JPH083573B2 - Focus adjustment device - Google Patents

Description

The present invention relates to a focus adjustment device used in a video camera or the like.

[Prior Art] Even during manual focusing, driving force generating means such as a motor is operated so as to respond to the operation of a manual operation element such as a range ring or a switch, and the focusing lens is displaced by this driving force generating means. A focus adjusting device for performing focus adjustment has already been proposed. An example of this type of device is as follows. That is, in the zoom lens, the position of the variator lens group and the compensator lens group and position required for focusing corresponding to the position of this variator lens group are stored in the storage means, and the in-focus state is once obtained. After that, when zooming is performed to change the position of the variator lens group, the driving force generation means such as a motor is operated based on the output of the storage means to move the compensator lens group to the in-focus position. There has been proposed an apparatus for maintaining a focus state (see Japanese Patent Laid-Open No. 60-143309). This is an autofocus mode for a zoom lens whose focus position changes when the variator lens group is moved for zooming (a type in which focus is adjusted by moving the compensator lens group, which is the rear lens). However, if the focus is adjusted manually, the in-focus state is maintained in order to eliminate the defocused state caused by zooming. As a result, there is a problem in that the lens is again in a defocused state. Therefore, in order to solve this problem, the lens is moved by the driving force generating means even during manual focusing as described above.

For this reason, there is provided a storage unit that stores the position of the variator lens group and the position of the compensator lens group that is necessary for focusing and that corresponds to the position of the variator lens group. Then, the compensator lens group is moved to a corresponding position to obtain a focused state.

[Problems to be Solved by the Invention] However, an extremely large number of positions of the variator lens group and the positions of the compensator lens group necessary for focusing, which correspond to the positions of the variator lens group, must be stored in advance. Of course, this requires a large-capacity storage means, resulting in high cost.

Therefore, it is an object of the present invention to provide an inexpensive focus adjustment device that requires a relatively small storage capacity.

[Means and Actions for Solving Problems] A focus adjusting apparatus according to the present invention includes a lens system including at least a variator lens group and a focusing lens group movably provided for focus adjustment, and There are multiple zoom sensors that detect the zooming state based on the position of the variator lens group, and multiple focus curves that represent the position of the focusing lens group to obtain an appropriate focus state according to the zooming state and the focus setting distance. When the storage means for storing, the driving force generating means for moving the focusing lens group, and the set focus setting distance correspond to any of the plurality of focus curves, The appropriate focusing lens position corresponding to the detection output of the zoom sensor at that time point is determined and set based on the corresponding focusing curve. When the focused focus setting distance does not correspond to any of the plurality of focusing curves, the appropriate focusing of the stored focusing curves is performed according to the detection output of the zoom sensor. A focusing means for calculating a focusing lens position by calculation based on a curve, and a control means for outputting an output for operating the driving force generating means to move the focusing lens group to the determined focusing lens position. And

[Examples] FIG. 1 is a block diagram showing a focus adjusting device as an example of the present invention. The apparatus shown in FIG. 1 is an application of the present invention to a video camera. The imaging lens barrel 1 in the video camera has a built-in lens system including a front lens group 2, a variator lens group 3, a diaphragm 4 and a focusing lens group 5 which is a so-called rear group lens. The variator lens group 3 and the focusing lens group 5 are arranged so as to be movable in the optical axis direction. Details of the mechanism for movably supporting the focusing lens group 5 are shown in FIG. As shown in the figure,
The focusing lens group 5 is held by a lens holding frame 7 which is guided by a guide rod 6 arranged substantially parallel to the optical axis thereof and is movable in the optical axis direction. An engagement pin 7a is provided on the lens holding frame 7 so as to project in the radial direction of the lens, and the engagement pin 7a is engaged with a feed screw 9 which is rotationally driven by a stepping motor 8 as a driving force generating means. Therefore, as the feed screw 9 rotates, the lens holding frame 7 holds the focusing lens group 5 through the engaging pin 7a and along the optical axis direction, the arrow A or the arrow B.
Move in the direction of. The stepping motor 8 is driven as a control means by a motor drive circuit 11 that supplies motor drive power based on the output of the control unit 10. Further, as shown in FIG. 2, a light shielding piece 7b is provided on the lens holding frame 7 so as to protrude along the optical axis direction so as to correspond to the zero point sensor 12 made of a photo interrupter. When the zooming is set to the tele side and the focusing is performed at the infinite position, the focusing lens group 5 reaches the limit position in the B direction in the adjustment movement range, but at this time, the light blocking piece of the lens holding frame 7 is reached. 7b reaches the zero point sensor 12, and the zero point sensor 12 outputs a detection output. In this device, the position of the focusing lens group 5 at this time is set as the reference position (zero point). The output of the zero point sensor 12 is supplied to the control unit 10. on the other hand,
The variator lens group 3 described in FIG. 1 is also held in substantially the same manner as the focusing lens group 5, and can be moved along the optical axis direction by manual operation or by the motor 20. The motor 20 is driven by a zoom motor drive circuit 22 that operates based on the operation of the zoom switch 21. The position of the variator lens group 3 moving along the optical axis direction is detected by a zoom sensor 23 including, for example, a position sensor in the form of a potentiometer or an encoder, and based on this, a detection signal indicating the degree of zooming at that time. Is output from the zoom sensor 23 and supplied to the control unit 10. Further, the aperture value of the aperture 4 is detected by the aperture sensor 24, and the detection output of the aperture sensor 24 is given to the control unit 10. The image pickup device 25 is arranged to receive the image from the lens system on the image pickup surface,
The photoelectric conversion output by the image pickup device 25 is a video signal processing circuit.
A predetermined signal processing is applied to the video signal 26, and a video signal corresponding to the subject is obtained from the video signal processing circuit 26. The luminance signal of the video signal is also derived from the video signal processing circuit 26, and the high frequency component detection circuit 27
Is configured to be supplied to. The high frequency component detection circuit 27 is for extracting the high frequency component contained in the luminance signal and supplying this to the control unit 10 as information on the degree of focus required for operation in the autofocus mode described later. The control unit 10 is also connected to an auto / manual switch 28 and a manual switch 29 for adjusting the focus in the manual focusing mode. By switching the position of the auto / manual switch 28, the control unit 10 selectively switches between the autofocusing mode and the manual focusing mode. The focus setting distance corresponding to the operation of the manual switch 29 is displayed on the distance display device 30 such as a liquid crystal display device based on the output of the control unit 10.

An outline of the operation of the device of the present invention configured as described above will be described below. By switching and selecting the position of the auto / manual switch 28 to "manual", the operation mode of the control unit 10 becomes the manual focusing mode. In the manual focusing mode, the operator visually adjusts the operation of the manual switch 29 and visually displays it on a monitor or an electronic viewfinder (neither of which is shown) which displays an image by the video signal output from the video signal processing circuit 26. Adjusting the focus setting distance while checking the focus status (focusing)
Perform Set the focus setting distance (focus) to the short distance side (hereinafter,
Set to N side) or set to the far side (hereinafter,
Based on the operation of the manual switch 29 depending on whether the focus lens group is set to the infinity side), the control unit 10 controls the focusing lens group at a predetermined speed corresponding to the degree of zooming identified by the signal provided from the zoom sensor 23. A motor drive signal is output to the motor drive circuit 11 in order to move 5. The motor drive circuit 11 power-amplifies this motor drive signal and rotationally drives the stepping motor 8, whereby the focusing lens group 5 moves in the optical axis direction. In the control unit 10, the zoom sensor 23
When the position of the variator lens group 3 which is identified from the detection output of the focusing lens group 3, that is, the zooming state is set to a position close to the tele side, the moving speed of the focusing lens group 5 becomes relatively fast, When the position is set close to, the moving speed of the focusing lens group 5 is controlled to be relatively slow. As a result, the focusing speed becomes substantially constant regardless of whether the zooming state is set to the tele side or the wide side. That is, the time required to change the focus setting distance over the full range of N∞ can be made substantially constant. The adjustment of zooming can be performed by operating the zoom switch 21 as described above or by manually operating a zoom ring or the like (not shown). Generally, in the lens system in which the rear lens group is the focusing lens group as in the present embodiment, even if the focusing lens group is once set to the in-focus position, if the zooming state is changed, it becomes out of focus. The control unit 10 stores the data of the focusing lens position necessary for obtaining the focus according to both the zooming state and the set distance, and even if the zooming changes, the data or the calculation based on this data is performed. The focusing lens group is controlled so as to always trace the proper position for focusing.

FIG. 3 shows the position of the focusing lens group 5 (that is, from the reference position of the focusing lens group 5 detected by the zero point sensor 12) for obtaining the focused state according to both the zooming state and the focus set distance. 3 is a focusing curve representing the amount of feeding of the image. In FIG. 3, the horizontal axis represents the amount of extension of the focusing lens group 5 from the reference position,
The vertical axis represents the zooming state such as telephoto (T), standard (S), and wide (W), that is, the amount of movement of the variator lens group 3. The curve l ₁ shown by the broken line is the focus setting distance (focus)
Is “infinity (∞)”, the curve l ₂ shown by the alternate long and short dash line is 1 m
And the curve l ₃ indicated by the chain double-dashed line represent the relationship between the moving amount of the variator lens unit 3 and the moving-out amount of the focusing lens unit 5 when the focus is 0.5 m. As can be easily understood from this figure, when the variator lens group 3 is at the position corresponding to the telephoto (T), the focusing lens group for obtaining the focus for each focus setting distance of "infinity", 1 m, and 0.5 m. The amount of each of 5 is a1, a
It is 2, a3. Also, the variator lens group 3 is standard (S)
When in the corresponding position, the respective amount of extension of the focusing lens group 5 for obtaining the in-focus with respect to the in-focus set distance is b1, b2, b3, respectively. Similarly, the amount of extension of the focusing lens group 5 for obtaining the in-focus states corresponding to the wide (W) equivalent position of the variator lens group 3 is c1, c2, c3. As can be understood by comparing the shapes of the respective focus curves l ₁ , l ₂ and l ₃ , the curvatures of the focus curves are different when the focus setting distance is different. Therefore, it is extremely difficult to control the position of the focusing lens unit by a mechanical means such as a cam in order to obtain the in-focus state for an arbitrary zooming state and in-focus set distance. In the above, the desired focusing state can be obtained with a simple structure in which the above curve is traced by the electronic storage and calculation means in the control section 10.
When the focusing curve is stored as data and the focusing lens position required for focusing is obtained by tracing this curve, in order to correspond to various focus setting positions, the above-mentioned focusing curves l ₁ and l ₃ It is necessary to set not only the curve l ₂ but also an extremely large number of curve groups and store all the data relating to these curve groups in advance, but this requires a large-capacity storage means. I will end up. For this reason,
In the device of the present embodiment, only the curve l ₁ corresponding to the set distance “infinity” and the curve l ₃ corresponding to the set distance “0.5 m” among the focusing curves are stored as data in the storage means, and The extension amount of the focusing lens group 5 corresponding to the set distance located in the middle of is calculated by calculation. That is, the full range of the variable range of the set distance by the manual switch 29 is divided into n equal parts, the set distance is set to a value D within this full range, and the amount of extension of the focusing lens group 5 on the focusing curve l ₁ (set distance ∞). Is X _∞ , and the amount of extension of the focusing lens group 5 on the focusing curve l ₃ (set distance 0.5 m) is X _N , the amount of extension S of the focusing lens group 5 corresponding to the above set distance D is Can be obtained as Therefore, in the device of the present embodiment, in correspondence with the zooming information by the zoom sensor 23 and the focus setting distance information by the manual switch 29,
An appropriate focusing lens extension amount is calculated by the calculation based on the focusing distances l ₁ and l ₃ and the above formula (1).

As shown in the drawing, the horizontal distance between the focus curves l ₁ and l ₃ is wide when the zooming is on the tele (T) side, and is extremely narrower than the T side when the zooming is on the wide (W) side. Therefore, also from FIG. 3, as described above, when the zooming is set to the T side, the moving amount of the focusing lens unit for focus adjustment is relatively large,
It will be easily understood that when the zooming is set to the W side, the moving amount of the focusing lens unit for focus adjustment becomes extremely small. Therefore, in the apparatus of the present invention, the focusing lens unit is moved at a relatively high speed on the T side and at a relatively low speed on the W side, so that the rate of change in focus adjustment is substantially independent of zooming. I try to keep it constant.

On the other hand, when the position of the auto / manual switch 28 is switched to "auto" and selected, the operation mode of the control unit 10 becomes the auto focusing mode. In the auto-focusing mode, the control unit 10 receives information regarding the zooming state from the zoom sensor 23 and information regarding the diaphragm from the diaphragm sensor 24, and receives from the high frequency component detection circuit 27 the high-frequency component of the luminance signal indicating the degree of focusing ( Focus information) is obtained, an appropriate position of the focusing lens group is calculated from each of these pieces of information, and a motor drive signal is output to the motor drive circuit 11 in order to position the focusing lens group at that position. As a result, the focusing lens group 5 is controlled to an appropriate position for focusing even if the zooming or diaphragm state changes.

In the device of the above embodiment, the control unit 10 is mainly composed of a microcomputer.

FIG. 4 is a block diagram showing the function of the control unit 10, and FIG. 5 is a flow chart showing details of the operation of the control unit 10. Next, the function and operation of the apparatus of this embodiment will be described in more detail with reference to FIGS. 4 and 5. In the embodiment shown in FIG. 4, an automatic restoration type seesaw type two-contact switch is used as the manual switch 29. Auto / manual switch
When 28 is set to the "manual" position, each functional unit related to the manual focusing mode described below is in operation. As shown in the flowchart of FIG. 5, this is the operation of the main routine that performs various known operations related to various arithmetic operations for autofocusing, monitoring of operation parts such as switches and camera-side control such as iris control. Is a part that shifts to the operation of reading the state of the manual switch. When the operator 29 'of the manual switch 29 is rotated clockwise in the drawing, the contact 29a is closed and the short distance side (N side)
The set distance to the infinity side (∞) is changed by closing the contact point 29b by rotating counterclockwise. Since one pole of each contact of the manual switch 29 is grounded and the other pole is connected to a positive potential through a pull-up resistor, the other pole of the closed contact has the closing time of the contact. It constitutes a manual command signal generating means for generating a manual command signal that has a medium ground potential. This manual command signal is read by the manual command signal identifying section 110 of the control section 10. When it is discriminated that one of the contacts of the manual switch 29 is on, a discrimination operation in the next operation direction (determination of which contact is on) is performed, and further zooming from the next zoom sensor 23 is performed. Move to the step of reading information about When it is identified that all the contacts of the manual switch 29 are off, the process immediately proceeds to the step of reading information regarding zooming (see FIG. 5). As shown in FIG. 4, the operating direction read by the manual command signal identifying unit 110, that is, the information indicating whether the set distance is further changed to the ∞ side or the N side is given to the counting / dividing unit 120. To be The counting / dividing unit 120 is configured to constantly supply the pulse output from the oscillating unit 130 at the stationary repetition frequency f, and the pulse of the manual switch 29 supplied from the manual command signal identifying unit 110. The function of the focus movement amount counter 121 for counting during the on-time is included. This focus movement counter 1
The count value at 21 corresponds to the change amount of the focus setting distance to be set manually. Zoom sensor
The frequency division value corresponding to the zooming information read from 23 is set in the frequency division value setting unit 140, and this frequency division value information is supplied to the counting / frequency division unit 120. The setting of the dividing value is
The frequency division value data stored in advance in the memory within the frequency division value setting unit is searched according to the output of the zoom sensor 23. The frequency of the pulse signal output from the oscillator 130 is f, and the frequency division value set by the frequency division value setting unit 140 is m.
Then, the frequency of the pulse signal divided and output in the counting / dividing unit 120 is f / m. Dividing value setting section 140
In the above, when the information that the zooming is set to the tele side is given from the zoom sensor 23, the above-mentioned m is given a relatively small value, and conversely, the information that it is set to the wide side is given. The above-mentioned m is set to a relatively large value. The pulse signal of the frequency of f / m output from the counting / dividing unit 120 is the motor control unit 200.
Given to. The motor control unit 200 outputs a drive signal to the motor drive circuit 11 to drive the stepping motor 8 (see FIG. 1) at the frequency of f / m. Therefore, when the zooming state is set to the tele side, the rotation speed of the stepping motor 8, that is, the focusing lens group 5
When the zooming state is set to the wide side, on the contrary, the moving speed of the focusing lens group 5 becomes relatively low, and as described above, it does not matter regardless of the zooming setting. The rate of change of the focus state becomes substantially constant.

The operation after the step of reading the output of the zoom sensor 23 will be described in detail again with reference to the flowchart shown in FIG. When it is determined in the frequency division value setting unit 140 that the zooming information has changed in comparison with the previously read data, a new frequency division value m is reset and the f / m of the above f / m in the counting / frequency division unit 120 is reset. The frequency division number is determined. On the other hand, even if the focus set distance is not changed, if the zooming state is changed, the focus state for the set distance is maintained unless the position of the focusing lens group 5 is adjusted as described in FIG. Can not do it. Therefore, in this device, the zooming information is sent to the motor control unit.
The position of the focusing lens group 5 for maintaining the in-focus state is calculated by the motor control unit 200 according to the change of the zooming information. That is, the motor control unit 200 sets the data relating to at least the curves l ₁ and l ₂ among the focusing curves shown in FIG. 3, for example, the data from the focusing curve storage unit 300 including a ROM, the zooming information. Further, in order to recognize the focus setting distance at that time, the focus setting distance counter 201, which is a function provided inside itself, is used to maintain the focus by the formula (1) described in FIG. The required position of the focusing lens group 5 is calculated. A lens position storage unit 210 that stores the current position of the focusing lens group 5 while updating the current position each time it changes is provided.
Functions to exchange information with the lens position storage unit 210.

On the other hand, when the zooming information has not changed, it is determined again by referring to the manual command signal identification unit 110 whether or not the manual switch 29 is turned on, and when not turned on, the control unit 10 The operation returns to the main routine again. Manual switch 29
When it is determined that is ON, and when the moving amount of the focusing lens group 5 is calculated by following the zooming in the motor control unit 200 as described above, the data stored in the lens position storage unit 210 When the focusing lens group 5 is at the focusable limit position in the ∞ direction or the N direction (position on the curve l ₁ or l _{3 in} FIG. ₃ ), the direction of change of the focus setting distance that has already been determined is the above limit. The motor control unit 200 checks whether or not the direction is beyond the position. As a result of this check, when it is determined that the setting is not changed in the direction in which the limit position is exceeded, the value of the focus movement amount counter 121 of the counting / dividing unit 120 is read. The count value of the counter 121 is the oscillation unit 13 counted during the ON time of the manual switch 29.
It is the number of input pulses from 0, and the value as described above corresponds to the change amount ± ΔD of the focus setting distance. The value of the focus movement amount counter 121 is given to the motor control unit 200, and addition / subtraction (D ₀ ± ΔD) is performed on the value of the focus setting distance counter 201 representing the current value D ₀ of the focus setting distance. That is, the result of the addition / subtraction represents the new focus setting distance D ₁ . The motor control unit 200 substitutes this value of D ₁ into D in the above equation (1) to calculate the position S ₁ of the new focusing lens group for maintaining the focus. The value of the lens position storage unit 210 is changed to the value of S ₁ thus obtained.

In the system of the present embodiment, the position of the focusing lens group can be constantly recognized in the lens position storage unit 210 with a relatively high resolution as the count value of the pulse having a relatively short cycle which is the output of the oscillation unit 130. Has become. That is, all the positions of the focusing lens group calculated by the equation (1) calculated by the motor control unit 200 are also expressed with such accuracy. On the other hand, as described with reference to FIG. 3, when the zooming is set to the wide side, the amount of movement of the focusing lens group 5 for focus adjustment is smaller than that when the zooming is set to the tele side. The number of rotation steps of the stepping motor 8 (see FIG. 1) for adjusting the focus between ∞N in
It is much less than that on the tele side. Therefore, if the system is constructed so that the position of the focusing lens group is recognized by the number of rotation steps of the stepping motor, it will be 1 between ∞N on the wide side.
Since the steps have a relationship corresponding to several steps on the tele side, the accuracy of the focusing lens group position on the wide side becomes a fraction of that on the tele side. As a result, after the in-focus state is once obtained on the wide side, when moving the zooming state to the tele side, the focusing lens group is driven along the above-mentioned focusing curve to maintain the in-focus state. In this case, since the resolution of the lens position expression on the wide side is coarse, it becomes impossible to specify the normal position for focusing on the tele side. In view of such a point, in the system of the present embodiment, in the lens position storage unit 210, regardless of how many steps are set between the focus setting distances ∞N depending on the number of steps of the stepping motor, the above-described operation is always performed. As described above, since the focusing lens position is stored with a constant high resolution, the above-mentioned inconvenience does not occur.

New focusing lens group position as described above
When S ₁ is calculated, this S ₁ is compared with the current position S _{0 of the} lens, and the value of S ₁ −S ₀ obtained at this time corresponds to the number of steps of the stepping motor 8 Is calculated. When S ₁ -S ₀ is less than one step is,
Return to the main routine. When the number of steps is calculated, the motor control unit 200 issues a drive signal to the motor drive circuit 11 to drive the stepping motor 8 by the number of steps. When the stepping motor 8 is driven by the number of steps described above, the motor drive circuit 11 is turned off and the process returns to the main routine.

The above is an explanatory diagram for the case where the apparatus of this embodiment operates in the manual focusing mode. Next, the case where the apparatus operates in the automatic focusing mode will be described.

When the position of the auto / manual switch 28 is selected to be "auto", the respective function units related to the auto focusing lens mode described below are activated. Fourth
In the figure, the autofocus calculation control unit 400 set in the control unit 10 includes aperture information from the aperture sensor 24, zooming information from the zoom sensor 23, and the high-frequency component detection circuit 27 to the A / D conversion unit 500 described above. Focusing information digitized via the respective units is supplied. Further, the automatic focus calculation control unit 400 is configured to exchange data with the storage unit 410, and is supplied with the data from the focus curve storage unit 300 described above. The autofocus control information output from the autofocus calculation control unit 400 is given to the motor control unit 200, and the motor control unit 200 drives the stepping motor 8 to rotate by the required number of steps through the motor drive circuit 11 based on this control information. Let The control method in the autofocusing mode of the apparatus of this embodiment is basically
This is the so-called hill-climbing servo system (see NHK Technical Research Vol. 17, Vol. 1, No. 86 (Volume 86), page 21 "Automatic focus adjustment of TV cameras by hill-climbing servo system"). In principle, this method is as follows. The level of the high frequency component of the luminance signal becomes higher as the contrast of the image formed on the image pickup surface of the image pickup means becomes sharper. Therefore, the level of the high frequency component is focus level information indicating the degree of focusing. In this method, the lens is moved first, and the resulting change in focus level is extracted. If the change is positive, the moving direction of the lens matches the direction in which it is in focus. If the change is negative, the lens is moved in the opposite direction to the moving direction, and while repeating such movement, the point where the focus level becomes maximum is to be found as the in-focus position. is there.
In the apparatus shown in FIG. 4, the focusing lens group 5 is driven to a minute step, and the high frequency component detection circuit 27 is driven each time.
By comparing the focus level information obtained through the A / D conversion unit 500 with the focus level immediately before stored in the storage unit 410, the lenses are sequentially driven in the direction in which the focus level increases, and Perform focus adjustment operation. The calculation related to this operation is performed by the autofocus calculation control unit 40.

On the other hand, the detected focus level changes differently depending on whether the contrast of the subject itself is high or low. As shown by the curve A ₀ , for a subject with a high contrast as shown in FIG. 6, when the lens is in the in-focus position, the level difference between the front focus position and the rear focus position is relatively large and steep. A mountain-shaped focus level characteristic in which an apex is formed is obtained. However, for a subject with low contrast, the focus level characteristic becomes a gentle curve, as shown by the curve B ₀ . Therefore, in this method, focus detection can be accurately performed on a subject with high contrast, but focus detection on a subject with low contrast becomes relatively difficult. Therefore, in the apparatus of this embodiment, as shown in FIG. 6, the limit level L is set as a predetermined level according to the focus level when out of focus, and when the focus level is below the limit level L, the focusing lens is set. The initial movement direction of the group 5 is set to the direction of the ordinary focus position, and while checking the change of the focus level, the lens is gradually driven to operate so as to search for the peak position of the focus level. At the time of initial movement of the lens, if the lens is already at the normal focus position, the lens is moved in the short distance direction and the same operation is performed.
The method of detecting the peak position is as follows.

(1) A point at which the focus level is larger than the limit level and the focus level does not change even if the lens is moved is detected. That is, near the top of the curve A ₀ shown in FIG.
In reality, such a position is found because the depth of focus occurs and the focus level does not change.

(2) When only a gentle curve is obtained as the focus level characteristic, such as the curve B ₀ shown in FIG. 6, the initial moving direction of the lens is set to the normal focus position, and the lens is moved in the forward and backward limit range. One reciprocal scanning is performed in the inside, and during this scanning, the maximum value of the focus level according to the progressive movement of the lens is stored together with the number of driving steps of the stepping motor at each time point, and based on this memory, the final focus level is stored. Find the peak position.

The operation of (1) above is prioritized over the operation of (2) above so that malfunctions of focus adjustment are minimized. In the initial stage of the operation, even if the operation is started by the operation of (2) above, if the clear peak value is found in the middle, the operation of (1) above is performed. In the operation (2), when the focus level is equal to or lower than the limit level L in the entire scanning range, the lens is set to the normal focus position, the energization of the stepping motor is stopped, and the focusing is performed. While increasing the probability of
I try to save power. In addition, the focus level when the lens is set at the in-focus position or the normal focus position is stored in the storage unit 410, and the stored level is constantly compared with the focus level obtained at the present time,
When the current value of the focus level takes a value different from the stored level for a predetermined time or more, the stepping motor is activated and the autofocusing operation is restarted. The predetermined time is set in order to prevent malfunction due to noise and to suppress an irritable reaction when something temporarily crosses in front of the subject.

As described with reference to FIG. 3, in a device that generally drives a rear lens group to perform focusing, it is necessary for focus adjustment when the zooming state is set to the wide (W) side. Since the amount of movement of the lens is extremely small, almost no adjustment is required as in the case of a fixed focus lens. Further, even when the zooming is set to the standard (S), the lens displacement amount between ∞N is substantially included in the range of the depth of focus when the diaphragm is narrowed down considerably deep. . Therefore, in the apparatus of the present embodiment, the autofocus calculation control unit 400 constantly reads the aperture value and zooming information from the aperture sensor 24 and the zoom sensor 23, and the adjustment displacement amount of the lens between ∞N is within the range of the depth of focus. In a situation where it is included, set the focusing lens at a predetermined position within the depth of focus, automatically stop the autofocusing operation, turn off the power to the stepping motor, and save power. is there.

Further, even in the operation in the normal autofocusing mode described above, the lens is not driven within the range that can be covered by the depth of focus, so
Compared with the case where the lens is moved over the entire section between N, the actual lens movement range is extremely limited, and the restraining autofocusing operation is realized.

In general, when focusing is performed by moving the rear lens group, it is possible to focus up to the close-up distance without so-called macro switching. However, if the lens is moved for the autofocusing over the entire range between the close-up distances ∞, the range of movement of the lens is large, so that it may be difficult to obtain the focus. Therefore, in the apparatus of this embodiment, the first distance range (range of 1 m∞) is set as the normal distance, and the second distance range (less than 1 m) is set as the close-up distance. The lens is driven according to the range and the auto focusing operation is performed. This can be easily realized by constantly counting and controlling the number of driving steps of the stepping motor. When performing auto-focusing on a normal distance as described above, even if there is a subject in the close-up position, if the contrast of the subject is sufficiently high, or if the subject is close to 1 m in the close-up range, Since the focus level can be detected when the focusing lens reaches the vicinity of the position corresponding to the focusing distance of 1 m, the focusing lens group can be moved in the close-up corresponding position direction to obtain an appropriate focus state. However,
When the subject is within the range of the close-up distance and the contrast is weak, it is difficult to obtain an appropriate focus state as described above. In the apparatus of this embodiment, when the focus level is low, the focus detection is performed while scanning the focusing lens group by the method (2) described above for the auto-focusing operation. The focus is detected by performing the scanning first and performing the scanning in correspondence with the range of the close-up distance only when the focus cannot be detected by only this. By doing so, so-called automatic focusing in the macro range is possible. In addition,
When the focus is not finally detected even by scanning, the focusing lens unit is forcibly set to the normal focus position. On the other hand, since the photographer can clearly recognize the subject at the close-up distance, the setting of both the above-mentioned distance ranges to be the targets of the above-mentioned autofocusing can be switched by a macro switch manual switch (not shown). Further, a known distance sensor using infrared rays or ultrasonic waves may be provided to detect the distance range of the subject and switch between the above two distance ranges to be subjected to autofocusing in accordance with the detected distance range. By doing so, fast and reliable autofocusing can be realized.

On the other hand, the lens position data from the above-mentioned focusing curve storage unit 300 is supplied to the autofocusing calculation control unit 400. In principle, the focusing curve l ₁ in FIG.
It is impossible to obtain the in-focus state outside the range between 1 and _3, and the range in which the focusing lens can actually be moved is the third range due to the restrictions on the mechanism of lens movement.
It is limited to the range Sv shown in the figure. Therefore, in the apparatus of this embodiment, the range Sv is set in the focus curve storage unit 300, and control is performed so that the focus adjustment does not deviate from this range in any case. Is configured.

FIG. 7 is a block diagram showing a modification of the system shown in FIG. In FIG. 7, blocks corresponding to the blocks shown in FIG. 4 are designated by the same reference numerals, and detailed description thereof will be omitted. In the system shown in FIG. 7, a push button type automatic resetting type single contact switch 290 is applied instead of the seesaw type two-contact manual switch 29 shown in FIG. The focusing lens group 5 is moved while the contact 290a of the manual switch 290 is on. The control of the moving speed of the lens at that time is performed in the same manner as the system in FIG. 4 described above. When the switch 290 is turned off and then turned on again, the moving direction of the lens is reversed. That is, the ON time of the manual switch 290 is recognized by the operation time setting unit 111 in the control unit 10A, and the manual switch 290
Information relating to the ON time of is given to the counting / dividing unit 120 in exactly the same manner as in the system of FIG. The operation time setting unit 111 also causes the off-timer 112 to start the time counting operation from the time when the manual switch 290 is turned off. When the time counting operation of the off timer 112 is completed while the manual switch 290 is in the off state, the movement direction setting unit 113 is caused to function by the output of the off timer 112 to force the focus adjustment direction to the normal focus direction. Set it so that it can be changed. A manual command signal identifying unit 110A is configured including the operation time setting unit 111, the off timer 112, and the moving direction setting unit 113.

FIG. 8 shows a flowchart of the operation of the manual command signal identifying section 110A shown in FIG.

Read the status of the manual switch 290 and contact 290a
Determine whether is on or off. When the contact 290a is on, the process proceeds to the next step of reading information from the zoom sensor 23. The operation of this shift is completely the same as that described in the flowchart of FIG. 5, and the description thereof will be omitted.
When the contact 290a is off, it is determined whether or not the off timer 112 has already finished the time counting operation. Off timer 11
When it is determined that the time counting operation in 2 is completed, the moving direction setting unit 113 forcibly sets the moving direction information so that the focus adjustment direction is the normal focus position. If it is determined that the off-timer 112 has not finished the time counting operation, it is discriminated whether or not the time counting operation is the normal time counting operation that has been performed once the initialization is performed, and the time counting operation is the normal time counting operation. Return to the main routine. If the operation is not a regular time counting operation, the off timer 112 is initialized, the moving direction set by the moving direction setting unit 113 is reversed, and then the process returns to the main routine. This behavior is
This corresponds to the state immediately after the manual switch 290 is pressed and then turned off.

In the apparatus of each of the above-described embodiments, the operation mode is switched between the manual focusing mode and the autofocusing mode by the auto / manual switch 28 in a single action. The focus state will not be lost. Therefore, it is not necessary to perform focus adjustment again each time the operation mode is switched.

[Effect of the Invention] According to the focus adjustment device of the present invention, even if the focus curve of the set focus setting distance is not stored, the focusing lens is calculated by an operation based on each of the stored focus curves. Since the position can be determined, the storage means for holding the data representing the focusing curve need only have a relatively small capacity, and this kind of device can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram of a focus adjusting device showing an embodiment of the present invention, FIG. 2 is a configuration diagram showing details of a mechanism for movably supporting the focusing lens group in FIG. 1, and FIG. FIG. 4 is a characteristic diagram of a focusing curve showing the position of the focusing lens group for obtaining the focused state according to both the zooming state and the set focus distance, and FIG. 4 shows the control section of the device shown in FIG. FIG. 5 is a block diagram showing the function, FIG. 5 is a flow chart regarding the operation of the control unit of FIG. 4, and FIG. 6 is a characteristic diagram of a focus level obtained according to focus adjustment for different subjects, FIG. Is a book diagram showing a modified example of the system shown in FIG. 4, and FIG. 8 is a flowchart relating to the operation of the system shown in FIG. 3 ... Variator lens group 5 ... Focusing lens group 8 ... Stepping motor (drive generation means) 10, 10A ... Control section (control means) 11 ... Motor drive circuit (driving force generation means) 23 ... Zoom sensor 29,290 …… Manual switch (manual command signal generation means) 110,110A …… Manual command signal identification section (manual command signal generation means)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 5/232 A

Claims (1)

[Claims] 1. A lens system including at least a variator lens group and a focusing lens group movably provided for focus adjustment, and a zoom for detecting a zooming state based on the position of the variator lens group. A sensor, a storage means for storing a plurality of focusing curves representing the position of the focusing lens group for obtaining an appropriate focusing state according to a zooming state and a focus setting distance, and moving the focusing lens group. And the set focus setting distance corresponds to any of the plurality of focus curves, the zoom at that point in time depends on the corresponding focus curve. The appropriate focusing lens position corresponding to the detection output of the sensor is calculated, and the set focus setting distance is set to any of the plurality of focus curves described above. If it is not applicable, the focusing lens position is calculated by the calculation based on each appropriate focusing curve among the stored focusing curves according to the detection output of the zoom sensor, and the determined focusing lens position is calculated. And a control unit that outputs an output for operating the driving force generation unit to move the focusing lens unit.