Image-capturing apparatus and driving method of optical system

An image-capturing apparatus for controlling a drive system for an optical system corresponding to the position of an operation unit includes a motor for driving a control target of the drive system, a driver for the motor, position detecting means for detecting the position of the operation unit, position generating means for generating the output corresponding to the position of the operating unit with a limited movable range by configuring an initialization value and maximum and minimum values of integrated displacement by the output of the position detecting means, and controlling means for controlling the motor via the driver so as to drive the control target corresponding to the position generating output of the operating unit.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application JP 2004-250732 filed in the Japanese Patent Office on Aug. 30, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image-capturing apparatus that controls a lens drive system during image capturing, and a driving method of an optical system.

2. Description of the Related Art

Recently, an open-loop control system using a stepping motor as an actuator has been widely used in camera drive systems. Such a control mechanism has an enhanced positioning resolution, achieving positional accuracies on the order of a few μm.

When a lens is moved with a motor in this camera drive system, a method has been known in that an operation controller detects a state of an operation member and the motor is controlled corresponding to the state and an integrated value of the state. For example, there have been provided a lever ring in that the operation member returns to the midpoint (see Japanese Unexamined Patent Application Publication No. 59-216111) and a rotary ring operation member (see Japanese Unexamined Patent Application Publication No. 63-177118). In order to have high accuracy in lens positional control and high resolution in operation, a ring has been required for controlling by such an operation controller.

On the other hand, in a lens mechanism in that a ring is mechanically connected to a lens and the lens advances or retreats in a lens barrel (mainly used for business purposes), the rotational angle of the ring is limited corresponding to the maximum advanced position or the maximum retracted position of the lens, and because the rotational angle of the ring is brought into one-to-one correspondence with the lens position, it is easy to intuitively operate this mechanism.

An example of a preexisting lens position determining method requiring the positional detection with high resolution similarly to the operation ring includes the following methods: a first is a method for obtaining an absolute position using a hall sensor and a potentiometer; a second is a method for obtaining a relative position from a reference position by combining a reset sensor with an MR (magneto resistance effect) sensor using the reset sensor for detecting the reference position and an FG (frequency generator) pulse counter (see Japanese Unexamined Patent Application Publication No. 59-216111); and a third is a method for detecting a plurality of reference positions using two or three reset sensors.

SUMMARY OF THE INVENTION

When the above-mentioned lens mechanism in that the ring is mechanically connected to the lens is applied to an inner focus lens, because of a complicated configuration, a ring movable range may not be brought into one-to-one correspondence with a lens movable range, so it has been difficult to intuitively comprehend when a control target (inner focus lens) arrives at a movable end.

In the relative position sensing for detecting the rotation magnitude of the operating ring with a displacement sensor, such as a two-phase pulse encoder, shown in the second method for obtaining the lens position, if the rotational angle of the operating ring is limited, there is a problem that the ring position cannot be comprehended directly after activation. Hence, for detecting the relative displacement using the state of the sensor directly after the activation as a reference, the ring is in a state capable of infinitely rotating. Thus, the ring movable range may not be brought into one-to-one correspondence with the lens movable range, so it has been difficult to intuitively comprehend when a control target (lens, for example) arrives at the movable end.

It may be possible for the configuration to detect the rotation magnitude of the operating ring by the output of the absolute position sensor, such as the potentiometer, shown in the first method for obtaining the lens position; however, the absolute position sensor generally has restrictions, such as low resolution and susceptibleness to noise, so the first method has been unsuitable for moving the lens smoothly or finely.

In the case where a plurality of the reset sensors are used shown in the third method for obtaining the lens position, the resolution has been reduced due to mechanical restrictions, such as the arrangement of the plurality of the reset sensors.

It is desirable to provide an image-capturing apparatus and a driving method of an optical system, which are capable of smoothly driving a control target by easily comprehending the arrival of the control target at the movable end.

According to an embodiment of the present invention, there is provided an image-capturing apparatus including a motor for driving a control target of the drive system; a driver for the motor; relative position detecting means for detecting the position of the operation unit; position generating means for generating the output corresponding to the position of the operating unit with a limited movable range by configuring an initialization value and maximum and minimum values of integrated displacement by the output of the position detecting means; and controlling means for controlling the motor via the driver so as to drive the control target corresponding to the generated position output of the operating unit.

Thereby, in the operating unit with a physically limited rotational angle (movable range), by configuring an initialization value and maximum and minimum values of integrated displacement of the position detecting means, the movable end of the operating unit is allowed to agree with the movable end of the control target.

The value of a storage area storing the position generating output in the position generating means herein is assumed to be an initialization value from the position detecting means, and after the initialization , the value of the storage area is integrated based on the signal from the position detecting means.

Furthermore, on the basis of the value of the storage area in the position generating means, when the integrated value is detected to be smaller or larger than the limited movable range of the operation unit, the minimum value or the maximum value of the integrated output is renewed corresponding to the movable range.

Thereby, positions of members of the optical system in the image-capturing apparatus, such as the zoom lens, the focus lens, and the iris, are controlled.

According to the embodiment of the present invention, there is provided a driving method for driving an optical system including the steps of detecting the position of the operation unit; generating the output corresponding to the position of the operating unit with a limited movable range by configuring an initialization value and maximum and minimum values of integrated displacement by the output of the detecting position step; controlling a motor via a driver so as to drive a control target corresponding to the generated position output of the operating unit; and driving the control target of the drive system with the motor.

Thereby, in the operating unit with a physically limited rotational angle (movable range), by configuring an initialization value and maximum and minimum values of integrated displacement of the position detecting means, the movable end of the operating unit is allowed to agree with the movable end of the control target.

The value of a storage area storing the position generating output in the position generating step herein is assumed to be an initialization value from the position detecting step, and after the initialization assuming, the value of the storage area is integrated based on the signal from the position detecting step.

Furthermore, on the basis of the value of the storage area in the position generating step, when the integrated value is detected to be smaller or larger than the limited movable range of the operation unit, the minimum value or the maximum value of the integrated output is renewed corresponding to the movable range.

Thereby, positions of members of the optical system in the image-capturing apparatus, such as the zoom lens, the focus lens, and the iris, are controlled.

According to the embodiment, in the operating ring with a physically limited rotational angle, using a displacement sensor for detecting a relative displacement, such as an MR encoder and a pulse encoder, a ring easy to be intuitively operated with a limited rotational angle can be configured. When a user rotates the ring to the movable end, continuous control is possible by allowing the movable end of the ring to agree with the movable end of the control target without discontinuous operation of the control target.

Thus, according to the embodiment, with the ring with controlled variables easy to be intuitively recognized because of a limited rotational angle, a lens can be manually operated finely and smoothly. Moreover, even when the ring is rotated during the image-capturing apparatus is de-energized, on start up, the rotating angle of the ring can be detected by allowing the movable end of the ring to agree with movable end of the control target.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a block diagram of an image-capturing apparatus according to an embodiment, showing the outline of the image-capturing apparatus.

Referring toFIG. 1, an image-capturing lens/iris block1enables an iris12to be exposed to an object lens, and enables a focus lens13to be focused. The image-capturing lens/iris block1also includes a lens casing for accommodating a zoom lens11therein.

An image-capturing element2is arranged in an optical axial direction of the image-capturing lens/iris block1, and an image signal photo-electrically converted by the image-capturing element2is converted into digital image data by an A/D converter15after being sample-held at a predetermined timing by a S/H circuit14in a S/H-A/D block3.

This digital image data is amplified by an amplifier circuit16in a camera signal processing block4to a level capable of signal-processing. The amplified digital image data is processed into luminous and chrominance signals by a luminous/chrominance signal processing circuit17so as to be outputted in an image-output unit8or a video-recording unit9.

From the digital image data amplified to an level capable of signal-processing, a luminous signal level and a high-frequency component of the luminous signal are detected by a luminous-signal detector circuit18, and exposure control is performed in accordance with this luminous signal level by an automatic exposure controller23′ in a camera control block5; focusing control is performed in accordance with the high-frequency component of the luminous signal by the automatic focusing controller23.

That is, based on an exposure control signal from the automatic exposure controller23′, exposure adjustment of the iris12, photo-electric conversion timing from a timing generating circuit7to the image-capturing element2, and an amplifier level of the amplifier circuit16are controlled, respectively.

Based on a focusing control signal from the automatic focusing controller23, the position of the focus lens13is controlled by a lens controller19and a lens drive unit20.

When the ring is operated by a user in a user interface control block6, a predetermined relative displacement is detected from a displacement detector21, as will be described later. The relative displacement output from the displacement detector21is supplied to a ring position generator22, which produces a ring position output by configuring an initial value, and the maximum and minimum values of integrated displacement values from the relative displacement output.

This ring position output is supplied to the lens controller19in the camera control block5, which produces a lens control signal based on the ring position output. This lens control signal is fed to the lens drive unit20, which drives the focus lens13and the zoom lens11corresponding to the lens control signal.

FIG. 2is a drawing of the lens driving by the ring rotational position generating unit, showing a lens drive system with the operating ring.

Referring toFIG. 2, the rotational angle of the ring10is limited within a movable range of approximately 0° to 90°.

The upper end of the ring is assumed to 0° and the lower end 90°, for the sake of convenience in description. When the ring10is rotated by a user operation, the rotating shaft of a rotary MR encoder24is rotated via a gear following the ring10.

The output of the MR encoder24is processed in the displacement detector21. Since the output of the MR encoder24is produced in a form of two-phase sine waves31and32(FIG. 3), the displacement detector21detects the displacement and the displacing direction from the voltage output with the continuous linear line segments in relation to the angle, based on the each phase voltage outputs and the phase relationship. Because changes in the output of the MR encoder24are increased even by the slight rotation of the ring10, the displacement detector21can detect the magnitude of the rotation with high resolution.

If the encoder displacement detected by the displacement detector21is denoted by ΔR; and the ring displacement by Δθ, the relationship between both the values is given by Numerical Formula 1.
Δθ=ΔR×α,(Numerical Formula 1)
where α is a constant; Δθ is the output of the displacement detector21.

The operation of the lens drive configured as described above will be described below.

FIG. 5is a PAD (problem analysis diagram) of the operation of the lens drive, showing the operation of microcomputers in the user interface control block6and the camera control block5.

Referring toFIG. 5, the initialization is first determined whether it is completed or not (Step S1). When the initialization is not completed at Step S1, storage area A denoted by numeral28is initialized (Step S2) with regarding the predetermined output (45°, for example) from the displacement detector21as the initial value; 0° is stored in storage area B denoted by numeral28(Step S3); and 90° is stored in storage area C denoted by numeral28(Step S4) so as to complete the initialization (Step S1). Specifically, when the value corresponding to the rotational angle of the ring10is generated in the ring position generator22, storage area A denoted by numeral28exists in the ring position generator22, so that the integrated value of displacement corresponding to the rotational angle of the ring10is stored. In a case where storage area A denoted by numeral28is not fixed, for example, right after power activation, an initialization assuming unit25of the ring position generator22regards the predetermined value (between 0° and 90°, 45°, for example) detected in the displacement detector21as the initial value so as to initialize storage area A denoted by numeral28with this rotational angle; 0° is stored in storage area B denoted by numeral28; and 90° is stored in storage area C denoted by numeral28.

When the initialization is completed at Step S1, the output of the displacement detector is added to the ring position regarded as the initial value in storage area A denoted by numeral28(Step S5). Specifically, the rotational angle regarded as the initial value in the initialization assuming unit25of the ring position generator22at Step S2is assumed to be 45°, for example. Because the physical angle of the ring is not known at this time, the value of storage area A does not agree with the practical physical angle of the ring10. However, the displacement of storage area A denoted by numeral28is adjusted by the above-mentioned α so as to become 90° at both ends. When the initialization is completed at Step S1, the rotational angle of the ring10from this point is calculated using the output of the displacement detector21. For example, when the ring10is rotated by 0.5°, the displacement detector21produces a rotational angle of 0.5°, so that an integrated value output unit26of the ring position generator22adds 0.5° to 45° of storage area A denoted by numeral28so as to output an integrated value of 45.5°. Similarly hereinafter, the integrated value output unit26of the ring position generator22generates the ring position by adding the output of the displacement detector21to the value of storage area A denoted by numeral28.

As described above, since the practical physical angle of the ring10does not agree with the value of storage area A denoted by numeral28, storage area A denoted by numeral28may have a value beyond the range of 0° to 90°. Thus, using storage areas B and C denoted by numeral28in the ring position generator22, the following processes are performed.

At Step S3, the upper end angle is stored in storage area B denoted by numeral28; and at Step S4, the lower end angle is stored in storage area C denoted by numeral28. In an initial state, storage area B=0°; and storage area C=90°.

If the value of storage area A denoted by numeral28becomes smaller than the value of storage area B denoted by numeral28(Step S6), it is regarded that the value of storage area B denoted by numeral28=the value of storage area A denoted by numeral28(Step S7), so that the value is renewed by regarding that the value of storage area C denoted by numeral28=the value of storage area A denoted by numeral28+90° (Step S8). Specifically, when the value of storage area A denoted by numeral28becomes smaller than 0° beyond the range 0° to 90, an integrated value max/min update unit27of the ring position generator22renews the value so as to regard 0° as the minimum value and regard 90° as the maximum value of storage area A respectively.

If the value of storage area A denoted by numeral28becomes larger than the value of storage area C denoted by numeral28(Step S9), it is regarded that the value of storage area C denoted by numeral28=the value of storage area A denoted by numeral28(Step S10), so that the value is renewed by regarding that the value of storage area B denoted by numeral28=the value of storage area A−90° (Step S11). Specifically, when the value of storage area A denoted by numeral28becomes larger than 90° beyond the range 0° to 90°, the integrated value max/min update unit27of the ring position generator22renews the value so as to regard 90° as the maximum value and regard 0° as the minimum value of storage area A respectively.

By performing this process, when the ring10is rotated to the movable end, the ring10can agree with the movable end of the control target (lens).

FIG. 6is a drawing showing the initial state.

In the initial state ofFIG. 6, the value, which is within the range 0° to 90°, 45° for example, of storage area A denoted by numeral62corresponding to a ring physical position61is regarded as an initialization value so as to initialize storage area A, so that 0° is stored in storage area B denoted by numeral63; and 90° is stored in storage area C denoted by numeral64. At this time, a lens position65of a lens66is located at an intermediate position50between an optical wide end0and an optical telescopic end100, corresponding to 45° between 0° and 90°.

FIG. 7is a drawing showing a state that the lens is moved in accordance with the rotation of the ring.

Referring toFIG. 7, when the ring is rotated, the value corresponding to a ring physical position71is added to 45° of storage area A denoted by numeral72so that the value 72.9° is stored. At this time, a lens position75of a lens76is located at an intermediate position81between the optical wide end0and the optical telescopic end100, corresponding to 72.9° between 0° of storage area B denoted by numeral73and 90° of storage area C denoted by numeral74.

FIG. 8is a drawing showing a state that the value of storage area A becomes beyond 90°.

Referring toFIG. 8, when the ring is rotated toward the lower end so that the value of storage area A denoted by numeral82corresponding to a ring physical position81becomes a value of 105.7° larger than 90° beyond the range of 0° to 90°, a lens position85of a lens86is located at the optical telescopic end100, corresponding to 105.7° larger than 90° beyond the range of 0° to 90°. At this time, the value is renewed so as to regard 90° as the maximum value of storage area C as denoted by numeral84and regard 0° as the minimum value of storage area A as denoted by numeral83.

Although not shown, when the value of storage area A is reduced smaller than 0°, since the state becomes reverse to that ofFIG. 8, the value is renewed so as to be reversed toFIG. 8.

In such a manner, by repeating the renewal of the maximum and minimum values of storage area A, the physical angle of the ring agrees with the value of storage area A, so that the movable end of the ring agrees with movable end of the lens.

FIG. 9is a drawing of a state that the movable end of the ring agrees with movable end of the lens.

Referring toFIG. 9, when the ring is rotated to the lowermost end and the value of storage area A denoted by numeral92corresponding to a ring physical position91becomes the maximum 121.3° larger than 90° beyond the range of 0° to 90°, a lens position95of a lens96is located at the optical telescopic end100, corresponding to 121.3° larger than 90° beyond the range of 0° to 90°. At this time, the value is renewed so as to regard 90° as the maximum value and regard 0° as the minimum value of storage area A respectively.

The lens controller19produces a control value (Step S12) based on values of storage areas A, B, and C in the ring position generator22; the lens drive unit20moves the lens to the corresponding position (Step S13). When one position of the lens movable end corresponds to value 0 and the other position corresponds to value 100 for the sake of convenience in description, the lens position L (0≦L≦100) is given by Numerical Formula 2.
L=(100−0)×(the value of storage areaA−the value of storage areaB)/(the value of storage areaC−the value of storage areaB)  (Numerical Formula 2)

In a zoom lens, for example, it is assumed that the wide end corresponds to value 0 and the telescopic end corresponds to value 100, alternatively, that the wide end corresponds to value 100 and the telescopic end corresponds to value 0. In a focus lens, it is assumed that the far end corresponds to value 0 and the near end corresponds to value 100, alternatively, that the far end corresponds to value 100 and the near end corresponds to value 0. Providing a selecting unit for selecting these alternative correspondences enables the relationship between the rotational direction of the ring10and the movement direction of the lens30to be selected by user's preference.

Moreover, the ring position generator22may monitor the output of the displacement detector21so as to detect whether the value of displacement discontinuously skips or not, and the value may be determined to skip when the displacement becomes discontinuous.

When the displacement becomes discontinuous, the initialization processing is again performed, and the ring position generator22completes the initialization at Step S1by configuring the rotational angle detected by the displacement detector21at Step S2as the initial position.

In addition, if the displacement does not become discontinuous, the lens drive at Step S13is continued.

The ring position generator22according to the embodiment is not limited to the lens drive control described above; alternatively, it may be applied to the control of iris drive unit20′ which will be described later.

In this case, only the lens controller19and the lens drive unit20, which are shown inFIG. 2, are replaced to an iris controller19′ and an iris drive unit20′, respectively; a lens drive motor29and the lens30are also replaced to an iris drive motor and an iris, respectively, and the other configurations may be the same. However, in the lenses shown inFIG. 1, the control signal supplied to the lens controller19from the automatic focusing controller23is replaced to the control signal supplied to an iris controller19′ from the automatic exposure controller23′ for the iris drive20′.

The operation of the iris drive mentioned above will be described.

The iris controller19′ produces a control value based on the ring position outputted from the above-mentioned ring position generator22′; the iris drive unit20′ moves the iris to the corresponding open/close position. Supposing that one open/close position of the iris movable end corresponds to value 0 and the other open/close position corresponds to value 100, for the sake of convenience in description, the iris open/close position L (0≦L≦100) is given by Numerical Formula 2 mentioned above. In this case, the control target is only replaced from the lens to the iris and the calculation and the control method are the same as those shown inFIG. 2and a displacement detector21′ performs in the manner described with respect to the displacement detector21.

FIG. 10is a drawing of the MR encoder.

When a detection subject polarized to an MR detection element101moves, the MR encoder shown inFIG. 10detects changes in position of the detection subject by the resistance changes due to the magneto resistance effect of the MR detection element101.

The sensor is not limited to the above-mentioned MR encoder and other sensors may also be used.

For example, as a modification, a pulse encoder having two-phase pulse outputs41and42shown inFIG. 4may also be used instead of the MR sensor as a displacement sensor.

Control examples of the lens drive system and the iris drive system have been described above; however, the control is not limited to those systems and other control targets driven by motors may be obviously applied.

The control may be widely incorporated to not only the rotating drive but also other operations linearly driven by a linear stepping motor. In this case, a liner encoder may be used instead of the rotary encoder by incorporating a mechanism for converting the ring rotation into linear movement.

The drive target may be applied to other optical members other than the lens.