JP3949066B2 - Auto focus camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an autofocus camera, and more particularly, to an autofocus camera that keeps focusing on a main subject that moves within an object scene.
[0002]
[Prior art]
An example of a conventional autofocus camera of this type is disclosed in Patent Document 1. In this prior art, focus index values in a plurality of AF areas allocated in advance on the screen are obtained based on the captured image data of each frame. Each focus index value is subjected to a difference calculation between frames, and an AF area having the maximum difference value is specified as an area where the main subject exists. The focus is adjusted based on the specified AF area.
[0003]
[Patent Document 1]
JP 2000-188713 A
[0004]
[Problems to be solved by the invention]
However, in this prior art, since the position of the main subject is determined based on the difference values obtained in all of the plurality of AF areas, a secondary subject different from the main subject has moved in the field of view. Sometimes a secondary subject could be focused.
[0005]
Therefore, a main object of the present invention is to provide an autofocus camera that can reliably focus on a main subject.
[0006]
[Means for Solving the Problems]
  The autofocus camera according to the present invention isFocus adjustment is instructedFirst determining means for determining one focus area satisfying the first area condition as an effective focus area where the main subject exists, out of a plurality of focus areas assigned to the object scene, with the effective focus area as a reference Adjustment means for executing focus adjustment, a first focus area that is different from the effective focus area and satisfies the second area condition among a plurality of focus areas is determined as a predicted target destination focus area that is predicted to be a main subject destination. 2 determining means, third determining means for determining an expected movement destination focus area as an effective focus area when a luminance change condition is satisfied, and an effective focus areaButExpected destination focus areaDirection next toAn application means for applying a different numerical value to the luminance change condition according toThe first area condition is a condition that the position of the focus lens where the focus evaluation value is maximum exists on the closest side, and the second area condition is that the luminance change rate is maximum in the focus area adjacent to the effective focus area. It is a condition that there is,The luminance change condition is a first threshold condition that the luminance change rate of the predicted destination focus area is equal to or greater than the first thresholdBe satisfied when is satisfiedThe application unit sets the numerical value to the first threshold value.
[0007]
[Action]
    The first determining means isFocus adjustment is instructedThen, one focus area that satisfies the first area condition among a plurality of focus areas assigned to the object scene is determined as an effective focus area in which the main subject exists. The focus adjustment is executed by the adjustment unit with the effective focus area as a reference. The second determining means determines one focus area that is different from the effective focus area and satisfies the second area condition among the plurality of focus areas as an expected destination focus area that is expected to be the main subject destination. The expected movement destination focus area is determined as an effective focus area by the third determination unit when the luminance change condition is satisfied. Applicable means are effective focus areaButExpected destination focus area andAdjacent directionDepending on, different numerical values are applied to the luminance change condition. here,The first area condition is a condition that the position of the focus lens where the focus evaluation value is maximum exists on the closest side, and the second area condition is that the luminance change rate is maximum in the focus area adjacent to the effective focus area. It is a condition that there is,The brightness change condition is a first threshold condition that the brightness change rate of the predicted destination focus area is greater than or equal to the first threshold.Satisfied when satisfied.The applying unit sets the above-described numerical value as the first threshold value.
[0009]
Preferably, the plurality of focus areas are a center position focus area arranged at the center of the object scene, a vertical position focus area arranged at a position extending in the vertical direction from the center of the object scene, And a horizontal position focus area arranged at a position extending in the horizontal direction from the center.
[0012]
    Preferably, the fourth determining unit determines, as a monitoring target focus area, a focus area having a predetermined positional relationship with the predicted destination focus area among the plurality of focus areas.Note that the predetermined positional relationship is a positional relationship in which the effective focus area is adjacent to the effective focus area on a side different from the side adjacent to the predicted destination focus area.The luminance change condition is a second threshold condition that the luminance change rate of the monitoring target focus area is lower than the second threshold.Is a satisfactory condition when is more satisfied.
[0013]
  More preferably, the luminance change condition corresponds to a logical product of the first threshold condition and the second threshold condition..
[0014]
  Preferably, the apparatus further includes detection means for detecting the tilt state of the camera body in the direction around the optical axis, each of the plurality of focus areas has an identifier, and the application means is an identifier of each of the effective focus area and the predicted destination focus area. The numerical value is determined based on the detection result of the detection means.
[0018]
【The invention's effect】
  According to this inventionTheIt is possible to reliably adjust the focus to the main subject.
[0019]
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.
[0020]
【Example】
Referring to FIG. 1, a digital camera 10 of this embodiment includes a focus lens 12 and a diaphragm mechanism 14. The optical image of the object scene enters the light receiving surface of the CCD type image sensor 16 through these members. On the light receiving surface, charges corresponding to the optical image are generated by photoelectric conversion.
[0021]
When the LCD 40 is activated, a through image display process is executed. First, the CPU 24 commands the TG (Timing Generator) 18 to read the entire data. The TG 18 generates the vertical synchronization signal Vsync once every 1/30 seconds, and reads it from the image sensor 16 at a cycle of 30 fps and in a thinning manner. The image sensor 16 outputs a low-resolution raw image signal corresponding to the entire object scene at a rate of 1 frame per 1/30 second.
[0022]
The CSD / AGC circuit 26 performs known noise removal and level adjustment on the raw image signal of each frame output from the image sensor 16. The raw image signal subjected to such processing is converted into raw image data which is a digital signal by the A / D converter 28, and the converted raw image data is subjected to color separation, white balance adjustment, gamma correction, A series of processing such as YUV conversion is performed. YUV data is output from the signal processing circuit 28. The output YUV data of each frame is written into the SDRAM 34 by the memory controller 32, and then read out from the SDRAM 34 by the same memory controller 32. The read YUV data is converted into a composite image signal of the NTSC system by the video encoder 38, and the converted composite image signal is given to the LCD 40. As a result, a real-time moving image (through image) of the subject is displayed on the LCD screen.
[0023]
Of the YUV data generated by the signal processing circuit 30, Y data is also input to the AE / AF evaluation circuit 42. The AE / AF evaluation circuit 42 integrates the input Y data for each frame to calculate a luminance evaluation value Iy [i] (i: block number from 0 to 255) representing the degree of brightness of the subject. The focus evaluation value Ih [j] (j: focus area number of 0 to 4) representing the degree of focus of the focus lens 12 is calculated by integrating the high frequency components of the input Y data for each frame. .
[0024]
Specifically, as shown in FIG. 2, the AE / AF evaluation circuit 36 divides the object scene, that is, the screen into 16 parts in each of the horizontal direction and the vertical direction, and “0” in a raster scan manner for each of the divided blocks. A block number of “˜“ 255 ”is assigned, and Y data is integrated for each block to calculate 256 luminance evaluation values Iy [0] to Iy [255]. The AE / AF evaluation circuit 36 also assigns five focus areas to the object scene, assigns focus area numbers “0” to “4” to the focus areas, and assigns high frequency components of Y data to each focus area. Are integrated into the focus evaluation values Ih [0] to Ih [4].
[0025]
The focus area 0 is composed of 8 blocks “103”, “104”, “119”, “120”, “135”, “136”, “151”, and “152” located substantially in the center of the object scene. It is formed. The focus area 1 is formed by 8 blocks “99”, “100”, “115”, “116”, “131,“ 132 ”,“ 147 ”, and“ 148 ”located on the left side of the object scene. The focus area 2 is formed by 8 blocks “107”, “108”, “123”, “124”, “139,“ 140 ”,“ 155 ”and“ 156 ”located on the right side of the object scene. The focus area 3 is formed by eight blocks “182” to “185” and “198” to “201” located below the object field. The focus area 4 is formed by eight blocks “54” to “57” and “70” to “73” located above the object scene.
[0026]
When the shutter button 44 is half-pressed, the attitude of the digital camera 10 is determined based on the output of the tilt sensor 46. As a result, it is specified whether the digital camera 10 is in the upright state, the 90 ° inclined state toward the right direction, or the 90 ° inclined state toward the left direction.
[0027]
Subsequently, the luminance evaluation values Iy [0] to Iy [255] output from the AE / AF circuit 42 are taken in by the CPU 24, and based on this, the optimum exposure period Ts and the optimum aperture amount As for main exposure are obtained. . Further, the driving method of the image sensor 16 is determined in accordance with the brightness of the object scene, and an AF exposure period suitable for the determined driving method is obtained. When the overall thinning readout is maintained as the driving method, the AF exposure period Taf1 is obtained, and when the driving method is changed from the whole thinning readout to the partial thinning readout, the AF exposure period Taf2 is obtained.
[0028]
In the total thinning readout, as described above, the entire light receiving surface of the image sensor 16 is used as a readout area, and the charge is thinned out at a cycle of 30 fps. On the other hand, in the partial reading, the central area shown in FIG. 2 of the light receiving surface of the image sensor 16 is the reading area, and the charge is thinned out at a cycle of 60 fps. In the partial reading, the vertical synchronization signal Vsync is output from the TG 18 once every 1/60 seconds.
[0029]
Further, thresholds C [0] to C [4] assigned to the focus areas 0 to 4 shown in FIG. 2 are determined based on the selection state of the scene selection key 48 and the output of the tilt sensor 46. There are six scenes that can be selected by the scene selection key 48: “portrait scene”, “sport scene”, “landscape scene”, “evening scene”, “night scene” and “default scene”.
[0030]
The setting states of the thresholds C [0] to C [4] when “portrait scene” is selected are shown in FIGS. In the upright state shown in FIG. 3A, the threshold THa is set as the threshold C [0], the threshold THb is set as the thresholds C [1], C [2], and C [4], and the threshold THd is It is set as the threshold value C [3]. In the left 90 ° tilt state shown in FIG. 3B, the threshold value THa is set as the threshold value C [0], the threshold value THb is set as the threshold values C [2], C [3], and C [4], and the threshold value THd is set as the threshold value C [1]. In the 90 ° right tilt state shown in FIG. 3C, the threshold THa is set as the threshold C [0], the threshold THb is set as the thresholds C [1], C [3], and C [4], and the threshold THd is set as the threshold value C [2].
[0031]
FIGS. 4A to 4C show the setting states of the thresholds C [0] to C [4] when “sport scene” is selected. In the upright state shown in FIG. 4A, the threshold value THa is set as the threshold value C [0], the threshold value THb is set as the threshold values C [1], C [2], and C [4], and the threshold value THc is set. It is set as the threshold value C [3]. 4B, the threshold THa is set as the threshold C [0], the threshold THb is set as the thresholds C [2], C [3], and C [4]. THc is set as the threshold value C [1]. 4C, the threshold THa is set as the threshold C [0], the threshold THb is set as the thresholds C [1], C [3], and C [4]. THc is set as the threshold value C [2].
[0032]
FIGS. 5A to 5C show the setting states of the thresholds C [0] to C [4] when “landscape scene”, “evening scene” or “night scene” is selected. In the upright state shown in FIG. 5A, the threshold value THa is set as the threshold value C [0], the threshold value THb is set as the threshold values C [1] and C [2], and the threshold value THc is set as the threshold value C [4]. Then, the threshold value THd is set as the threshold value C [3]. 5B, the threshold value THa is set as the threshold value C [0], the threshold value THb is set as the threshold values C [3] and C [4], and the threshold value THc is set as the threshold value C [2]. ] And the threshold THd is set as the threshold C [1]. 5C, the threshold THa is set as the threshold C [0], the threshold THb is set as the thresholds C [3] and C [4], and the threshold THc is the threshold C [1]. ] And the threshold value THd is set as the threshold value C [2].
[0033]
FIGS. 6A to 6C show the setting states of the thresholds C [0] to C [4] when “default scene” is selected. In any of the upright state, the left 90 ° inclination state, and the right 90 ° inclination state, the threshold value THa is set as the threshold value C [0], and the threshold value THb is set to the threshold values C [1], C [2], C [3]. And C [4].
[0034]
Note that a relationship of THa <THb <THc <THd is established among the thresholds THa, THb, THc, and THd.
[0035]
When the setting of the thresholds C [0] to C [4] is completed, the focus lens 12 is moved stepwise in the optical axis direction by the focus driver 22, and the focus evaluation value Ih [0] of the object field photographed in each step. ] To Ih [4] are captured by the CPU 24. When the image sensor 16 is driven by the whole thinning readout method, the focus evaluation values Ih [0] to Ih [4] are taken into the CPU 24 at a rate of once every 1/30 seconds, and the image sensor 16 reads out the partial parts. When driven by the method, the focus evaluation values Ih [0] to Ih [4] are taken into the CPU 24 at a rate of once every 1/60 seconds.
[0036]
The CPU 24 determines any one of the focus areas 0 to 4 as the effective focus area Zc based on the focus evaluation values Ih [0] to Ih [4] acquired in each step. A focus area other than the effective focus area is defined as an “invalid focus area”.
[0037]
Specifically, among the focus evaluation values Ih [0] to Ih [4] acquired at each lens position, the maximum value is saved as the register values Ih [0] max to Ih [4] max, and the maximum value is The obtained position information fpos of the focus lens 12 is saved as register values f [0] to f [4].
[0038]
The saved register values Ih [0] max to Ih [4] max are compared with the above-described threshold values C [0] to C [4]. Of the focus areas satisfying the condition of Ih [j] max> threshold value C [j], the focus area having the maximum register value f [j], that is, the focus area closest to the in-focus point is set as the effective focus area Zc. It is determined. Further, the subject in the determined effective focus area Zc is focused.
[0039]
For example, when the portrait scene is selected and the person Hm1 is captured as shown in FIG. 7A, when the shutter button 44 is pressed halfway, the focus area 0 is determined as the effective focus area Zc. . Further, when the portrait scene is selected, and the person Hm2 present in the distance and the person Hm3 present in the vicinity are captured as shown in FIG. Area 2 is determined as the effective focus area Zc.
[0040]
When the sports scene is selected and the person Hm5 running far and the person Hm6 running near are captured as shown in FIG. 8, when the shutter button 44 is pressed halfway, the focus area 1 becomes the effective focus area Zc. It is determined.
[0041]
When a landscape scene, an evening scene, or a night scene is selected, and the shutter button 44 is half-pressed in a state in which a distant house Hs and a nearby person Hm4 are captured as shown in FIG. The focus area 2 is determined as the effective focus area Zc.
[0042]
When the effective focus area Zc is determined, the CPU 22 displays a frame indicating the effective focus area Zc on the LCD screen. The operator can visually grasp which focus area is currently set as the effective focus area Zc.
[0043]
Note that when the image sensor 16 is driven by the partial pulling readout method, reading of the YUV data stored in the SDRAM 34 is continued, but writing of the YUV data to the SDRAM 34 based on the raw image signal output from the image sensor 16 is continued. Is canceled. As a result, the display on the LCD 40 changes from a through image to a freeze image.
[0044]
However, when the effective focus area Zc is determined based on the focus evaluation values Ih [0] to Ih [4], the driving method of the image sensor 16 is returned from partial thinning readout to full thinning readout, and from the image sensor 16. Writing of the YUV data to the SDRAM 34 based on the output raw image signal is resumed. As a result, the display on the LCD 40 is also returned from the freeze image to the through image.
[0045]
When the half-pressed state of the shutter button 44 is continued, an automatic tracking process for continuously focusing on the main subject moving within the object scene is executed. The automatic tracking operation is executed as follows.
[0046]
First, the luminance evaluation values Iy [0] to Iy [255] are captured at a rate of once every several frames by the CPU 24, and the luminance evaluation values Iy [0] to Iy [255] captured this time and the luminance captured last time. Luminance differences ΔIy [0] to ΔIy [255] that are differences from the evaluation values (register values) Iy [0] ′ to Iy [255] ′ are calculated. Further, luminance change rates E [0] to E [255] for each block are calculated based on the register values Iy [0] ′ to Iy [255] ′ and the luminance differences ΔIy [0] to ΔIy [255]. Thereafter, luminance change rates Ef [0] to Ef [4] for each focus area are calculated.
[0047]
Whether or not the main subject has moved from the effective focus area Zc to another focus area is determined based on the calculated luminance change rates Ef [0] to Ef [4]. That is, since the luminance changes when the subject moves, the movement determination of the main subject is performed by paying attention to the luminance change rate Ef [j] of the focus area other than the effective focus area Zc.
[0048]
Specifically, if the focus area 0 is the effective focus area Zc, the focus area having the maximum luminance change rate Ef [j] among the invalid focus areas 1 to 4 is determined as the predicted destination area Zt. Furthermore, a focus area located on the opposite side of the predicted movement destination area Zt with the focus area 0 interposed therebetween is determined as the monitoring target area Zm. Further, the threshold value K to be compared with the luminance change rate Ef [j] of the expected movement destination area Zt is determined in the following manner according to the attitude of the digital camera 10. Note that the threshold value L compared with the luminance change rate Ef [j] of the monitoring target area Zm is a fixed value.
[0049]
Referring to FIGS. 10A and 10B, when digital camera 10 is in the upright state, main subject Pr existing on focus area 0 is focus area 1 rather than focus area 3 or 4. Or it seems to move towards 2. On the other hand, if the digital camera 10 is tilted by 90 °, the main subject Pr existing on the focus area 0 seems to move toward the focus area 3 or 4 rather than the focus area 1 or 2. For this reason, if the digital camera 10 is in the upright state, the threshold value K assigned to the force area 1 or 2 is set lower than the threshold value K assigned to the focus area 3 or 4. If the digital camera 10 is tilted by 90 °, the threshold value K assigned to the force area 3 or 4 is set lower than the threshold value K assigned to the focus area 1 or 2.
[0050]
On the other hand, if any one of the focus areas 1 to 4 is the effective focus area Zc, three invalid focus areas close to the effective focus area Zc are determined as candidates for the predicted destination area Zt. That is, if the focus area 1 or 2 is the effective focus area Zc, the focus areas 0, 3 and 4 are candidates, and if the focus area 3 or 4 is the effective focus area Zc, the focus areas 0, 1 and 2 are candidates. Is done. Then, a focus area having the maximum luminance change rate Ef [j] among the three focus areas that are candidates is determined as the expected destination area Zt.
[0051]
Note that a focus area located on the opposite side of the predicted movement destination area Zt across the focus area 0 is determined as the monitoring target area Zm, and a threshold value to be compared with the luminance change rate Ef [j] of the monitoring target area Zm. The point that L is a fixed value is the same as described above. However, the threshold value K to be compared with the luminance change rate Ef [j] of the expected movement destination area Zt is determined as follows.
[0052]
11A and 11B, when the digital camera 10 is in the upright state, the main subject Pr existing on the focus area 1 is in any of the focus areas 0, 3 or 4. It seems to move. If the digital camera 10 is tilted by 90 °, the main subject Pr existing on the focus area 3 is considered to move to any of the focus areas 0, 1 or 2.
[0053]
On the other hand, referring to FIGS. 12A and 12B, when the digital camera 10 is in the upright state, the main subject Pr existing on the focus area 4 is not the focus area 0 but the focus area 1. Or it seems to move towards 2. If the digital camera 10 is tilted by 90 °, the main subject Pr existing on the focus area 1 seems to move toward the focus area 3 or 4 rather than the focus area 0.
[0054]
For this reason, when the main subject exists on the focus area arranged on the right side or the left side of the object scene, the lower threshold value K is assigned to all three focus areas that are candidates for the predicted destination area Zt. It is done. On the other hand, when the main subject is present on the focus area located above or below the object field, out of the three focus areas that are candidates for the expected destination area Zt, A threshold value K is assigned, and the lower threshold value K is assigned to the remaining two focus areas.
[0055]
In the movement determination, if the luminance change rate Ef [j] of the predicted destination area Zt is equal to or greater than the threshold value K and the luminance change rate Ef [j] of the monitoring target area Zm is less than the threshold value L, the main subject is “moved”. It is determined. On the other hand, the luminance change rate Ef [j] of the predicted destination area Zt is less than the threshold K, or the luminance change rate Ef [j] of the expected destination area Zt and the luminance change rate Ef [ If j] is greater than or equal to threshold value K and threshold value L, it is determined that the main subject is “no movement”.
[0056]
Note that it is determined that “no movement” when the luminance change rate Ef [j] of the predicted destination area Zt is equal to or greater than the threshold value K and the luminance change rate Ef [j] of the monitoring target area Zm is equal to or greater than the threshold value L. This change seems to be due to panning or tilting.
[0057]
However, when the moving speed of the main subject is slow, the luminance change rate Ef [j] of the predicted destination area does not reach the threshold value K even though the main subject is moving toward the predicted destination area Zt. there is a possibility. Therefore, when it is determined that there is no movement in the movement determination described above, based on the integrated values (register values) S [0] to S [4] of the luminance change rates Ef [0] to Ef [4]. It is determined whether or not the main subject has moved.
[0058]
Specifically, if any one of the focus areas 1 to 4 is the effective focus area Zc, the integrated value S [0] is set as the threshold value X. If the focus area 0 is the effective focus area Zc, one of the integrated values S [1] to S [4] is set as the threshold value X according to the attitude of the digital camera 10. That is, if the digital camera 10 is in the upright state, the larger value of the integrated values S [1] and S [2] is set as the threshold value X. If the digital camera 10 is in the 90 ° inclined state, the integrated value S [3 ] And S [4], a larger numerical value is set as the threshold value X.
[0059]
Therefore, as shown in FIG. 10A, when the digital camera 10 is in the upright state and the main subject Pr exists on the focus area 0, the integrated value S [1] or S [2] is set as the threshold value X. Is set. As shown in FIG. 10B, when the digital camera 10 is tilted and the main subject Pr exists on the focus area 0, the larger one of the integrated values S [3] or S [4] is larger. Set as threshold X. On the other hand, when the main subject Pr exists on a focus area other than the focus area 0 as shown in FIG. 11 (A), FIG. 11 (B), FIG. 12 (A), or FIG. Is set as a threshold value X.
[0060]
If the threshold value X is less than the threshold value L, the main subject is determined as “no movement”, and if the threshold value X is equal to or greater than the threshold value L, the main subject is determined as “moving”.
[0061]
When the determination result “with movement” is obtained, the effective focus area Zc is changed to the expected movement destination area Zt, and the focus is adjusted on the changed effective focus area Zc. When a determination result of “no movement” is obtained, the setting is maintained in the current effective focus area Zc.
[0062]
When the automatic tracking process as described above is performed, the aperture mechanism 14 is opened by the aperture driver 20. This is to reduce the influence of light diffraction at the opening of the aperture mechanism 14 and improve tracking accuracy.
[0063]
When the shutter button 44 shifts from the half-pressed state to the fully-pressed state, the optimum aperture amount As and the optimum exposure period Ts are set in the aperture mechanisms 14 and TG 18 respectively, and the recording process is executed. First, the CPU 24 instructs the TG 18 to perform one frame main exposure and all pixel readout, and the CPU 24 instructs the signal processing circuit 30 to perform compression processing. The TG 18 performs a main exposure according to the optimum exposure period Ts, and reads out all charges generated by the main exposure, that is, a high-resolution raw image signal for one frame from the image sensor 16.
[0064]
The read raw image signal is input to the signal processing circuit 30 via the CDS / AGC circuit 26 and the A / D converter 28, and converted into YUV data by the above-described series of processing. The converted YUV data is written into the SDRAM 34 by the memory controller 32. Thereafter, the signal processing circuit 30 reads the YUV data from the SDRAM 34 through the memory controller 32, performs JPEG compression on the read YUV data, and records the compressed image data generated by the JPEG compression on the memory card 36 in a file format.
[0065]
An example of the automatic tracking operation will be described with reference to FIGS. 13 (A) to 11 (C). As shown in FIG. 13A, from the state where the main subject Pr exists on the focus area 1 and the effective focus area Zc is set to the focus area 1, the main subject Pr is shown in FIGS. As shown in FIG. 13C, the secondary subject Se that crosses the scene toward the digital camera 10 and does not exist in the scene at the time of FIG. It is assumed that the object enters the object scene at the point of time and moves out of the object field at the point of FIG. 13B.
[0068]
When the shutter button 44 is half-pressed in a state where the automatic tracking function is enabled by the operation of the mode key 50, the CPU 24 executes processing according to the flowcharts shown in FIGS. A control program corresponding to these flowcharts is stored in the flash memory 24a.
[0069]
Referring to FIG. 14, first, posture detection processing using tilt sensor 46 is performed in step S1. As a result, it is determined whether the digital camera 10 is in the 90 ° tilted state to the right, the 90 ° tilted to the left, or the upright state. When it is determined that the inclination state is 90 ° to the right, the posture coefficient SLP is set to “1”, and when it is determined that the inclination state is 90 ° to the left, the posture coefficient SLP is set to “2”. When it is determined to be in the standing state, the posture coefficient SLP is set to “3”.
[0070]
In the subsequent step S3, AE / AF control processing is executed. Among these, the optimum exposure period Ts and the optimum aperture amount As are obtained by the AE control process. In addition, it is determined whether or not the object field is focus adjustable by AF control processing. If the determination result is affirmative, the effective focus area Zc is determined and the determined effective focus area Zc is determined. Focus on the subject. If focus adjustment is possible, a “Good” determination result is obtained, and if focus adjustment is not possible, an “NG” determination result is obtained.
[0071]
In step S5, the determination result obtained by the AF control process is determined. In step S7, it is determined whether the half-pressed state of the shutter button 44 is continued.
If the determination result is “NG”, or if the determination result is “Good” and the shutter button 34 is not half-pressed, the optimum exposure period Ts and the optimum aperture amount As are set for the main exposure in step S25. After setting the TG 18 and the aperture mechanism 14, the process is terminated. Therefore, when the shutter button 34 shifts from the half-pressed state to the fully-pressed state, the recording process is executed regardless of whether the shutter is in focus.
[0072]
If the determination result is “Good” and the shutter button 44 is half-pressed, the processing from step S9 is executed to automatically track the main subject.
[0073]
First, in step S9, variables p, q, r and register values S [0] to S [4] are set to “0”. Here, the variable p is a variable for counting the number of frames required until the Y data is stabilized after the shutter button 44 is half-pressed. The variable q is a variable for counting the capturing period of the luminance evaluation values Iy [0] to Iy [255]. The variable r is a variable for counting the number of integrated frames of the luminance change rates Ef [0] to Ef [4]. The register values S [0] to S [4] are integrated values of the luminance change rates Ef [0] to Ef [4], respectively.
[0074]
In step S11, it is determined whether or not the aperture mechanism 14 is in an open state. If YES is determined, the process proceeds directly to step S19. If NO is determined, the process proceeds to steps S19 through steps S13 to S17.
[0075]
In step S13, the optimum aperture amount A (= As) obtained in the AE control process is saved as the register value As', and in step S15, the aperture mechanism 14 is opened. In step S17, an AF exposure period Taf1 is calculated, and the calculated AF exposure period Taf1 is set in TG18.
[0076]
In step S19, it is determined whether or not the vertical synchronization signal Vsync is generated. If YES, it is determined in step S25 whether or not the half-pressed state of the shutter button 44 is maintained. If the half-pressed state is released, the process is terminated through the main exposure setting in step S25.
[0077]
If the half-pressed state of the shutter button 44 is maintained, the luminance evaluation values Iy [0] to Iy [255] are fetched from the AE / AF evaluation circuit 36 in step S25, and the variable p is set to the upper limit value P (=) in step S27. It is determined whether or not 3) has been reached. If the variable p has not yet reached the upper limit value P, the variable p is incremented in step S29, and the current luminance evaluation values Iy [0] to Iy [255] are changed to register values Iy [0] ′ to Iy [ 255] 'and then the process returns to step S19.
[0078]
When the variable p reaches the upper limit value P, the process proceeds from step S27 to step S33, and it is determined whether or not the variable q has reached the upper limit value Q (= 3). If the variable q has not yet reached the upper limit Q, the variable q is incremented in step S37, and the process returns to step S19. When the variable q reaches the upper limit Q, the variable q is returned to “0” in step S37, and the luminance change detection process is executed in step S39. The luminance change rates Ef [0] to Ef [4] of the focus areas 0 to 4 are obtained by the luminance change detection process.
[0079]
In step S41, a first movement determination process is executed. The predicted movement destination area Zt and the monitoring target area Zm are determined by the first movement determination process, and whether or not the main subject has moved is determined based on the luminance change rate Ef [j] of the predicted movement destination area Zt and the monitoring target area Zm. Is done. In step S43, it is determined whether the determination result of the first movement determination process is “with movement” or “without movement”.
[0080]
When it is determined NO, the second movement determination process is executed in step S45. Through the second movement determination process, the luminance change rates Ef [0] to Ef [4] are integrated, and whether or not the main subject has moved is determined based on the integrated values S [0] to S [4]. In step S47, it is determined whether the determination result of the second movement determination process is “with movement” or “without movement”. If NO is determined here, it is considered that no movement has occurred in the main subject, and the process directly returns to step S19.
[0081]
On the other hand, if YES is determined in any one of steps S43 and S47, AF restart processing is executed in step S49. By the AF restart process, the effective focus area Zc is updated, and focus adjustment is performed in the updated effective focus area Zc. In step S51, the register values S [0] to S [4] are returned to “0”, and in step S53, the current luminance evaluation value Iy [i] is saved as the register value Iy [i] ′. When the saving process is completed, the process returns to step S19.
[0082]
The posture detection process in step S1 shown in FIG. 14 follows a subroutine shown in FIG. First, in steps S61 and S63, the attitude of the digital camera 10 is determined based on the output of the tilt sensor 46. If the output of the tilt sensor 46 indicates “upright state”, YES is determined in step S61, and the posture coefficient SLP is set to “3” in step S65. If the output of the tilt sensor 46 indicates “a 90 ° tilt state to the right”, it is determined YES in step S63, and the posture coefficient SLP is set to “1” in step S67. If the output of the tilt sensor 46 indicates “the 90 ° tilt state in the left direction”, NO is determined in step S63, and the posture coefficient SLP is set to “2” in step S69.
[0083]
The AE / AF control process in step S3 shown in FIG. 14 follows a subroutine shown in FIGS. First, in step S71, 256 luminance evaluation values Iy [0] to Iy [255] are fetched from the AE / AF evaluation circuit 42. In step S73, the optimum exposure period Ts is calculated based on the fetched luminance evaluation values Iy [0] to Iy [255]. In step S75, the calculated optimum exposure period Ts is saved as the register value Ts ′. . In step S77, an optimal aperture amount As is calculated based on the acquired luminance evaluation values Iy [0] to Iy [255], and the aperture driver 20 is controlled to set the optimal aperture amount As in the aperture mechanism 14. The calculation of the optimum exposure period Ts and the optimum aperture amount As is performed according to the currently effective photometry method (multi-segment photometry, center-weighted photometry, spot photometry, etc.).
[0084]
When the setting is completed, a first freeze process is performed in step S79. As a result, the driving method of the image sensor 16 is determined as either the whole thinning readout or the partial thinning readout. In other words, if the object scene is bright, the whole thinning readout is maintained, and if the object scene is dark, the partial thinning readout is selected. When partial reading is selected, the memory controller 32 is instructed to stop data writing.
[0085]
In step S81, a threshold setting process is executed. Thus, threshold values C [1] to C [4] are individually assigned to the focus areas 0 to 4. Specific numerical values of the thresholds C [1] to C [4] are determined based on the scene selected by the scene selection key 48 and the posture of the digital camera 10.
[0086]
In step S83, the focus driver 22 is driven to set the focus lens 12 to the infinite position. In step S85, the focus position information fpos is set to “0” corresponding to the infinite position. Subsequently, register values Ih [0] max to Ih [4] max are set to “0” in step S87, and it is determined whether or not the vertical synchronization signal Vsync is generated in step S89.
[0087]
When the vertical synchronization signal Vsync is generated, the variable j is set to “0” in step S91, and the focus evaluation value Ih [j] is fetched from the AE / AF evaluation circuit 42 in step S93. In step S95, the fetched focus evaluation value Ih [j] is compared with the register value Ih [j] max. If it is determined that Ih [j] <Ih [j] max, the process proceeds to step S101. On the other hand, if it is determined that Ih [j] ≧ Ih [j] max, the focus evaluation value Ih [j] is set as the register value Ih [i] max in step S97, and the current focus position is determined in step S99. The information fpos is saved as the register value f [j], and then the process proceeds to step S101.
[0088]
In step S101, it is determined whether or not the variable j has reached “4”. If the variable j has not reached “4”, the variable j is incremented in step S103, and the process returns to step S93. When the variable j reaches “4”, the focus position information fpos is compared with a predetermined value NEAR corresponding to the closest position in step S105. If fpos <NEAR, the focus lens 12 is considered not to have reached the closest position, and the focus lens 12 is moved to the closest side in step S107, and the focus position information fpos is incremented in step S109. When the process of step S109 is completed, the process returns to step S99.
[0089]
By repeating the processes in steps S89 to S109 as described above, the register values f [0] to f [4] indicate the focus positions of the focus lens 12 in the focus areas 0 to 4, respectively.
[0090]
When the focus lens 12 reaches the closest position, YES is determined in step S105, and the second freeze process is executed in step S111. By the second freeze processing, the driving method of the image sensor 16 is returned to the whole thinning readout.
[0091]
In step S113, register value Ih [0] max to register value Ih [4] max are compared with threshold values C [0] to C [4], respectively, and the condition of Ih [j] max ≧ C [j] is satisfied. Detect focus area. In step S115, it is determined whether a focus area that satisfies the condition is detected, and the process proceeds to one of step S117 and step S127 depending on the determination result.
[0092]
When a focus area satisfying the condition is detected, an optimum register value f [j] is specified in step S117. Specifically, the register value f [j] corresponding to the focus area that satisfies the condition is identified as having the largest numerical value, that is, the closest value. In step S119, the focus area corresponding to the optimum register value f [j] is determined as the effective focus area Zc, and a frame indicating the effective focus area Zc is displayed on the LCD 40. In step S121, the optimum register value f [j] is returned as the focus position information fpos. In step S123, the focus lens 12 is moved to the position indicated by the focus position information fpos. In step S125, the determination result “Good” is validated. .
[0093]
On the other hand, if a focus area that satisfies the condition is not detected, a fixed value is set in the focus position information fpos in step S127. In step S129, the focus lens 12 is moved to the position indicated by the focus position information fpos. In step S131, the determination result “NG” is validated. When the process of step S125 or S131 is completed, the process returns to the upper hierarchy routine.
[0094]
The first freeze process follows a subroutine shown in FIG. First, in step S141, a luminance level y_level is calculated based on the luminance evaluation values Iy [0] to Iy [255] acquired in step S71 described above. The calculation method follows the photometry method that is currently valid. In step S143, a luminance level y_level_max corresponding to the longest exposure period Tmax is calculated based on the optimum exposure period Ts calculated in step S73 described above, the settable longest exposure period Tmax, and the luminance level y_level calculated in step S141. To do. Specifically, the calculation of Formula 1 is executed.
[0095]
[Expression 1]
y_level_max = y_level × Tmax / Ts
In step S145, the calculated luminance level y_level_max is compared with the target luminance level y_target. If y_level_max> y_target, the darkness ratio night_ratio is set to “0” in step S157, and if y_level_max ≦ y_target, the darkness ratio night_ratio is calculated in accordance with Equation 2 in step S159.
[0096]
[Expression 2]
night_ratio =
100 (1-y_level_max / y_target)
When the process of step S147 or S149 is completed, the darkness ratio night_ratio is compared with the threshold value B in step S151. If night_ratio> B, it is considered that the object scene is sufficiently bright, and the process proceeds to step S163.
In step S163, an AF exposure period Taf1 suitable for the entire thinning readout which is the current driving method is calculated, and the calculated exposure period Taf1 is set to TG18. When the setting is completed, the routine returns to the upper-level routine.
[0097]
On the other hand, if night_ratio ≦ B, it is considered that the brightness of the object scene is insufficient, and the generation of the vertical synchronization signal Vsync is awaited in step S153. When the vertical synchronization signal Vsync is generated, the memory controller 32 is instructed to stop data writing in step S155. The memory controller 32 performs only data reading, and the display on the LCD 40 transitions from a through image to a freeze image (still image). In step S157, the TG 18 is instructed to perform partial reading, and in step S159, the generation of the vertical synchronization signal Vsync is awaited. When the vertical synchronization signal Vsync is generated, the process proceeds to step S161, where the calculation of the AF exposure period Taf2 suitable for the partial drawing readout method and the setting of the calculated exposure period Taf2 to the TG 18 are performed. When the setting is completed, the routine returns to the upper level routine.
[0098]
The threshold value setting process in step S81 shown in FIG. 17 follows a subroutine shown in FIG. First, the selection state of the scene selection key 48 is detected in step S171, and it is determined what scene is selected in steps S173, S177, and S179. If the default scene has been selected, the process proceeds from step S173 to step S175, where the threshold value THa is set as the threshold value C [0], and the threshold value THb is set as the threshold values C [1] to C [4]. When the process of step S175 is completed, the process returns to the upper layer routine.
[0099]
If a portrait scene has been selected, “YES” is determined in the step S177, and a first threshold value determining process is executed in a step S181. If a sports scene has been selected, “YES” is determined in the step S179, and a second threshold value determining process is executed in a step S183. If a landscape scene, an evening scene, or a night scene is selected, NO is determined in step S179, and the third threshold value determining process is executed in step S185. When the process of step S181, S183, or S185 is completed, the process returns to the upper layer routine.
[0100]
The first threshold value determination process in step S181 follows a subroutine shown in FIG.
First, the slope coefficient SLP is determined in steps S201 and S205. If the slope coefficient SLP is “1”, the process proceeds from step S201 to step S203, the threshold THa is set as the threshold C [0], and the threshold THb is set as the threshold C [1], C [3] or C [4]. Then, the threshold value THd is set as the threshold value C [2]. If the slope coefficient SLP is “2”, the process proceeds from step S205 to step S207, the threshold value THa is set as the threshold value C [0], and the threshold value THb is set as the threshold value C [2], C [3] or C [4]. Then, the threshold value THd is set as the threshold value C [1].
[0101]
If the slope coefficient SLP is “3”, the process proceeds from step S205 to step S209, the threshold THa is set as the threshold C [0], and the threshold THb is set as the threshold C [1], C [2] or C [4]. Then, the threshold value THd is set as the threshold value C [3]. When the process of step S203, S207 or S209 is completed, the process returns to the upper hierarchy routine.
[0102]
The second threshold value determination process in step S183 follows a subroutine shown in FIG.
First, the slope coefficient SLP is determined in steps S211 and S215. If the slope coefficient SLP is “1”, the process proceeds from step S211 to step S213, the threshold value THa is set as the threshold value C [0], and the threshold value THb is set as the threshold value C [1], C [3] or C [4]. Then, the threshold value THc is set as the threshold value C [2]. If the slope coefficient SLP is “2”, the process proceeds from step S215 to step S217, the threshold THa is set as the threshold C [0], and the threshold THb is set as the threshold C [2], C [3] or C [4]. Then, the threshold value THc is set as the threshold value C [1].
[0103]
If the slope coefficient SLP is “3”, the process proceeds from step S215 to step S219, where the threshold THa is set as the threshold C [0], and the threshold THb is set as the threshold C [1], C [2] or C [4]. Then, the threshold THc is set as the threshold C [3]. When the process of step S213, S217, or S219 is completed, the process returns to the upper hierarchy routine.
[0104]
The third threshold value determination process in step S185 follows a subroutine shown in FIG.
First, the slope coefficient SLP is determined in steps S221 and S225. If the slope coefficient SLP is “1”, the process proceeds from step S221 to step S223, the threshold THa is set as the threshold C [0], the threshold THb is set as the threshold C [3] or C [4], and the threshold C The threshold THc is set as [1], and the threshold THd is set as the threshold C [2]. If the slope coefficient SLP is “2”, the process proceeds from step S215 to step S217, the threshold THa is set as the threshold C [0], the threshold THb is set as the threshold C [3] or C [4], and the threshold C The threshold value THd is set as [1], and the threshold value THc is set as threshold value C [2].
[0105]
If the slope coefficient SLP is “3”, the process proceeds from step S215 to step S219, the threshold THa is set as the threshold C [0], the threshold THb is set as the threshold C [1] or C [2], and the threshold C The threshold value THd is set as [3], and the threshold value THc is set as threshold value C [4]. When the process of step S223, S227, or S229 is completed, the process returns to the upper layer routine.
[0106]
The second freeze process in step S111 shown in FIG. 19 follows a subroutine shown in FIG. First, in step S231, it is determined whether or not the memory controller 32 has stopped data writing. If “NO” is determined here, the process directly returns to the upper-level routine.
[0107]
On the other hand, if “YES” is determined, the TG 18 is instructed to read the entire thinned out in step S233. When the vertical synchronization signal Vsync is generated, the process proceeds from step S235 to step S237, and the calculation of the AF exposure period Taf1 suitable for the entire thinning readout and the setting of the calculated exposure period Taf1 to the TG 18 are performed. When the vertical synchronization signal Vsync is generated again, the process proceeds from step S239 to step S241 to command the memory controller 32 to resume data writing. By resuming data writing, the display on the LCD 40 transitions from the freeze image to the through image. When the process of step S241 is completed, the process returns to the upper layer routine.
[0108]
The luminance change detection process in step S39 shown in FIG. 15 follows a subroutine shown in FIG. First, in step S251, the luminance evaluation values Iy [0] to Iy [255] fetched in step S23 of FIG. 14 and the register values Iy [0] ′ to Iy [255] previously saved in step S31 of FIG. ] ′ And an arithmetic operation according to Equation 3 are performed to obtain luminance differences ΔIy [0] to Iy [255] of the respective blocks.
[0109]
[Equation 3]
ΔIy [i] = | Iy [i] −Iy [i] ′ |
However, i = 0 to 255
In step S253, the luminance differences ΔIy [0] to Iy [255] and the register values Iy [0] ′ to Iy [255] ′ calculated according to the equation 3 are subjected to an operation according to the equation 4, and the luminance change rate of each block E [0] to E [255] are calculated.
[0110]
[Expression 4]
E [i] = (ΔIy [i] / Iy [i] ′) × 100
However, i = 0 to 255
In step S255, the luminance change rate E [i] of the blocks belonging to the focus area 0 is averaged to obtain the luminance change rate Ef [0], and the luminance change rates E [i] of the blocks belonging to the focus area 1 are averaged. The luminance change rate Ef [1] is obtained, and the luminance change rate Ef [2] of the blocks belonging to the focus area 2 is averaged to obtain the luminance change rate Ef [2]. Also, the luminance change rate E [i] of the blocks belonging to the focus area 3 is averaged to obtain the luminance change rate Ef [3], and the luminance change rate E [i] of the blocks belonging to the focus area 4 is averaged to change the luminance. The rate Ef [4] is obtained. When the process of step S255 is completed, the process returns to the upper layer routine.
[0111]
The first movement determination process in step S41 shown in FIG. 15 follows a subroutine shown in FIGS. First, in step S261, it is determined whether or not the effective focus area Zc is set to the focus area 0. If YES is determined, the process proceeds to step S263, and the focus area having the maximum luminance change rate Ef [j] among the invalid focus areas 1 to 4 is determined as the predicted destination area Zt. In the subsequent step S265, the slope coefficient SLP is determined.
[0112]
If the slope coefficient SPL is “3”, the digital camera 10 is considered to be in an upright state, and the threshold value K is determined in step S267. Specifically, the threshold value K of the focus area 1 or 2 is determined to be a predetermined value k, and the threshold value K of the focus area 3 or 4 is determined to be twice the predetermined value k. On the other hand, if the inclination coefficient SPL is “1” or “2”, the digital camera 10 is considered to be in the 90 ° inclination state, and the threshold value K is determined in step S269. Specifically, the threshold value K of the focus area 1 or 2 is determined to be twice the predetermined value k, and the threshold value K of the focus area 3 or 4 is determined to be the predetermined value k.
[0113]
When the process of step S267 or S269 is completed, the process proceeds to step S271, where the luminance change rate Ef [j] and the threshold value K of the predicted destination area Zt are compared with each other. If Ef [j] <K, it is determined in step S279 that the main subject is “no movement”, and the process returns to the upper hierarchy routine. On the other hand, if Ef [j] ≧ K, the monitoring target area Zm is determined in step S273. Specifically, if the focus area 1 is the expected movement destination area Zt, the focus area 2 is the monitoring target area Zm, and if the focus area 2 is the expected movement destination area Zt, the focus area 1 is the monitoring target area Zm. If the focus area 3 is the expected movement destination area Zt, the focus area 4 is the monitoring target area Zm. If the focus area 4 is the expected movement destination area Zt, the focus area 3 is the monitoring target area Zm.
[0114]
In step S275, the luminance change rate Ef [j] in the determined monitoring target area Zm is compared with the threshold value L. If Ef [j] <L, the main subject is determined to be “moved” in step S277. On the other hand, if Ef [j] ≧ L, the main subject is determined as “no movement” in step S279. When the process of step S277 or S279 is completed, the process returns to the upper hierarchy routine.
[0115]
If NO is determined in step S261, a candidate for the predicted destination area Zt is determined in step S281. Specifically, if the focus area 1 or 2 is the effective focus area Zc, the invalid focus areas 0, 3 and 4 are set as candidates for the expected destination area Zt. If the focus area 3 or 4 is the effective focus area Zc, the invalid focus areas 0, 1 and 2 are candidates for the expected movement destination area Zt. In step S283, the focus area having the maximum luminance change rate E [j] among the determined candidates is determined as the expected destination area Zt.
[0116]
In step S285, the slope coefficient SLP is determined. If the slope coefficient SLP is “3”, the process proceeds to step S287, and if the slope SLP is “1” or “2”, the process proceeds to step S289. In step S287, the setting destination of the effective focus area Zc is determined. If the effective focus area Zc is set to the focus area 1 or 2, the candidate threshold value K of the expected movement destination area Zt is determined in step S291, and the effective focus area Zc is set to the focus area 3 or 4. In step S293, a candidate threshold value K for the predicted destination area Zt is determined.
[0117]
Also in step S289, the effective focus area setting destination is determined in the same manner as in step S287. If the effective focus area Zc is set to the focus area 1 or 2, the candidate threshold value K of the expected movement destination area Zt is determined in step S295, and the effective focus area Zc is set to the focus area 3 or 4. In step S297, a candidate threshold value K for the predicted destination area Zt is determined.
[0118]
In step S291, the threshold value K of the focus area 0, 3 or 4 is determined to be a predetermined value k. In step S293, the threshold value K of the focus area 0 is determined to be twice the predetermined value k, and the threshold value K of the focus area 1 or 2 is determined to be the predetermined value k. In step S295, the threshold value K of the focus area 0 is determined to be twice the predetermined value k, and the threshold value K of the focus area 3 or 4 is determined to be the predetermined value k. In step S297, the threshold value K of the focus area 0, 1 or 2 is determined to be a predetermined value k.
[0119]
When the processes of steps S291 to S297 are completed, the processes of steps S299 to S307 are executed. Since these processes are the same as the above-described steps S271 to S279, a duplicate description is omitted.
[0120]
The second movement determination process in step S45 shown in FIG. 15 follows the subroutine shown in FIGS. First, change rate integration processing is performed in step S311. Through the change rate integration process, the luminance change rate Ef [j] of the focus area specified according to the effective focus area Zc and the posture of the digital camera 10 among the focus areas 0 to 4 is integrated. The integration results of the luminance change rates Ef [0] to Ef [4] are held as register values S [0] to S [4]. Further, the variable r is incremented by the change rate integration process.
[0121]
In step S313, it is determined whether or not the variable r has reached the upper limit value R. If the variable r has not reached the upper limit value R, the determination result of “no movement” is validated in step S339 and then the upper level routine is entered. Return.
[0122]
When the variable r reaches the upper limit value R, the variable r is returned to “0” in step S315, and it is determined whether or not the focus area 0 is the effective focus area Zc in step S317. If any one of the focus areas 1 to 4 is the effective focus area Zc, the register value S [0] is set as the integrated value X in step S319. On the other hand, if the focus area 0 is the effective focus area Zc, the process proceeds to step S321, and the attitude of the digital camera 10 is determined based on the attitude coefficient SLP.
[0123]
If the attitude coefficient SLP is “3”, the digital camera 10 is considered to be in an upright state, and the register values S [1] and S [2] are compared with each other in step S329. If S [1] ≧ S [2], the register value S [1] is set as the integrated value X in step S331. If S [1] <S [2], the register value S [ 2] is set as the integrated value X.
[0124]
On the other hand, if the attitude coefficient SLP is “1” or “2”, the digital camera 10 is considered to be in a 90 ° tilt state, and the register values S [3] and S [4] are compared with each other in step S325. To do. If S [3] ≧ S [4], the register value S [3] is set as the integrated value X in step S325. If S [3] <S [4], the register value S [ 4] is set as the integrated value X.
[0125]
When the integrated value X is determined, the integrated value X is compared with a threshold value M in step S335. If the integrated value X is greater than or equal to the threshold value M, the determination result of “with movement” is validated in step S337 and the process returns to the upper hierarchy routine. If the integrated value X is less than the threshold value M, “moving” is performed in step S339. After enabling the determination result of “None”, the process returns to the upper-level routine.
[0126]
The change rate integration process in step S311 follows a subroutine shown in FIGS. First, in step S341, the setting destination of the effective focus area Zc is determined.
If the focus area 0 is the effective focus area Zc, the slope coefficient SLP is determined in step S343. When the slope coefficient SLP is “3”, the process proceeds to step S345, and the luminance change rate Ef [1] of the focus area 1 and the luminance change rate Ef [2] of the focus area 2 are individually integrated. Specifically, an operation according to Equation 5 is executed.
[0127]
[Equation 5]
S [1] = S [1] + Ef [1]
S [2] = S [2] + Ef [2]
When the slope coefficient SLP is “1” or “2”, the process proceeds to step S347, and the luminance change rate Ef [3] of the focus area 3 and the luminance change rate Ef [4] of the focus area 4 are individually integrated. Specifically, the calculation according to Equation 6 is executed.
[0128]
[Formula 6]
S [3] = S [3] + Ef [3]
S [4] = S [4] + Ef [4]
When the calculation of Equation 5 or Equation 6 is completed, the variable r is incremented in Step S349, and then the process returns to the upper hierarchy routine.
[0129]
If any one of the focus areas 1 to 4 is the effective focus area Zc, the slope coefficient SLP is determined in step S351. When the inclination coefficient SLP is “3”, the setting destination of the effective focus area Zc is determined in step S355. If the focus area 3 or 4 is the effective focus area Zc, the process proceeds to step S359 as it is. If the focus area 1 or 2 is the effective focus area Zc, the luminance change rate Ef [ 0] is added, and then the process proceeds to step S349.
[0130]
[Expression 7]
S [0] = S [0] + Ef [0]
When the slope coefficient SLP is “1” or “2”, the setting destination of the effective focus area Zc is determined in step S353. If the focus area 1 or 2 is the effective focus area Zc, the process directly proceeds to step S349. If the focus area 3 or 4 is the effective focus area Zc, the process proceeds to step S349 via step S357.
[0131]
The AF restart process in step S49 shown in FIG. 15 follows a subroutine shown in FIG. First, in step S361, the effective focus area Zc is changed to the current expected movement destination area Zt, and a frame indicating the changed effective focus area Zc is displayed on the LCD 40. In step S363, focus adjustment is performed in the changed effective focus area Zc. When the adjustment is completed, the variable p is returned to “0” in step S365, and then the routine returns to the upper hierarchy. Note that, in the focus adjustment in step S363, the image sensor 14 is subjected to overall thinning readout.
[0132]
As can be understood from the above description, when the effective focus area Zc used for focus adjustment is first determined from among the focus areas 0 to 4 arranged in the object field, the maximum focus obtained in each of the focus areas 0 to 4 is determined. Evaluation values Ih [0] max to Ih [4] max are compared with threshold values C [0] to C [4] assigned to the focus areas 0 to 4, respectively. Here, the assignment destination of the thresholds THa, THb, THc or THd set as the thresholds C [0] to C [4] is changed by the CPU 24 based on the detection result of the tilt sensor 46, that is, the camera posture. That is, the focus areas 0 to 4 are arranged radially with respect to the center of the object scene, and the assignment destinations of the thresholds THa, THb, THc, or THd are rotated according to the camera posture.
[0133]
Thus, by changing the assignment destination of the thresholds THa, THb, THc, or THd based on the camera posture, the focus can be accurately adjusted regardless of the camera posture. Further, three focus areas 0 to 4 are arranged in the vertical direction and the horizontal direction, and the tilt sensor 46 determines whether the camera posture is in the upright state or the 90 ° tilt state, and the CPU 24 determines the thresholds THa and THb. , THc or THd is rotated by 90 °, so that even if the tilt sensor 46 has a low performance that can only discriminate between the upright state and the 90 ° tilt state, the threshold THa, THb, THc or THd is accurately assigned. Is possible.
[0134]
Further, the charge corresponding to the optical image of the object scene is periodically read from the entire light receiving surface of the image sensor 16. In the SDRAM 34, YUV data based on the electric charges read from the image sensor 16 is written. An image based on the YUV data stored in the SDRAM 34 is displayed on the LCD 40. However, when the shutter button 44 is operated, the brightness of the object scene is determined. If the brightness is sufficient, the CPU 24 activates a specific setting state in which the charge is read from the central area of the light receiving surface of the image sensor 16 and the writing of YUV data to the SDRAM 34 is prohibited.
[0135]
The focus is adjusted based on the electric charge read from the image sensor 16 after the specific setting state is validated. When the focus adjustment is completed, the specific setting state is canceled by the CPU 24. As a result, charges are periodically read from the entire light receiving surface of the image sensor 16, and YUV data based on the read charges is written into the SDRAM 34. The display on the LCD 40 changes from a freeze image to a real-time moving image of the object scene.
[0136]
By reading out the electric charge from the central area of the image sensor 16, the reading cycle is shortened. Further, by prohibiting the writing of the YUV data based on the electric charges read from the central area to the SDRAM 34, the display on the LCD 40 shifts from a through image of the entire object scene to a freeze image. By shortening the readout cycle, it is possible to speed up the focus adjustment. Moreover, although it is a freeze image, since the image of the whole object scene is displayed on LCD34, the fall of operativity can be suppressed.
[0137]
Note that since the speed of focus adjustment is increased, the time for which the freeze image is displayed is short, and the operator is not significantly discomforted. Further, since the specific setting state is validated due to the manual operation of the operator, the monitor display does not transition from the through image to the frozen image at a timing not intended by the operator.
[0138]
When the half-pressed state of the shutter button 44 continues, the main subject automatic tracking function is activated. At this time, the CPU 24 individually calculates the luminance change rate Ef [j] for a plurality of invalid focus areas other than the effective focus area Zc among the focus areas 0 to 4, and the movement of the subject existing in the plurality of invalid focus areas. To evaluate. Further, the CPU 24 determines whether or not the main subject has moved based on the calculated luminance change rate Ef [j] and a plurality of threshold values K respectively assigned to the plurality of invalid focus areas. When the main subject moves, the effective focus area Zc is changed. The focus is adjusted based on the effective focus area Zc thus changed. Here, the numerical value indicated by each of the plurality of threshold values K is changed according to the position of the effective focus area Zc so as to reflect the possibility of movement of the main subject.
[0139]
Specifically, when the focus area 3 or 4 is the effective focus area Zc when the digital camera 10 is in the upright state, the threshold value K of the focus area 1 or 2 is set lower than the threshold value of the focus area 0. . This is because when the main subject is located above or below the center of the scene, the main subject moves in an oblique direction rather than in the vertical direction of the scene.
[0140]
If the focus area 1 or 2 is the effective focus area Zc when the digital camera 10 is in the upright state, the threshold values K of the focus areas 0, 3 and 4 are set to the same numerical value. This is because when the main subject is located at the center right side or the center left side of the scene, the main subject may move in both the horizontal and diagonal directions of the scene. .
[0141]
Further, if the focus area 0 is the effective focus area when the digital camera 10 is in the upright state, the threshold value K of the focus area 1 or 2 is set lower than the focus area 3 or 4 threshold value. This is because when the main subject is located at the center of the object scene, the main subject moves in the horizontal direction rather than in the vertical direction of the object scene.
[0142]
In this way, by changing the value of the threshold value K in consideration of the possibility of movement of the main subject, it is possible to improve the accuracy of determining whether or not the main subject has moved, and to focus the main subject reliably. Become.
[0143]
In this embodiment, only the focus lens 12 is moved in the optical axis direction for focus adjustment. Instead, only the image sensor 16 or both the focus lens 12 and the image sensor 16 are optical axes. You may make it move to a direction.
[0144]
In this embodiment, the scene is selected according to the operation of the scene selection key 48, but the scene may be automatically determined.
[0145]
Further, the inclination sensor 46 of this embodiment can only determine one of the upright state, the right 90 ° inclination state, and the left 90 ° inclination state, but a sensor with higher accuracy may be used. Then, by assigning innumerable focus areas extending radially from the center of the object field to the object field, it is possible to rotate the numerical assignments indicated by the thresholds C [0] to C [4] in small increments. It becomes.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is an illustrative view showing one example of distribution states of focus areas 0 to 4 and a central area formed on a screen.
FIG. 3A is an illustrative view showing one example of setting states of threshold values C [0] to C [4] when a portrait scene is selected, and FIG. 3B is a diagram showing that a portrait scene is selected; FIG. 10 is an illustrative view showing another example of setting states of threshold values C [0] to C [4] when (C) shows threshold values C [0] to C [4] when a portrait scene is selected. It is an illustration figure which shows another example of a setting state.
4A is an illustrative view showing an example of a setting state of threshold values C [0] to C [4] when a sports scene is selected, and FIG. 4B is a diagram when a sports scene is selected. It is an illustration figure which shows another example of the setting state of threshold value C [0] -C [4], (C) is the setting state of threshold value C [0] -C [4] when a sports scene is selected. It is an illustration figure which shows another example.
5A is an illustrative view showing an example of setting states of threshold values C [0] to C [4] when a landscape scene, an evening scene, or a night scene is selected, and FIG. 5B is a landscape scene; , Is an illustrative view showing another example of setting states of thresholds C [0] to C [4] when an evening scene or a night scene is selected, and (C) is a scene scene, evening scene or night scene selected It is an illustration figure which shows another example of the setting state of threshold value C [0] -C [4] when being done.
6A is an illustrative view showing one example of setting states of threshold values C [0] to C [4] when a default scene is selected, and FIG. 6B is a diagram when a default scene is selected. It is an illustration figure which shows another example of the setting state of threshold value C [0] -C [4], (C) is the setting state of threshold value C [0] -C [4] when a default scene is selected. It is an illustration figure which shows another example.
FIG. 7A is an illustrative view showing an example of an object scene shot with a portrait scene selected, and FIG. 7B shows an object scene shot with a portrait scene selected. It is an illustration figure which shows another example.
FIG. 8 is an illustrative view showing one example of an object scene photographed in a state where a sports scene is selected.
FIG. 9 is an illustrative view showing one example of a scene that is shot in a state in which a landscape mode, an evening scene mode, or a night scene is selected.
FIG. 10A is an illustrative view showing one example of the tracking operation of the main subject, and FIG. 10B is an illustrative view showing another example of the tracking operation of the main subject.
11A is an illustrative view showing another example of the tracking operation of the main subject, and FIG. 11B is an illustrative view showing still another example of the tracking operation of the main subject.
12A is an illustrative view showing another example of the tracking operation of the main subject, and FIG. 12B is an illustrative view showing another example of the tracking operation of the main subject.
FIG. 13A is an illustrative view showing a part of a series of operations for tracking a main subject, and FIG. 13B is an illustrative view showing another part of a series of operations for tracking a main subject; (C) is an illustrative view showing another part of a series of operations for tracking a main subject.
FIG. 14 is a flowchart showing a part of the operation of FIG. 1 embodiment;
15 is a flowchart showing another portion of the operation of the embodiment in FIG. 1; FIG.
FIG. 16 is a flowchart showing still another portion of the operation of FIG. 1 embodiment;
FIG. 17 is a flowchart showing yet another portion of the operation of FIG. 1 embodiment;
FIG. 18 is a flowchart showing another portion of the operation of the embodiment in FIG. 1;
FIG. 19 is a flowchart showing still another portion of the operation of FIG. 1 embodiment;
FIG. 20 is a flowchart showing still another portion of the operation of the embodiment in FIG. 1;
FIG. 21 is a flowchart showing another portion of the operation of the embodiment in FIG. 1;
22 is a flowchart showing still another portion of the operation of FIG. 1 embodiment. FIG.
FIG. 23 is a flowchart showing yet another portion of the operation of the embodiment in FIG. 1;
24 is a flowchart showing another portion of the operation of the embodiment in FIG. 1; FIG.
FIG. 25 is a flowchart showing still another portion of the operation of the embodiment in FIG. 1;
FIG. 26 is a flowchart showing yet another portion of the operation of the embodiment in FIG. 1;
FIG. 27 is a flowchart showing another portion of the operation of the embodiment in FIG. 1;
FIG. 28 is a flowchart showing still another portion of the operation of FIG. 1 embodiment;
FIG. 29 is a flowchart showing yet another portion of the operation of FIG. 1 embodiment;
30 is a flowchart showing another portion of the operation of the embodiment in FIG. 1; FIG.
FIG. 31 is a flowchart showing still another portion of the operation of FIG. 1 embodiment;
32 is a flowchart showing yet another portion of the operation of the embodiment in FIG. 1. FIG.
[Explanation of symbols]
10. Digital camera
12 ... Focus lens
14: Aperture mechanism
24 ... CPU
42. AE / AF evaluation circuit
44 ... Tilt sensor
48 ... Scene selection key

Claims (5)

First determining means for determining, as an effective focus area in which a main subject exists, one focus area that satisfies the first area condition among a plurality of focus areas assigned to the object field when focus adjustment is instructed ;
Adjusting means for performing focus adjustment based on the effective focus area;
Second determining means for determining one focus area that is different from the effective focus area and satisfies the second area condition among the plurality of focus areas as an expected destination focus area that is expected to be a destination of the main subject;
Third determining means for determining the predicted movement destination focus area as the effective focus area when a luminance change condition is satisfied; and a numerical value different depending on a direction in which the effective focus area is adjacent to the predicted movement destination focus area An application means for applying to the luminance change condition is provided.
The first area condition is a condition that the position of the focus lens at which the focus evaluation value is maximum exists on the closest side,
The second area condition is a condition that a luminance change rate is maximum in a focus area adjacent to the effective focus area,
The luminance change condition can be satisfied when a first threshold condition that a luminance change rate of the predicted destination focus area is equal to or greater than a first threshold is satisfied, and the applying unit sets the numerical value to the first threshold. Autofocus camera to set.   The plurality of focus areas include a center position focus area arranged at the center of the object scene, a vertical position focus area arranged at a position extending in the vertical direction from the center of the object scene, and the object field. An autofocus camera according to claim 1, further comprising a horizontal position focus area arranged at a position extending horizontally from the center of the camera. A fourth deciding means for deciding, as a monitoring target focus area, a focus area having a predetermined positional relationship with the predicted destination focus area among the plurality of focus areas;
The predetermined positional relationship is a positional relationship in which the effective focus area is adjacent to the effective focus area on a side different from a side adjacent to the predicted destination focus area.
3. The autofocus camera according to claim 1, wherein the luminance change condition can be satisfied when a second threshold condition that a luminance change rate of the focus area to be monitored is lower than a second threshold is satisfied. . The autofocus camera according to claim 3 , wherein the luminance change condition corresponds to a logical product of the first threshold condition and the second threshold condition. It further comprises detection means for detecting the tilt state of the camera body in the direction around the optical axis,
Each of the plurality of focus areas has an identifier;
Said applying means determines the numerical value based on a detection result of said detecting means and the effective focus area and each of the identifier of the expected movement destination focus area, according to any one of claims 1 to 4 autofocus camera .

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