JPS6118724B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a lens system with a built-in variable magnification lens, more specifically, a lens with a built-in variable magnification lens system having a rotatable turret on which a plurality of variable magnification lenses each having a different magnification are attached. It is related to the system.

In a lens system that includes a rotatable turret equipped with variable magnification lenses, each with a different magnification, such as an extender, the turret is rotated by a servo motor, and the main lens system and the extender with the desired magnification are connected in a coaxial relationship. It is known to be arranged in

In order to arrange the main lens system and the extender in a coaxial relationship with high precision, the precision of the servo system must be sufficiently high. However, a sufficiently accurate servo system has the disadvantage of being expensive.

For this reason, in the lens system of the present invention, a method is adopted in which the turret is rotated by a servo system, and a click mechanism is provided on the turret, and positioning is performed by the click mechanism. However, if this method is adopted,
If a discrepancy occurs between the position determined by the click mechanism and the position determined by the servo system, the turret rotation force generated by the servo system is naturally greater than the turret rotation stopping force generated by the click mechanism, so the turret rotation force generated by the servo system is naturally larger. The position is determined by the position.

The present invention has been made in consideration of this point, and therefore, an object of the present invention is to provide a variable magnification system in which a turret is rotationally driven by a servo system, and the stopping position of the turret is accurately determined by a click mechanism. To provide a lens system with a built-in lens that includes a variable power lens that smoothly stops a turret at a position determined by a click mechanism with a predetermined gain.

This objective is achieved by expanding the dead area of the servo system when the turret is click-locked.

Before explaining the present invention, a conventional example will be explained using the attached drawings.

1 and 2 are diagrams showing a conventional lens with a built-in variable magnification lens using a servo motor. FIG. 1 is a top view of the lens portion, and FIG. 2 is a servo circuit. In Figure 1, 1 is a focusing lens, 2
is a variator lens, 3 is a compensator lens, 4 is an erector lens, and 5 is a relay lens. These lenses are movably or fixedly held by a lens barrel 6. 7 is a turret. This turret 7 is rotatably mounted to the lens barrel 6 about a rotating shaft 8. 9
are fixed so that the optical axis is located on the same circle around the rotation axis 8 of the turret 7.
It is a double extender lens.

Reference numeral 10 denotes a gear provided on the outer periphery of the turret, and this gear 10 meshes with a gear 12 of a motor 11. Furthermore, this gear 10 meshes with a gear 14 of a potentiometer 13 which generates a rotational position signal for the turret 7. The output of this potentiometer 13 is input to a comparator 15 as shown in FIG. 16, 17, 18 are equal size, 1.5 times, 2
This is an instruction potentiometer that generates an instruction signal for selecting a lens with a magnification. 19 is a selection switch. The instruction signal is input to the other terminal of the comparator 15 via the selection switch 19. The difference between the turret rotational position signal and the instruction signal is input to the motor 11 as an analog value.
rotates until the output of the comparator 15 disappears. 20 is a tachogenerator which generates an inverse signal to the rotation of the motor 11, and which generates an inverse signal to the adding circuit 2.
If we add this inverse signal and the instruction signal by 1, we get
The rotation of the motor becomes almost uniform.

In such conventional examples, the positioning of the turret is 100% dependent on the accuracy of the servo system, so the servo system must be highly accurate.

In the present invention, a click mechanism is used for positioning the turret.

Embodiments of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows the turret 7 section. A click mechanism is formed by a click groove 21 provided on the turret 7 and a tension roller 22 provided on the lens barrel 6. FIG. 4 is a circuit diagram of the servo system. This circuit differs from the circuit shown in FIG. 2 in that a gain switching circuit 23 is formed in the comparator 15. That is, when the switch 24 of the gain switching circuit 23 is connected to the terminal 25, a comparison output with a low amplification rate is obtained, and when it is connected to the terminal 26, a comparison output with a high amplification rate is obtained. Further, a switch 27 is arranged between the motor 11 and the comparator 15. 28 is a relay which closes the switch 27 when there is a large comparison output;
is connected to terminal 26.

Next, the operation will be explained. In FIG. 4, the selection switch 19 is connected to the command potentiometer corresponding to the same magnification, the switch 27 is open, and the switch 24 is connected to the terminal 25. This state indicates that the same magnification extender has been selected and is stable in this state. If a 1.5x extender is desired from this state, the selection switch 19 is connected to the command potentiometer 17. Since the difference between the turret rotational position signal from the potentiometer 13 and the instruction signal from the command potentiometer 17 is large, the comparator 15 produces a high output even at a low gain. This output activates relay 28, connecting switch 24 to terminal 26 and closing switch 27. Therefore, the motor 11 rotates. As the motor 11 rotates, the difference between the output of the potentiometer 13 and the output of the command potentiometer 17 narrows. When the tension roller 22 melts into the click groove 21, the difference in output almost disappears. Therefore, the comparison output of comparator 15 becomes small. This stops the operation of relay 28, opens switch 27, and connects the gain changeover switch to terminal 25. Therefore, the motor stops and the turret is held by the click mechanism. or,
Since the comparison output is greatly reduced due to gain switching, the dead area of this servo system is large. Yometer 13
Even if a slight difference in output occurs, the motor 11 will not operate and a stable state will be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams explaining a lens system with a built-in variable magnification lens using a conventional servo method. Figure 1 is a top view, Figure 2 is a servo circuit diagram, and Figures 3 and 4 are in accordance with the present invention. 3 is a diagram showing the turret part, and FIG. 4 is a servo circuit diagram. In the figure, 11...turret drive motor, 13
...Turret position detection potentiometer, 1
5... Comparator, 16, 17, 18... Potential for extender selection, 21... Click groove, 2
2... tension roller, 23... gain switching circuit, 27... switch, 28... relay.

Claims (1)

[Scope of Claims] 1. A variable power lens built-in lens system having a rotatable turret on which a plurality of variable power lenses each having a different magnification are mounted, wherein the turret is held at multiple rotational positions by a click mechanism, The rotation from the click hold at the rotational position to the rotation at other rotational positions is performed by a motor for rotating the turret, and the motor is controlled by a means for generating a rotational position signal corresponding to the rotational position of the turret and a lens corresponding to the selected lens. a comparator for comparing the respective outputs of the means for generating the selection instruction signal; a switch connected between the motor and the comparator; and a gain switching circuit for switching the amplification rate according to the comparison output of the comparator. A lens system with a built-in variable magnification lens, characterized in that the switch is opened and closed by the gain switching circuit.