JPH045176B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a focus adjustment device for an autofocus camera capable of manual focus adjustment.

2. Description of the Related Art Conventionally, some cameras that perform manual focus adjustment are provided with display means that lights up, such as a light-emitting display element, in the viewfinder to inform the photographer that the focus is on. However, with such cameras, the photographer's eyes cannot concentrate on the subject image in the viewfinder, and there is a time lag between checking the focus display and stopping manual adjustment. There was a problem that I said was unavoidable.

Therefore, proposals for solving the above-mentioned problems have been made in Japanese Patent Application Laid-Open No. 159620/1982 and US Pat. No. 4,314,750. These proposals disable or suppress the movement of the focusing ring by driving a magnet or the like during focusing, so that focusing can be perceived intuitively. However, there is a problem in that a new means for disabling or suppressing the movement of the focusing ring is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus adjustment device for an autofocus camera that solves the above-mentioned problems and can intuitively notify a photographer of focus during manual focus adjustment by making slight circuit changes. be.

In order to achieve the above object, the present invention includes a focus detection circuit that detects a focus state and selectively outputs a focus signal, a rear focus signal, or a front focus signal according to the focus state; In response to the focus signal, an energizing path is formed from the first terminal to the second terminal for the photographic lens driving motor to rotate the motor in the forward direction, and in response to the front focus signal, the current is connected to the motor. an energization control circuit that forms an energization path from the second terminal toward the first terminal to reverse the motor, and cuts off the energization path to the motor in response to the focus signal; and a brake closed circuit that forms a bidirectional closed circuit in parallel with the motor, and a focus adjustment device for an autofocus camera that automatically adjusts the focus. A manual focus control circuit is provided that prohibits responses to the rear focus signal, front focus signal, and focus signal and maintains the energized path in a cut-off state, and this controls the focus detection circuit and the brake closed circuit during manual focus adjustment. The focus adjusting device for an autofocus camera is configured such that when the motor is activated, the motor acts as a generator in the focusing area to apply a brake during manual focus adjustment.

In the embodiment described below, the distance measuring device 1 and the comparators 12 and 13 correspond to the focus detection circuit of the present invention, the motor 2 corresponds to the photographic lens driving motor, and the transistors 18 to 21 correspond to the energization control circuit. It is assumed that transistors 24 and 25 correspond to a brake closed circuit, and AND gates 6 and 7, manual selection switch 3, and pull-up resistor 4 correspond to a manual focus control circuit.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

1 and 2 show an embodiment of the present invention, in which FIG. 1 is a circuit diagram and FIG. 2 is a schematic connection diagram in FIG. 1. Reference numeral 1 denotes a distance measuring device which outputs a distance measuring signal that is an analog value of a positive voltage when the front side is out of focus, zero when in focus, and a negative voltage when the rear side is out of focus. 2 is a motor, 3 is a manual selection switch that is turned on during manual adjustment, 4 is a pull-up resistor, 5 is a signal line, 6 and 7 are AND gates, 8 is a distance measuring device 1
The signal lines 9, 10, and 11 are voltage dividing resistors, and the potential at the voltage dividing point a of the voltage dividing resistors 9 and 10 is input to the inverting input terminal as the reference voltage of the comparator 12, and the voltage dividing resistors 9, 10, and 11 are voltage dividing resistors. Piezoresistor 10 and voltage dividing resistor 11
The potential at the voltage dividing point b is inputted to the non-changing input terminal of the comparator 13 as a reference voltage. 14, 15 are output lines from comparators 12, 13, 16,
17 is the output line from AND gates 6 and 7, 1
8 to 21 are transistors, 22 and 23 are inverters, 24 and 25 are transistors, and 26 and 27 are connection terminals for the motor 2. The potentials at the voltage dividing points a and b are set to potentials corresponding to the upper and lower limits of the focusing range, respectively.

Next, the operation will be explained. During automatic focus adjustment, since the manual selection switch 3 is off, the potential of the signal line 5 becomes high level through the pull-up resistor 4, and is input to the AND gates 6 and 7.

Assuming that the front side is now out of focus, the distance measurement device 1 outputs a distance measurement signal with a positive voltage corresponding to the degree of defocus, and inputs it to the comparator 12 via the signal line 8. Since this ranging signal is higher than the potential at the voltage dividing point a, the output of the comparator 12 becomes high level, and the output of the comparator 13 becomes low level. Since a high level signal is input from the signal line 5 to the AND gate 6, the output of the AND gate 6 becomes a high level and the transistor 18
is on, transistor 19 is off, and the output of AND gate 7 is at a low level, so transistor 21 is on and transistor 20 is off.
When the transistors 18 and 21 are turned on, a current flows from the connection terminal 26 to the connection terminal 27, the motor 2 starts rotating, and focus adjustment is performed in the focusing direction. Also, output line 1
The high-level potential of output line 15 passes through the inverter 23 and turns off the transistor 25, and the low-level potential of the output line 15 passes through the inverter 12 and turns on the transistor 24, so that the back electromotive force generated when the motor is reversed manually is passed. and the transistor 18,
21 can be protected. That is, the circuit connected to the motor 2 is as shown in FIG. 2A.

At the time of focusing, the potential of the signal line 8 is approximately zero, so the outputs of the comparators 12 and 13 are both low level, and therefore the AND gates 6 and 7
Since the output of transistor 1 also becomes low level,
Since transistors 8 and 20 are turned off and transistors 19 and 21 are turned on, no driving voltage is supplied to connection terminals 26 and 27. However, since the potentials of the output lines 14 and 15 are at low level, the inverters 22 and
The output from 23 is inverted to a high level, transistors 24 and 25 are turned on, and a bidirectional signal is generated, which is equivalent to connecting bidirectional diodes in parallel between connecting terminals 26 and 27 of motor 2, as shown in FIG. 2B. A closed circuit is formed. As a result, the motor 2 works as a generator, and when the brake is applied, the motor 2
stops.

When the rear side is defocused, the transistors 19 and 20 are turned on, contrary to when the front side is defocused, and the transistors 18 and 21 are turned on.
is turned off, the connection terminal 27 to the connection terminal 26
A current flows in the direction, and the motor 2 rotates in the focusing direction. Further, the transistor 25 is turned on via the inverter 23, which passes the back electromotive force generated when the motor is reversed manually, etc., and the transistor 19,
20 can be protected. That is, the circuit connected to the motor 2 is as shown in FIG. 2C.

Next, when adjusting the focus manually, use the manual selection switch 3.
By turning on the signal line 5, the potential of the signal line 5 becomes low level, the AND gates 6 and 7 are closed, and the drive voltage is not supplied to the connection terminals 26 and 27.

However, since the ranging signal output from the ranging device 1 changes, the outputs of the comparators 12 and 13 also change, and the transistors 24 and 25 are turned on or off via the inverters 22 and 23. That is, when the front side is defocused, the output of the comparator 12 is at a high level, so the transistor 25 is turned off via the inverter 23, and the output of the comparator 13 is at a low level, so the transistor 24 is turned on via the inverter 22. As a result, a one-way closed circuit is formed with the transistor 24 for the motor 2, as shown in FIG. 2D. When the lens is moved in the focusing direction by manual focus adjustment, the motor 2 is thereby rotated, but since the transistor 25 is turned off, the motor 2 cannot work as a generator, and the motor 2 becomes a mere rotating load. Rotate lightly. Therefore, for the photographer, manual focus adjustment in the focusing direction feels light. When the lens is moved in the defocusing direction, the motor 2 acts as a generator due to the one-way closed circuit formed by the transistor 24, and a brake is applied.
Therefore, manual focus adjustment in the defocusing direction feels burdensome to the photographer.

When in focus, the outputs of the comparators 12 and 13 are both low level, and the transistors 24 and
25 is turned on and a bidirectional closed circuit for braking is formed for the motor 2 as shown in FIG. 2E, so that the motor 2 acts as a generator for movement of the lens in either direction. Apply the brakes,
Makes the photographer feel that the camera is in the in-focus area.

When the rear side is defocused, the output of the comparator 13 is at a high level and the output of the comparator 12 is at a low level, so the transistor 24 is turned off and the transistor 25 is turned on. As a result, Figure 2 F
As shown in , a one-way closed circuit for braking is formed for the motor 2, making manual focus adjustment in the in-focus direction light and manual focus adjustment in the defocusing direction heavy.

According to this embodiment, by adding the manual selection switch 3, pull-up resistor 4, AND gates 6, 7, inverters 22, 23, and transistors 24, 25, the lens driving motor 2 can also be used as a braking means. It is possible to intuitively notify the photographer of focus during manual focus adjustment at low cost. Furthermore, the transistors 18 to 21 can be protected during automatic focus adjustment. In addition, we made the brake directional by making the adjustment light in the direction of focus and heavier in the direction of defocusing, so even if the width of the focus range is narrow, it is easy to achieve focus by reciprocating adjustment. be able to.

In this embodiment, it is more effective for the transistors 24 and 25 to be elements or circuits with as little forward voltage drop as possible, and it goes without saying that it is more effective to use equivalent diodes or the like using a feedback system using an operational amplifier or the like. . Also, transistor 1
It goes without saying that if transistors 8 to 21 have opposite polarities using an inverter, the power supply voltage can be converted into driving force without loss, and duty control etc. can also be applied to this driving. Furthermore, in this embodiment, the manual focus adjustment in the in-focus area and the manual focus adjustment in the defocusing direction are braked, but the brake may be applied only in the in-focus area. In this case, inverter 2
The transistors 24 and 25 are controlled to be turned on and off at the same time by an AND gate that receives the outputs of the transistors 2 and 23 as inputs.

As explained above, according to the present invention, during manual focus adjustment, the energization control circuit prohibits the response to the rear focus signal, the front focus signal, and the focus signal,
A manual focus control circuit is provided to keep the energized path in a disconnected state, and this activates the focus detection circuit and brake closed circuit during manual focus adjustment, and operates the motor as a generator in the focusing area to apply the brake. This allows the photographer to be intuitively informed of focus during manual focus adjustment by making a slight circuit change.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is a schematic connection diagram showing the motor connection circuit in FIG. 1. 1...Distance measuring device, 2...Motor, 3...Manual selection switch, 6, 7...And gate, 9-11
...Voltage dividing resistor, 12, 13...Comparator, 1
8-21...Transistor, 22, 23...Inverter, 24, 25...Transistor, a, b...
...Partial pressure point.

Claims (1)

[Scope of Claims] 1. A focus detection circuit that detects a focus state and selectively outputs a focus signal, a rear focus signal, or a front focus signal according to the focus state, and a photographing lens in response to the rear focus signal. An energizing path is formed for the drive motor from the first terminal to the second terminal to cause the motor to rotate forward, and in response to the front focus signal, an energizing path is formed for the motor from the second terminal to the first terminal. an energization control circuit that forms an energization path toward the terminal of the motor to reverse the motor, and cuts off the energization path to the motor in response to the focus signal; A focus adjustment device for an autofocus camera that automatically adjusts the focus and has a brake closed circuit forming a bidirectional closed circuit at the rear focus signal and the front focus signal of the energization control circuit during manual focus adjustment. and a manual focus control circuit that prohibits response to a focus signal and holds the current-carrying path in a cut-off state, and activates the focus detection circuit and the brake closed circuit during manual focus adjustment. Focus camera focus adjustment device.