parallel to the optical axis is used as the straight-moving guide means, the rod is provided on either one of the cam barrel and the fixed barrel, and the cam groove is provided on the other, and the movable lens frame is engaged with the rod. However, the present invention can be realized. Further, in the above-described embodiment, the image pickup lens 5 in which the first lens group 5a and the third lens group 5c move for zooming and the first lens group 5a alone moves for focusing has been described. For example, the zooming is not limited to the second lens group 5b and the third lens group.
5c moves, and the focusing lens moves only the first lens group 5a (in this case, the first lens group moving cam groove is provided with a groove in the variable power region around the optical axis). The present invention can be applied even if the first lens group does not move in the optical axis direction during zooming.

Then, as shown in FIG. 10, all the patterns 11d of the encoder substrate 11 are formed in a comb-teeth shape, the number of pulses is counted in the variable magnification region, and when the cam barrel 2 is rotated in the variable magnification region, when the focusing region is approached, The motor 9 may be decelerated. By doing so, it is possible to smoothly switch from the high-speed zoom area to the focusing area that requires accuracy. Although the motor 9 is a DC motor, it is not limited to this and may be, for example, a stepping motor, or focusing may be performed manually instead of driving the motor. Further, in the above embodiment, the taking lens 5 having two focal points of telephoto and wide-angle has been described, but the taking lens having three focal points of telephoto, standard and wide-angle may be used.
If a cam groove 23 for moving the first lens group and a cam groove 24 for moving the third lens group are formed in the cam barrel 2 as shown in FIG. 11,
It is possible to continuously perform telephoto focusing, zooming, standard focusing, zooming, and wide-angle focusing. Further, in this case, as shown in FIG. 12, the patterns 11f, 11g, 11h and 11i are formed on the encoder substrate 11.
By providing the above, at the terminals a, b and c of the circuit shown in FIG. 6, an output as shown in FIG. 13 can be obtained,
It is possible to detect in which area the cam barrel 2 is located.

Further, as shown in FIGS. 14 and 15, teeth are engraved on the circumferential surface of a disk-shaped encoder board 21 to allow the encoder board 21
Is engaged with the cam body gear portion 2a. When the pattern shown in FIG. 13 is provided on the encoder board 21, when the cam barrel 2 rotates from wide-angle U = ∞ to telephoto U = ∞ (or from wide-angle U = min to telephoto U = min). , The encoder board 21 is 1
Make it to rotate. By doing this, the pattern of the focusing area can be used in both wide-angle and telephoto. Although the distance measuring element 14 uses the phase difference detection method, other methods such as a contrast detection method may be used.

(Effects of the Invention) As described above, according to the present invention, the sub-optical system is unnecessary, the mechanism is simple, and the adjustment in the manufacturing process is easy.
It is possible to realize a varifocal camera in which the F value of the lens at each focus does not change much. Further, according to the present invention, since the motor is driven at a high speed only in the moving region that is unrelated to the positioning accuracy of focusing, the positioning accuracy does not deteriorate despite the quick switching of the focal length. . Therefore, it is possible to realize a variable focus camera that can switch the focal length quickly and accurately.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part showing an embodiment of the present invention, and FIG.
FIGS. 3 and 4 are views showing the lens arrangement in FIG. 1, FIG. 4 is a development configuration diagram of the cam barrel in FIG. 1, FIG. 5 is a plan view of the encoder board in FIG. 1, and FIG. FIG. 7 is a circuit diagram connected to the encoder board in FIG. 1, FIG. 7 is a diagram showing outputs in respective areas of terminals a, b, c in FIG.
FIG. 8 is a drive circuit diagram in FIG. 1, FIG. 9 is a diagram showing motor drive control in each region in FIG. 1, and FIG. 10 is a plan view of an encoder substrate showing another embodiment of the present invention.
11 is a development configuration diagram of a cam barrel showing another embodiment of the present invention, FIG. 12 is a plan view of an encoder board when the cam barrel of FIG. 11 is used, and FIG. 13 is an encoder of FIG. FIG. 6 is a diagram showing the output in each region of the terminals a, b, c in FIG. 6 when a substrate is used, FIG. 14 is a perspective view of the main part showing another embodiment of the present invention, and FIG. FIG. 15 is a plan view of the encoder board in FIG. 14. 1 ... Fixed barrel, 1a ... Main body 1b ... Second lens group fixed barrel section 1c ... Master lens system fixed barrel section 1d ... First group lens moving linear guide groove 1e ... Third group lens movement Linear guide groove 2 …… Cam barrel, 2a …… Cam barrel gear part 2b …… Protrusion 3,23 …… Cam groove for moving 1st group lens 4,24 …… Cam groove for moving 3rd group lens 5 …… Photographing lens 5a ... 1st group lens, 5b ... 2nd group lens 6 ... Aperture mechanism, 7 ... 1st group lens frame 7a, 8b ... Cam pin 8 ... 3rd group lens frame, 8a ... … Support part 9 …… Motor, 9a …… Output shaft 10 …… Reduction gear train 11, 21 …… Encoder board 12 …… Brush, 13 …… Encoder 14 …… Distance measuring element 15 …… Magnification switch 16 …… Motor power supply, 17 ... Control circuit

Claims (2)

(57) [Claims] 1. A varifocal camera capable of switching to a plurality of focal lengths by moving a plurality of lenses along an optical axis, comprising a fixed barrel and a cam barrel rotatably supported by the fixed barrel. A moving lens frame for holding the plurality of lenses, a moving region for enlarging one of the fixed barrel and the cam barrel for switching a focal length, and a plurality of moving regions connected to the moving region. A cam groove formed of a focusing area and engaged with the moving lens frame, and a straight-moving guide means provided on the other of the fixed barrel and the cam barrel for guiding the moving lens frame in parallel along the optical axis. A motor for driving the cam barrel to rotate, and the moving lens frame engaged with the cam groove, detecting where the moving region and the plurality of focusing regions are, and output And a drive control of the motor in the moving region and the plurality of focusing regions based on the detection result of the detecting unit, and at least in the moving region, faster than the plurality of focusing regions, A variable focus camera, comprising: a control unit that drives the motor. 2. As the control means, for driving control of the motor in the plurality of focusing regions, a motor that drives the motor in a focusing region having a long focal length is slower than in a focusing region having a short focal length. The variable focus camera according to claim 1, which is used.