JP5294549B2 - Imaging apparatus and control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of speedily moving a diaphragm blade on the small diaphragm side and also capable of restraining vibration of the diaphragm blade on the open side. <P>SOLUTION: According to a difference between the actual position and target position of the diaphragm blade, a drive control signal representing an amount by which the diaphragm blade is driven is output. By inputting the drive control signal to a band variable LPF, a drive signal for the diaphragm blade is generated. The band variable LPF, differs in a frequency band to be blocked according to the position of the diaphragm blade. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to feedback control, and more particularly to control of diaphragm blades of an imaging apparatus.

  2. Description of the Related Art In recent years, automatic exposure adjustment has come to be equipped as standard in imaging devices such as video cameras. In general, there are many diaphragm devices having a so-called meter-type simple drive unit, which is often used in meters such as a DC ammeter, as a diaphragm device used in an imaging unit of a home video camera. This meter-type drive unit adjusts the current flowing through the coil, thereby repelling between the magnetic field generated by the coil and the magnetic field of the permanent magnet, or an attractive force, and an elastic member such as a spring connected to the aperture blade The aperture value is adjusted to a desired value by adjusting the balance of the magnitude of the force and the biasing force.

  In the case of a control mechanism having such two inertia systems, a vibration resonance point may appear due to friction generated between the diaphragm blades and the ground plane, the balance state described above, or the like. This vibration resonance point is likely to occur when the diaphragm is on the open side.

  If a minute vibration occurs at this vibration resonance point, there will be no noticeable change in the amount of light, but if the microphone is built into the imaging device, the noise caused by the vibration will be picked up and recorded by the microphone. May end up.

To solve this problem, generally, the oscillation state is suppressed by reducing the gain of the entire servo system of the diaphragm device (see, for example, Patent Document 1), or by applying an appropriate filter, the resonance is damped and vibration is caused. There has been a method of removing or reducing components (see, for example, Patent Document 2). As another method, there is a method of calculating a vibration component by modeling a vibration system and removing the vibration component from an actual control signal (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-133303 JP 2000-078861 A JP 2004-254322 A

  However, in the case of the control system described above, when the vibration resonance point is located in the vicinity of the control band of the diaphragm blade, there are the following problems when the conventional method as described above is used.

  First, when the gain of the entire servo system is lowered, the diaphragm blades cannot be moved smoothly, and there is a problem that the amount of light reaching the image sensor changes intermittently. The small aperture side is particularly noticeable because the sensitivity of the aperture is high.

  Moreover, if the resonance point is attenuated by applying an appropriate filter, not only will the light intensity change intermittently, but there will be less room for oscillation as a servo system, and it may easily fall into an oscillation phenomenon. .

  Furthermore, it is not practical to calculate the vibration component by modeling and remove the vibration component from the actual control signal, taking into account variations in the characteristics of the members of the device, etc. The amount of computation of the microcomputer inside increases.

In order to solve the above-described problems, a control device according to the present invention is configured to move a driving unit, a diaphragm blade driven by the driving unit, a position detection unit that detects a position of the diaphragm blade, and the diaphragm blade. A drive that outputs a drive control signal representing the amount of drive of the diaphragm blades based on the difference between the target position of the diaphragm blades, which is the target position, and the position of the diaphragm blades obtained by the position detection means Amount calculation means, filter means for cutting off a frequency band set from the drive control signal obtained by the drive amount calculation means and outputting a drive signal, and band for setting a frequency band to be cut off by the filter means And when the diaphragm blades are located on the open side, the band control means sets a wider frequency band to cut off than when the diaphragm blades are located on the small diaphragm side, and the drive unit , And drives in response to a driving signal outputted from said filter means.

  According to the present invention, the driven body can be quickly moved to the target value, and the driven body can be prevented from oscillating in the vicinity of the target position.

  Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram schematically showing the configuration of an imaging apparatus according to an embodiment of the present invention. Although not shown, the imaging apparatus includes a microphone that picks up sound and a recording unit that records the sound picked up by the microphone.

  Reference numeral 101 denotes a first fixed lens group. Reference numeral 102 denotes a variable power lens group for performing a variable power operation, which is hereinafter referred to as a zoom lens. Reference numeral 103 denotes a diaphragm blade as a driven body, and reference numeral 104 denotes a second fixed lens group. Reference numeral 105 denotes a focus / compensation lens group having a focus adjustment function and a function of correcting the movement of the focal plane due to zooming, and is hereinafter referred to as a focus lens.

  Reference numeral 110 denotes a driving unit for the diaphragm blade 103. By adjusting a current flowing through the coil, a repulsion generated between the magnetic field generated by the coil and the magnetic field of the permanent magnet, or an attractive force, a spring connected to the diaphragm blade, and the like The aperture value is adjusted to a desired value by adjusting the balance of the magnitude of the force with the urging force of the elastic member. A driver 111 receives a drive signal from the camera microcomputer 114 and drives the drive unit 110. An encoder 112 detects the position of the aperture blade 103 and outputs it as a position signal. The position signal output from the encoder 112 is amplified to a predetermined magnification by the amplifier 113 and then taken into the camera microcomputer 114. The camera microcomputer 114 is a microcomputer that controls the entire imaging apparatus including the control of the diaphragm blades.

  While the incident light from the subject passes through the lens groups 101, 102, 104, and 105, the amount of light is adjusted by the diaphragm blade 103 and forms an image on the image sensor 106.

  The image sensor 106 is a photoelectric conversion element such as a CCD or CMOS sensor, and has a function of converting a subject image into a video signal composed of an electrical signal. The camera signal processing circuit 107 performs predetermined analog video signal processing and AGC (auto gain control) processing on the video signal output from the image sensor 106. In the AGC processing, the gain is controlled so that the integrated value of the video signal subjected to the analog video signal processing is at the same level as a predetermined gain control reference signal. The maximum value of this gain is limited by the maximum gain control reference signal in order to suppress noise at low illumination. The video luminance signal Y obtained from the video signal obtained by the camera signal processing circuit 107 is subjected to detection processing by the detector 115, is A / D converted, and is taken into the camera microcomputer 114. This video luminance signal Y represents the luminance data of the video signal.

  The camera signal processing circuit 107 also has a function of converting a video signal into a video signal suitable for the monitor device 108 or the recording device 109. The recording device 109 records the subject image on a recording medium such as a magnetic tape, an optical disk, or a semiconductor memory, and the monitor device 108 displays the subject image on an electronic viewfinder, a liquid crystal panel, or the like using a video signal.

  Next, the configuration of the camera microcomputer 114 will be described with reference to FIG.

  In FIG. 2, reference numeral 201 denotes an A / D converter, which converts the detection signal X output from the detector 115 into a digital signal. A first comparison unit 202 compares the digital signal output from 201 with the exposure reference signal set by the reference value setting unit 203 and outputs a signal representing the difference. The exposure reference signal represents the target value of the luminance of the video signal. By this processing, the difference between the luminance value actually obtained from the video signal and the target value is obtained.

  Reference numeral 204 denotes second comparison means, which compares the output signal of the first comparison means with the position signal of the diaphragm blade 103 amplified by the amplifier 113 and digitized by the A / D converter 208, and the comparison result. Is used to read out and output the target position of the diaphragm blade 103 from unshown table data.

  Then, the difference between the signal read and output from the table data by the second comparing means 204 and the position signal amplified by the amplifier 113 and digitized by the A / D converter 208 is obtained by the adding means. This position signal is a signal representing the position of the diaphragm blade 103 as described above. If a minute vibration is generated in the diaphragm blade 103, the signal reflects this minute vibration. From this addition result, a drive control signal indicating the drive amount of the diaphragm blades necessary to fill the difference between the luminance value actually obtained from the video signal and the target value is obtained.

  A servo filter 205 determines the characteristics of the feedback system, and is a so-called PID calculation means for calculating differentiation, integration, and proportional gain with respect to the drive control signal. Reference numeral 206 denotes a band variable LPF (low pass filter) to which the output signal of the servo filter 205 is input. The band variable LPF 206 is controlled by a band control processing unit 207 in the cutoff frequency, that is, the frequency band to be cut off.

  The output signal of the band-variable LPF 206 is converted into an analog signal inside the camera microcomputer 114, subjected to pulse width modulation (PWM) to generate a drive signal, and supplied to the drive unit 110 via the driver circuit 111. Then, the diaphragm blade 103 is driven.

Reference numeral 208 denotes an A / D converter, which digitizes the position signal amplified by the amplifier 113 and adds second comparison means 204, addition means positioned between the second comparison means and the servo filter 205 , and band control processing. Input to means 207.

  Here, it has been described that the cut-off frequency of the band variable LPF 206 is controlled by the band control processing unit 207. The processing performed by the band control processing unit 207 will be described with reference to the flowchart of FIG.

  In step S101, the band control processing means 207 determines whether the current position of the diaphragm blade 103 obtained via the A / D converter 208 is located on the open side with respect to the threshold value x1, and positions the open position on the open side. If so, the process proceeds to step S102, and if not, the process proceeds to step S103.

  In step S102, the variable fmin of the cutoff frequency of the band variable LPF 206 is set to a predetermined value f2.

  In step S103, the band control processing means 207 determines whether the current position of the aperture blade 103 is located on the small aperture side from the threshold value x2, and if it is located on the small aperture side, the process proceeds to step S104. If it is not located on the small aperture side, the process proceeds to step S105.

  In step S104, the variable fmin of the cutoff frequency of the band variable LPF 206 is set to a predetermined value f1. Here, the relationship among the above x1, x2, f1, and f2 will be described with reference to FIG.

  In FIG. 4, the position of the diaphragm blade 103 is set on the horizontal axis, and the variable fmin of the cutoff frequency of the band variable LPF 206 is set on the vertical axis. In FIG. 4, the position of the diaphragm blade 103 approaches the open state as it goes to the right, and the variable fmin of the cutoff frequency becomes a value representing the high frequency as it goes upward.

  If the position of the diaphragm blade 103 is located on the open side with respect to the threshold value x1, f2 is set as the variable fmin. If the position of the diaphragm blade 103 is located on the diaphragm side with respect to the threshold value x2, f1 is set as the variable fmin. Is done. Here, x1 is located on the open side with respect to x2, and f1 has a higher frequency than f2.

Returning to FIG. 3, in step S <b> 105, the band control processing unit 207 obtains a cutoff frequency variable fmin by the following calculation.
fmin = (f1−f2) / (x1−x2) × (x−x1) + f2
Here, x indicates the current position of the diaphragm blade 103 detected by the encoder 112.

  This is shown in FIG. As the position of the aperture blade 103 changes from the open side threshold value x1 to the small aperture side x2, the cutoff frequency variable fmin changes from f2 to f1 in a linear function manner on the high frequency side. Recognize. In the present embodiment, the position of the diaphragm blade 103 and the variable fmin of the cutoff frequency in step S105 are shown as linear functions, but they may be exponential or logarithmic. Further, instead of the calculation in step S105, the position of the diaphragm blade 103 and the variable fmin of the cutoff frequency may be obtained using table data.

  If the process in step S102, step S104, or step S105 is completed, the process proceeds to step S106.

  In step S106, it is determined whether the current target position of the diaphragm blade 103 set by the second comparison unit 204 matches the previous target position of the diaphragm blade 103. If not, the process proceeds to step S110. .

  In step S110, the bandwidth control processing unit 207 resets the time count t1, and proceeds to step S111.

  Returning to step S106, if the current target position of the diaphragm blade 103 set by the second comparison means 204 matches the previous target position of the diaphragm blade 103, the process proceeds to step S107. Note that it may be configured to determine whether the current target position and the previous target position are within a predetermined range, for example, whether they are within one step.

  In step S107, the bandwidth control processing unit 207 increments the time counter t1. That is, the value of the time counter t1 increases as the time during which the target position of the aperture blade 103 has not changed is longer.

  In step S108, the bandwidth control processing unit 207 determines whether a predetermined time has elapsed from the value of the time counter t1, and proceeds to step S109 if the predetermined time has elapsed, otherwise proceeds to step S111.

  In step S109, the band control processing unit 207 sets a variable fmin as the minimum value of the cutoff frequency of the band variable LPF 206.

  In step S111, the band control processing unit 208 sets f1 as a minimum value of the cutoff frequency of the band variable LPF 206, or a predetermined value that is higher than f1.

  Thus, if it is determined that the target position of the diaphragm blade 103 does not change in a certain period, the variable fmin corresponding to the position of the diaphragm blade is set as the minimum value of the cutoff frequency of the band variable LPF 206 in step S109. Is set.

  Since the aperture blade is more likely to resonate on the open side, the variable fmin has a wider frequency band cut off by the band-variable LPF 206 on the open side, that is, the frequency band that can be passed is narrowed to provide a highly stable drive system. If the oscillation of the diaphragm blade 103 can be suppressed, it is possible to suppress the recording of noise caused by the vibration by the microphone provided in the imaging device. Further, the variable fmin has a narrower frequency band cut off by the band variable LPF 206 toward the smaller aperture side, that is, a wider frequency band that can be passed, and a drive system with high responsiveness. On the small aperture side where the sensitivity of the aperture is higher than that on the open side, the phenomenon that the light quantity changes intermittently by increasing the response of the aperture device is suppressed.

  On the other hand, if it is not determined that the target position of the diaphragm blade 103 has not changed in a certain period, a frequency of f1 or higher is set as the minimum value of the cutoff frequency of the band variable LPF 206 in step S111.

  The fact that the target position of the diaphragm blade 103 does not change for a certain period of time can be considered that there is a high possibility that the diaphragm blade 103 still leaves a distance to the target position. Therefore, the frequency band blocked by the band variable LPF 206 is narrowed, that is, the frequency band that can be passed is made wider than that in step S105, and the response of the drive system of the diaphragm blade 103 is improved. In this state, the stability of the drive system against oscillation decreases, but there is no problem because the diaphragm blade 103 can be regarded as still being away from the target position.

  As described above, in this embodiment, priority is given to the response of the drive system compared to the open side so that the change in the amount of light by the diaphragm blades is smooth on the small aperture side, and noise due to resonance of the aperture blades is suppressed on the open side. Therefore, priority is given to the stability of the drive system compared to the small aperture side.

  Note that x1, x2, f1, f2, and the predetermined time used for the determination in step S108 are experimentally appropriate values set according to the purpose of use of the imaging device and the actual specifications of each component. Good.

It is a block diagram which shows the structure of the imaging device concerning embodiment of this invention. It is a block diagram which shows the internal structure of the camera microcomputer of the imaging device of FIG. It is a flowchart which shows the process of the band control process means of the camera microcomputer of FIG. It is a figure which shows the relationship between the position of an aperture blade, and the minimum value of a cutoff frequency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 1st fixed lens group 102 Zoom lens 103 Diaphragm blade 104 2nd fixed lens group 105 Focus lens 106 Image pick-up element 107 Camera signal processing circuit 108 Monitor apparatus 109 Recording apparatus 110 Drive part 111 Driver 112 Encoder 113 Amplifier 114 Camera microcomputer 115 Detector 201, 208 A / D converter 202 First comparison means 203 Reference set value 204 Second comparison means 205 Servo filter 206 Band variable LPF
207 Band control processing means

Claims (7)

A drive unit;
A diaphragm blade driven by the drive unit;
Position detecting means for detecting the position of the diaphragm blade;
The driving amount of the diaphragm blade is expressed based on the difference between the target position of the diaphragm blade, which is a target position when the diaphragm blade is moved, and the position of the diaphragm blade obtained by the position detecting means. Drive amount calculation means for outputting a drive control signal;
Filter means for cutting off a frequency band set from the drive control signal obtained by the drive amount calculation means and outputting a drive signal;
Band control means for setting a frequency band to be cut off by the filter means, and
The band control means, when the diaphragm blades are located on the open side, set a wider frequency band to cut off compared to when located on the small diaphragm side,
The image pickup apparatus, wherein the drive unit is driven in accordance with a drive signal output from the filter unit.   The imaging apparatus according to claim 1, wherein the band control unit sets the frequency band to be cut off according to a position of the diaphragm blade if the difference is within a predetermined range.   The band control means sets the cut-off frequency band according to the position of the diaphragm blade if the difference is within a predetermined range for a predetermined time. Item 3. The imaging device according to Item 2. Having imaging means for imaging a subject;
The drive amount calculation means outputs the drive control signal based on a signal related to the brightness of the subject based on a signal output from the imaging means and a position of the diaphragm blade obtained by the position detection means. The imaging apparatus according to any one of claims 1 to 3, wherein   5. The drive amount calculation unit outputs the drive control signal that fills a difference between a luminance value of the subject and a luminance target value based on a signal output from the imaging unit. Imaging device.   The drive unit adjusts a current flowing through the coil to thereby generate a repulsion between the magnetic field generated by the coil and the magnetic field of the permanent magnet, or an attractive force, and an urging force of the elastic member connected to the diaphragm blade. The imaging apparatus according to claim 1, wherein the stop position of the aperture blade is set by adjusting a balance of the magnitude of force. A control method for an imaging apparatus having a driving unit and a diaphragm blade driven by the driving unit,
A position detecting step for detecting the position of the diaphragm blade;
The driving amount of the diaphragm blade is expressed based on the difference between the target position of the diaphragm blade that is a target position when the diaphragm blade is moved and the position of the diaphragm blade obtained in the position detection step. A drive amount calculation step for outputting a drive control signal;
A filter step of cutting a frequency band set from the drive control signal obtained in the drive amount calculation step and outputting a drive signal for driving the drive unit;
A band control step for setting a frequency band to be cut off in the filter step, and
In the band control step, when the aperture blade is located on the open side, a frequency band to be cut off is set wider than when the aperture blade is located on the small aperture side.

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