JP2648046B2 - Auto focus camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus control apparatus using an inner lens which has a zooming function and whose image forming position changes according to the focal length.

[0002]

2. Description of the Related Art A so-called inner focus system, which has a zooming function and changes an image forming position in accordance with a focal length, and keeps the image forming position constant during a zoom operation, is disclosed in
It is also disclosed in Japanese Patent Application Laid-Open No. 2-15226 (G02B7 / 04), and is recently being awarded for its advantage that the focusing operation can be speeded up. In the inner method, since the image forming position changes in accordance with the focal length, the focus lens that has once reached the in-focus position needs to be position-corrected in conjunction with the telephoto to wide-angle zooming operation. The amount is a numerical value that is predetermined according to the distance between the camera and the subject (subject distance) and the zoom position, as in a zoom correction curve in FIG.

[0003]

The zoom correction curve indicates the in-focus state for each distance to the subject (subject distance) when the vertical axis indicates the zoom magnification (zoom position) and the horizontal axis indicates the focus lens position. The relationship between the zoom position and the focus lens position for maintaining is shown. When focusing is performed near the telephoto end in a lens system having zoom correction characteristics as shown in this figure, the distance to the subject can be easily calculated from the zoom position and the focus lens position immediately after the focusing operation. In such a case, since the curves of the distances to the respective objects are dense, very high accuracy is required for the focus lens position detection, and it is difficult to detect with the accuracy of a sensor used in general consumer equipment. Therefore, there is a high possibility that out-of-focus occurs when zooming in the telephoto direction after focusing near the wide-angle end.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a lens system having a function of changing magnification and having an image forming position which varies in accordance with a focal length. Means, a first detection means for detecting the position of the zoom lens group, a focus control means for controlling the position of the focus lens group, a second detection means for detecting the position of the focus lens group, and the focus control means. Zoom focus means for performing a zoom focus operation of displacing the focus lens group to a lens position determined by the object distance and the first detection means output, the output of the second detection means immediately after the focus state is reached; A wide-angle end determining means for detecting whether or not the zoom position by the zoom lens group is near the wide-angle end, and when the zoom position is near the wide-angle end, Lens position determining means for determining in which of the plurality of lens ranges the focus lens group is located, wherein a specific subject distance set according to the lens range is set as a subject distance used for zoom focus operation. It is characterized by adoption.

[0005]

Since the present invention is constructed as described above, if the approximate subject distance is known, the selection of the lens correction curve for the zoom focus operation can be set without a large error even near the wide-angle end.

[0006]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 denotes an inner focus type lens unit, which includes a zoom lens 10 having a zooming function for changing a focal length and a rear lens (hereinafter, referred to as a focus lens 11) for focusing an object image on an image sensor. It is composed of Here, the zoom lens 10 advances and retreats in the optical axis direction by a driving force of the zoom motor 2 via a mechanism (not shown), and the focus lens 11 also moves by the driving force of the focus motor 4 via a mechanism (not shown). Move back and forth in the direction. Reference numeral 3 denotes a zoom encoder for detecting the lens position of the zoom lens 10 in the optical axis direction. Reference numeral 5 denotes a pulse generator that generates a pulse in accordance with the amount of movement of the focus lens 11. It is configured to detect a rotation state and emit a predetermined number of pulses for one rotation of the motor. 6 is focus lens 1
This is a position detection switch for detecting a position for detecting the first reference position, and is also used as an end point switch indicating the movable limit of the focus lens 11. The position of the focus lens 11 is detected by counting the number of output pulses of the pulse generator 5 by the counter 12, and when the focus lens 11 reaches a predetermined position (for example, the point at infinity), the position detection switch is turned on and the counter is turned on. 12 is reset. In addition, counter 1
2 is that when the motor is rotating so that the lens 11 moves toward the near point, the output from the pulse generator 5 is counted up, and conversely, the motor rotates so as to move toward the point at infinity. If so, count down.

The subject image formed on the image pickup device is photoelectrically converted by the image pickup circuit 7 to become a picked-up image signal, and the luminance signal of this image signal is supplied to the focus control circuit 8 shown in FIG. The result of the focus control by the focus control circuit 8 is output to the motor control circuit 9, and the motor control circuit 9 controls the driving of the zoom and focus motors 2, 4.

The luminance signal supplied to the focus control circuit 8 is
Only the luminance signal in the focus area set at the center of the imaging screen is extracted in a time-division manner by the area extraction circuit 21 and output to the two subsequent HPFs 22 and 23. Here, the area extracting circuit 21 extracts the vertical and horizontal synchronizing signals in the luminance signal by a synchronizing separation circuit, and uses these synchronizing signals and a fixed oscillator output to open the focus area. This is realized by controlling the opening and closing of a gate circuit which receives a luminance signal as input.

The cutoff frequencies of the HPFs 22 and 23 are different from each other. Specifically, the cutoff of the HPF 22 is 600 KHz, and the cutoff of the HPF 23 is 200 KHz.
Is set to From the luminance signal output from the area extraction circuit 21, only high-frequency components thereof are extracted through HPFs 22 and 23.
In step 5, digital integration is performed for the corresponding field for each field. In this way, the integrated value V1 of the high-frequency component having a relatively higher frequency (600 KHZ or more) is output from the digital integration circuit 24, while the high-frequency component (200KHZ or more) including the frequency component lower than the integration value V1 is output from the digital integration circuit 25. The integrated value V2 of the component is output. Note that the relationship between the focus lens position and each of the integral values V1 and V2 is as shown in FIG.

The integral value V1 is stored in an initial value and maximum value memory 3.
1, 30, the position memory 35, and the hill-climbing focusing operation performed by the first to third comparators are used as focus evaluation values. This hill-climbing focusing operation is performed in a direction discriminating mode (MO) that determines the moving direction of the focus lens 11 immediately after the operation starts.
DE = 1), a hill-climbing mode in which the lens is displaced so that the focus evaluation value becomes large (MODE = 2), and a focus return mode (MODE = 3) in which the lens once returns to the focus position after passing through the focus position. Mode.

Next, the focusing operation will be described with reference to FIG. In the direction determination mode executed immediately after the start of the focusing operation, the focus evaluation value obtained first is held in the maximum value memory 30 and the initial value memory 31. Thereafter, the motor control circuit 9 causes the focus motor 4 to rotate in a predetermined direction (for example, a near point direction), and accordingly, the lens 1
1 is displaced in the optical axis direction, and the output of the second comparator 33 is monitored. The second comparator 33 compares the focus evaluation value obtained after driving the focus motor with the initial evaluation value stored in the initial value memory 31, and outputs the magnitude of the comparison.

The motor control circuit 9 rotates the focus motor 4 in the first direction until the output of the second comparator 33 is large or small, and the output that the latest evaluation value is larger than the initial evaluation value is output. Is performed, the rotation direction is held as it is, and if the latest evaluation value is smaller than the initial evaluation value, the rotation direction of the focus motor 4 is reversed, and then the hill-climbing mode is entered. 1 The output of the comparator 32 is monitored.

The first comparator 32 compares the maximum evaluation value so far held in the maximum value memory 30 with the latest evaluation value, and the latest evaluation value is larger than the contents of the maximum value memory 30 ( Two comparison signals of S1) or sufficiently small (S2) are output. Here, the maximum value memory 30 updates the value based on the output S1 of the first comparator 32 when the latest evaluation value is larger than the content of the maximum value memory 30, and always keeps the maximum value of the evaluation value up to the present. Will be retained.

Reference numeral 35 denotes a position memory for storing the count value of the counter 12 as the position of the lens 11, similarly to the maximum value memory 30, when the maximum evaluation value is obtained based on the output S 1 of the first comparator 32. Updated to keep the lens position at all times.

The motor control circuit 9 monitors the output of the first comparator 32 while rotating the focus motor 4 in the direction determined based on the output of the second comparator 33, and prevents malfunction due to noise in the evaluation value. Therefore, when an output S2 indicating that the latest evaluation value is sufficiently smaller than the maximum evaluation value by the threshold width L or more is output from the output of the first comparator 32, the focusing mode is restored and the focus motor 4 is simultaneously rotated in reverse. .
After this reverse rotation, the contents of the position memory 35 and the count value of the counter 12 indicating the current lens position are compared in the third comparator 36, and when they match, that is, when the lens 11 reaches the position where the focus evaluation value becomes the maximum. When returning, the motor control circuit 9 operates so as to stop the focus motor 4. At the same time, the motor control circuit 9 outputs a hill-climbing completion signal LS. Thus, a series of focusing operations is completed.

When the focus lens reaches the in-focus position by a series of hill-climbing focusing operations, the first memory 42 and the fourth comparator 44 continuously execute a fine adjustment operation. The fine adjustment operation will be described in detail. When the hill-climbing focusing operation is completed, a hill-climbing completion signal is issued and the first memory 42
After the focus evaluation value of the peak of the mountain is stored, the amount of displacement of the focus lens 11 per field during the hill-climbing focusing operation is significantly smaller than the displacement amount of the focus lens 11 per field, and a very small amount of no change in focus on the imaging screen is recognized. The focus motor 4 is driven so that the lens is displaced in a predetermined direction, for example, in the direction of the point at infinity as one unit, and the focus evaluation value obtained first and the value held in the first memory 42 are compared. If the value is smaller, it is displaced by 2 units in the reverse direction, that is, in the direction of the near point, and the latest focus evaluation value obtained in the next field is compared with the contents of the first memory 42. If it is smaller, it is determined that the contents held in the first memory maintain the maximum value, and as shown in FIG.
The lens is displaced by a unit to confirm that the lens position is at the peak of the mountain, and the lens is stopped for a predetermined period.

When it is determined that the lens position is not at the peak of the peak at the time of checking the peak, fine adjustment is performed. That is, as shown in FIG. 7, if the focus evaluation value at the start of the minute displacement is slightly deviated from the peak of the mountain toward the near point, when the unit is displaced by one unit in the far point direction, the latest focus evaluation value becomes better. At this time, a large situation occurs. At this time, the contents of the first memory 42 are updated with the latest focus evaluation value, and the vertex is confirmed again from this position as the vertex of the mountain whose position is to be confirmed. FIG.
In the example of the above, as a result, the lens is finely adjusted to the peak of the mountain by displacing it by two units in the direction of the far point and rechecking the vertex twice. This fine adjustment is effective when the lens position is slightly deviated from the in-focus position, but if the deviation is large, it takes time to reach the in-focus state. It is preferable to respond quickly. For example, if the focus evaluation value at the start of the minute displacement is significantly shifted toward the infinity point from the peak of the mountain, the lens position is moved by one unit in the infinity point direction as shown in FIG. When the unit is moved by a unit, the evaluation value after the movement becomes larger than the evaluation value before the start of the movement.
The contents of the memory 42 are updated, moved one unit further in the direction of the near point, compared, and the update is repeated. It takes a considerable time to reach the vertex. Therefore, in order to cope with this, as shown in FIG.
If the peak is not reached even after the unit movement, the fine adjustment operation is stopped and the hill-climbing focusing operation is restarted. In this case,
“6”, which is a threshold value for determining whether or not to restart the focusing operation, is referred to as a preset allowable step number M.

After the above-described series of hill-climbing focusing operations is completed,
In parallel with the execution of the fine adjustment operation, the in-focus subject moves or changes, and becomes out of focus, and it is determined whether or not it is necessary to perform the focusing operation again by using a relative ratio described later. The relative monitoring circuit 41, the second memory 43, and the fifth comparator 45 execute the subject monitoring operation for monitoring.

The subject monitoring operation will be described in detail.
First, each time the integration values V1 and V2 are generated by the integration circuits 24 and 25, the relative ratio calculation circuit 41 calculates the ratio of the two to the relative ratio R.
Output as A graph showing the relationship between the relative ratio (V1 / V2) and the degree of blurring of the subject (the amount of movement or deviation from the lens position during focusing) results in a monotonously decreasing characteristic curve as shown in FIG.

The state quantity, which is the relative ratio, is a function value that can express the in-focus state (degree of blur) of the subject in the same manner as the focus evaluation value, and is expressed as a ratio. It is a state quantity that is not easily affected by the environment in which the subject is placed. 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 properties are not limited to the type of the subject, this relative ratio can be used as a parameter of the degree of blur.

As described above, since the relative ratio is a state quantity representing the degree of blur, the change in the subject can be determined by monitoring the change in the relative ratio. Therefore, the relative ratio R output from the relative ratio calculation circuit 41 for each field is held as the reference relative ratio RMAX in the second memory 43 when the timing signal TS output from the motor control circuit 9 is output. The obtained relative ratio is compared with the content held in the second memory 43 by the fifth comparator 45. In this comparison, the latest relative ratio is ± 50% of the reference relative ratio.
, That is, when the difference between the latest relative ratio and the reference relative ratio is １ ／ or more of the reference relative ratio, it is determined that the subject has moved, and a restart command signal is output to the motor control circuit. Upon receiving this command signal, the motor control circuit 9 restarts the focusing operation immediately. Note that the above-described fine adjustment operation and the focus resumption determination when the allowable step number M accompanying the operation is exceeded, and further, the subject monitoring operation are all performed in the subject monitoring mode.
An autofocus operation is configured in the above four modes.

Reference numeral 37 denotes an AF / MF selection switch for selecting whether the operator performs the focusing operation automatically or manually. If an automatic (AF) mode is selected, the above-described hill-climbing focusing operation is executed. Later, the subject monitoring mode (MODE =
4) The auto focus operation is performed, and manual (M
F) If the mode is selected, it is possible to manually move the focus lens 11 forward and backward.

Next, the autofocus operation executed by the focusing control circuit 8 and the motor control circuit 9 will be described with reference to the flowchart shown in FIG. First, the focus evaluation value V1 and the relative ratio R of the corresponding field are derived from the digital integrators 24 and 25 and the relative ratio calculation circuit 41 (step 100). Next, a SW processing subroutine is executed (step 150). This subroutine will be described with reference to the flowchart of FIG. Specifically, the AF mode is set to M or M by the AF / MF switch 37.
It is determined which of the F modes is selected (step 300), and if the mode is the MF mode, the fact that the mode is the MF mode is displayed on the viewfinder (step 30).
1) Reset the AZ flag described later (step 30)
2) Prepare for execution of the MF mode with MODE = 5 (step 303). On the other hand, if the AF mode has been selected, the fact that the current mode is the AF mode is displayed on the viewfinder (step 304), the zoom operation is performed, and the lens position correction unique to the inner focus method (described later), that is, It is determined whether or not the AZ flag that is set when it is necessary to execute the zoom focus is set, that is, whether or not it is necessary to execute the lens position correction operation accompanying the zoom operation (step 305). If the correction operation needs to be performed, the subroutine ends without any processing, and if it is reset and the correction operation does not need to be performed, the FS flag is reset. The FS flag indicates a subject distance (or a zoom position and a focus lens position for knowing the subject distance) for maintaining a focused state during zoom focus.
Is set when is stored or set, and thereafter, the determined subject distance is not updated. In the case of the MF mode, MODE = 1 is set and the hill-climbing focusing operation is restarted from the beginning.

When the SW processing subroutine is completed in this way, the process returns to the main routine of FIG. 9 again to determine whether or not the AZ flag is set (step 101). A determination is made (step 104), and if it is not set, it is determined whether the mode is an autofocus mode (AF mode) or a manual mode (MF mode) (step 102). Here, the operator can determine which mode the AF / MF
The changeover switch 37 is operated to select manually. If it is determined that the mode is the MF mode, the operator further operates the manual focus switch (MF switch) 38.
Is operated to apply a predetermined voltage to the focus motor 4 to determine whether or not the focus lens 11 is being moved to a desired position (step 103).
When it is determined that is not being operated, the operator operates the zoom switch 39 to drive the zoom motor 2 and determine whether or not the zoom operation is being performed. Incidentally, whether the AZ flag has already been set or the MF
Only when the MF switch 38 is not operated in the mode and the zoom operation is being performed, the focus correction amount at the time of zooming (the correction amount for keeping the imaging position constant) is determined.

The determination of the correction amount is peculiar to the inner focus method, and the focus lens 11 is located at a lens position at which a subject at a certain subject distance (distance between the subject and the camera) can be kept in focus. In this case, if a zoom operation is performed on the telephoto (TELE) or wide-angle (WIDE) side, it is necessary to correct the position of the focus lens in accordance with the zoom operation, that is, the change in the focal length. For example, as shown in FIG. For a subject whose subject distance is infinity, correction along the straight line L1 is necessary.
In addition, for a subject whose subject distance is 1 m, correction along the straight line L2 is necessary. The straight lines for correction differ depending on the subject distance. These straight lines are prepared in advance when designing the lens unit, and each straight line is stored in the motor control circuit 9. Accordingly, a correction curve is selected in FIG. 11 from the subject distance determined as described later, and a change in the focal length corresponding to the lens position of the zoom lens to be displaced by the zoom operation is input, thereby performing focus correction. The amount is calculated by the motor control circuit 9 (step 10).
5).

Next, an AZ flag setting subroutine (step 106) of FIG. 10 is executed. First, in the subject monitoring mode (MODE = 4), a timing signal TS is issued and the latest relative ratio R is stored in the second memory 43 as the reference relative ratio RMAX (step 199). Note that in a mode other than the subject monitoring mode, the reference relative ratio is not updated, and the value when MODE = 4 last time remains as it is. Next, it is determined whether or not the zoom switch 39 is operated (step 200). If the zoom switch 39 is being operated, the zoom motor 2 is driven in the direction specified by the zoom switch 39 (step 201). The determination of the resumption of focusing when the ratio R is used is | R-RMAX |> RMA
A comparison of X / 2 is made (step 202). When the difference between the latest relative ratio R and the reference relative ratio RMAX exceeds 1/2 of the reference relative ratio in this way, it is determined that the in-focus state has deviated greatly, and the AZ flag is reset (step 20).
6). By the operation of step 206, in the subject monitoring mode, the change in the relative ratio is monitored, and the reference relative ratio RMAX is monitored.
If there is a change by a predetermined amount, it means that the lens position correcting operation is not executed. At this time, if the mode is the MF mode (MODE = 5), MODE = 1 is set and restart of the focusing operation is instructed (steps 204 and 205). Also,
By the operation of step 206, in the subject monitoring mode,
The difference between the latest relative ratio and the reference relative ratio is １ ／ of the reference relative ratio.
If the value is less than, it is determined that the in-focus state is maintained, the mode is set to MODE = 5, the MF mode is set, the autofocus operation is stopped, and the AZ is executed to execute the lens position correction operation.
A flag is set (step 203). This allows
A zoom focus operation under the MF mode, that is, a lens position correction operation is performed without performing any autofocus operation.

On the other hand, if the zoom switch 39 is not operated, the zoom motor 2 is stopped (step 21).
At 0), it is determined whether or not the AZ flag is set (step 211). If the flag is set,
| R-RMAX |> RMAX / 2 (step 212), and if the difference is less than 1/2 of the reference relative ratio and immediately after the zoom motor 2 stops, the subject monitoring mode (MODE = 4) Then, the allowable step number M at the time of the fine adjustment is changed from 6 to 12 (step 213). Due to the increase in the allowable step number M, it is difficult to restart the focusing operation. If the difference is larger than 1/2 of the reference relative ratio, the process proceeds to step 204 or 206, and the same operation as described above is executed.

After the execution of the AZ flag setting subroutine, the AF / MF switching process is performed (step 10).
7). This is a process performed when the operator operates the AF / MF switch 37. When the operator performs switching between the AF mode and the MF mode during the corresponding field period, if the MF mode is designated, the current operation is performed. Regardless of the mode (MODE1 to MODE4) of the autofocus operation, the mode is forcibly switched to the MF mode of MODE = 5, and A
When the F mode is designated, MODE = 1 is executed from the direction determination mode.

In this way, the operation corresponding to any one of MODEs 1 to 5 is executed to complete the operation for one field. Here, in the MF mode (MODE = 5), the operation according to the flowchart shown in FIG. 14 is performed.
In this routine, it is first determined whether or not the MF switch 38 is being operated (step 400). If the MF switch is being pressed, the focus motor 4 is rotated in the pressed direction (step 401). By manually displacing the focus lens 11 in a direction desired by the operator (in the direction of infinity or in the direction of near point), manual focus control becomes possible. If it is determined that the MF switch 38 is not being operated by the operator, it is determined whether the FS flag is in a reset state (step 402). The zoom position at this time is telephoto (T) from the reference position Z shown in FIG.
It is determined whether the side is the ELE) side or the wide-angle (WIDE) side (step 403). If it is on the telephoto side from the reference zoom position Z, the subject distance determined by the focus lens position H and the zoom position at this time is stored as it is (step 403). Step 405) If the zoom position is wider than the reference zoom position Z, the focus lens position H at this time is changed to the preset reference lens position X.
1, X2 and X3 are compared (step 404). If less than X1 (condition 1), the subject distance is set to D1 (step 408). If X1 or more and less than X2 (condition 2), the subject distance is set to D2. (Step 407), X is equal to or greater than X2.
If it is less than 3 (condition 3), it is set to D3, and if it is more than X3 (condition 4), the subject distance determined from the focus lens position H and the zoom position at this time is stored as it is (step 4). 406). Here, the horizontal axis of FIG. 12 indicates the position of the focus lens 11,
Specifically, it is indicated by the amount of movement of the focus lens 11 from the point at infinity. As can be seen from this zoom correction curve, since the curves of the object distances are extremely dense on the wide angle side from the reference zoom position Z, it is difficult to determine the object distance from the lens position with high accuracy. Therefore, as described above, it is necessary to take measures to make the subject distance as easy as possible and not to cause a significant malfunction in the zoom focus operation.
The significance of 408 will be described in detail.

Generally, in actual photographing, a subject at a long distance is more strongly photographed than a subject at a short distance.
Malfunctions are less likely to occur if the distant subject is always focused. Therefore, when Condition 1 is satisfied, D1 (for example, 10 m), which is the subject distance of the curve L11 in which the farthest subject distance is relatively close to the curve L10 at infinity, among the curves within the range of Condition 1 adopt. Condition 2
Is satisfied, the subject distance D2 (for example, 5 m) of the curve L12 farther than all the curves satisfying this condition is satisfied.
Is adopted. The subject distance D3 (for example, 2.3 m) of the curve L13 farther than all the curves satisfying the condition 3
Is adopted. Further, when the condition 4 is satisfied, that is, when the subject distance is away from the dense portion such as when the subject distance is 0.2 m or 0.05 m as shown by the curves L14 and L15, the angle of view is wider than the reference zoom position Z. Since the object distance can also be determined with high accuracy from the lens position on the side, each lens position is held as it is as the object distance.

When the determination of the object distance is completed,
The FS flag is set, then step 105 in FIG.
The position of the lens 11 is corrected by driving the focus motor 4 by the correction amount determined in. Here, step 4
The subject distance set in 05 to 408 does not contribute to the correction operation in step 410 immediately after, but contributes to the determination of the correction amount when passing through step 105 in the next field. When the main routine of FIG. 9 is first executed, the object distance is not determined, so that the correction amount cannot be determined in step 105 and the correction amount is not determined.

The above is A for executing the autofocus operation.
This is an F routine, and this AF routine is repeatedly executed for each field.

In determining the correction amount in step 105, it is necessary to detect the subject distance. The work of detecting the subject distance from the zoom position and the focus lens position using the characteristic diagram of FIG. If not, it is only necessary to detect once, so if the FS flag is in the set state, the subject distance set immediately before is used as it is, and no new detection work is performed.

Therefore, when the zoom position is on the telephoto side of the reference zoom position Z or when the focus lens 11 is in focus at a position closer to the near point than the reference lens position X3, the process proceeds from step 403 in FIG. 405, and when the zoom position is moved from this position to a wider angle side than the reference zoom position Z and the focus lens position is moved to a point farther than the reference lens position X3, the subject or the like changes. Without | R-RMAX | is RMAX
/ 2 or less, go through step 203 in FIG.
The flag is set. At this time, FIG.
Steps 306 to 308 are skipped, and F
The S flag is not reset. Further, since the object jumps from step 402 to step 409 in FIG. 14, the object distance is not updated from the value at the start of the zoom operation.

Immediately after the end of the zoom operation, the process goes through steps 212 and 213 in FIG. 10 and enters the subject monitoring mode of MODE = 4. Further, the object distance jumps over steps 306 to 308 in FIG. 13 and further jumps from step 402 to 409 in FIG. Therefore, once a reliable subject distance is stored near the telephoto end when the zoom position is near, even if the zoom operation is performed near the wide-angle end, the relative ratio fluctuates due to a change in the subject, etc., and | R− RMAX |
Until> RMAX / 2 is satisfied, the highly reliable object distance is kept stored, and even when zooming in the telephoto direction again, the in-focus state is maintained to perform the zoom focus operation according to this object distance.

[0036]

As described above, according to the present invention, even when the zoom position is on the wide-angle side and the subject distance cannot be detected with high accuracy, the correction amount of the lens can be determined easily and with relatively little malfunction. Even if zooming is performed in the telephoto direction from the wide-angle end, the possibility of a large deviation from the actual correction curve and falling into an out-of-focus state can be minimized.

[Brief description of the drawings]

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

FIG. 2 is a main part circuit block diagram of one embodiment of the present invention.

FIG. 3 is a diagram illustrating a hill-climbing focusing operation.

FIG. 4 is a diagram illustrating a relationship between a lens position and a focus evaluation value.

FIG. 5 is a diagram showing a relationship between a degree of blur and a relative ratio.

FIG. 6 is an explanatory diagram of a fine adjustment operation.

FIG. 7 is an explanatory diagram of a fine adjustment operation.

FIG. 8 is an explanatory diagram of a fine adjustment operation.

FIG. 9 is a flowchart of a main routine when performing an autofocus operation.

FIG. 10 is a flowchart of an AZ flag setting routine.

FIG. 11 is a diagram illustrating a relationship between a focus lens position and a focal length.

FIG. 12 is a diagram illustrating a relationship between a focus lens position and a zoom position.

FIG. 13 is a flowchart of a SW processing subroutine.

FIG. 14 is a flowchart of a subroutine in a manual mode.

[Explanation of symbols]

 Reference Signs List 10 Zoom lens 11 Focus lens 3 Zoom encoder 12 Counter 8 Focus control circuit 9 Motor control circuit

Claims (1)

(57) [Claims] 1. An autofocus camera having a lens system having a function of changing magnification and changing an image forming position according to a focal length, wherein a focal length variable which varies a magnification by moving a lens group which controls the focal length. Means, first position detecting means for detecting the position of the lens group which controls the focal length, focus control means for controlling the position of the lens group which controls focusing, and detecting the position of the lens group which controls the focusing The second position detecting means and the focus control means determine the output of the second position detecting means once the focusing state has been reached as a subject distance, and determine the output from the subject distance and the output of the first position detecting means. Zoom focus means for performing a zoom focus operation for displacing the lens group that controls the focusing to a lens position; and a zoom position by the lens group that controls the focal length is near a wide-angle end. Wide-angle end determining means for detecting whether or not the zoom lens is in the vicinity of the wide-angle end, and determining which of a plurality of preset lens ranges the lens group responsible for focusing is located in; A lens position determining unit that performs zooming when the zoom position is near the wide-angle end.
A specific subject distance preset for each lens range is adopted in place of the output of the position detecting means, and each of the specific subject distances is determined from an intermediate value between the shortest subject distance and the longest subject distance in the corresponding lens range. An autofocus camera characterized in that it is also set at a long distance.