JPH067668B2 - Mountain climbing type autofocus device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a contrast value from a high frequency component of a video signal in a camera device such as a video camera and detects a peak point of the contrast value to perform a focusing operation. The present invention relates to a focus device, and more particularly to a mountain climbing type autofocus device suitable for a camera device using a front fixed zoom lens as an optical lens for obtaining a video signal.

2. Description of the Related Art Conventionally, a mountain climbing type autofocus device in a video camera or the like having a front lens fixed zoom lens in which a focusing lens is provided on the image side of a variable power lens is shown in a block diagram in FIG. A device having such a configuration is known.

The operation will be briefly described below, but before that, the front lens fixed zoom lens will be described.

As is well known, the front lens fixed zoom lens can make the size of the focusing lens smaller and lighter than the extremely common rear lens fixed zoom lens, and the amount of movement thereof can be reduced. Have a point.

In addition, it has a feature that it is possible to shoot a subject within 1 m, which is usually called macro shooting, depending on the setting of the focal length.

Such a characteristic is also clear from the focusing characteristic diagram showing the relationship between the focusing lens position and the focal length at which the in-focus state can be obtained with the subject distance in the general front fixed zoom lens shown in FIG. 4 as a parameter. Is. That is, as the set focal length becomes closer to the short focus side, the limit distance on the near point side where the in-focus state can be obtained changes to the near distance side due to the movement of the focusing lens. Note that the focusing lens position for an object at infinity in the characteristics shown in FIG. 4 is constant regardless of the focal length, but this is due to an appropriate design including other lenses such as a correction lens. Easy to implement, not to mention in detail.

In addition, points N and F in FIG. 4 indicate the limit positions on the near point side and the far point side, respectively, in terms of the design in which the focusing lens can move.

The operation of the conventional device shown in FIG. 3 will be described below.
Now, when a focusing device for a general desired subject at a distance of 1 m or more is started, a zoom lens L ₁ , a correction lens L ₂ , a focusing lens
The video signal of the desired subject obtained through the front fixed zoom lens 1 composed of L _{3 and the} like is supplied from a camera device 2 such as a video camera to a high-pass circuit 3, and the high-pass circuit 3 outputs a high frequency signal from the video signal. The component is taken out and output to the contrast value detection circuit 4.

The contrast value detection circuit 4 is composed of a detection circuit, a peak hold circuit or the like, and detects the contrast value from the high frequency component and outputs it to the difference circuit 5.

The difference circuit 5 detects an increase / decrease of the supplied contrast value, and indicates the increase / decrease / invariance of the contrast value.
The second and third signals are output and supplied to the motor control circuit 6.

Therefore, the motor control circuit 6 drives the motor 7 which does not start the focusing operation to move the focusing lens L ₃ along the optical axis, and controls the moving direction by the output of the difference circuit 5. become. That is, if the contrast value increases or does not change and the difference circuit 5 outputs the first or third signal, the direction is as it is, and if the contrast value decreases and the second signal is output, the direction is the reverse direction. Therefore, the moving direction of the focusing lens L ₃ is controlled.

Such an operation is performed by changing the contrast value with respect to an arbitrary focusing lens position within the entire moving range indicated by points N and F in FIG. 4 of an object at a distance of 1 m or more having a general contrast at an arbitrary focal length shown in FIG. The description will be as follows with reference to the contrast value characteristic diagram showing the characteristic A.

Now, assuming that the focusing lens L ₃ is located at the point P in FIG. 5, the focusing lens L ₃ first starts moving in the arrow X direction, which is the near point side, by starting the focusing operation described above. If so, the contrast value will decrease, and in this case, therefore, the difference circuit 5 will supply the second signal to the motor control circuit 6, so that the motor control circuit 6 reverses the motor 7 and causes the focusing lens L to rotate. The movement direction of ₃ will be reversed.

That is, by the above operation, the focusing lens L ₃ is moved to the arrow Y in FIG.
In this case, since the contrast value increases as is apparent from FIG. 5, the difference circuit 5 outputs the first signal, and the motor control circuit 6 outputs the motor 7 Will continue to be driven in that direction.

When the focusing lens L ₃ moves in the direction of the arrow Y and passes the point Q where the contrast value reaches the peak, the contrast value decreases again and the motor 7 is rotated in the reverse direction, so that the focusing lens L ₃ moves in the direction of the arrow X again. Will be done.

However, in such a case, the reverse operation is performed beyond the Q point at which the peak point can be obtained, and the Q point is immediately passed again, and as a result, the reverse operation is repeated within a short time.

Here, the motor control circuit 6 detects the repetition of the reverse rotation operation within the above short time, and controls the drive stop of the motor 7 so as to position the focusing lens L ₃ at the point Q, so that the motor 7 stops. For example, at that point, the focusing operation on the desired subject having the contrast value characteristic A ends.

The above is the focusing operation for a general subject, but if the characteristic of the contrast value of the desired subject is the characteristic shown by B in FIG. 5, the following inconvenience occurs. There is a fear.

That is, as in the previous case, if the focusing lens L ₃ is located at point P in the figure and starts moving in the direction of arrow X when the focusing operation starts, the difference circuit 5 does not increase or decrease the contrast value. Since the third signal indicating unchanged is output, it becomes impossible to instruct the motor control circuit 6 to perform reverse rotation.

Therefore, the motor 7 reverses only after the focusing lens L ₃ moves to the N point, which is the designed movement limit on the near point side, and starts to move in the arrow Y direction on the far point side.

As a result, the focusing operation takes a long time and the photographing screen becomes unsightly.

Therefore, in the conventional apparatus shown in FIG. 3, the macro switch shown in FIG. 8 in the drawing, the lens drive range arithmetic circuit shown in 9 and the comparison circuit shown in 10 and the variable magnification lens L shown in 11 and 12 are shown. ₁ The position detecting means of the focusing lens L ₃ was provided.

That is, according to the intention of the photographer, the driving range of the focusing lens L ₃ is divided into a range for performing the above-described macro photography for a subject of less than 1 m and a range for performing normal photography for a subject of 1 m or more by the above-mentioned configuration , It was limited.

More specifically, first, the lens drive range arithmetic circuit 9 uses the output of the variable power lens position detection means 11 to focus the lens L ₃ for a subject of, for example, 1 m at the current variable lens position.
4 is calculated from the characteristics shown in FIG. 4, and the driving range of the focusing lens L ₃ is set to the limit position on the near point side from the calculation position when the macro switch 8 is turned on by turning on and off the macro switch 8. Further, when the micro switch 8 is off, the calculation position is set to the limit position on the far point side.

The comparison circuit 10 compares the output of the focusing lens position detection means 12 with the limit positions at both ends that define the drive range set by the arithmetic circuit 9, and the current position of the focusing lens L ₃ is the limit position. When either one of them is reached, a reverse rotation instruction signal for rotating the motor 7 in reverse is supplied to the motor control circuit 6.

As a result, the focusing lens L ₃ is controlled in operation so as not to move out of the drive range set by the arithmetic circuit 9.

Therefore, when corresponding to the example of the subject described in FIG. 5, the focusing lens position for the subject of, for example, 1 m shown by R in the figure is set as one drive limit, and
On the other hand, the subject having the drive limit of the characteristic A or B is clearly 1 m or more as described above, and the macro switch 8 is turned off, so that the subject is determined as the point F.

For this reason, the focusing lens L ₃ is applied to the subject for which the characteristic B is obtained.
Starts moving in the direction of arrow X from point P, the difference circuit 5 outputs the third signal, and even if the reverse rotation instruction cannot be given, the focusing lens
L ₃ is reversed by reaching R point without reaching N point, and moves in the direction of arrow Y.

Therefore, the focusing operation becomes shorter than in the previous case, and the photographing screen smoothly shifts to the focused state.

Problems to be Solved by the Invention However, in the above-described conventional device, since it is necessary to operate the macro switch 8 based on the will of the photographer, for example, the range from outside the range in which the subject is macro-shot. In the case of approaching inside, the problem that the operation of the macro switch 8 is required during the shooting and it becomes difficult to operate at an appropriate timing, or the operation of the macro switch 8 is forgotten, and it is shown in FIG. 5B. As described above, there is a problem that a focusing operation is not performed for a long time on a subject having a low contrast, or the above-described in-focus state when the subject is moved cannot be obtained.

The present invention has been made in consideration of the above problems, and provides a mountain climbing type autofocus device that automatically switches the driving range of the focusing lens L ₃ described above according to the characteristics of the contrast value. It is a thing.

Means for Solving Problems A mountain climbing type autofocus device according to the present invention includes a contrast value detecting device for detecting a contrast value from a high frequency component extracted from a video signal output from a camera device, and an increase / decrease in the contrast value. A differential circuit that outputs first, second, and third signals that indicate increase, decrease, and invariance,
A motor for moving the focusing lens in the optical axis direction, and a driving state of this motor are directly received by the first and third signals.
A motor control circuit for controlling the driving in the same direction or the second signal to drive in the opposite direction, and a variable control circuit for detecting a variable lens position of a lens mounted on the camera device and outputting a variable lens position signal. Double lens position detecting means,
Macro area calculation means for calculating and outputting focus lens position information, which is a macro photography area in consideration of the characteristics of the lens, in response to the variable magnification lens position signal, and a focus lens position for detecting the focus lens position of the lens. A comparison is made between focusing lens position detecting means for outputting a signal and the focusing lens position information and the focusing lens position signal to determine whether or not the current position of the focusing lens is in the macro photographing area. Means and the inrush of the focusing lens from the outside to the inside of the macro photographing area is detected by the output of the comparing means, and the output signal of the difference circuit at the time of detecting the inrush from the outside to the inside is the third signal. Only in some cases, the focusing lens reaches the limit position on the far point side by the output of the signal outputting means for outputting the fourth signal for rotating the motor to the motor control circuit and the output of the focusing lens position detecting means. Whether or not it is detected, and the detection content is stored until a focused state is obtained, and a prohibition means for prohibiting the operation of the signal output means when there is a memory that the focusing lens has reached the far-point side limit position. It is configured with.

The mountain climbing type auto-focusing device according to the present invention has the above-mentioned configuration, and is 1 m long without providing a macro switch which requires manual operation unlike the conventional device described at the beginning.
The conditions under which the focusing lens can enter the macro shooting area within are when the first signal is output, which indicates when the contrast value is increasing, and when the peak point of the contrast value cannot be detected in all areas outside the macro shooting area. Therefore, the focusing lens does not move to the macro photographing area in the case of a subject having a low contrast and a distance of 1 m or more.

On the other hand, the focusing operation can be performed from the macro shooting area to the far point side limit, that is, in the entire moving range of the focusing lens without performing any operation on a general subject that does not output the third signal with high contrast. It will be.

Embodiment 1 FIG. 1 is a block diagram showing the configuration of an embodiment of a mountain climbing type autofocus device according to the present invention, and a third embodiment
The same reference numerals as those in the figure indicate the same functional blocks.

In FIG. 1, reference numeral 13 is a variable magnification lens position signal, which is focal length information supplied from the variable magnification lens position detection means 11 for detecting the position of the variable magnification lens L ₁ , and the characteristics of the front fixed zoom lens 1. Then, a macro area calculating means for calculating a focus lens position, which is a macro shooting area, for example, an area for shooting a subject of less than 1 m at the focal length indicated by the variable power lens position signal, and outputs it as focus lens position information. Shows.

A focusing lens position signal 14 from the focusing lens position detecting means 12 for detecting the position of the focusing lens L ₃ and focusing lens position information from the macro area calculating means 13 are supplied to compare the focusing lens L ₃ with each other. The comparison means is for determining whether or not the current position of the focusing lens L ₃ is within the macro photographing area, and for outputting a determination signal indicating that the focus lens L ₃ is located in each area.

Reference numeral 15 detects that the focusing lens L ₃ has entered from the outside to the inside of the macro area due to the change of the discrimination signal, and if the difference circuit 5 at the time of detection outputs the third signal, the motor control circuit 6 receives the motor signal. Signal output means 16 for outputting a fourth signal for reversing 7 indicates whether or not the focusing lens L ₃ has reached the movement limit position on the far point side by the output of the focusing lens position detection means 12. The operation of the signal output unit is prohibited when there is a memory indicating that the focus lens L ₃ has reached the movement limit position on the far point side, while storing the detection content until the focus state is detected. It indicates a prohibition measure.

The operation of the mountain climbing autofocus device according to the present invention having the above structure will be described below.

As is clear from FIG. 1, the drawing numbers 1 to 7, 1
1,12 Each configuration shown is is a conventional device of the same construction previously described, thus the present invention apparatus is also basic movement control operation of the focusing lens L _3, i.e. subjected to the movement of the focusing lens L ₃ If the output of the differential circuit 5 is the first and third signals, the second
In the case of a signal, the operation of controlling to move in the opposite direction is the same as that of the conventional apparatus, and the description thereof is omitted. The operation different from that of the conventional apparatus will be described below.

As is apparent from FIG. 1, the mountain climbing type autofocus device according to the present invention includes a macro area calculating means 13 and the like.

Therefore, when the focusing operation is started, the macro area calculation means 13 receives the variable-magnification lens position signal, calculates the focusing lens position that is a macro photographing area of less than 1 m at the current variable-magnification lens position, and focuses. Comparing means 14 as lens position information
Output to.

The comparing means 14 compares the focusing lens position information with the focusing lens position signal from the focusing lens position detecting means 12,
The current position of the focusing lens L ₃ is discriminated, that is, it is discriminated whether or not it is within the macro photographing region, and a discrimination signal indicating that it is inside or outside the region is outputted and supplied to the signal output means 15.

On the other hand, the output signal of the difference circuit 5 is also supplied to the signal output means 15, and therefore the signal output means 15 uses the discrimination signal and the output signal from the difference circuit 5 to focus the lens L _3.
Will detect the moving state of.

Therefore, if the output signal of the difference circuit 5 is the third signal when the focusing lens L ₃ rushes in from the outside of the macro photography area due to the change of the discrimination signal, the signal output means 15 reverses the motor 7. An attempt is made to output to the motor control circuit 6 a fourth signal which makes the moving direction of the focusing lens L ₃ the opposite direction.

That is, if there is no memory in the prohibiting means 16 that the focusing lens L ₃ has reached the limit position on the far point side, the signal output means 15 will output the above-mentioned fourth signal.

If the prohibiting means 16 has a memory that the far point side has been reached or not, the same operation as that of the above-described conventional apparatus is performed if the above conditions are not satisfied. That is, the signal output means 15 does not operate and the fourth signal is not output.

Further, the operation of the prohibiting means 16 is that the focusing lens L ₃ once enters the far-side limit point and then enters the macro photography area, which means that the peak point of the contrast value exists outside the macro photography area. In other words, it means that there is a high possibility that the peak value of the contrast value exists in the macro photographing area. In such a case, the fourth signal is not preferable rather than unnecessary and therefore the signal output means 1
The operation of No. 5 is prohibited. Further, it goes without saying that the stored contents of the prohibiting means 16 are reset once the in-focus state is obtained.

This operation is performed in addition to the operation similar to that of the conventional apparatus. In order to make the above-described operation of the mountain climbing type autofocus apparatus of the present invention clearer, the contrast as shown in FIG. Consider the case of a subject having a value characteristic A or B.

First, with respect to the subject having the characteristic A, in the case of the characteristic A, the signal output from the difference circuit 5 is limited to the first and second signals indicating the maximum or decrease of the contrast value. The signal output means 15 does not operate, and the focusing lens L ₃ is moved to the focusing position by the operation control of the motor control circuit 6 by the first and second signals similar to the conventional device.

Next, considering a subject having the characteristic B, the difference circuit 5 outputs the first, second, and third signals in accordance with the movement of the focusing lens L ₃ .

Therefore, the focusing lens L ₃ unconditionally performs the same operation as the conventional device when the first and second signals are output,
When the third signal is output, basically the same operation as the conventional device is performed, but the signal output means 15 described above is used.
Then, there may occur a case where an operation different from that of the conventional apparatus based on the operation of the prohibiting means 16 and the like is performed.

Now, assuming that the focusing lens L ₃ is located at the point P in FIG. 5 and starts moving to the N point side following the start of the focusing operation, the differential circuit 5 outputs the third signal, and Motor control circuit 6
Means that the motor 7 is rotated as it is, and the movement of the focusing lens L ₃ toward the N point side is continued.

However, when the focusing lens L ₃ exceeds the limit position of the macro photography area set by the macro area calculation means 13, for example, the point R, the discrimination signal output by the comparison means 14 changes, and the signal output means 15 changes this. When the entry of the focusing lens L _{3 into} the macro photography area is detected by the change in the determination signal,
The prohibiting means 16 does not remember that the focusing lens L ₃ has reached the far point side limit point because it is a movement from the point P to the point R.
Further, since the third signal is supplied from the difference circuit 5, the signal output means 15 operates and outputs the fourth signal for reversing the motor to the motor control circuit 6.

As a result, unlike the conventional apparatus, the focusing lens L ₃ is automatically moved to the point F side in the opposite direction when the moving direction is not provided with the macro switch 8 or the like, unlike the conventional apparatus. It will be controlled by.

On the other hand, in the case of a subject whose contrast value characteristic is, for example, the one shown by the broken line in FIG. 5, the peak point of the contrast value cannot be obtained outside the macro photography area. It is conceivable that the focusing lens L ₃ once again reaches the far-side limit point F and then crosses the point R. However, in such a case, the prohibiting unit 16 causes the signal output means 15 to operate. Since the operation is prohibited, the motor 7 does not reversely rotate, and the focusing lens L ₃ plunges into the macro photographing area. still,
The focusing operation in such a case is a focusing operation for a long time, but if the subject in the macro shooting area is photographed less frequently, the subject having the characteristics shown by the broken line in FIG. Needless to say, it can be considered that it is not a big problem in practical use because it becomes a very special part or condition such as a palm or a toe and the condition is less frequent.

The operation of the mountain climbing type autofocus device according to the present invention has been described above, but it goes without saying that the motor control circuit 6 and the signal output means 15 in FIG. An example of the operation when the circuit 6, the signal output means 15 and the like are configured by a microcomputer will be briefly described with reference to the flowchart shown in FIG.

When the focusing operation is started, first, step 200 is selected and driving of the motor 7 in an arbitrary direction, for example, a direction for moving the focusing lens L ₃ to the near point side as described above is started.

Next, step 201 is selected, and it is confirmed whether or not the contrast value is increased by the movement of the focusing lens L ₃ by the driving of the motor 7, and if the contrast value is increased, step 208 is selected.

If the contrast value has not increased, then step 20 is performed.
2 is selected, and it is confirmed whether or not the contrast value is decreasing this time. If the contrast value is decreasing, step 204 is selected and the driving direction of the motor 7 driven in the previous step 200 is reversed.

If the contrast value has not decreased, the contrast value remains unchanged, so step 203 is selected, and in this step 203, the data of the macro shooting area is set.

Upon completion of step 203, step 205 is selected, and the focusing lens L ₃ is moved from outside the macro photography area by confirming the discrimination signal of the comparison means 14 for comparing the data set in step 203 with the focusing lens position signal. It is confirmed whether or not it has entered.

If the confirmation result in the above step 205 is NO, that is, if the focusing lens L ₃ has not entered the macro shooting area, step 208 described below will be executed, and if YES is confirmed, the step described below will be executed if it is confirmed that the focus lens L ₃ has entered the macro shooting area. 206
Is selected.

Step 206 is a step of confirming the stored contents of the storage unit that stores whether or not the focusing lens L ₃ has reached the far point side limit during the operation of each step described above, and if not reached, step 207 However, if it has arrived, step 208 will be selected.

Step 207 is a step that is selected when the contrast value is unchanged and the focusing lens L ₃ rushes in from outside the macro photography area and has not reached the far point side limit point by the above steps, As is clear from the above description, this is the step of outputting the fourth signal and reversing the driving direction of the motor 7.

Further, step 208 is selected when it is confirmed in step 201 that the contrast value is increased. That is, this step is selected when the reverse rotation of the motor 7 is not required, and is the step for performing the operation of detecting the peak point of the contrast value necessary for stopping the focusing lens L ₃ at the focus position.

Although the peak point detection operation has been described above, it goes without saying that it is an operation for confirming whether or not the reverse rotation operation of the motor 7 has occurred within a short time.

When the peak point detecting operation is started in step 208, it is then confirmed in step 209 whether or not the above detecting operation is completed, that is, it is confirmed whether or not the peak point is obtained, and the peak point is detected. If the peak point detection operation is completed by the above, step 210 is selected and the motor 7
Is stopped, and the stored content indicating whether or not the focusing lens L ₃ reached the far point side limit point confirmed in step 206 is reset.

On the other hand, if the peak point is not obtained and the peak point detection operation is not completed, the flowchart selects step 201 again,
After that, the operation of each step as described above is performed again.

Needless to say, a series of focusing operations are ended by selecting step 210 and stopping the driving of the motor 7.

The mountain climbing type autofocus device according to the present invention sets the macro photographing area according to the position of the zoom lens, that is, the focal length, and contrasts the rush of the focusing lens from the outside to the inside by the signal output means. When the value does not change and the far point side limit point is not reached, it is controlled so that it can not be performed, so there is no need for a macro switch that requires manual operation, and for objects outside the macro shooting area with a small contrast value This has the effect of limiting the range of movement of the focusing lens.

Further, with respect to a subject having a high contrast, which outputs a signal indicating an increase / decrease in the contrast value, the above-mentioned region is not regulated, so that the focusing lens can move over the entire moving range. That is, there is an effect that the focusing operation can be performed in the entire movement range without performing the manual operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a mountain climbing type autofocus device according to the present invention, and FIG. 2 is an example of an operation when the motor control circuit 6 and the like in FIG. 1 are constructed by a microcomputer. It is a flow chart shown. FIG. 3 is a block diagram showing an example of the configuration of a conventionally known mountain climbing type autofocus device, and FIG.
FIG. 5 is a focusing characteristic diagram showing the relationship between the focusing lens position and the focal length at which the in-focus state is obtained with the subject distance in a general front fixed zoom lens as a parameter. FIG. 5 is the focusing lens position at an arbitrary focal length. 3 is a contrast value characteristic diagram of a subject at a distance of 1 m or more and a subject at a distance of 1 m or less with a large contrast. 1 ... front fixed zoom lens, 2 ... camera device, 3 ...
... High-pass circuit, 4 ... Contrast value detection circuit, 5 ...
… Differential circuit, 6 …… Motor control circuit, 7 …… Motor, 1
1 ... Variable-magnification lens position detection means, 12 ... Focusing lens position detection means, 13 ... Macro area calculation means, 14 ... Comparison means, 15 ... Signal output means, 16 ... Inhibition means.

Claims (1)

[Claims] 1. A contrast value detecting means for detecting a contrast value from a high frequency component extracted from a video signal output from a camera device, and an increase / decrease of the contrast value,
A differential circuit that outputs first, second, and third signals indicating increase, decrease, and invariance, a motor that moves a focusing lens of a lens mounted on the camera device in the optical axis direction, and the first and first A motor control circuit for receiving the three signals, driving the motor as it is, driving the motor in the reverse direction, and detecting the repetition of the reverse rotation operation of the motor within a short time to stop the driving of the motor. A variable-magnification lens position detecting means for detecting the variable-magnification lens position of the lens and outputting a variable-magnification lens position signal, and a focusing function which receives the variable-magnification lens position signal and becomes a macro photography area in consideration of the characteristics of the lens. Macro area calculating means for calculating and outputting lens position information, focusing lens position detecting means for detecting the focusing lens position and outputting a focusing lens position signal, and the focusing lens position Comparing means for comparing the information and the focusing lens position signal to determine whether or not the focusing lens is within the macro photographing area, and outputting a determination signal indicating that the focusing lens is located inside or outside the area, A fourth signal for detecting the entry of the focusing lens from the outside to the inside of the macro photographing area by the determination signal and for reversing the motor only when the output signal of the difference circuit is the third signal at the time of detection. A signal output means for outputting to the motor control circuit and whether or not the focusing lens has reached a far point side limit position from the focusing lens position signal, and the detection content is displayed until a focusing state is obtained. A mountain climbing type autofocus device comprising: a storing means and a prohibiting means for prohibiting the operation of the signal output means when there is a memory that the focusing lens has reached the limit position.