JP2006065176A - Photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that sound and vibration are produced at wobbling operation time in performing AF control by using a linear motor for the driving of a focus lens. <P>SOLUTION: By setting the target reaching time of wobbling speed when driving the focus lens by using the linear motor, speed is calculated from the set time and the amplitude of wobbling so as to prevent high-speed driving that the vibration is produced more than necessary. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lens drive control device for driving a lens group such as a photographing lens in a camera / video camera or a projection lens in a video projector.

  In this type of conventional lens drive control device, a motor such as a DC motor or a stepping motor is often used as a lens drive actuator.

  4 is a longitudinal sectional view showing a lens barrel of a conventional zoom lens for a video camera, and FIG. 5 is a longitudinal sectional view taken along line AA of FIG. 4 and 5, reference numerals 101a to 101d denote photographing lenses housed in a fixed cylinder 102, 103, 104a and 104b guide bars arranged in parallel to the optical axis 105 in the fixed cylinder 102, and 106 as a drive source. A lens holding frame 111 that holds the photographing lens 101b, which is a DC motor and is a variator lens for changing the angle of view, includes an output shaft 106a, a gear train 107, a screw rod 108 having a screw groove 108a, and a pressing spring 109. It is moved in the optical axis direction along the guide rod 103 via the ball 110 pressed and engaged with the screw groove 108a with the pressing force of. Reference numeral 112 denotes a stepping motor as a drive source, which holds the photographing lens 101d for focus position change and focusing accompanying a change in angle of view, and a lens holding unit in which the screw member 113 is integrally assembled with the sleeve portion 114a. The frame 114 is moved in the optical axis direction along the guide rods 104a and 104b via a screw member 113 that is screwed into the screw portion of the output shaft 112a. Reference numeral 118 denotes an IG meter that drives the aperture unit.

  In recent years, in cameras and video cameras, miniaturization has progressed, and it has become necessary to reduce the volume and weight while maintaining the same or higher functions. As one means for this purpose, a magnet is disposed on the outer periphery of the lens holding frame that holds the lens, and a coil and a yoke are disposed on the outer periphery of the magnet to form a voice coil motor. There is a system for driving the holding frame in the optical axis direction. In this system, the voice coil motor as a compact lens driving actuator is realized by making the voice coil central axis and the optical axis substantially coincide with each other.

  FIG. 6 shows an application example of the voice coil motor, and FIG. 7 is a longitudinal section taken along line BB of FIG. 6 and 7, the same parts as those in FIGS. A coil 116 wound around a yoke 117a and a bobbin 119 is disposed on the outer periphery of the lens holding frame 111 that holds the lenses 101b1 to 101b3, and a yoke 117b and a magnet 115 bonded to the yoke 116 are disposed outside the coil 116 so as to face the yoke 117a. The yokes 117a and 117b and the magnet 115 are attached to the fixed cylinder 102. The lens holding frame 111 is held by two guide rods 103a and 103b parallel to the optical axis 105 so as to be movable in the optical axis direction.

  Since the magnet 115 is magnetized as shown in the drawing, a magnetic field is formed in the radial direction between the yokes 117a and 117b. Since the coil 116 exists between the yokes 117a and 117b and is wound in the circumferential direction, when a current is passed through the coil 116, a driving force in the optical axis direction is generated, and the bobbin 119 is integrally formed. The lens holding frame 111 and the lens groups 101b1 to 101b3 are driven in the optical axis direction.

  6 and 7 show a type in which the magnet 115 is fixed and the coil 116 moves, whereas FIG. 8 shows a type in which the coil is fixed and the magnet moves. In the magnet moving type of FIG. 8, a magnet 115 magnetized in the radial direction is bonded to the outer periphery of the lens holding frame 111 that holds the lenses 101b1 to 101b3, and an appropriate gap is provided between the magnet 115 and the outer periphery. A coil 116 is provided which is bonded to the inner periphery of the yokes 117a and 117b and wound in the circumferential direction. Since the lens holding frame 111 is held by the two guide rods 103a and 103b so as to be movable in the optical axis direction, when a current is passed through the coil 116, the lens holding frame 111 moves in the optical axis direction.

  FIG. 9 shows an example in which a video lens system is formed using the voice coil motor described above. In this figure, the lens group 101b of the variator lens for zooming and the lens group 101d of the focus lens are used by the voice coil motor. This is a type in which the magnet moves.

  Since the video lens shown in FIG. 9 is a so-called rear focus lens that performs focusing by a lens group closer to the image plane than the variator lens group, the positional relationship between the variator lens group and the focus lens group depends on the subject distance. Change. This is shown in FIG.

  In FIG. 10, the vertical axis represents the focus lens position, the horizontal axis represents the variator lens position, and the subject distance is a parameter, and the cam locus that each lens group should follow is shown. Accordingly, each voice coil motor needs to determine the speed and direction in which the lens group should move based on various information provided in the system, and keep the focused state. These systems are described in detail below.

  In FIG. 9, encoders 121 and 122 for detecting absolute positions are attached to face the variator lens group 101b and the focus lens group 101d, respectively. These encoders 121 and 122 are of a type that uses a linear type volume or an electrode on which a gray code pattern is formed with a brush, a light emitting element such as iRED that moves with a lens holding frame, and a photoelectric conversion element such as PSD. A type that performs the above-mentioned is conceivable.

  Outputs from the encoders 121 and 122 are read by the respective reading circuits 123 and 124 and sent to the CPU 125. The video signal from the CCD 126 is processed in the peak detection circuit 127, the peak value of the luminance signal is extracted, and sent to the CPU 125 as information on the current focus state.

  FIG. 11A is a focus detection signal diagram in which the vertical axis represents the output value So of the peak detection circuit 127 and the horizontal axis represents the focus lens position. As shown in the figure, the approximate defocus amount is detected by the peak value So of the luminance signal. Based on this information and information from the ROM 128 having information on the cam locus shown in FIG. 12 as data, each voice coil motor (hereinafter abbreviated as VCM) as a lens driving means in the CPU 125. The current value or the waveform to be passed through the coils 129 and 130 is determined, and the current flows through the coils 129 and 130 through the respective drivers 131 and 132. With the above-described system, the variator lens group 101b and the focus lens group 101d can maintain a positional relationship that is always in focus.

  Next, a system from the state where the variator lens group 101b is fixed and in focus is brought into focus, that is, an autofocus (AF) system will be described.

  The CPU 125 is configured to perform AF operation control processing according to the flowchart shown in FIG. 13, for example.

  First, when this process is started (step S1301), control is performed to finely drive the focus lens group 101d by a wobbling operation, and the AF evaluation signal as described above is captured to check whether the current focus is in focus. Is determined (step S1302). If it is determined that the image is blurred, it is further determined whether the pin is a front pin or a rear pin.

  Next, based on the result of the wobbling operation in step S1302, it is determined whether or not the focus lens group 101d is currently in focus (step S1303).

  If it is determined in step S1303 that the in-focus state is obtained, control is performed to stop the focus lens group 101d, and the process proceeds to a restart monitoring process routine in step S1308 and later described. On the other hand, if it is determined in step S1303 that the subject is not in focus, the process proceeds to a hill-climbing operation processing routine after step S1304 described later.

  In the hill-climbing operation processing routine, first, according to the result of the blur determined in step S1302, that is, the result of determining whether the focus is the front pin or the rear pin, the control of the hill-climbing operation for driving the focus lens group 101d in the direction of the blur is performed. It executes (step S1304).

  Next, it is determined whether or not the in-focus point, that is, the vertex of the AF evaluation signal has been exceeded (step S1305). If the result of the determination is that the vertex has not been exceeded, the process returns to step S1304 to control the hill climbing operation. To continue.

  If the result of determination in step S1305 is that the vertex has been exceeded, drive control of the focus lens group 101d is performed so that the AF evaluation signal returns to that vertex (step S1306).

  Then, it is determined whether or not the AF evaluation signal has reached the vertex (step S1307). If the determination result shows that the AF evaluation signal has not reached, the process returns to step S1306.

  If the AF evaluation signal has reached the apex as a result of the determination in step S1307, the process returns to step S1302. This is because the subject may change due to panning or the like during the operation of returning the AF evaluation signal to the apex, so if the AF evaluation signal reaches the apex, the current AF evaluation signal is surely This is because the process returns to step S1302 and the wobbling operation is performed again in order to determine whether or not the current position of the focus lens group 101d is in focus.

  On the other hand, in the restart monitoring processing routine, first, the signal level of the AF evaluation signal at the time of focusing is stored (step S1308).

  Next, it is determined whether or not the signal level of the current AF evaluation signal has changed compared to the signal level of the AF evaluation signal stored in step S1308 at the time of focusing (step S1309). For example, when the signal level fluctuates by a predetermined percentage or more with respect to the stored signal level, it is recognized that the subject has changed due to panning or the like, and “restart” is determined. If the fluctuation is less than the predetermined percentage, it is recognized that there is no change in the subject, and “non-restart” is determined.

  Then, based on the determination result of step S1309, it is determined whether it is “restart” or “non-restart” (step S1310). If it is “non-restart”, the focus lens group 101d is moved as it is. Control to stop is performed (step S1311), and the process returns to the restart determination process of step S1309. If it is “restart”, the process returns to step S1302, and the processing after step S1302, that is, the wobbling operation is performed again to determine the direction in which the focus lens group 101d is moved, and the like.

  By repeating the processes in steps S1302 to S1311 as described above, the focus lens group 101d is driven so that the in-focus state is constantly maintained.

FIG. C. It is a block diagram regarding the drive system of M. When a target value (sensor voltage value) at which the lens is to be located is given, the sensor voltage value passes through the phase compensation filter 21, and V.V. C. It is converted into a current i by a converter 22 with a resistance value (1 / R) determined by the coil of M. Based on this current i, the calculation unit 23 calculates a thrust f for driving the lens, and the V.V. C. The lens is driven by M24, and the lens position is measured by an encoder (sensor) 25 at every sampling period (Tsec), and a voltage is output. By subtracting the voltage obtained by multiplying the voltage output by the loop gain K by the calculating unit 26 from the target value by the subtracting unit 20, the lens position can approach the target value.
JP-A-8-154196

  However, in the above conventional example, V.V. C. The gain K of the M control system is constant regardless of the position of the lens in the optical axis direction, but the magnetic field that the coil crosses is not always evenly distributed, but rather is often non-uniform. . In particular, it is difficult to keep the magnetic field uniform due to factors such as leakage flux at the yoke end in the closed magnetic type and at the magnet end in the open magnetic type.

  14 shows a V.V. of the open magnetic type shown in FIG. C. M is an example in which the magnetic flux density on the surface in the thickness direction of the magnet is measured, and the horizontal axis indicates the magnet thickness and the vertical axis indicates the magnetic flux density. As is apparent from the figure, the magnetic flux density drops at the magnet end. Further, the magnetic flux density is wobbling in the central portion of the thickness. C. If a constant current is passed through the M coil, a constant thrust cannot be obtained regardless of the position of the lens on the optical axis. That is, V. C. Even when the gain K is constant in performing the M control, the actual V.P. C. The gain K ′ as M is not constant, and the stability to the lens target position varies depending on the position on the optical axis. In particular, at the time of starting and stopping, when driving at high speed due to its characteristics and mechanical rigidity, vibration and sound are likely to occur, and vibration and sound increase as the speed increases.

  On the other hand, since the VCM drive can be driven at high speed, it is used for the purpose of high-speed and high-performance AF.

  In particular, since the wobbling operation in AF is periodically driven and stopped, both sound and vibration are likely to occur.

  The present invention has been made paying attention to the above points, and by performing focus lens drive using a linear motor, it is possible to perform AF control according to drive characteristics by setting the target time of wobbling speed to reach the target. An object of the present invention is to provide a photographing apparatus that performs the above.

  The present invention is an imaging apparatus having the following configuration.

  In a photographing apparatus that detects a focus signal corresponding to the degree of focus from the video signal and moves the focus adjustment lens based on the detection signal to perform focus adjustment, a direction determination operation for detecting a focus direction is performed. An imaging device characterized in that a speed is obtained from a predetermined arrival time that can be set in advance, and solves the problems such as the generation of sound and vibration described above by changing the predetermined arrival time according to lens characteristics. It is.

  According to the present invention, V.I. C. When performing AF with M, the sound and vibration associated with high-speed driving can be suppressed by setting the target arrival time during wobbling, and by changing the setting according to the driving characteristics of the lens, variations in lens characteristics can be avoided. Therefore, it is possible to provide an imaging apparatus that realizes AF with high speed and high performance and reduced sound and vibration.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  1 is a drawing that best represents the features of the present invention. C. It is a figure which shows the example which driven the lens group using M. In FIG. 1, 1a to 1d are zoom lens groups, 1b is a variator lens group for zooming, and 1d is a focus lens group. Reference numerals 2a and 2b denote lens holding frames for holding the zoom lens group 1b and the focus lens group 1d. Reference numerals 3a and 3b denote magnets, which are bonded to the outer peripheral portions of the lens holding frames 2a and 2b in the radial direction. ing. Reference numerals 4a and 4b denote coils wound in the circumferential direction, and are bonded to the lens barrel 5 with appropriate gaps provided on the outer circumferences of the magnets 3a and 3b.

  The lens holding frames 2a and 2b are held so as to be movable in the optical axis direction by two guide rods 6a to 6d arranged in parallel with the optical axis. Reference numerals 7 and 8 denote encoders for detecting the absolute positions of the variator lens group 1b and the focus lens group 1d. Outputs from the encoders 7 and 8 are read by the respective reading circuits 9 and 10 and sent to the CPU 11 as lens control means. Sent. The video signal from the CCD 12 is processed in the peak detection circuit 13, the peak value of the luminance signal is extracted, and sent to the CPU 11 as information on the current in-focus state.

  Reference numerals 14 and 15 denote drivers, to which an applied voltage level or voltage waveform determined based on an in-focus state signal, an absolute position signal, or the like in the CPU 11 is applied, and a current is passed through the coils 4a and 4b. In addition, a frequency detector 16, a phase comparator 17, and a reference frequency oscillator 18 are provided to obtain a focusing signal for the autofocus system. Reference numeral 20 denotes a rewritable storage means such as an E2 PROM.

  The object of the invention is The purpose is to drive C and M as fast as possible and to suppress sound and vibration as much as possible.

  FIG. 2 is a diagram showing the wobbling speed and the read timing for AF. 2A is a diagram illustrating wobbling at a high speed, and FIG. 2B is a diagram illustrating wobbling at a lower speed than that in FIG. From this figure, it can be seen that the slope a is faster and the establishment time is shorter. However, since the establishment time required for performing AF may be in time for the AF signal readout timing, it is not necessary to drive at a higher speed than necessary. Rather, sound and vibration due to the high speed driving are not required. Occurrence becomes a problem. Since FIG. 2A has a high speed, the inclination is higher than that in FIG. In this case, it can be easily understood that the sound and vibration generated at the time of activation are larger than those in FIG. Therefore, in the present invention, by generating the speed at the time of wobbling from the time required for the imaging device to establish the wobbling and the time to reach the target position, generation of sound and vibration due to driving at a higher speed than necessary The purpose is to suppress.

Target arrival time: Mtime
Speed: Wobv
Drive amount: Range
age,
Wobv = Range / Mtime
It becomes. The speed is determined as a function of the target arrival time.

  FIG. 3 shows the flow. In 301, it is determined whether or not AF is a wobbling operation. When in the wobbling mode, the target arrival time is read in 302, the wobbling amplitude is obtained from the degree of aperture or blur in 303, the driving speed is calculated in 304, and the focus in 305 Drive.

  Since the establishment time varies depending on the lens, it is necessary to drive at the highest possible speed and to establish it in the shortest possible time considering the readout timing of the AF signal. Therefore, depending on the driving characteristics of the focus lens, the setting of the target arrival time is shortened for those that generate less noise and vibration, and the setting for longer occurrences of sound and vibration is set longer. It can be suppressed.

  Further, when the driving amount increases, the speed may exceed a predetermined command cycle or AF read time. In that case, it is needless to say that it can be avoided by delaying the period of the AF readout timing or driving at high speed.

Illustration of the description of the first embodiment Illustration of the description of the first embodiment Flow chart of embodiment 1 Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Illustration of conventional example Conventional flowchart Illustration of conventional example

Explanation of symbols

1a to 1d Zoom lens groups 2a and 2b Lens holding frames 3a and 3b Magnets 4a and 4b Coils 6a to 6d Guide rods 7 and 8 Encoders 9 and 10 Reading circuit 11 CPU
12 CCD
13 Peak detection circuit 14, 15 Driver 16 Frequency detector 17 Phase comparator 18 Reference frequency oscillator 20 Rewriteable storage means

Claims (4)

  In a photographing apparatus that detects a focus signal corresponding to the degree of focus from a video signal and moves the focus adjustment lens based on the detection signal to perform focus adjustment, a predetermined speed at which a focus determination operation can be set in advance. An imaging device characterized in that it is obtained from a target arrival time.   The photographing apparatus according to claim 1, wherein the focusing lens is a focusing lens using a linear motor.   The photographing apparatus according to claim 1, wherein the predetermined target arrival time is changed from driving characteristics of the focus adjustment lens.   2. The photographing apparatus according to claim 1, wherein the predetermined target arrival time is set longer as the vibration or sound generated when the focus adjustment lens is driven is larger.

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