JPH07109468B2 - Variable focus camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a variable focus camera having a plurality of focal lengths by switching an optical system.

(Background of the Invention) Conventionally, various variable focus cameras having a plurality of focal lengths by switching an optical system 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 focal length camera of the variable power system in which the sub optical system (conversion lens) is inserted into the optical axis, a mechanism for inserting the sub optical system is required. In addition, since the sub-optical system must be accurately inserted on the optical axis, 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, the mechanism to be simple, the optical axis alignment adjustment in the manufacturing process to be easy, and the F value of the lens at each focus. It is to provide a variable focus camera that does not change much.
Another object of the present invention is to provide a varifocal camera in which various adjustments can be easily performed during camera product inspection.

(Means for Solving the Problems) The present invention for solving the above problems is a variable focus camera that can switch to a plurality of focal lengths by moving a plurality of lenses along an optical axis, and is fixed. A barrel, a cam barrel rotatably supported by the fixed barrel, and a movable lens frame for holding the plurality of lenses, for switching the focal length to either the fixed barrel or the cam barrel. Moving area,
And two focusing regions that are continuously provided at both ends of the moving region and have an end point in the direction opposite to the moving region having an afocal point, and further, a cam groove with which the moving lens frame engages is engraved, and on the other side, A linear guide means for guiding the movable lens frame in parallel along the optical axis is provided, and the zooming and focusing are performed by rotating the cam barrel.

(Operation) In the variable focus camera of the present invention, by rotating the cam barrel with respect to the fixed barrel, the moving lens frame that holds the moving lens is engaged with the cam groove in the optical axis direction by the linear guide means. It moves parallel along and zooming and focusing are performed.

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

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

The bifocal 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. Figure 2 shows the lens arrangement on the telephoto side.
Focusing is performed by moving the first lens group 5a along the optical axis. Also, FIG. 3 shows a wide angle.
With the lens arrangement on the side, the first lens group 5a and the third lens group 5c, which are moving lenses, are moving in the camera body direction along the optical axis from the state of FIG. 2 showing the telephoto side. Also in this lens arrangement, focusing is performed by moving only the first group lens 5a along the optical axis. Also, the third
A diaphragm mechanism 6 is arranged between the group lens 5c and the master lens 5e.

Returning to FIG. 1, the explanation will be continued. The fixed barrel 1 includes a main body 1a that rotatably supports the cam barrel 2, a second lens group fixed barrel 1b that holds the second lens group 5b, and a master lens fixed barrel that holds the master lens 5e. Composed of 1c. As the linear guide means, a first group lens moving linear guide groove extending in the optical axis direction is provided on the left side portion and the right side portion of the body portion 1a in the drawing.
1d and a third group lens moving linear guide groove 1e extending parallel to the optical axis are formed in the upper and lower portions of the drawing. 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 moving cam groove 3. 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 fixing barrel 1b. A through groove 1f for a third lens group is formed in the upper and lower parts of the second lens group fixing body 1b in the drawing, and the supporting portion 8a of the third lens group frame 8 is used for the third lens group. The cam pin 8b having a small friction coefficient provided in the support portion 8a is inserted through the through groove 1f, and the third group lens moving linear guide groove 1e is formed.
And is engaged with the cam groove 4 for moving the third lens group. or,
The base of the cam barrel 2 is provided with a cam barrel gear portion 2a in which a rack is engraved in the circumferential direction. Reference numeral 9 is a DC motor for driving the cam barrel, which is a pinion 9b of an output shaft 9a of the motor 9 for driving the cam barrel.
The rotation output of the motor 9 is transmitted to the cam barrel 2 via the reduction gear train 10 that meshes with the cam barrel gear portion 2a, and the cam barrel 2 rotates. An encoder board 11 provided with a predetermined print pattern is fixed to the fixed barrel 1 near the cam barrel gear portion 2a of the cam barrel 2. A protrusion 2b is provided on the cam body 2 and a brush 12 which is in sliding contact with the encoder substrate 11 is attached to the protrusion 2b.

Next, the cam groove 3 for moving the first lens group and the cam groove 4 for moving the third lens group will be described with reference to FIG. The cam groove 3 for moving the first lens group has a wide focusing portion 3a and the wide focusing portion 3a.
It is composed of three parts, a variable power section 3b continuously provided to 3a and a tele-focusing section 3c continuously connected to the variable power section 3b. Similarly, the cam groove 4 for moving the third lens group also includes a wide focusing portion 4a, a variable power portion 4b continuous with the wide focusing portion 4a, and a telefocusing portion 4c continuous with the variable power portion. It consists of three parts. The end A of the wide focusing portion 3a of the cam groove 3 for moving the first lens unit is an afocal point on the wide side, and the end B of the tele focusing portion 3c is an afocal point on the tele side. As the cam barrel 2 rotates, the first group lens moving cam groove 3
The first group lens frame 7 (the first group lens) having a cam pin 7a that is guided by the first group lens moving cam groove 3 to be engaged with the first group lens moving cam groove 3a.
5a) moves in the optical axis direction (indicated by the arrow). Also, the third
The third lens group frame 8 (third lens group 5c) having the cam pin 8b which is guided by the group lens moving cam groove 4 and engages with the third lens group moving cam groove 4 also moves in the optical axis direction. . Here, the variable power portion 3b of the first group lens moving cam groove 3 and the variable power portion 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. It is selected that the first lens group 5a and the third lens group 5c are moved by a predetermined amount in the optical axis direction from the telephoto lens arrangement to the wide-angle lens arrangement (or vice versa) when 2 rotates. . In addition, the wide focusing portion 3a of the first group lens moving cam groove 3
The focusing portion 3c is inclined with respect to the optical axis direction, and the inclination is selected so that the first group lens 5a moves in an amount necessary for focusing in each lens arrangement. Further, the wide focusing part 4a and the tele focusing part of the cam groove 4 for moving the third lens group.
4c is parallel to the direction of rotation of the cam barrel 2 in FIG. 4, and the third lens group 5c does not move even if the cam barrel 2 rotates. By doing so, the cam barrel 2 is rotated, and wide focusing, zooming, and tele focusing can be continuously performed.

Next, the means (encoder) 13 for detecting the rotation of the cam barrel will be described with reference to FIGS. As shown in FIG. 5, the encoder substrate 11 provided on the fixed barrel 1 is provided with four line-shaped conductive patterns 11a, 11b, 11c and 11d. And these line-shaped patterns 11
On the a, 11b, 11c and 11d, four conductive sliding contact branches 12a, 12b,
The brush 12 having 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 barrel 2 rotates.
Further, the base ends of the sliding contact branches 12a, 12b, 12c and 12d of the brush 12 are connected. Each pattern 11a of the encoder board 11,
Terminals I, II, III and IV are provided at one ends of 11b, 11c and 11d, and these terminals I, II, III and IV are connected to the circuit shown in FIG. The terminal I is connected to the anode of the DC power supply B of V (v) via the terminal a and the 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 FIG. 11 has comb teeth 11e and 11f in the wide focusing area and the tele focusing area. In the present 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 is narrower in the tele focusing area. , 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 that detects where the cam barrel 2 is located, 14 is a range-finding element that detects the defocus direction and defocus amount, for example, using a phase difference detection method, 15
Is a tele / wide magnification switch, 16 is a motor power supply,
Reference numeral 17 is an encoder 13, a distance measuring element 14, and a magnification changeover switch 15.
It is a control circuit that takes in information from the above and controls the motor 9 based on these information. The control circuit 17 controls the motor 9 shown in FIG. 9 in each region. (I)
Is a control method of the motor 9 in the variable power range. 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 range. 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 method of controlling the motor 9 in the tele-focusing range. At this time, the motor 9 is driven at a low speed by the pulse voltage as in the wide focusing range, but since the depth of focus in the telephoto is shallower than that in the wide angle, the duty ratio is made smaller than (b), and the wide focusing is performed. The driving speed is lower than the range to improve the positioning accuracy.

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 to rotate the cam barrel 2 to the in-focus position.

According to the above configuration, since the lens system of the multifocal camera of this embodiment has no sub-optical system, the mechanism is simple, the optical axis adjustment in the manufacturing process is easy, and the F value of the lens at each focus is not so large. It does not change. At the time of product inspection of the camera, the lens is set to an afocal state and the encoder substrate 11 and the first group lens 5a are finely adjusted. In the present embodiment, the first group lens moving cam groove 3 is used. By making both ends of the telescopic side and the wide side afocal point, the afocal point is realized in a state where the cam pin 7a of the first lens group frame 7 is in contact with the end portion of the first lens group moving cam groove 3. It is possible to adjust them accurately and easily. Also, the encoder 13 and the distance measuring element 14
Also, information from the magnification changeover switch 15 is fetched into the control circuit 17, and the motor 9 is controlled based on these information, whereby autofocusing can be realized. Further, the driving speed of the motor 9 can be freely set by using the pulse voltage for driving the motor 9 in the focusing area and the variable magnification area, and the pattern in the focusing area can be set.
By changing the pitch and the number of steps of the comb teeth of the comb teeth 11e and 11f of 11d, the motor 9 can be adjusted according to the focal length of the lens system.
The control method and accuracy of can be changed arbitrarily.

The present invention is not limited to the above embodiment. In the above-mentioned embodiment, focusing has been described by using the bifocal lens 5 in which the first lens group 5a moves along the optical axis, but both the first lens group 5a and the third lens group 5c move to focus. The present invention can be applied to the bifocal lens 5 for performing the above-described operation, if both ends of the third-group lens moving cam groove 4 have afocal points. The fixed barrel 1 is provided with a first group lens moving linear guide groove 1e and a third group lens moving linear guide groove 1f, and the cam barrel 2 is provided with a first group lens moving cam groove 3 and a third group lens. Although the moving cam groove 4 is engraved, conversely, the moving cam grooves of the first lens group and the third lens group are engraved on the fixed barrel 1, and the first lens group and the third lens group are formed on the cam barrel 2. The present invention can be realized even by engraving the moving linear guide groove. Further, 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, the motor 9 is not limited to the DC motor, but may be a stepping motor, for example, or the focusing may be performed manually without using the motor drive. 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, the optical axis alignment adjustment is easy in the manufacturing process, and the F-number of the lens at each focus is too small. It doesn't change,
It is possible to realize a varifocal camera in which various investigations (encoder adjustment, lens fine adjustment, distance measuring device adjustment) at the time of camera product inspection performed in the final process are easy.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIGS. 2 and 3 are views showing the lens arrangement in FIG. 1, and FIG. 4 is a development configuration view of a cam barrel in FIG. FIG. 7 is a plan view of the encoder board in FIG. 1, FIG. 6 is a circuit diagram connected to the encoder board in FIG. 1, and FIG. 7 shows outputs at terminals a, b, and c in FIG. FIG. 8, FIG. 8 is a drive circuit diagram in FIG. 1, and FIG. 9 is a diagram showing motor drive control in each region in FIG. 1-fixed barrel, 1a-main body 1b-second lens group fixed barrel 1c-master lens system fixed barrel 1d-first group lens moving linear guide groove 1e-third group lens movement Straight guide groove for cam 2 …… Cam barrel, 2a …… Cam barrel gear 2b …… Protrusion 3 …… Cam groove for moving 1st lens group 4 …… Cam groove for moving 3rd lens group 5 …… 2 focus lens, 5a ... first lens group 5b ... second lens group, 6 ... diaphragm mechanism 7 ... first group lens frame 7a, 8b ... cam pin 8 ... third group lens frame, 8a ... support section 9 ... Motor, 9a ... Output shaft 10 ... Reduction gear train, 11 ... Encoder board 12 ... Brush, 13 ... Encoder 14 ... Distance measuring element 15 ... Magnification change switch 16 ... Motor power supply, 17 ...... Control circuit

Claims (1)

[Claims] 1. A variable focus camera capable of switching to a plurality of focal lengths by moving a plurality of lenses along an optical axis, wherein a fixed barrel and a cam rotatably supported by the fixed barrel. A barrel and a moving lens frame for holding the plurality of lenses; one of the fixed barrel and the cam barrel is provided with a moving region for switching a focal length, and is continuously provided at both ends of the moving region, The end in the direction of the anti-moving region is composed of two focusing regions having afocal points, and further, a cam groove with which the moving lens frame engages is carved, and on the other hand, the moving lens frame is parallel to the optical axis. A variable focus camera characterized in that a linear guide means for guiding to the camera is provided, and zooming and focusing are performed by rotating the cam barrel.