JP3696894B2 - Lens control device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to lens control in an inner focus type lens system.
[0002]
[Prior art]
FIG. 4 shows a simple configuration of a general inner focus type lens system. In the figure, 101 is a fixed first lens group, 102 is a second lens group for zooming (hereinafter referred to as a zoom lens), 115 is a stop, and 103 is a fixed third lens group. , 104 is a fourth lens group (hereinafter referred to as a focus lens) having a focus adjustment function and a so-called competition function for correcting movement of the focal plane due to zooming, and 119 is an imaging surface of the image sensor.
[0003]
In the lens system configured as shown in FIG. 4, since the focus competition lens 104 has both a competition function and a focus adjustment function, a focus competition lens for focusing on the imaging surface 119 even when the focal lengths are equal. The position 104 varies depending on the subject distance.
[0004]
When the position of the focusing lens 104 for focusing on the imaging surface is continuously plotted when the object distance is changed at the position of the variable magnification lens, that is, at each focal length, a characteristic curve as shown in FIG. 2 is obtained. . During zooming operation, if the locus shown in FIG. 2 is selected according to the subject distance, and the focus lens 104 is moved along the locus, zooming without blurring becomes possible.
[0005]
On the other hand, in the front lens type lens system, a compensator lens independent from the variable power lens is provided, and the variable power lens and the compensator lens are coupled by a mechanical cam ring.
[0006]
Therefore, for example, when a knob for manual zoom is provided on the cam ring, and the focal length is changed manually, the cam ring will follow the rotation no matter how fast the knob is moved, and the zoom lens and Since the lens moves along the cam groove of the cam ring, the above operation does not cause blurring if the focus lens is in focus.
[0007]
In the control of the inner focus type lens system having the above-described features, a plurality of pieces of trajectory information shown in FIG. 2 is stored in a memory in the lens control microcomputer in some form to change the focus lens. In general, a locus is selected depending on the position of the double lens, and zooming is performed while following the selected locus.
[0008]
Further, since the position of the focus lens relative to the position of the variable magnification lens is read from the memory and applied for lens control, the position of each lens must be read with a certain degree of accuracy. In particular, as is apparent from FIG. 2, when the variable magnification lens moves at a constant speed or a speed close thereto, the inclination of the locus of the focus lens changes every moment due to the change in the focal length. This indicates that the moving speed and the moving direction of the focus lens change every moment. In other words, the actuator of the focus lens must actually respond with a precise speed response from 1 Hz to several hundred Hz. It will be.
[0009]
As an actuator that satisfies the above-mentioned requirements, it is becoming common to use a stepping motor for the focus lens group of the inner focus lens system. The stepping motor rotates in complete synchronization with the stepping pulse output from the lens control microcomputer and the like, and the stepping angle per pulse is constant, so it has high speed response, stopping accuracy, and position accuracy. It is possible to obtain
[0010]
Further, when using a stepping motor, the rotation angle with respect to the number of stepping pulses is constant, so that the stepping pulse can be used as an incremental encoder as it is, and there is an advantage that a special position encoder need not be added. is there.
[0011]
As described above, when the stepping motor is used to drive the focus lens to perform the zooming operation while maintaining the in-focus state, the locus information shown in FIG. It is necessary to read the locus information in accordance with the position or moving speed of the zoom lens and move the focus lens based on the information.
[0012]
FIG. 3 is a diagram for explaining an example of a trajectory tracking method previously proposed by the present applicant. In the figure, z0, z1, z2, ..., z11 indicate zoom lens positions, and a0, a1, a2, ..., a11 and b0, b1, b2, ..., b11 are These are representative trajectories stored in the memory in the lens control microcomputer. Further, p0, p1, p2,..., P11 are trajectories calculated based on the two trajectories. The calculation formula of this locus is described below.
[0013]
p (n + 1) = │p (n) -a (n) │ / │b (n) -a (n) │ * │b (n + 1) -a (n + 1) │ + a (n ) --- (1)
[0014]
According to the equation (1), for example, in FIG. 3, when the focus lens is at p0, a ratio of p0 internally dividing the line segment b0-a0 is obtained, and the line segment b1-a1 is internally divided according to this ratio. P1. From the positional difference of p1 to p0 and the time required for the zoom lens to move from z0 to z1, the moving speed of the focus lens for maintaining the focus is known, and the focus lens is moved at the moving speed. If so, the cam trajectory can be traced while maintaining the in-focus state.
[0015]
However, in order not to cause blur in the tracking method, it is necessary to reset the value of the stepping pulse counter of the stepping motor to a specific value. In other words, if the value of the stepping pulse counter deviates, the cam locus information obtained from the coordinates of the combination of the magnification lens position and the focus lens position stored in the microcomputer cannot be read correctly. This is because it becomes impossible to trace accurately.
[0016]
Therefore, a method of resetting the stepping pulse counter by moving the focus lens to a predetermined position after turning on the power and before entering the normal lens control operation is often used. In this case, the predetermined position is generally set as a mounting position of a position detection photodiode incorporated in the lens, and the focus lens position where the output signal from the photodiode is changed is set as the reset position. Then, the focus lens is stopped and the value of the step pulse counter is set to the initial value determined by the balance adjustment of the optical system. At this time, the reason why the lens is temporarily stopped at the reset position is that the value of the stepping pulse counter is still changing in the lens driving state, so that the counter reset is ensured.
[0017]
By the way, the normal zoom lens is driven / stopped according to the information of the zoom switch operated by the photographer, but when the zoom lens reaches the zoom end determined by the balance adjustment like the focus lens. The zoom lens should be stopped regardless of the operating state of the zoom switch. If the zoom switch is pushed in the tele direction and the zoom lens position has reached z0 in FIG. If the information is not stored, blur will occur, and when the variable power lens is driven to the super tele area, it will thrust into its mechanical end, that is, the mechanical end. This is because there is a risk of breakage.
[0018]
[Problems to be solved by the invention]
However, according to the lens control device in the conventional video camera, since the control is performed in synchronization with the vertical synchronization period, there are the following drawbacks.
[0019]
For example, since the detection of the zoom end is performed once in one vertical synchronization period, depending on the driving speed of the zoom lens, there is a case where the zoom lens stops after the telephoto end is pushed beyond the tele end.
[0020]
As the lens becomes higher in magnification, the inclination of the cam locus on the tele side shown in FIG. 2 becomes steep, and a focus lens for maintaining the focus with respect to the movement of several pulses of the variable power lens. The amount of movement corresponds to several tens of pulses. Therefore, when the variable power lens is projected to the super tele area as described above, the focus lens must be moved further in an infinite direction and at a high speed in order to maintain the in-focus state.
[0021]
However, the movable range of the focus lens in the infinite direction is up to the software infinite end position determined by the tele end focusing position on the trajectory of FIGS. The movement to the area is generally prohibited because there is a risk that the focus lens will hit the mechanical end.
[0022]
Therefore, when the variable magnification lens is greatly projected at the extreme telephoto end, the focal point may exist in an infinite direction further than the infinite end position, and at this time, it is impossible to focus. was there.
[0023]
In the reset of the stepping motor stepping pulse counter described in the above-mentioned conventional example, since the stop control of the focus lens is performed once in one vertical synchronization period, the output signal of the photodiode changes. In some cases, the focus lens stops at a position shifted from the position of the sagged lens, and the stepping pulse counter is reset at that position. At this time, a deviation occurs between the focus lens position recognized in the microcomputer and the actual focus lens position. When the amount of deviation is large, the amount of blur increases especially during zooming operation.
[0024]
[Means for solving problems]
The present invention has been made for the purpose of solving the above-mentioned problems, and is characterized by a variable power lens for performing a variable power operation, and movement of a focal plane by the movement of the variable power lens. A focus lens for correction, an actuator such as a stepping motor for moving the zoom lens and the focus lens in parallel with the optical axis, and driving the focus lens according to the movement of the zoom lens, The lens control apparatus includes a control unit that generates an interrupt according to the movement of the zoom lens by the actuator in the minimum movement unit and can detect arrival of the zoom lens at the end of the moving range.
[0026]
[Action]
As a result, it is possible to stop the lens in the minimum movement unit.For example, when the zoom lens enters the ultra-tele area or the focus lens position deviates from the reset position, the step pulse counter is reset. It is possible to prevent inconveniences such as breakage during zooming, and it is possible to prevent the risk of breakage and displacement due to blurring during zooming or when the lens hits the mechanical end.
[0027]
【Example】
Hereinafter, the configuration and operation of the lens control device according to the present invention will be described in detail with reference to a first embodiment shown in the drawings.
[0028]
<< First Example >>
FIG. 1 is a block diagram of the first embodiment showing the characteristics of the lens control apparatus according to the present invention. In the following description, it is assumed that the driving actuator is a stepping motor for both the variable power lens and the focus lens.
[0029]
In FIG. 1, reference numerals 101, 102, 115, 103, and 104 denote elements constituting an inner focus type lens system, respectively, a fixed front lens group and a second lens group (variable magnification) for performing variable magnification. Lens), a diaphragm, a fixed third lens group, and a fourth lens group (focusing lens) having both a function of competition and a function of focusing. These optical components themselves are similar to the lens system of FIG.
[0030]
Reference numerals 105 and 107 denote switches for detecting that the variable power lens 102 and the focus competition lens 104 are at the reference positions, respectively. In this embodiment, these switches are incorporated in the lens driving systems together with the photosensors 106 and 108, respectively. ing. The switches 105 and 107 are fixed to the lens groups 102 and 104, respectively, and move integrally as the lens groups 102 and 104 move in parallel with the optical axis.
[0031]
Then, in the movable region of each lens group, the operation of whether or not to block the output light of the photosensors 106 and 108 is performed with the middle vicinity as a boundary. Depending on whether the output light is blocked or not, the light detection unit of the photosensors 106 and 108 outputs a signal of 1 to 0, and the lens changes its position as the reference position where the output signal changes. Whether or not it is at the reference position can be detected.
[0032]
116 is a diaphragm encoder for detecting the state of the diaphragm, 117 is an amplifier that amplifies the output signal of the diaphragm encoder 116, and 118 is a lens control micro computer (hereinafter referred to as a lens control microcomputer) 124 that outputs the output signal of the amplifier 117. This is a signal conversion circuit that converts the signal into a signal that can be read by the computer.
[0033]
119 is an image sensor such as a CCD, 120 is an amplifier or impedance converter, 121 is an AGC circuit that automatically controls the gain according to the output signal level of the image sensor, and 122 is a high-frequency component that changes from the video signal according to the focus state. A signal processing circuit for processing a video signal to perform AF processing based on a high-frequency component signal output from the bandpass filter, and a microcomputer for controlling driving of the lens It is.
[0034]
138 is a diaphragm control circuit for adjusting the state of the diaphragm 115 so as to keep the output level of the AGC circuit 121 constant, 139 is an amplifier for amplifying the output of the diaphragm control circuit 138, and 140 is for driving the diaphragm 115. The driver 115 is configured to control the diaphragm 115 by driving the amplifier 139 and the driver 140 based on the output of the diaphragm control circuit 138 so as to keep the video signal level constant.
[0035]
Reference numerals 125 and 128 denote drivers for outputting drive energy to the stepping motors 110 and 112, respectively, in accordance with drive instructions for the variable power lens 102 and the focus competition lens 104 output from the lens control microcomputer 124. Stepping motors for driving the variable power lens 102 and the focus competition lens 104, 111 and 114 are output shafts forming lead screws directly connected to the stepping motors 110 and 114, and 109 and 112 are outputs. The racks sandwiching the shafts 111 and 114 are rotated by the output shafts 111 and 114, so that these racks move in parallel with the optical axis, and the lens groups fixed to the racks are 102 and 104, respectively. Move.
[0036]
131 is a pull-up resistor group connected to various operation switches connected to the lens control microcomputer 124, 132 is a power source, 134 and 135 are zoom switches for moving the variable power lens 102 in the wide direction and the tele direction, respectively. Reference numerals 136 and 137 respectively denote focus switches for moving the focus lens 104 in an infinite direction and a close direction.
[0037]
The above-described zoom control 134, 135, zooming operation, focus switch 136, 137 manual focus operation, AF operation based on the output of the AF signal processing circuit 123, various lens initial setting operations, etc. It is controlled centrally by the control microcomputer 124.
[0038]
Next, driving control of a stepping motor for lens control will be described. The lens control microcomputer 124 determines the driving speeds of the zoom stepping motor 110 and the focus stepping motor 112 by program processing, and drives the zoom motor 110 through the control lines 127 and 130 as rotation frequency signals of the stepping motors. To the driver 125 for driving and the driver 128 for driving the focus motor 113.
[0039]
In addition, a drive / stop command for the motors 110 and 113 is sent to the drivers 125 and 128 through the control lines 143 and 144 and the rotation direction of each motor through the control lines 126 and 129, respectively.
[0040]
Further, the drive / stop signal and the rotation direction signal correspond to the state of the two switches 134 and 135 for the zoom motor, the state of the two switches 136 and 137 for the focus motor during the manual operation, and the microcomputer 124 during the AF. The Hi / Low control is performed in accordance with the driving direction command determined by the AF processing routine in the camera.
[0041]
The motor drivers 125 and 128 set the excitation phase of the four-phase stepping motor to forward rotation and reverse rotation according to the rotation direction signal of the motor, and according to the received rotation frequency signal, By outputting the excitation phase while changing the applied voltage (or current) of the excitation phase, the rotation direction and the rotation frequency of the motor are controlled. At the same time, every time the motor excitation phase changes by one pulse, a pulse signal is output to the lens control microcomputer 124 through the lines 141 and 142, and the lens control microcomputer 124 counts the pulse signal so that each stepping motor, that is, each lens. The amount of movement is detected.
[0042]
The motor drivers 125 and 128 turn on / off the output to each motor in response to a drive / stop command from the lens control microcomputer 124, but excite up to an excitation pattern (one-phase excitation pattern) that outputs a pulse signal. Until the phase advances, the output to the stepping motor is not turned OFF. That is, each motor does not stop except for the one-phase excitation pattern.
[0043]
5 and 6 are control flow charts for carrying out the present invention, which are processed by the lens control microcomputer 124. FIG. The flow chart shown in FIG. 5 is an interrupt processing routine, and this processing is executed when a 141 pulse signal from the motor driver is detected. That is, every time the zoom lens 102 moves by one pulse, an interrupt is applied, and the flow chart process shown in FIG. 5 is executed.
[0044]
FIG. 6 shows a subroutine process for performing the zooming operation, which is processed once by the lens control microcomputer 124 in one vertical synchronization period. Before the process of FIG. 6 is executed, an AF mode process for controlling automatic focus adjustment according to the focus voltage is performed.
[0045]
In FIG. 6, step 601 indicates the start of this subroutine. Step 602 is a process for determining whether or not the zoom operation is being performed. When neither of the zoom switches 134 and 135 is pressed, it is determined that the operation is stopped, and the process proceeds to step 618.
[0046]
If the tele switch 135 is pressed, the process proceeds to step 603 to determine whether or not the variable magnification lens 102 has reached the tele end. Here, Cz represents a stepping pulse counter for the variable power lens, which increases when moving in the tele direction and decreases while moving in the wide direction.
[0047]
Further, the counter value C tele at the tele end and the counter value C wide at the wide end are set to eigenvalues of each lens determined by the balance adjustment result of the optical system. In step 603, if Cz is equal to or greater than C tele, it is determined that the tele end has been reached ("Y"), and the processing from step 618 is performed. If Cz has not reached C tele at step 603, it is determined that the tele end has not been reached ("N"). At step 604, a forward rotation direction signal is output to the zoom driver 125 via the control line 126.
[0048]
On the other hand, if it is determined in step 602 that the wide switch 134 has been pressed, in step 605, the counter value Cz is compared with the counter value C wide at the wide end to determine whether the wide end has been reached. If Cz is equal to or smaller than C wide and it is determined that the variable magnification lens has reached the wide end, the process proceeds to step 618. If it has not reached the wide end, in step 606, the zoom driver 125 is processed. A reverse direction signal (wide direction) is output and processing from step 607 is performed.
[0049]
Step 607 is a process for determining whether or not the current zoom lens position is a zoom lens position (referred to as a boundary position) that possesses representative trajectory data stored in the lens control microcomputer 124. If it is not on the boundary, it is determined that the tracking locus cannot be calculated, and the flow proceeds to step 616 in order to maintain the moving direction and moving speed of the zoom lens and focus lens calculated previously.
[0050]
If it is determined in step 607 that the trajectory can be calculated ("Y") (if the zoom lens position is at z (n) on a certain boundary in FIG. 3), in step 608, the adjacent boundary obtained by the above equation (1). The upper follow-up focus lens position p (n + 1) is calculated.
[0051]
In step 609, the moving speed Vz of the variable power lens is calculated. The value of Vz is usually a constant speed. However, in the case of high-speed zoom or the like, if Vz is not reduced on the telephoto side, the moving speed of the focus lens for maintaining the in-focus will exceed the step-out limit speed. It will end up. In this embodiment, Vz is set to a constant value for simplicity, but the value of Vz is held in the lens control microcomputer 124 as a speed table with the variable magnification lens position as a variable so as to smoothly decelerate, and extracted from there. Vz may be determined.
[0052]
In step 610, the cam locus following focus speed Vf is calculated. Where Vf is the current position of the focus lens as p (n),
Vf = ((pn + 1) -p (n)) * Vz / [Delta] z
Given in. Here, Δz = | z (n + 1) −z (n) |.
[0053]
In step 611, it is determined whether Vf calculated in step 610 is 0. If Vf = 0, it is determined that there is no need to move the focus lens. Converts to a frequency signal for driving the motor. The actual motor drive pulse signal generates Hi / Low of the pulse signal output to the motor driver by timer interrupt processing different from the flow charts of FIGS. 5 and 6. In the conversion performed in step 617, A timer value for determining the timer interrupt processing cycle is determined. In step 619, a drive signal is output to the zoom motor driver 125 via the control line 143, and a stop signal is output to the focus motor driver 128 via the control line 142.
[0054]
If Vz ≠ 0 is determined in step 611, it is determined in step 612 whether Vz> 0. If “Yes”, a forward rotation signal is output to the focus motor driver 128 via the control line 129 in step 613. Then, the process proceeds to step 615. If “No” in step 612, a reverse rotation signal is output to the focus motor driver 128 via the control line 129 in step 614.
[0055]
In step 615, in the same manner as in step 617, a timer interruption period for determining each motor rotation frequency is calculated from the zoom speed Vz and the focus speed Vf.
[0056]
In step 616, a drive signal is output to the zoom motor driver 125 through the control line 143 and to the focus motor driver 128 through the control line 142.
[0057]
If it is determined in step 602 that the zoom is stopped, step 603 is determined that the zoom lens position is at the telephoto end, and step 605 is determined that the zoom position is at the wide end, the process proceeds to step 618 and the zoom motor driver 125 controls the zoom motor driver 125. A stop signal is output via line 143.
[0058]
Step 620 represents the end of the flow of FIG. 6, and returns to the main processing routine such as other AF processing.
[0059]
On the other hand, the zoom motor driver 125 outputs a pulse signal to the microcomputer 124 through the control line 141 every time the zoom lens moves one pulse by the processing routine of FIG. The lens control microcomputer 124 executes the interrupt processing routine shown in FIG. 5 each time the pulse of the control line 141 is detected.
[0060]
In FIG. 5, step 501 indicates the start of this interrupt processing. Whether the zoom motor is rotating in the forward rotation direction from the signal state of the control line 126 output to the zoom driver 125 at step 502 is reversed. Determine if it is rotating.
[0061]
If it is forward rotation (tele direction), the value of the stepping pulse counter Cz of the zoom motor is increased by 1 at step 503. If the rotation is reverse (in the wide direction), the value of Cz is decreased by 1 in step 504. This interrupt process is executed after the variable magnification lens has moved one pulse, so it is performed in order to match the amount of movement with the value of the stepping pulse counter Cz. In this way, Cz is monitored. The position of the variable magnification lens can be recognized simply by doing.
[0062]
Step 505 is a process for determining whether or not zooming is in progress. When both the zoom switches 134 and 135 are not pressed, it is determined that the operation is stopped, and a stop signal is output to the zoom motor driver 125 via the control line 143 at step 509. .
[0063]
When the tele switch 135 is pressed, it is determined in step 506 whether or not the zoom lens has reached the tele end. As described above, C tele is a step pulse counter value at the tele end (C wide is a counter value at the wide end).
[0064]
When it is determined at step 506 that the tele end has been reached, the routine proceeds to step 509, and when it is determined that the tele end has not been reached, the processing from step 508 is executed.
[0065]
On the other hand, if it is determined in step 505 that the wide switch 134 has been pressed, it is determined in step 507 whether or not the wide end has been reached. If “Yes”, step 509 is determined. Then, a drive signal is output to the zoom motor driver 125 through the control line 143.
[0066]
Step 510 is a process for permitting the next interrupt so that this interrupt routine can be executed when the zoom lens moves one pulse next time, and step 511 represents the end of this interrupt routine.
[0067]
As described above, the zoom lens can be stopped in the minimum movement unit by recognizing the zoom end by performing the interrupt processing of FIG. 5 for each drive of one pulse which is the minimum movement unit of the zoom lens. This eliminates the inconvenience that the zoom lens goes beyond the telephoto end and enters the super telephoto area. This makes it possible to overcome the disadvantage that the focal point exists in the ultra-infinite region beyond the infinite end of the focus and becomes impossible to focus.
[0068]
<< Second Embodiment >>
The detection accuracy of the zoom lens position and the focus lens position directly affects the trajectory tracking accuracy as described above in the description of the prior art and the problems of the invention.
[0069]
In this embodiment, taking a reset operation of a focus lens as an example, means for performing lens position detection with high accuracy will be described.
[0070]
FIG. 7 is a block diagram of a reset switch that operates the lens position counter, and is a shielding plate that moves along the optical axis with the lens along the optical path from the light emitting unit 701 to the light receiving unit 702 constituting the photosensor 108 (or 106). When 107 (or 105) is interrupted, the output signal of the light receiving portion 702 is at the Low level, and when not interrupted, it is at the Hi level.
[0071]
FIGS. 8 and 9 are flowcharts for explaining the reset operation of the lens position counter. In the illustrated example, the position counter reset operation of the focus lens 104 will be described. The reset can be used in the same manner.
[0072]
In FIG. 8, when the execution of the process is started at step 801, it is detected whether or not the power is turned on at step 802. If the power is not turned on, the process continues to stand by on the spot.
[0073]
When the power is turned on, the focus detection lens position detection counter Cf is cleared at step 803, and a reset flag is set at step 804.
[0074]
In step 805, it is confirmed whether or not the output signal of the photosensor 108 is at the Hi level. For example, when the boundary between the light shielding and the light transmission is approximately in the middle of the lens movable range, it can be determined from the state of the output signal of the photosensor 108 whether the boundary is closer to the current lens position or the infinite side.
[0075]
Taking FIG. 7 as an example, since the output signal of the photo sensor 108 is shielded from light, the focus competition lens 104 is positioned closer to the boundary than the focus competition lens 104. By moving to the infinite side, the change of the output signal of the photosensor 108 from Low to Hi can be obtained. First, when the output signal of the photosensor 108 is at the Hi level, the opposite is true.
[0076]
Therefore, the state of the output signal of the photo sensor 108 is confirmed at 805 in FIG. 8, and if it is Hi level, the focus competition lens 104 is moved in the closest direction at step 806 to obtain a boundary point.
[0077]
If 805 is recognized as Low, the focus lens 104 is moved to the infinite side at Step 807. Step 808 continues to wait until the reset flag is cleared. Here, the lens is driven by the lens control microcomputer 124 sending a rotation direction signal, a rotation frequency signal, and a drive command signal to the focus motor driver 128 via the control lines 129, 130, and 144, respectively.
[0078]
When the focus competition lens 104 moves, a pulse signal is output from the driver 128 to the lens control microcomputer 124 via the control line 142 every time the lens moves one pulse. The lens control microcomputer 124 executes the interrupt processing routine shown in FIG. 9 each time a pulse signal on the control line 142 is detected.
[0079]
In the flow chart shown in FIG. 9, the focus lens position counter Cf is matched with the number of stepping pulses of the stepping motor 113, the position of the reset switch during the reset operation is detected, and the focus lens is stopped. Here, FIG. 9 will be described.
[0080]
Step 901 indicates the start of this interrupt processing. In step 902, the moving direction of the focus lens is confirmed. If the focusing lens is moving in the closest direction, the focus lens position detection counter Cf is incremented by 1 in step 903.
[0081]
On the other hand, when moving in the infinite direction, the value of Cf is decreased by 1 in step 904. Step 905 determines whether or not the reset operation is in progress. If the reset flag = 1, the process proceeds to step 906, and if not, the process proceeds to step 911.
[0082]
If it is determined in step 905 that the reset operation is being performed, the moving direction of the focus lens is confirmed once again in step 906. Do. If it is still Hi, the boundary point has not been reached, and the routine proceeds to step 911.
[0083]
When the output of the photosensor 108 becomes low at step 907, the focus lens has reached the boundary point and is positioned above the reset switch position. At step 909, the reset flag is set to 0, and at step 910, the focus lens is set. Stop the lens. The lens is stopped by outputting a stop command signal to the focus motor driver 128 through the control line 144.
[0084]
If it is determined in step 906 that it is moving in the infinite direction, it is checked in step 908 whether the output signal of the photosensor 108 has become Hi. If it is still Low, the boundary point has not been reached, so go to Step 911. If not, the processing from Step 909 is performed assuming that the focus lens has reached the boundary point. In step 911, the next interrupt is permitted, and in 912, the present interrupt processing routine is exited.
[0085]
Accordingly, in step 808 in FIG. 8, it is assumed that the focus lens is stopped at the reset switch position by interrupt processing, and when the reset flag is cleared, in step 809, the focus lens position detection counter Cf is preliminarily set. A numerical value indicating the position of the reset switch that has been measured or determined (for example, the number of stepping pulses of the stepping motor 113 that represents the reset switch position measured from the origin determined by the optical design within the focus lens movement range) Substitute the value converted into.
[0086]
When the processing of step 809 is completed, the resetting of the lens position detection counter is completed, and the normal photographing operation of step 810 is executed. In step 811, it is confirmed that shooting has been completed and the power supply has been cut off, and the processing returns to step 802.
[0087]
As explained above, the lens position detection counter can be reset with high accuracy no matter how fast the lens movement speed is during the reset operation by the stop control in the minimum movement unit of the lens using interrupt. The reset operation time can be shortened while maintaining the reset operation accuracy.
[0088]
【The invention's effect】
As described above, according to the lens control device of the present invention, it is possible to perform stop control in the minimum movement unit of the lens by using an interrupt in the microcomputer, so that the variable magnification lens can move beyond the telephoto end to super telephoto. It is possible to reliably prevent inconveniences such as entering the area or resetting the lens position detection counter where the lens position is different from the reset switch position, and this contributes particularly to improvement of focusing performance during zooming operation.
[0089]
Further, it is possible to perform a high-speed reset operation without deterioration of the reset operation accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram of a lens control device according to the present invention.
FIG. 2 is a characteristic diagram showing a change of a focus surface that changes in accordance with a zooming operation in an inner focus lens.
FIG. 3 is a diagram for explaining processing for calculating a trajectory other than the stored trajectory from a trajectory indicating a change in focus surface according to a scaling operation stored in the lens control microcomputer;
FIG. 4 is a diagram illustrating a lens configuration of an inner focus lens.
FIG. 5 is a flowchart showing interrupt processing for performing stop control of the zoom lens.
FIG. 6 is a flowchart for explaining a zooming operation in the lens control device of the present invention.
FIG. 7 is a perspective view for explaining a configuration of a switch for detecting a reset position of a lens.
FIG. 8 is a flowchart showing a process of resetting the focus lens in the second embodiment of the present invention.
FIG. 9 is a flowchart showing an interrupt process for detecting and resetting the focus lens reset position in the second embodiment of the present invention.

Claims (1)

A zoom lens for zooming operation,
A focus lens for correcting movement of the focal plane due to movement of the zoom lens;
An actuator such as a stepping motor for moving the zoom lens and the focus lens in parallel with the optical axis;
The focus lens is driven in accordance with the movement of the variable power lens, and an interrupt is generated in accordance with the movement of the minimum movement unit of the variable power lens by the actuator, to the end of the moving range of the variable power lens. Control means capable of detecting arrival;
A lens control device comprising:

Images