JPH04270902A - position detection device - Google Patents

Abstract

PURPOSE:To obtain a position detector which is small in change with lapse of time and hardly affected by noise. CONSTITUTION:A plurality of the first electrodes 2 are arranged at certain intervals on a base cylinder 1 which is a fixed member. The second electrodes 6 are arranged in corresponding to the electrodes 2 on the third-group lens frame 3 which is a mobile member. The position of the lens frame 3 against the cylinder 1 is detected on the basis of the presence/absence of the capacitance of the capacitor formed of the first and second electrodes 2 and 6.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a position detection device that includes a fixed member such as a lens barrel and a movable member that moves relative to the fixed member.

0002

2. Description of the Related Art When automation is performed in a device equipped with a movable member, such as an automatic focusing device, a device for detecting the position of the movable member with respect to a fixed member is incorporated. Conventionally, as this type of device, a photocoupler type, a photointerrupter type, a potentiometer type, a gray scale type, etc. are commonly used.

However, the above-mentioned photocoupler method,
The photointerrupter method has disadvantages in that the light emitting element must be turned on at all times, resulting in high power consumption and an increase in the size of the device. Furthermore, the aforementioned potentiometer type and gray scale type require movable contacts, which poses a problem in durability.

0004

[Problems to be Solved by the Invention] In view of this point, Japanese Patent Laid-Open No. 62-262009 proposes a device that detects changes in the position of a movable member relative to a fixed member by continuous changes in capacitance. . According to this device, it is possible to reduce power consumption and prevent the device from becoming larger.
Furthermore, the structure is such that there is no problem in terms of durability.

However, in the above proposed device that detects position information by looking at continuous changes in capacitance, there is a decrease in accuracy due to the influence of changes in capacitance over time, and noise and stray capacitance in the circuit. The problem was that the capacitance was easily affected by changes in capacitance due to temperature, humidity, etc.

SUMMARY OF THE INVENTION In view of the above points, an object of the present invention is to provide a position detection device that is less susceptible to changes over time and noise and has good environmental resistance.

[0007]

[Means for Solving the Problems] The present invention provides a plurality of first electrodes arranged at intervals on one of a fixed member and a movable member, and a plurality of first electrodes arranged on the other member at intervals. at least one second electrode disposed opposite the electrode;
The apparatus further includes position detection means for detecting the position of the variable member relative to the fixed member based on the presence or absence of capacitance of at least a pair of capacitors formed by the first electrode and the second electrode.

[0008]

[Operation] When the movable member moves, the first and second electrodes face each other to the front, creating capacitance, and the first and second electrodes are shifted and face each other, so no capacitance is created. , two states are created, and the position detecting means detects these two states to detect the position of the movable member with respect to the fixed member.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 4 show an embodiment of the present invention, in which the present invention is incorporated into a video camera.

In FIG. 1, a fixed electrode 2 is attached to a cylindrical base tube 1, which is a fixed member, and an imaging device such as a CCD is attached to the rear of the base tube 1. Reference numeral 3 denotes a fourth group lens frame, which is a movable member that holds fourth group lenses 4 and 5, which moves in the optical axis direction and focuses when the rotational output of a focus motor, which will be described later, is transmitted. perform an action. A movable electrode 6 is provided on the fourth group lens frame 3, and as described later, by facing the fixed electrode 2, electrostatic capacitance is generated. The third group lens frame 7 is the third group lens 8
, 9, and 10, and has an integral structure with the base tube 1. The aperture device 11 has the function of adjusting the aperture diameter by rotating blades 12 by receiving the rotational output of an iris motor (not shown).

The fixed lens barrel 13 has a helicoid cut out, and the first group lens outer frame 14 also has a helicoid cut out.
is engaged with. The first group lens inner frame 15 has an integral structure with the first group lens outer frame 14, and when the first group lens outer frame 14 rotates by transmitting rotational output from the zoom motor described later, the first group lens outer frame 15 rotates. The first group lenses 16, 17, and 18 held by the lens inner frame 15 move in the optical axis direction. Further, the cam ring 19 rotates in conjunction with the first group lens inner frame 15, and the second group lenses 21, 22, 2 held in the second group lens frame 20
3 is moved in the optical axis direction in conjunction with the first group lenses 16, 17, and 18 to change the magnification. A fixed electrode 24 is provided on the fixed lens barrel 13, which is a fixed member, and a movable electrode 25 is provided on the first group lens inner frame 15, which is a movable member. By opposing each other, a capacitance is generated.

FIG. 2 is a perspective view showing the base tube 1 and the fixed electrode 2, which are the fixed members, and the fourth group lens frame 3 and the movable electrode 6, which are the movable members.

As mentioned above, the fixed electrode 2 is installed inside the base tube 1.
a to 2f are provided, and movable electrodes 6a to 6c are provided on the outside of the fourth group lens frame 3.

In such a configuration, as the fourth lens group frame 3 moves, one of the fixed electrodes 2a to 2f and the movable electrodes 6a to 6c face each other, thereby forming a pair of capacitors C and static electricity. Capacitance is generated, and if the positions are shifted, no capacitance is generated.

FIG. 3 is a perspective view showing the fixed lens barrel 13 and the fixed electrode 24, which are the fixed members, and the first group lens frame 15 and the movable electrode 25, which are the movable members.

A rectangular fixed electrode 24 is provided inside the fixed lens barrel 13, and a rectangular movable electrode 25 is provided outside the first group lens frame 15.

In such a configuration, as shown in FIG.
As the first group lens frame 15 rotates, the fixed electrode 24 and the movable electrode 25 face each other, forming a pair of capacitors C and generating capacitance, and if they are misaligned, capacitance will occur. do not have.

FIG. 4 is a block diagram showing the general configuration of a video camera, and the two types of condensers C configured as described above are connected to the zoom lens position reading device 10 shown in the figure.
1 and a focus lens position reading device 102, and the information of these devices 101 and 102 is output to the CPU 104 together with the information from the automatic focusing device 103.

In FIG. 4, when the main switch 105 is turned on, the power-on reset circuit 106 initializes each section. When the zoom switch 107 is then pressed, the CPU 104 outputs the zoom information selected at this time to the zoom motor driver 108, and the zoom motor driver 108 adjusts the zoom mode based on this zoom information. - Operate the computer 109. Further, when focus information is input from the automatic focusing device 103, the CPU 104 outputs this focus information to the focus motor driver 110, and the focus motor driver 110 adjusts the focus motor based on this focus information. 111 is activated.

The storage device 112 stores information related to various controls, and the CPU 104 uses the information from the zoom lens position reading device 101, automatic focusing device 103, and focus lens position reading device 102 to read information from the storage device 112. Necessary information is read from 112 and the above-mentioned control etc. are performed.

FIG. 5 shows a zoom lens position reading device 101.
and the configuration of the focus lens position reading device 102.

A square wave is inputted from the square wave generating circuit 151 via the resistor R to the capacitor C having two types of electrodes described above, which acts as a position sensor. The capacitor C and an external resistor R constitute an L-shaped circuit 152 as shown in the figure, and if the capacitor C has a capacitance, it serves as a differential circuit, and if it does not, it serves as a series resistor. It has become.

[0023] When capacitor C has a capacitance,
The square wave from the square wave generating circuit 151 is differentiated into a narrow impulse. This is rectified by the half-wave rectifier circuit 153 so as to serve as a trigger for the pulse generation circuit 154, and the pulse generation circuit 154 generates a pulse as a trigger. The number of generated pulses is counted by a pulse counting circuit 155, and the information is output to the CPU 104. Furthermore, if the capacitor C has no capacitance, the square wave is directly applied to the half-wave rectifier circuit 153, but the circuit is configured so that it does not trigger the pulse generation circuit 154 when it is rectified.

Note that the signal input to the pulse generation circuit 154 may be any signal that causes the pulse generation circuit 154 to output a pulse depending on the two states of the electrodes forming the capacitor, and is not necessarily a signal as shown in FIG. It doesn't have to be the composition. Also, even if pulses are not generated depending on the two conditions,
Any configuration may be used as long as the number of cases in that state can be counted.

As described above, by detecting the presence or absence of capacitance and counting the number of times this state is maintained, the location where the electrodes have moved from the width of the equally spaced electrodes of the same width and the counted number of times can be determined. The relative position from the reference position can be detected.

By doing as described above, the base cylinder 1 and the fourth
The position sensor can be incorporated into the group lens frame 3, the fixed lens barrel 13, and the first group lens inner frame 15 in a natural manner, and
Non-contact power saving, detecting only the presence or absence of capacitance.
Moreover, it is possible to obtain a position sensor that is less susceptible to noise and changes over time and has good environmental resistance.

Furthermore, each electrode can be easily formed by forming a conductive thin film on the inner or outer surface of the lens barrel and then cutting the insulating part, or by selectively growing a conductive thin film. Can be done. Furthermore, if an insulating high dielectric constant film is formed on top of the conductive thin film, there is no need for short circuiting even if the electrodes come into contact due to eccentricity, etc., and the capacitance increases, thereby improving detection accuracy.

According to this embodiment, electrodes are arranged at predetermined intervals on the inside of the fixed member, electrodes are arranged at predetermined intervals on the side of the movable member opposite to the electrodes, and the movable member relative to the fixed member is arranged at predetermined intervals. The position of the electrodes is detected by the number of pulses generated when the electrodes face each other and generate capacitance, which reduces accuracy due to changes in capacitance over time and reduces noise and noise. It is possible to obtain a position detection device that is less susceptible to the effects of stray capacitance of the circuit, as well as ambient temperature and humidity.

In particular, when it is incorporated into an optical system such as a video camera, it has the advantage of good consistency, allowing the overall volume to be reduced, being less affected by eccentricity, and being resistant to vibrations.

(Modification) In this embodiment, the device is incorporated into a video camera, but it may be used in other optical systems such as a silver halide camera. Further, the fixed member and the movable member may be combined with either the inner or outer member.

Furthermore, although the fixed electrode and the movable electrode in this embodiment have the same spacing, if the two states of capacitance and non-capacitance occur as the object moves or rotates, the fixed electrode and the movable electrode The movable electrodes may be arranged at different intervals by methods such as making the fixed electrodes an integral multiple of the movable electrodes, or making the fixed electrodes a reciprocal of the integer of the movable electrodes, and the number can also be controlled at a fixed position. In this case, they may be arranged on a one-to-one basis, and may be configured in any manner.

[0032]

[Effects of the Invention] As explained above, according to the present invention,
A plurality of first electrodes arranged at intervals on one of the fixed member and the movable member, and a plurality of first electrodes arranged on the other member,
Presence or absence of capacitance of at least one second electrode disposed opposite to the first electrode, and at least one pair of capacitors formed by the first electrode and the second electrode facing each other. and a position detecting means for detecting the position of the variable member relative to the fixed member based on the movable member. When the movable member moves, the first and second electrodes face each other to generate capacitance, By creating two states in which capacitance does not occur by displacing and facing the second electrode, and
The position of the movable member relative to the fixed member is detected by the position detecting means detecting two states. Therefore, it is possible to provide a position detection device that is less susceptible to changes over time and noise and has good environmental resistance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical system when an apparatus according to an embodiment of the present invention is incorporated into a video camera.

2 is a perspective view showing the shapes of two types of electrodes constituting a position sensor attached to the focus optical system of FIG. 1; FIG.

3 is a perspective view showing the shapes of two types of electrodes constituting the position sensor attached to the zoom optical system of FIG. 1. FIG.

FIG. 4 is a circuit block diagram showing the configuration of a video camera incorporating an embodiment of the present invention.

[Fig. 5] Zoom lens position reading device and form in Fig. 4.
It is a block diagram showing an example of composition of a cast lens position reading device.

[Explanation of sign]

1 Base barrel 2, 6 Electrode 3 Fourth group lens frame 13 Fixed lens barrel 15 First group lens frame 24, 25 Electrode 101 Zoom lens position reading device 102 Focus lens position reading device 104 CPU 151 Square wave generation circuit 152 L Type circuit 153 Half-wave rectifier circuit 154 Pulse generation circuit 155 Pulse counting circuit C Capacitor R Resistor

Claims (4)

[Claims] 1. A fixed member, a movable member that moves relative to the fixed member, and a plurality of first movable members disposed at intervals on one of the fixed member and the movable member. at least one second electrode disposed on the other member opposite to the first electrode, and at least one pair of capacitors formed by the first electrode and the second electrode. a position detecting device that detects the position of the variable member relative to the fixed member based on the presence or absence of capacitance of the variable member. 2. The movable member is a member that moves in a linear direction with respect to the fixed member, and the movable member is a member that moves in a linear direction with respect to the fixed member.
2. The position detection device according to claim 1, wherein the arrangement direction of the capacitors formed by the electrodes is a linear direction that is the moving direction of the movable member. 3. The cylindrical movable member is a member that moves in the circumferential direction with respect to the cylindrical fixed member, and an array of capacitors is formed by first and second electrodes arranged on these members. 2. The position detection device according to claim 1, wherein the direction is a circumferential direction, which is a moving direction of the movable member. 4. Claim 12, wherein the fixed member and the movable member are part of a lens barrel in an optical system.
Or the position detection device according to 3.