JPS58224318A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To perform limit detection conforming to various lenses easily by obtaining a focusing lens position in the form of an electric detection signal, and reducing signals from movable parts and detecting the lens position. CONSTITUTION:Pulse control signals for driving the motor 4 in a lens is inputted from a camera side to terminals 1 and 2. The position detection signal of a focusing lens 5 is transmitted from a terminal 3 to the camera. A brush 6 moving according to the movement of the lens 5 moves on an electrode pattern 8 to generate a pulse waveform 9 with a contact 9, and both brushes 11 and 12 for short distance and long distance are provided and contact electrodes 13 and 16 to generate a low potential signal L. One input terminal of an AND gate 28 is connected to the connection point 9 and as the lens 5 moves within an interlocking range, a pulse signal is sent to the terminal 3 and inputted to a distance measuring device to calculate the distance to the focusing point, e.g. defocusing extent, pulse by pulse, every time the lens 5 moves, thereby using it as a signal for deciding on whether the lens 5 should be moved or not.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focusing device, and more particularly, it is possible to determine the current position of the focusing lens, that is, whether the focusing lens is at the telephoto end or the close end, from a distance measuring device. For example, a position that can be linked with a so-called ranging signal that detects the amount of defocus, and according to the amount of defocus, is sent out in the telephoto direction or the close-up direction by a driving means such as a motor, and can be moved to the in-focus position. To provide an automatic focusing device that determines whether the object is within the range, transmits the determined signal to a distance measuring device, especially a device that generates a focusing lens movement signal, and enables quick focusing operation.

TTL - When a photographic system consisting of an eye reflex camera and an interchangeable lens is equipped with a TTL automatic focusing distance measuring device on the camera side, and automatic focusing is performed by transmitting a movement signal for the focusing lens from the camera side to the lens side. The position of the focusing lens is detected and a detection signal is sent to the camera side.The camera side determines in which direction the focusing lens should be moved based on the detection signal, and then moves the focusing lens based on that determination. Movement needs to be controlled.

In the case of the above-mentioned system, the number of terminals for simultaneously receiving and receiving signals between the camera and the lens increases, which causes structural design problems and cost problems. Furthermore, as the number of terminals increases, quality and performance constraints also occur.

The above-mentioned problem also applies to the number of signal lines that send signals for detecting the position of the focusing lens to a device that detects the position of the focusing lens within the lens barrel, such as a logic circuit.

The present invention is proposed to solve the above-mentioned problems. In particular, it is an object of the present invention to provide a device capable of detecting the position of the focusing lens by using an electric signal as a detection signal for the position of the focusing lens and minimizing the signal from the movable part of the focusing lens.

In particular, the present invention relates to the lens position detection of the invention related to the lens control method disclosed in Japanese Patent Application No. 205786 of 1982, which was previously filed by the present applicant.

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, numerals 1, 2, and 3 indicate electrical contacts or terminals for receiving and receiving signals between the camera side and the lens side, and the terminals 1 and 2 are used to send control signals from the camera 2 side to drive the motor 4 in the lens, for example. Input pulse signal. A signal for detecting the position of the focusing lens is transmitted from a terminal 6 to the camera side using a signal from a circuit described later.

5 is a focusing lens that is moved along the optical axis direction by a lens 4; Reference numeral 6 denotes a brush member that moves with the movement of the focusing lens, one end 7 of which is grounded, and a comb-shaped electrode pattern 8 whose pusher portion is fixed in the optical axis direction inside a fixed barrel of a lens barrel (not shown). , and one end of the electrode pattern 8 is connected to a pull-up resistor 10 via a connection point 9. When the brush 6 slides on the electrode pattern 8, a constant pulse waveform is output to the contact 9 by repeating on/off spring on/off 011. 11 and 12 are brushes fixed on the brush member 6 for detecting the close end and for detecting the telephoto end;
- 12 is constructed so as to be able to contact close-up and telephoto electrode portions 13-1<5 attached to a fixed tube (not shown). When the focusing lens 5 moves to the close end, the electrode 15 and the brush 11 are connected, and an electrical logic low potential signal is generated at the input terminal of the °C inverter gate via the signal line 14 and the pull-up resistor 15. Also, when the focusing lens 5 reaches the infinity end, the brush 1
2゜Terminal wire 17 by electrode 16 and pull-up resistor 18
Outputs an L signal to When the focusing lens 5 is within the range where the focusing operation can be performed, the inverter gates 19 and 20 are in the L position.
It becomes a signal. As a result, AND gate 21/22-2
! 1.2゛4 is closed and the OR gate 25 becomes an L signal, resulting in the output of the OR gate 25 and the pulse generator 6.
The AND gate 26 with the output of 6 also becomes an L signal.

Further, the NOR gate 27 outputs an H signal, and the CAND gate 2B outputs an H signal. The other input terminal of the AND gate 28 is connected to the connection point 9, so that when the focusing lens 5 moves within the above-mentioned interlockable range, a pulse signal corresponding to the movement is outputted to the terminal 6. Therefore, when the focusing lens 5 is within the interlocking range by this signal, this signal is introduced into the distance measuring device, and each time the focusing lens moves one pulse at a time, the position of the focusing lens 5 and the distance to the in-focus point are determined, e.g. It can be used as a signal to calculate the defocus amount and further determine whether to move the focusing lens 5 or not.

Inverter A30.66 and AND gate 31-! +4
is a circuit for discriminating the moving direction of the focusing lens 5;
Inverter when driving the focusing lens 5 towards infinity! 10 and and gate! H to connection point 62 by +1
An output signal is output, and when driving in the close direction, an H output signal is output to the connection point 35 by the inverter 6 and antagonist 54.

When the focusing lens 5 is at the close end and the output from the distance measuring device is such that no focusing signal is detected, the lens 5 must be driven toward infinity. In this case, the push 1 mentioned above
It is necessary to change the driving direction of the focusing lens 5 after a certain period of time has elapsed after the focusing lens 5 outputs a signal indicating the infinite position by the circuit including the 111 electrode 1'5 and the resistor 15.

The problem in this case is that when the focusing lens 5 reaches the infinity position, it is necessary to quickly switch the driving direction of the focusing lens to the close-up direction. Therefore, the present invention has the above-mentioned reference numerals 11-13 and 1.
Circuit configured in 4, 15, 19 and 12-16-17
The position of the υ focusing lens 5 is accurately detected by generating an electric signal indicating that the focusing lens is at the close end or the infinite end using the circuit 18-20.

FIGS. 2A and 2B show the comb-teeth electrode 8 in the lens barrel shown in FIG. 1. An example of a lens barrel having a brush 6 is shown,
The lens barrel has a helicoid 40 at one end of the lens barrel.
a, and the helicoid 4 screwed with the helicoid 40 &
The comb electrode 8 is fixed to the outer circumferential surface of the fixed tube 40, and the brush and ground terminal 7 are attached to the inner circumference of the focusing tube 42. The electrode C provided on the outer periphery of the fixed tube 40 is connected to the ground shown in FIG. 1 by means of one turn for grounding.

On the infinite side, the 16 electrode patterns are grounded,
On the closest side, 16 patterns are grounded.

As described in detail above, the present invention eliminates the above-mentioned inconveniences associated with the provision of conventional mechanical switches, and is extremely advantageous in terms of lens drive control and control circuitry. , it becomes possible to easily perform limit detection suitable for each of various lenses, and is useful for devices that need to know the limit when moving a lens within a predetermined range, especially automatic focus adjustment devices (especially automatic focus adjustment devices). This is extremely useful in applications where lens-related signals are formed in the form of lens related signals.

In addition, as an example of a means for generating lens-related signals (pulses), a mechanical contact method using a brush and a comb-teeth electrode is shown in the embodiment, but of course, in addition to this, a photo interrupter, an electromagnetic Non-contact formats such as a virtual surprise are also fully applicable.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 2A@B is a diagram showing an embodiment showing the arrangement of each electrode and brush provided on the lens barrel. 1, 2, 6...Signal terminal 4 on the lens mirror ■ side...
Fist/motor 5... Focusing lens 6, 11, 1
2-...Brush 8, fist that moves together with the focusing lens...
・Electrode pattern for generating pulses according to the movement of the focusing lens Applicant: Canon Corporation

Claims (2)

[Claims] (1) In a focusing device that moves a focusing lens based on an electrical signal, the moving direction of the focusing lens is determined by a first electrical signal indicating that the focusing lens is within a focusing range; An automatic focusing device characterized in that the automatic focusing device is controlled by a second electrical signal indicating that the focusing device is outside the focusable range. (2) A signal for controlling the moving direction of the focusing lens is transmitted to the first focusing operation member of the lens barrel including the focusing lens.
and at least a part of the constituent elements of the means for generating the second electric signal are arranged.
The automatic focusing device described in section 1).