JP2011043776A - Electronic camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic camera capable of maintaining focusing performance for a field including a light source. <P>SOLUTION: Nine focus areas are allotted to an imaging surface 16f. A CPU 30 repeatedly changes a distance from a focus lens 12 to the imaging surface 16f, and repeatedly detects a high frequency component of a field image captured in each of the nine focus areas, that means, an AF evaluated value. The CPU 30 repeatedly selects one or two or more focus areas being out of a high luminance condition based on luminance information of the field image captured in each of the nine focus areas, and adjusts the distance from the focus lens 12 to the imaging surface 16f to a distance corresponding to a focusing point based on the AF evaluated value detected corresponding to the one or two or more selected focus areas. The focusing performance for the field including the light source is maintained. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electronic camera, and more particularly to an electronic camera that adjusts a distance from a focus lens to an imaging surface to a distance corresponding to a focal point.

  An example of this type of device is disclosed in Patent Document 1. According to this background art, the focus area is divided into a plurality of areas. The focus evaluation value and the photometric value are acquired in the entire area from the nearest to infinity corresponding to each of the divided areas. Further, the maximum value and the minimum value of the photometric values are detected corresponding to each of the divided areas.

  In detecting the in-focus position with reference to the focus evaluation value, an area where the difference between the detected maximum value and minimum value is an allowable value or more is excluded. That is, it is considered that a high-brightness point light source exists in an area where the difference between the maximum value and the minimum value of the photometric value is greater than or equal to the allowable value, and the focus position detection process is performed excluding such an area. The As a result, the in-focus position can be accurately detected even in the field where the point light source exists.

JP 2007-25559 A

  However, in the background art, since the number of areas that can be referred to for the detection of the in-focus position is reduced by excluding the area where the point light source exists, the in-focus performance may be deteriorated.

  Therefore, a main object of the present invention is to provide an electronic camera capable of maintaining a focusing performance with respect to an object field including a light source.

  The electronic camera according to the present invention (10: reference numeral corresponding to the embodiment; the same applies hereinafter) repeatedly changes the distance from the focus lens (12) to the imaging surface (16f) having a plurality of evaluation areas (FB_0 to FB_8). Change means (S31), detection means (S23, S25, S33) for repeatedly detecting high-frequency components of the object scene image captured in each of the plurality of evaluation areas in parallel with the change processing of the change means, multiple evaluation areas The process of selecting one or more evaluation areas out of the high luminance condition from a plurality of evaluation areas based on the luminance information of the object scene image captured in each of the above is repeated in parallel with the changing process of the changing means The selection means (S53 to S65) to be executed, and the distance from the focus lens to the imaging surface is focused based on the high frequency component detected by the detection means corresponding to one or more evaluation areas selected by the selection means Corresponding to Comprise adjusting means for adjusting to a specific distance (S67 ~ S71, S29, S35 ~ S41).

  Preferably, the selection unit includes luminance information detection unit (S53 to S55) for detecting the luminance information of the object scene image captured in each of the plurality of evaluation areas in parallel with the changing process of the changing unit, and luminance information detection Comparing means (S57 to S61) for comparing the luminance information detected by the means with a reference is included.

  More preferably, the luminance information includes, as a parameter, the number of pixels that exhibit a luminance change amount and / or a luminance value exceeding a set value associated with the changing process of the changing means.

  Preferably, the adjustment means extracts extraction means (S69 to S71) for extracting the specific evaluation area where the high frequency component indicating the maximum value is detected from one or more evaluation areas selected by the selection means, and the specific evaluation. Adjustment processing means (S41) is included for executing adjustment processing to a specific distance based on the amount of change in the high-frequency component detected in the area.

  More preferably, the adjustment means further includes an activation control means (S39) that activates the adjustment processing means when the amount of change in the high-frequency component detected in the specific evaluation area exceeds a threshold value.

  The focus control program according to the present invention repeatedly changes the distance from the focus lens (12) to the imaging surface (16f) having a plurality of evaluation areas (FB_0 to FB_8) in the processor (30) of the electronic camera (10). A change step (S31), a detection step (S23, S25, S33) for repeatedly detecting high-frequency components of the object scene image captured in each of the plurality of evaluation areas in parallel with the change process of the change step, a plurality of evaluation areas The process of selecting one or more evaluation areas out of the high luminance condition from a plurality of evaluation areas based on the luminance information of the object scene image captured in each of the above is repeated in parallel with the change process of the change step Imaging from the focus lens based on the selection step (S53 to S65) to be executed and the high-frequency component detected by the detection step corresponding to one or more evaluation areas selected by the selection step Adjustment step of adjusting the distance to a distance corresponding to the focal point for executing (S67 ~ S71, S29, S35 ~ S41), a focus control program.

  The focus control method according to the present invention is a focus control method executed by the electronic camera (10), from the focus lens (12) to the imaging surface (16f) having a plurality of evaluation areas (FB_0 to FB_8). A change step (S31) for repeatedly changing the distance, and a detection step (S23, S25, S33) for repeatedly detecting high-frequency components of the object scene image captured in each of the plurality of evaluation areas in parallel with the change process of the change step. A process of changing the change step is a process of selecting one or more evaluation areas out of the high luminance condition from the plurality of evaluation areas based on the luminance information of the object scene image captured in each of the plurality of evaluation areas. Focus step based on the selection step (S53 to S65) that is repeatedly executed in parallel and the high-frequency component detected by the detection step corresponding to one or more evaluation areas selected by the selection step Adjustment step of adjusting the lens to the distance corresponding to the distance to the imaging surface at a focal point comprising a (S67 ~ S71, S29, S35 ~ S41).

  According to the present invention, the process of selecting one or more evaluation areas that satisfy the high luminance condition is repeatedly executed in parallel with the process of changing the distance from the focus lens to the imaging surface. On the other hand, the spread of the high-luminance portion that appears around the light source differs depending on the degree of focus on the light source. Therefore, when a light source is present in the object scene, one or more evaluation areas to be selected can vary with a change in the distance from the focus lens to the imaging surface. The distance from the focus lens to the imaging surface is adjusted to the distance corresponding to the focal point based on the high-frequency component corresponding to one or more evaluation areas selected in this way. Thereby, it is possible to maintain the focusing performance with respect to the object field including the light source.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is a block diagram which shows the basic composition of this invention. It is a block diagram which shows the structure of one Example of this invention. It is an illustration figure which shows an example of the allocation state of a single photometry area and nine focus areas. FIG. 3 is a block diagram showing an example of a configuration of a focus evaluation circuit applied to the embodiment in FIG. 2; It is an illustration figure which shows an example of a structure of the register | resistor for registering nine AF evaluation values detected corresponding to nine focus areas for every lens position. It is an illustration figure which shows an example of a structure of the register | resistor for registering nine high-intensity count values detected corresponding to nine focus areas for every lens position. It is an illustration figure which shows an example of a structure of the register | resistor for registering nine luminance change rates detected corresponding to nine focus areas for every lens position. It is an illustration figure which shows an example of a structure of the register | resistor for identifying the evaluation area which should be referred for focus adjustment. It is an illustration figure which shows an example of the to-be-photographed field caught by the imaging surface. FIG. 10 is an illustrative view showing a state in which nine focus areas are assigned to the object scene shown in FIG. 9. It is a graph which shows an example of the focusing curve detected in a part of focus area. It is a flowchart which shows a part of operation | movement of CPU applied to the FIG. 2 Example. It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example. FIG. 11 is a flowchart showing still another portion of behavior of the CPU applied to the embodiment in FIG. 2; FIG. 10 is a flowchart showing yet another portion of behavior of the CPU applied to the embodiment in FIG. 2; It is a flowchart which shows a part of other operation | movement of CPU applied to the FIG. 2 Example.

Embodiments of the present invention will be described below with reference to the drawings.
[Basic configuration]

  Referring to FIG. 1, the electronic camera of the present invention is basically configured as follows. The changing unit 1 repeatedly changes the distance from the focus lens 5 to the imaging surface 6 having a plurality of evaluation areas. The detection unit 2 repeatedly detects the high-frequency component of the object scene image captured in each of the plurality of evaluation areas in parallel with the change process of the change unit 1. The selection unit 3 changes the process of selecting one or more evaluation areas out of the high luminance condition from the plurality of evaluation areas based on the luminance information of the object scene image captured in each of the plurality of evaluation areas. It is repeatedly executed in parallel with the changing process of the means 1. The adjusting means 4 corresponds to the focal point the distance from the focus lens 5 to the imaging surface 6 based on the high-frequency component detected by the detecting means 2 corresponding to one or more evaluation areas selected by the selecting means 3. Adjust to the distance you want.

The process of selecting one or more evaluation areas that satisfy the high luminance condition is repeatedly executed in parallel with the process of changing the distance from the focus lens 5 to the imaging surface 6. On the other hand, the spread of the high-luminance portion that appears around the light source differs depending on the degree of focus on the light source. Therefore, when a light source is present in the object scene, the selected one or more evaluation areas may vary with a change in the distance from the focus lens 5 to the imaging surface 6. The distance from the focus lens 5 to the imaging surface 6 is adjusted to the distance corresponding to the focal point based on the high-frequency component corresponding to one or more evaluation areas selected in this way. Thereby, it is possible to maintain the focusing performance with respect to the object field including the light source.
[Example]

  Referring to FIG. 2, the digital camera 10 of this embodiment includes a focus lens 12 and an aperture mechanism 14 driven by drivers 18a and 18b, respectively. The optical image of the object scene that has passed through the focus lens 12 and the diaphragm mechanism 14 is irradiated onto the imaging surface 16f of the imaging device 16 and subjected to photoelectric conversion. As a result, a charge representing the object scene image is generated.

  When the power is turned on, the CPU 30 instructs the driver 18c to repeat the pre-exposure operation and the thinning-out reading operation in order to execute through image processing. In response to a vertical synchronization signal Vsync periodically generated from an SG (Signal Generator) 20, the driver 18c performs pre-exposure on the imaging surface and reads out the charges generated on the imaging surface in a thinning manner. From the imaging device 16, low-resolution raw image data based on the read charges is periodically output in a raster scanning manner.

  The signal processing circuit 22 performs processing such as white balance adjustment, color separation, and YUV conversion on the raw image data output from the imaging device 16, and the YUV format image data thus created is transferred to the SDRAM 34 through the memory control circuit 32. Write. The LCD driver 36 repeatedly reads the image data written in the SDRAM 34 through the memory control circuit 32, and drives the LCD monitor 38 based on the read image data. As a result, a real-time moving image (through image) of the object scene is displayed on the monitor screen.

  Referring to FIG. 3, a photometric area EA is assigned to the center of the imaging surface. The luminance evaluation circuit 24 integrates Y data belonging to the photometry area EA among the Y data output from the signal processing circuit 22 every time the vertical synchronization signal Vsync is generated. The integral value, that is, the luminance evaluation value is output from the luminance evaluation circuit 24 in the generation cycle of the vertical synchronization signal Vsync. In order to calculate an appropriate EV value based on the luminance evaluation value output from the luminance evaluation circuit 24, the CPU 30 repeatedly executes the through image AE process (simple AE process) in parallel with the above through image processing. The aperture amount and the exposure time that define the calculated appropriate EV value are set in the drivers 18b and 18c, respectively. As a result, the brightness of the through image displayed on the LCD monitor 38 is appropriately adjusted.

  When the shutter button 28 s on the key input device 28 is half-pressed, a strict recording AE process is executed in order to calculate the optimum EV value based on the luminance evaluation value output from the luminance evaluation circuit 24. The aperture amount and the exposure time that define the calculated optimal EV value are set in the drivers 18b and 18c, respectively, as described above.

  When the recording AE process is completed, the AF process based on the output of the focus evaluation circuit 26 is executed. The focus evaluation circuit 26 integrates the high-frequency component of Y data belonging to each of the focus areas FB_0 to FB_8 shown in FIG. 3 in the Y data output from the signal processing circuit 22 every time the vertical synchronization signal Vsync is generated. The calculated integral value, that is, the AF evaluation value is registered in the register RGST1.

  The focus evaluation circuit 26 also counts the number of high-luminance pixels (pixels having luminance exceeding the set value) appearing in each of the focus evaluation areas FB_0 to FB_8 every time the vertical synchronization signal Vsync is generated, and the focus evaluation areas FB_0 to FB_0. The luminance change rate of Y data belonging to each of FB_8 is calculated every time the vertical synchronization signal Vsync is generated. The counted number of high luminance pixels, that is, the high luminance count value is registered in the register RGST2, and the calculated luminance change rate is registered in the register RGST3.

  The CPU 30 refers to the description of the registers RGST1 to RGST3 and searches for a position corresponding to the focal point by so-called hill climbing processing. The focus lens 12 is moved stepwise in the direction of the optical axis every time the vertical synchronization signal Vsync is generated, and then placed at the focal point.

  When the shutter button 28s is fully pressed, a recording process is executed. The CPU 30 instructs the driver 18c to execute the main exposure operation and the all pixel reading once. The driver 18c performs main exposure on the imaging surface in response to the generation of the vertical synchronization signal Vsync, and reads out all the charges generated in the charge reading area in a raster scanning manner. As a result, high-resolution raw image data representing the scene is output from the imaging device 16.

  The output raw image data is subjected to the same processing as described above, and as a result, high-resolution image data conforming to the YUV format is secured in the SDRAM 34. The I / F 40 reads out the high-resolution image data thus stored in the SDRAM 34 through the memory control circuit 32 and records the read-out image data in the recording medium 42 in a file format. Note that the through image processing is resumed when high-resolution image data is stored in the SDRAM 34.

  The focus evaluation circuit 26 is configured as shown in FIG. Since the raw image data is output from the imaging device 16 in a raster scanning manner, the Y data is also input to the focus evaluation circuit 26 in a raster scanning manner. The distributor 50 distributes the Y data with reference to the allocation state of the focus areas FB_0 to FB_8 shown in FIG.

  The Y data belonging to the focus areas FB_0, FB_3 and FB_6 is given to the HPF 52, the high luminance counter 64 and the luminance change rate calculation circuit 70. The Y data belonging to the focus areas FB_1, FB_4, and FB_7 is given to the HPF 54, the high luminance counter 66, and the luminance change rate calculation circuit 72. Y data belonging to the focus areas FB_2, FB_5 and FB_8 is given to the HPF 56, the high luminance counter 68 and the luminance change rate calculation circuit 74.

  Each of the HPFs 52, 54 and 56 extracts high frequency components of given Y data. The integrating circuit 58 integrates the high frequency component extracted by the HPF 52 corresponding to each of the focus areas FB_0, FB_3, and FB_6. The integration circuit 60 integrates the high-frequency component extracted by the HPF 54 corresponding to each of the focus areas FB_1, FB_4, and FB_7. The integrating circuit 62 integrates the high frequency component extracted by the HPF 56 corresponding to each of the focus areas FB_2, FB_5, and FB_8. Accordingly, focus evaluation values corresponding to the focus areas FB_0 to FB_8 are detected.

  The high-intensity counter 64 pays attention to each of the focus areas FB_0, FB_3, and FB_6, and counts the number of high-intensity pixels. The high luminance counter 66 pays attention to each of the focus areas FB_1, FB_4, and FB_7, and counts the number of high luminance pixels. The high brightness counter 68 pays attention to each of the focus areas FB_2, FB_5, and FB_8 and counts the number of high brightness pixels. As a result, the high brightness count value corresponding to each of the focus areas FB_0 to FB_8 is detected.

  The luminance change rate calculation circuit 70 calculates the luminance change rate by paying attention to each of the focus areas FB_0, FB_3, and FB_6. The luminance change rate calculation circuit 70 calculates the luminance change rate by paying attention to each of the focus areas FB_1, FB_4, and FB_7. The luminance change rate calculation circuit 70 calculates the luminance change rate by paying attention to each of the focus areas FB_2, FB_5, and FB_8. Thereby, the luminance change rate corresponding to each of the focus areas FB_0 to FB_8 is detected.

  5 to 7, each of registers RGST1 to RGST3 has nine columns corresponding to focus areas FB_0 to FB_8, respectively. Further, when the AF process is executed, the focus lens 12 is disposed at Pmax + 1 positions from the closest end to the infinite end. Based on this, each of the nine columns is divided into Pmax + 1.

  The nine focus evaluation values detected in the focus areas FB_0 to FB_8 are registered in the nine columns of the register RGST1 corresponding to the current position of the focus lens 12. The nine high brightness count values detected in the focus areas FB_0 to FB_8 are registered in nine columns of the register RGST2 corresponding to the current position of the focus lens 12. The nine luminance change rates detected in the focus areas FB_0 to FB_8 are registered in the nine columns of the register RGST3 corresponding to the current position of the focus lens 12.

  In the AF process, first, the focus lens 12 is disposed at the closest end, and the variable P is set to “0”. By the variable P setting process, the writing position of the AF evaluation value in the register RGST1 is designated, the writing position of the luminance change rate in the register RGST2 is designated, and the writing position of the high luminance count value in the register RGST3 is designated. The AF evaluation value is registered at the Pth position of the register RGST1, the luminance change rate is registered at the Pth position of the register RGST2, and the high luminance count value is registered at the Pth position of the register RGST3.

  When the vertical synchronization signal Vsync is generated, the peak detection process focusing on the focusing curves CV_0 to CV_8 respectively corresponding to the focus areas FB_0 to FB_8 is executed as follows. Note that the focusing curve CV_K (K: 0 to 8) corresponds to a curve drawn by the AF evaluation value registered in the Kth column of the register RGST1.

  As a premise, it is assumed that the object scene where the desk light DKL1 having the spherical light source LT1 and the fluorescent lamp FL1 having the linear light source LT2 and the person HM1 exist as shown in FIG. 9 is captured. Here, the desk light DKL1 is located closer to the fluorescent lamp FL1. The focus area FB_6 is assigned to the left side of the light source LT1, the focus area FB_0 is assigned to the left side of the light source LT2, and the focus area FB_4 is assigned to a position that covers the face of the person HM1.

  The focusing curves CV_6, CV_4, and CV_0 respectively corresponding to the focus areas FB_6, FB_4, and FB_0 assigned in this manner change as shown in FIG.

  The high luminance component of the light source LT1 enters the focus area FB_6 in a different manner depending on the defocus amount with respect to the light source LT1. The focusing curve CV_6 rises until the ratio of the high luminance component in the focus area FB_6 reaches a certain value.

  However, when the ratio of the high luminance component exceeds a certain numerical value, the focusing curve CV_6 rapidly decreases. The peak of the focusing curve CV_6 that appears in the vicinity of the center is caused by such a change in the ratio of the high luminance component.

  Thereafter, the focusing curve CV_6 is raised by the focus on the leg of the desk light DSK1, and is lowered by the defocus on the leg of the desk light DSK1. The peak of the focusing curve CV_6 that appears in the vicinity of the closest end is caused by such a variation in the focusing degree.

  The high luminance component of the light source LT2 also enters the focus area FB_0 in a different manner depending on the defocus amount with respect to the light source LT2. When the ratio of the high luminance component in the focus area FB_0 decreases to a certain numerical value, the focusing curve CV_0 rapidly decreases. The lowered focusing curve CV_0 is lowered as the ratio of the high luminance component is further reduced.

  The focusing curve CV_4 rises due to the focus on the face of the person HM1 and falls due to the defocus on the face of the person HM1. The peak of the focusing curve CV_4 that appears in the vicinity of the center is caused by such a variation in the degree of focusing.

  In the peak detection process, first, the latest luminance change rate and high luminance count value in the focus area of interest are detected from the registers RGST2 and RGST3, respectively, and the flag HL_FLG is set based on the detected luminance change rate and high luminance count value. Is adjusted.

  The flag HL_FLG is set to “1” when the luminance change rate exceeds the threshold TH1 and the high luminance count value exceeds “0”, and the high luminance count value exceeds the threshold TH2 even when the luminance change rate is equal to or lower than the threshold TH1. Is set to “1”.

  The flag HL_FLG is also set to “0” when the luminance change rate and the high luminance count value are equal to or lower than the threshold value TH1 and the threshold TH2, respectively, and the high luminance count value is “0” even if the luminance change rate exceeds the threshold value TH1. If it is less than or equal to “0”, it is set to “0”.

  That is, the flag HL_FLG is set to “1” when a high luminance component such as a light source exists in the focus area of interest, and is set to “0” when there is no high luminance component in the focus area of attention.

  When the setting of the flag HL_FLG is completed, it is determined whether or not the flag HL_FLG of the focused focus area is “0” and whether or not a peak appears in the focusing curve of the focused focus area. In peak discrimination, one or more AF evaluation values registered in the register RGTS1 corresponding to the focus area of interest are referred to.

  When the flag HL_FLG is “0” and a peak appears in the focus curve of the focus area, the flag RE_FLG provided in the register RGST4 shown in FIG. 8 is set to “1” corresponding to the focus area. . On the other hand, if the flag HL_FLG is “1” or no peak appears in the focusing curve of the focus area of interest, the flag RE_FLG provided in the register RGST4 is set to “0” corresponding to the focus area of focus. .

  Accordingly, the flag RE_FLG is set to “1” when a peak appears in the focus curve of the focus area where no high luminance component exists. In other words, even if a peak appears in the focus curve of the focus area, the flag RE_FLG is not set to “1” if a high-luminance component exists in the focus area.

  In the example shown in FIGS. 9 to 11, when the peak of the focusing curve CV_4 appears near the center, the flag RE_FLG is set to “1” corresponding to the focus area FB_4. Further, when the peak of the focusing curve CV_6 appears in the vicinity of the closest end, the flag RE_FLG is set to “1” corresponding to the focus area FE_6.

  The peak detection process ends when the state of the flag RE_FLG is determined for all of the focus areas FB_0 to FB_8.

  When the peak detection process ends, the state of the flag RE_FLG provided in the register RGST1 is determined. If at least one of these flags RE_FLG indicates “1”, one or more focusing curves corresponding to RE_FLG = 1 are specified from the focusing curves CV_0 to CV_8. Furthermore, the change rate of the AF evaluation value in the vicinity of the peak is calculated for each specified focusing curve, and it is determined whether or not at least one of the calculated change rates of 1 or 2 or more exceeds the threshold value THrt.

  If a focus curve showing a change rate exceeding the threshold value THrt is found, the peak position of the found focus curve is regarded as a focus point, and the focus lens 12 is disposed at this focus point. In the example of FIG. 11, the rate of change in the vicinity of the peak of the focusing curve CV4 exceeds the threshold value THrt. As a result, the focus lens 12 is disposed at the peak position of the focusing curve CV4. The AF process is terminated when the focus lens 12 is placed at the focal point.

  On the other hand, if “1” does not exist in the description of the register RGST4 or if a focusing curve showing a change rate exceeding the threshold value THrt is not found, the focus lens 12 is moved to the infinite side by a predetermined amount, and the variable P Is incremented and the process described above is resumed.

  CPU30 performs the process according to the imaging task shown in FIGS. A control program corresponding to this imaging task is stored in the flash memory 44.

  First, in step S1, through image processing is executed. As a result, a through image representing the object scene is output from the LCD monitor 38. In step S3, it is determined whether or not the shutter button 28s is half-pressed, and the through image AE process in step S5 is repeated as long as the determination result is NO. As a result, the brightness of the through image is appropriately adjusted. When the shutter button 28s is half-pressed, the recording AE process is executed in step S3, and the AF process is executed in step S7. The brightness of the through image is adjusted to the optimum value by the process of step S7, and the focus lens 12 is arranged at the in-focus position by the process of step S9.

  In step S11, it is determined whether or not the shutter button 28s has been fully pressed. In step S13, it is determined whether or not the operation of the shutter button 28s has been released. If “YES” in the step S11, the process returns to the step S1 through the recording process of the step S15. If “YES” in the step S13, the process returns to the step S3 as it is.

  The AF process in step S9 is executed according to a subroutine shown in FIGS. First, in step S21, the focus lens 12 is arranged at the closest end, and in step S23, the variable P is set to “0”.

  By the variable P setting process, the writing position of the AF evaluation value in the register RGST1 is designated, the writing position of the luminance change rate in the register RGST2 is designated, and the writing position of the high luminance count value in the register RGST3 is designated.

  When the vertical synchronization signal Vsync is generated, the process proceeds from step S25 to step S27, and a peak detection process focusing on the focusing curves CV_0 to CV_8 respectively corresponding to the focus areas FB_0 to FB_8 is executed.

  As a result of the peak detection process, the flag RE_FLG provided in the register RGST4 is set to “0” or “1” corresponding to each of the focus areas FB_0 to FB_8. That is, the flag RE_FLG is set to “1” when a peak appears in the focusing curve in the focus area where no high luminance component exists, and is set to “0” under other circumstances.

  In step S29, it is determined whether or not at least one of the flags RE_FLG provided in the register RGST4 indicates “1”. If the determination result is NO, the process proceeds to step S31, and the focus lens 12 is moved to the infinite side by a predetermined amount. When the lens movement process is completed, the variable P is incremented in step S33, and then the process returns to step S25.

  If the decision result in the step S29 is YES, the process proceeds to a step S35 so as to specify one or more focusing curves corresponding to RE_FLG = 1 from the focusing curves CV_0 to CV_8. In step S37, the rate of change of the AF evaluation value in the vicinity of the peak is calculated for each specified focusing curve, and in step S39, it is determined whether or not at least one of the calculated rates of change exceeds the threshold value THrt.

  If the determination result is NO, the process returns to step S31, while if the determination result is YES, the process proceeds to step S41. In step S41, the peak position of the focusing curve showing the rate of change exceeding the threshold value THrt (specifically, a position closer to the preset amount by twice the current lens position) is regarded as the focusing position, and this focusing is performed. The focus lens 12 is disposed at the position. When the process of step S43 is completed, the process returns to the upper layer routine.

  The peak detection process in step S27 shown in FIG. 13 is executed according to the subroutine shown in FIGS. First, in step S51, the variable K is set to “1”. In step S53, the latest luminance change rate corresponding to the variable K is detected from the register RGST2, and in step S55, the latest high luminance count value corresponding to the variable K is detected from the register RGST3.

  In step S57, it is determined whether or not the luminance change rate detected in step S53 exceeds a threshold value TH1. In step S59, it is determined whether or not the high brightness count value detected in step S55 exceeds a threshold value TH2. Further, in step S61, it is determined whether or not the high brightness count value detected in step S55 exceeds “0”.

  If both steps S57 and S61 are YES, or if NO in step S57 and YES in step S59, flag HL_FLG is set to “1” in step S63. If both of steps S57 and S59 are NO, or if YES in step S57 and NO in step S61, flag HL_FLG is set to “0” in step S65.

  Accordingly, the flag HL_FLG is set to “1” when a high luminance component exists in the focus area FB_K, and is set to “0” when no high luminance component exists in the focus area FB_K.

  When the process of step S81 or S83 is completed, it is determined in step S67 whether or not the flag HL_FLG indicates “0”, and whether or not a peak appears in the focusing curve CV_K is determined in step S69. In the determination process in step S69, one or more AF evaluation values registered in the register RGTS1 corresponding to the focus area FB_K are referred to.

  If both steps S67 and S69 are YES, the process proceeds to step S71, and the flag RE_FLG provided in the register RGST4 is set to “1” corresponding to the variable K. If “NO” in the step S67 or S69, the process proceeds to a step S73 to set a flag RE_FLG provided in the register RGST4 to “0” corresponding to the variable K.

  Accordingly, the flag RE_FLG is set to “1” when a peak appears in the focus curve of the focus area where no high luminance component exists. In other words, even if a peak appears in the focus curve of the focus area, the flag RE_FLG is not set to “1” if a high-luminance component exists in the focus area. By controlling the setting of the flag RE_FLG in this way, the focus curve of the focus area where the high luminance component exists is excluded from the focus determination target.

  When the process of step S71 or S73 is completed, the variable K is incremented in step S75, and it is determined in step S77 whether or not the variable K exceeds “8”. If the determination result is NO, the process returns to step S53, and if the determination result is YES, the process returns to the upper hierarchy routine.

  As can be seen from the above description, focus areas FB_0 to FB_8 are assigned to the imaging surface 16f. The CPU 30 repeatedly changes the distance from the focus lens 12 to the imaging surface 16f (S31), and parallels the high-frequency component of the object scene image captured in each of the focus areas FB_0 to FB_8, that is, the AF evaluation value, in parallel with the distance change process. Are repeatedly detected (S23, S25, S33). The CPU 30 also selects one or more focus areas out of the high brightness condition from the focus areas FB_0 to FB_8 based on the luminance information of the object scene image captured in each of the focus areas FB_0 to FB_8 ( S53 ~ S65). This selection process is repeatedly executed in parallel with the distance adjustment process. Further, the CPU 30 adjusts the distance from the focus lens 12 to the imaging surface 16f to a distance corresponding to the focal point based on the AF evaluation value detected corresponding to the selected one or more focus areas (S67). ~ S71, S29, S35 ~ S41).

  The process of selecting one or more focus areas that satisfy the high luminance condition is repeatedly executed in parallel with the process of changing the distance from the focus lens 12 to the imaging surface 16f. On the other hand, the spread of the high-luminance portion that appears around the light source differs depending on the degree of focus on the light source. Therefore, when a light source exists in the object scene, one or more selected focus areas can be changed with a change in the distance from the focus lens 12 to the imaging surface 16f. The distance from the focus lens 12 to the imaging surface 16f is adjusted to the distance corresponding to the focal point based on the high frequency component corresponding to one or more focus areas selected in this way. Thereby, it is possible to maintain the focusing performance with respect to the object field including the light source.

  In this embodiment, the focus lens 12 is moved in the optical axis direction during the AF processing, but the imaging surface is moved in the optical axis direction instead of the focus lens 12 or together with the focus lens 12. You can do it.

  In this embodiment, the AF process is terminated when the in-focus position is detected (see step S41 in FIG. 14). However, the AF process may be terminated after the focus lens 12 reaches the end on the infinite side.

DESCRIPTION OF SYMBOLS 10 ... Digital camera 12 ... Focus lens 16 ... Imaging device 24 ... Luminance evaluation circuit 26 ... Focus evaluation circuit 30 ... CPU
44 ... Flash memory

Claims (7)

Changing means for repeatedly changing the distance from the focus lens to the imaging surface having a plurality of evaluation areas;
Detecting means for repeatedly detecting a high-frequency component of the object scene image captured in each of the plurality of evaluation areas in parallel with the changing process of the changing means;
Processing for selecting one or more evaluation areas out of the high luminance condition from the plurality of evaluation areas based on luminance information of the object scene image captured in each of the plurality of evaluation areas. Selection means for repeatedly executing in parallel with the changing process; and the imaging surface from the focus lens based on the high-frequency component detected by the detection means corresponding to one or more evaluation areas selected by the selection means An electronic camera comprising adjustment means for adjusting the distance to a specific distance corresponding to the focal point.   The selection means is detected by the luminance information detection means for detecting the luminance information of the object scene image captured in each of the plurality of evaluation areas in parallel with the changing process of the changing means, and the luminance information detection means. The electronic camera according to claim 1, further comprising comparison means for comparing the brightness information with the reference.   The electronic camera according to claim 2, wherein the luminance information includes, as a parameter, a number of pixels that exhibit luminance exceeding a set amount and / or a luminance change amount associated with the changing process of the changing unit.   The adjusting means extracts from the one or two or more evaluation areas selected by the selection means the specific evaluation area where the high-frequency component indicating the maximum value is detected, and is detected in the specific evaluation area The electronic camera according to claim 1, further comprising an adjustment processing unit that performs an adjustment process to the specific distance based on a change amount of a high-frequency component.   The electronic camera according to claim 4, wherein the adjustment unit further includes an activation control unit that activates the adjustment processing unit when a change amount of the high-frequency component detected in the specific evaluation area exceeds a threshold value. In the electronic camera processor,
A change step for repeatedly changing the distance from the focus lens to the imaging surface having a plurality of evaluation areas;
A detection step of repeatedly detecting a high-frequency component of the object scene image captured in each of the plurality of evaluation areas in parallel with the change process of the change step;
Processing for selecting one or more evaluation areas out of the high luminance condition from the plurality of evaluation areas based on luminance information of the object scene image captured in each of the plurality of evaluation areas. A selection step that is repeatedly executed in parallel with the change process; and the imaging surface from the focus lens based on the high-frequency component detected by the detection step corresponding to one or more evaluation areas selected by the selection step A focus control program for executing an adjustment step for adjusting the distance to the distance corresponding to the focal point. A focus control method executed by an electronic camera,
A change step for repeatedly changing the distance from the focus lens to the imaging surface having a plurality of evaluation areas;
A detection step of repeatedly detecting a high-frequency component of the object scene image captured in each of the plurality of evaluation areas in parallel with the change process of the change step;
Processing for selecting one or more evaluation areas out of the high luminance condition from the plurality of evaluation areas based on luminance information of the object scene image captured in each of the plurality of evaluation areas. A selection step that is repeatedly executed in parallel with the change process; and the imaging surface from the focus lens based on the high-frequency component detected by the detection step corresponding to one or more evaluation areas selected by the selection step A focus control method comprising an adjustment step of adjusting the distance to the distance corresponding to the focal point.

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