JPH04114570A - lens control device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a lens control device suitable for use in video equipment such as video cameras and electronic still cameras.

(Prior Art) In recent years, the development of video equipment such as video cameras and electronic cameras has been remarkable, and in particular, automatic focus adjustment devices (AF) and automatic aperture control devices (AE) have been developed to improve their functions and operability. , automatic white balance adjustment, zoom function, etc.
Various macro scanning functions have come to be standard equipment.

By the way, automatic focusing devices detect the sharpness of the screen from the video signal obtained by photoelectrically converting the subject image using an image sensor, etc., and control the focusing lens position so that the sharpness is maximized. A method that allows focus adjustment is becoming mainstream.

The sharpness is generally evaluated using the intensity of high frequency components of the video signal extracted by a band pass filter (BPF), or the blur width (of the edge part of the subject image) of the video signal extracted by a differentiation circuit, etc. Width) using detection strength, etc.

This is 1. When shooting a normal subject image, when the subject is out of focus, the level of high frequency components is small and the width of the blur becomes blurry and wide; The sharpness of the focusing lens decreases, and takes the maximum and minimum values respectively when the sharpness is completely in focus.Therefore, when the sharpness is low, the focusing lens is driven as fast as possible in the direction of increasing the sharpness. As the sharpness increases, the speed is reduced and the camera is controlled to accurately stop at the top of the sharpness peak.This method is generally called the mountain climbing autofocus method (mountain climbing AF).
It is called.

With the adoption of such an automatic focus adjustment device,
Conventionally, the operability of video cameras and the like, especially those used to shoot moving images, has improved dramatically and has become an essential requirement in recent years.

In addition to improving operability through the adoption of AF, zoom lenses have been adopted as standard in order to expand the shooting range and functions by making it possible to deal with more shooting conditions. However, in the wide macro shooting area, the focus is adjusted by operating the zoom lens, and the focus control method is different from that in the normal area. Focus adjustment was performed manually, which hindered improvements in operability.

(Problem to be Solved by the Invention) However, in order to automate focus adjustment in the wide macro area, it is difficult to simply control the zoom lens in the wide macro area by mountain climbing AF based on focus detection information. Mountain climbing AF in macro area
When this is done, there is a problem that the response at the start of wide macro AF is slow. This is because the focusable subject rejection in the wide macro area is extremely wide, from just in front of the lens to infinity, so if the zoom lens is not positioned appropriately when starting wide macro AF, it is easy to lose sight of the subject. It is.

(Means for Solving the Problems) The present invention has been made to solve the above-mentioned problems, and is characterized by a first region and a second region closest to the first region. a focus adjustment means capable of performing a focusing operation in a region; and an operation region switching means for switching an operation region of the focus adjustment means between the first region and a second region, the operation region switching means , when the operating region of the focus adjustment means is switched from the first region to the second region, the focus adjustment means is stopped at a position where the focus adjustment means is driven a predetermined amount in the close direction within the second region; The lens control device is configured to set the stop position as the initial position of the focusing operation in the second area.

(Function) This greatly improves the responsiveness of focus adjustment operations in the wide macro area, especially the responsiveness at the start of AF operation within the wide macro area, in cameras that can focus in the normal area and wide macro area. will be improved.

(Embodiment) Hereinafter, an embodiment of the automatic focusing device according to the present invention will be described in detail with reference to the respective figures.

FIG. 1 is a block diagram showing a case where the lens control device of the present invention is implemented in a video camera.

In the figure, ■ indicates the photographic lens system, which includes a focusing lens LA with a front lens for adjusting the focus.
, a zoom lens IB that performs focus adjustment in a wide macro area as well as zoom operation. The focusing lens IA is driven and controlled via a focusing motor drive circuit 9 and a focusing motor 1o.

Further, the zoom lens IB is driven and controlled via a zoom motor drive circuit 11 and a zoom motor 12. 2 is an aperture (iris) that controls the amount of incident light, and an iris drive circuit 7
The drive is controlled via the IG meter 8 for driving the aperture. 3 is an image sensor, such as a CCD, which charges and converts the subject image formed on the imaging surface by the focusing lens 1 into an image signal, and 4 amplifies the image signal output from the image sensor 3 to a predetermined level. The preamplifier 5 performs predetermined processing such as gamma correction, blanking processing, and addition of a synchronization signal to the video signal output from the preamplifier 4, converts it into a standardized standard television signal, and outputs it from the video output terminal. It is a process circuit. The television signal output from the process circuit 5 is supplied to a video recorder (not shown), an electronic viewfinder, or the like.

Further, 6 inputs the video signal output from the preamplifier 4, and connects a 1g meter 8 via an iris drive circuit 7 to control the opening amount of the diaphragm 2 so that the level of the video signal is constant at a predetermined level. This is an iris control circuit that automatically controls.

13 is a band pass filter (BPF) that extracts high frequency components necessary for focus detection from the video signal output from the preamplifier 4; The focus detection circuit uses the property that the blur width of the subject decreases as it approaches the in-focus state. The focus detection method itself using this blur width detection circuit is well known, for example, from Japanese Patent Laid-Open No. 103616/1983, and therefore a detailed explanation thereof will be omitted.

Reference numeral 15 denotes a gate circuit that applies a gate to the outputs of the band pass filter 13 and the blur width detection circuit 14, and allows only signals corresponding to a designated area on the imaging screen to pass through, and a gate pulse supplied by a logic control circuit 21, which will be described later. Accordingly, only the signal corresponding to a specified area in the video signal for one field is passed through, thereby extracting a high frequency component at an arbitrary position within the imaging screen. You can set the area. Reference numeral 16 denotes a peak position detection circuit that detects the position in the horizontal and vertical directions within the imaging screen where the peak value of the higher frequency component in the video signal corresponding to the focus detection area extracted by the gate circuit 15 is obtained. This peak position detection circuit is
The peak position detected in the 71 field period is
The focus detection area is divided into a predetermined number of blocks in the horizontal and vertical directions, and it is detected in which block the focus detection area is located, and its horizontal and vertical coordinates are output.

Further, 17 is a lens operation reading circuit that reads various control operations regarding the lens such as wide macro AF operation and high speed shutter.

Further, 18 is a focus encoder that detects the moving position of the focusing lens IA, 19 is a zoom encoder that detects focal length information varied by the zoom lens IB, and 20 is an iris encoder that detects the aperture amount of the diaphragm 2. This detection information is supplied to the logic control circuit 21.

Reference numeral 21 denotes a logic control circuit that centrally controls the entire system, and is composed of, for example, a microcomputer. ). This logic control circuit operates on the bandpass filter 1 outputted from the peak position detection circuit 16.
The peak value and its peak position coordinates within one field period of the high frequency component based on the output of 3, the blur width information based on the output of the blur width detection circuit 14, and the detection information from each encoder are taken in and processed into a predetermined algorithm. Therefore, based on these time-series changes, the position, size, movement direction, and movement response speed of the focus detection area on the imaging screen are set, that is, the subject is tracked.
It calculates the moving direction and moving speed of the focusing lens to obtain a focused point.

That is, based on the peak value within one field period of the high frequency component based on the output of the bandpass filter 13 and the coordinates of the peak position, the movement of the subject is detected for each field, and the changed peak position, that is, the subject position is detected. In order to set a focus detection area at a position centered on , a gate pulse is supplied to the gate circuit 15 to control opening and closing, and only a portion of the video signal corresponding to the focus detection area of the video signal is allowed to pass through.

Furthermore, the logic control circuit 21 performs focus detection on the subject and performs focus adjustment based on the video signal corresponding to the focus detection area set as described above. That is, the blur width information supplied from the blur width detection circuit 14 and the peak value information of the high frequency component supplied from the band pass filter 13 are taken in, and the blur width in the l field period is minimized and the peak value of the high frequency component is maximized. (Drive the focusing lens IA to
Supply control signals such as rotation/stop to achieve this.

At this time, the logic control circuit 21 adjusts the size of the focus detection area according to the degree of focus and the depth of field calculated from the aperture value and focal length detected by the aperture encoder 20 and zoom encoder 19. control the speed, movement range, and movement response speed.

In this way, it is possible to keep the camera in focus while tracking a moving subject image.

The reason why the blur width signal output from the blur width detection circuit 14 and the peak value of the high frequency component output from the band pass filter 13 are used for focus detection in the present invention is based on the following rationale.

In other words, the bokeh width approaches the in-focus point (becomes a small value and becomes the minimum at the in-focus point, and is less affected by the contrast of the subject, so it has the advantage of being able to obtain high focus detection accuracy, but the dynamic range is low. If it is narrow and far out of focus, it will not be possible to obtain sufficient detection accuracy.

On the other hand, high-frequency components have a wide dynamic range and can obtain an output according to the degree of focus even if they are far out of focus, but they are greatly affected by contrast, and blur width information Focusing accuracy cannot be obtained.

Therefore, by combining these, it is possible to realize a focus detection method with a wide dynamic range and high detection accuracy near the in-focus point.

Next, automatic focusing operation in a wide macro area, which is the gist of the lens control device of the present invention, will be explained step by step with reference to the flowchart shown in FIG.

In FIG. 2, when the lens control operation by the logic control circuit 21 is started, in step S1, the lens operation The reading circuit 17 detects the presence or absence of the wide macro AF start signal, and if the wide macro AF start signal is not output and photography is being performed in the normal area, the process moves to step S2 and the previous step is performed. This is an AF operation in the normal region (hereinafter referred to as normal AF mode) performed by driving the ball focusing lens.

The operation itself to switch to wide macro shooting mode is to automatically move the zoom lens to the wide macro area by operating an operation unit (not shown), and then set the wide macro AF mode to the wide macro shooting mode.
mode.

In step S1, if the wide macro AF mode is not set and the wide macro AF start signal is output, the process advances to step S3 to shift to the wide macro AF mode, and focus by operating the zoom lens. The control mode is entered, and initial settings in the wide macro AF operation mode are performed. This initial setting is a main part of the present invention, and details will be described later.

After completing the initial settings in step S3, the process proceeds to step S4, where a wide macro AF control operation is performed, and actual focusing operation becomes possible by driving the zoom lens without using the focusing lens.

In step S5, the lens operation reading circuit 17 determines whether or not to continue the wide macro AF operation by detecting whether or not an operation command to cancel the wide macro operation has been output. AF
When a signal that interrupts the operation is detected, step S
The process moves to the wide macro area AF post-processing routine in step S6, and in other cases, the process moves to the wide macro AF control routine in step S4 to continue the wide macro AF operation.

In the wide macro area AF post-processing routine of step S6, the zoom lens is forced to escape from the wide macro area to the normal area, and the control returns to the wide macro area AF start signal detection routine of step Sl. This is to prepare for the occurrence of wide macro AF operation.

Next, in the flowchart in FIG. 2 mentioned above,
The control operation of the wide macro area AF initial setting routine, which is the gist of the present invention, will be explained in detail using the flowchart shown in FIG.

In step S1 in FIG. 2, it is detected that the wide macro AF mode has been set by the wide macro start signal, and when the wide macro AF initial setting routine processing in step S3 is started, immediately step S31 in FIG.
Shifts to the focusing lens motor control routine,
Stop the focusing lens drive motor that was driving the front focusing lens. This is because in the wide macro area, even if the front focusing lens moves, it has no effect on the focal state.

Thereafter, in the zoom lens movement routine of step S32, the zoom lens is moved to the wide macro area at the highest speed.

Step S33 is a wide macro area detection routine, which analyzes the zoom lens position signal corresponding to the zoom lens position detected by the zoom lens encoder in FIG. 1, and detects whether the zoom lens has entered the wide macro area. It is something to do.

If it is detected in step S33 that the zoom lens has entered the wide macro area, control is transferred to a counter initialization routine in step S34. In other cases, control is returned to the zoom lens movement routine of step S32, and the operation of driving the zoom lens to the wide macro area at the highest speed is continued. 7 steps S3
In the counter initial setting routine of 4, wide macro AF
Sets how long the initial position of the zoom lens within the wide macro area (i.e. the position to start AF operation within the wide macro area) should be kept within the wide macro area when performing the operation. It is something to do. Here, it is assumed that, for example, a period of 30 fields is set, and after the zoom lens enters the wide macro region, it is driven at the highest speed to the close side for 30 fields and is stopped at a position.

Steps S35 to S37 are a zoom lens movement routine for moving the zoom lens to its initial position.

Step S35 is a routine for driving the zoom lens in the close-up direction, that is, the wide-angle direction, at the maximum speed. Step 336 is a countdown routine for decrementing the counter set value every field. Step S37 is a routine for determining whether the counter set value has reached O or not. This is a routine to determine.

That is, the zoom lens is driven at the highest speed in step S35, the counter value is decremented for each field in step S36, and if it is determined in step S37 that the value has become 0, the wide macro AF initial setting routine is executed. Then, control is transferred to the wide macro control routine of step S4 in FIG. If the counter value is not 0, the process returns to step S35 and the zoom lens continues to move at high speed until the counter value becomes 0. As a result, after the zoom lens enters the wide macro area, it is stopped at the position where it was driven at the highest speed for 30 fields.

Here, the reason why the zoom lens is moved to a predetermined position within the wide macro area without stopping at the boundary between the normal area and the wide macro area will be explained.

Theoretically, at the telephoto end of the wide macro area, an object at an infinite distance is in focus, and at the wide end, an object directly in front of the lens is in focus. Therefore, when starting wide macro AF, if you stop the zoom lens at a position immediately after entering the wide macro area, for example when trying to focus on a subject at a distance of about 10 cm from the lens, the response will be very high. becomes late. This is based on the rotation angle of the zoom lens within the wide macro area.
This is because the distance of the subject to be focused on is very wide, so even a small rotation angle will cause a large amount of blur. Therefore, when a zoom lens is positioned to focus on an object at infinity, an object at a distance of 10 cm is severely blurred, and it takes time to capture the object. Furthermore, photographers who wish to perform wide macro AF have little intention of photographing a subject that is at infinity from the beginning (in most cases, they try to focus on a subject that is within about 10 cm).

Therefore, in the present invention, when initializing wide macro AF,
The zoom lens is moved in advance to a position where a subject of about 10 cm is in focus, thereby improving the responsiveness of the subsequent wide macro AF operation. The setting of this stop position, that is, the initial position at the start of the wide macro AF operation, can be appropriately selected by changing the set value of the counter according to the driving speed of the zoom lens.

In this way, when performing an AF operation in a wide macro area, especially when switching from a shooting state in a normal area to a wide macro AF mode, the operation can be performed quickly and smoothly.

According to the above-described embodiment, the counter is configured to count the drive time of the zoom lens at its maximum speed in order to cause the zoom lens to enter a predetermined position within the wide macro area, but the present invention is not limited to this. Instead, the initial position of the zoom lens may be set by detecting the position from the zoom encoder.

However, in this case, it goes without saying that the zoom encoder must be capable of detecting a predetermined position at which the zoom lens should be stopped within the wide macro area.

Further, in the above embodiment, the initial setting position of the zoom lens was set to focus on the subject approximately 10 cm from the lens, but the invention is not limited to this, and the individual optical systems,
It may be set in consideration of usage conditions.

(Effect of the invention) As described above, in the present invention, wide macro A
At the time of initial setting of F, the initial setting position of the zoom lens is set to an appropriate position taking into account the photographer's intention, and wide macro AF operation is started from this position, so that the initial setting position of wide macro AF operation is Its practical effects are significant, such as significantly improving responsiveness, improving operability, and being able to respond to sudden changes in shooting conditions.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration when the lens control device according to the present invention is applied to a video camera, and FIG. 2 is a flowchart for explaining the control operation by the lens control device according to the present invention. FIG. 3 is a flowchart for explaining the initial operation for setting the initial position of the zoom lens at the start of wide macro AF in the flowchart of FIG.

Claims (1)

What is claimed is: a focus adjusting means capable of performing a focusing operation in a first region and a second region closer to the first region; and a second area, and the operating area switching unit is configured to switch the operating area of the focus adjustment means from the first area to the second area, The means is stopped at a position where the means is driven a predetermined amount in the close direction within the second area, and the stopping position is moved to the second area.
1. A lens control device characterized in that the lens control device is configured to set an initial position of a focusing operation in a region.