JP2006039254A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera for obtaining a field-of-view image visually in focus on a desired object. <P>SOLUTION: A CPU 34 specifies a plurality of proper intervals on a plurality of the objects in a field of view by a contrast detection method respectively when a shutter button is half-pressed, displays a plurality of object images caught at the plurality of the specified proper intervals on an LCD monitor 30 respectively, receives selection operation selecting any one of a plurality of the field-of-view images from a cursor/OK key 38, and notifies a driver 16 of the proper interval corresponding the field-of-view image selected by the selection operation. The driver 16 adjusts the position of a focus lens 12 on the basis of the notified proper interval. The CPU 34 executes the photographing when the shutter button is fully pressed after focus adjustment is completed. Thereby the field-of-view image visually in focus on the desired object can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a camera, and more particularly to a camera that performs autofocus (AF) adjustment by a contrast detection method, for example.

  Conventionally, in this type of camera, generally, when the shutter button is pressed halfway, the focus lens is moved stepwise from the far end point to the near end point, and the object scene is imaged. Evaluate the contrast of the field image. The evaluation is performed for the AF evaluation area assigned to the center of the object scene. Then, the focus position corresponding to the object scene image having the maximum evaluation value is identified as the focal point, and the focus lens is moved to a position according to the identified focal point. Thereafter, the main photographing is executed when the shutter button is fully pressed.

  In the related art, by performing a shutter operation in a state where a desired subject is introduced into the AF evaluation area, an appropriate scene image in which the desired subject is in focus can be obtained in many cases.

  However, when a desired subject is introduced into the AF evaluation area, a subject other than the desired subject usually enters the AF evaluation area together. If the contrast of another subject is higher than that of the desired subject, only an inappropriate image in which the desired subject is blurred can be obtained. For example, when a person is photographed outdoors, if there is a high contrast object such as a tree behind the person, the tree behind may be in focus and the person image may be blurred. Also, if you try to take a picture of a landscape through a window glass, the entire window may be blurred because the near window glass is in focus.

  Therefore, a main object of the present invention is to provide a camera capable of obtaining an object scene image in which a desired subject is in focus.

  The camera according to the first aspect of the invention evaluates the contrast of the object scene image captured by the imaging surface each time the interval is displaced by the displacing means for stepwise displacing the distance between the optical lens and the imaging surface. Evaluation means, identification means for identifying a plurality of appropriate intervals appropriate for a plurality of subjects belonging to the object scene based on the evaluation values obtained by the evaluation means, and a plurality of subjects captured at the plurality of appropriate intervals, respectively Display means for displaying a field image, accepting means for receiving a selection operation for selecting any one of a plurality of object scene images, and appropriateness corresponding to an object scene image selected by a selection operation among a plurality of appropriate intervals An enabling means for enabling the interval is provided.

  The distance between the optical lens and the imaging surface is displaced stepwise by the displacement means, and the evaluation means evaluates the contrast of the object scene image captured by the imaging surface every time the distance is displaced. The specifying unit specifies a plurality of appropriate intervals that are appropriate for a plurality of subjects belonging to the object scene based on the evaluation value obtained by the evaluation unit. That is, a plurality of appropriate intervals that are appropriate for a plurality of subjects belonging to the scene are specified by the contrast detection method. A plurality of scene images captured at a plurality of appropriate intervals thus identified are displayed on the display means, and the accepting means accepts a selection operation for selecting any one of the plurality of scene images. The validating means validates the appropriate interval corresponding to the object scene image selected by the selection operation among the plurality of appropriate intervals.

  The camera according to the invention of claim 2 is dependent on claim 1, and further comprises an extraction means for extracting a plurality of object scene images respectively corresponding to a plurality of appropriate intervals in parallel with the evaluation operation of the evaluation means, and a display means Displays a plurality of scene images extracted by the extracting means.

  In parallel with the evaluation operation of the evaluation means, a plurality of object scene images respectively corresponding to a plurality of appropriate intervals are extracted by the extraction means, and the display means displays the extracted plurality of object scene images. Since a plurality of object scene images are extracted in parallel with the evaluation operation, a plurality of object scene images can be displayed immediately after the evaluation is completed.

  The camera according to the invention of claim 3 is dependent on claim 1 or 2, and is provided with a memory in which a plurality of areas for holding a plurality of appropriate intervals are formed, and two evaluation values obtained successively by the evaluation means. Comparing means for comparing each other, and changing means for changing a variable for designating one of the plurality of areas when a comparison result of the comparing means satisfies a predetermined condition.

  A plurality of areas for holding a plurality of appropriate intervals are formed in the memory. The comparison means compares the two evaluation values successively obtained by the evaluation means with each other, and the changing means designates one of a plurality of areas formed in the memory when the comparison result satisfies a predetermined condition. To change. Since the areas are sequentially switched each time the comparison result satisfies the predetermined condition, a plurality of appropriate intervals can be held in the plurality of areas, respectively.

  The camera according to the invention of claim 4 is dependent on claim 3 and further comprises detection means for detecting the number of consecutive comparison results that the evaluation value obtained this time is lower than the evaluation value obtained last time, The higher the contrast, the larger the value, and the predetermined condition includes a threshold condition that the number of times detected by the detection means exceeds the threshold value.

  The detection means detects the number of consecutive comparison results that the evaluation value obtained this time is lower than the evaluation value obtained last time. The evaluation value indicates a larger value as the contrast is higher, and the predetermined condition includes a threshold condition that the number of times detected by the detection unit exceeds the threshold value.

  The camera according to the invention of claim 5 is dependent on claim 4, and the predetermined condition further includes a numerical condition that the evaluation value obtained this time does not fall below the evaluation value obtained last time.

  According to the fourth and fifth aspects, the area is switched when the state in which the contrast decreases continues beyond the period corresponding to the threshold value.

  The camera according to the invention of claim 6 is dependent on claim 1, and is an assigning means for assigning a plurality of evaluation areas to the imaging surface, and a plurality of local areas respectively corresponding to the plurality of evaluation areas for the object scene image captured at an appropriate interval. A calculation means for calculating a local contrast evaluation value, and a selection means for selecting an evaluation area corresponding to the largest one of the plurality of local contrast evaluation values calculated by the calculation means from the plurality of evaluation areas, The display means displays a marker indicating the position of the evaluation area selected by the selection means on the object scene image.

  A plurality of evaluation areas are assigned to the imaging surface. The calculating means calculates a plurality of local contrast evaluation values respectively corresponding to a plurality of evaluation areas for the scene image captured at an appropriate interval. The selection means selects an evaluation area corresponding to the maximum one of the plurality of calculated local contrast evaluation values from the plurality of evaluation areas. The display means displays a marker indicating the position of the evaluation area selected in this manner so as to overlap the object scene image. As a result, it is possible to know which position is most focused in the displayed object scene image, so that the selection operation can be performed accurately.

  A program according to a seventh aspect of the present invention is a distance adjusting program that is executed by a camera processor and adjusts the distance between the optical lens and the imaging surface. An evaluation step that evaluates the contrast of the object scene image captured by the imaging surface each time it is displaced, and a plurality of appropriate intervals that are appropriate for a plurality of subjects belonging to the object scene based on the evaluation value obtained by the evaluation step A specifying step for specifying the image, a display step for displaying a plurality of scene images captured at a plurality of appropriate intervals, a reception step for receiving a selection operation for selecting any one of the plurality of scene images, and a plurality of steps A validating step for validating the proper interval corresponding to the object scene image selected by the selection operation among the proper intervals

  According to the present invention, a plurality of appropriate intervals that are appropriate for a plurality of subjects in the scene are specified by the contrast detection method, and a plurality of scene images captured at the plurality of specified appropriate intervals are displayed. And accepting a selection operation for selecting any one of a plurality of object scene images, and enabling an appropriate interval corresponding to the object scene image selected by the selection operation, so that a desired subject is in focus. A field image is obtained.

  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.

  Referring to FIG. 1, a digital camera 10 of this embodiment includes a focus lens 12. The optical image of the object scene is irradiated to the light receiving surface of the image sensor 14, that is, the imaging surface through the focus lens 12. On the imaging surface, a charge corresponding to the optical image of the subject, that is, a raw image signal is generated by photoelectric conversion.

  When displaying a real-time moving image of a subject, that is, a through image, on the LCD monitor 30, the CPU 34 instructs the timing generator / signal generator (TG / SG) 18 to repeat pre-exposure and thinning-out reading. The TG / SG 18 repeatedly executes pre-exposure of the image sensor 14 and thinning-out reading of the raw image signal generated thereby. The image sensor 14 outputs a low-resolution raw image signal corresponding to the optical image of the subject.

  The output raw image signal is subjected to a series of processes of noise removal, level adjustment and A / D conversion by the CDS / AGC / AD circuit 20, and thereby, raw image data which is a digital signal is obtained. 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 CDS / AGC / AD circuit 20 to generate YUV format image data. The generated image data is written into the SDRAM 26 by the memory control circuit 24 and then read out by the same memory control circuit 24. The video encoder 28 converts the image data read by the memory control circuit 24 into a composite video signal conforming to the NTSC format, and provides the converted composite video signal to the LCD monitor 30. As a result, a through image of the subject is displayed on the monitor screen.

  Of the image data generated by the signal processing circuit 22, Y data is also provided to the AF evaluation circuit 32 for focus adjustment. Referring to FIG. 2, the AF evaluation circuit 32 divides the object scene into 16 parts in each of the horizontal direction and the vertical direction, and the evaluation area E0 assigned to the center of the object field among these 256 divided areas. Accumulate high frequency components of Y data. Thereby, a high-frequency AF evaluation value (hereinafter referred to as “AF evaluation value”) is obtained.

  Referring again to FIG. 1, when the shutter button 36 is half-pressed, the CPU 34 first performs the following AF maximum point detection. In AF maximum point detection, the focus lens 12 is first moved to the far end point. Thereafter, through imaging is performed while moving the focus lens 12 step by step from the far end point to the near end point, and an AF evaluation value is acquired from the AF evaluation circuit 32 for each step. Based on the change of the AF evaluation value periodically acquired in this way, the local maximum value of the AF evaluation value and the position of the focus lens 12 when the AF evaluation value becomes the local maximum are specified.

  The relationship between the focus position and the AF evaluation value is shown in FIG. Referring to FIG. 3, if through-shooting is performed while moving the focus lens 12 from the far end point to the near end point, the AF evaluation value generally becomes maximum at a plurality of focus positions. Here, these maximum values are described as Amax [0] to Amax [i]. Further, focus positions corresponding to the maximum values Amax [0] to Amax [i], that is, in-focus positions, are described as Afpos [0] to Afpos [i].

  Referring to FIG. 1 again, the CPU 34 is provided with a maximum value register 34r and a focus position register 34s. As shown in FIG. 4, the maximum value register 34 r includes a plurality of areas [0], [1], [2],. As shown in FIG. 5, the in-focus position register 34s is composed of a plurality of areas [0], [1], [2],. The CPU 34 holds the detected maximum values Amax [0] to Amax [i] in the areas [0] to [i] in the maximum value register 34r, respectively. The CPU 34 also registers the specified in-focus positions Afpos [0] to Afpos [i] in the areas [0] to [i] in the in-focus position register 34s, respectively.

  On the other hand, the SDRAM 26 is provided with a focusing frame memory 26m. As shown in FIG. 6, the focusing frame memory 26m is composed of a plurality of areas [0], [1], [2],. The CPU 34 further converts the frames taken at the in-focus positions Afpos [0] to Afpos [i], that is, the low-resolution images of the in-focus frames [0] to [i], into the regions [0] to [0] to the in-focus frame memory 26m. Store each in [i].

  Next, the CPU 34 generates a thumbnail list of the focused frames [0] to [i] based on the image information in the focused frame memory 26m, and a focused frame selection screen including the generated thumbnail list (FIG. 16). Reference (described later) is displayed on the LCD monitor 30. The operator refers to the displayed thumbnail list and focuses on any one of the in-focus frames [0] to [i], more specifically, a desired subject among a plurality of subjects in the object scene. Select the in-focus frame that matches.

  The CPU 34 accepts the operator's selection operation via the cursor / OK key 38, and reads the focus position corresponding to the selected focus frame from the focus position register 34s. Then, the driver 16 is notified of the read focus position. In response, the driver 16 moves the focus lens 12 to the notified position.

  When the shutter button 36 is fully pressed after the focus adjustment is completed in this way, the following main photographing process is executed. In the main photographing process, the CPU 34 instructs the TG / SG 18 to perform the main exposure and the reading of all charges generated by the main exposure. The image sensor 14 is subjected to the main exposure, and all charges generated by this, that is, a high-resolution raw image signal is output from the image sensor 14. The output raw image signal is converted into raw image data by the CDS / AGC / AD circuit 20, and the raw image data is converted into YUV format image data by the signal processing circuit 22. The converted raw image data is written into the SDRAM 26 through the memory control circuit 24.

  The CPU 34 also instructs the JPEG codec 40 to compress the image data stored in the SDRAM 26. The JPEG codec 40 reads image data from the SDRAM 26 through the memory control circuit 24, and performs JPEG compression on the read image data. The compressed image data generated thereby is written into the SDRAM 26 through the memory control circuit 24. When JPEG compression is completed, the CPU 34 reads the compressed image data from the SDRAM 26 through the memory control circuit 24, and records the image file including the read compressed image data on the recording medium 44 through the I / F 42.

  Specifically, the CPU 34 performs processing according to the flowcharts shown in FIGS. Note that programs corresponding to these flowcharts are stored in the flash memory 46. First, referring to FIG. 7, in step S1, a through photographing command is issued. In response, a low-resolution raw image signal is output from the image sensor 14, and the raw image signal is converted into raw image data by the CDS / AGC / AD circuit 20. The raw image data is converted to YUV format image data by the signal processing circuit 22, and the YUV format image data is converted by the video encoder 28 to a composite video signal in accordance with the NTSC format. The composite video signal is given to the LCD monitor 30. As a result, a through image of the subject is displayed on the monitor screen.

  Of the image data generated by the signal processing circuit 22, Y data is also provided to the AF evaluation circuit 32 for focus control. The AF evaluation circuit 32 integrates the high frequency components of the Y data for the evaluation area E0 in the object scene, and thereby the AF evaluation value is output from the AF evaluation circuit 26.

  In step S3, it is determined whether or not the shutter button 36 is half-pressed. If the determination result is affirmative, the process proceeds to step S5 to perform AF maximum point detection (described later). In the next step S7, focus frame selection for selecting any one of a plurality of focus frames obtained by AF maximum point detection, and focus to the focus position corresponding to the selected focus frame are performed. Focus adjustment (to be described later) for moving the lens 12 is performed.

  Thereafter, the process enters a loop of steps S9 and S11, and waits for the half-pressed shutter button 36 to be fully pressed or half-pressed to be released. If the shutter button 36 is fully pressed, YES is determined in the step S9, and the process proceeds to a step S13 to perform the main photographing. When the main photographing is completed, the process returns to step S1. When the half-press of the shutter button 36 is released, YES is determined in the step S11, and the process returns to the step S3.

  The AF maximum point detection in step S5 is executed according to the subroutines shown in FIGS. Referring to FIG. 8, first, initialization processing is performed in step S21. In the initialization process, “0” is set in each of the variables i, x, y, and dcount. Also, “0” is set in Amax [0], Amax [1],... And Afpos [0], Afpos [1],.

  Amax [0], Amax [1],... Are held in areas [0], [1],. Afpos [0], Afpos [1],... Are held in areas [0], [1],. The variables i, x, y, and dcount are held in separate registers (not shown) in the CPU 34, respectively.

  In the next step S23, the position of the focus lens 12 is moved to the far end point, and then the process proceeds to step S25. In step S25, it waits for Vsync from TG / SG18. When Vsync is detected, YES is determined in the step S25, and a series of processes of the steps S27 to S49 are executed. In step S27, an AF evaluation value is acquired from the AF evaluation circuit 32, and the acquired AF evaluation value is set in a variable x.

  Referring to FIG. 9, in step S29, it is determined whether or not the value of variable x is larger than the value of variable y. If this determination result is affirmative, the process proceeds to step S47. In step S47, the variable x is set to the variable y, and the variable dcount is incremented. Then, the process proceeds to step S49.

  If the determination result of step S29 is negative, it will move to step S31 and the value of the variable x will be set to the variable y. In step S33, it is determined whether or not the value of the variable dcount is greater than a threshold value, here “2”. If the determination result in step S33 is affirmative, the variable i is incremented in step S35, and then the process proceeds to step S37. If the determination result of step S33 is negative, the process immediately proceeds to step S37.

  In step S37, the variable dcount is initialized. In step S39, it is determined whether or not the value of the variable x is larger than the value of Amax [i]. If the determination result is negative, the process proceeds to step S49. If the determination result in step S39 is affirmative, first, in step S41, the value of variable x is set in Amax [i], then in step S43, the current focus position is set in Afpos [i], and step S45. The current low-resolution image is stored in the area [i] in the focused frame memory 26m. Thereafter, the process proceeds to step 49.

  In step S49, it is determined whether or not the current focus position is at the near end point. If the focus position has not yet reached the near end point, the focus position is moved one step toward the near end in step S51, and then the process returns to step S25. When the focus position reaches the near end point, the routine returns to the upper layer routine.

  In short, it is determined whether the AF evaluation value is decreasing or increasing by comparing the current AF evaluation value (x) with the AF evaluation value (y) before 1V period in step S29. Only when in the phase, the variable x, the current focus position, and the current low-resolution image are written in the maximum value register 34r, the focus position register 34s, and the focus frame memory 26m, respectively, in steps S41, S43, and S45. When it is determined that the variable is decreasing, the variable dcount is incremented. That is, the value of the variable dcount indicates the duration of the decreasing phase.

  In step S33, it is determined based on the value of the variable dcount whether one increasing phase is continuing or a new increasing phase is entered. When it is determined that a new increasing phase is entered, the variable i is set in S35. It is incrementing. Accordingly, the AF evaluation value, the focus position, and the area where the low resolution image is written are changed.

  Even if the AF evaluation value that is increasing starts to decrease, if the value of the variable dcount does not exceed the threshold “2”, that is, if the duration of the decreasing phase does not exceed the 2V period, there is still one increasing phase. Considered to be ongoing. The threshold affects the detection sensitivity of the maximum point. Specifically, if the threshold value is reduced, the number of detected maximum points increases, and if the threshold value is increased, the number of detected maximum points decreases. For this reason, an appropriate threshold value is selected so that a necessary and sufficient number of local maximum points is detected.

  The variable i is incremented each time a new increase phase is entered, such as “0” in the first increase phase and “1” in the next increase phase. That is, each of the plurality of increasing phases is identified by the variable i.

  In the first increase phase [0], the AF evaluation value is repeatedly written in the area [0] in the maximum value register 34r, and the focus position is repeatedly written in the area [0] in the in-focus position register 34s. Is repeatedly written in the area [0] in the focused frame memory 26m. In the next increasing phase [1], the AF evaluation value is repeatedly written in the area [1] in the maximum value register 34r, and the focus position is repeatedly written in the area [1] in the in-focus position register 34s. Is repeatedly written in the area [1] in the in-focus frame memory 26m.

  Therefore, when the focus position reaches the near end point, the region [0], [1],... In the maximum value register 34r has a final AF evaluation value in the increase phase [0], [1],. In other words, the local maximum values [0], [1],... Remain, and the regions [0], [1],. .., And in-focus positions [0], [1],... Are left in the areas [0], [1],. 1],..., That is, low-resolution images of in-focus frames [0], [1],.

  The in-focus frame selection and the focus adjustment in step S7 are executed according to the subroutine of FIG. Referring to FIG. 10, first, in step S61, low resolution images are read from areas [0], [1],... In focusing frame memory 26m, and a plurality of low resolution images respectively corresponding to the read low resolution images are read. Are displayed as a list on the LCD monitor 30. In step S63, a selection operation for selecting one of a plurality of thumbnails is accepted via the cursor / OK key 38. In step S65, the number of the low resolution image corresponding to the selected thumbnail, that is, the focused frame number is set in the variable k.

  In step S67, the focus position, that is, Afpos [k] is read from the area [k] of the focus position register 34s, and the position of the focus lens 12 is moved to Afpos [k]. Thereafter, the process returns to the upper layer routine.

  Hereinafter, specific examples will be described with reference to FIGS. First, referring to FIG. 11, there are two subjects, that is, a house and a car, in the evaluation area E0. The car is behind the house. When AF maximum point detection is performed on the object field including two subjects having such a perspective difference, a result as shown in FIG. 12 is obtained.

  Referring to FIG. 12, the focus position is moved from the far end point side to the near end point side by 10 steps step by step from pos1 → pos2 →... → pos10, and a low-resolution image is captured at each step. And AF evaluation are performed. Thereby, AF evaluation values x1 to x10 respectively corresponding to the focus positions pos1 to pos10 are obtained.

  In the first to third steps, since it is determined that the AF evaluation value is increasing (see FIG. 9: Step S29), the AF evaluation value is repeated in Amax [0], that is, the region [0] of the local maximum register 34r. The focus position is written and written repeatedly in Afpos [0], that is, the area [0] of the in-focus position register 34s, and the low-resolution image is repeatedly recorded in the area [0] of the in-focus frame memory 26m.

  That is, the AF evaluation value x1 recorded in Amax [0] in the first step is overwritten by the AF evaluation value x2 in the second step, and this AF evaluation value x2 is overwritten by the AF evaluation value x3 in the third step. Is done. The focus position pos1 recorded in Afpos [0] in the first step is overwritten by the focus position pos2 in the second step, and this focus position pos2 is overwritten by the focus position pos3 in the third step. The low-resolution image of the first frame recorded in the area [0] of the focused frame memory 26m in the first step is overwritten by the low-resolution image of the second frame in the second step, and further, the low-resolution image of the second frame is overwritten. The image is overwritten with a third frame low resolution image in a third step.

  In the fourth to sixth steps, since it is determined that the AF evaluation value is decreasing, none of the AF evaluation value, the focus position, and the low resolution image is recorded. Instead, the variable dcount (see step S47) indicating the duration of the decreasing phase is incremented.

  In the seventh step, since the AF evaluation value increases from the previous time and the variable dcount exceeds “3”, that is, exceeds the threshold value “2”, it is determined that the AF evaluation value has changed from decreasing to increasing. Accordingly, the writing destination of the AF evaluation value is changed to Amax [1], that is, the area [1] of the register 34r, and the writing destination of the focus position is changed to AFpos [1], that is, the area [1] of the register 34s. The recording destination of the resolution image is changed to the area [1] of the focused frame memory 26m (see Steps S29 to S35).

  In the eighth and ninth steps, since it is determined that the AF evaluation value is increasing following the seventh step, the AF evaluation value is repeatedly written in Amax [1], and the focus position is repeatedly written in Afpos [1]. The written low resolution image is repeatedly recorded in the area [1] of the focused frame memory 26m. After the tenth step when the AF evaluation value decreases, the AF evaluation value, the focus position, and the low resolution image are not recorded.

  Thus, when the focus position reaches the near end point, the areas [0] and [1] of the maximum value register 34r hold x3 and x9 as shown in FIG. Further, pos3 and pos9 are held in the areas [0] and [1] of the in-focus position register 34s as shown in FIG. On the other hand, in the areas [0] and [1] of the focused frame memory 26m, as shown in FIG. 15, the low resolution image of the third frame and the low resolution image of the ninth frame are stored.

  Thereafter, as shown in FIG. 16, two thumbnail images based on the two low-resolution images in the focused frame memory 26m are displayed on the LCD monitor 30. One thumbnail image is in focus on the house, and the other is in focus on the car. When, for example, a thumbnail image focused on the automobile, that is, a focused frame [1] is selected by operating the cursor / OK key 38, the focus position pos9 is read from the area [1] of the maximum value register 34r. Then, the focus lens 12 is moved to this position, and then actual photographing is performed in response to the shutter being fully pressed. As a result, a high-resolution image focused on the automobile can be obtained.

  As is apparent from the above, in this embodiment, when the shutter button 36 is half-pressed, the CPU 34 specifies a plurality of in-focus positions that respectively focus on a plurality of subjects in the object field by the contrast detection method. The cursor / OK key is used to display a plurality of low-resolution images captured at a plurality of specified in-focus positions on the LCD monitor 30 and to select one of the displayed low-resolution images. The in-focus position corresponding to the low resolution image selected by the selection operation and selected by the selection operation is notified to the driver 16. In response, the driver 16 moves the focus lens 12 to the notified in-focus position. After the movement is completed, the CPU 34 executes the main photographing when the shutter button 36 is fully pressed. As a result, an appropriate high resolution image in which a desired subject is in focus can be obtained.

  In this embodiment, the focus lens 12 is moved in the optical axis direction for focusing. However, the image sensor 14 is moved in the optical axis direction instead of the focus lens 12 or together with the focus lens 12. It may be. In short, focusing can be performed by changing the distance between the focus lens 12 and the imaging surface of the image sensor 14.

  In this embodiment, a low-resolution image (see FIG. 16) of a plurality of focused frames is displayed on the LCD monitor 30, and a selection operation for selecting one image focused on a desired subject is accepted. However, for example, when the size of the LCD monitor 30 is small or when shooting an object scene with a small perspective, it is difficult to distinguish which frame is in focus on the desired subject. There is a possibility. Therefore, in the following, another embodiment in which the selection operation can be performed accurately even in such a case will be described.

  Referring to FIG. 17, a digital camera 10a according to another embodiment of the present invention includes an AF evaluation circuit 32a instead of the AF evaluation circuit 32 in the digital camera 10 of FIG. 1, and a CPU 34a instead of the CPU 34. Prepare. The components other than the AF evaluation circuit 32a and the CPU 34a are the same as those in FIG. 1, and are omitted in FIG. The CPU 34a is further provided with an AF maximum area register 34t in addition to the maximum value register 34r and the focus position register 34s similar to those of the CPU 34.

  Referring to FIG. 18, in addition to accumulating high frequency components of Y data for evaluation area E0, AF evaluation circuit 32a also adds Y data for five evaluation areas E1 to E5 allocated in evaluation area E0. The high frequency components of are integrated. Thus, AF evaluation values are obtained for a total of six areas, evaluation areas E0 to E5.

  Referring to FIG. 19, the AF maximum area register 34 t includes a plurality of areas [0], [1], [2],. The CPU 34a holds the AF maximum areas ASmaxArea [0] to ASmaxArea [i] selected by the AF maximum area selection process (described later) in the areas [0] to [i] in the AF maximum area register 34t, respectively.

  The AF maximum areas ASmaxArea [0] to ASmaxArea [i] held in the areas [0] to [i] in the AF maximum area register 34t are used to display low-resolution images of the focused frames [0] to [i] on the LCD monitor. This is read when a list is displayed in 30. Then, spot frames (see FIG. 25) corresponding to the read AF maximum areas ASmaxArea [0] to ASmaxArea [i] are displayed so as to overlap the low-resolution images of the focused frames [0] to [i]. .

  Except for performing the AF maximum area selection process and the spot frame display process as described above, the operation of the CPU 34a is the same as that of the CPU 34 (see FIGS. 7 to 10).

  Referring to FIG. 20, the AF maximum area selection process is performed between step S43 and step S45. The CPU 34a executes the AF maximum area selection process in step S44 according to the subroutine of FIG.

  Referring to FIG. 21, an initialization process is first performed in step S81. Specifically, “0” is set to each of the variable j and the variable ASmax. Thereafter, the variable j is incremented in step S83, and in the next step S85, it is determined whether or not the value of the variable j exceeds “5”. If this determination result is affirmative, the process returns to the upper layer routine, and if negative, the process proceeds to step S87.

  In step S87, the AF evaluation value AS_E [j] of the evaluation area E [j] for the current low resolution image is acquired from the AF evaluation circuit 32a. In step S89, it is determined whether or not the acquired AF evaluation value AS_E [j] is larger than the value of the variable ASmax. If the determination result is negative, the process returns to step S83.

  If the determination result of step S89 is affirmative, the process proceeds to step S91, and the AF evaluation value AS_E [j] acquired in step S87 is set to the variable ASmax. In step S93, the variable ASmaxArea [i], that is, E [j] is set in the area [i] in the AF maximum area register 34t, and then the process returns to step S83.

  When the loop of steps S83 to S93 is repeated five times in this way, as a result, the AF maximum area in the focused frame [i] is registered in the area [i] in the AF maximum area register 34t.

  Referring to FIG. 22, the spot frame display process is performed between step S61 and step S63. That is, after a plurality of thumbnails respectively corresponding to a plurality of low resolution images are displayed in a list on the LCD monitor 30 in step S61, the process proceeds to step S62 and held in the areas [0] to [i] in the AF maximum area register 34t. The read AF maximum areas ASmaxArea [0] to ASmaxArea [i] are read, and spot frames corresponding to the read AF maximum areas ASmaxArea [0] to ASmaxArea [i] are displayed on-screen, that is, a plurality of areas on the monitor screen are displayed. To be displayed over the thumbnail. In step S63, a selection operation for selecting one of the plurality of thumbnails is accepted.

  As described above, the AF maximum area is selected for the in-focus frame in step S44, and the spot frame indicating the AF maximum area is displayed on-screen in step S62, so that the position of the in-focus frame displayed in step S61 is the highest. You can see if the subject is in focus. For this reason, it is possible to easily distinguish which of the plurality of thumbnails displayed in a list, that is, the plurality of in-focus frames, is the in-focus frame in focus on the desired subject. As a result, the selection in step S63 is performed. The operation can be performed accurately.

  Specific examples will be described below. When the object scene as shown in FIG. 11 is photographed with the digital camera 10a, two in-focus frames [0] and [1] as shown in FIG. . For each of these two in-focus frames [0] and [1], as shown in FIGS. 23 (A) and 23 (B), the AF evaluation value is maximum in the five evaluation areas E1 to E5. Select an area to become.

  Referring to FIG. 23 (A), for focusing frame [0], since the front house is in focus, one of three evaluation areas E1, E3 and E4, for example, evaluation area E1 is selected. The Referring to FIG. 23B, for focusing frame [1], evaluation area E2 is selected because the automobile in the back is in focus.

  Referring to FIG. 24, evaluation areas E1 and E2 thus selected are stored in areas [0] and [1] (see FIG. 19) of AF maximum area register 34t, respectively.

  Referring to FIG. 25, when two thumbnail images, that is, two in-focus frames [0] and [1] are displayed on the LCD monitor 30, the left thumbnail image, that is, the in-focus frame [0], has an area E1. The spot frame is displayed on the screen, and the spot frame of the area E2 is displayed on the screen on the right thumbnail image, that is, the focused frame [1]. With these spot frames, the operator can easily know that the house is in focus in the left thumbnail image and that the car is in focus in the right thumbnail image.

  It is also possible to calculate the distance from the obtained in-focus position to the in-focus subject and further display the calculation result on-screen.

  Although the digital camera has been described above, the present invention can also be applied to a silver salt film camera. In this case, the imaging surface is the surface of the film.

1 is a block diagram showing a configuration of a digital camera which is an embodiment of the present invention. FIG. It is an illustration figure which shows AF evaluation area allocated to the object scene. It is a graph which shows the relationship between a focus position and AF evaluation value. It is an illustration figure which shows the content of the maximum value register | resistor 34r. It is an illustration figure which shows the content of the focusing position register | resistor 34s. It is an illustration figure which shows the content of the focusing frame memory 26m. It is a flowchart which shows a part of CPU operation | movement. It is a flowchart which shows another part of CPU operation | movement. It is a flowchart which shows the other part of CPU operation | movement. It is a flowchart which shows a part of others of CPU operation | movement. It is an illustration figure which shows an example of an object scene. 11 is an illustrative view for explaining the procedure of AF maximum point detection for the object scene. It is an illustration figure which shows the content of the focusing position register | resistor 34s after AF maximum point detection. It is an illustration figure which shows the content of the maximum value register | resistor 34r after AF maximum point detection. It is an illustration figure which shows the content of the focusing frame memory 26m after AF maximum point detection. It is an illustration figure which shows a focusing frame selection screen. It is a block diagram which shows the component added to FIG. 1 Example in other Example of this invention. FIG. 18 is an illustrative view showing an AF evaluation area assigned to a scene in the embodiment in FIG. 17; It is an illustration figure which shows the content of AF maximum area register 34t. FIG. 18 is a flowchart showing a part (S44) of the CPU operation added in the embodiment in FIG. 17; FIG. 18 is a flowchart showing another portion (S81 to S93) of the CPU operation added in the embodiment in FIG. 17; FIG. 18 is a flowchart showing another portion (S62) of the CPU operation added in the embodiment in FIG. 17; FIG. 17A is an illustrative view for explaining AF maximum area selection processing performed for the focused frame [0] in FIG. 16, and FIG. 17B is an AF maximum area performed for the focused frame [1] in FIG. It is an illustration figure for demonstrating selection processing. It is an illustration figure which shows the content of AF maximum area register 34t after AF maximum area selection. FIG. 17 is an illustrative view showing a spot frame displayed on the screen on the screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10a ... Digital camera 12 ... Focus lens 14 ... Image sensor 26m ... Focusing frame memory 32, 32a ... AF evaluation circuit 34, 34a ... CPU
34r: Maximum value register 34s: Focus position register 34t: AF maximum area register

Claims (7)

A displacement means for stepwise displacing the distance between the optical lens and the imaging surface;
Evaluation means for evaluating the contrast of the object scene image captured by the imaging surface each time the interval is displaced by the displacement means;
A specifying means for specifying a plurality of appropriate intervals that are appropriate for a plurality of subjects belonging to the object scene based on the evaluation value obtained by the evaluation means;
Display means for displaying a plurality of object scene images respectively captured at the plurality of appropriate intervals;
Receiving means for accepting a selection operation for selecting any one of the plurality of object scene images; and validating an appropriate interval corresponding to the object scene image selected by the selection operation among the plurality of appropriate intervals. A camera comprising an enabling means. An extraction means for extracting a plurality of object scene images respectively corresponding to the plurality of appropriate intervals in parallel with the evaluation operation of the evaluation means;
The camera according to claim 1, wherein the display unit displays a plurality of object scene images extracted by the extraction unit. A memory in which a plurality of areas for holding the plurality of appropriate intervals are formed;
Comparison means for comparing two evaluation values successively obtained by the evaluation means, and changing means for changing a variable that designates one of the plurality of areas when the comparison result of the comparison means satisfies a predetermined condition The camera according to claim 1, further comprising: It further comprises a detecting means for detecting the number of consecutive comparison results that the evaluation value obtained this time is lower than the evaluation value obtained last time,
The camera according to claim 3, wherein the evaluation value indicates a larger value as the contrast is higher, and the predetermined condition includes a threshold condition that a number of times detected by the detection unit exceeds a threshold value.   The camera according to claim 4, wherein the predetermined condition further includes a numerical condition that an evaluation value obtained this time does not fall below an evaluation value obtained last time. Assigning means for assigning a plurality of evaluation areas to the imaging surface;
Calculation means for calculating a plurality of local contrast evaluation values respectively corresponding to the plurality of evaluation areas for the object scene image captured at the appropriate interval; and a plurality of local contrast evaluation values calculated by the calculation means A selection means for selecting an evaluation area corresponding to the largest one from the plurality of evaluation areas;
The camera according to claim 1, wherein the display unit displays a marker indicating the position of the evaluation area selected by the selection unit so as to overlap the object scene image. An interval adjustment program that is executed by a camera processor and adjusts the interval between the optical lens and the imaging surface,
A displacement step for displacing the interval stepwise;
An evaluation step for evaluating the contrast of the object scene image captured by the imaging surface each time the interval is displaced by the displacement step;
A specifying step for specifying a plurality of appropriate intervals, each of which is appropriate for a plurality of subjects belonging to the scene, based on the evaluation value obtained by the evaluation step;
A display step of displaying a plurality of object scene images respectively captured at the plurality of appropriate intervals;
An accepting step of accepting a selection operation for selecting any one of the plurality of object scene images; and validating an appropriate interval corresponding to the object scene image selected by the selection operation among the plurality of appropriate intervals. An interval adjustment program comprising an enabling step.

Images