JP4907956B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus such as a digital camera. Specifically, even when there is an optical axis shift between a plurality of lenses constituting an optical unit, uniform focusing is performed on the entire area of the imaging surface. The present invention relates to an image pickup apparatus that can be obtained.

  Some electronic cameras having a solid-state image sensor such as a CCD that captures light transmitted through a photographing lens employ a focus adjustment method called contrast AF.

  Contrast AF, also called hill-climbing AF, processes the output of the image sensor each time moving the focus lens in small increments, and determines the position where the processing value (which changes according to contrast) reaches the maximum value as the in-focus position Then, the focus lens is set at that position.

  On the other hand, as in the so-called passive method and active method, an external light type AF that measures a subject distance using a subject light beam other than the light transmitted through the photographing lens and drives the focus lens based on the measurement result is also well known.

  In addition, recent lens barrels are increasingly required to be smaller and have a higher magnification, and in order to satisfy these requirements, high-precision assembly accuracy is required. It is widely known that the “alignment process” is performed (for example, see Patent Publication 1). Here, in order to further improve the alignment accuracy, it is desirable that the eccentricity in the vicinity of the center of the optical axis is adjusted most well and the balance of the peripheral resolution is good.

  However, as the lens barrel is downsized and the magnification is increased, high-precision alignment is required. When this alignment process is performed, the number of man-hours increases compared to the case of assembly without the alignment process. Resulting in.

  Therefore, in the alignment process, the lens is adjusted so that the eccentricity of the lens falls within a certain range, and the periphery of the in-focus position (for example, focus lens position information) at the center portion (near the center of the optical axis) When the amount of shift in the in-focus position is detected in advance and when shooting is actually performed, the shift of the in-focus position is performed based on the shift amount set in advance with respect to the in-focus position obtained in the center portion. (Hereinafter referred to as balance shift).

  In addition, in an imaging apparatus that performs optical zoom shooting by extending a lens, a shift amount at each zoom position is set in advance, and a balance shift is performed according to the zoom position at the time of shooting.

  In addition, as a conventional imaging device, when shooting a warped film, a book page, or the like, a plurality of AF areas are set, and the front surface of the subject is determined based on a distance measurement result obtained from the plurality of AF areas. There has also been proposed an imaging device that drives and controls a focus lens so as to be within the depth of field (see, for example, Patent Document 2).

Furthermore, as a conventional imaging device, the focus position of the subject image formed by the imaging lens is adjusted by correcting the focus position based on the field curvature information for each lens in the detachable lens barrel. An imaging apparatus configured to do so has also been proposed (see, for example, Patent Document 3).
JP 2004-309818 A JP-A-8-160291 Japanese Patent Laid-Open No. 2003-121913

  By the way, it is known that the optimum shift amount in the balance shift varies depending on the distance to the subject.

  FIG. 10 shows the relationship between the distance to the subject (the reciprocal of the distance L) and the amount of deviation of the peripheral focusing lens position (focus lens position) with respect to the central portion of the imaging plane. The vertical axis in the figure (the amount of shift of the focus lens position) indicates the focus lens position that is the focal point in the CCD central region and the focus lens that is the focal point in the region around the CCD when shooting a subject with a uniform distance. The position difference is shown. In this example, the movement of the focus lens in the positive direction means focusing on a near subject (hereinafter referred to as a shift toward the near side), and the movement in the negative direction focuses on a far subject. (Hereinafter referred to as a shift to the far side).

  Therefore, at a distance where the amount of shift of the focusing lens position is positive (for example, when the distance to the subject is 0.3 m), shifting from the focusing position of the central area to the near side allows the center and peripheral areas to be shifted. Images with a good balance of resolution can be taken. Further, at a distance where the amount of shift of the focusing lens position is negative (for example, when the distance to the subject is 1.0 m), shifting from the focusing position of the central area to the far side allows the center and peripheral areas to be shifted. Images with a good balance of resolution can be taken.

  However, in any of the conventional imaging devices described above, although the shift amount is switched according to the optical zoom position, the shift amount is not switched depending on the distance to the subject. There is a problem that the focal position cannot be obtained.

  The subject of this invention is providing the imaging device which can perform the optimal balance shift according to the distance with a to-be-photographed object.

In order to solve the above problems, the invention according to claim 1 is directed to a lens system including a focusing lens system that forms a subject image on a predetermined imaging plane, and a subject input via the lens system. An image pickup means for picking up an image and outputting image data; a distance measuring means for measuring a distance from a subject with a region near the central portion of the imaging plane as a target region; and moving the focusing lens An imaging apparatus comprising: a focusing control unit that performs an automatic focusing operation; and a correction unit that corrects the in-focus position with a correction parameter that is set in advance with respect to a deviation amount of the surrounding focusing degree with respect to the target region In this case, as the correction parameter, parameters set according to the distance to the subject and the zoom position are prepared, and the distance measuring unit measures the distance for each region with respect to a plurality of regions in the imaging plane. The line The correction means determines an optimum correction amount according to the distance measured by the distance measuring means with reference to the parameter, and corrects the in-focus position based on the correction amount. The means corrects the in-focus position when the difference between the distance measurement results of the plurality of distance measurement areas is within a predetermined threshold, and the difference between the distance measurement results of the plurality of distance measurement areas is equal to or greater than the predetermined threshold. In some cases, the focus position is not corrected.

According to the above configuration, in the imaging apparatus that corrects a deviation (or a deviation in focus degree) of the distance measurement result between the central portion and the peripheral portion of the imaging surface using a preset correction parameter, the correction is performed. As a parameter, a parameter in which the distance to the subject and the correction amount are associated with each other is prepared, and the correction unit can refer to the parameter to perform an optimal balance shift according to the distance to the subject.
In addition, the correction means does not correct the focus position when the difference between the distance measurement results of the plurality of distance measurement areas is equal to or greater than a predetermined threshold value, and therefore avoids correction to a subject that does not have a balance shift effect. It becomes possible.

  According to a second aspect of the present invention, in the first aspect, the distance measuring unit uses the imaging unit to move the lens system to detect a focus position, and the imaging unit. And a second distance measuring means for detecting the distance to the subject using a photoelectric conversion means different from the above.

  According to the above configuration, the distance measuring means includes the first distance measuring means (CCD-AF) and the second distance measuring means (external AF), so that the focusing generally used in the imaging apparatus is performed. It can be adapted to the control means.

  According to a third aspect of the present invention, in the second aspect, the correction unit determines an optimal correction amount from the correction parameter based on the distance measured by the second distance measurement unit, and the first measurement is performed. It is characterized by correcting the in-focus position obtained by the distance means.

  According to the above configuration, it is possible to adapt to the hybrid AF generally used in the imaging apparatus.

  According to a fourth aspect of the present invention, in the first aspect, the correction unit selects a correction amount corresponding to the distance closest to the measured distance from the distance information of the correction parameter, and sets the focus position. It is characterized by performing correction.

  According to the above configuration, it is possible to perform an optimal balance shift even for a distance that is not included in the correction parameter.

  According to a fifth aspect of the present invention, in the first aspect, the correction unit supplements the measured distance based on distance information of the correction parameter and a shift amount of the focus degree. It is characterized by determining an optimum correction amount.

  According to the above configuration, as in the case of claim 4, it is possible to perform an optimal balance shift even for a distance not included in the correction parameter.

According to a sixth aspect of the present invention, in the first aspect, the imaging apparatus main body includes setting means for selecting and setting a plurality of shooting modes (scene shooting mode, AF mode, etc.), and the correction means is the setting means. When the shooting mode is set to a predetermined mode, the in-focus position is corrected.

According to the above configuration, as in the case of the first aspect , it is possible to avoid correction to a subject having no effect of balance shift.

A seventh aspect of the invention is characterized in that, in the first aspect, the correction means switches the correction amount according to an aperture value.

  According to the above configuration, it is possible to perform a balance shift optimum for the aperture value at the time of shooting.

  According to the present invention, it is possible to realize an imaging apparatus capable of performing an optimal balance shift according to the distance to the subject.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram of a digital camera as an imaging apparatus according to the present invention. In the figure, reference numeral 100 denotes a digital camera. The digital camera 100 includes a lens system 101, a mechanical mechanism 102, a CCD (charge coupled device) 103, a CDS (correlated double sampling) circuit 104, and a variable gain amplifier (AGC amplifier). 105, A / D converter 106, IPP 107, DCT 108, coder 109, MCC 110, SDRAM 111, PC card interface 112, CPU 121, display unit 122, operation unit 123, SG (control signal generation) unit 126, strobe device 127, battery 128 , A DC-DC converter 129, an EEPROM 130, a focus driver 131, a pulse motor 132, a zoom driver 133, a pulse motor 134, a motor driver 135, and an external AF sensor 136. A PC card 150 is detachably attached via the PC card interface 112.

  The lens unit includes a mechanical mechanism 102 including a lens system 101, a diaphragm / filter unit, and the mechanical shutter of the mechanical mechanism 102 performs simultaneous exposure of two fields. The lens system 101 is composed of, for example, a varifocal lens and includes a focus lens system 101a and a zoom lens system 101b that are focusing lenses.

  The focus driver 131 drives the pulse motor 132 according to the control signal supplied from the CPU 121 to move the focus lens system 101a in the optical axis direction. The zoom driver 133 drives the pulse motor 134 according to the control signal supplied from the CPU 121 to move the zoom lens system 101b in the optical axis direction. Further, the motor driver 135 drives the mechanical mechanism 102 in accordance with a control signal supplied from the CPU 121, and sets, for example, an aperture value of the aperture.

  The CCD 103 converts an image input via the lens unit into an electric signal (analog image data). The CDS circuit 104 is a circuit for reducing noise with respect to the CCD type imaging device.

  In addition, the AGC amplifier 105 corrects the level of the signal that has been correlated and sampled by the CDS circuit 104. The gain of the AGC amplifier 105 is set by the CPU 121 when setting data (control voltage) is set in the AGC amplifier 105 via a D / A converter built in the CPU 121. Further, the A / D converter 106 converts analog image data from the CCD 103 input via the AGC amplifier 105 into digital image data. That is, the output signal of the CCD 103 is converted into a digital signal through the CDS circuit 104 and the AGC amplifier 105 and by the A / D converter 106 at an optimum sampling frequency (for example, an integer multiple of the subcarrier frequency of the NTSC signal). Is done.

  Further, an IPP (Image Pre-Processor) 107, a DCT (Discrete Cosine Transform) 108, and a coder (Huffman Encoder / Decoder) 109, which are digital signal processing units, are provided for digital image data input from the A / D converter 106. Various processing, correction, and data processing for image compression / decompression are performed separately for color differences (Cb, Cr) and luminance (Y). The DCT 108 and the coder 109 perform, for example, orthogonal transformation / inverse orthogonal transformation, which is a JPEG-compliant image compression / decompression process, and Huffman coding / decoding, which is a JPEG-compliant image compression / decompression process.

  Further, an MCC (Memory Card Controller) 110 temporarily stores the compressed image and records it on the PC card 150 or reads it from the PC card 150 via the PC card interface 112.

  The CPU 121 uses the RAM as a work area in accordance with a program stored in the ROM, and controls all operations inside the digital camera according to an instruction from the operation unit 123 or an external operation instruction such as a remote controller (not shown). Specifically, the CPU 121 controls an imaging operation, an automatic exposure (AE) operation, an automatic white balance (AWB) adjustment operation, an AF operation, and the like. The above-described operation unit 123 includes a release for an operator to instruct photographing.

  Camera power is input from a battery 128, such as NiCd, nickel metal hydride, or a lithium battery, to the DC-DC converter 129 and supplied into the digital camera.

  The display unit 122 is realized by an LCD, LED, EL, or the like, and displays captured digital image data, decompressed recorded image data, and the like. The operation unit 123 includes a release key for performing a shooting instruction, buttons for performing function selection and other various settings from the outside, and the like. The CPU 121 executes an AF operation or the like when the release key is pressed halfway and RL-1 is turned on, and performs a shooting operation when the release key is fully pressed and RL-2 is turned on. In the EEPROM 130, adjustment data and the like used when the CPU 121 controls the operation of the digital camera are written.

  The above-described digital camera 100 (CPU 121) includes a recording mode in which image data obtained by imaging a subject is recorded on the PC card 150, a display mode in which image data recorded on the PC card 150 is displayed, and captured image data. Is provided directly on the display unit 122.

  The external AF sensor 136 shown in FIG. 1 includes a passive distance measuring sensor, and is used to measure the distance of the subject. FIG. 2 is a diagram showing a schematic configuration of the external AF sensor. The external AF sensor 136 includes a lens 151, photosensor arrays 152a (left sensor) and 152b (right sensor), and an arithmetic circuit (not shown).

  The principle of distance measurement of the external AF sensor 136 will be described with reference to FIGS. In FIG. 2, the distance to the subject is d, the distance between the lens 151 and the photo sensor arrays 152a and 152b is f, the width of the light input to the photo sensor arrays 152a and 152b is X1 and X2, respectively, and the photo into which the light is incident. If the distance between the sensor arrays 152a and 152b is B, the distance d from the front surface of the external AF sensor 136 to the subject can be calculated by triangulation as d = B · f / (X1 + X2).

  FIG. 3 shows subject images of the left and right photosensor arrays 152a and 152b, and the arithmetic circuit integrates the light amounts of the subject images of the photosensor arrays 152a and 152b, and calculates the deviation of the left and right sensor data. The subject distance d is calculated and output to the CPU 121.

  In this embodiment, the operation of detecting the in-focus position using the external AF sensor 136 is referred to as external AF, and the case of detecting the in-focus position using the CCD 103 is referred to as CCD-AF (internal AF). In the CCD-AF, the focus lens system 101a is moved, the AF evaluation value indicating the contrast of the subject according to the image signal output from the CCD 103 is sampled, and the hill-climbing servo with the peak position of the AF evaluation value as the in-focus position. Use the method.

  Next, CCD-AF and balance shift will be described with reference to FIGS.

  In the CCD-AF, an integral value of a high-frequency component or a luminance difference between adjacent pixels is obtained from a video signal obtained for each field or frame of the CCD, and this is used as an AF evaluation value indicating the degree of focus. The AF evaluation value increases when the subject is in focus because the edge portion of the subject is clear, and the AF evaluation value decreases when the subject is out of focus. By sequentially acquiring the AF evaluation values while moving the focus lens, an AF evaluation value curve as shown in FIG. 5 is obtained. At the time of shooting, the lens is stopped with the point where the AF evaluation value is maximized as the focal point. In the CCD-AF, an AF evaluation value is acquired within a preset AF area (see FIG. 4). It is also possible to set a plurality of AF areas as shown in the figure.

  Here, the balance shift adjustment process performed after the assembly process of the apparatus will be described. In addition, it is assumed that, before the balance shift adjustment, adjustment is already performed so that the eccentricity of the lens is within a certain range by the alignment process.

  In this balance shift adjustment step, as shown in FIG. 4, AF areas are set in the left area, the center area, and the right area, respectively, and AF evaluation values are acquired. Here, it is assumed that AF evaluation values as shown in FIG. 5 are obtained for each of the left area, the center area, and the right area. That is, in the left area, the AF evaluation value peaks at a position where the focus pulse position indicating the focus lens extension position is “127” (hereinafter referred to as a focus position), and in the center area and the right area, the focus position is “130”. The AF evaluation value shows a peak.

  In the balance shift adjustment, a shift to a focus position where the resolution of the central area is the best and the peripheral resolution is well balanced is performed. That is, in the example of FIG. 5, “129” can be set as the target focus position, and the shift amount in this case is “−1” focus pulse step.

  By setting the balance shift amount as described above for each zoom position and each distance to the subject, correction parameters as shown in Table 1 are created. In the example of Table 1, a total of 32 shift amount parameters including eight types of distance parameters “L0” to “L7” as distances to the subject and four types of zoom position parameters “Z0” to “Z3” as zoom positions. ("S00" to "S73") is set.

  When this shift parameter indicates a positive value (for example, “+2”), the focus lens is shifted by two steps from the in-focus position obtained by distance measurement in the center area to the far side during actual shooting. Indicates that shooting will be performed. Similarly, when the shift parameter shows a negative value (for example, “−1”), the focus lens is shifted by one step from the in-focus position obtained by the distance measurement in the central area during actual shooting. Indicates that shooting is performed.

  The correction parameters set in the balance shift adjustment are referred to in actual shooting, and an optimum shift amount is selected according to the distance to the subject and the zoom position, and the focus position (focus) at the time of shooting is selected. Position) is corrected. Therefore, an optimum balance shift can be performed even when shooting subjects with different distances.

  The AF area may be set at the four corners of the periphery (upper left, upper right, lower left, lower right) or other area settings. If a plurality of AF areas cannot be set, the center area may be set as an AF area, and the degree of focus in the periphery may be determined visually.

  Next, an operation example related to AF of the digital camera having the above configuration will be described.

  In FIG. 6, first, the CPU 121 sets an external AF area and a CCD-AF area in the central area shown in FIG. 4 (step S10). Then, it is determined whether or not it is the external AF execution timing (step S11). As a result of the determination, if it is not the execution timing of the external AF, the process proceeds to step S13. On the other hand, if the external AF execution timing is reached, a distance measurement process using external AF is executed (step S12), the external AF sensor 136 measures the distance to the subject, and the process proceeds to step S13.

  In step S13, the CPU 121 determines whether the release key is pressed halfway and the RL-1 key is turned on. If RL-1 is not ON, the process returns to step S11, and external AF distance measurement processing is performed at the external AF execution timing until RL-1 is turned ON. On the other hand, if RL-1 is turned on in step S13, the CPU 121 calculates the start position (reference position) of the CCD-AF based on the distance measurement result of the external AF (step S14). Performing AF using external AF and CCD-AF in this way is called hybrid AF. Hybrid AF has an advantage that the distance measurement time is shorter than that of a normal CCD-AF because the CCD-AF is performed near the distance measurement result in the external AF.

  Then, the CPU 121 moves the focus lens system 101a to the calculated CCD-AF start position (reference position) (step S15). Subsequently, after moving the focus lens system 101a to the reference position, the CPU 121 starts the external AF and the CCD-AF simultaneously (step S16). In the external AF, the external AF sensor 136 measures the distance to the subject and detects the in-focus position. In the CCD-AF, the focus lens system 101a is moved in the vicinity of the reference position, the AF evaluation value is acquired, and the focus position is detected. Then, the CPU 121 determines whether or not the external AF and the CCD-AF are finished (step S17), and when the external AF and the CCD-AF are finished, the in-focus position of the CCD-AF is acquired (step S18). ).

  Here, the imaging apparatus of the present embodiment performs a balance shift based on the distance of the subject with respect to the in-focus position as the AF result. Here, first, the CPU 121 acquires the position Z of the zoom lens 101b (step S19). Next, the CPU 121 calculates a distance L to the subject from the external AF result (step S20). The CPU 121 selects an optimal shift amount from the correction parameters shown in Table 1 based on the zoom position Z and the distance L. That is, it is determined whether there is a correction parameter that matches the distance L among the correction parameter distance information L0 to L7 (step S21). If there is a parameter that matches the distance L, the correction parameter is selected ( If there is no parameter that matches the distance L in step S22), the parameter closest to the distance L among the correction parameter distances L0 to L7 is referred to (step S23). Then, the CPU 121 corrects the in-focus position obtained in step S18 using the selected correction parameter (step S24). For example, when the shift amount = 2 step is selected, a target focus position is obtained by adding “2” to the in-focus position (focus position) of the CCD-AF obtained in step S18.

  Thereafter, the CPU 121 moves the focus lens system 101a to the corrected focus position (step S25). Thereafter, when the release key is fully pressed and RL-2 is turned on, a shooting operation is performed, and the image data of the subject is captured and recorded in the PC card 150 (step S26).

  In this embodiment, the distance to the subject is measured using the external AF. However, the distance measurement using the CCD-AF may be performed.

  Next, a second embodiment of the present invention will be described. FIG. 7 shows an operation example related to AF of the digital camera having the above configuration. In the present embodiment, a plurality of areas including a left area, a center area, and a right area shown in FIG. 4 are set as the external AF area, and the distance to the subject is measured for each area. Further, when the distance L to the subject does not exist in the correction parameter, the correction amount is determined by complementation using the correction parameter distances L0 to L7.

  In FIG. 7, first, the CPU 121 sets external AF areas in the left area, center area, and right area shown in FIG. 4 (step S30), and sets a CCD-AF area in the center area shown in FIG. Step S31). Then, it is determined whether or not it is the external AF execution timing (step S32). As a result of the determination, if it is not the execution timing of the external AF, the process proceeds to step S34. On the other hand, if the external AF execution timing is reached, a distance measurement process using external AF is executed (step S33), the external AF sensor 136 measures the distance to the subject, and the process proceeds to step S34. In this embodiment, the distance to the subject is measured for each of the left area, the center area, and the right area in FIG.

  In step S34, the CPU 121 determines whether or not the release key is pressed halfway and the RL-1 key is turned on. If RL-1 is not ON, the process returns to step S32, and external AF distance measurement processing is performed at the external AF execution timing until RL-1 is turned ON. On the other hand, if RL-1 is turned on in step S34, the CPU 121 determines the CCD based on the distance measurement result of the central area that is the same area as the CCD-AF area among the distance measurement results of the external AF. -A start position (reference position) of AF is calculated (step S35).

  Then, the CPU 121 moves the focus lens system 101a to the calculated CCD-AF start position (reference position) (step S36). Subsequently, after moving the focus lens system 101a to the reference position, the CPU 121 starts external AF and CCD-AF simultaneously (step S37). In the external AF, the external AF sensor 136 measures the distance to the subject and detects the in-focus position. In the CCD-AF, the focus lens system 101a is moved in the vicinity of the reference position, the AF evaluation value is acquired, and the focus position is detected. Then, the CPU 121 determines whether or not the external AF and the CCD-AF are finished (step S38), and when the external AF and the CCD-AF are finished, the in-focus position of the CCD-AF is acquired (step S39). ).

  Next, the CPU 121 acquires the position Z of the zoom lens 101b (step S40), and calculates distances Ll, Lc, and Lr to the subject from the external AF result (step S41). That is, the distance to the subject is measured with respect to the left area, the center area, and the right area in FIG.

  Next, the CPU 121 determines whether or not the calculated distances Ll, Lc, and Lr are comparable distances (step S42). If the distances Ll, Lc, and Lr are comparable, the process proceeds to step S43, and if the difference between the distances Ll, Lc, and Lr is equal to or greater than a predetermined threshold, the process proceeds to step S47. That is, when the distances L1, Lc, and Lr are different, the focus lens is moved to the in-focus position of the CCD-AF obtained in step S39 without performing a balance shift. For example, if the balance shift is performed when the person, left area, and right area are the background in the center area, the focus on the person will be reduced, while the balance for the "background" with a different original distance will be reduced. As a result, the shift effect cannot be obtained. Thus, the balance shift is effective for a uniform subject, and it is better not to perform the balance shift for a subject that does not have a uniform distance. That is, by determining whether or not to perform a balance shift based on the distance measurement results of a plurality of AF areas, it is possible to obtain a focus according to the subject.

  On the other hand, if the distances Ll, Lc, and Lr are the same in step S42, the CPU 121 selects an optimum shift amount from the correction parameters shown in Table 1 based on the zoom position Z and the distance Lc of the central area. To do. Here, it is determined whether there is a correction parameter that matches the distance Lc among the correction parameter distance information L0 to L7 (step S43). If there is a parameter that matches the distance Lc, the correction parameter is selected. (Step S44) If there is no parameter that coincides with the distance Lc, the correction parameter distances L0 to L7 are used to calculate the shift amount with respect to the distance Lc by complementation (step S45). The CPU 121 corrects the in-focus position obtained in step S39 using the determined correction parameter (step S46).

  Thereafter, the CPU 121 moves the focus lens system 101a to the corrected focus position (step S47). Thereafter, when the release key is fully pressed and RL-2 is turned on, a shooting operation is performed, and the image data of the subject is captured and recorded in the PC card 150 (step S48).

  In this embodiment, the distance to the subject is measured using the external AF. However, the distance measurement using the CCD-AF may be performed.

  Next, a third embodiment of the present invention will be described. FIG. 8 shows an operation example related to AF of the digital camera having the above configuration.

  In recent years, an imaging apparatus such as a digital camera has a function for selecting and setting scene shooting modes such as a portrait mode, a night view mode, a landscape mode, a sport mode, a snap mode, and a character mode in consideration of user convenience. Even if the user has little knowledge or experience in operating digital cameras, the user can capture and acquire high-quality captured images of the subject corresponding to the selected scene shooting mode by setting the scene shooting mode. It is possible to do.

  For example, in portrait mode, there are many cases where the composition is such that a person is in the center and the surroundings are landscapes, and it is desirable to shoot so that the background is naturally blurred and the person is enhanced. Such a problem in performing the balance shift on the subject is as described in FIG. When the user selects and sets a character mode for shooting, the subject is often a flat surface, and it is desirable to perform shooting with a balanced balance between the center and the periphery. As described above, when the user sets the scene shooting mode and performs shooting, a balance shift suitable for each mode is required.

  The operation of this embodiment will be described below with reference to the flowchart of FIG. The processing from step S50 to step S61 in the figure is the same as the processing from step S30 to step S41 in FIG.

  After calculating the distances Ll, Lc, and Lr to the subject from the external AF result in step S61, the CPU 121 acquires the shooting mode set by the user (step S62). Here, the CPU 121 determines whether or not the shooting mode is the character mode (step S63). If the shooting mode is not the character mode, the process proceeds to step S64 to determine whether or not the shooting mode is the snap mode (step S64). If the shooting mode is not the snap mode, the process proceeds to step S65. Hereinafter, the processing from step S65 to step S71 is the same as the processing from step S42 to step S48 in FIG.

  On the other hand, if the shooting mode is the character mode in step S63, the process proceeds to step S66, and an optimal shift amount is selected from the correction parameters shown in Table 1 based on the zoom position Z and the center area distance Lc (step S66). ). That is, if the shooting mode is the character mode, the subject is expected to be a flat surface, and the distances Ll, Lc, Lr measured for each AF area set in step S50 are the same distances. The shift amount is determined based on the zoom position Z and the distance Lc between the central areas.

  If the shooting mode is the snap mode in step S64, the process proceeds to step S70, and the focus lens system 101a is moved to the in-focus position obtained in step S59 (step S70). That is, when the shooting mode is the snap mode, the selection process of the balance shift amount from step S65 to step S69 is skipped.

  As described above, in this embodiment, since it is determined whether or not the focus position needs to be corrected in the scene shooting mode, it is possible to perform a balance shift optimum for the shooting mode intended by the user.

  Further, the scene shooting mode described in the present embodiment is an example, and the balance shift may be switched depending on other scene shooting modes. For example, in the distant view mode, balance shift may be performed on the assumption that the subject has a certain degree of uniformity, and the subject is a uniform subject not only in the scene shooting mode but also when the AF mode is set to infinity. A balance shift may be performed.

  Next, a fourth embodiment of the present invention will be described. FIG. 9 shows an operation example related to AF of the digital camera having the above configuration. In this embodiment, the balance shift amount is switched according to the aperture value. That is, as the aperture is made smaller (aperture), the depth of field becomes deeper, so that the shift between the focus positions of the center and the periphery on the imaging surface becomes less noticeable. In such a case, the balance shift amount can be set smaller (or not shifted) than when the aperture is large.

  The operation of this embodiment will be described below with reference to the flowchart of FIG. The processing from step S80 to step S95 in the figure is the same as the processing from step S30 to step S45 in FIG.

  The CPU 121 selects an optimal shift amount from the correction parameters in step S94 or step S95, obtains the aperture value F (step S96), and corrects the shift amount based on the aperture value F (step S97). That is, even if the subject distance is the same, the smaller the aperture, the smaller the shift amount (or no shift), and the larger the aperture, the larger the balance amount.

  Then, the CPU 121 moves the focus lens system 101a to the in-focus position corrected based on the shift amount obtained in step S97 (step S99). The following steps are the same as those after step S47 in FIG.

  In this embodiment, the shift amount is corrected based on the aperture value F with respect to the shift amount selected from the correction parameters in Table 1 according to the zoom position Z and the distance Lc. May be a parameter in which the shift amount for each aperture value F is described.

  As described above, by setting the balance shift amount based on the aperture value, it is possible to perform photographing with a good balance of peripheral resolution and excellent center resolution.

It is a block diagram of a digital camera as an imaging apparatus according to the present invention. It is a schematic block diagram of an external AF sensor. It is a figure which shows the to-be-photographed object image of the left and right photosensor arrays. It is a figure which shows the left area, center area, and right area on a CCD image plane. It is a figure which shows the relationship between a focus position and AF evaluation value. 6 is a flowchart illustrating an operation example related to AF of the digital camera according to the first embodiment. 10 is a flowchart illustrating an operation example related to AF of the digital camera according to the second embodiment. 12 is a flowchart illustrating an operation example related to AF of the digital camera according to the third embodiment. 12 is a flowchart illustrating an operation example related to AF of the digital camera according to the fourth embodiment. It is a figure which shows the relationship between a to-be-photographed object distance and the shift | offset | difference of a focus position.

Explanation of symbols

100 Digital camera (imaging device)
101 Lens system 103 CCD (imaging means)
121 CPU (correction means)
131 Focus driver (Focus control means)
134 Pulse motor (focus control means)
136 External AF sensor (ranging means)

Claims (7)

A lens system including a focusing lens system that forms a subject image on a predetermined imaging plane;
Imaging means for imaging a subject image input via the lens system and outputting image data;
Ranging means for measuring the distance from the subject, with the vicinity of at least the central part of the imaging plane as the target area,
A focusing control means for moving the focusing lens to perform an automatic focusing operation;
An imaging apparatus comprising: a correction unit that corrects the in-focus position according to a correction parameter set in advance with respect to a deviation amount of the surrounding in-focus degree with respect to the target region,
As the correction parameter, a parameter set according to the distance to the subject and the zoom position is prepared,
The distance measuring means performs distance measurement for each region for a plurality of regions in the imaging plane,
The correction means refers to the parameter, determines an optimal correction amount according to the distance measured by the distance measurement means, and corrects the in-focus position based on the correction amount,
The correction means corrects the in-focus position when the difference between the distance measurement results of the plurality of distance measurement areas is within a predetermined threshold, and the difference between the distance measurement results of the plurality of distance measurement areas is a predetermined threshold value. An imaging apparatus characterized by not correcting the in-focus position when the above is true.   The distance measuring means uses a first distance measuring means for detecting the in-focus position by moving the lens system using the imaging means, and a distance from the subject using a photoelectric conversion means different from the imaging means. The imaging apparatus according to claim 1, further comprising: a second distance measuring unit that detects the distance. The correction means determines an optimal correction amount from the correction parameter based on the distance measured by the second distance measurement means,
The imaging apparatus according to claim 2, wherein correction is performed on the in-focus position obtained by the first distance measuring unit.   2. The correction unit according to claim 1, wherein the correction unit selects a correction amount corresponding to a distance closest to the measured distance from the distance information of the correction parameter and corrects the in-focus position. Imaging device.   The correction means determines an optimum correction amount by complementing the measured distance based on distance information of the correction parameter and a deviation amount of a focus degree. The imaging apparatus according to 1. The imaging apparatus main body has setting means for selecting and setting a plurality of shooting modes,
The imaging apparatus according to claim 1, wherein the correction unit corrects a focus position when the shooting mode is set to a predetermined mode by the setting unit.   The imaging apparatus according to claim 1, wherein the correction unit switches the correction amount according to an aperture value.

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