JP5586838B2 - Imaging apparatus and zoom control method - Google Patents

Description

  The present invention relates to an image pickup apparatus having an optical zoom function and an electronic zoom function, and a zoom control method.

  Light has a refractive index that varies depending on the wavelength, light having a short wavelength has a high refractive index, and light having a long wavelength has a low refractive index. For this reason, in an apparatus having a lens such as an image pickup apparatus, when incident light passes through an image pickup lens for forming a subject image, a phenomenon of chromatic aberration in which the image formation position differs for each wavelength due to a difference in refractive index occurs. Chromatic aberration includes axial chromatic aberration and lateral chromatic aberration, both of which cause problems such as color blurring and reduced resolution.

FIG. 9 is a diagram for explaining axial chromatic aberration.
On-axis chromatic aberration is chromatic aberration with different imaging positions on the optical axis. When a white light beam is incident on the optical axis, the image formation position for each color is a lens for the image formation position of a blue light beam (hereinafter referred to as G) rather than the image formation position of a green light beam (hereinafter referred to as G). The image forming position of red (hereinafter referred to as R) light is positioned closer to the image sensor than the image forming position of G light. On-axis chromatic aberration causes effects such as color blur and a decrease in resolution on the entire screen due to the shift of the imaging position on the optical axis.

FIG. 10 is a diagram for explaining lateral chromatic aberration.
The chromatic aberration of magnification is chromatic aberration with different imaging positions on the imaging surface. When the position where incident light from an oblique direction when white light is incident on the optical axis forms an image on the image plane is seen for each color, the R light image formation position is the G light image formation position. The image is formed on the peripheral side of the screen as compared with the position, and conversely, the image forming position of the B light is imaged on the screen center side than the G light. Since the shift of the image formation position for each color on the image formation surface increases as the image height at the image formation position increases, color blur and a decrease in resolution appear particularly as the image periphery is approached.

  The amount of chromatic aberration depends on the aperture value and zoom magnification of the lens barrel at the time of shooting. As a characteristic of the lens, the light transmitted through the lens periphery has a larger image position shift than the light transmitted through the center of the lens. Thus, the amount of chromatic aberration increases. Further, as the zoom magnification changes to the telephoto side, the focal position shift becomes larger, and the image quality deterioration due to chromatic aberration becomes conspicuous.

  Conventionally, measures have been taken to reduce chromatic aberration by devising the shape of the lens, the glass material, the combination of lenses, and the like with respect to the above problem. However, since the shape of the lens is complicated, there is a problem that the cost is increased, or the cost is increased due to a change in the material of the lens.

Therefore, a method has been proposed in which when the zoom position moves to the telephoto side where aberrations are conspicuous, the image quality deterioration due to aberrations is reduced by changing the open F-number in the direction to narrow down (Patent Document 1).
JP-A-8-256288

  However, in the method of Patent Document 1, if the zoom operation is performed with the aperture fully open, the aperture F value moves in the direction to reduce the aperture and the amount of light decreases, so that the S / N deterioration and the shutter speed increase. There was a problem of image blurring.

  An object of the present invention is to provide an imaging apparatus and a zoom control method that can suppress image quality deterioration due to aberration without reducing the amount of light.

An imaging apparatus according to a first aspect of the present invention includes a lens barrel, an imaging unit that captures a subject image via the lens barrel, and at least a part of a lens included in the lens barrel. An optical zoom unit that changes the angle of view of the subject image that can be captured by the imaging unit, an electronic zoom unit that changes a shooting range of a captured image obtained from the imaging unit by image processing, and an aperture value of the lens barrel detection means for detecting, when performing the zooming operation to the telephoto side, to a first zoom magnification at the time of aperture of the lens barrel first value to zoom by the optical zoom means, the first The electronic zoom means is prioritized over the optical zoom means from a zoom magnification of 1, and when the aperture value of the lens barrel is a second value larger than the first value, the electronic zoom means is greater than the first zoom magnification. Also Stay until the second zoom magnification to zoom by the optical zoom means, and a zoom control means gives priority to the electronic zoom means than the optical zoom means from said second zoom magnification. The zoom control means is configured such that the aperture value of the lens barrel is the third value when the aperture value of the lens barrel is the first value and is higher than the second zoom magnification. When the zoom value is switched to the second value and further zoomed to the telephoto side, enlargement control is performed by changing the zooming ratio between the optical zoom means and the electronic zoom means .

A zoom control method according to a second aspect of the present invention includes a lens barrel, an imaging unit that captures a subject image via the lens barrel, and at least a part of a lens included in the lens barrel. An optical zoom unit that changes a field angle of a subject image that can be captured by the imaging unit, an electronic zoom unit that changes a shooting range of a captured image obtained from the imaging unit by image processing, and an aperture of the lens barrel. when performing detection means for detecting a value, a zoom operation to the telephoto side, to a first zoom magnification at the time of aperture of the lens barrel first value to zoom by the optical zoom means, said with giving priority to the electronic zoom means than the optical zoom means from the first zoom magnification, the first zoom magnification at the time of the second value aperture is greater than the first value of the lens barrel Remote high until the second zoom magnification performs a zoom operation by the optical zoom means, zoom in the image pickup apparatus and a zoom control means gives priority to the electronic zoom means than the optical zoom means from said second zoom magnification In the control method, the zoom control means causes the lens mirror in a state where the aperture value of the lens barrel is the first value and is higher than the second zoom magnification. When the aperture value of the cylinder is switched to the second value and the zoom operation is further performed to the telephoto side, zoom control is performed by changing the zooming ratio of the optical zoom unit and the electronic zoom unit.

According to the present invention, it is possible to minimize an increase in the amount of aberration due to a zoom operation without causing a deterioration in S / N due to a decrease in sensitivity and a problem of image blurring, and to obtain a good image with little deterioration in image quality due to aberration. Can be acquired.
Further, the above effect can be realized by properly using the optical zoom function and the electronic zoom function originally provided in the imaging apparatus, and can be realized without increasing the cost.

  Furthermore, by changing the zoom control method according to the aperture value, which is an important factor related to aberrations, it is possible to suppress aberrations to the minimum at any aperture position, and to realize a high aberration reduction effect. it can.

  Furthermore, the zoom control is simplified and the pattern of the zoom control method stored in the zoom control method storage means is reduced by preferentially using the electronic zoom only when the aperture area is desired to be prioritized. , Storage capacity can be reduced. This is also effective in increasing the processing speed in zoom control.

The best mode for carrying out the present invention will be described below with reference to the drawings.
In addition, each figure shown below is the figure shown typically, and in order to make an understanding easy, the magnitude | size and shape of each part are exaggerated suitably.
In the following description, specific numerical values, configurations, operations, and the like are shown and described, but these can be changed as appropriate.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a first embodiment of an imaging apparatus using a zoom control method according to the present invention.
The imaging apparatus of this embodiment includes a lens barrel 1, an imaging element 7, a signal processing unit 8, a recording device 11, a monitor 12, a diaphragm position detection unit 13, a zoom position detection unit 14, a zoom switch (SW) 19, and drive control. The unit 20 is provided.

  The lens barrel 1 of this embodiment includes four lens groups and a diaphragm 6 that constitute a photographing optical system. The imaging optical system of the lens barrel 1 includes a first lens group (focus group) 2, a second lens group (variator) 3, a third lens group (compensator) 4, and a fourth lens group (relay lens). It consists of five. Each lens group is configured by combining a plurality of lenses, and the first lens group 2 and the third lens group 4 do not move in the optical axis direction during zoom operation. The second lens group 3 is a lens for optically changing the zoom magnification. By moving the position of the second lens group 3 in the optical axis direction, the angle of view of the subject image formed on the image sensor 7 can be changed. In the photographing optical system of the present embodiment, when only the optical zoom is used, the zoom magnification is 8 times at the maximum (telephoto end).

  Here, the zoom magnification in the present embodiment will be described. In the imaging apparatus of the present embodiment, optical zoom and electronic zoom can be performed as described later. Therefore, the zoom magnification unless otherwise specified in the description of the present embodiment refers to a magnification calculated based on the photographing range of the photographed image regardless of whether the optical zoom is used or the electronic zoom is used. Accordingly, the magnification is not necessarily obtained simply from the focal length of the photographing optical system. For example, when the optical zoom by the photographing optical system is 3 times and the electronic zoom is 2 times, the zoom magnification of the obtained photographing range is 6 times.

The fourth lens group 5 moves in the optical axis direction according to the position change of the second lens group 3, and corrects the defocus of the subject image.
The diaphragm 6 is fixed between the third lens group 4 and the fourth lens group 5 so as not to move relative to the optical axis direction. The diaphragm 6 is a diaphragm means having an iris diaphragm that adjusts the amount of light of the subject image toward the image sensor 7.
The subject image transmitted from the first lens group 2 through the fourth lens group 5 is imaged on the imaging surface of the image sensor 7.

The image sensor 7 is a CCD (Charge Coupled) having a color filter.
Device) Image sensor or CMOS (Complementary Metal-Oxide)
Semiconductor) Image sensor. The imaging device 7 is an imaging unit that converts an optical subject image formed by the photographing optical system into an electrical analog signal. An analog signal that has been subjected to photoelectric conversion by the image sensor 7 and output is input to the signal processing unit 8.

The signal processing unit 8 includes an A / D converter 9 and an image processing unit 10.
The A / D converter 9 receives the analog signal output from the image sensor 7, converts it into a digital image signal, and outputs it to the image processing unit 10.
The image processing unit 10 receives the digital image signal output from the A / D converter 9, performs digital image processing such as gamma correction and contour correction on the digital image signal, and outputs it as a video signal.
The video signal output from the signal processing unit 8 is recorded on the recording device 11 or displayed on the monitor 12.

The recording device 11 includes a memory card, a hard disk device, and the like, and records the video signal output from the signal processing unit 8.
The monitor 12 includes a liquid crystal display device and the like, and displays the video signal output from the signal processing unit 8 and displays various information such as shooting conditions using characters, figures, and the like.
The aperture position detection unit 13 is a detection unit that detects the aperture position of the aperture 6, that is, the aperture value.
The zoom position detection unit 14 detects the zoom position of the lens barrel 1, that is, the focal length of the photographing optical system, by detecting the position of the second lens group 3 with an encoder (not shown) provided in the lens barrel 1. It is a detection part to do.
The zoom switch (SW) 19 is an input means for performing optical zoom and electronic zoom, and a zoom operation is performed only while the zoom SW 19 is being operated.

The drive control unit 20 includes an optical zoom drive unit 15, an electronic zoom drive unit 16, a zoom control unit 17, and a zoom control method storage unit 18.
The optical zoom drive unit 15 drives the second lens group 3 in the direction along the optical axis by giving a drive signal to a zoom actuator (not shown) according to an instruction from the zoom control unit 17 to change the zoom position of the photographing optical system. To do. The optical zoom drive unit 15 and the second lens group 3 form an optical zoom unit that performs optical zoom.

  In response to an instruction from the zoom control unit 17, the electronic zoom drive unit 16 gives the image processing unit 10 an instruction for a shooting range to be cut out as an electronic zoom. In response to the instruction from the electronic zoom drive unit 16, the image processing unit 10 cuts out and enlarges an image in the designated shooting range from the shot image. The electronic zoom driving unit 16 and the image processing unit 10 form electronic zoom means for performing electronic zoom for performing image processing and expanding a photographing range.

When performing a zoom operation, the zoom control unit 17 determines an optimum zoom method according to the aperture value detected by the aperture position detection unit 13 and the zoom position detected by the zoom position detection unit 14. Specifically, a combination of optical zoom and electronic zoom is determined. At this time, when the zoom control unit 17 acquires the detection results of the aperture position detection unit 13 and the zoom position detection unit 14, the zoom control unit 17 refers to the combination of the optical zoom and the electronic zoom stored in the zoom control method storage unit 18. Then, a combination method of optical zoom and electronic zoom to be actually applied is determined.
Thereafter, the zoom control unit 17 controls the optical zoom drive unit 15 and the electronic zoom drive unit 16 according to the determined combination method to perform a zoom operation.

  Here, the combination of the optical zoom and the electronic zoom is a combination of how the optical zoom and the electronic zoom are used in order to obtain a zoom magnification corresponding to the operation amount of the zoom SW 19 by the photographer. It is. For example, only optical zoom is used, optical zoom and electronic zoom are used together, how many times magnification is ensured by optical zoom, and how many magnification (magnification) is secured by electronic zoom.

The zoom control method storage unit 18 stores a combination method (zoom control method) of optical zoom and electronic zoom in a form corresponding to the zoom position of the lens barrel 1 and the aperture value of the aperture 6.
The zoom control method stored in the zoom control method storage unit 18 has an aberration that increases at the periphery of the shooting range as the field angle of the subject image obtained by optical zoom becomes smaller than a preset threshold value. It is determined to be. That is, in the optical zoom, the image is enlarged by the electronic zoom before the zoom magnification at which the aberration increases in the peripheral portion and the aberration amount exceeds the threshold value. Thereby, the aberration amount in the peripheral portion does not exceed the threshold value. Further, since the peripheral portion is excluded by the electronic zoom, the aberration included in the obtained image is extremely reduced.

In the optical zoom, the field angle of the subject image that can be photographed by the image sensor 7 is changed by driving the photographing optical system.
On the other hand, in the electronic zoom, the shooting range of the shot image obtained from the image sensor 7 is partially cut out and enlarged by image processing to change the apparent angle of view.
These optical zoom and electronic zoom can be executed independently or in combination. The zoom control unit 17 determines how to combine the optical zoom and the electronic zoom, or to execute them alone. The zoom control unit 17 controls the optical zoom driving unit 15 and the electronic zoom driving unit 16 according to the determined combination of the optical zoom and the electronic zoom, and performs a zoom operation. The zoom control unit 17 also controls the zoom operation using optical zoom or electronic zoom independently.

  The optical zoom is performed when the zoom control unit 17 determines that a zoom operation using the optical zoom is necessary. When performing optical zoom, the zoom control unit 17 moves the second lens group in the optical axis direction via the optical zoom drive unit 15 to change the zoom magnification to a desired zoom magnification.

  The electronic zoom is performed when the zoom control unit 17 determines that the zoom operation using the electronic zoom is necessary. When performing electronic zoom, the zoom control unit 17 changes the cutout range of the image data output from the A / D converter 9 via the electronic zoom driving unit 16 in the image processing unit 10, so that a desired zoom magnification is obtained. Change to

Next, the zoom control method in this embodiment will be described.
When the zoom operation is performed, the optical zoom and the electronic zoom have different ratios for expanding chromatic aberration. Therefore, in order to suppress an increase in the amount of chromatic aberration, it is desirable to perform a zoom operation with priority given to a smaller chromatic aberration expansion ratio.
The enlargement ratio of chromatic aberration due to the zoom operation mainly depends on the lens characteristics, and varies depending on the zoom magnification and the state of the diaphragm at that time. In general, when the zoom magnification is near the telephoto end, the magnification ratio of chromatic aberration due to optical zoom is significantly larger than that of electronic zoom, and near the wide-angle end, the magnification ratio of chromatic aberration due to optical zoom is relatively small. Further, when the aperture value is close to the full aperture, the transmitted light around the lens is condensed, so that the chromatic aberration increases significantly.

FIG. 2 is a conceptual diagram showing the chromatic aberration magnification ratio with respect to the zoom magnification when the aperture value is F8.0 in the first embodiment.
FIG. 3 is a conceptual diagram showing the chromatic aberration magnification ratio with respect to the zoom magnification when the aperture value is F5.6 in the first embodiment.
FIG. 4 is a conceptual diagram showing the chromatic aberration magnification ratio with respect to the zoom magnification when the aperture value is F3.4 in the first embodiment.
FIG. 5 is a conceptual diagram showing the chromatic aberration magnification ratio with respect to the zoom magnification when the aperture value is F2.0 in the first embodiment.
2 to 5 show the characteristics of the chromatic aberration magnification ratio at each zoom magnification when using the optical zoom and when using the electronic zoom, for each stop position. The unit of the chromatic aberration magnification ratio indicates the magnification ratio of the aberration amount at each zoom magnification when the chromatic aberration amount at the wide-angle end is used as a reference.

In the case of F8.0 shown in FIG. 2, the chromatic aberration magnification ratio is higher in the electronic zoom than in the optical zoom until the zoom magnification is 7.0 times, and the chromatic aberration is larger in the optical zoom than in the electronic zoom at a zoom magnification higher than that. The ratio is high. In this case, the optical zoom is preferentially used until the zoom magnification is 7.0 times, and the electronic zoom is preferentially used when the zoom magnification is higher than that, thereby degrading the image quality due to the enlargement ratio of chromatic aberration, that is, chromatic aberration. Can be minimized.
For other aperture values, zoom is 6.0 times at F5.6 shown in FIG. 3, 5.0 times at F3.4 shown in FIG. 4, and 4.0 times at F2.0 shown in FIG. When the magnification is exceeded, the chromatic aberration magnification ratio by the optical zoom exceeds the chromatic aberration magnification ratio by the electronic zoom. Therefore, if electronic zoom is prioritized at higher zoom magnification, image quality degradation due to chromatic aberration can be minimized.

FIG. 6 is a conceptual diagram illustrating a zoom control method according to the first embodiment.
FIG. 6 shows a zoom control method for each aperture value, which is optimal from the above characteristics, and this zoom control method is stored in the zoom control method storage unit 18.
A conventional zoom control method is also shown at the top of FIG. Conventionally, after enlarging to a zoom magnification of 8.0 times (optical telephoto end) using optical zoom preferentially, enlargement processing by electronic zoom has been performed.

  In the present embodiment, the start position of the electronic zoom priority area is changed for each aperture value. Specifically, in the case of F8.0, the electronic zoom is given priority from the zoom magnification of 7.0 times, 6.0 times in the case of F5.6, 5.0 times in the case of F3.4, F2.0 In this case, the electronic zoom is preferentially used from 4.0 times. By changing the start position of the electronic zoom priority area for each aperture value, it is possible to minimize the expansion of chromatic aberration at any aperture value.

  However, since there is a problem that the resolution is lowered when the electronic zoom is used, the optimum position of the start position of the electronic zoom priority area is determined in consideration of the characteristics of both the reduction in resolution and the magnification ratio of chromatic aberration. Is desirable. In the present embodiment, a zoom control method will be described that places an emphasis on suppression of chromatic aberration expansion, assuming that there is little reduction in resolution due to electronic zoom.

Further, as a zoom method in the electronic zoom priority area, a method in which optical zoom and electronic zoom are used alternately and a method in which optical zoom and electronic zoom are used in combination are conceivable. In the present embodiment, a zoom method using both optical zoom and electronic zoom is used, but it may be used alternately.
The zoom ratio between the optical zoom and the electronic zoom when using the optical zoom and the electronic zoom at the same time remains until the optical zoom reaches the telephoto end and the zoom magnification left until the electronic zoom reaches the maximum. Determined by the ratio of zoom magnification.

  For example, it is assumed that the enlargement ratio of the electronic zoom can be up to 8.0 times. At this time, it is assumed that the zoom operation is performed from the wide-angle end in the state of F8.0, the zoom magnification is 7.0 times only by the optical zoom, that is, the start position of the electronic zoom priority area is reached. At this time, the remaining zoom magnification in the optical zoom is 8/7, and the remaining zoom magnification in the electronic zoom is 8.0. Therefore, the zooming ratio between the optical zoom and the electronic zoom in the electronic zoom priority area is optical zoom: electronic zoom = 1: 7. For other aperture values, the zoom ratio is 1: 6 for F5.6, 1: 5 for F3.4, and 1: 4 for F2.0.

Next, a zoom control method when the aperture value is changed during the zoom operation will be described.
For example, assume that the zoom operation is performed from the wide-angle side to the telephoto side in the state of F2.0, and the aperture value is changed to F8.0 when the zoom magnification is 8.0 times. In this state, when zooming further to the telephoto side, the zooming ratio between the optical zoom and the electronic zoom is changed so that the remaining zoom magnification in the optical zoom and the remaining zoom magnification in the electronic zoom can be enlarged uniformly. . On the other hand, when the zoom operation to the wide-angle side is performed after the aperture value has been changed, the area is set to be used only for optical zoom with a zoom magnification of 7.0. That is, the zoom ratio between the optical zoom and the electronic zoom is changed so that the zoom magnification exceeding 7.0 times by the optical zoom and the zoom magnification by the electronic zoom can be reduced uniformly.

  Further, it is assumed that the zoom operation is performed from the wide-angle side to the telephoto side in the state of F2.0, and the aperture value is changed to F8.0 when the zoom magnification is 6.0 times. In this state, when the zoom operation is further performed to the telephoto side, only the optical zoom is used until the magnification of the optical zoom becomes 7.0 times. When the optical zoom becomes 7.0 times or more, the electronic zoom priority area Change to be On the other hand, when zooming to the wide angle side after the aperture value has been changed, reduction processing is performed before electronic zoom, and when the enlargement ratio by electronic zoom becomes 1.0, reduction by optical zoom is performed. To start.

  Furthermore, it is assumed that the zoom operation is performed from the wide angle side to the telephoto side in the state of F8.0, and the aperture value is changed to F2.0 in the state of the zoom magnification of 8.0. In this state, when zooming further to the telephoto side, the zooming ratio between the optical zoom and the electronic zoom is changed so that the remaining zoom magnification in the optical zoom and the remaining zoom magnification in the electronic zoom can be enlarged uniformly. . On the other hand, when the zoom operation to the wide-angle side is performed after the aperture value is changed, the area is set to be used only for optical zoom with a zoom magnification of 4.0. That is, the zoom ratio between the optical zoom and the electronic zoom is changed so that the zoom magnification exceeding 4.0 times by the optical zoom and the zoom magnification by the electronic zoom can be reduced uniformly.

  Furthermore, it is assumed that the zoom operation is performed from the wide-angle side to the telephoto side in the state of F8.0, and the aperture value is changed to F2.0 in the state where the zoom magnification is 6.0 times. In this state, when zooming further to the telephoto side, the zooming ratio between the optical zoom and the electronic zoom is changed so that the remaining zoom magnification in the optical zoom and the remaining zoom magnification in the electronic zoom can be enlarged uniformly. On the other hand, when the zoom operation to the wide angle side is performed after the aperture value is changed, only the optical zoom is used because the enlargement by the electronic zoom is not performed.

FIG. 7 is a flowchart of the zoom operation in the first embodiment.
When the zoom SW 19 is operated by the photographer, the zoom operation is started.
In step (hereinafter referred to as S) 101, the zoom control unit 17 detects and acquires the zoom position and the aperture value by the zoom position detection unit 14 and the aperture position detection unit 13.
In S103, the zoom control unit 17 acquires a zoom control method corresponding to the zoom position and aperture value acquired in S101 with reference to the zoom control method storage unit 18.

  In S <b> 105, the zoom control unit 17 determines a zoom control method to be actually applied based on the zoom control method acquired with reference to the zoom control method storage unit 18. Here, when the zoom control method acquired with reference to the zoom control method storage unit 18 can be applied as it is, a combination of optical zoom and electronic zoom in the zoom control method is employed. On the other hand, there may be a case where the zoom control method acquired with reference to the zoom control method storage unit 18 cannot be applied as it is, such as when the aperture value is changed during the zoom operation. In such a case, as described above, the subsequent zoom control method is determined according to the optical zoom magnification and the electronic zoom magnification at that time.

In S107, the zoom control unit 17 determines whether the zoom control method determined in S105 is only optical zoom or electronic zoom priority (in this embodiment, optical zoom and electronic zoom are used together). If only the optical zoom is used, the process proceeds to S109. If the electronic zoom is prioritized, the process proceeds to S111.
In S <b> 109, the zoom control unit 17 gives an instruction to drive the second lens group 3 to the optical zoom drive unit 15 and executes optical zoom.
In S111, the zoom control unit 17 performs an electronic zoom priority operation. Specifically, an instruction to drive the second lens group 3 is given to the optical zoom driving unit 15 to execute the optical zoom, and an instruction to execute the electronic zoom is given to the electronic zoom driving unit 16, so Cut out and enlarge the image in the specified shooting range. As a result, it is possible to obtain a photographed image having a zoom magnification obtained by combining the optical zoom magnification by the optical zoom and the enlargement ratio by the electronic zoom.

  In S113, it is determined whether or not the zoom magnification corresponds to the operation amount of the zoom SW 19 by the photographer. If the required zoom magnification is not obtained, the process returns to S101, and if the required zoom magnification is obtained, the zoom operation is terminated.

As described above, according to the first embodiment, enlargement of chromatic aberration due to a zoom operation can be suppressed to a minimum, and image quality deterioration such as color blur due to chromatic aberration and a reduction in resolution can be reduced.
The configuration of the first embodiment can be realized without adding a new configuration as hardware. Therefore, expansion of chromatic aberration due to the zoom operation can be suppressed without increasing the cost.

(Second Embodiment)
In the first embodiment, different zoom control methods are stored in the zoom control method storage unit 18 for each aperture position. However, for example, in the case of a lens with suppressed chromatic aberration, if only chromatic aberration only in the vicinity of the open, where chromatic aberration is conspicuous, is suppressed. Good. Therefore, in the second embodiment, the zoom control method is simplified by changing the start position of the electronic zoom priority area to the wide-angle side only when the aperture is fully open, where image degradation due to chromatic aberration is conspicuous.
The circuit configuration of the second embodiment is equivalent to that of the first embodiment. Therefore, the same reference numerals are given to the portions that perform the same functions as those in the first embodiment described above, and repeated descriptions are omitted as appropriate.

FIG. 8 is a conceptual diagram illustrating a zoom control method according to the second embodiment.
The zoom control method of the second embodiment is stored in the zoom control method storage unit 18 as in the first embodiment.
As shown in FIG. 8, when the aperture value detected by the aperture position detection unit 13 is not the full aperture value, the optical zoom is preferentially used and the zoom magnification is expanded to 8.0 times (optical telephoto end). The enlargement process is performed by operating only the electronic zoom. Therefore, the same zoom control method is used for any aperture value other than the full aperture, and the processing becomes easy.

  On the other hand, when the aperture position is open, the start position of the electronic zoom priority area using optical zoom and electronic zoom is changed to the wide-angle end side. The starting position at this time is determined in consideration of the characteristics of the resolution reduction and the chromatic aberration magnification ratio. In the present embodiment, since the zoom magnification of 6.0 times is optimal, the start position of the electronic zoom priority area is set to 6.0 times. Further, the zoom method in the electronic zoom priority area uses a zoom method using both optical zoom and electronic zoom, as in the first embodiment.

The zoom control method when the aperture value is changed during the zoom operation is the same as in the first embodiment.
It is assumed that the zoom operation is performed from the wide-angle side to the telephoto side in a state other than the aperture opening, and the aperture value is changed to the open state at a zoom magnification of 7.0. In this state, when zooming further to the telephoto side, the zooming ratio between the optical zoom and the electronic zoom is changed so that the remaining zoom magnification in the optical zoom and the remaining zoom magnification in the electronic zoom can be enlarged uniformly. . On the other hand, when the zoom operation to the wide angle side is performed after the aperture value is opened, it is set to be an area where only optical zoom is performed at a zoom magnification of 6.0 times. That is, the zoom ratio between the optical zoom and the electronic zoom is changed so that the zoom magnification exceeding 6.0 times by the optical zoom and the zoom magnification by the electronic zoom can be reduced uniformly.

  Further, it is assumed that the zoom operation is performed from the wide-angle side to the telephoto side in a state other than the full aperture state, and the aperture value is changed to the full open state at a zoom magnification of 9.0 times. In this state, when the zoom operation is further performed to the telephoto side, the position of the optical zoom is already at the telephoto end, so only the electronic zoom is used. On the other hand, when the zoom operation to the wide angle side is performed after the aperture value is opened, it is set to be an area where only optical zoom is performed at a zoom magnification of 6.0 times. That is, the zoom ratio between the optical zoom and the electronic zoom is changed so that the zoom magnification exceeding 6.0 times by the optical zoom and the zoom magnification by the electronic zoom can be reduced uniformly.

  Furthermore, it is assumed that the zoom operation is performed from the wide-angle side to the telephoto side with the aperture opened, and the aperture value is changed to other than the full aperture with a zoom magnification of 7.0. In this state, when the zoom operation is further performed to the telephoto side, only the optical zoom is used until the magnification of the optical zoom becomes 7.0 times. When the optical zoom becomes 7.0 times or more, the electronic zoom priority area Change to be On the other hand, when the zoom operation to the wide angle side is performed after the aperture value is changed to other than the full aperture, the reduction process is performed first after the electronic zoom, and the optical zoom is performed when the enlargement ratio is 1.0 times. Start zooming out.

  Furthermore, it is assumed that the zoom operation is performed from the wide-angle side to the telephoto side with the aperture open, and the aperture value is changed to other than open with the zoom magnification of 9.0. In this state, when the zoom operation is further performed to the telephoto side, the optical zoom is performed first, and when the optical zoom reaches the telephoto end, the enlargement process by the electronic zoom is started. On the other hand, when the zoom operation to the wide angle side is performed after the aperture value is changed to other than the full aperture, the reduction process is performed first after the electronic zoom, and the optical zoom is performed when the enlargement ratio is 1.0 times. Start zooming out.

  As described above, according to the second embodiment, with a simple zoom control method, it is possible to minimize the expansion of chromatic aberration due to a zoom operation, and to reduce image quality degradation such as color blur due to chromatic aberration and a decrease in resolution. it can.

(Deformation)
The present invention is not limited to the embodiment described above, and various modifications and changes are possible, and these are also within the scope of the present invention.
(1) In each embodiment, an example in which a zoom control method is set by paying attention to chromatic aberration has been shown. However, the present invention is not limited to this, and for example, paying attention to other aberrations such as spherical aberration, coma, and astigmatism. A zoom control method may be set.

(2) In each embodiment, the imaging apparatus in which the lens barrel 1 is integrally provided has been described as an example. However, the present invention is not limited to this, and for example, as an imaging apparatus or an imaging system in which the lens barrel is detachable. Also good. In this case, a portion corresponding to the zoom control method storage unit 18 may be provided in the lens barrel.

  Note that the first embodiment, the second embodiment, and the modified embodiments can be used in appropriate combination, but detailed description thereof is omitted. Further, the present invention is not limited by the embodiments described above.

It is a figure which shows the structure of 1st Embodiment of the imaging device using the zoom control method by this invention. In a 1st embodiment, it is a key map showing a chromatic aberration magnification ratio to zoom magnification when an aperture value is F8.0. In a 1st embodiment, it is a key map showing a chromatic aberration magnification ratio to zoom magnification when an aperture value is F5.6. In a 1st embodiment, it is a key map showing a chromatic aberration magnification ratio to zoom magnification when an aperture value is F3.4. In 1st Embodiment, it is a conceptual diagram which shows the chromatic aberration expansion ratio with respect to zoom magnification in case an aperture value is F2.0. It is a conceptual diagram which shows the zoom control method in 1st Embodiment. 3 is a flowchart of a zoom operation in the first embodiment. It is a conceptual diagram which shows the zoom control method in 2nd Embodiment. It is a figure explaining axial chromatic aberration. It is a figure explaining lateral chromatic aberration.

Explanation of symbols

1 Lens barrel 2 First lens group (focus group)
3 Second lens group (variator)
4 Third lens group (compensation)
5 Fourth lens group (relay lens)
6 Aperture 7 Image Sensor 8 Signal Processing Unit 9 A / D Converter 10 Image Processing Unit 11 Recording Device 12 Monitor 13 Aperture Position Detection Unit 14 Zoom Position Detection Unit 15 Optical Zoom Drive Unit 16 Electronic Zoom Drive Unit 17 Zoom Control Unit 18 Zoom Control method storage unit 19 Zoom SW
20 Drive controller

Claims (11)

A lens barrel;
An imaging unit that captures a subject image via the lens barrel;
An optical zoom unit that moves at least a part of a lens included in the lens barrel and changes a field angle of a subject image that can be captured by the imaging unit;
Electronic zoom means for changing a shooting range of a shot image obtained from the imaging unit by image processing;
Detecting means for detecting an aperture value of the lens barrel;
When zooming to the telephoto side, when the aperture value of the lens barrel is the first value, the zoom operation is performed by the optical zoom means up to the first zoom magnification, and from the first zoom magnification to the optical The electronic zoom means is prioritized over the zoom means, and the second zoom magnification is higher than the first zoom magnification when the aperture value of the lens barrel is a second value larger than the first value. Zoom control means that performs a zoom operation by the optical zoom means and prioritizes the electronic zoom means over the optical zoom means from the second zoom magnification,
The zoom control means is configured such that the aperture value of the lens barrel is the third value when the aperture value of the lens barrel is the first value and is higher than the second zoom magnification. An image pickup apparatus characterized in that when the zoom value is switched to the second value and further zoomed to the telephoto side, enlargement control is performed by changing a zooming ratio between the optical zoom means and the electronic zoom means. A zoom control method storage means for storing a combination of the optical zoom means and the electronic zoom means corresponding to the state of the lens barrel;
The zoom control means determines how to combine the optical zoom means and the electronic zoom means based on the combination stored in the zoom control method storage means;
The imaging apparatus according to claim 1. The detecting means detects a zoom position of the lens barrel changed by the optical zoom means;
The zoom control means determines how to combine the optical zoom means and the electronic zoom means according to the zoom position of the optical zoom means detected by the detection means;
The imaging device according to claim 1 or 2, wherein The zoom control means and the optical zoom means and the optical zoom means so that the aberration that increases at the periphery of the photographing range becomes smaller than a preset threshold as the angle of view of the subject image obtained by the optical zoom means becomes narrower. Determining how to combine with electronic zoom means,
The imaging apparatus according to claim 3. The zoom control unit determines how to combine the optical zoom unit and the electronic zoom unit so that the electronic zoom unit is preferentially used as the angle of view of the subject image obtained by the optical zoom unit becomes narrower. ,
The imaging device according to claim 3 or 4, wherein The lens barrel includes a diaphragm unit that adjusts a light amount of a subject image toward the imaging unit,
The detection means detects an aperture value of the aperture means,
The zoom control means determines how to combine the optical zoom means and the electronic zoom means according to the aperture value of the aperture means detected by the detection means;
The imaging device according to any one of claims 1 to 5, wherein The zoom control unit includes the optical zoom unit and the electronic zoom unit so that an aberration that increases in a peripheral portion of the photographing range becomes smaller than a preset threshold as the aperture value of the aperture unit approaches the full aperture. Determining how to combine with
The imaging apparatus according to claim 6. The zoom control unit determines how to combine the optical zoom unit and the electronic zoom unit so that the electronic zoom unit is preferentially used as the aperture value of the aperture unit approaches the full aperture;
The imaging apparatus according to claim 6 or 7, wherein Using the electronic zoom means with priority only when the aperture means is in a preset aperture value area;
The imaging device according to claim 8. The method of combining the optical zoom unit and the electronic zoom unit determined by the zoom control unit includes at least a combination method of using the optical zoom unit and the electronic zoom unit together,
The imaging device according to any one of claims 1 to 9, wherein: A lens barrel, an imaging unit that captures a subject image via the lens barrel, and an angle of view of a subject image that can be captured by the imaging unit by moving at least a part of a lens included in the lens barrel An optical zoom unit that changes the image, an electronic zoom unit that changes a shooting range of a shot image obtained from the imaging unit by image processing, a detection unit that detects an aperture value of the lens barrel, and a zoom operation toward the telephoto side. the first to the zoom magnification to zoom by the optical zoom means, the electrons than the optical zoom means from said first zoom magnification at the time when the aperture value is the first value of the lens barrel to perform causes priority to zoom means, to a second zoom magnification higher than the first zoom magnification at the time of the second value aperture is greater than the first value of the lens barrel the optical zoom To zoom by means provides a zoom control method in an image pickup apparatus and a zoom control means gives priority to the electronic zoom means than the optical zoom means from said second zoom magnification,
With the zoom control means, the aperture value of the lens barrel is the first value, and the aperture value of the lens barrel is the third zoom magnification higher than the second zoom magnification. A zoom control method characterized in that when the zoom value is switched to the second value and further zoomed to the telephoto side, enlargement control is performed by changing the zooming ratio of the optical zoom means and the electronic zoom means.

Images