JPH05145827A - Automatic focusing controller - Google Patents

Abstract

PURPOSE:To accurately discriminate focusing by extracting different period number component at a same point from an image pickup signal and using the signal, thereby detecting the focusing state. CONSTITUTION:A peak hold circuit 17 holds a maximum value for one vertical operation period and a sample-and-hold circuit 18 holds data in matching with a peak hold timing signal H of the peak hold circuit 17. In this case, each holding value is obtained by extracting different frequency components of a same point in the video signal, and the result is respectively A/D-converted by A/D converters 19, 20. Moreover, a comparator 40 compares the quantity of the outputs of the A/D converters 19, 20 and a switch 41 is subjected to switching control by the output and the switch 41 is controlled so as to connect a larger output between the A/D converters 19, 20 to a post-stage circuit. Then based on a selected focus detection signal, a motor speed discrimination circuit 12 sets the speed of the focusing motor 6 in response to the focusing.

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 suitable for use in a video camera or the like.

[0002]

2. Description of the Related Art As an automatic focus adjusting device used in a video camera such as a video camera, a high frequency component is extracted from a video signal obtained from an image pickup device such as a CCD, and the high frequency component is maximized. A so-called hill-climbing system is known in which a photographing lens is driven to perform focusing.
Such an automatic focus adjustment method does not require a special optical member for focus adjustment, and has an advantage of being able to focus accurately regardless of distance regardless of distance. This type of automatic focus adjustment method will be described with reference to the drawings.

Reference numeral 1 denotes a focusing lens, which is moved by a focusing motor 6 in the optical axis direction for focusing. The light passing through the lens 1 is imaged on the image pickup surface of the image pickup device 2, photoelectrically converted into an electric signal, and output as a video signal. The video signal is amplified to a predetermined level by the amplifier 3, input to the process circuit 4 of the camera, converted into a standard television signal, and input to a bandpass filter (hereinafter referred to as BPF) 8. .. The BPF 8 extracts high-frequency components from the video signal, extracts only the video signal corresponding to the focus detection area set in a part of the screen by the gate circuit 9, and the peak hold circuit 10 makes it an integral multiple of the vertical synchronization signal. Perform peak hold at synchronized intervals. Hereinafter, this peak-held value will be referred to as the focus voltage value B.

Based on the focus voltage value B, the motor speed determination circuit 12 sets the speed of the focusing motor 6 according to the degree of focus. That is, the speed of the motor 6 is varied by instructing the motor driver 7 to be fast during large blur and slow during small blur. Further, the motor direction determination circuit 11 sets the motor drive direction in the direction in which the focus voltage value B increases. That is, so-called hill climbing control, which is well known in the past, is performed. However, since the motor direction determination circuit 11 does not know the direction in which the focus voltage value B becomes the maximum at first, the motor direction determination circuit 11 operates the motor 6 for the time being and rotates until the direction in which the focus voltage value B increases can be determined. Continue. If the lens 1 hits the end during this time, the focus encoder 5 discriminates this and the motor 6 is rotated in the reverse direction.

[0005]

However, in the above-mentioned conventional example, the focus voltage changes not only according to the degree of blurring of the subject but also according to the type and contrast of the subject, so that the degree of focus cannot be accurately determined. There was a point.

That is, in the case of the conventional example, for a normal subject, the motor speed determination circuit 12 increases the motor speed during large blurring and slows down the motor speed during small blurring, thereby eliminating hunting and achieving high-speed automatic focusing. Adjustment operation is possible. However, in low contrast subjects,
Since the focus voltage was low, the motor speed could not be slowed down even with small blurring, and hunting was often repeated near the in-focus state.
Further, in a high-contrast subject, the focus voltage is high, so that the object is decelerated at the time of large blurring, and it may take a very long time to focus.

Further, in order to enable the focus detection operation even during large blurring, in addition to a bandpass filter for high pass that has a high cutoff frequency for focus detection, a cut is performed so that the direction of the focus can be recognized even in large blurring. A method has been proposed in which a plurality of band pass filters with low off frequencies are provided, and focus adjustment is possible even in the vicinity of the in-focus point and in the state of large blurring. However, during imaging signals output in time series such as video cameras. In the method of extracting the signal for performing more in-focus detection, the value that maximizes the output of each filter is usually evaluated, so the signals of these multiple filters do not always indicate the same point on the imaging screen, and Depending on the state, each bandpass filter may be evaluating a different point on the screen, and if there is a difference in distance between these points, it may cause perspective conflict, resulting in insufficient focus detection characteristics. Rukoto were those that can not be.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and an automatic focus adjusting device capable of performing a good automatic focus adjusting operation quickly and without causing hunting for any subject. The feature is that the image pickup means, the extracting means for extracting different frequency components at the same point from the image pickup signal output from the image pickup means, and the extracting means. An automatic focus adjustment device includes a detection unit that detects a focus state using the extracted signal and a focus adjustment unit that performs focus adjustment based on the output of the detection unit.

Another feature of the present invention is that the image pickup surface is selected from the image pickup means for photoelectrically converting a subject image formed on the image pickup surface to output an image pickup signal, and the image pickup signal output from the image pickup means. At the same point, the extraction means including a plurality of bandpass filters for extracting the first and second signal components having different frequency components from each other, and the signal extracted by the extraction means to calculate the in-focus state. An automatic focus adjustment device is provided with detection means for detecting and focus adjustment means for performing focus adjustment based on the output of the detection means.

Another feature of the present invention is that an image pickup means for photoelectrically converting an object image formed on an image pickup surface to output an image pickup signal, and an image pickup signal outputted from the image pickup means. More specifically, extraction means for extracting the first and second signal components having different characteristics and varying depending on the focus state, and one of the signals extracted by the extraction means are divided by the other to detect the in-focus state. Detection means,
An automatic focus adjusting device is provided with a focus adjusting means based on the output of the detecting means.

[0011]

As a result, different frequency components can be obtained at the same point on the image pickup screen, accurate focus detection can be performed, and a plurality of focus signal information pieces can be calculated to reduce low contrast. For example, the focus adjustment can be performed accurately and without malfunction regardless of the state of the subject.

Further, speed control and direction determination can be performed accurately.

[0013]

Embodiments of the automatic focus adjusting device of the present invention will be described in detail below.

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention. In the figure, the same components as those in the conventional example of FIG. 13 are designated by the same reference numerals, and the description thereof will be omitted.

The video signal amplified by the amplifier 3 to a predetermined level has a first band-pass filter (BPF) 13 for extracting a frequency component that changes depending on the focus state and a second B-pass filter.
It is input to the PF 14, respectively. Here is the second BPF
The pass center frequency of 14 is lower than the pass center frequency of the first BPF 13. The first BPF 13 extracts a high frequency specific frequency, and the gate circuit 9 extracts only a signal corresponding to a portion set in the focus detection area in the screen.
It is input to the peak hold circuit 17. Also the first B
Second BP in which a frequency lower than the output of PF13 is extracted
The output of F14 is input to the sample hold circuit 18.

The peak hold circuit 17 holds the maximum value during one vertical operation period, and at the same time, holds the timing signal H holding the value at the sample hold circuit 1.
Output to 8. The sample hold circuit 18 holds the data in accordance with the peak hold timing signal H of the peak hold circuit 17. That is, the hold value of the peak hold circuit 17 and the hold value of the sample hold circuit 18 are
It is obtained by extracting different frequency components at the same point in the video signal. The output of the peak hold circuit 17 and the output of the sample hold circuit 18 are the A / D converter 1
The signals 9 and 20 are analog-digital converted, output to the switch 41, and input to the comparator 40.

The comparator 40 includes A / D converters 19 and 20.
The output of the comparator is compared in magnitude, and the output of the comparator controls the switch 41.

The switch 41 is A / D by the comparator 40.
Switching is controlled so that the converters 19 and 20 are compared and the larger one is connected to the circuit in the subsequent stage. That is, of the outputs of the two BPFs having different pass frequency bands, the one with the higher level is used as the focus detection signal.

Based on the focus detection signal thus selected, the motor speed determination circuit 12 sets the speed of the focusing motor 6 according to the degree of focus. That is, the motor driver 7 is controlled so as to be fast during large blur and slow during small blur, and the motor speed is varied.

The motor direction determination circuit 11 sets the motor drive direction in the direction in which the signal increases based on the signal corresponding to the focus degree selected by the switch 41 and the measurement value of the focus encoder 5. That is, so-called mountain climbing control is performed. Since the motor direction determination circuit 11 does not know the direction in which the level of the signal selected by the switch 41 is the maximum at first, the motor direction determination circuit 11 drives the motor 6 in an appropriate direction for the time being, and if the signal level thereby increases, it drives in the same direction. If it decreases, the direction is determined by reversing. If the focusing lens 1 hits the end during this operation, the focus encoder 5 discriminates this to rotate the motor in the reverse direction.

As described above, the speed and the driving direction of the focusing lens are determined by using the signal having the higher signal level of the high and low frequency components at the same point on the image pickup screen.

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

As in the first embodiment, the image pickup signal amplified to a predetermined level by the amplifier 3 is first converted into digital data by the A / D converter 42. This digital data is filtered by digital signal processing in the next band pass filters BPF 43 and 44, respectively, and only specific frequency components are extracted. BPF 43,44 at this time
The frequency characteristics themselves to be extracted are BPFs 13 and 1, respectively.
It is almost equal to 4. Then, the gate circuit 45 extracts the digital data of only the focus detection region, and the peak hold circuit 46 extracts the maximum BPF 43 during one vertical scanning period.
The value of BPF 44 is held in the latch register 47 according to the peak hold pulse H at the same time that the value of BPF 44 is held. The peak hold output and the latch register output are added by the adder 48 and input to the motor direction determination circuit 11 and the motor speed determination circuit 12. Thereafter, the automatic focus adjustment operation is performed as in the first embodiment.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. This embodiment is based on the above-mentioned first,
The second embodiment is further improved to calculate different frequency components at the same point on the screen to improve the focus detection characteristic.

In FIG. 3, the video signal amplified to a predetermined level by the amplifier 3 is the first BPF 13 and the second BP.
Input to F14. Here, the pass center frequency of the second BPF 14 is lower than the pass center frequency of the first BPF 13. The first BPF 13 extracts a specific frequency, and the gate circuit 9 extracts only the signal corresponding to the portion set in the focus detection area in the screen and inputs it to the peak hold circuit 17. Also, the first BPF 13
The output of the second BPF 14 in which the frequency lower than the output of is extracted is input to the sample hold circuit 18.

The peak hold circuit 17 holds the maximum value in one vertical operation period, and at the same time, holds the timing signal H holding the maximum value in the sample hold circuit 1.
Output to 8. The sample hold circuit 18 holds the data in accordance with the peak hold timing signal H of the peak hold circuit 17. That is, peak hold 1
The holding value of 7 and the holding value of the sample hold 18 are obtained by extracting different frequency components at the same point in the video signal. The outputs of the peak hold circuit 17 and the sample hold circuit 18 are the A / D converters 19 and 2 respectively.
0, analog-to-digital conversion, respectively, and a divider 2
Input to 1.

In the divider 21, the output C of the A / D converter 19 (the value obtained by extracting the higher frequency) is used as the numerator for A / D.
Output D of converter 20 (value with lower frequency extracted)
The denominator is used as a denominator, and at the same time as the vertical scanning period ends, digital calculation is performed and the evaluation value A of the focus degree is output for each vertical scanning period. This evaluation value A is the motor direction determination circuit 1
1 and the motor speed determination circuit 12 are input. The motor direction determination circuit 11 determines the motor direction using the evaluation value A and transmits it to the motor driver. Further, in the motor speed determination circuit 12, in order to be proportional to the reciprocal of the evaluation value A,
The speed of the motor 6 is determined and transmitted to the motor driver 7. That is, when the evaluation value A is low and is far from the focal point,
The speed of the motor 6 is increased, the evaluation value A is high, and when the in-focus point is close, the speed of the motor 6 is decreased.

The motor driver 7 drives the focusing motor 6 in accordance with the given speed of the motor 6 and the direction of the motor 6, and adjusts the focusing lens 1 to perform automatic focus adjustment.

Now, the operation of the motor direction determination circuit 11 will be described with reference to the flowchart of FIG. In the motor direction determination circuit 11, first, the focus encoder 5
It is checked whether or not the edge is hit according to the input from (step 1). And when it hits the edge,
The direction of the motor 6 is reversed (step 2). If not, it is compared with the data A'in the previous field to determine whether the data A is increasing (step 3). As a result, if it is decreasing, the direction of the motor 6 is reversed (step 2), and if it is increasing, the same direction is maintained.

Next, using FIG. 5 and FIG. 6, the evaluation value of the third embodiment (FIG. 5) and the focus voltage B in the conventional example of FIG. 13 (FIG. 6).
Explain the difference. The focus voltage B has a low value even at the in-focus point for a subject having a low contrast, and a high value for a subject having a high contrast. On the other hand, the evaluation value A of Example 3 is a substantially constant value regardless of the contrast of the subject.

(Fourth Embodiment) FIG. 7 is a block diagram showing the structure of the fourth embodiment.

Similar to the third embodiment, the video signal amplified by the amplifier 3 to a predetermined level is first converted into digital data by the A / D converter 24. This digital data is respectively filtered by the third BPF 22 and the fourth BPF 23, and only specific frequency components are extracted.

At this time, the frequency characteristics extracted by the BPF 22 and the BPF 23 are almost equal to those extracted by the first BPF 13 and the second BPF 14 in the first embodiment, respectively. Then, the gate circuit 25 extracts the digital data of only the focus detection area, the peak hold circuit 26 holds the maximum value of the BPF 22 during one vertical scanning period, and at the same time, the peak hold pulse H is stored in the latch register 27. The value of BPF 23 is held. Hereinafter, the same automatic focus adjustment operation as in the third embodiment is performed.

(Embodiment 5) FIG. 8 shows a fifth embodiment of the present invention. An A / D converter 1 in the third embodiment is shown in FIG.
By bringing 9 and 20 in front of the peak hold circuit 17 and the sample hold circuit 18, an analog filter is used for the BPF, and the peak hold circuit 26 and the data latch register 27 are digital circuits for processing digital data. It was what I had. The operation itself is the same as that in each of the above-described embodiments. As described above, according to the present invention,
While determining the driving direction of the focusing lens based on the signal extracted from the image pickup signal by the plurality of extraction means, by detecting the focusing signal according to the degree of focus by dividing the extraction signal, Since the focusing lens is driven to the in-focus point by determining the driving speed of the focusing lens on the basis of this, it is possible to perform quick focus adjustment without hunting for any subject.

(Embodiment 6) Next, a sixth embodiment of the present invention will be described. In this embodiment, the performance of the direction determination and speed determination of the focusing motor in the systems of the above-mentioned third to fifth embodiments is further improved. It is an improvement.

FIG. 9 is a system block diagram of the sixth embodiment. The same components as those in the third embodiment shown in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. According to this embodiment, the divider 21 uses the output C of the A / D converter 19 (a value obtained by extracting a higher frequency) as the numerator and the A / D converter 2
The output D of 0 (a value obtained by extracting a lower frequency) is used as a denominator, digital calculation is performed at the same time as the vertical scanning period ends, and the evaluation value A of the focus degree is output every vertical scanning period. Up to Fig. The same as 2. The evaluation value A is input to the motor speed determination circuit 12. The motor speed determination circuit 12 determines the speed of the motor 6 so as to be proportional to the reciprocal of the evaluation value A, and informs the motor driver 7 of the speed. That is, when the evaluation value A is low and far from the in-focus point, the speed of the motor 6 is increased, and when the evaluation value A is high and the in-focus point is close, the speed of the motor 6 is decreased.

Further, the outputs C and A / of the A / D converter 19 are
The output D of the D converter 20 is compared in magnitude by the comparator 29, and by switching the switch 30 with the output of this comparator 29, the larger one of the output C and the output D is selected to be the data E. The data E is input to the motor direction determination circuit 11, and the motor direction determination circuit 11 uses the data E and the input from the focus encoder 5 to determine the direction of the motor 6 and transmits it to the motor driver 7.

The motor driver 7 drives the focusing motor 6 in accordance with the given speed of the motor 6 and the direction of the motor 6, and adjusts the focusing lens 1 to perform automatic focus adjustment.

Now, the operation of the motor direction determination circuit 11 will be described with reference to the flowchart of FIG. In the motor direction determination circuit 11, first, it is checked whether or not the edge is hit according to the input from the focus encoder 5 (step 1 '). When it hits the end, the direction of the motor 6 is reversed (step 2 '). If not, the data E'is compared with the data E'in the previous field to determine whether the data E is increasing (step 3 '). As a result, if it is decreasing, the direction of the motor 6 is reversed (step 2 '), and if it is increasing, the same direction is maintained.

The difference between the evaluation value in this embodiment and the focus voltage B of the conventional example shown in FIG. 3 is as described above with reference to FIGS. 5 and 6, and the focus voltage B is for a subject with low contrast. The value is low even at the in-focus point, and is high for subjects with high contrast. On the other hand, the sixth embodiment
The evaluation value A of is a substantially constant value regardless of the contrast of the subject.

The difference between the evaluation value A and the data E will be described with reference to FIG. When the same subject is taken, the evaluation value A is
The degree of focus can be known, but if the image is greatly blurred, the output does not change. On the other hand, although the data E has a difference in the value at the in-focus point depending on the subject, the slope of the mountain can be detected even with large blur. Therefore, the evaluation value A is suitable for the speed control of the motor 6, and the data E is suitable for the direction control of the motor 6.

(Embodiment 7) FIG. 12 is a block diagram showing the configuration of Embodiment 7.

Similar to the sixth embodiment, the video signal amplified by the amplifier 3 to a predetermined level is first converted into digital data by the A / D converter 24. This digital data is respectively filtered by the third BPF 22 and the fourth BPF 23, and only specific frequency components are extracted.

At this time, the frequency characteristics extracted by the BPF 22 and the BPF 23 are almost equal to those extracted by the first BPF 13 and the second BPF 14 in the first embodiment, respectively. Then, the gate circuit 25 extracts the digital data of only the focus detection area, the peak hold circuit 26 holds the maximum value of the BPF 22 during one vertical scanning period, and at the same time, the peak hold pulse H is stored in the latch register 27. The value of BPF 23 is held.

The peak hold output C and the latch register output D are added by the adder 28 to obtain the motor direction determination circuit 1
Input to 1. The output E of the adder 28 can improve the direction determination ability even during large blurring by adding a plurality of filter outputs. Also, the motor speed determination circuit 1
The evaluation value A obtained by dividing the output C by the output D by the divider 21 is input to 2 as in the sixth embodiment. Hereinafter, the same automatic focus adjustment operation as that of the first embodiment is performed.

[0046]

As described above, according to the automatic focus adjusting apparatus of the present invention, by obtaining different frequency components at the same point on the image pickup screen, it is possible to accurately and accurately not affect the state of the subject. A focus adjustment device can be realized.

Further, according to the present invention, the driving direction of the focusing lens is determined on the basis of the signals extracted from the image pickup signals by the plurality of extracting means, and the extraction signals are divided to determine the focusing degree. The focusing lens is driven to the in-focus point by detecting the corresponding focusing signal and determining the driving speed of the focusing lens based on this signal, so no matter what kind of subject, hunting is fast. Focus can be adjusted.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an automatic focusing apparatus according to the present invention,

FIG. 2 is a block diagram showing a second embodiment of the automatic focusing apparatus according to the present invention,

FIG. 3 is a block diagram showing a third embodiment of the automatic focus adjustment device of the present invention,

4 is a flowchart showing the operation of a motor direction determination circuit in the system of FIG.

5 is a characteristic diagram of an evaluation value A in the system of FIG.

6 is a characteristic diagram of a focus voltage B in the system of FIG.

FIG. 7 is a block diagram showing a fourth embodiment of the present invention,

FIG. 8 is a block diagram showing a fifth embodiment of the present invention,

FIG. 9 is a block diagram showing a sixth embodiment of the present invention,

10 is a flowchart showing the operation of the motor direction determination circuit in the system of FIG. 9 of the present invention,

11 is an evaluation value A and data E in the system of FIG.
Characteristic diagram of

FIG. 12 is a block diagram showing a seventh embodiment of the present invention,

FIG. 13 is a block diagram showing a configuration of a conventional automatic focus adjustment device.

Claims (4)

[Claims] 1. An imaging unit, an extraction unit for extracting different frequency components at the same point from the imaged signal output from the imaging unit, and a focus state is detected using the signal extracted by the extraction unit. An automatic focus adjustment device comprising: a detection unit; and a focus adjustment unit that performs focus adjustment based on the output of the detection unit. 2. An image pickup means for photoelectrically converting a subject image formed on an image pickup surface to output an image pickup signal, and an image pickup signal outputted from the image pickup means, which correspond to the same point on the image pickup surface. An extracting unit including a plurality of bandpass filters for extracting first and second signal components having different frequency components; a detecting unit for detecting a focus state by calculating a signal extracted by the extracting unit; An automatic focus adjusting device comprising: a focus adjusting means for adjusting the focus based on an output of the detecting means. 3. The detecting means is means for dividing a signal component having a high frequency among the first and second signal components by a signal component having a lower frequency and normalizing a high frequency component by a low frequency component. An automatic focusing device characterized by the above. 4. An image pickup means for photoelectrically converting a subject image formed on an image pickup surface to output an image pickup signal, and a first device having characteristics different from each other and changing according to a focus state.
And an extracting means for extracting the second signal component, an extracting means for extracting, a detecting means for detecting a focus state by dividing one of the signals extracted by the extracting means by the other, and the detecting means. An automatic focus adjusting device, comprising: a focus adjusting unit that adjusts the focus based on the output of the.