JPH06141224A - Automatic focusing adjusting device - Google Patents

Abstract

PURPOSE:To obtain an automatic focusing adjusting device capable of performing the focusing adjustment of an optical system by using a one- dimensional image pickup element without requiring complicated process or control. CONSTITUTION:A line CCD 6 outputs an image signal of one line in the vertical direction of an image-forming plane 5 at every travel of one step according to the rotation of a CCD travel motor 8, and the image signal is amplified by an AGC amplifier 10, and is inputted to a threshold processing circuit 11. The threshold processing circuit 11 obtains the binary image signal by using a threshold value inputted from a controller 13 corresponding to luminance, and outputs it to an edge counter 12. The edge counter 12 counts the number of edges of an inputted binary signal. and outputs it to the controller 13. The controller 13 controls a motor driving circuit 14 corresponding to the number of edges of the inputted binary signal, and drives an image pickup lens 1 to a focusing point by driving by a lens travel motor 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focus adjusting device for automatically adjusting the focus of an optical system in an electronic image pickup device.

[0002]

2. Description of the Related Art As a conventional automatic focus adjusting device, FIG.
The structure shown in is known. That is, the imaging lens 5
0 is movable in the optical axis direction, and area CC is behind
D51 is arranged. The image signal output from the area CCD 51 is amplified by the AGC amplifier 52 and input to an image signal processing unit (not shown), and the BPF 5
Input to 3. The BPF 53 passes a predetermined frequency band of the input image signal and outputs it to the detection circuit 54, and the detection circuit 53 detects the contrast signal contained in the band and inputs it to the peak detection and control circuit 55. The peak detection and control circuit 55 detects the peak of the contrast signal input from the detection circuit 53 and controls the lens movement motor 56. As a result, the image pickup lens 50 moves in the optical axis direction, and when the contrast signal reaches a peak, the peak detection and control circuit 54 stops the lens moving motor 55 to position the image pickup lens 50 at the focal point. .

[0003]

However, in such a conventional automatic focus adjusting device, the focus adjustment is performed by moving the image pickup lens 50 to a position where the contrast signal of the two-dimensional image data has a peak. Is configured to do. Therefore, it is premised that there is an image pickup device that outputs two-dimensional image data such as the area CCD 51, and when a one-dimensional image pickup device such as a line CCD is used, the system of this device should be adopted as it is. I can't. Of course, even when a one-dimensional image sensor is used, even if a one-dimensional image sensor is used, complicated control such as accumulating one-dimensional data in a memory to generate two-dimensional data can be performed. Focus adjustment may be possible with this method, but if such control is performed, data processing and control contents become complicated.

The present invention has been made in view of the above conventional problems, and the focus of an optical system can be automatically adjusted by using a one-dimensional image pickup device without complicated processing and control. An object of the present invention is to provide a focus adjustment device.

[0005]

In order to solve the above-mentioned problems, according to the present invention, an optical system for forming an image of a subject, and an image forming surface of the optical system is scanned by a one-dimensional image pickup device to obtain a luminance signal. Is output to pick up a subject image, a binarizing unit that binarizes the luminance signal output from the image pickup unit, and an edge of the signal binarized by the binarizing unit is counted. Counting means and a control means for controlling the optical system so that the count value of the counting means becomes maximum.

[0006]

In the above structure, the one-dimensional image pickup device scans the image forming surface of the subject image formed by the optical system to output a luminance signal, and the luminance signal is binarized by the binarizing means. The edges of the binarized signal are counted by the counting means, and the control means controls the optical system so that the count value of the counting means becomes maximum. That is, when the luminance signal is binarized using a certain threshold value, the number of edges of the binarized signal becomes maximum at the focal point of the optical system. Therefore, the optical system is adjusted to the in-focus point by controlling the optical system so that the number of edges becomes maximum.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. That is, in this embodiment, the present invention is applied to an image pickup apparatus that picks up an image using a line CCD that is a one-dimensional image pickup element, and the image pickup lens 1 shown in FIG.
It is movable in the optical axis direction as the ring gear 2 rotates, and a pinion 4 fixed to the rotation shaft of the lens moving motor 3 is meshed with the ring gear 2. Behind the image pickup lens 1, a line CCD 6 which is movable in the horizontal direction along an image forming surface 5 of the image pickup lens 1 is arranged. The line CCD 6 is formed by arranging elements in parallel in a vertical direction, and a lower end portion thereof is fixed to a nut 7, and a long bolt 9 provided on a rotation shaft of a CCD moving motor 8 is screwed into the nut 7. Has been done. Therefore, when the CCD moving motor 8 operates and the bolt 9 rotates, the line CCD 6 moves in the horizontal direction integrally with the nut 7 when the bolt 9 rotates.

At this time, the line CCD 6 outputs an image signal for one line in the vertical direction of the image plane 5 every time it moves in the horizontal direction by one step, and this image signal is amplified by the AGC amplifier 10 to 2 It is input to the digitization circuit 11.
The binarization circuit 11 binarizes the image signal according to the brightness according to the threshold value input from the controller 13, and outputs the binarized image signal to the edge counter 12. The edge counter 12
Counts the number of edges of the input binary signal,
Output to the controller 13. The controller 13 is
The state of the motor drive circuit 14 is controlled according to the number of edges of the input binary signal, and the lens moving motor 3 and the CCD moving motor 8 are controlled by the operating state of the motor driving circuit 14.
And work. In addition, on the image plane 5, a predetermined range in the center is line C when the focus of the imaging lens 1 is adjusted.
The CD 6 is a detection zone Z for detecting the brightness.

Next, the operation of this embodiment having the above configuration will be described with reference to the flow chart shown in FIG. That is, the AF (not shown) is set in a state in which the subject can be imaged.
When the start switch is operated, the controller 14 starts the operation according to this flowchart. Then, first, the motor drive circuit 14 is activated to operate the lens moving motor 3 to move the imaging lens 1 to an intermediate position between the closest distance and infinity (S1). Continuously, CCD moving motor 8
Is operated to move the line CCD 6 to the entrance of the detection zone Z (S2). As a result, the line CCD 6 outputs an image signal for one line at the entrance of the detection zone Z,
The image signal for one line is amplified by the AGC amplifier 10 and input to the binarization circuit 11.

At this time, a predetermined threshold value is input in advance from the controller 13 to the binarization circuit 11, and the binarization circuit 11 outputs the predetermined threshold value input in advance and the luminance component of the image signal. After the comparison, the binarized signal resulting from the comparison is output to the edge counter 12. The edge counter 12 counts the number of edges in the binarized signal for one line and outputs it to the controller 13.

The controller 13 determines whether or not the edge count, which is the count value of the number of edges of the input binarized signal for one line, is a peak (S3). Then, it is determined whether or not it has moved to the exit of the detection zone Z (S4). If the line CCD 6 has not moved to the exit of the detection zone Z, the line CCD 6 is moved horizontally by one step (S5), and the determination from S3 is executed.

That is, by the loop of S3 to S5, the line CCD 6 moves from the entrance of the detection zone Z toward the exit by one.
Move step by step, step by step,
In S3, it is determined whether the edge count has reached a peak. The determination in S3 is performed by, for example, comparing the number of edges of the binarized signal for one line that is sequentially input with the number of edges that is a predetermined peak value. When the edge CCD exceeds the predetermined peak value at the position where the line CCD 6 is in the detection zone Z, the determination in S3 is YES, and the loop is exited.
CD6 stops at that position.

On the other hand, even if the line CCD 6 is moved step by step from the entrance to the exit of the detection zone Z and the edge number of the line does not exceed the predetermined peak value at any point, the line CCD 6 is operated. After reaching the exit of the detection zone Z, the determination in S4 is YES. In this case, the line CCD 6 is unavoidably stopped at the center position of the detection zone Z (S6). Therefore, when the next step S7 is executed, the line CCD 6 is located at the position where the edge count reaches the peak or the detection zone Z.
Has stopped in one of the central positions.

Then, in S7, the threshold having the largest value among the plurality of thresholds stored in advance in the ROM of the controller 13 is set in the binarization circuit 11. Then, the binarization circuit 11 causes the line CC that has stopped moving.
The image signal for one line at the position input from D6 via the AGC amplifier 10 is compared with the threshold value to be binarized, and the edge counter 12 counts the number of edges of the binarized signal and inputs it to the controller 13. To do. The controller 13 determines whether or not the edge count reaches a peak by comparing the edge count, which is the number of edges counted by the edge counter 12, with a predetermined peak value (S8).

If the edge count does not reach the peak, it is determined whether the threshold value is changed to the minimum (S
9) If the threshold value is not changed to the minimum, the threshold value is decreased by one step (S10), and the determination from S8 is repeated. Therefore, the loop of S8 to S10 is repeated until the edge count reaches the peak or the threshold becomes the minimum, whereby the binarization circuit 11 outputs the same image signal to different thresholds every time the threshold is decreased by one step. And binarize and output.

As a result, as shown in FIG.
Even for the image signals for the lines, the binarization circuit 11 outputs different binarization signals depending on the threshold value. Further, in the example shown in FIG. 3, the number of edges of the binarized signal is the largest at the threshold value, and if this edge number exceeds the predetermined peak value, the determination in S8 is YES at the threshold value. Therefore, the threshold value used for the drive control of the imaging lens 1 described below is determined to.

On the other hand, if the number of edges of the line does not exceed the predetermined peak value at any threshold even if the threshold is changed to the minimum, the determination in S9 is YES.
Therefore, in this case, the threshold value is unavoidably set to the center value of the large and small spaces (S11). Therefore, when the processing up to S11 is completed, firstly, the line CCD 6 is in a state of being stopped at either the position where the edge count reaches the peak or the center position of the detection zone Z, and
Second, the binarization circuit is in a state in which either the threshold value when the edge count reaches the peak or the central value is set.

Then, according to the above procedure, the line CCD 6
After determining the position and the threshold value, the driving control of the imaging lens 1 after S12 is started, and the imaging lens 1 is first moved to infinity (∞) (S12). Then, the binarization circuit 1
In the state where the image pickup lens 1 is at infinity, reference numeral 1 compares the image signal for one line of the position input from the line CCD 6 through the AGC amplifier 10 with the threshold value to binarize it, and the edge counter 12 Inputs the number of edges of the binarized signal to the controller 13. The controller 13 determines whether or not the edge count reaches a peak by comparing the edge count, which is the number of edges counted by the edge counter 12, with a predetermined peak value (S13).

If the edge count does not reach the peak, it is judged whether or not the image pickup lens 1 has moved to the closest point (S14). If not, the image pickup lens 1 is extended. (S15), the determination from S13 is repeated. Therefore, until the edge count reaches a peak or the imaging lens 1 moves to the closest position, S
The loop of 13 to S15 is repeated, and every time the image pickup lens 1 is extended, the binarization circuit 11 binarizes the image signal corresponding to the focus state at the position and outputs the binarized image signal.

At this time, as shown in (a) and (b) of FIG. 4, the output waveforms at points (a) and (b) of FIG. 1 are waveforms (a) in which the detail of the image exists at the time of focusing. On the other hand, the waveform (b) in which details are lost when the object is out of focus is obtained. In addition, the waveforms (a) and (b) are the binarization circuit 11
Then, when binarized using the same threshold value, the waveform (a) at the time of focusing is output as a binarized signal (a ′) having a large number of edges, while the waveform (a) at the time of non-focusing ( b) is output as a binarized signal (b ') having a small number of edges. Then, as shown in (c) of the figure, if the edge count reaches a peak, the imaging lens 1 is in focus at this point, and the determination in S14 is YES, and AF (autofocus) is performed. Adjustment). By the end of this AF, the imaging lens 1
The lens moving motor 3 driving the lens from infinity to the closest direction stops, and the imaging lens 1 stops at the in-focus position.

On the other hand, even if the image pickup lens 1 is extended,
When the edge count of the binarized signal does not reach the peak, the determination in S14 is YES when the imaging lens 1 reaches the closest position. Then, in this case, it is unavoidable to move the imaging lens 1 to an intermediate position between infinity and the closest distance (S16), and the AF is ended. That is, when the subject is white, the contrast component of the image signal is very small,
Even if this is binarized, the number of edges may not reach a predetermined peak value in some cases. Therefore, in this case, the imaging lens 1 is moved to the intermediate position where there is a high possibility of focusing, and the AF is ended.

In the description of the embodiments, the focusing procedure for actually picking up an image of a subject has been described, but the closest focusing position of the image pickup lens can be set in the manufacturing process by the similar focusing procedure. That is, as shown in FIG. 1, a test chart T on which a predetermined striped pattern is drawn is placed at a known distance from the image pickup lens 1, and the test chart T is used as an object to operate in accordance with the above-mentioned flowchart to achieve a focused state. To Then, if the image pickup lens 1 is extended by the amount of extension corresponding to the known distance, the image pickup lens becomes the closest position. Therefore, by defining this position as the closest position and performing the adjustment, the imaging lens 1 can be quickly
The closest position of can be set.

[0023]

As described above, according to the present invention, the luminance signal output from the one-dimensional image pickup device is binarized, and the optical system is controlled so that the edge of the binarized signal is maximized. did. Therefore, in an image pickup apparatus using a one-dimensional image pickup element, without complicating the data processing or the apparatus,
The automatic focus adjustment function can be easily obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart showing an automatic focus adjustment procedure of the embodiment.

FIG. 3 is a diagram showing a relationship between an image signal for one line and a binarized signal according to a threshold value.

FIG. 4 is a diagram showing an example of states of (a) to (c) of FIG.

FIG. 5 is a block diagram showing a conventional automatic focus adjustment device.

[Explanation of symbols]

 1 Imaging Lens 6 Line CCD 11 Binarization Circuit 12 Edge Counter 13 Controller

Claims (1)

[Claims] 1. An optical system for forming an image of an object, an image pickup means for scanning an image forming surface of the optical system with a one-dimensional image pickup element to output a luminance signal, and picking up an image of an object, and an output from the image pickup means. The binarized binarized luminance signal 2
And a counting means for counting the edges of the signal binarized by the binarizing means, and a controlling means for controlling the optical system so that the count value of the counting means becomes maximum. An automatic focus adjustment device characterized in that