JP4574345B2 - Imaging device - Google Patents

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 cameras, high frequency components are extracted from video signals obtained from solid-state image sensors such as CCD image sensors, and the high frequency components are 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 ). Processing content of the camera signal processing circuit, since the present invention are well known unrelated, further explanation is omitted here.
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. number and those selectable, that are also NTSC, have conventional TV system imaging apparatus capable of imaging such high-definition system not only have been devised to spread such PAL in the moving image. For this reason, in the interchangeable lens system, the camera and the lens are improved in image pickup means and resolving power and improved in image quality according to the release date, and are spreading to various forms.
For example, although video recording in the early exchangeable lens system was only standard TV signal, the high-resolution still images and high-definition shooting camera capable and lens than TV signal is developed, it is released new, old camera Lenses are coexisting in the market . In such a case, it is preferable that the combination is compatible, and it is desirable that photographing is possible even in the case of a combination of an HD compatible camera and an old lens designed for a standard TV .

However, in the case of a combination of an HD camera and an old lens designed for a standard TV , the camera is a high-definition high-definition camera , so the spatial frequency to be resolved is high as shown in FIG. extraction frequency characteristic of the high frequency component detected from also that Do as high compared to the conventional TV system. For this reason, a case where appropriate AF cannot be performed without further information may occur . Meanwhile, the lens because it is old lens, on having only resolution for standard TV, sometimes AF system not only includes those for older standard TV is present in the lens.
Because as the focus detection means for performing AF is performed by extracting a high frequency component of the video signal as described above, the frequency of the extracted which is previously fixed by the camera, for example, the aforementioned HDTV focusing signal of the camera in combination with the old lens when it was set for HDTV could that such not intended operation of the AF is suitable for not matching characteristics. Also, when the AF system is present in the lens can not be performed only AF for traditional TV, or no can do proper operation, it is conceivable to not operate in some cases.

The case where the AF operation is not appropriate in the combination of the high-definition camera and the old lens means that the driving amount per unit is not appropriate, and as a result, AF cannot be stopped at the peak of focus. is there. In combination with the high-definition camera and old lenses, high frequency of the signals to be extracted, and the signal is the width of the peak against to narrow ranges that are recognized narrow fried, blurred as compared with the case of NTSC, for NTSC With a lens designed for a wide range of focus peak focus width and out-of- focus blur, the amount of drive per unit is not appropriate, and there is a problem that it cannot stop at the peak position near the true focus. Because. Therefore, even if the spatial frequency if optical resolution corresponded to high definition, in the case of the combination of the present example is the case of AF at the peak of the focus can not be stopped is generated. In addition, when the frequency at which the high-frequency component of the video signal is extracted is higher than NTSC in accordance with the spatial frequency resolved by HDTV, it is difficult to detect the in-focus direction. This is because the deterioration of the signal in the case of blurring away from the peak position is larger at the higher frequency to be extracted than at the lower frequency, as shown in FIG. Further, in the case of an AF system adapted to the conventional NTSC such as this example in which this point is not taken into consideration, there is a possibility that the AF operation is extremely inferior .
That is, when the optical conditions are the same, the minimum drivable pitch must be fine according to the height when the resolution frequency is high .
On the other hand, even finer drive pitch than required if the frequency conversely low problems as described above occur. That is, on the contrary to the above example, when the camera is combined with an old NTSC lens whose lens drives with high-definition pitch for HDTV, the AF signal from the camera is a video signal that matches the frequency resolved by the NTSC. AF is performed by the frequency extracted from the AF, and there is a problem that the AF drive stops in the middle of the peak in the vicinity of the in-focus state. This is because, as shown in FIG. 6, when the focus peak is wide and gentle, and the pitch is fine, no signal change can be obtained even during the focus peak. Even when away from the peak, the driving pitch is fine (the signal change is fine), so there are problems of direction detection accuracy and the problem that the mountain cannot be fully climbed during the above-described mountain climbing operation.
Further, for example, the camera has the ability to record movies in still image and NTSC system, combined when the lens is closed the AF function tailored to NTSC, the focusing signal of the camera to the frequency to be extracted in the NTSC system Rukoto Accordingly, high pixel than the NTSC system in the still image, can be recorded at high density can be assumed.

Figure 7 shows compares the spatial frequency characteristic of resolution of NTSC, high pixel during still image shooting, and a spatial frequency characteristic of resolving the time of high-density recording.
In FIG. 7, it is assumed that the NTSC resolution spatial frequency is NTSC Hz, and that still image shooting is performed with 3 million pixels having a larger number of pixels than the NTSC required spatial frequency. FIG. 7 shows that the spatial frequency “Stil-300” Hz for resolving still image shooting is higher than the spatial frequency for resolution in NTSC (NTSC Hz). Thus, the spatial frequency resolved by NTSC and the spatial frequency resolved by still image shooting are different. Here, the spatial frequency to be resolved is not the limit frequency that can be resolved as shown by the arrows in FIG. 7, but the spatial frequency at which a sufficiently high frequency of MTF is 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 a still image of 3 million pixels is taken as a frequency characteristic for AF focus detection at a spatial frequency “NTSC” Hz that is resolved by NTSC, the focus is blurred due to the difference in resolution limit of the spatial frequency. It may be recognized. This is because a focus peak cannot be detected for a “Still-300” Hz subject, and the stopping position is rough.

FIG. 6 shows the relationship between the output of the AF high-frequency component signal and the focus position when the extraction frequency is high.
Why blurring of the above focus would be recognized, to position the width of the peak when low extraction frequency as is shown in Fig 6, the peak position width when high extraction frequency Ri narrowly, in the case of FIG. This is because even if the signal peaks at “NTSC” Hz, it does not necessarily peak at “Still-300” Hz. On the other hand, in this case, and match the extracted frequency AF for still image shooting can be performed better imaging in focus in the still image shooting but, when recording a movie can not perform good shooting . The reason for this is that, as shown in FIG. 6, since the AF peak is sharper than when the extraction frequency is set for moving images, the filter characteristics at “NTSC” Hz, which has a low spatial frequency, are used. in the case away from the peak, clarity detection of focus position from a blur state due to the presence of large signal change than the extraction frequency of the AF tailored to the spatial frequency "Stil-300" Hz is high because the response is degraded as a result. This is because in the case of the vicinity of the peak, since the peak position width is narrow, problems such as overshooting the peak position and lack of stability occur . Thus, in the frequency characteristic of the fixed, predetermined AF signal, it is impossible to achieve optimal results for each.

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.
Thus the frequency characteristics necessary for AF are also come to change the state of the respective lenses. 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. Difference in spatial frequency resolution of the wide-angle end and the telephoto end in the higher magnification of recent zoom advances are largely ing tendency.
In FIG. 9 , it is assumed that the spatial frequency of resolution of the lens in the wide is 3 MHz and that in the tele is 0.5 MHz. Frequency characteristics necessary for this case the AF that Do and higher than tele wide, but high frequency characteristics is not required required wide at the telephoto. When the frequency required for tele is set, the AF result is likely to be out of focus in the wide range. The reason for this is that, as shown in FIG. 6, the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position is high, the extraction frequency is high relative to the peak position width when the extraction frequency is low. to the the narrower the peak position width case, because even if the signal of the peak as an extraction frequency characteristic of the AF in the spatial frequency resolution on the tele does not always coincide with the peak positions of the wide. If you make an AF in setting the required frequency of the wide-reversed telephoto, it takes longer than setting in tele the peak position detection in the vicinity of the focal responsiveness and engagement from blurring, a problem not stable Will occur. The reason for this is that, as shown in FIG. 6, the rising of the peak of the signal is steep, so when compared with the case where the spatial frequency of tele with a low spatial frequency is set to the AF frequency characteristic, the peak is far from the peak. since the signal variation is larger than the case in which high frequency characteristics of the AF combined spatial frequency wide, clarity detection of focus position from the blur state, because Therefore responsiveness is deteriorated. Further, in the case of the vicinity of the peak, the peak position width is narrow, so that problems such as overshooting the peak position and lack of stability occur . As described above, it is impossible to obtain an optimum result for each of the fixed frequency characteristics of the predetermined AF signal. The resolving power of the lens changes depending on the stop.

Spatial frequency resolution of the lens by FNo diaphragm as shown in FIG. 10 Ru different. In other words, what was different from the required frequency and the required frequency in the vicinity of the narrowing in the vicinity of the opening. Suppose now that there is a squeeze that can vary from F number 2 to 32.
10, the spatial frequency to be resolved in the lens, 3.5 MHz at 2MHz, F8 in F2, when the 1MHz at F16, frequency characteristics necessary for AF are required frequency higher than the F8 F2 and F16, On the other hand, 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. The reason for this is that, as shown in FIG. 6, the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position is high, the extraction frequency is high relative to the peak position width when the extraction frequency is low. This is because the peak position width in this case becomes narrow, and the peak signal does not necessarily coincide with the peak position at F8 or F2 as the AF frequency characteristics at the spatial frequency resolved at F16. Conversely, when AF is performed with F2 or F16 after setting to the required frequency of F8, F2 is used for F2 and F16 is set for F16 for detecting the peak response near the focus and response from blur. The problem is that it takes time and is not stable. The reason for this is that, as shown in FIG. 6, since the rising of the peak of the signal is steep, if the spatial frequency at F16 having a low spatial frequency is set to the frequency characteristic of AF, the spatial frequency F8 is separated from the peak. clarity detection of focus position from a blur state for signal changes than larger when increasing the extraction frequency of the AF to suit, because Therefore responsiveness is deteriorated. Further, in the vicinity of the peak, the peak position width is narrow, so that problems such as overshooting the peak position and lack of stability occur . As described above, it is impossible to obtain an optimum result for each of the fixed frequency characteristics of the predetermined AF signal.

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. In the figure, the spatial frequency resolved by the lens is 3 MHz at the infinite end and 1.5 MHz 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. When set to the required frequency of the near end, if AF results it can recognize defocusing tends to occur at the infinity end. The reason for this is that, as shown in FIG. 6, the relationship between the output of the high-frequency component signal of AF when the extraction frequency is high and the focus position is high, the extraction frequency is high relative to the peak position width when the extraction frequency is low. This is because the peak position width in this case becomes narrower, and the signal of the peak does not necessarily coincide with the peak position at the infinite end even with the AF frequency characteristics having the spatial frequency to be resolved at the closest end. If you make an AF with closest end set to the required frequency of the infinity end the contrary, it takes more time than when set to a closest end to the peak position detection in the vicinity of the focal responsiveness and engagement from blurring The problem that it is not stable occurs. The reason for this is that, 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 to the AF extraction frequency , the spatial frequency is in accordance with the infinity end clarity detection of focus position from a blur state for signal change is greater than when a higher frequency characteristic of the AF, because Therefore responsiveness is deteriorated. Further, in the case of the vicinity of the peak, the peak position width is narrow, so that problems such as overshooting the peak position and lack of stability occur . As described above, it is impossible to obtain an optimum result for each of the fixed frequency characteristics of the predetermined AF signal.
In addition, as described above, when the necessary AF frequency is obtained from the camera imaging state such as the still image and moving image of the camera, the imaging state, the number of pixels, and the compression ratio, the focal length of the lens, the aperture compares the case where the spatial frequency characteristic for resolution states the necessary AF from the lens such as a focus is obtained, higher than the required frequency characteristic of the state of the frequency lens from a camera imaging state of In this case, even if AF is performed at a frequency from the imaging state of the camera, the lens does not need to have frequency characteristics up to its height, but also when AF is performed with the necessary frequency characteristics from the lens state. In comparison, there is a problem that it takes time to focus and is not stable.

In the above, different state amount of frequency and drivable (driven thereby) minimum to resolve the type and lens For lenses in a lens that is mounted, for the camera is resolved by the photographing state of the camera type and camera The frequency and the minimum amount that can be driven (driven) are different, and various problems arising from it are described.
Therefore, the present invention can be applied to various interchangeable lenses, their lens states, and various cameras when the out-of-focus blur can be recognized, or when responsiveness deteriorates, overshoots, and lacks stability. An imaging device capable of realizing good automatic focus adjustment in any combination and any shooting state (still image or moving image, size of image to be captured, number of shooting pixels, shooting compression rate, shooting pixel density, recording density, number of recording pixels, etc.) The purpose is to provide.

Imaging apparatus of the present invention to achieve the above object, an imaging device that converts the interchangeable lens and, imaged the electrical signal image by the interchangeable lens having a focusing lens for adjusting focus, and focus detection means for detecting the degree of focus of the image based on the electrical signal the extracted from the electrical signal to extract a predetermined frequency obtained from the image sensor, based on a detection result of the focus detection means an imaging apparatus having a camera unit having a focus adjustment unit that performs focus adjustment by driving the focusing lens, the interchangeable lens, the spatial frequency of resolving the shooting state of the camera unit camera Based on the lower one of the spatial frequency to be resolved from the shooting state obtained from the camera unit and the spatial frequency to be resolved in the lens state of the interchangeable lens. There are, setting the minimum amount of driving of the focusing lens.

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According to the present invention, when an out-of-focus blur can be recognized, or when responsiveness is deteriorated or lacks stability due to overshoot, various interchangeable lenses, their lens states, and arbitrary combinations with various cameras, and Good autofocus adjustment can be realized in any shooting state (still image or moving image, size of image to be captured, number of shooting pixels, shooting compression rate, shooting pixel density, recording density, number of recording pixels, etc.).

Hereinafter, the present invention will be described based on examples thereof .

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 may be any identifiable information such as a predetermined number or a camera specification . The camera main control circuit 30 obtains a lens identification signal from the communication of the lens main control circuit 31.
In the present invention, when the camera transmits a signal for AF to the lens, the contents can be changed by the identification signal. It will be described to be transmitted to the lens by changing the frequency characteristic for extracting from the video signal in the present embodiment.
For example, interchangeable lens to perform AF is Ri plural kinds Ah, if the AF signal suitable for each if the AF method is different in they are known in advance, outputs the signal to suit each from the identification information of the lens To do. Thus any combination can achieve a good AF.

FIG. 12 shows the flow. In S1201, the camera main control circuit 31 transmits identification information to the lens. In S1202, the driving amount at the time of AF 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. That is, the above problem (when the frequency to be extracted is low, the signal position in the vicinity of the focus peak is small as shown in FIG. 6 so that it is difficult to detect the peak position and blur is likely to remain. On the other hand, the frequency to be extracted is high. In this case, the problem that the response from blurring becomes dull because the signal change at the time of blurring is small can be solved by this embodiment for any camera and lens combination.

Next, a second embodiment of the present invention will be described.
In this embodiment , taking into account the state of the lens and the state of shooting, the spatial frequency to be resolved is obtained and the band of the high frequency component extracted from the video signal is obtained.
As shown in FIG. 13, the shooting state detection unit 87 detects shooting states such as still images and moving images, the size of captured images, the number of pixels, the compression rate, and the pixel density, and each shooting state is controlled by the camera main control. Input to the circuit 30. The lens state is input to the lens main control circuit 31. For example, the same lens, even the imaging device, the state and the photographing mode of the lens, the compression ratio, resolvable spatial frequency also different. If the shooting state is 2 million pixels , no compression, and the spatial frequency to be resolved is 10 MHz, the spatial frequency to be resolved when the lens state is the tele end infinite F8 is 0.5 MHz. The extraction frequency of the video signal for the image may be 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 during blurring is difficult to find because there is little change in the signal except near the focus peak . On the other hand, the high frequency at which the video signal for AF is extracted This is because the lower the frequency band of the components, the better the response, and therefore the extraction frequency should not be set too high .
Therefore, the minimum resolution to be driven by the lens may be 0.5 MHz. For driving the pitch need not be finely driving pitch since the focal depth is deep enough driving amount increases in a state such as diaphragm, focus change per unit driving becomes large when the depth or the like around the opening is shallow Therefore, the drive pitch is made fine. Therefore, the accuracy of the minimum driving amount is required when the lens is opened. In addition, when the spatial frequency to be resolved is low, it should not be made finer than necessary, and it should be fine enough . This is also because the AF performance has the above-described problem that when the frequency at which the high-frequency component of the video signal is extracted is changed from the spatial frequency to be resolved , the peak cannot be stopped and stopped in the middle of the mountain. Thus, it is necessary to determine the minimum drive pitch and the extracted frequency in accordance with AF. This is also the gist of the present invention.
That is, the spatial frequency to be resolved, by obtaining in consideration of characteristics and conditions of the imaging lens, in the camera in any imaging means, also in combination with a lens having any optical information, always it is possible to allow the optimum AF.

The main control circuits 30 and 31 have a spatial frequency detection function and an extraction frequency determination function, and hold extraction frequency determination data in the built-in ROMs 30a and 31a as shown in FIGS. The main control circuit 30 and 31, is determined built from the imaging state and lens state ROM 30a, thus the extraction frequency determination data stored in 31a or the like, whether to extract the frequency component data of which bands in a predetermined frequency component extraction circuit 46 .
For example, for the case where the camera determines the extraction frequency in accordance with an instruction from the lens, it will be described with reference to the flowchart of FIG. 16.
In S1601, the camera reads the shooting state. In S1602, the spatial frequency to be resolved or the frequency to be extracted from the video signal is transmitted to the lens. In S1603, the lens reads the lens state. In S1604, the resolution obtained from S1604. to compare the frequency to be extracted from a video signal obtained from the spatial frequency and S1604, instructs the camera as a frequency to extract the lower of them in S1605, the camera Ru obtain a signal according to the instruction at S1606. In step S1607, the lens obtains the minimum driving amount from the obtained spatial frequency to be resolved, and determines the AF driving amount in consideration of the F value state of the lens.

In addition, the camera but it may also be to obtain a lens information from the lens. For the case of obtaining the lens information from the lens that describes a flow of Figure 17. Lens main control circuit 31 in S1701 reads the lens state, detecting a frequency to be extracted from the spatial frequency or video signal to resolution of the lens state in S1702, it transmits to the camera main control circuit 30 in S1703, the camera in S1704 The main control circuit 30 reads the shooting state, detects the spatial frequency resolved from the shooting state or the frequency extracted from the video signal in S1705, compares it with the information from the lens state obtained in S1703, and lowers them in S1706. Ru resulting signal as a frequency for extracting.

Further, the automatic focusing means can be easily applied to a so-called single-lens reflex type camera that performs AF by communicating AF driving information such as speed, direction, and driving amount to the lens. This will be described with reference to the flow of FIG.
Lens main control circuit 31 in S1801 reads the lens state, detects the frequency information extracted from the spatial frequency or video signal resolution in the lens state in S1802, transmits to the camera main control circuit 30 in S1803, the camera in S1804 the main control circuit 30 reads the shooting condition, compared to information from the lens state obtained in S1803 by detecting a frequency to be extracted from the spatial frequency or video signal resolution from the imaging state at S1805, their low in S1806 performing AF to obtain a signal as a frequency for extracting a thing.
16-18 , 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. A spatial frequency to be imaged is detected , one frequency to be resolved is obtained from the detected information , and the frequency is extracted and output to the predetermined frequency component extraction circuit 46 so as to select a band including the frequency. The frequency band to be selected may be the spatial frequency itself of this lens. Needless to say, when the upper limit is exceeded, the upper limit or lower limit is set.
For example , if the lens information is wide end / F8 / infinite end, the shooting state is moving image, NTSC, and 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. Is required. In this case, to indicate the frequency band to be extracted 3MHz and predetermined frequency component extraction circuit 46. 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.
In the example described above so doing, AF result of the lens information + image pickup state is not AF in a frequency band lower than the spatial frequency to be resolved in the imaging state only spatial frequencies resolution of lens information + imaging information Therefore, there is no inconvenience that the out-of-focus can be recognized.

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. 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 pre-process circuit 30 Lens main control circuit 31 Camera main control circuit 200 Lens unit 201a Lens mount 201 Camera unit 202a Camera mount

Claims (4)

An interchangeable lens having a focusing lens for performing focus adjustment ;
An imaging element that converts an image formed by the interchangeable lens to electrical signals, if the image based on the electrical signal the extracted from the electrical signal to extract a predetermined frequency obtained from the image sensor degree an imaging apparatus comprising: a focus detecting means for detecting, and a camera unit having a focus adjustment unit that performs focus adjustment by driving the focusing lens based on a detection result of the focus detection means,
The interchangeable lens acquires a spatial frequency resolved from the shooting state of the camera unit from the camera unit, and resolves the spatial frequency resolved from the shooting state acquired from the camera unit and the lens state of the interchangeable lens. based on the frequency of the lower of the spatial frequency, imaging device according to feature to set the minimum amount of driving of the focusing lens. An interchangeable lens having a focusing lens for performing focus adjustment;
An image sensor that converts an image formed by the interchangeable lens into an electric signal, and a predetermined frequency is extracted from the electric signal obtained from the image sensor, and the degree of focus of the image is determined based on the extracted electric signal. An imaging apparatus comprising: a focus detection unit that detects; and a camera unit that includes a focus adjustment unit that drives the focusing lens and performs focus adjustment based on a detection result of the focus detection unit,
The interchangeable lens acquires the frequency extracted from the video signal from the camera unit, and the lower one of the frequency extracted from the video signal acquired from the camera unit and the spatial frequency to be resolved in the lens state of the interchangeable lens An imaging device, wherein a minimum driving amount of the focusing lens is set based on the frequency of the focusing lens. An interchangeable lens having a focusing lens for performing focus adjustment;
An image sensor that converts an image formed by the interchangeable lens into an electric signal, and a predetermined frequency is extracted from the electric signal obtained from the image sensor, and the degree of focus of the image is determined based on the extracted electric signal. An imaging apparatus comprising: a focus detection unit that detects; and a camera unit that includes a focus adjustment unit that drives the focusing lens and performs focus adjustment based on a detection result of the focus detection unit,
The camera unit obtains a spatial frequency to be resolved in the lens state of the interchangeable lens from the interchangeable lens, and resolves from the spatial frequency to be resolved in the lens state obtained from the interchangeable lens and the photographing state of the camera unit. An imaging device, wherein a minimum driving amount of the focusing lens is set based on a lower one of the spatial frequencies to be operated. An interchangeable lens having a focusing lens for performing focus adjustment;
An image sensor that converts an image formed by the interchangeable lens into an electric signal, and a predetermined frequency is extracted from the electric signal obtained from the image sensor, and the degree of focus of the image is determined based on the extracted electric signal. An imaging apparatus comprising: a focus detection unit that detects; and a camera unit that includes a focus adjustment unit that drives the focusing lens and performs focus adjustment based on a detection result of the focus detection unit,
The camera unit acquires a spatial frequency to be resolved in the lens state of the interchangeable lens from the interchangeable lens, and out of a spatial frequency to be resolved in the lens state obtained from the interchangeable lens and a frequency extracted from a video signal An imaging apparatus, wherein a minimum driving amount of the focusing lens is set based on a lower frequency.

Images