JPH05236326A - Auto-focus controller - Google Patents

Abstract

PURPOSE:To attain the quick and smooth auto-focus control with application of a mount climbing system by deciding the driving value of a pulse motor to successively improve the in-focus degree comparing the precedent accuracy and the present accuracy. CONSTITUTION:An area setting circuit 7 decides an area to extract an auto- focus control signal (AF signal) out of the vertical and horizontal synchronizing signals received from a camera circuit 6. A CPU 11 obtains the AF signal at the fall of the area signal received from the circuit 7, i.e., the end position of the decided area, performs the operations to obtain a difference signal between the AF signal and the precedent AF signal, a gradient signal from the difference signal, and a zoom position signal, etc., and performs the decision based on these signals. Thus, the CPU 11 decides the next driving value of a master lens driving pulse motor 15. Then, the motor 15 is driven asynchronously with the generating cycle of the video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device for video cameras, still cameras and the like.

[0002]

2. Description of the Related Art Conventionally, as an automatic focusing method for a focus of a video camera, a still camera, etc., the screen definition (the degree of focusing) is obtained from the video signal of each screen generated every 1/60 seconds. A so-called hill-climbing method is known in which the drive motor of the focusing lens is detected so that the resolution of the previous time and the resolution of this time are compared to sequentially increase the definition of the screen, that is, the degree of focus. There is.

Japanese Patent Publication No. 268/268
The autofocus device of No. 34 uses a pulse motor capable of extending the life as a drive motor for the focusing lens. If the drive cycle of this pulse motor and the generation cycle of the video signal are different, When the difference between the definition and this time is obtained, the control amount of the pulse motor for the difference is not constant, and the meaning of the difference becomes unclear, causing a malfunction. The above pulse motor was driven by a constant amount in synchronization with the vertical synchronizing signal of the signal.

[0004]

However, when the pulse motor is driven by a constant amount in synchronization with the generation period of the video signal as described above, there are the following problems.

(A) Even if it is determined by the mountain climbing type focusing control that the mountain is clearly climbing on the hillside or near the top of the mountain, it is difficult to accelerate or decelerate the pulse motor.

(B) When the subject change is detected from the stopped state and the focus control is started, the focus control according to the change of the subject distance due to the panning operation of the camera cannot be smoothly performed.

(C) When the pulse motor is driven by several pulses in each video signal generation cycle in order to perform the focusing control at high speed, while the screen definition is being detected from the video signal of each screen, A situation occurs in which the focusing lens is moving, and in this case, the image moves even though it is a stationary subject, which causes a malfunction, so high-speed control is actually impossible. Become.

It is an object of the present invention to realize high-speed and smooth automatic focusing control in a hill-climbing type automatic focus adjusting device using a pulse motor.

[0009]

To achieve the above object, an automatic focusing apparatus according to the present invention converts an optical lens including a focusing lens and an optical image formed through the optical lens into an electric signal. Camera circuit for outputting as a video signal, a pulse motor for moving the focusing lens, and a focus amount for sequentially detecting the definition of the screen obtained from the high frequency component of each video signal from the camera circuit. The drive amount of the pulse motor of this time is determined so as to sequentially increase the focus degree by comparing the previous definition and the present definition detected by the detection unit and the focus amount detection unit, The pulse motor drive control means drives the pulse motor asynchronously with the signal generation cycle.

[0010]

The optical image formed through the optical lens is converted into an electric signal by the camera circuit and output as a video signal.

Then, the focus amount detecting means sequentially detects the definition of the screen from the high frequency components of each video signal from the camera circuit.

Then, the pulse motor drive control means compares the previous fineness detected by the focus amount detecting means with the fineness this time so as to sequentially increase the focus degree, and the drive amount of the pulse motor at this time. Is determined, and the pulse motor is drive-controlled asynchronously with the generation cycle of the video signal.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of an automatic focus adjusting device according to the present invention.

As shown in FIG. 1, this automatic focusing device includes a taking lens 4 including a front lens 1, a zoom lens 2, a focusing master lens (hereinafter referred to as a master lens) 3, and a CCD sensor. 5, camera circuit 6, area setting circuit 7, bandpass filter 8, first A / D converter 9, addition circuit 10, CPU 11, focus sensor 12, zoom sensor 13, second A / D converter 14, master lens drive pulse It has a motor 15, a variable power lens drive pulse motor 16, a first motor drive circuit 17, and a second motor drive circuit 18.

The taking lens 4 forms an optical image of the subject on the CCD sensor 5, and the CCD sensor 5 photoelectrically converts the optical image of the subject and outputs it to the camera circuit 6. The camera circuit 6 performs various signal processing such as generation of a luminance signal and a color signal from the photoelectrically converted electric signal. The area setting circuit 7 determines an area for extracting a signal (AF signal) for automatic focus adjustment from the vertical synchronizing signal and the horizontal synchronizing signal from the camera circuit 6, and outputs the area signal to the first A / D converter 9. To do.
The bandpass filter 8 extracts only the high frequency component from the luminance signal from the camera circuit 6 and outputs it to the first A / D converter 9. The first A / D converter 9 includes a bandpass filter 8
The high frequency components from 1 to 3 are sampled in the area set by the area setting circuit 7, are A / D-converted sequentially, and are output to the adding circuit 10. The adder circuit 10 includes the first A / D converter 9
The digital values of the high-frequency components sequentially input from are added to obtain the total value in the area of one field, and the total value is output to the CPU 11 as an AF signal.

As shown in FIG. 2, the AF signal, that is, the high frequency component, decreases as the defocus amount increases.
The CPU 11 drives the master lens drive pulse motor 15 through the first motor drive circuit 17 to climb the peak of the AF signal by utilizing the fact that the defocus amount decreases and the focus amount increases as the focus comes into focus. Focusing control is performed by performing such control and controlling to stop at the maximum point of the AF signal. The focus sensor 1
2. The zoom sensor 13 is a sensor for detecting the positions of the master lens 3 and the zoom lens 2, respectively, and the signals from these sensors are A / D converted by the second A / D converter 14 and output to the CPU 11. To be done. Therefore, the CPU 11
The drive amount of the master lens drive pulse motor 15 is determined in consideration of the position signals from these sensors. In particular, the position signal from the focus sensor 12 is used when setting the initial position of the master lens 3.

Next, the master lens drive pulse motor 1
The drive timing of No. 5 will be described with reference to FIG.

An AF signal is obtained at the trailing edge of the area signal from the area setting circuit 7, that is, at the end position of the area. A difference signal between the AF signal and the previous AF signal, a gradient signal obtained from the difference signal, and a zoom position Calculations for obtaining signals, etc. and judgments based on them are performed (T ₁ in FIG. 3,
During the T ₁ ′ period), the drive amount (control speed) of the next master lens drive pulse motor 15 is determined. Here, the T ₁ and T ₁ ′ periods, which are the above-mentioned calculation / judgment periods, are indefinite,
This is because the steps to be followed in the flow of FIG. 5 described later are different.

The period from the calculation / judgment period T ₁ , T ₁ ′ to the next rise of the area signal (the period T in FIG. 3).
₂ , T ₂ ′), the master lens drive pulse motor 15 is driven. That is, while the area signal is in the “H” state and the AF signal is being generated, the master lens drive pulse motor 15 is stopped so that an accurate AF signal can be obtained based on a stable image signal of the subject. I have to.

As is clear from the above description, the master lens drive pulse motor 15 is driven asynchronously with the image signal generation cycle. By managing the number of pulses until the next AF signal generation period starts, for example, it is possible to clarify the meaning of the difference between the fineness of the previous time and the definition of the current time. Even if the master lens drive pulse motor 15 is driven by, the problem of malfunction due to the deviation of both cycles does not occur. The control speed of the master lens drive pulse motor 15 is determined by how many drive pulses are given during the T2 period.

Next, the outline of the automatic focusing control will be described with reference to FIG.

When the power is turned on, first, under the control of the CPU 11, initial settings such as the initial position of the master lens 3 are performed (step S1). Next, the mode shifts to the mountain climbing mode of climbing the mountain of the AF signal in the designated direction (step S
2). In this mountain climbing mode, the change of the AF signal is monitored while rotating the master lens drive pulse motor 15 in the designated direction, and when the AF signal becomes smaller than the previous time, the master lens drive pulse motor 15 is rotated in the reverse direction by a predetermined amount. , And shifts to the fine adjustment mode (step S3). In the fine adjustment mode, the motor speed is reduced to find the peak value of the AF signal. Then, when the peak value of the AF signal is found, the rotation of the master lens drive pulse motor 15 is stopped and the mode is shifted to the stop mode (step S4).
In stop mode, changes in the subject are determined. As a result, when there is a change, the mode shifts to the direction determination mode (step S5), the master lens is driven in a predetermined direction by a predetermined amount, and the control direction is determined based on the magnitude relationship of AF signals before and after the driving. Then, the mode returns to the mountain climbing mode. When the AF signal is “0” or very small in each mode, that is, when the focus is out of focus (low contrast), the mode is shifted to the search mode (step S6) and a relatively large AF signal is obtained. To be able to

Next, the drive control of the master lens drive pulse motor 15 will be described with reference to FIG. 5, focusing on the mountain climbing mode.

First, the CPU 11 starts the mode N0. Is set (step S201), and the drive pulse number counter is initialized to "0" (step S202). Next, the AF signal is read from the adder circuit 10 (step S203), and the control counter C is set to "4" (step S204). Then, it is judged whether or not the content of the control number counter C is "0" (step S205), and if it is not "0", the control number counter C is determined.
Is decremented by "1" (step S20)
6). Then, it is determined whether or not the AF signal is larger than a predetermined reference value "2049" (step S207). As a result, if the AF signal is larger than the predetermined reference value “2049”, 25 μm corresponding to one pulse is set as the control amount of the master lens drive pulse motor 15 (step S2).
08), and proceeds to step S213. On the other hand, if the AF signal is smaller than the predetermined reference value “2049”, 50 μm corresponding to 2 pulses is set as the control amount of the master lens drive pulse motor 15 (step S209), and step S209 is set.
Proceed to 213.

When it is determined in step S205 that the content of the control counter C is "0", it is determined whether the zoom position f is larger than 30 mm (step S205).
210), if the zoom position f is larger than 30 mm, 100 μm corresponding to 4 pulses is set as the control amount of the master lens drive pulse motor 15 (step S21).
1), the process proceeds to step S213. On the other hand, if the zoom position f is smaller than 30 mm, 50 μm corresponding to two pulses is set as the control amount of the master lens drive pulse motor 15 (step S212), and the process proceeds to step S213.

The above control means the following. That is, the master lens drive pulse motor 15 is rotated at a relatively low speed for the first four times in the mountain climbing mode. This is because the distance from the subject may change due to the panning operation of the camera when the subject is detected from the stopped state and the motor control (focus control) is performed. That is, immediately after the subject has changed, and when the AF signal is large, there is a high possibility that panning is still in focus, so the master lens drive pulse motor 15 is rotated at the minimum speed. Also,
When the subject changes and the AF signal is small, it is highly likely that the subject distance has changed. Therefore, the master lens drive pulse motor 15 is rotated at a higher speed than in the above case. However, even in this case, the motor may be rotated at a relatively low speed because it may be in the middle of panning. In addition,
As will be apparent from the description below, even in the control of the first four times, when the AF signal of this time becomes smaller than that of the previous time, the mode shifts to the fine adjustment mode. In addition, in the control from the fourth time onward, the motor speed is increased based on the judgment that the hill climbing direction is definitely the designated direction. However, in this case, the motor speed is determined in consideration of the zoom position. this is,
The range of movement of the master lens 3 differs depending on the focal length. For example, at the wide end, it is possible to control from the closest 1 m to the point at infinity with 4 pulses, so it is not necessary to control so fast, and conversely on the tele side from the closest 1 m to infinity. This is because more pulses are required up to the distant point and high-speed control is required.

In step S213, it is determined whether or not the manual switch is turned on. As a result, if this switch is turned on, control according to the manual mode is performed (step S214). On the other hand, if the switch is not turned on, the AF signal is the predetermined reference value "12".
It is determined whether it is larger than 7 "(step S21).
5). As a result, if it is smaller than the reference value “127”, it means that there is a large blur (low contrast).
The mode shifts to the search mode (step S216). If the AF signal is larger than the reference value "127", the master lens drive pulse motor 15 is rotated in the designated direction by the set control amount (step S217).

Then, the next AF signal is read (step S218), and it is determined whether or not the previous AF signal is larger than the current AF signal (step S219). As a result, if the previous AF signal is smaller than the current AF signal,
Further, it is determined whether or not the previous gradient is larger than the current gradient (step S220). As a result, if the previous gradient is larger than the current gradient, the process returns to step S205, and if the previous gradient is smaller than the current gradient, it is further determined whether or not the AF signal is larger than the reference value "127" (step S221). . As a result, if it is smaller than the reference value “127”, the process returns to step S205, and if it is larger than the reference value “127”, the control number counter C is set to “2” (step S222) and the process returns to step S205.

In the processing of steps S218 to S222, when climbing a hill and reaching the peak of the AF signal, in order to avoid unsmooth control such as overshoot or hunting, the control speed is reduced to bring the focus into focus. It means to come. That is, when the slope of the mountain this time becomes smaller than the slope of the previous mountain and the AF signal becomes larger than the predetermined value, it is determined that the peak of the mountain is near, and the motor speed is the same as at the beginning of the mountain climb. I'm slowing down.

When it is determined in step S219 that the previous AF signal is greater than the current AF signal, it means that the peak of the mountain has been passed, so control is performed in the reverse direction by 25 μm (step S223). The mode shifts to the fine adjustment mode (step S224). In this way, the master lens drive pulse motor 15 is driven and controlled asynchronously with the vertical synchronization signal (that is, asynchronous with the video signal generation cycle) in consideration of the difference between the current and previous AF signals, the slope of the mountain, the zoom position, and the like. By making the motor control speed variable, high-speed and smooth automatic focusing control is realized.

The present invention is not limited to the above-mentioned embodiment, but it is also possible to set a finer control amount according to the zoom position and perform more fine-tuned control.

[0033]

According to the present invention, in a hill-climbing type automatic focus adjusting device using a pulse motor, high-speed and smooth automatic focusing control can be realized, and the usability of a video camera or a still camera equipped with this device is improved. improves.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an automatic focusing device according to the present invention.

FIG. 2 is a diagram showing a relationship between the magnitude of an AF signal and the degree of focusing.

FIG. 3 is a time chart showing drive timing of a master lens drive pulse motor.

FIG. 4 is a flowchart showing an outline of drive control of a master lens drive pulse motor.

FIG. 5 is a part of a flowchart showing details of drive control of a master lens drive pulse motor.

6 is the remaining portion of the flowchart of FIG.

[Explanation of reference numerals] 3 master lens 4 photographing lens 5 CCD sensor 6 camera circuit 7 area setting circuit 8 band pass filter 9 first A / D converter 10 addition circuit 11 CPU 15 master lens drive pulse motor 17 first motor drive circuit

Claims (2)

[Claims] 1. An optical lens including a focusing lens, a camera circuit for converting an optical image formed through the optical lens into an electric signal and outputting the signal as a video signal, and a lens for moving the focusing lens. A pulse motor, a focus amount detecting means for sequentially detecting the fineness of the screen obtained from the high frequency component of each video signal from the camera circuit, the previous fineness detected by the focus amount detecting means and the current fineness. And a pulse motor drive control unit that drives the pulse motor asynchronously with the generation cycle of the video signal, by determining the drive amount of the pulse motor this time so as to sequentially increase the focus degree by comparing An automatic focus adjustment device characterized in that 2. The pulse motor drive control means inhibits the drive control of the pulse motor while the definition of the screen is detected from the high frequency component of the video signal by the focus amount detection means. The automatic focusing apparatus according to claim 1, wherein the automatic focusing apparatus is a focusing apparatus.