JPH08289193A - Auto-focusing video camera - Google Patents

Abstract

PURPOSE: To suppress an excess when a lens goes past beyond a focusing position to a minimum and to quickly and smoothly perform automatic adjustment as sharing a digital integrator with the one for focusing evaluation value calculation that is the base of a focusing operation, the one for exposure evaluation value calculation that is the base of exposure adjustment and the one for white balance adjustment that is the base of white balance adjustment. CONSTITUTION: A focusing evaluation value, an exposure evaluation value and a color evaluation value are calculated 7 by supplying by switching the high-pass component and low-pass component of an image pickup video signal and the low-pass component of a color difference signal by a switch 13, respectively to a single digital integrator 15 while a lens 1 is separated from the focusing position. When the lens 1 approaches the focusing position, the integrator is used for only the generation of the focusing evaluation value by supplying only the high-pass component of the image pickup video signal by fixing the switch 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video camera having an autofocus device for automatically focusing using a picked-up image signal.

[0002]

2. Description of the Related Art In an autofocus device for a video camera, a method of using a picked-up image signal obtained from an image pickup element for evaluation of a focus control state has essentially no parallax and has a shallow depth of field. There are many advantages such as accurate focusing even in case or a distant subject.
Moreover, no special sensor for autofocus is required, and the mechanism is extremely simple.

By the way, in a normal video camera, in addition to the autofocus function, the amount of light incident on the image pickup device is adjusted to an appropriate amount to prevent an extremely dark screen or a bright screen from being projected, and the color of the light source. R depending on temperature
A white balance adjustment function for adjusting the gains of the (red) and B (blue) signals is provided, and a method of evaluating the picked-up video signal is applied to both of these functions in the same manner as the autofocus function.

FIG. 1 is a block diagram of the essential parts of a video camera having these three functions. This conventional technique will be described. The incident light that has passed through the taking lens 1 forms an image on the solid-state image sensor (CCD) 3 through the optical diaphragm mechanism 2, is photoelectrically converted, and is input to the AGC circuit 4 as an image pickup signal. The output of the AGC circuit 4 is , To the video signal processing circuit 5.

As shown in FIG. 2, the video signal processing circuit 5 includes a color separation circuit 5a for processing an image pickup signal into three primary color signals of R, G and B, and an R gain correction signal for the R signal from the color separation circuit 5a. R amplifier 5b that amplifies by the gain set by
Similarly, a B amplifier 5c that amplifies the B signal with a gain set by the B gain correction signal, and a luminance signal Y and a color difference signal using the G signal and the R and B signals that have passed through the R and B amplifiers 5b and 5c as inputs. It is composed of a camera process & matrix circuit 5d for creating RY and BY.

The image pickup signal from the CCD 3 is usually a signal whose level is proportional to the brightness, and the image pickup signal is input to the low pass filter (LPF) 12 and used for evaluating the exposure state for the auto iris.

The image pickup signal is input to a BPF 10 having a cutoff frequency of 200 KHz for extracting a high frequency component and a BPF 11 having a cutoff frequency of 600 KHz higher than the BPF 10, and both BPF outputs are combined for autofocus. It is used to evaluate the focus state.

Further, the color difference signals RY and BY output from the video signal processing circuit 5 are input to LPFs 8 and 9, respectively, and their levels are detected.

The five outputs of the LPFs 8, 9, 12 and the BPFs 10, 11 are fixed contacts 13a, 13 of the switch 13, respectively.
b, 13c, 13d, 13e, and the switch 13 is switched according to a predetermined rule by a switching control signal from a microcomputer 7 described later.

The output of the switch 13 is converted into a digital value by the A / D converter 14 and set to 1 by the digital integrator 15.
The sum of the field periods, that is, digital integration, is input to the microcomputer 7 as each evaluation value.

If the switch 13 is switched to the fixed contact 13a and the LPF8 output is selected, the digital integrator 15 outputs one field of the color difference signal R-Y after the completion of integration for one field period. Similarly, when the switch 13 is switched to the fixed contact 13b and the LPF 9 output is selected with the digital integrated value as the RY color evaluation value, the digital integrator 15 outputs 1 of the color difference signal BY.
The digital integrated value for the field is output as the BY color evaluation value.

Further, when the switch 13 is switched to the fixed contact 13c and the output of the BPF 10 is selected, the digital integrator 15 outputs the first digital integrated value of the high frequency component of 200 KHz or more of the image pickup signal during one field period.
Similarly, as the focus evaluation value, the switch 13 is the fixed contact 13
When switching to d and BPF11 output is selected,
The digital integrator 15 outputs the digital integrated value of the high frequency component of 600 KHz or more of the image pickup signal for one field period as the second focus evaluation value.

When the switch 13 is switched to the fixed contact 13e and the LPF 12 output is selected, the digital integrator 15 outputs the digital integrated value of the image pickup signal for one field period as the exposure evaluation value.

Incidentally, normally, the switch 13 and the A / D converter 1
4 and the digital integrator 15 are integrated in a single standard cell 16.

Reference numeral 16 in FIG. 1 is a focus motor for moving the lens 1 back and forth in the optical axis direction. The drive speed and the rotation direction are controlled in response to a command from the microcomputer 7 instructing the speed and direction, and the drive speed is changed. The change changes the moving speed of the lens, and the change of the rotation direction changes the moving direction of the lens. In addition, information indicating the current lens position is input from the motor 16 to the microcomputer 7. This location information is
It is calculated based on the rotation amount of the focus motor 16 in one direction from the initial position. That is, when the lens starts the focusing operation from the initial position and the motor 16 rotates in the positive direction and the lens rotates in the infinity point direction, the rotation of the motor 16 reaches the initial value corresponding to the initial position. When the amount is added and the lens is rotated in the reverse direction to rotate in the near point direction, the rotation amount of the motor 16 is subtracted.

As described above, the microcomputer 7 executes three different types of operations, which are the white balance adjusting operation, the exposure adjusting operation, and the focusing operation, which are independent of each other, in a time-division manner. The calculation is performed by using a series of circuits from the switch 13 to the digital integrator 15 in time division. That is, as shown in FIG. 3A, the switch is the BPF 10
→ BPF11 → LPF8 → BPF10 → BPF11 → L
3 like PF9 → BPF10 → BPF11 → LPF3
After the BPF 10 and the BPF 11 are selected in the field cycle, one of the three types of LPFs is sequentially selected. In other words, the BPF 10 that creates the first focus evaluation value that is the basis of the hill-climbing focus operation is performed once every three fields.
The BPF 11 that calculates the relative ratio R together with the first focus evaluation value is also once in 3 fields following the BPF 10, and the LPF 8 for white balance adjustment of the RY color difference signal is 1 in 9 fields.
9 times, LPF9 for white balance adjustment of BY color difference signal
Once in the field, the LPF 12 for exposure adjustment is also selected once in 9 fields.

Further, by selection by the switch 13 in one field period, each filter output is digitally integrated over this one field period and processed into an evaluation value,
It is in the next field that each process is actually read by the microcomputer 7 and executed. That is, as shown in FIG. 3B, when the BPF 10 is selected in a certain field (n is an integer and n is the nth field), the reading of the first focus evaluation value by the microcomputer 7 is n + 1. The second focus evaluation value is read by selecting the BPF 11 in the (n + 1) th field and the hill climbing focus operation is n + 2.
Executed in the field, LPF in the n + 2 field
The reading of the RY color evaluation value by the selection of 8 is executed in the (n + 3) th field, and the BPF1 in the (n + 3) th field.
The reading of the first focus evaluation value obtained by selecting 0 by the microcomputer 7 is the n + 4 field, and the reading of the second focus evaluation value by the selection of the BPF 11 in the n + 4 field and the hill climbing focus operation are the n + 5 field. And the B + by the LPF9 selection at the (n + 5) th field.
The white balance adjustment operation, which is the operation of creating the R and B gain adjustment signals at the same time as reading the Y color evaluation value and the latest RY color evaluation value, is executed in the n + 6 field, and is obtained by selecting the BPF 10 in the n + 6 field. The reading of the first focus evaluation value to be performed becomes the (n + 7) th field, and the reading of the second focus evaluation value and the hill-climbing focusing operation by the selection of the BPF 11 at the (n + 7) th field are executed at the (n + 8) th field and the LPF12 at the (n + 8) th field. The reading of the exposure evaluation value and the exposure adjusting operation based on the reading are executed in the (n + 9) th field, and the switching and reading operations are repeated thereafter.

Next, the processing by the microcomputer 7 will be described in more detail. The microcomputer 7 executes the camera processing routine of FIG. 4 for each field. This camera processing routine selectively executes AF processing for focusing operation, AE processing for exposure adjustment operation, and AWB processing for white balance adjustment operation. Specifically, first, In step S1, switching of the switch 13 is executed for each field according to the above-mentioned rule, and in step S2, the digital integrator 15 which is the filter output digital integration value selected by the switch 13 one field before is used as an evaluation value. If the switch 13 is a field next to the field for which the BPF 10 or the BPF 11 is selected, the field is recognized as the AF processing field in step S3, and the AF processing routine of step S4 is performed.

If the switch 13 is the next field after the field in which the LPF 12 is selected, step S4
And jumps to step S5 to the AE processing routine of step S6.

Further, the switch 13 is the LPF 8 or the LP.
If it is the next field of the field that selected F9,
Jump from step S6 to step S7 to step S
The process proceeds to the AWB processing routine of No. 8.

Here, the AF processing routine of step S4 will be further described. The AF processing routine is composed of the flowchart shown in FIG. To explain this flowchart in detail, it is determined that the switch 13 is the field next to the field in which the BPF 10 is selected in step S.
When recognized by 10, the evaluation value input in step S11 is stored in the memory M1 as the first focus evaluation value V1, and the AF processing routine is completed.

If the switch 13 is the field next to the field in which the BPF 11 is selected, step S is executed.
When it is recognized in 10, it is determined that the input evaluation value is the second focus evaluation value V2, and the process proceeds to step S12. Step S12 is a step of confirming the set state of the AF completion flag which is set only when the lens is stopped at the in-focus position after the hill climbing control is completed. The process moves to S13.

Here, the first focus evaluation value V1 and the second focus evaluation value V2 have a cutoff frequency of BPF10 of BPF11.
Since it is set lower than the cutoff frequency of
The PF10 output also includes a relatively lower frequency component than the BPF11 output, and as shown in FIG. 7, the first focus evaluation value V1 has the maximum value at the focus position and is gentle with respect to changes in the lens position. On the other hand, the second focus evaluation value V2 has the maximum value at the in-focus position and is steep with respect to the change of the lens position.

The CL flag is a flag which becomes a clear state when it is recognized that the lens has moved beyond the in-focus position.
Since the set state is set during the normal hill climbing focus operation, the process proceeds to step S14.

In step S14, the input second focus evaluation value V2 is compared with the maximum evaluation value MAX so far, and if it is determined that the latest evaluation value is larger, the lens is released in step S15. The value of the maximum evaluation value MAX is updated with the latest evaluation value, assuming that the mountain is being climbed. Further, the current lens position at the time when the latest evaluation value is input in step S16 is stored in the lens position memory ML.

Next, assuming that the in-focus position exists in the current movement direction, the lens movement direction is maintained as it is in step 17, and it is determined that the hill climbing control should be continued, and the CL flag is set in step S18. Is set, the latest first focus evaluation value V1 stored in the memory M1 is read out in step S19, and the relative ratio R (= V2
/ V1) is calculated.

Then, it is determined in step S20 whether the relative ratio R exceeds the first threshold value RTH, and the relative ratio R
Is above the threshold RTH, the focus motor 16 is driven at a low speed in order to slow down the lens movement in step S21 because the current lens position is approaching the in-focus position, and conversely the relative ratio R is equal to the threshold value. If it is less than RTH, it is determined in step S22 that the current lens position is considerably separated from the in-focus position, and the focus motor 16 is driven at high speed in order to move the lens at high speed.

Now, the control of the lens moving speed by the relative ratio R will be described in more detail.
It is a function value that can express the in-focus state (degree of blurring) of the subject as well as the focus evaluation value. It is a kind of normalized state quantity because it is expressed as a ratio, and the effect of the environment in which the subject is placed. It has the property of being less susceptible to For example, when the illuminance of the subject changes, the absolute value of the focus evaluation value changes, but the relative ratio does not change significantly. Usually, since the above-mentioned property is independent of the type of subject, it is possible to use this relative ratio as a parameter of the degree of blur. The relationship between the degree of blurring and the relative ratio R is illustrated in the monotonically decreasing characteristic curve of FIG.
The relationship between the focus evaluation value V2 and the relative ratio R and the lens position is illustrated in FIG. 9, and as is clear from FIG. 8, the relative ratio R has the in-focus position as the apex and is closer to the near point and the ∞ point side. A characteristic that changes substantially linearly is obtained. Therefore, the first threshold R
As a result of comparison between TH and the relative ratio R, when the first threshold RTH is exceeded, the focus evaluation value changes in the vicinity of the steep focus position, and when it falls below the first threshold RTH, the lens moves to a position away from the focus position where the change is gentle. There will be a position. On the other hand, if the lens is moved as fast as possible, a quick focusing operation is possible, but if the lens is too close to the focus position, too much speed will cause a large amount of overshoot when moving past the focus position. As a result, an unstable focusing operation is executed.

Therefore, as a countermeasure against this, by comparing the relative ratio R with the first threshold value RTH as described above, it is determined whether or not the lens is approaching the in-focus position, and the in-focus position is approached. The moving speed of the lens is slowed only when there is.

By the series of hill climbing focusing operations described above, FIG.
As indicated by the arrow Y1, the lens gradually approaches the in-focus position P while moving in the direction in which the second focus evaluation value increases.

On the other hand, when it is determined in step S14 that the latest focus evaluation value is below the maximum evaluation value MAX,
Threshold width a that can be used to confirm that the focus position has been exceeded too much
As described above, it is determined in step 23 whether or not the second focus evaluation value V2 has dropped, and even a slight drop within the threshold width a may continue due to the influence of noise or the like, so the hill climbing operation is continued and the threshold width a or above is exceeded. If the drop is confirmed, it is determined that the point Q has been reached, and the process proceeds to step 24 to reverse the rotation direction of the motor 16 so as to reverse the lens movement direction,
In step S25, the lens is moved at high speed, and step S
At 26, the flag CL is cleared to indicate that the focus position has been exceeded, and the lens moves in the direction of arrow Y2 in FIG.

Therefore, in the AF process thereafter, the process proceeds from step S13 to step S27, the current lens position is compared with the lens position having the maximum evaluation value stored in the lens position memory ML, and the second It is judged whether or not the lens has returned to the position where the focus evaluation value V2 becomes the maximum evaluation value MAX. If not returned, the lens movement in the arrow direction is continued, and if it is returned, step S28. The driving of the focus motor 16 is stopped to stop the lens 1, and the AF completion flag is set in step S29. As a result, the lens stops at the in-focus position and the in-focus operation is completed. In the AF processing thereafter, a series of hill-climbing in-focus operations is not executed from step S12.

In the AE process executed when the exposure evaluation value is read from the evaluation value obtained by selecting the LPF 12, the exposure evaluation value indicating the brightness level of the entire screen can realize the optimum exposure state. An aperture correction signal is output so as to match the reference value, and the aperture amount of the optical aperture mechanism 2 is adjusted accordingly. Even if the amount of incident light is extremely large and the diaphragm mechanism 2 is in the fully open state, if the reference value still cannot be obtained, the AGC correction signal is input to the AGC circuit 4 and the level of the image pickup signal is input to the AGC circuit 4. Adjust electrically.

Further, in the AWB processing routine, when the evaluation value obtained by selecting the LPF 8 is loaded into the microcomputer 7, only the work of storing the evaluation value in the memory as the RY evaluation value is executed. When the evaluation value obtained by selecting the LPF 9 after three fields is taken into the microcomputer 7, this evaluation value is B-
Recognized as Y evaluation value and the latest RY from memory
The evaluation value is read out, and the R gain correction signal is output to the R amplifier 5b so that the RY evaluation value becomes a preset reference value, and the gain of the R signal is corrected. At the same time, BY
The B gain correction signal is output to the B amplifier 5c so that the evaluation value becomes a preset reference value, and the gain of the B signal is corrected.

[0035]

Normally, white balance adjustment and exposure adjustment can be performed gently over a relatively long time without any particular problem. However, in the case of focusing operation, the lens has a large focusing position. In consideration of problems such as overshooting, it is necessary to process from the calculation of the focus evaluation value to the specific control based on it in a short time. That is, in the above-mentioned conventional technique, the first and second focus evaluation values are obtained once every three fields, and the focusing operation is performed once in three fields based on these values. It can be recognized that the focus position has reached the maximum value and has begun to fall, at a position three fields away from the focus position.

Further, in practice, as shown in FIG.
The image pickup signal created based on the electric charges accumulated in the CD3 is digitally integrated through a predetermined filter in the next field and read into the microcomputer 7 in the next field. Therefore, the focus evaluation read by the microcomputer is performed. The value is 1.
The data is obtained by evaluating the screen shot 5 fields before. Therefore, until the lens reaches the in-focus position and then the drop in the evaluation value is detected and it is possible to recognize that the in-focus position has been reached, a total of 4. Five fields are also required, and during this 4.5 fields, the lens moves beyond the in-focus position, greatly exceeds the allowable width a, and moves away from the in-focus position. What was there will be out of focus again.

In order to solve such a problem, B
An A / D converter and a digital integrator 15 are prepared for the PFs 10 and 11, respectively, and further, an A / D is used for the LPFs 8, 9 and 12.
Prepare one converter and one digital integrator, that is, A /
If D converters and digital integrators for 3 channels are prepared, and the focus evaluation value for each field is calculated and read by the microcomputer one field later, 1.
Even if the delay of 5 fields is taken into account, it becomes a delay of 2.5 fields, and it becomes possible to eliminate the amount of lens overshooting between 2 fields.
Standard having D converter and digital integrator 15
The number of gates of the dosels will increase drastically and the cost will inevitably increase.

[0038]

According to the present invention, there is provided a first BPF for extracting a first high frequency component of an image pickup signal obtained by photoelectrically converting incident light entering through a lens by an image pickup device,
The second BPF having a higher cutoff frequency than the first BPF and extracting the second high frequency component of the image pickup signal, the LPF detecting the level of the image pickup signal, and the outputs of the first BPF, the second BPF and the LPF are selectively selected. The switch means and the output of the switch means are digitally integrated, the integrated value is output as the first focus evaluation value when the first BPF is selected by the switch means, and the integrated value is output when the second BPF is selected. An integrating unit that outputs the two focus evaluation values and outputs the integrated value as the exposure evaluation value when the LPF is selected, and the focus evaluation value of either the first focus evaluation value or the second focus evaluation value is the maximum value. A focus control means for controlling the distance between the image pickup element and the lens so as to obtain a relative ratio calculation means for calculating a ratio of the second focus evaluation value to the first focus evaluation value as a relative ratio. And exposure control means for adjusting the exposure so that the exposure evaluation value becomes a predetermined reference value, and when the relative ratio exceeds a threshold value, the switch means is fixed to one of the first BPF or the second BPF. .

As still another means, a first BPF for extracting a first high frequency component of an image pickup signal obtained by photoelectrically converting incident light entering through a lens by an image pickup element, and a first BPF.
A second BPF that has a higher cutoff frequency than the PF and that extracts a second high-frequency component of the image pickup signal, a first LPF that detects the level of the color difference signal RY in the image pickup signal, and a color difference signal BY in the image pickup signal. A second LPF for detecting the level of
An R signal amplifier that adjusts the gain of the R signal in the imaging signal;
A B signal amplifier for adjusting the gain of the B signal in the image pickup signal,
The switch means for selectively selecting the outputs of the first BPF, the second BPF, the first LPF and the second LPF, and the output of the switch means are digitally integrated, and the switch means outputs the first BPF.
Is output as the first focus evaluation value when is selected, the integration value is output as the second focus evaluation value when the second BPF is selected, and the integration is output when the first LPF is selected. The value is output as the RY color evaluation value and the second L
Integrating means for outputting the integrated value as a BY color evaluation value when PF is selected, and imaging so that the focus evaluation value of either the first focus evaluation value or the second focus evaluation value becomes the maximum value. Focus control means for controlling the distance between the element and the lens, relative ratio calculation means for calculating the ratio of the second focus evaluation value to the first focus evaluation value as a relative ratio, RY color evaluation value and BY color. Gain control means for determining the gain of the R signal amplifier and the gain of the B signal amplifier so that the evaluation value becomes a predetermined reference value is provided, and when the relative ratio exceeds the threshold value, the switch means is set to one of the first BPF and the second BPF. It is characterized by fixing.

[0040]

Since the present invention is configured as described above, after the relative ratio exceeds the threshold value and approaches the in-focus state, either the first or second focus evaluation value which becomes the basis of the focus control for each field. Is always detected, and it becomes possible to minimize the amount of overshoot when the relative position of the lens overshoots the in-focus position.

[0041]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The overall block diagram is the same as that shown in FIG. 1 described in the prior art, and the only difference is the operation of the microcomputer 7.

While the relative ratio R is below the second threshold value B, the microcomputer 7 executes the white balance adjusting operation, the exposure adjusting operation and the focusing operation as in the conventional example. Also at this time,
The switching pattern of the switch 13 is the same as in FIG.

In the AF processing of this embodiment, the state of the flag BS that affects the switching of the switch 13 and the processing of AE and AWB by the microcomputer as in step S30 of FIG. 12 is performed after the series of processing of FIG. It is different from the conventional example in that a control routine is added.

The state control routine of the flag BS is composed of the flow chart shown in FIG. That is, after a series of steps for the mountain climbing focus operation, it is determined in step S31 whether or not the mountain is being climbed, based on the state of the flag CL. If the flag CL is in the set state, the process proceeds to step S32. Then, it is determined whether the relative ratio R calculated in step S19 exceeds the second threshold value RA, and R <
If RA, the lens is located far away from the in-focus position and it is judged that the in-focus position will not be suddenly overshot, and the flag BS is cleared in step S33, and conversely R ≧.
If RA is satisfied, the lens is extremely close to the in-focus position, and the lens may go too far in the in-focus position, and the flag BS is set in step S34.

If it is determined in step 31 that the mountain is not being climbed, only the second focus evaluation value is set to 1 anymore.
The flag BS is cleared in step S35 on the assumption that it is not necessary to take out the focusing operation for each field.

On the other hand, in the camera processing, as shown in FIG. 11, steps 80 to 85 are added to the flowchart of FIG. Here, steps S80, S82, S8
4 and 85 are both steps for judging whether or not the flag BS is in the set state. In other words, whether or not the lens is sufficiently close to the in-focus position during mountain climbing or the mountain climbing operation has already been completed. If the flag BS is not in the set state, that is, if the lens is far from the in-focus position or if the in-focus position has already been detected, the same as in the conventional example shown in FIG. In order, the microcomputer 7 performs AF processing, AE processing, AWB
The processing is sequentially executed.

On the other hand, if the flag BS is in the set state,
In step S81, the switch 13 is fixed to the fixed contact 13d, so that the evaluation value input from the digital integrator to the microcomputer 7 in step S2 is always the integrated value of the BPF 11 output.

Then, step S82 unconditionally moves to step S4 to execute the AF process, and then skips steps S84 to S5 and step S6 to not execute the AE process. Similarly, steps S85 to S7. Also, the AWB process is not executed beyond step S8. In this way, while the flag BS continues to be in the set state, a fine focusing operation is executed based on only the second focus evaluation value obtained for each field from the output of the BPF 11, and the fear of overshooting the in-focus position is avoided. .

Also, during this period, the exposure adjusting operation and the white balance adjusting operation are prohibited, but these two adjusting operations do not require a high response as compared with the in-focus scanning, so that they are very close to the in-focus position. There is no great inconvenience even if it is not executed for a period of time until the lens being moved passes the in-focus position and falls to such an extent that it exceeds the threshold width a.

Further, while the switch 13 is fixed to the fixed contact 13d as described above, the second focus evaluation value V2
However, the first focus evaluation value V1 necessary for calculating the relative ratio R is not updated and only an accurate value is not calculated when calculating the relative ratio R in step S19. As is clear from FIG. 7, the first focus evaluation value V1 has a flat shape near the peak, that is, the focus position, and the relative ratio R changes depending on the second focus evaluation value. It does not matter if the focus evaluation value is not updated.

In the above embodiment, the second focus evaluation value V2 is used as the basis for executing the hill climbing focusing operation.
Alternatively, the first focus evaluation value V1 may be used. In this case, if the flag BS is in the set state, the switch 13 must be set so as to be fixed to the fixed contact 13d at all times. Further, both the first threshold value RTH, which is a criterion for determining whether to move the lens at a high speed, and the second threshold value RA, which is a criterion for determining whether to execute only the AF process, are set to optimum values in advance by experiments or the like. However, there is no particular problem even if the values are the same.

In the above embodiment, the lens 1 is moved back and forth in the optical axis direction by the driving force of the focus motor 16.
Alternatively, the lens 1 may be fixed and the CCD 3 may be moved back and forth in the optical axis direction by a focus motor.
Further, it can be realized by a piezoelectric element instead of the focus motor.

Further, in the above-mentioned embodiment, the image pickup signal obtained from the CCD 3 is used for creating the focus evaluation value or the exposure evaluation value, but it is also possible to use the luminance signal from the video signal processing circuit 5. Needless to say.

[0054]

As described above, according to the present invention, after the relative ratio exceeds the threshold and approaches the in-focus state, any one of the focus evaluation values which is the basis of the focus control is always detected for each field. As a result, it is possible to minimize the amount of overshoot when the relative position of the lens goes beyond the in-focus position, and it is possible to achieve a smooth focus automatic operation without the cost increase associated with the increase of digital integrators. Adjustments can be realized.

[Brief description of drawings]

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

FIG. 2 is a block diagram of an essential part of an embodiment of the present invention.

FIG. 3 is a diagram illustrating a switching rule of a switch 13 and a processing timing in a microcomputer according to an embodiment of the present invention.

FIG. 4 is a flowchart of a camera processing routine of a conventional example of the present invention.

FIG. 5 is a flowchart of an AF processing routine of a conventional example of the present invention.

FIG. 6 shows a lens position and a second position in the hill climbing focusing operation of the present invention.
It is a figure explaining the relationship with a focus evaluation value.

FIG. 7 is a diagram illustrating the relationship between the first and second focus evaluation values and the lens position according to the present invention.

FIG. 8 is a diagram illustrating a relationship between a blur degree and a relative ratio according to the present invention.

FIG. 9 is a diagram illustrating a relationship between a second focus evaluation value and a relative ratio and a lens position of the present invention.

FIG. 10 is a timing explanatory diagram of a conventional example of the present invention.

FIG. 11 is a flowchart of a camera processing routine according to an embodiment of the present invention.

FIG. 12 is a flowchart of an AF processing routine according to an embodiment of the present invention.

FIG. 13 is a flowchart of a flag BS state control processing routine in one embodiment of the present invention.

[Explanation of symbols]

 1 Lens 2 Aperture Mechanism 3 CCD 8 LPF 9 LPF 10 BPF 11 BPF 12 LPF 13 Switch 15 Digital Integrator 7 Microcomputer 16 Focus Motor 5b R Amplifier 5c B Amplifier

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H04N 5/238 G02B 7/11 K 9/73 NG03B 3/00 A

Claims (2)

[Claims] 1. A first BPF for extracting a first high-frequency component of an image pickup signal obtained by photoelectrically converting incident light entering through a lens by an image pickup element, and a cutoff frequency higher than that of the first BPF. A second BPF for extracting the second high frequency component of the image pickup signal, an LPF for detecting the level of the image pickup signal, a switch means for selectively selecting the output of the first BPF, the second BPF and the LPF, and an output of the switch means Is digitally integrated, the integrated value is output as a first focus evaluation value when the first BPF is selected by the switch means, and the integrated value is output as a second focus evaluation value when the second BPF is selected. And an integration unit that outputs an integrated value as an exposure evaluation value when the LPF is selected, and either the first focus evaluation value or the second focus evaluation value. A focus control unit that controls a distance between the image sensor and the lens so that a focus evaluation value becomes a maximum value, and a relative ratio that calculates a ratio of the second focus evaluation value to the first focus evaluation value as a relative ratio. A calculation unit and an exposure control unit that adjusts the exposure so that the exposure evaluation value becomes a predetermined reference value, and when the relative ratio exceeds a threshold value, the switch unit is set to one of the first BPF and the second BPF. An autofocus video camera that is fixed. 2. A first BPF for extracting a first high frequency component of an image pickup signal obtained by photoelectrically converting incident light entering through a lens by an image pickup element, and a cutoff frequency higher than that of the first BPF. A second BPF for extracting the second high-frequency component of the image pickup signal, a first LPF for detecting the level of the color difference signal RY in the image pickup signal, and a second LPF for detecting the level of the color difference signal BY in the image pickup signal. An R signal amplifier that adjusts the gain of the R signal in the image pickup signal, a B signal amplifier that adjusts the gain of the B signal in the image pickup signal, the first BPF, the second BPF, the first LPF, and the second LP
Switch means for selectively selecting the output of F, and digital integration of the output of the switch means, and when the first BPF is selected by the switch means, the integrated value is output as a first focus evaluation value, The integrated value is output as a second focus evaluation value when the second BPF is selected, and the integrated value is R when the first LPF is selected.
Any of the first focus evaluation value or the second focus evaluation value, which outputs as a Y color evaluation value and outputs an integrated value as a BY color evaluation value when the second LPF is selected. And a focus control unit that controls the distance between the image sensor and the lens so that the focus evaluation value becomes maximum, and a ratio of the second focus evaluation value to the first focus evaluation value is calculated as a relative ratio. Relative ratio calculation means, and gain control means for determining the gain of the R signal amplifier and the gain of the B signal amplifier so that the RY color evaluation value and the BY color evaluation value become predetermined reference values, An autofocus video camera, wherein the switch means is fixed to one of the first BPF and the second BPF when the relative ratio exceeds a threshold value.