JPH0698235A - Camera - Google Patents

Abstract

PURPOSE:To enable speedy focusing even when an object is out of an original distance measure frame by changing an area to extract a sharpness signal when the driving direction of a lens part to perform focusing control is inverted plural times. CONSTITUTION:A video signal is sent through a gate circuit 11 to prepare the distance measure frame for performing automatic focus processing to a signal processing circuit 12 to process the video signal (to prepare the sharpness signal) for performing automatic focus processing and fetched into a Microcomputer 13 for lens control later. The gate circuit 11 is controlled by the microcomputer 13. In the case of changing the size of the distance measure frame, a signal for this change is sent from the microcomputer 13 to the gate circuit 11 by a signal line S5 and the size of the distance measure frame is changed. When the driving direction of a focus lens 6 is inverted plural times during mountaineering automatic focus control, the distance measure frame is enlarged. Thus, an object can be speedily focused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera having an automatic focusing device for automatically focusing on a subject.

[0002]

2. Description of the Related Art In recent years, the development of video equipment such as video cameras and electronic cameras has been remarkable, and in particular, in order to improve the functions and operability thereof, an automatic focusing device (AF) and an automatic exposure control device (AE) have been developed. ) Etc. have come to be equipped as standard.

By the way, looking at the automatic focus adjusting device, the sharpness of the screen is detected from the video signal obtained by photoelectrically converting the subject image by an image pickup device or the like, and focus adjustment is performed so as to maximize it. A method of controlling the position of a lens (hereinafter referred to as a focus lens) to perform focus adjustment is becoming mainstream.

As the evaluation of the sharpness signal, generally, the strength of the high frequency component of the video signal extracted by the band pass filter (BPF) or the blur width of the video signal extracted by the differentiating circuit ( The width of the edge part of the subject) The detection intensity is used.

This is because, when a normal subject image is taken, the high-frequency component level is small and the blur width is large in the defocused state, and the high-frequency component level is large and the blur width is small as the focus is improved. Then, the maximum value and the minimum value are taken respectively when the focus is completely reached. Therefore, when the sharpness is low, the focus lens is controlled so that the focus lens is driven at a high speed in a direction in which the sharpness is high, the speed is decelerated as the sharpness becomes higher, and the focus lens is accurately stopped at the top of the mountain. Controlled. Such a control method is generally called a hill-climbing auto focus method (hill-climbing AF).

By adopting such an automatic focus adjusting device, the operability has been dramatically improved in the past, especially in a video camera for taking a moving image, and in recent years, it has become an essential function.

In a camera for converting an optical image into an electric signal by such an image pickup device, an area (hereinafter referred to as a distance measuring frame) for extracting a sharpness signal necessary for hill-climbing AF is mainly a central portion of the screen. It is generally set to. This assumes that the photographer will bring the subject he wants to shoot to the center of the screen.

There is also known a method of varying the distance measuring frame depending on the state of the subject. According to this method, for example,
By enlarging the range-finding frame, it becomes possible to focus on a subject at the edge position of the screen. Further, even when the subject moves from one end of the screen to another, such as during panning, the distance measuring frame is made variable so that a stable image is always maintained.

[0009]

However, in the above-mentioned conventional example, since the range-finding frame is not changed during the hill-climbing AF, the subject is out of the range-finding frame when focusing is attempted from the large blur state. However, there is a drawback in that the focus lens cannot find the focal point, causing hunting or stopping the blur.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a camera capable of quick focusing even when a subject is not within the original distance measuring frame.

[0011]

In order to achieve the above object, the present invention provides a lens unit for focus adjustment, a driving unit for moving the lens unit in parallel with the optical axis, and a focusing degree from a video signal. Extraction means for extracting a sharpness signal according to the above, a focus adjustment means for controlling the drive means by the sharpness signal extracted by the extraction means for focus adjustment, and an extraction of the sharpness signal in the screen. In a camera having a changing means for changing the area, a control means for controlling the area for extracting the sharpness signal to be changed when the driving direction of the lens portion is inverted a plurality of times is provided. is there.

Further, in order to achieve the same object, it is desirable to control so as to prohibit or allow the change by the changing means according to the movement amount from the time when the driving direction of the lens portion is reversed to the time when the driving direction is reversed again.

[0013]

When the driving direction of the lens section for focus adjustment is reversed a plurality of times, the area for extracting the sharpness signal changes, so that quick focusing is possible even when the subject is not within the original range-finding frame. It will be.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing the configuration of a video camera as a camera according to the first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an inner focus type lens system. A first fixed lens (front lens) 2 sequentially arranged along the optical axis from the subject side to the right side, and a zoom lens (zoom) for moving in parallel with the optical axis to perform zooming ( 2nd lens part) 3, diaphragm 4,
It comprises a second fixed lens 5 and a focus lens (first lens portion) 6 having both a competition function and a focusing function.

The optical object image formed by the lens system 1 is imaged on the image pickup surface 7a of the image pickup device (CCD) 7 and photoelectrically converted into a video signal. This video signal is amplified by the first amplifier (or impedance converter) 8, the amplitude of the output by the AGC (automatic gain control device) 9 is kept constant, and only the high frequency component is extracted by the filter (extracting means) 10. . Next, the video signal is processed through a gate circuit (gate means) 11 for forming a distance measurement frame for performing AF (autofocus) processing, and the video signal for performing AF processing is processed (creating a sharpness signal). After being sent to the signal processing circuit 12 for the lens, it is taken in by a lens control microcomputer (hereinafter, referred to as a microcomputer) 13. The gate circuit 11 is controlled by the microcomputer 13.

The variable power lens 3 and the focus lens 6 are driven by driving means 14 and 15, respectively. Drive means 1
Reference numerals 4 and 15 include stepping motors 14a and 15a and drivers 14b and 15b (hereinafter, the stepping motor 14a on the variable magnification lens 3 side is referred to as a zoom motor, and the stepping motor 15a on the focus lens 6 side is referred to as a focus motor. ). Output shafts 14c and 15c directly connected to the zoom motor 14a and the focus motor 15a
The racks 14d and 15d meshing with the are fixed to the variable power lens 3 and the focus lens 6, respectively.

Then, in accordance with the drive command signal output from the microcomputer 13, the drive energy is supplied from the drivers 14b and 15b to the zoom motor 14a and the focus motor 15 respectively.
When the output shafts 14c and 15c are respectively output to a and are rotated, the variable magnification lens 3 and the focus lens 6 move integrally with the racks 14d and 15d in parallel with the optical axis (arrow A and B directions in the figure). .

The diaphragm 4 is driven by a driver 16 which is a driving means. That is, the control signal from the control circuit 17 for detecting the level of the output signal of the AGC 9 and adjusting the diaphragm state of the diaphragm 4 so as to keep this level constant is the second signal.
It is amplified by the amplifier 18 and sent to the driver 16, and the driver 4 drives the diaphragm 4.

The diaphragm state of the diaphragm 4 is detected by the encoder 19, the detection signal is amplified by the third amplifier 20, converted into a signal which can be read by the microcomputer 13 by the signal conversion circuit 21, and then taken into the microcomputer 13.

Further, the information in the camera section is transmitted to the lens controlling microcomputer 13 through a communication line or the like.

The microcomputer 13 has a wide switch 2 for moving the variable power lens 3 in the wide and tele directions.
2, an infinite switch 24 and a close-up switch 25 for moving the tele switch 23, the focus lens 6 in the infinite direction and the close-up direction, respectively.

A power supply 27 is connected to a connection line between each of the switches 22 to 25 and the microcomputer 13 via a pull-up resistor 26.

Next, the control operation of the camera of the present invention having the above structure will be described with reference to FIG. FIG. 2 is a flowchart showing the control procedure of the AF part of the control of the entire camera. In the figure, first, in step 201, it is determined whether or not the focus is achieved. If it is in focus, the process proceeds to the next step 202 and the value C of the counter is incremented. Then, in the next step 203, it is observed whether the counter value C is an even number,
If it is even, it proceeds to step 204, and if it is odd, it proceeds to step 211.

In steps 204 and 211, the size of the distance measuring frame is changed. The signal for this change is sent from the microcomputer 13 to the gate circuit 11 by the signal line S _{5 in} FIG.
And the size of the distance measuring frame is changed. Step 20
In 4, the distance measuring frame is made smaller. Next step 205, 20
In FIG. 6, Es represents the sharpness signal extracted by the current distance measuring frame, Ess represents the sharpness signal captured by the small distance measuring frame, and Ess ₀ represents the sharpness signal previously measured by the small distance measuring frame. ing.

In step 205, the sharpness signal captured by the previous small distance measuring frame is Ess _0, and in step 206, the sharpness signal currently captured is Ess.

In step 211, the distance measuring frame is enlarged. Then, Es in the next steps 212 and 213
l ₀ is the sharpness signal captured by the previous large ranging frame, and Esl is the sharpness signal captured by the current large ranging frame. In step 212, the sharpness signal captured by the large distance measuring frame last time is set to Esl _0, and step 21
In Fig. 3, the sharpness signal that is currently captured is Esl.

At step 207, Ess ₀ and E
Although ss is compared, if these two values are almost the same, it is determined that the focus is achieved, and this flow is exited.

In step 207, if Ess ₀ and Ess are different from each other, Ess is calculated in the next step 208.
And Esl are compared. When Ess and Esl are almost the same, it is determined that the subject has moved or the subject has moved out of the small distance measuring frame due to panning, and this flow is exited. In step 208, Ess and Esl
If is different from, it is determined that the distance of the subject has changed significantly, the next step 209 is defocused, the counter value C is cleared in the next step 210, and the operation is restarted. In this case, the next time the process comes to this flow, if zooming is not in progress, it is determined that the focus is out of focus in step 201, so the flow advances to step 215, and the hill-climbing AF control is performed with the small distance measurement frame set in step 204. To start.

On the other hand, in step 214, Esl
₀ is compared with Esl, and if the two values are almost the same, it is determined that focus is achieved, and this flow is exited. Said Es
If l ₀ and Esl are different from each other, the focus is defocused in step 209, and then the counter value C is set in step 210.
Will be cleared and it will be restarted. When the distance measuring frame is large, it includes the area when the distance measuring frame is small, so Ess and Esl
Need not be compared with. However, if these two areas are different, the comparison performed in step 208 is also necessary. In this case, when zooming is not in progress, the hill-climbing AF is executed in step 215 when the next flow is reached.
Control is performed, and the size of the distance measuring frame at that time is the large distance measuring frame set in step 211.

When the hill-climbing AF control is started in step 215, it is checked in step 216 whether the driving direction of the focus lens is inverted twice during the hill-climbing AF control. If it has not been inverted twice, the hill climbing AF control is performed in the current state of the distance measuring frame, and then this flow is exited. However, when the image is inverted twice in step 216, the process moves to step 211 to enlarge the distance measurement frame,
The hill-climbing AF control is performed in a state where the distance measuring frame is large.

FIG. 3 shows a change in the level of the sharpness signal with respect to the position of the focus lens in two large and small distance measuring frames for an object which is out of the small distance measuring frames. In the figure, reference numeral 303 denotes a change in the sharpness signal due to a small distance measuring frame, and 304 denotes a change in the sharpness signal due to a large distance measuring frame. Reference numeral 306 indicates the movement of the focus lens. If the hill-climbing AF control is performed on such a subject with a small range-finding frame,
Since the sharpness signal is lowered at point 2, the driving direction of the focus lens is reversed. If the size of the focus detection frame remains small, the drive direction of the focus lens will continue to be reversed until the subject enters the focus detection frame, or noise will occur during the reversal. The focus will be misjudged and the blur will stop.
However, if the distance measuring frame is enlarged when the drive direction of the focus lens is inverted twice, the sharpness signal becomes 304, and the in-focus point 305 is known, so that the in-focus can be quickly achieved.

FIG. 4 is a diagram showing the size of the distance measuring frame. In the figure, A indicates a small distance measuring frame, and B indicates a large distance measuring frame. X and y in A (x, y) and B (x, y) respectively indicate the position in the vertical direction. By changing this point, the size of the distance measuring frame can be set within the range of the screen. It can be changed freely.

Incidentally, step 2 of FIG. 2 in the present embodiment.
In 16, it is determined whether or not the driving direction of the focus lens is inverted twice, but the number of inversions may be any number as long as it is two or more.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG.

In the first embodiment described above, it is checked in step 216 in FIG. 2 whether or not the driving direction of the focus lens has been inverted twice. In this embodiment, at this time, the first and second times are performed. The amount of movement of the focus lens at the time of inversion is confirmed.

FIG. 5 shows the movement of the focus lens in the case where the sharpness signal in the camera of this embodiment has noise and the driving direction is reversed. In the figure, 50
1 is a change in the sharpness signal due to the small ranging frame, 502 is a change in the sharpness signal due to the large ranging frame, 503 is an incorrect focus position due to the large ranging frame, and 504 is when the driving direction of the focus lens is reversed. , 505 is the true focus position, 506 is the movement of the focus lens, and 507 is noise on the sharpness signal. Then, 508 is to enlarge the distance measurement frame in step 211 of FIG. 2 in the above-described first embodiment.

In this figure, although the true focus point is 505, the driving direction of the focus lens is reversed due to the influence of noise 507, and the distance measuring frame becomes large.
It shows that blurring stops at position 503.
In this case, the movement amount 504 is quite small. Here, if this movement amount 504 is observed, and if this amount is small, it is necessary to forego making the distance measurement frame large,
The hill-climbing AF control can be performed without erroneously increasing the distance measurement frame due to the influence of noise.

[0039]

As described above, according to the camera of the present invention, if the driving direction of the focus lens is reversed a plurality of times during the hill-climbing AF control, the range-finding frame is made larger so that the object can be swiftly adjusted. Can be charred. Further, by observing the amount of movement of the focus lens when the driving direction is reversed, it is possible to perform a quick and reliable focusing operation as a whole without accidentally changing the distance measuring frame due to the influence of noise or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a camera according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure of the camera.

FIG. 3 is a diagram showing a level change of a sharpness signal with respect to a position of a focus lens in two large and small distance measuring frames in the same camera.

FIG. 4 is a diagram showing a size of a distance measuring frame in the camera.

FIG. 5 is a diagram of a camera according to a second embodiment of the present invention.
FIG.

[Explanation of symbols]

 6 Focus Lens (Lens Section) 10 Filter (Extraction Means) 13 Microcomputer (Change Means, Control Means, Focus Adjusting Means) 15 Driving Means 20 Camera Signal Processing Circuit (Selecting Means)

Claims (2)

[Claims] 1. A lens unit for performing focus adjustment, a driving unit for moving the lens unit in parallel with an optical axis, and an extracting unit for extracting a sharpness signal corresponding to a focus degree from an image signal.
A camera having focus adjusting means for controlling focus by controlling the driving means by the sharpness signal extracted by the extracting means, and changing means for changing a region in the screen where the sharpness signal is extracted, A camera comprising control means for controlling a region for extracting a sharpness signal to change when the driving direction of the lens unit is inverted a plurality of times. 2. The control means controls to prohibit or permit the change by the changing means according to a movement amount from when the driving direction of the lens portion is reversed to when it is reversed again. The camera according to item 1.