JP5825765B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method therefor, and more particularly to aperture control of the imaging apparatus.

  In the conventional imaging apparatus, when the focal length is changed from the wide end to the tele side, the F value is also constant if the aperture diameter is constant except on the aperture opening side. In addition, on the wide open side, the F value is decreased by operating from the wide end to the tele side. As disclosed in Patent Document 1, in order to prevent flare and spherical aberration, The aperture diameter is monotonously decreased according to the drop. In practice, in order to realize this operation, as shown in FIG. 5A, a maximum aperture diameter is provided for each focal length to limit the aperture diameter.

JP-A-8-256288

  However, as a result of obtaining a lens having a small size, high magnification, and high resolution, it is necessary to move more lens groups than the conventional lens. In order to keep the F value constant when the focal length is changed from the wide side to the tele side, the aperture diameter of the aperture is changed according to the focal length at all aperture positions as shown in FIG. 5B. Must. In particular, at the F value near the open end, when the focal length is changed from the wide end to the tele side, first, the aperture diameter of the diaphragm is increased in order to keep the F value constant, and the focal length is further moved to the tele side. As in the prior art, it is necessary to reduce the aperture diameter in accordance with the drop of the F value. That is, conventionally, the maximum value of the aperture diameter can be calculated by monotonically decreasing the aperture diameter, but when the focal length is changed from the wide end to the tele side as described above, the F value at the wide end is maintained. For this purpose, it is necessary to once increase the maximum value of the aperture diameter, which complicates aperture control.

  Also, even if an attempt is made to open the aperture diameter from the open end at the wide end in order to keep the F value constant, the mechanical end that comes into contact with the aperture when the aperture reaches the maximum aperture diameter is close to the open end at the wide end. It is difficult to keep the F value constant at the mechanical end. That is, in order not to hit the mechanical end, it is necessary to increase the maximum aperture diameter of the diaphragm, and the lens cannot be reduced in size.

  The present invention has been made in view of the above problems, and even in a configuration in which the aperture diameter must be larger than the wide end in accordance with the change in the focal length in order to keep the F value constant, the image quality is deteriorated. The object is to prevent and to make the aperture control simple.

In order to achieve the above object, an imaging apparatus of the present invention includes a diaphragm unit that controls the amount of incident light according to the size of an aperture, a diaphragm driving unit that operates the diaphragm unit, and at least three or more lens groups. A photographic lens; lens driving means for driving the photographic lens so that at least three or more lens groups included in the photographic lens move in the optical axis direction when changing a focal length; Control means for controlling the lens driving means, and in order to satisfy the minimum F value when the focal length is at the wide end, at a part of the focal length, at the wide end corresponding to the minimum F value. An imaging apparatus in which the aperture diameter of the aperture means needs to be larger than the aperture diameter of the aperture means, and the control means takes a maximum value of the aperture diameter of the aperture means used during shooting. Focal length when there is the aperture diameter of the diaphragm means in said wide end corresponding to the minimum F value regardless of the focal length if less than the predetermined focal length the is part of the focal distance or more, the time of shooting When the focal length is equal to or greater than the predetermined focal length, the focal length becomes smaller as it approaches the tele end within a range equal to or smaller than the aperture diameter of the diaphragm at the wide end corresponding to the minimum F value. To do.

  According to the present invention, it is possible to prevent image quality deterioration and simplify the aperture control even in a configuration in which the aperture aperture diameter must be larger than the wide end in accordance with the change in focal length in order to keep the F value constant. it can.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention. FIG. 4 is a diagram illustrating the trajectories of four lenses with respect to the zoom operation of the imaging apparatus in FIG. 1. FIG. 2 is a diagram illustrating a maximum value of a diaphragm aperture diameter with respect to a focal length of the imaging apparatus in FIG. 1. It is a flowchart which shows the flow of a calculation process of the maximum value of the aperture opening diameter with respect to a focal distance. (A) is the figure which showed the maximum value of the aperture opening diameter with respect to the conventional focal distance, (b) is the figure which showed the aperture opening diameter according to each F value with respect to the conventional focal distance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to an embodiment of the present invention.

  In FIG. 1, 100 is a fixed lens group on the foremost side of the imaging lens of the subject, 101 is a zoom lens group for adjusting the zoom position, 103 is a shift lens group for correcting camera shake, and 104 is for focusing the subject. This is a focus lens group. In the present embodiment, each lens group is obtained by classifying a plurality of lenses for each main application, and a single lens group is also referred to as a lens group. These lens groups are collectively referred to as a photographing lens. A diaphragm mechanism 102 controls the amount of incident light.

  Reference numeral 110 denotes a stepping motor for operating the zoom lens 101, which is driven by the zoom lens driver 120. The zoom lens driver 120 is connected to the microcomputer 150. Reference numeral 111 denotes an IG meter that drives the aperture mechanism 102 and is driven by an IG meter driver 121. The IG meter driver 121 is connected to the microcomputer 150.

  Reference numeral 112 denotes a hall sensor for detecting the size of the aperture diameter of the diaphragm mechanism 102, and is connected to the microcomputer 150 via a hall amplifier (hole AMP) 126. A stepping motor 113 operates the shift lens 103 in the optical axis direction, and is driven by the second shift lens driver 122. The second shift lens driver 122 is connected to the microcomputer 150.

  Reference numeral 114 denotes a magnetic motor that moves the shift lens 103 in a direction perpendicular to the optical axis in order to correct camera shake, and is driven by the first shift lens driver 123. The first shift lens driver 123 is connected to the microcomputer 150.

  Reference numeral 115 denotes a hall sensor for detecting the position in the direction perpendicular to the optical axis of the shift lens 103, and is connected to the microcomputer 150 via a hall amplifier (hole AMP) 125. Reference numeral 116 denotes a stepping motor for operating the focus lens, which is operated by the focus lens driver 124. The focus lens driver 124 is connected to the microcomputer 150.

  As described above, in the illustrated imaging apparatus, at least three or more lens groups including the zoom lens 101 are moved in the optical axis direction according to the focal length by the lens driving means such as the stepping motor 110 and the magnetic motor 114.

  In the imaging apparatus of FIG. 1, 130 is an imaging element such as a CCD or CMOS that photoelectrically converts incident light, and 131 is a sample and hold apparatus that samples a signal photoelectrically converted by the imaging element 130. Reference numeral 132 denotes an analog-digital converter (A / D) that converts an analog image signal output from the sample hold device 131 into a digital signal. Reference numeral 133 denotes a camera signal processing device (DSP) having a control function of adding a synchronization signal and generating a standard television signal after performing processing such as color separation and color difference matrix after gamma correction.

  A microcomputer (hereinafter simply referred to as “microcomputer”) 150 is a CPU (Central Processing Unit) that performs calculations to operate each lens based on information from the DSP 133 and information such as an external switch.

  Next, the operation of each functional block in the microcomputer 150 and the lens operation will be described.

  The microcomputer 150 includes analog-to-digital converters (A / D) 140 and 144, a focus position calculator 141, a first shift lens position calculator 142, a second shift lens position calculator 143, and an aperture position. A calculation unit 145 and a zoom position calculation unit 146 are provided.

  First, when the zoom lever 161 is operated from the WIDE side to the TELE side, the operation signal is input to the zoom position calculation unit 146, and the zoom position calculation unit 146 calculates the zoom position. Information on the calculated zoom position is sent to the zoom lens driver 120. The zoom lens driver 120 drives the stepping motor 110, and the zoom lens 101 operates. If only the zoom lens 101 is operated, the focus position is shifted, so that the focus lens 104 and the shift lens 103 must be operated simultaneously. Therefore, zoom position information is sent from the zoom position calculation unit 146 to the focus position calculation unit 141 and the second shift lens position calculation unit 143, and the focus position and the shift lens position should be relative to the optical axis. Let's calculate whether it is good. Then, information on the focus target position is sent from the focus position calculation unit 141 to the focus lens driver 124, and information on the shift lens target position is sent from the second shift lens position calculation unit 143 to the second shift lens driver 122. Thereafter, the focus lens driver 124 operates the focus lens 104 by driving the stepping motor 116. The second shift lens driver 122 operates the shift lens 103 in the optical axis direction by driving the stepping motor 113. The zoom operation is established by the series of operations described above. FIG. 2 shows the trajectories of the four lenses for this zoom operation. In FIG. 2, the lens position is shown in the horizontal direction and the zoom position is shown in the vertical direction.

  Incidentally, the shift lens 103 is provided with a magnetic motor 114 that operates perpendicularly to the optical axis direction in addition to the stepping motor 113 that operates in the optical axis direction. This is because the gyro sensor 160 detects camera shake or shaking of the imaging apparatus body and sends a signal to the first shift lens position calculation unit 142. Upon receiving this signal, the first shift lens position calculation unit 142 instructs the first shift lens driver 123 to operate in a direction that cancels camera shake and shaking of the imaging apparatus. The first shift lens driver 123 drives the magnetic motor 114. As a result, the shift lens 103 operates in a direction perpendicular to the optical axis. The position of the shift lens 103 is detected by the hall sensor 115, and the detection signal is converted into a digital signal by the A / D 140 in the microcomputer 150 through the hall amplifier 125. The digital signal is input to the first shift lens position calculation unit 142 to form a feedback loop. This achieves stable operation when the shift lens 103 is driven in a direction perpendicular to the optical axis.

  Similarly, in the drive control of the aperture mechanism 102, the aperture position calculation unit 145 calculates the aperture diameter at which the appropriate exposure is obtained based on the exposure evaluation value detected by the DSP 133, and causes the IG meter driver 121 to operate the IG meter 111. Give an order. In response to this, the IG meter driver 121 outputs a drive signal to the IG meter 111, and the aperture mechanism 102 is operated by the IG meter 111 to change the aperture diameter. Then, the position of the member that moves with the change in the opening diameter is detected by the hall sensor 112, and the detection signal is converted into a digital signal by the A / D 144 in the microcomputer 150 through the hall amplifier 126. The converted digital signal is input to the aperture position calculator 145 to form a feedback loop. Thereby, stable operation of the diaphragm mechanism 102 is achieved.

  Next, a method for calculating the maximum value of the aperture diameter of the aperture on the open side will be described with reference to FIG.

  FIG. 3 is a diagram illustrating the maximum value of the aperture diameter with respect to the focal length of the imaging apparatus of FIG.

  In the figure, the horizontal axis represents the focal length or the zoom position, and the vertical axis represents the aperture diameter of the stop. A solid line is an ideal value of the maximum value of the aperture diameter for reducing image quality degradation due to flare and spherical aberration, and a dotted line is a design value of the maximum value of the actual aperture diameter based on the present invention.

  When the focal length is between the wide end A and the middle B, the maximum aperture diameter of the diaphragm is made constant at the aperture diameter Φ1 corresponding to the minimum F value at the wide end A as shown by the dotted line in the figure. That is, when the focal length at the time of shooting is less than a predetermined focal length, a predetermined value (aperture diameter Φ1) is used regardless of the focal length. Here, the focal length middle B (predetermined focal length) is equal to the maximum value of the actual aperture diameter at the wide end and the ideal value of the maximum aperture diameter to reduce image quality degradation due to flare and spherical aberration. Refers to the focal length.

  Next, when the focal length is between the middle B and the telephoto end C, the maximum aperture diameter is changed linearly from the aperture diameter Φ1 to the maximum aperture diameter Φ2 at the telephoto end C according to the focal length. Let That is, when the focal length at the time of shooting is equal to or greater than a predetermined focal length, the focal length is changed within a range of a predetermined value or less (opening diameter Φ1 or less) according to the focal length. Specifically, as the focal length approaches the telephoto end C from the middle B, it decreases monotonously from the opening diameter Φ1 toward the opening diameter Φ2. Here, it can be summarized as an equation as follows.

・ When “wide end A ≦ focal length <middle B” Maximum aperture diameter = Φ1 (maximum aperture diameter at wide end A) (Formula 1)
In the case of “middle B ≦ focal length”, the maximum value of the aperture diameter = ((Φ2−Φ1) × (focal length−B) / (CB)) + Φ1 (Formula 2)
When the exposure evaluation value detected by the DSP 133 is small and the aperture position calculation unit 145 calculates (determines) that it should operate to the open side, the maximum aperture diameter of the aperture indicated by the dotted line according to each focal length The diaphragm mechanism 102 is controlled so as not to exceed the value.

  Next, processing for executing the above-described calculation method will be described with reference to FIG.

  FIG. 4 is a flowchart showing a flow of processing for calculating the maximum value of the aperture diameter with respect to the focal length. In this process, each part in the microcomputer 150 cooperates to execute the process.

  In step S101, it is determined whether or not the current focal length is less than a predetermined focal length. In the present embodiment, the predetermined focal length is the middle B described above. In the determination process of step S101, for example, the determination is performed based on the zoom position calculated by the zoom position calculation unit 146. As a result of the determination in step S101, if the current focal length is less than the predetermined focal length, the process proceeds to step S102, and if it is equal to or greater than the predetermined focal distance, the process proceeds to step S103.

  In step S102, the above (Equation 1) is set as the maximum value of the aperture diameter, and the diaphragm is controlled so as not to have an aperture diameter larger than that.

  In step S103, the above (Equation 2) is set as the maximum value of the aperture diameter, and the aperture is controlled so as not to have an aperture diameter larger than that.

  In this way, by setting the maximum value of the aperture diameter to a certain value, that is, the maximum value at the wide end up to a certain focal length, the maximum value of the aperture diameter is constant or monotonous with respect to the focal length as in conventional lenses. It can be reduced and calculation is easy. Further, although the mechanical end is close to the maximum value at the wide end, a maximum value larger than the maximum value at the wide end is not set, so that a large margin can be obtained for the mechanical end. As a result, it is possible to prevent power from being continuously supplied to operate the aperture to the open side even though the aperture is not enlarged any more, while the aperture is being moved to the open side. Can also be prevented.

  Although the present invention has been described in detail based on preferred embodiments thereof, the present invention is not limited to these specific embodiments, and various forms within the scope of the present invention are also included in the present invention. included. A part of the above-described embodiments may be appropriately combined.

  The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

DESCRIPTION OF SYMBOLS 101 Zoom lens group 102 Diaphragm mechanism 103 Shift lens group 104 Focus lens group 141 Focus position calculation part 142 1st shift lens position calculation part 143 2nd shift lens position calculation part 145 Diaphragm position calculation part 146 Zoom position calculation part 150 Micro Computer

Claims (4)

A diaphragm means for controlling the amount of incident light according to the size of the aperture diameter;
Aperture driving means for operating the aperture means;
A photographic lens including at least three lens groups;
Lens driving means for driving the photographing lens so that at least three or more lens groups included in the photographing lens move in the optical axis direction when changing the focal length;
Control means for controlling the diaphragm driving means and the lens driving means,
In order to satisfy the minimum F value when the focal length is at the wide end, at some focal lengths, the aperture of the aperture stop is larger than the aperture diameter of the aperture at the wide end corresponding to the minimum F value. An imaging device that needs to have a large aperture,
Said control means, said minimum despite the maximum opening diameter of the diaphragm means used during shooting, the focal length in the case the focal length at the time of photographing is less than the predetermined focal length the is part of the focal length or The aperture diameter of the aperture means at the wide end corresponding to the F value is set. When the focal length at the time of shooting is equal to or greater than the predetermined focal length , the aperture means of the aperture means at the wide end corresponding to the minimum F value is used. An image pickup apparatus characterized in that the focal length becomes smaller as it approaches the telephoto end within a range of an aperture diameter or less. Wherein when the focal length at the time of photographing of more than the predetermined focal length, and characterized in that is monotonically decreasing in linear the maximum opening diameter of the aperture means as the focal length approaches the telephoto end The imaging device according to claim 1 . The photographing lens includes a zoom lens group, a focus lens group, and a shift lens group,
The lens driving means drives each lens group so that the zoom lens group, the focus lens group, and the shift lens group move in the optical axis direction when changing the focal length. Or the imaging device of 2 . A diaphragm unit that controls the amount of incident light according to the size of the aperture diameter, a diaphragm drive unit that operates the diaphragm unit, a photographing lens that includes at least three lens groups, and the photographing lens when changing the focal length A lens driving unit that drives the photographing lens so that at least three lens groups included in the lens unit move in the optical axis direction, and a control unit that controls the diaphragm driving unit and the lens driving unit. In order to satisfy the minimum F value when the distance is the wide end, the aperture diameter of the aperture means is larger than the aperture diameter of the aperture means at the wide end corresponding to the minimum F value at some focal lengths. A method for controlling an imaging apparatus that needs to be increased,
Said control means, said minimum despite the maximum opening diameter of the diaphragm means used during shooting, the focal length in the case the focal length at the time of photographing is less than the predetermined focal length the is part of the focal length or The aperture diameter of the aperture means at the wide end corresponding to the F value is set. When the focal length at the time of shooting is equal to or greater than the predetermined focal length , the aperture means of the aperture means at the wide end corresponding to the minimum F value is used. A control method for an imaging apparatus, comprising: a control step of decreasing a focal length closer to a telephoto end within a range of an aperture diameter or less.

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