JPS58214130A - Automatic focus controller - Google Patents

Abstract

PURPOSE:To reduce the effect of the inertia force of a motor on the stoppage of lens shift, by controlling the driving state of a motor which shifts the lens in four states, i.e., the continuous drive, the 1st and 2nd pulse drives and the reverse drive, respectively. CONSTITUTION:A distance signal is supplied to a comparator 6 from a distance signal generator 1 after the distance up to an object is measured by a known means. The comparator 6 compares the lens position signal supplied from a lens position detecting circuit 5 with the distance signal and then actuates a driving circuit 4 of a motor 3 which shifts a photogaphing lens 2 to the focused position. A continuous driving part A is selected when a shift extent of the lens is large, i.e., the shift of the lens is started. The part A is changed to the 1st pulse driving part B as the part A gets close to the focused position and then to the 2nd pulse driving part C of a smaller driving torque than the part B. Then a reverse pulse driving part D is selected at the focused position, and the revolution of the motor 3 is stopped at once.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic focusing device that automatically focuses a photographic camera, a video camera, etc. by automatically moving a photographic lens to a predetermined position using a motor, and particularly relates to an automatic focusing device that automatically focuses a photographing lens of a photographic camera, a video camera, etc. The present invention relates to an automatic focus adjustment device equipped with a photographic lens movement stop device that can very accurately stop a photographic lens at a predetermined position.

2. Description of the Related Art Various devices for automatically adjusting the focus of a photographic lens of a video camera or the like have been proposed in the past, and devices in which the photographic lens is moved by a motor are also well known.

That is, the photographic lens is moved by the rotation of the motor based on the output from the focus state detection section forming the automatic focus adjustment device, and the photographic lens is positioned at a predetermined position where the in-focus state can be obtained by stopping the rotation of the motor. This device has been well known in the past, and the means for controlling the rotation and stopping of the motor as described above is a means for controlling the state of energy supply, that is, when the motor needs to rotate, it supplies energy. However, means to cut off energy when it is not needed is extremely common, and is also used in the above-mentioned devices.

However, controlling the rotation and stopping of the motor by supplying and cutting off energy as described above has a problem in that it is extremely affected by inertial force.

That is, even if the energy supply to the rotating motor is cut off, the motor does not stop immediately and continues to rotate due to inertial force even after the energy supply is cut off. If we consider specifically the movement control of the photographic lens, the influence of the inertial force of the motor will differ depending on whether the photographic lens has moved a large amount to a predetermined position or if it has only a small amount of movement. Even if the motor is shut off, the time it takes for the motor to completely stop rotating and the photographic lens to stop will vary, resulting in a problem in that the stopping position of the photographic lens will vary around a predetermined position.

In addition, if the stop position of the photographic lens cannot be set correctly,
Needless to say, even if extremely accurate focus detection operation is possible, a fatal problem arises as a device in that a good in-focus state cannot be obtained.

As a motor-based movement control device for a photographic lens that takes this problem into consideration, a device as disclosed in Japanese Patent Application Laid-Open No. 100532/1983 is known.

In order to accurately stop the photographing lens at a predetermined position, this device is equipped with a device that generates a signal representing a location area adjacent to the location area including the predetermined position, and detects an adjacent location based on the output of the adjacent location area detection device. The state of energy supply to the photographing lens from the location range to the location range including the predetermined position is controlled to a pulsating state, and the energy supply is stopped when the predetermined location range is reached. It is something.

That is, the moving torque supplied to the photographic lens is changed into three states, and the influence of the above-mentioned inertial force is avoided as much as possible.

In other words, the photographic lens receives a large moving torque by continuously supplying energy to the motor until it reaches the adjacent location area, and when the adjacent location area is detected, pulsating energy is supplied to the motor. A small moving torque is supplied to the motor, and when it finally reaches a predetermined position, the movement is stopped by cutting off the energy supply to the motor.

Therefore, the inertial force of the motor is largely absorbed when the motor's rotation is controlled by pulsating energy supply within the adjacent position range, so it is necessary to cut off the energy supply to the motor when it reaches the predetermined position range. For example, the motor stops rotating within a very short period of time, and the photographic lens can be accurately set at a predetermined position.

However, as mentioned above, JP-A-55-10053
The device disclosed in the No. 2 publication also has the possibility of causing the same problems as the conventional device when the position range of the photographing lens is set to be extremely small.

In other words, if the position range of the photographic lens becomes extremely small, the control time within the adjacent position range becomes extremely short, so even if pulsating energy is supplied, it may not be possible to sufficiently absorb the motor's inertial force. Furthermore, if the setting position range is small, even a slight movement error may cause the photographic lens to be out of focus, so it is still not perfect.

Regarding the setting of the position range of the photographic lens mentioned above, for example, in the case of a zoom lens used in a video camera, an extremely small setting is required, so a device that can stop the movement of the photographic lens extremely accurately is required. Needless to say, this is required.

The present invention has been made in consideration of the above-mentioned points,
The purpose of the present invention is to provide an automatic focus adjustment device equipped with a photographing lens movement stop device that can extremely accurately set the position of the photographic lens using a motor even if the setting of the position range of the photographic lens is small. explain.

FIG. 1 is a block diagram showing one embodiment of an automatic focus adjustment device according to the present invention. In the figure, 1 measures the distance to the subject, and based on the measurement, an electric signal corresponding to the subject distance, that is, the distance a distance signal generator that outputs a signal; 2 a photographic lens; 3 a motor that controls movement of the photographic lens 2;
4i1: Motor drive circuit that controls the operation of the motor 3, 6
6 is a lens position detection circuit that outputs an electric signal corresponding to the position of the photographic lens 2, that is, a lens position signal; 6 is a lens position detection circuit that compares the distance signal described above with the lens position signal, and determines the rotation direction of the motor 3; Comparing circuits that output the amount of rotation, that is, the direction and amount of movement of the lens, and control the operation of the motor drive circuit 4 are shown.

Note that the rotation of the motor is controlled by the comparison circuit 6 and the motor drive circuit 4, and it goes without saying that these two circuits constitute a photographing lens movement stop device.

Further, the motor drive circuit 4 is configured as shown briefly in the drawing.
It has four parts A, B, C, and D. Among these parts, A is a continuous drive unit that continuously supplies energy to the motor, B is a first pulse drive unit that supplies first pulse drive energy to the motor, and C is a first pulse drive unit. a second pulse drive unit that supplies the motor with second pulse drive energy having a drive torque smaller than the energy;
Reference numeral D indicates a reverse pulse drive unit that supplies reverse pulse energy to the motor, and is configured to be appropriately selected based on the comparison result output of the comparator circuit 6.

In the operation of one embodiment of the automatic focus adjustment apparatus according to the present invention having the above-mentioned configuration, first, the distance to the subject is measured by a well-known means such as an optical method or an ultrasonic method.

When the distance to the subject is measured, the distance signal generator 1
'' supplies a distance signal corresponding to the subject distance to the comparison circuit 6.

The comparator circuit 6 is also supplied with an electric signal corresponding to the detected position from the lens position detection circuit 6 that detects the position of the photographic lens 2, that is, a lens position signal. Therefore, the distance signal and the lens position signal are Comparison circuit 6 compares them.

The comparison circuit 6 compares the photographic lens 2 with the comparison operation as described above.
If the lens is not in focus, the photographic lens 2
The motor drive circuit 4 is operated to move the motor. The output signal from the comparator circuit 6 at this time is a signal that can determine the moving direction of the photographic lens 2;

Now, let us consider a case where the photographing lens 2 requires a large amount of movement to reach a position where it can be in focus.

First, based on the comparison result of the comparison circuit 6, the motor 3 is operated by the motor drive circuit 4 in order to move the photographing lens 2 in the direction in which the amount of movement is required. At this time, the drive state of the motor 3 is such that the continuous drive section A is selected at the start of movement in the motor drive circuit 4, so that the motor 3 is in a drive state in which energy is continuously supplied. 3
is rotated with a large torque, and the photographing lens 2 is moved in a predetermined direction.

When the photographing lens 2 starts to move, the lens position signal from the lens position detection circuit 5 changes as a result of this movement, and naturally the comparison result from the comparison circuit 6 also changes.

That is, since the photographic lens 2 moves closer to the position where the in-focus state can be obtained, the difference between the two signals mentioned above in the comparison result by the comparator circuit 6 gradually decreases.

In the device according to the present invention, when the difference between the two signals from the comparison circuit 6 decreases to a certain level, the control state of the motor 3 in the motor drive circuit 4 changes from control by the continuous drive unit A to control by the first pulse drive unit B. It is designed so that it can be switched depending on the state. That is, the configuration is such that the driving torque of the motor 3 is reduced when the photographing lens 2 approaches the in-focus position to some extent.

When the control state by the motor drive circuit 4 is switched to the first pulse drive unit B, the energy supply state to the motor 3 becomes pulsed." - As mentioned above, the drive torque becomes smaller, but it is difficult to maintain rotation. Needless to say, therefore, the photographing lens 2 also moves further toward a position where an in-focus state can be obtained.

When the photographing lens 2 approaches a position where a focused state can be obtained due to the rotation of the motor 3 by the first pulse drive unit B,
For example, when reaching an adjacent range of an extremely small lens position range including the in-focus position, the motor drive circuit 4 is further switched to the second pulse drive unit C, and the drive torque by the first pulse drive unit B is increased. The operation of the motor 3 is controlled by an even smaller drive torque. still,
Needless to say, the timing of the switching as described above can be easily set by detecting the difference between the two signals in the comparison result of the comparator circuit 6.

The motor 3 is further rotated by supplying a small driving torque by the second pulse driving section C, and the photographing lens 2 reaches a position where a focal point can be obtained.

When the photographic lens 2 reaches the position where the focal point can be obtained, the distance signal and the lens position signal will match, so
The comparison circuit 6 outputs a coincidence signal, and the reverse pulse drive section is selected in the motor drive circuit 4 based on this coincidence signal.

When the reverse pulse drive section is selected, the motor 3 is supplied with pulse energy in the opposite direction to the energy that has been supplied to the motor 3 immediately or after a predetermined period of time during which no energy is supplied.

For this reason, from the supply of large drive torque by the continuous drive unit A until then, the first and second pulse drive units B,
In addition to the fact that the drive torque is gradually reduced and the inertia force is suppressed by C, the rotation of the motor 3 is immediately stopped at the time when the above-mentioned reverse pulse energy is supplied, and needless to say, the rotation of the photographing lens 2 is stopped. Movement will also stop.

As described above, in the automatic focusing device according to the present invention, the motor is continuously driven.

By setting multiple pulse energy supply states with different amounts of supplied energy and reverse pulse energy supply states, the effect of the inertia of the motor on stopping the movement of the photographic lens is minimized, making the photographic lens extremely useful. It becomes possible to position the positive electrode at a predetermined position.

FIG. 2 shows a comparison circuit 6. of the automatic focus adjustment device according to the present invention explained in FIG. This figure shows a specific example of the motor drive circuit 4, most of which is implemented by a microprocessor unit (
Hereinafter, an example configured with 7 (hereinafter referred to as M, P, and U) is shown.

First, the operation of specific circuit parts including the motors 3 other than M, P, U, and 7 will be briefly explained.

When the distance signal and lens position signal in the functional part corresponding to the comparator circuit 6 are compared, M, P, U, -
r generates an output signal at output terminal E or F to control the operation of transistor 8 or 9. In addition, M, P,
It goes without saying that the selection of the output terminal E or F at U, 7 is determined by the required rotational direction of the motor 3 obtained from the comparison result of the comparison function section, as will be described in detail later. Alternatively, the conducting/non-conducting state of 9 is controlled by the output signal from the output terminal E or F.

Now, if the transistor 8 is made conductive by the output signal from the output terminal E, then the resistor 10, 1 is connected to the power supply terminal G.
1. ) A current flows in the loop of the transistor 8, and the transistor 12 is made conductive by the N voltage across the resistor 1o.

When the transistor 12 becomes conductive, the power supply terminal G connects the transistor 1 to the motor 3. Current will flow through the transistor 8, causing the motor 3 to rotate in a predetermined direction, and of course also moving the photographing lens 2.

On the other hand, the output signal from the output terminal F causes the transistor 9 to
If we consider the case where the resistors 13, 14 . ) A current will flow through the transistor 9 and the transistor 16 will therefore be rendered conductive.

When transistor 16 becomes conductive, energy from power supply terminal G is transferred to transistor 14. Motor 3. The energy will be supplied through the loop of transistor 9, and the direction of the energy supply will be opposite to that in the above case, so motor 3 will rotate in the opposite direction to when transistor 8 is in a conductive state. .

The specific circuit portion operates in accordance with the relationships described above, and below, M, P, U,
The operation of step 7 will be explained with reference to the flowchart shown in FIG.

FIG. 3 shows the comparator circuit 6. shown in FIG. This is a flowchart showing an example in which the lens drive circuit 4 is composed of M, P, U, and R, but for convenience of explanation, step 100 of the comparison function section is described as the start.

Now, the distance signal X and lens position signal Y in the comparison function section
If the results of step 100, which compare the Therefore, steps 101 of M, P, U, and 7, which also constitute the motor drive circuit 4, are selected.

Step 101 is a step of determining the difference Z between the above-mentioned signals X and Y, and once the difference Z is determined, the next step 10 is performed.
Proceed to step 2.

Step 102 is a step of confirming the sign of the difference Z between both signals X and Y. For example, if the sign of the difference Z is positive, step 103 is selected and the motor 3 is outputted with normal rotation, and if the sign is negative, step 104 is selected and set to a mode in which a reverse rotation output is supplied to the motor 3. That is, to describe the specific operation, step 102 is the operation of selecting which of the output terminals E8 and F should output the output signals generated by M, P, U, and 7.

Step 103 or 104 is selected by step 102, and an output signal is issued from either output terminal E or F of M, P, U, 7 in FIG. 2, and rotation of the motor 3 in a predetermined direction is started. Then, M, P, 0.
7 goes to the inte knob 105, and the absolute value of the above-mentioned difference Z +21
is required.

It goes without saying that this absolute value 121 corresponds to the amount of movement of the photographing lens 2, and the photographing lens 2 must be accurately moved by this absolute value.

The size of is compared with an arbitrary number N and determined.

This step 106 is a step for selecting the continuous drive section A and the first pulse drive section B in the motor drive circuit 4 described above. Note that the number N, which is the criterion for determining the magnitude of the absolute value in step 1Φ6, is determined by taking into consideration how the photographic lens 2 is divided into positions, that is, the method of setting the detectable position range of the photographic lens 2. It is determined.

Now, for example, if we consider the case where the distance from the closest shooting position of /Z2 to the infinity shooting position is divided into about 70 setting points I, the absolute value I21 of the above-mentioned difference Z will be within several points. If so, it is desirable to configure the first pulse drive section B to be selected, and in this case, the number N may be selected from 3 to 6 in consideration of the moving speed of the photographic lens 2, etc.

Incidentally, if the absolute value IZ1 is greater than or equal to several N, the distance signal Needless to say, the motor 3 is rotated by the continuous drive section A with a large drive torque.

If it is determined in step 106 that the absolute value I21 is smaller than the arbitrary number N, that is, the photographing lens 2 has approached the desired position, then step 1o is selected.

Step 107 is a step in which the inertia force of the motor 3 is taken into account, and it is determined whether the motor 3 that has been rotating up to that point is at startup time. The inertial force is small, and if the motor 3 has been repeatedly driven from step 100 to step 106, the inertial force is considered to be large, and this step is to determine the difference in inertial force.

This step 107 is performed in accordance with the present invention, as explained in the block diagram of FIG. Since the states of start-up and continuous drive frequently occur, the following steps, which are selected based on the determination results, play an extremely important role in accurate drive control of the motor 3.

If it is determined in step 107 that the motor 3 is starting, step 108 is performed to supply power to the motor 3 for a predetermined time, and if it is determined that the motor 3 is still in continuous drive, the step is immediately performed. 109 is selected.

Step 109 is a step for determining the magnitude of the absolute value of the difference Z+21, and it is determined whether the magnitude of the above absolute value is 1 or not, similar to step 106 described above. That is,
It has the function of determining whether or not the photographing lens 2 has reached the next point as soon as it has been set, and switching the state within the motor drive circuit 4 from the first pulse drive section B to the second pulse drive section C based on the result. It is a step.

If the determination result in step 109 is different from 1, step 110 supplies power to the motor 3 for a predetermined time.
If it is determined to be 1, step 110 is skipped and step 111 is selected in which power is supplied to the motor 3 for a predetermined time.

Step 111, like steps 108 and 110, is a step of supplying power to the motor 3 for a predetermined period of time.

When step 111 is completed, step 112 is selected and the power supply to the motor 3 is stopped, and the next step 1
At step 13, a power supply stop period to the motor 3 is set.

When step 113 is completed, the flowchart returns to step 100, and if the determination result in step 100 does not match, the operations of each step as described above are repeated.

On the other hand, the process returns to step 100, and if the determination result in step 100 matches, step 114 is selected.

Step 114 is a step from step 100 to step 1.
In this step, it is determined whether or not the motor 3 has rotated up to 14.

If the determination result in step 114 is that the motor 3 is not rotating, this indicates that the photographing lens 2 is at the in-focus position from the beginning, and for example, as indicated by number 1 in FIG. If it is determined that an output signal for operating the distance signal generator is output, and that the operations from step 101 onwards as described above have been performed and the motor 3 is being rotated, step 115 is selected.

Step 116 is a step of supplying the motor 3 with the output necessary to rotate the motor 3 in the opposite direction to the direction of rotation of the motor 3 that has been rotated in the steps from step 101 to step 113.
determined by

When step 116 is completed, the energy supply to the motor 3 is stopped, the motor 3 is stopped in step 117, and the flowchart returns to step 100 again.

The operation as described above is the operation of the flowchart shown in FIG. 3, and finally, the relationship with the operation of the flowchart will be briefly explained using the power supply state diagram to the motor 3 as shown in FIG. do. Note that an example in which the arbitrary number N in step 106 is "3" will be explained.

In FIG. 4, the straight line 0 is a pseudo-indication of the range of set points of the photographic lens 2, of which 80 is the point to be set, A1 is the adjacent point, hereinafter,
A2. Points that you want to set according to A3...A. I think it will move away from.

Further, the solid line P is a voltage waveform diagram showing the power supply state to the motor 3, and needless to say, its horizontal axis corresponds to the straight line 0.

Now, as soon as the shooting lens 2 is set, point) A. If the melting point is located at seven points far apart from each other, step 103 or step 10 of the flowchart explained in FIG.
4, a driving voltage is supplied at eight points, and driving of the motor 3 in a predetermined direction is started.

At this point, the position of the photographic lens 2 is at the set point A. As explained above, the steps are repeated between 100 and 106, and the voltage supplied to the motor 3 is DC as shown in Fig. 4, and the drive torque is large. will be supplied.

When the motor 3 is continuously rotated by the power supply as described above and step 106 is performed at time b when the photographic lens 2 approaches point A as soon as it is set and reaches within point A3, the process proceeds to step 107 and thereafter. At the time,
At time c, steps 110 and 111 are carried out, and at time d, step 112 is carried out, and the power supply to the motor 3 is stopped. Note that this power supply stop period is during step 1.
13 will be mainly determined.

Then, the operations from step 100 are repeated again from time e. .

As a result, the power supply state to the motor 3 is such that the power supply time is the period determined by each step 103 or 104, 106, the power supply stop time is the period determined by the processing time of steps 112, 100, 101, 102, and step 113. W
The voltage becomes the first pulse voltage, and thereafter, the first pulse voltage continues to be supplied until the determination result in step 109 changes.

If the determination result in step 109 is different from the determination in the first pulsing voltage supply state described above when the photographic lens 2 reaches within point A1, step 110 is skipped. Although the voltage is the same, its characteristics are different.

That is, if point A1 is recognized at step 109 at time point (3), the motor 3 will be supplied with power for a certain amount of time at step 1.
03 or 104. 105.106゜107.10
8,109, the period determined in step 111, and the power supply stop period are steps 112, 100, 10.
A second pulse voltage is supplied for a processing time of 1,102 and a period determined in step 113. In other words, although it is clear from the drawing, point A1
In this case, the driving torque of the motor 3, which has a short power supply time, is suppressed to supply energy.

In the above condition, the photographic lens 2 is
. Suppose that step 114 is selected based on the judgment in step 100 when the power supply is stopped, the power supply to the motor 3 is stopped, and a reverse pulse voltage as shown in the drawing is supplied at time q in steps 115 and 116. be done.

As a result, the motor 3 completely stops its rotation and the photographic lens 2 is set correctly.Point) A. It will be located inside.

As described above, the present invention is an automatic focus adjustment device that uses a motor to automatically move a photographic lens to a focused position, and detects the state of power supply to the motor relative to the focused position of the photographic lens. An automatic focus adjustment device that is characterized by controlling information to four drive states: DC drive, first and second pulse drive, and reverse drive, and is capable of extremely accurately positioning the photographic lens at the in-focus position. It is of extremely high practical value.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic focus adjustment device according to the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the motor drive circuit and comparison circuit indicated by numbers 4 and 6 in FIG. 3 is a flowchart of M, P, and U indicated by number 7 in FIG. 2, and FIG. 4 is a flowchart of M, P, and U in the automatic focus adjustment device according to the present invention. 70 shows the power supply waveform to the motor and the photographic lens positional relationship diagram, respectively. 1...Distance signal generator, 2...Photographing lens, 3...Motor, 4...Motor drive circuit, 6...Lens Position detection circuit, 6...
. . . Comparison circuit, 7 . . . Microprocessor unit (M, P, U,). Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (2)

[Claims] (1) Photographic camera! :' A comparison circuit that detects the positional relationship between the position of a photographing lens such as a video camera and a predetermined position to which the photographing lens is desired to be moved to obtain a focused state;
In an automatic focus adjustment device that includes a motor that moves the photographic lens and a motor drive circuit that supplies energy to the motor, the motor drive circuit supplies DC power to the motor to generate a large drive torque. a continuous drive section; a first pulse drive section that supplies power intermittently to the motor to generate a drive torque smaller than the drive torque obtained by the continuous drive section; a second pulse drive unit that generates a drive torque smaller than the drive torque obtained by the pulse drive unit; and a second pulse drive unit that supplies pulse energy in eight directions opposite to the one direction in which the energy is supplied to the motor by each of the drive units. and a reversing pulse drive section, each drive section being appropriately selected based on a positional relationship detection output between the photographing lens position and the predetermined position by the comparison circuit to control the drive of the motor. Focusing device. (2) A comparison circuit and a motor drive circuit include the steps of determining the difference between the photographing lens position and a predetermined position, determining the sign and absolute value of the difference, and moving the motor in a predetermined direction based on the sign of the difference. a step of determining the magnitude of the absolute value by comparing it with an arbitrary predetermined number N that is between 1 and 2 and can be recognized as indicating that the photographic lens is close to the in-focus position; a step for determining whether the absolute value is equal to 1; and a step for a plurality of timers for controlling the power supply time to the motor by two steps: determining whether the absolute value is equal to 1, and determining the magnitude of the absolute value.
a step of stopping power supply to the motor when the magnitude of the absolute value is 1; and a step of supplying pulse energy to the motor in a direction opposite to the direction of the power supply, which is selected when the absolute value becomes zero. The automatic focus adjustment device according to claim 1, characterized in that it is constituted by a microprocessor unit including a microprocessor unit.