JP2006178211A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of attaining excellent automatic focusing performance in any interchangeable lens, in any state of the lens, in any combination with cameras and in any photographing state when the focus shift is recognized or when responsiveness is deteriorated, overshoot is caused or stability is insufficient. <P>SOLUTION: The interchangeable lens has an automatic focusing means and the minimum driving pitch of the interchangeable lens is changed according to the identification information of the camera, or the interchangeable lens has the automatic focusing means and the minimum driving pitch of the interchangeable lens is changed according to the resolved spatial frequency information of the camera, whereby the excellent automatic focusing performance is attained in any interchangeable lens, in any state of the lens, in any combination with the cameras and in any photographing state. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an imaging device such as a camera that is mounted with a replaceable lens device and that captures still images and moving images.

Conventionally, as an automatic focusing method used in video input devices such as video and cameras, a high-frequency component is extracted from a video signal obtained from a solid-state image pickup device such as a CCD image pickup device, and this high-frequency component is maximized. A so-called hill-climbing system is known in which the photographic lens is driven to adjust the focus. Such an automatic focus adjustment method does not require a special optical member for focus adjustment, and has an advantage of being able to focus accurately regardless of distance regardless of distance.
With reference to FIG. 19, the hill-climbing automatic focusing apparatus will be briefly described.
The light from the subject includes a fixed first lens group 110, a variable magnification second lens group 112 (hereinafter referred to as a variable magnification lens), a diaphragm 114, a fixed third lens group 116, and The light enters the image pickup surface (photoelectric conversion surface) of the image pickup device 120 through a fourth lens group 118 (hereinafter referred to as a focusing lens) having both a focus adjustment function and a function of correcting the movement of the focal plane due to zooming. To do.
The image sensor 120 converts an optical image on the imaging surface into an electric signal. The output signal of the image sensor 120 is sampled and held by the CDS circuit 122, amplified to a predetermined level by the AGC circuit 124, and converted into a digital signal by the A / D converter 126. The output signal of the A / D converter 126 is supplied to a camera signal processing circuit (not shown). Since the processing content of the camera signal processing circuit is well-known not related to the present invention, further description thereof is omitted.
The output of the A / D converter 126 is also applied to a band pass filter (BPF) 128. The BPF 128 extracts a predetermined high frequency component from the video data output from the A / D converter 126. The output of the BPF 128 is all converted to a positive polarity signal by the ABS circuit 130. The gate signal generation circuit 132 generates a gate signal that designates a portion corresponding to the in-focus detection area in the shooting screen, and the detection circuit 134 is in accordance with the gate signal output from the gate signal generation circuit 132. From this output, only a signal corresponding to the in-focus detection region is detected (for example, peak hold or integration) and output as an AF (automatic focus adjustment) evaluation value at an interval synchronized with an integral multiple of the vertical synchronization signal.
A main control circuit 136 comprising a microcomputer takes in the output (AF evaluation value) of the detector 134, determines the focusing speed according to the degree of focus, and the motor driving direction in which the AF evaluation value increases, and the motor driving circuit 138 is controlled. The motor drive circuit 138 drives the focus motor 140 in accordance with a command from the main control circuit 136, and moves the focusing lens 118 to a specified position at a specified speed. As a result, the focusing lens 118 is controlled to a position where the output of the BPF 128 is maximized.
The main control circuit 136 also rotates the zoom motor 144 by the motor driving circuit 142 in accordance with the user's zooming operation, and moves the zoom lens 112 to a designated position. Thereby, the focal length can be changed, and the photographing magnification changes.

FIG. 20 shows a flowchart of a hill-climbing control type automatic focus adjustment operation by the main control circuit 136.
The main control circuit 136 executes automatic focus adjustment control while capturing the output (AF evaluation value) of the detector 134 at intervals synchronized with an integral multiple of the vertical synchronization signal. When the power is turned on or when the photographing preparation mode is entered, AF feedback control is started (S1), and the focusing lens 118 is driven in the direction in which the AF evaluation value increases to perform hill climbing control (S2). The peak of the mountain is determined by overshooting the mountain top once and then returning (S3), stopping at the highest level, and waiting for restart (S4). When it is detected that the level of the AF evaluation value is lower than the level at the time of stop, the AF feedback control is restarted (S5).
In addition to a method of extracting a high frequency component in a video signal by the BPF 128, a configuration in which a high frequency component is extracted from a conversion result of a two-dimensional orthogonal transformer used in recent years for image compression and used for automatic focus adjustment. Has also been proposed.
JP-A-8-327893 discloses a dynamic focus adjustment device that eliminates the influence of the spatial frequency of a focus detection target without changing the focus detection optical system and always performs focus adjustment based on the best image plane position. Proposed.
JP-A-8-327893

In recent years, zooming of lenses and higher magnification, and higher pixel density and higher density of imaging means are accelerating for camera imaging, and still images and moving images can be taken. Since an image pickup apparatus capable of picking up an image such as a high-definition method as well as a conventional TV method such as NTSC and PAL for a video that can be selected and a moving image has been devised and spread, a camera and a lens are used in an interchangeable lens system. Depending on the release date, improvement of imaging means and resolving power and higher image quality are progressing, and it is spreading to various forms.
For example, in the early interchangeable lens system, only standard TV signals were recorded, but cameras and lenses capable of shooting still images and high-definition images higher than TV signals were developed and released. A camera lens will be present. In terms of marketability, merchantability, and compatibility, it is preferable that these combinations can be photographed without problems. For example, if the camera is HD compatible and the old lens cannot be photographed even in combination with an object designed for a standard TV, the attractiveness of the marketability and the merchantability as an interchangeable lens system will be significantly reduced.

However, in the case of this combination, for example, since the camera is a high-definition high-definition, the spatial frequency to be resolved is high as shown in FIG. 5, and therefore the extraction frequency characteristic of the high-frequency component detected from the video signal is also compared with the conventional TV system. It can be easily imagined that appropriate AF cannot be performed unless further information is required in some cases. On the other hand, in this example, the lens not only has a resolution for standard TV, but an AF system may exist in the lens. However, the AF system has only a conventional standard TV.
As described above, the focus detection means for performing AF is performed by extracting a high-frequency component in the video signal. Since the frequency to be extracted is fixed in advance by the camera, for example, the camera can be combined with the above-described combination. If the in-focus signal is set for high-definition, the characteristics will not match and the AF operation will not be appropriate, or if the AF system is present in the lens, Since only AF can be performed, it is conceivable that an appropriate operation cannot be performed or in some cases it does not operate.

In this case, the frequency of the signal to be extracted is high, the peak width of the signal is narrower than that of NTSC, and the range in which blur is recognized is narrow. In a lens whose driving amount is designed for NTSC, there is a problem that it is impossible to stop at the peak position in the vicinity of the true focus because the focus peak width and the range where the focus blur is not recognized are wide. Even if the spatial frequency to be optically resolved corresponds to the high vision, in this case, the AF may not be stopped at the focus peak. Further, when the frequency for extracting the high frequency component of the video signal is higher than that of NTSC in accordance with the spatial frequency to be remodeled by HDTV, the frequency at which the deterioration of the signal in the case of blurring is far from the peak position as shown in FIG. 6 is low. Since it is larger than the case, it is difficult to detect the direction of the pin. In addition, in the case of an AF system adapted to the conventional NTSC such as this example in which a system that takes this point into consideration is not easy, there is a possibility that the AF operation is remarkably degraded.
That is, when the resolution frequency is high, the minimum driveable pitch must be fine under the same optical conditions. On the other hand, when the frequency is low, the above problem occurs even if the drive pitch is finer than necessary. The following issues describe the issues arising from differences in spatial frequency depending on the state of each lens and camera in the interchangeable lens system.
Contrary to this example, when the camera is combined with an old NTSC lens whose lens drives fine pitch for high vision, the AF signal from the camera is derived from a video signal that matches the frequency modified by NTSC. AF is performed by the frequency extracted by the lens, and the focus peak is wide and gentle as shown in FIG. 6 near the in-focus position. There is a problem that AF driving stops midway during the peak because no signal change can be obtained midway. In addition, since the driving change is fine in the signal even when away from the peak, there is a concern that the mountain cannot be fully climbed during the direction detection system or the above-described mountain climbing operation.
Also, for example, a camera that can shoot still images and NTSC moving images has an AF function that matches the lens to the NTSC, and the focusing signal of the camera matches the frequency extracted by the NTSC method, and still images from the NTSC method. It is also assumed that recording is performed with high pixels and high density.

FIG. 7 shows a comparison between the spatial frequency characteristics resolved by NTSC and the spatial frequency resolved when recording with high pixels and high density during still image shooting.
As shown in FIG. 7, for example, in the case of NTSC, the spatial frequency to be resolved is NTSC Hz, and the minimum driving amount of the lens is also NTSC. In still image shooting, for example, more pixels than the necessary spatial frequency of NTSC are used. The spatial frequency “Stil-300” Hz to be resolved in the case of assuming that shooting is performed with a number of 3 million pixels is higher than the spatial frequency to be resolved in NTSC. The spatial frequency to be resolved here is not the limit frequency that can be resolved as indicated by the arrow in the figure, but a sufficiently high frequency of the MTF is assumed to be the spatial frequency to be resolved. Although this determination method is arbitrary, a sufficient MTF can be obtained by using about 80% of the limit resolution spatial frequency as a guide.
Therefore, when shooting a still image of 3 million pixels using the NTSC resolution spatial frequency “NTSC” Hz as a frequency characteristic for AF focus detection, due to the difference in resolution limit of the spatial frequency and the difference in stop accuracy. You may be able to recognize out-of-focus blur. That is, the focus peak cannot be detected for the subject of “Still-300” Hz, and the stop position is rough.

FIG. 6 shows the relationship between the high frequency component signal output in the AF signal and the focus position when the extraction frequency is high.
As can be seen from this figure, the peak position width when the extraction frequency is high is narrower than the peak position width when the extraction frequency is low. In this example, even if the signal is a peak signal at “NTSC” Hz. This is because the peak is not necessarily “Still-300” Hz. On the other hand, if the AF extraction frequency is adjusted for still image shooting in the above case, it is possible to perform shooting with good focus in still image shooting. However, when moving images are shot, the AF operation sets the extraction frequency for moving images. As can be seen from FIG. 6, the rising of the peak of the signal is steep as compared with the case of setting, so that the filter frequency at “NTSC” Hz having a low spatial frequency has a spatial frequency “Stil-300” when it is far from the peak. “There is a signal change compared with the case where the AF extraction frequency adjusted to Hz is high, so the detection of the in-focus position from the blurred state is easy to understand, and therefore the responsiveness deteriorates. Similarly, the peak position width near the peak The frequency characteristics of fixed AF signals that are fixed, such as overshooting the peak position due to the narrowness, causing problems such as lack of stability. It is not possible to obtain a result.
In addition, the performance of the lens varies depending on the focal length, the focus position, and the aperture, and these are also factors for changing the resolution of the lens.

Therefore, the frequency characteristics necessary for AF change from the state of the lens depending on each state. For example, as for the focal length, as shown in FIG. 9, the spatial frequency to be resolved differs between wide and tele. In general, since the subject image is finer than that of tele at wide, the spatial frequency to be resolved is higher than that of tele. With the recent increase in zoom magnification, the difference in spatial frequency between the wide end and the tele end tends to increase.
In FIG. 9, it is assumed that there is a lens with a spatial frequency of 3 MHz for resolution at wide and 0.5 MHz for tele. In this case, the frequency characteristics required for AF need to be higher than that of tele, and high frequency characteristics necessary for tele are not required. If the frequency required for tele is set, the AF result is likely to be out of focus in the wide range.
FIG. 6 shows the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position, and the peak position width when the extraction frequency is high compared to the peak position width when the extraction frequency is low. This is because, in this example, the peak signal is not necessarily the wide peak position as the AF extraction frequency characteristic at the spatial frequency resolved by tele. On the other hand, when AF is performed with the telescope set to a wide required frequency, there is a problem that it takes more time and is not stable than when telescope is used to detect the responsiveness from blur and the peak position near the focus. appear.
As shown in FIG. 6, since the signal peak rises sharply, the spatial frequency is adjusted to be wide when it is far from the peak as compared with the case where the spatial frequency at the low spatial frequency is set to the AF frequency characteristic. Since the signal changes more than when the AF frequency characteristics are increased, the detection of the in-focus position from the blurred state is easy to understand, and as a result, the responsiveness deteriorates, and similarly the peak position width is narrow near the peak. For this reason, it is impossible to obtain an optimum result for each of the fixed frequency characteristics of a predetermined AF signal, such as overshooting the peak position or problems such as lack of stability.
The resolving power of the lens changes depending on the stop.

As shown in FIG. 10, the spatial frequency to be resolved differs depending on the FNo of the stop, and the required frequency near the open position and the required frequency near the stop are different. For example, it is assumed that there is an aperture that can change from F number 2 to 32.
As shown in FIG. 10, when the spatial frequency to be resolved at F2 is 2 MHz, F8 is 3.5 MHz, and F16 is 1 MHz, the frequency characteristics required for AF are higher than F2 and F16 in F8. Further, F16 does not require the high frequency characteristics necessary for F2 and F8. If the required frequency of F16 is set, it is likely that the AF result will be out of focus in F2 or F8.
FIG. 6 shows the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position, and the peak position width when the extraction frequency is high compared to the peak position width when the extraction frequency is low. This is because, in this example, the signal at the peak is not necessarily the peak position at F8 or F2 even in the frequency characteristic of AF at the spatial frequency resolved at F16 in this example. On the other hand, when AF is performed with F2 or F16 with the required frequency set to F8, F2 is set for F2 and F16 is set for F16 for detecting responsiveness from blur and peak position near the focus. Problems such as time consuming and unstable.
As shown in FIG. 6, since the signal peak rises steeply, if the spatial frequency at F16, which has a low spatial frequency, is set to the AF frequency characteristic, the AF extraction frequency is adjusted to the spatial frequency F8 when it is far from the peak. Since there is a signal change compared to when the value is increased, the detection of the in-focus position from the blurred state is easy to understand, and as a result, the responsiveness deteriorates. With the fixed frequency characteristics of the predetermined AF signal, such as shooting and problems such as lack of stability, optimal results for each cannot be obtained.
Furthermore, the resolving power of the lens may change depending on the focus position.

FIG. 11 is an example in which the spatial frequency to be resolved at the focus position is different. It is assumed that the spatial frequency to be resolved at the infinite end is 3 MHz and there is a 1.5 MHz lens at the closest end. In this case, the frequency characteristic required for AF needs to be higher at the infinite end than at the close end, and the high frequency characteristic required at the infinite end is not required at the close end. If the required frequency at the closest end is set, the AF result at the infinite end is likely to be out of focus.
FIG. 6 shows the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position, and the peak position width when the extraction frequency is high compared to the peak position width when the extraction frequency is low. This is because, in this example, the signal at the peak is not necessarily the peak position at the infinite end as the frequency characteristic of the AF at the spatial frequency to be resolved at the closest end in this example. Conversely, when AF is performed at the near end by setting the required frequency at the infinite end, it takes more time than when it is set for the near end to detect the peak position near the focus and the response from blur, Problems such as instability occur.
As shown in FIG. 6, since the signal peak rises steeply, if the spatial frequency at the close end where the spatial frequency is low is set as the AF extraction frequency, the AF is matched to the infinite end of the spatial frequency when moving away from the peak. Since there is a signal change compared with the case where the frequency characteristic is high, the detection of the in-focus position from the blurred state is easy to understand, so that the responsiveness deteriorates, and similarly, the peak position width is narrow near the peak. With the fixed frequency characteristics of a predetermined AF signal, such as problems such as overshooting the position and lack of stability, it is not possible to obtain an optimum result for each.
In addition, as described above, the camera's imaging state, such as the camera's still and moving images, the number of pixels, and the compression ratio, the necessary AF resolution, the lens focal length, aperture, focus, etc. If the spatial frequency characteristics for resolving the required AF are obtained from the lens state, compare them, for example, when the frequency from the imaging state of the camera is higher than the necessary frequency characteristic from the lens state, Even if AF is performed at the frequency from the camera imaging state, the lens does not need to have frequency characteristics up to its height, but compared to the case where AF is performed at the required frequency characteristic from the lens state. , It takes time to focus and there is a problem that it is not stable.
In addition, when the frequency from the imaging state of the camera is lower than the necessary frequency characteristic from the lens state, even if AF is performed with the necessary frequency characteristic from the lens state, the camera will have the number of frequencies up to that height. Not only is the characteristic not necessary, but there is a problem that it takes time to focus and is not stable as compared with the case where AF is performed at a frequency from the imaging state of the camera.

As shown in FIG. 6, since the signal peak rises steeply, if the extraction frequency with the lower extraction frequency is set to the AF extraction frequency, AF extraction is performed in accordance with the higher extraction frequency when moving away from the peak. Since there is a signal change compared to when the frequency is increased, the detection of the in-focus position from the blurred state is easy to understand.Therefore, the responsiveness deteriorates, and similarly, the peak position is narrow because the peak position width is narrow near the peak. The frequency may be set higher than necessary due to problems such as overshoot and lack of stability.
As described above, when the resolution frequency is high, the minimum driveable pitch must be fine under the same optical conditions. On the other hand, when the frequency is low, the above problem occurs even if the drive pitch is finer than necessary. The following issues describe the issues arising from differences in spatial frequency depending on the state of each lens and camera in the interchangeable lens system.
Depending on the type of lens and the state of the lens, the camera mounted in this way has various resolutions and the minimum amount that can be driven or driven depending on the type of camera and the shooting state of the camera. The problem was stated.
Therefore, the present invention is not limited to the case where the out-of-focus blur can be recognized, the responsiveness deteriorates, the camera overshoots, or lacks stability. An object of the present invention is to provide a photographing apparatus capable of realizing good autofocusing performance even in the combination and photographing state.

In order to achieve the above object, a photographing apparatus according to a first aspect of the present invention includes an interchangeable lens that forms a subject image and has identification information;
Imaging means for picking up an image formed by the lens, and focus detection means for converting the image into an electric signal, extracting a predetermined frequency from the electric signal, and detecting a degree of focus of the image. And having a camera unit,
The minimum drive pitch of the interchangeable lens is changed according to the identification information of the camera,
Alternatively, the minimum drive pitch of the interchangeable lens is changed according to spatial frequency information resolved by the camera,
Alternatively, the minimum drive pitch of the interchangeable lens is changed according to the information of the camera,
Alternatively, the minimum driving pitch of the interchangeable lens is changed according to the information of the lens,
Alternatively, the minimum driving pitch of the interchangeable lens is changed according to the information on the camera and the information on the lens.

Furthermore, the imaging device of the second aspect of the present invention includes an interchangeable lens that forms a subject image and performs imaging.
A camera having an image pickup means for picking up an image formed by the lens;
Focus detection means for detecting the degree of focus of the captured image;
A focus adjusting means for performing focus adjustment;
An automatic focus adjustment unit that automatically adjusts the focus by controlling the output of the focus detection unit and the focus adjustment unit;
The camera changes the frequency extracted by the focus detection means from the minimum driving focus movement amount of the interchangeable lens,
Or
The camera changes the frequency extracted by the focus detection unit from the minimum driving focus movement amount that is variable according to the information of the interchangeable lens,
Or
The camera is characterized in that the frequency extracted by the focus detection unit is changed based on a minimum driving focus movement amount variable according to lens information of the interchangeable lens and a shooting state of the camera.

Furthermore, an imaging device according to a third aspect of the present invention includes an interchangeable lens that forms a subject image and performs imaging.
A camera having an image pickup means for picking up an image formed by the lens;
Focus detection means for detecting the degree of focus of the captured image;
A focus adjusting means for performing focus adjustment;
An automatic focus adjustment unit that automatically adjusts the focus by controlling the output of the focus detection unit and the focus adjustment unit;
Having a spatial frequency detection function for obtaining a spatial frequency to be resolved from information of the interchangeable lens;
The camera has a spatial frequency detection function for obtaining a spatial frequency to be resolved from the imaging state of the imaging means,
The focus detection unit is capable of changing a frequency to be extracted, and compares the spatial frequency resolved by the optical system with the spatial frequency resolved by the imaging unit, and the focus is detected from the lower spatial frequency resolved. Change the frequency extracted by the detection means and the minimum driving amount of the interchangeable lens,
Or
The focus detection unit can change a frequency to be extracted, and compares a spatial frequency resolved by the optical system with a spatial frequency resolved by the imaging unit, and determines a lower spatial frequency to be resolved. The frequency extracted by the detecting means and the minimum driving amount of the interchangeable lens are used.

According to the photographing apparatus of the present invention, the replaceable lens has the automatic focusing means, and the minimum drive pitch of the replaceable lens is changed according to the identification information of the camera,
Alternatively, the interchangeable lens has the automatic focusing means, and the minimum driving pitch of the interchangeable lens is changed according to spatial frequency information resolved by the camera.
Further, the camera changes the frequency extracted by the focus detection means from the minimum drive focus movement amount of the interchangeable lens,
Or
The camera changes the frequency extracted by the focus detection means from the minimum driving focus movement amount that varies depending on the lens state of the interchangeable lens,
Or
The camera is characterized in that the frequency extracted by the focus detection means is changed based on a minimum driving focus movement amount that varies depending on a lens state of the interchangeable lens and a photographing state of the camera.
Further, the interchangeable lens and the camera each have communication means for communicating,
The camera communicates the frequency extracted by the focus detection means to the interchangeable lens.
The interchangeable lens has a spatial frequency detection function for obtaining a spatial frequency resolved from the optical information of the optical system,
The camera has a spatial frequency detection function for obtaining a spatial frequency to be resolved from the imaging state of the imaging means,
The focus detection unit is capable of changing a frequency to be extracted, and compares the spatial frequency resolved by the optical system with the spatial frequency resolved by the imaging unit, and the focus is detected from the lower spatial frequency resolved. Change the frequency extracted by the detection means and the minimum driving amount of the interchangeable lens,
Or
The focus detection unit can change a frequency to be extracted, and compares a spatial frequency resolved by the optical system with a spatial frequency resolved by the imaging unit, and determines a lower spatial frequency to be resolved. The frequency extracted by the detection means and the minimum driving amount of the interchangeable lens are used.
With the above configuration, when an out-of-focus blur can be recognized, when responsiveness deteriorates, overshoots, or lacks stability, any interchangeable lens, its lens state, and camera Good autofocusing performance can be achieved even in combination and shooting conditions.

  Hereinafter, the present invention will be described with reference to the drawings based on the embodiments.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a schematic block diagram of an embodiment of the present invention.
A lens unit 200 that is an interchangeable lens is attached to and detached from the camera unit 201 via a lens mount 201a and a camera mount 202a.
Light from the subject passes through the fixed first lens group 10, the variable magnification lens 12, the stop 14, the fixed third lens group 16, and the focusing lens 18, and then the imaging surface of the imaging device 20. Incident on the (photoelectric conversion surface). The image sensor 20 converts an optical image on the imaging surface into an electric signal. The output signal of the image sensor 20 is sampled and held by the CDS circuit 22, amplified to a predetermined level by the AGC circuit 24, and converted into a digital signal by the A / D converter 26. The output signal of the A / D converter 26 is supplied to a camera signal processing circuit (not shown).
The output of the A / D converter 26 is input to the AF preprocess circuit 28. The AF preprocess circuit 28 generates an AF evaluation value and supplies it to a camera main control circuit 31 composed of a microcomputer, details of which will be described later. The main control circuit 31 takes in the output (AF evaluation value) of the AF preprocess circuit 28 and outputs it to the lens main control circuit 30 through communication via the camera mount and the lens mount. The lens main control circuit 30 determines the focusing speed according to the degree of focus and the motor drive direction in which the AF evaluation value increases, and controls the motor drive circuit 32. The motor drive circuit 32 drives the focus motor 34 in accordance with a command from the main control circuit 31, and moves the focusing lens 18 to a designated position at a designated speed. Thereby, the focusing lens 18 is controlled to a position where the AF evaluation value becomes maximum.
The lens main control circuit 30 also rotates the zoom motor 38 by the motor drive circuit 36 according to the user's magnification operation, and moves the magnification lens 12 to a designated position. Thereby, the focal length can be changed, and the photographing magnification changes.

FIG. 2 shows a schematic block diagram of an example of the AF preprocess circuit 28, and FIG. 3 is an explanatory diagram of a focus detection area in the screen and a pixel configuration in the focus detection area. A focus detection area 56 is set in the screen 54 of one frame or one field. The focus detection area 56 includes a plurality of horizontal lines 58, and each horizontal line 58 includes a plurality of pixels 60.
This will be described with reference to FIG. The line memory 40 stores pixel data P0, P1,..., Pn of one horizontal line in the focus detection area 56 from the output data of the A / D converter 26. A discrete cosine transform (DCT) circuit 42 orthogonally transforms image data of one horizontal line stored in the line memory 40, and outputs frequency domain data F0, F1,. The weighting circuit 44 multiplies the output of the DCT circuit 42 by predetermined constants K0 to Kn so that each frequency component has a substantially uniform level. That is, the weighting circuit 44 outputs k0 × P0, K1 × P1,..., And Kn × Pn.
The predetermined frequency component extraction circuit 46 extracts and outputs only the component commanded by the main control circuit 30 from the outputs k0 × P0, K1 × P1,..., And Kn × Pn of the weighting circuit 44. The line peak hold circuit 48 holds the maximum value of the output for one line output from the predetermined frequency component extraction circuit 46, and updates the hold value for each horizontal line with the maximum value of the next horizontal line. To do.
The adder 50 and the register 52 constitute an accumulator. This accumulator functions as an integration circuit in the vertical direction, and cumulatively adds the outputs of the line peak hold circuit 48. That is, initially, the register 52 is set to zero. The adder 50 adds the output of the register 52 to the output of the line peak hold circuit 48 and writes the addition result in the register 52. By executing this operation for all horizontal lines 58 in the focus detection area 56, the accumulated value of the maximum value of the predetermined frequency components of all the horizontal lines 58 in the focus detection area is stored in the register 52. The stored value of the register 52 is supplied to the main control circuit 30 as an AF evaluation value.

FIG. 4 shows an example of data transition in the line memory 40, the DCT circuit 42, the weighting circuit 46, and the predetermined frequency component extraction circuit 46. 4A shows a data string stored in the line memory 40, FIG. 4B shows a data string output from the DCT circuit 42, and FIG. 4C shows an output data string of the weighting circuit 42.
4D, 4E, and 4F are output examples of the predetermined frequency component extraction circuit 46. FIG. In the outputs F0 to Fn of the DCT circuit 42, F0 is the lowest frequency component near the DC component, the frequency gradually increases in the order of F1, F2,..., And Fn becomes the highest frequency component.
The camera main control circuit 31 sends a camera identification signal to the lens main control circuit 30 by communication. This is not particularly limited as long as it is identifiable information such as a predetermined number or information indicating camera specifications.
In the present invention, the lens can change the driving amount for AF by the camera's identification signal.
For example, there are a plurality of types of cameras that can be exchanged and have different recording methods and shooting methods such as NTSC and Hi-Vision, and when performing AF in these, if the AF suitable for each camera is known in advance, from the camera identification information AF corresponding to each is performed.
As a result, it is possible to realize good AF with any combination.

FIG. 12 shows the flow. In S1201, the camera main control circuit 31 transmits identification information to the lens. In S1202, the minimum focus driving pitch is determined from the camera identification information, and determined in S1203.
With this function, even when the frequency extracted from the video signal is different when performing AF, it is possible to easily cope with it, and good AF can be performed.
If the frequency to be extracted is low and the drive pitch is fine, as shown in FIG. 6, since the signal change near the focus peak is small, it is difficult to detect the peak position, and blurring tends to remain.
On the other hand, when the frequency to be extracted is high, there is a problem that the response from blurring becomes dull because there is little signal change at the time of blurring, and this embodiment can solve this problem in any combination of camera and lens.
In step S1203, the minimum drive pitch can be obtained by taking into account the F value, the focal length, the focus position, the combination thereof, and the resolution information obtained from them.
The information from the camera is not only the identification information but also the above-mentioned moving image or still image, the television system such as NTSC or Hi-Vision, or the shooting state such as the recording pixel, density, compression rate, etc., as information from the camera. Needless to say. It can be obtained from information such as recording pixels, density, compression rate, etc., or a combination of still images for still images, moving images for moving images, NTSC for NTSC, and high-definition for high-definition images. Therefore, it is possible to cope with various recording formats, shooting conditions, and shooting conditions. It can be inferred that this is an epoch-making technique that eliminates boundaries such as video cameras and single-lens reflex cameras at once. In addition, since there is a high possibility that it will be possible to respond to unexpected future camera shooting and environmental changes such as the appearance of recording media called next generation media, shooting methods, compression methods, etc., lenses have been released in advance. Even if the camera is to be released later, it is possible to fully demonstrate the performance of the latest camera without being bound by a system that supports only the conventional method. Accordingly, it goes without saying that the lens drive pitch range is desired to be as wide as possible. In other words, it is an important matter that the lens can be driven at a resolution higher than the required resolution of the system at the time of lens sale or has a driving pitch at the minimum driving resolution required for optical performance. Needless to say.
The minimum drive pitch at the time of AF has been described above, but it has a manual focus function (not shown), and the minimum drive pitch that becomes the minimum resolution of manual focus drive can be changed according to the above-described camera information and lens status. Can be easily imagined. Since the resolution is too fine than necessary, it is difficult to understand the change in focus, or on the contrary, it is too coarse to exceed the focus peak, and it is easy to imagine the occurrence of problems that can not be stopped from the above explanation. Needless to say, it is effective in solving these problems.
The minimum drive pitch is a minimum unit drive amount, and may be defined as a minimum drive amount per unit time. As a result, an optimum focus operation can always be realized during manual focus.

Next, Example 2 of the present invention will be described.
In the present invention, a spatial frequency to be resolved is obtained by taking into account a lens state and a photographing state, and a high frequency component band to be extracted from a video signal and a lens driving pitch are obtained. In FIG. 13 for explanation, the same parts as those in FIG.
As shown in FIG. 13, the shooting state detection unit 87 detects shooting states such as still images and moving images, the size of the captured image, the number of pixels, the compression rate, the pixel density, and the like, and is input to the camera main control circuit 31. The The lens state is input to the lens main control circuit 30. For example, even with the same lens and imaging means, the resolvable spatial frequency varies depending on the lens state, shooting mode, and compression rate. Even if the spatial frequency for resolving a still image without compression of 2 million pixels is 10 MHz, if the spatial frequency for resolving when the lens is in the tele end infinite F8 is 0.5 MHZ, AF The video signal may be extracted at a frequency of 0.5 MHz. If the spatial frequency is high and the frequency to be extracted is high, there is a problem that the focus direction at the time of blurring is difficult to find because there is little change in the signal except near the focus peak, and the frequency band of the high-frequency component that is extracted from the video signal for AF Since the signal change at the time of blurring is obtained when the value is lower, the response is better, so it is not desirable to set the extraction frequency higher than necessary. Therefore, the minimum resolution to be driven by the lens may be 0.5 MHz. The drive pitch increases as the depth of focus is deeper in a state such as an aperture, but the amount of vibration increases, but when the depth is shallow near the open position or the like, the focus change per unit drive increases, so the drive amount is reduced. Therefore, this minimum drive requires accuracy when the lens is open. Also, if the spatial frequency to be modified is low, it will not be moved more finely than necessary. Also, from the AF performance, when changing the frequency from which the high-frequency component of the video signal is extracted from the spatial frequency to be modified, it is possible to stop at the peak. However, there is a problem of stopping in the middle of a mountain, and the minimum drive pitch and the frequency to be extracted must be determined in accordance with AF. This is also the gist of the present invention.
Therefore, the spatial frequency to be resolved is determined by taking into account the characteristics of the lens and the state of imaging, and by determining the necessary minimum resolution from the frequency, a lens having any optical performance in any imaging device. Even in combination, the optimum AF can always be performed.

The main control circuits 30 and 31 have a spatial frequency detection function and an extraction frequency determination function, and have extraction frequency determination data in the built-in ROMs 30a and 31a as shown in FIGS. In accordance with the extracted frequency determination data stored in the built-in ROMs 30a, 31a, etc. from the state, the predetermined frequency component extraction circuit 46 determines which band of frequency component data is to be extracted.
For example, when the camera determines the extraction frequency in accordance with an instruction from the lens, a description will be given using the flow of FIG.
In S1601, the camera reads the shooting state and transmits the spatial frequency to be resolved in S1602 or the frequency to be extracted from the video signal to the lens. In S1603, the lens reads the lens state and obtains the spatial frequency to be resolved or obtained in S1604. The frequencies extracted from the video signal obtained therefrom are compared, and in S1605, the lower one is extracted as the frequency to be extracted. In S1606, the camera obtains a signal according to the instruction, and in S1607, the lens obtains the obtained resolution. The minimum drive amount is obtained from the spatial frequency to be determined, and the AF drive amount is determined in consideration of the F value state of the lens.

In addition, the camera may obtain lens information from the lens. In the flow of FIG. 17, the lens main control circuit 30 reads the lens state in S1701, and extracts it from the spatial frequency or video signal to be resolved in the lens state in S1702. Frequency information to be transmitted is transmitted to the camera main control circuit 31 in S1703. The camera main control circuit 31 reads the shooting state in S1704, and detects the spatial frequency resolved from the shooting state or the frequency extracted from the video signal in S1705. Compared with the information from the lens state obtained in S1703, a signal may be obtained as a frequency for extracting those low ones in S1706.
Alternatively, the automatic focusing means can be easily applied to a so-called single-lens reflex type camera in which AF driving information such as speed, direction, and driving amount is communicated to the lens and AF is performed.

18, the lens main control circuit 30 reads the lens state in S1801, acquires the spatial frequency to be resolved in the lens state or the frequency information extracted from the video signal in S1802, and the camera main control circuit 31 in S1803. In step S1804, the camera main control circuit 31 reads the shooting state, detects the spatial frequency resolved from the shooting state or the frequency extracted from the video signal in step S1805, and compares it with the information from the lens state obtained in step S1803. In S1806, signals are obtained as frequencies for extracting those low ones, and AF is performed.
In any case, the extracted frequency determination data includes the lens information and the spatial frequency to be resolved in the shooting state, and has a spatial frequency detection function and an extraction frequency determination function to detect and obtain the spatial frequency to be resolved from the current shooting state. It outputs to the predetermined frequency component extraction circuit 46 so that the band containing the frequency may be selected. The frequency band to be selected may be the spatial frequency itself of this lens. Needless to say, if the upper and lower limits are exceeded, the upper and lower limits are set.
For example, when the lens information is wide end, F8, infinite end, the shooting state is moving image, and NTSC, if 5 MHz is obtained from the lens information and 3 MHz is obtained from the imaging state, the resolution frequency is 3 MHz because 3 MHz <5 MHz. Desired.
Therefore, in this case, the predetermined frequency component extraction circuit 46 is instructed to extract a frequency band of 3 MHz. The spatial frequency to be resolved at this time is not a resolution limit frequency but a sufficient frequency of MTF, for example, about 80% of the resolution limit frequency.
By doing so, in the above example, the AF result in the lens information + imaging state is not the AF in the frequency band lower than the spatial frequency in which only the imaging state is resolved, but the spatial frequency in which the lens information + imaging information is resolved. Since they are combined, it will not be possible to recognize out-of-focus.

FIG. 6 shows the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position, and the peak position width when the extraction frequency is high compared to the peak position width when the extraction frequency is low. This is because in this example, the peak signal is not necessarily the peak position in the lens information + imaging information as the AF frequency characteristics at the spatial frequency resolved by tele in this example. This problem can be solved by setting the + imaging information to the lens information and the frequency extracted to the spatial frequency at which the imaging information is resolved.
Also, in this case, by specifying the frequency band to be extracted according to the resolution of lens information + imaging information resolution, it is set for lens information to detect responsiveness from blur and peak position detection near the focus. The problem that it takes more time and is not stable can be solved.
In the case of shooting with compression with a low extraction frequency as shown in FIG. 6, when the frequency corresponding to the frequency of non-compression shooting with a high extraction frequency is extracted, the signal peak rises sharply, so that the imaging state has a low spatial frequency. Compared to the case where the spatial frequency alone is set to the AF frequency characteristic, there is a signal change when the spatial frequency is away from the peak compared to the case where the spatial frequency is made higher than the case where the AF frequency characteristic is increased in accordance with non-compression shooting. In-focus position detection is easy to understand, so the responsiveness deteriorates.Similarly, the peak position width is narrow near the peak, causing problems such as overshooting the peak position and lack of stability. However, this problem can be solved by setting the frequency to be extracted according to the lower of the spatial frequency to resolve the lens information + imaging information. .

It is a schematic block diagram of Example 1 of the present invention. It is a schematic block diagram of an example of an AF preprocess circuit. It is explanatory drawing of the pixel structure in the focus detection area in a screen, and a focus detection area. 4 is a data characteristic diagram in the line memory 40, the DCT circuit 42, the weighting circuit 46, and the predetermined frequency component extraction circuit 46. FIG. It is an extraction frequency characteristic view of a high frequency component detected from a video signal. FIG. 6 is a relationship diagram between the output of a high-frequency component signal of AF and the focus position when the extraction frequency is high. It is a comparison diagram of the spatial frequency characteristics resolved by NTSC and the spatial frequency resolved when recording with high pixels and high density during still image shooting. It is a frequency characteristic figure of the spatial frequency which AF resolves. It is a spatial frequency characteristic diagram which resolves wide and tele. It is a spatial frequency characteristic figure resolved by FNo of a stop. It is a spatial frequency characteristic diagram to be resolved at the focus position. It is an operation | movement flowchart of Example 1 of this invention. It is a schematic block diagram of Example 2 of this invention. It is explanatory drawing of the main control circuit which comprises Example 2 of this invention. It is explanatory drawing of the main control circuit which comprises Example 2 of this invention. It is an operation | movement flowchart of Example 2 of this invention. It is an operation | movement flowchart of Example 2 of this invention. It is an operation | movement flowchart of Example 2 of this invention. It is a block diagram of the automatic focus adjustment apparatus of the mountain climbing system of a prior art example. It is a flowchart of the automatic focus adjustment operation | movement by the main control circuit of the hill-climbing control system of a prior art example.

Explanation of symbols

10: First lens group, 12: Variable magnification lens, 14: Aperture, 16: Third lens group, 18: Focusing lens, 20: Image sensor, 22: CDS circuit, 24: AGC circuit, 26: A / D Converter: 28: AF preprocess circuit, 30: Lens main control circuit, 31: Camera main control circuit, 200: Lens unit, 201a: Lens mount, 201: Camera unit, 202a: Camera mount

Claims (8)

Form a subject image,
An interchangeable lens having identification information;
Imaging means for picking up an image formed by the lens, and focus detection means for converting the image into an electric signal, extracting a predetermined frequency from the electric signal, and detecting a degree of focus of the image. And having a camera unit,
The minimum drive pitch of the interchangeable lens is changed according to the identification information of the camera,
Alternatively, the minimum drive pitch of the interchangeable lens is changed according to spatial frequency information resolved by the camera,
Alternatively, the minimum drive pitch of the interchangeable lens is changed according to the information of the camera,
Alternatively, the minimum driving pitch of the interchangeable lens is changed according to the information of the lens,
Alternatively, the minimum driving pitch of the interchangeable lens is changed according to the information on the camera and the information on the lens. An interchangeable lens that forms and captures a subject image;
A camera having an image pickup means for picking up an image formed by the lens;
Focus detection means for detecting the degree of focus of the captured image;
A focus adjusting means for performing focus adjustment;
An automatic focus adjustment unit that automatically adjusts the focus by controlling the output of the focus detection unit and the focus adjustment unit;
The camera changes the frequency extracted by the focus detection means from the minimum driving focus movement amount of the interchangeable lens,
Or
The camera changes the frequency extracted by the focus detection unit from the minimum driving focus movement amount that is variable according to the information of the interchangeable lens,
Or
The imaging apparatus, wherein the camera changes a frequency extracted by the focus detection unit from a minimum driving focus movement amount variable according to lens information of the interchangeable lens and an imaging state of the camera. Form a subject image,
An interchangeable lens for imaging;
A camera having an image pickup means for picking up an image formed by the lens;
Focus detection means for detecting the degree of focus of the captured image;
A focus adjusting means for performing focus adjustment;
An automatic focus adjustment unit that automatically adjusts the focus by controlling the output of the focus detection unit and the focus adjustment unit;
Having a spatial frequency detection function for obtaining a spatial frequency to be resolved from information of the interchangeable lens;
The camera has a spatial frequency detection function for obtaining a spatial frequency to be resolved from the imaging state of the imaging means,
The focus detection unit is capable of changing a frequency to be extracted, and compares the spatial frequency resolved by the optical system with the spatial frequency resolved by the imaging unit, and the focus is detected from the lower spatial frequency resolved. Change the frequency extracted by the detection means and the minimum driving amount of the interchangeable lens,
Or
The focus detection unit can change a frequency to be extracted, and compares a spatial frequency resolved by the optical system with a spatial frequency resolved by the imaging unit, and determines a lower spatial frequency to be resolved. An imaging apparatus characterized in that the frequency extracted by the detection means and the minimum drive amount of the interchangeable lens are used.   The imaging apparatus according to claim 1, wherein the lens information is obtained from any of a lens state, focal length information, focus position information, aperture position information, lens resolution information, focal length, focus, and aperture. .   The camera information is any one of the shooting state of the camera, whether it is still image shooting or moving image shooting, imaging density, number of imaging pixels, imaging compression rate, recording density, number of recording pixels, or still 4. The photographing apparatus according to claim 1, wherein the number of recording pixels and the compression rate at the time of image shooting or moving image shooting are the number of recording pixels and the compression rate at the time of still image shooting or moving image shooting.   4. The photographing apparatus according to claim 1, wherein in the interchangeable lens system zoom lens, the information of the lens includes focal length information, and when the focal length is wide, the frequency extracted from the tele has high frequency characteristics. .   The photographing apparatus according to claim 1, wherein the minimum driving pitch when the automatic focusing function is functioned.   The photographing apparatus according to claim 1, further comprising a manual focus adjustment unit, wherein the minimum drive pitch is obtained when the focus is manually adjusted.

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