JP2016109766A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device that can improve a performance of a tracking AF with respect to a subject.SOLUTION: A plurality of grating-like small regions is set with respect to a frame image, and an intermediate AF evaluation value is created for each of the small regions. Meanwhile, an AF evaluation frame is set with respect to a region corresponding to a position of a subject obtained by tracking detection. Then, a final AF evaluation value is created using the set AF evaluation frame and intermediate AF evaluation value, and on the basis of the created final AF evaluation value, a position of a focus lens is adjusted to perform an AF control.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an imaging apparatus, and more particularly to an autofocus control technique in the imaging apparatus.

  In the imaging apparatus, a subject area is detected from the face position and luminance / color distribution information obtained by the face recognition process, and an evaluation frame for autofocus (AF) is set at the position of the main subject estimated from the subject area. Thus, a technique for performing AF on the main subject has been proposed. For example, Patent Document 1 discloses a technique for realizing AF that can track a movement even if the main subject is slightly lost by tracking the position of the main subject as an AF target from image data of a peripheral part of the face detection position. Has been.

  In Patent Document 2, the position of the main subject is tracked, the moving direction of the subject is predicted, and a wider AF evaluation frame is set for the predicted direction, whereby an AF evaluation frame for the moving main subject is set. A technique for increasing the capture probability of an image is disclosed.

JP 2013-11766 Gazette JP 2006-129272 A

  However, in the technique of Patent Document 1, no consideration is given to the influence on the tracking AF performance from the acquisition of the captured image until the tracking result of the position of the main subject is obtained. Conventionally, two AF methods, a contrast evaluation method and a phase difference detection method, are known. In either AF method, the focus lens focus state is estimated from a captured image for AF evaluation (which is also used for display / recording during moving image capture), and the captured image of the next frame is acquired. Move the focus lens to the estimated focus position.

  On the other hand, since the technique of Patent Document 1 obtains the tracking result of the position of the main subject from the captured image, an AF evaluation frame cannot be set for the position of the main subject in the captured image. The AF evaluation frame can be reflected on the position of the main subject in the captured image in the captured image of the next frame. The position of the main subject in the captured image of the next frame is one frame before. There is no guarantee that the position of the main subject is the same as the captured image. As described above, the technique of Patent Document 1 cannot essentially realize tracking AF to the main subject.

  In addition, since the technique of Patent Document 2 is a technique that merely sets a wider AF evaluation frame in the moving direction of the subject, it can be guaranteed that the AF evaluation frame can be set at the position of the main subject in the captured image. I can't get it. Further, since a wider AF evaluation frame is set with respect to the main subject, there is a problem that the probability of occurrence of perspective conflicts increases, and it cannot be said that the technique improves the AF performance comprehensively.

  The present invention has been made in view of the above problems, and an object thereof is to provide an imaging apparatus capable of improving the performance of tracking AF to a subject.

  In order to achieve the above object, an imaging apparatus of the present invention is generated by an imaging unit including a focus lens, a subject tracking unit that generates data indicating the position of a subject from an output signal of the imaging unit, and the subject tracking unit. Set by an AF evaluation frame setting means for setting an AF evaluation frame from the obtained data, a first generation means for generating a first AF evaluation value from the output signal of the imaging means, and the AF evaluation frame setting means Second generation means for generating a second AF evaluation value using the AF evaluation frame and the first AF evaluation value generated by the first generation means, and the second generation means generated by the second generation means. Control means for performing AF control by adjusting the position of the focus lens based on the AF evaluation value of 2.

  According to the present invention, it is possible to generate a contrast AF evaluation value in a state in which the position of the main subject is tracked, and it is possible to improve the performance of tracking AF on the subject.

1 is a block diagram illustrating a schematic configuration of an imaging apparatus according to a first embodiment of the present invention. It is a block diagram which shows schematic structure of the 1st contrast evaluation calculating part in FIG. FIG. 3 is a diagram showing a schematic configuration of a first contrast evaluation calculation subcircuit in FIG. 2. (A) is a diagram showing an example of setting a first contrast evaluation calculation frame, (b) is a diagram showing an example of a first contrast evaluation value. It is a timing chart for demonstrating operation | movement of a 1st contrast evaluation calculating part. FIG. 4A is a diagram illustrating an example of a subject tracking AF evaluation area, and FIG. 5B is a diagram illustrating another example of a subject tracking AF evaluation area. 3 is a timing chart for explaining the operation of the imaging apparatus of FIG. 1. (A) A figure showing an example of subject tracking AF evaluation field in a 2nd embodiment, (b) A figure showing another example of subject tracking AF evaluation field. It is a block diagram which shows schematic structure of the imaging device which concerns on the 3rd Embodiment of this invention. It is a block diagram which shows schematic structure of the reliability calculating part in FIG. It is a block diagram which shows schematic structure of the 1st reliability calculation subcircuit in FIG. (A) The figure which shows an example of the subject tracking AF evaluation area | region in 3rd Embodiment, (b) The figure which shows an example of an object tracking AF reliability result, (c) The figure which shows another example of an object tracking AF evaluation area | region It is. It is a block diagram which shows schematic structure of the imaging device which concerns on the 4th Embodiment of this invention. It is a figure which shows the time transition of the focus lens position of the imaging device which concerns on the 4th Embodiment of this invention. It is a figure which shows the mode of the blur spread of the main subject which arises by the change of the focus state with respect to the main subject.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of an imaging apparatus according to the first embodiment of the present invention.

  In FIG. 1, the imaging apparatus includes a focus lens 101, a sensor (imaging device) 102, a camera signal processing unit 103, a display / recording processing unit 104, a display device 105, a recording medium 106, and a tracking detection unit 107. The imaging apparatus also includes a first memory interface 108, a memory that holds tracking evaluation value data 109, a second memory interface 110, a contrast evaluation filter 111, a first contrast evaluation calculation unit 112, and a third memory interface 113. Furthermore, the imaging apparatus includes a memory that holds the first contrast evaluation value data 114, a fourth memory interface 115, a second contrast evaluation calculation unit 116, a microcomputer 117, a lens driving actuator 118, and a video synchronization generation unit 119.

  In the imaging apparatus of FIG. 1, an optical image of a subject (not shown) is formed on the imaging surface of the sensor 102 via the focus lens 101, and a sensor output signal S <b> 101 is output from the sensor 102. The sensor output signal S101 output from the sensor 102 is input to the camera signal processing unit 103, the tracking detection unit 107, and the contrast evaluation filter 111, respectively.

  The camera signal processing unit 103 performs camera signal processing such as color separation, gamma correction, and white balance adjustment (not shown) on the input sensor output signal S101 to generate a camera processed image signal S102, and performs display / recording processing. Output to the unit 104.

  The display / recording processing unit 104 generates a display image signal S103 and recording image data S104 from the input camera processing image signal S102, and outputs the display image signal S103 to the display device 105 to display an image or the like. Further, the display / recording processing unit 104 records the recording image data S104 on the recording medium 106.

  The tracking detection unit 107 detects the position of the main subject from the input sensor output signal S101 based on, for example, a human face or a specific color area. Further, the tracking detection unit 107 tracks the position of the main subject in the past frame and the position of the main subject using a known technique such as template matching processing, and generates tracking detection light data S105. The tracking detection write data S105 is stored in the external memory such as a DRAM as tracking evaluation value data 109 via the first memory interface 108.

  As is known, the contrast evaluation filter 111 is a band-pass filter having a frequency characteristic that drops at least a DC component and a color carrier component by a color filter (not shown) of the sensor 102 to null. Then, the contrast evaluation filter 111 generates a filtered image signal S107 and outputs it to the first contrast evaluation calculation unit 112. This filtered image signal S107 is a signal of a spatially filtered image that is optimal for evaluating the subject edge sharpness included in the sensor output signal S101, and the energy of the image depends on the focus state by the focus lens 101. It has changing characteristics.

  In order to evaluate the energy of the image, the first contrast evaluation calculation unit 112 performs an absolute value integration calculation process on the input filtered image signal S107 and outputs the result as first contrast evaluation light data S108. The first contrast evaluation write data S108 is stored in an external memory such as a DRAM as first contrast evaluation value data 114 via the third memory interface 113.

  The tracking evaluation value data 109 described above is read to the microcomputer 117 as tracking detection read data S106 via the second memory interface 110. Since the tracking evaluation value data 109 is data representing the position of the main subject in the sensor output signal S101, the microcomputer 117 generates an AF evaluation frame setting S110 from the tracking detection lead data S106. The AF evaluation frame setting S110 is sent to the second contrast evaluation calculation unit 116.

  The second contrast evaluation calculation unit 116 reads the first contrast evaluation value data 114 once stored in the external memory such as the DRAM as the first contrast evaluation read data S109 via the fourth memory interface 115. Then, based on the AF evaluation frame setting S110 input from the microcomputer 117, second contrast evaluation data S111, which is a contrast evaluation value for the main subject that is detected by tracking, is generated.

  The second contrast evaluation data S111 generated by the second contrast evaluation calculation unit 116 is read into the microcomputer 117, and focus lens drive instruction data S112 is generated according to a predetermined AF control algorithm. The generated focus lens drive instruction data S112 is sent to the lens drive actuator 118 and is sent to the focus lens 101 as a focus lens drive control signal S113, and the focus lens is moved. Such an operation of the second contrast evaluation calculation unit 116 enables contrast evaluation synchronized with main subject tracking detection, which is a feature of the present invention, and will be described in detail later.

  Note that the synchronization signal S114 is supplied from the video synchronization generation unit 119 to at least the sensor 102 and the first contrast evaluation calculation unit 112, and video processing synchronized with the synchronization signal S114 is performed.

  Next, a method for generating a contrast evaluation value by the first contrast evaluation calculation unit 112 will be described with reference to FIG.

  FIG. 2 is a block diagram showing a schematic configuration of the first contrast evaluation calculation unit 112 in FIG.

  In FIG. 2, the first contrast evaluation calculation unit 112 includes a first contrast evaluation calculation subcircuit 201, a second contrast evaluation calculation subcircuit 202, a third contrast evaluation calculation subcircuit 203, and a fourth contrast evaluation calculation subcircuit 204. . The first contrast evaluation calculation unit 112 includes a fifth contrast evaluation calculation subcircuit 205, a sixth contrast evaluation calculation subcircuit 206, a seventh contrast evaluation calculation subcircuit 207, and an eighth contrast evaluation calculation subcircuit 208. Furthermore, the first contrast evaluation calculation unit 112 includes an evaluation calculation timing generation circuit 209, an evaluation value selection selector 210, and an absolute value calculation circuit 211.

  As described above, the filtered image signal S107 and the synchronization signal S114 are input to the first contrast evaluation calculation unit 112. Since the sensor 102 is also driven by the synchronization signal S114, the filtered image signal S107 is also synchronized with the synchronization signal S114.

  The filtered image signal S107 is converted to an absolute value by the absolute value calculation circuit 211, and an absolute value converted filter image processing signal S218 is generated. Further, as described above, the filtered image signal S107 is a signal with a sign centered on a zero value because bandpass filter processing of a predetermined band is performed and the DC component is dropped to null. The absolute value calculation circuit 211 is for excluding the above-described code information and extracting the energy information. The generated absolute value filtered image processing signal S218 is commonly supplied to the first contrast evaluation calculation subcircuit 201 to the eighth contrast evaluation calculation subcircuit 208.

  The first contrast evaluation calculation subcircuit 201 to the eighth contrast evaluation calculation subcircuit 208 operate in response to the first evaluation calculation timing signal S201 to the eighth evaluation calculation timing signal S208 from the evaluation calculation timing generation circuit 209. In the absolute value filter image processing signal S218, the integration processing is performed only for the image region for which contrast evaluation is desired. The purpose of this integration process is to evaluate the energy change of the image according to the focus state by the focus lens 101 with good S / N in the image region where contrast evaluation is desired, and to reduce the evaluation value to one evaluation value.

  Each integration result by the first contrast evaluation calculation subcircuit 201 to the eighth contrast evaluation calculation subcircuit 208 is generated as a first subevaluation value S209 to an eighth subevaluation value S216. The generated first sub-evaluation value S209 to eighth sub-evaluation value S216 are sequentially selected in accordance with a predetermined sequence by the evaluation value selection selector 210 and output as first contrast evaluation light data S108. This selection control is controlled by a select signal S217 from the evaluation calculation timing generation circuit 209.

  FIG. 3 is a circuit diagram showing a schematic configuration of the first contrast evaluation calculation subcircuit 201 in FIG.

  3, the first contrast evaluation calculation subcircuit 201 includes an integration calculation circuit 301, an integration calculation enable selector 302, an integration calculation reset circuit 303, an integration calculation data buffer 304, an integration data load selector 305, and an integration result output buffer 306. .

  The operation of the first contrast evaluation calculation subcircuit 201 will be described in detail. Note that the second contrast evaluation calculation subcircuit 202 to the eighth contrast evaluation calculation subcircuit 208 perform the same operations as the first contrast evaluation calculation subcircuit 201, and thus the description thereof is omitted.

  The first evaluation calculation timing signal S201 includes three signals: an integration reset signal S301, an integration enable signal S302, and an integration data load signal S303. When the integration reset signal S301 is asserted High, the integration calculation reset circuit 303 becomes active, and the integration data S304 is reset to zero. Further, when the integration enable signal S302 is asserted High, the addition result of the integration data S304 and the absolute value filter image processing signal S218 as input data is updated as the integration data S304. Further, when the integration data load signal S303 is asserted High, the integration data S304 is held in the integration result output buffer 306 and output as the first sub evaluation value S209.

  Next, the operation timing of the first contrast evaluation calculation unit 112 shown in FIG. 2 and the method of generating the first contrast evaluation value data 114 by the first contrast evaluation calculation unit 112 will be described with reference to FIGS. This will be described with reference to FIG.

  FIG. 4A is a diagram illustrating a setting example of the first contrast evaluation calculation frame.

  In FIG. 4A, in a frame image composed of 10 scanning lines Line-1 to Line-10, the vertical pixel positions of Lines 3 to 5 are surrounded by a thick line, that is, in the horizontal direction. A mode that the 1st contrast evaluation calculation frame is set in 8 area | regions is shown. The eight horizontal regions shown in the figure correspond to each of the first contrast evaluation calculation subcircuit 201 to the eighth contrast evaluation calculation subcircuit 208 shown in FIG.

  FIG. 5 is a timing chart for explaining the operation of the first contrast evaluation calculation unit 112.

  In FIG. 5, the synchronization signal S114 includes a V synchronization signal (VD) and an H synchronization signal (HD). As shown in FIG. 4A, since the frame image in the present embodiment is composed of 10 scanning lines, there are 10 HD periods for the VD period.

  The illustrated first vertical evaluation period T501 represents Line-3, the second vertical evaluation period T502 represents Line-4, and the third vertical evaluation period T503 represents Line-5 scanning timing. In each of the first horizontal evaluation period T504, the second horizontal evaluation period T505, and the third horizontal evaluation period T506 corresponding to the first vertical evaluation period T501 to the third vertical evaluation period T503, the first contrast evaluation calculation subcircuit 201 contrasts. This is a period during which evaluation calculation (integration calculation) is performed.

  The integration enable signal S302 is asserted High in each of the first horizontal evaluation period T504, the second horizontal evaluation period T505, and the third horizontal evaluation period T506, and the integration reset signal S301 is asserted High at the start timing of each horizontal scan. To do. As a result, the following arithmetic processing is performed on the integration data S304. That is, the integration data S304 is reset to 0 value at the start timing of the first vertical evaluation period T501 (Line-3), and integration processing is performed in the first horizontal evaluation period T504 (integration result A).

  Then, it is reset to 0 value at the start timing of the second vertical evaluation period T502 (Line-4), and integration processing is performed in the second horizontal evaluation period T505 (integration result B). Further, it is reset to 0 value at the start timing of the third vertical evaluation period T503 (Line-5), and integration processing is performed in the third horizontal evaluation period T506 (integration result C). Also, the integration data A, B, and C are held as the first sub-evaluation value S209 by asserting the integration data load signal S303 to High at the end of each horizontal scan. The above is the first sub-evaluation value S209 obtained by the first contrast evaluation calculation sub-circuit 201.

  Although the second contrast evaluation calculation subcircuit 202 to the eighth contrast evaluation calculation subcircuit 208 are not shown, the horizontal evaluation period is set at a timing adjacent to the first to third horizontal evaluation periods T504 to T506 and while shifting each. Is done. As a result, as shown in FIG. 5, the second sub-evaluation value S210 to the eighth sub-evaluation value S216 are obtained.

  Then, a selection signal S217 is given to the evaluation value selection selector 210 so that the selection is made in the order of the first sub evaluation value S209 to the eighth sub evaluation value S216. As a result, as shown in the first contrast evaluation light data S108 in FIG. 5, in the second vertical evaluation period T502, the integration results of the integration calculations performed in the first vertical evaluation period T501 are A, D, G, J , M, P, S, V in this order. In addition, in the third vertical evaluation period T503, the integration results of the integration calculations performed in the second vertical evaluation period T502 are output in the order of B, E, H, K, N, Q, T, and W. Further, in the period following the third vertical evaluation period T503, the integration results of the integration operations performed in the third vertical evaluation period T503 are in the order of C, F, I, L, O, R, U, and X. Is output.

  With the above operation, as shown in FIG. 4B, the contrast evaluation values obtained for each of the eight grid-like small regions in the horizontal direction and three in the vertical direction are obtained as the first contrast evaluation value data 114. It is done.

  Next, a method in which the second contrast evaluation calculation unit 116 in FIG. 1 generates the second contrast evaluation data S111 using the AF evaluation frame setting S110 and the first contrast evaluation value data 114 will be described with reference to FIGS. This will be described with reference to 6 (b).

  The AF evaluation frame setting S110 is surrounded by, for example, Line-4 (V region 2) to Line-5 (V region 3) and H region 3 to H region 4, as indicated by a thick line in FIG. The area is set (AF evaluation area). That is, the resolution of the AF evaluation frame setting S110 is set in units of small areas, and H, I, K, and L correspond to the first contrast evaluation value data 114 obtained for each small area. Based on this premise, the second contrast evaluation calculation unit 116 reads H, I, K, and L from the first contrast evaluation value data 114, calculates H + I + K + L, and outputs the result as second contrast evaluation data S111. Thereby, contrast evaluation data equal to the integral evaluation value for the subject tracking AF evaluation region as shown in FIG. 6B can be obtained.

  In this manner, a plurality of grid-like small areas are set for the frame image, and the first contrast evaluation value data 114 (first AF evaluation value) is generated for each small area. As a result, the AF evaluation value for the main subject position can be obtained for all regions (position, size) in the frame image without restriction.

  Since the AF evaluation frame setting S110 is an evaluation frame for the main subject detected by the tracking detection unit 107, the second contrast evaluation data S111 is a contrast evaluation value obtained by tracking the main subject.

  Next, the acquisition timing of the second contrast evaluation data S111 will be described with reference to FIG.

  In the present embodiment, the focus state is evaluated from the sensor output signal S101, and feedback control for finally adjusting the focus lens 101 is performed. Therefore, the smaller the latency, the better the AF control response. Is desirable.

  In FIG. 7, the sensor output signal S101 is represented as a first frame (FR1) to a fourth frame (FR4). The tracking detection write data S105 is obtained from the sensor output signal S101 of at least two frames, and is calculated in a period indicated by tracking detection (FR2 / FR1). Similarly, calculation is performed for the periods indicated by tracking detection (FR3 / FR2) and tracking detection (FR4 / FR3).

  During the tracking detection period, the calculation timing is shifted depending on where the main subject is located on the screen. Therefore, as shown in FIG. 7, the tracking detection result is the tracking result (FR2) timing at the latest, as shown in FIG. The result of detection (FR2 / FR1) will be obtained. Similarly, the result of tracking detection (FR3 / FR2) is obtained at the timing of the tracking result (FR3) at the latest. The tracking detection result for the first frame (FR1) is not present because the sensor output signal S101 of the previous frame is not obtained.

  The first contrast evaluation light data S108 is calculated in each period of AF evaluation (FR1), AF evaluation (FR2), AF evaluation (FR3), and AF evaluation (FR4). These calculation periods vary according to the position of the screen area where the first contrast evaluation is performed, but the result of the AF evaluation (FR1) is obtained at the timing of the first contrast evaluation value (FR1) at the latest. Similarly, a result is obtained at the timing of the illustrated first contrast evaluation value (FR2) and first contrast evaluation value (FR3).

  Each acquisition timing of the first contrast evaluation values (FR1 to FR4) in the present embodiment is the acquisition timing of the contrast AF evaluation value according to the conventional technique. On the other hand, the acquisition timing of the second contrast evaluation data S111 is that the second contrast evaluation value (FR2) and the second contrast evaluation value (FR3) are obtained after the calculation delay T701 shown in FIG. This calculation delay T701 is the time required to read H, I, K, and L from the first contrast evaluation value data 114 and calculate H + I + K + L, and it is sufficient to calculate in a very short time. Is possible.

  As described above, according to the first embodiment, a plurality of grid-like small regions are set for the frame image, and an intermediate AF evaluation value is generated for each small region, while the tracking detection is performed. An AF evaluation frame is set for an area corresponding to the position of the main subject. Then, a final AF evaluation value is generated using the set AF evaluation frame and the intermediate AF evaluation value, and AF control is performed by adjusting the position of the focus lens based on the generated final AF evaluation value. . Thereby, it is possible to generate a contrast AF evaluation value in a state where the position of the main subject is tracked, and it is possible to improve the performance of tracking AF on the subject.

[Second Embodiment]
Since the imaging apparatus according to the second embodiment of the present invention is the same as that of the first embodiment, description thereof is omitted. Hereinafter, differences from the first embodiment will be described.

  First, the second contrast evaluation calculation unit 116 according to the second embodiment of the present invention uses the AF evaluation frame setting S110 and the first contrast evaluation value data 114 to generate the second contrast evaluation data S111. FIG. This will be described with reference to (a) and FIG.

  In FIG. 8A, the first contrast evaluation value data 114 is generated for each of 81 rectangular small areas, that is, V areas 1 to 9 and H areas 1 to 9 in total. As the AF evaluation frame setting S110, as shown in FIG. 8A, there are a total of 12 rectangular small areas of V area 3 to 5 and H area 4 to 7. At this time, the second contrast evaluation calculation unit 116 uses the first contrast evaluation value data 114 of each of the twelve rectangular small regions, that is, the values of A to L, to calculate the second contrast evaluation data S111 using the following formula. Calculated according to (1).

  S111 = (A + B + C + D + F + G + I + J + K + L) / 16 + 2 (E + H) / 16 Formula (1)

  That is, the weight 2/16 is applied to the first contrast evaluation value data 114 of the two small rectangular areas V area 4 and H areas 5 and 6 at the center position of the AF evaluation frame setting S110, that is, E and H. Since other areas are peripheral areas, calculation is performed with a weight of 1/16. In this way, the first contrast evaluation value data 114 at a position close to the center of the AF evaluation frame setting S110 is weighted more greatly.

  As described above, according to the second embodiment, weighting is performed so as to emphasize the first AF evaluation value at a position close to the center of the AF evaluation frame setting S110. Thereby, the AF evaluation value for the main subject position can be obtained without lowering the accuracy, and the performance of the tracking AF to the main subject can be improved.

[Third Embodiment]
FIG. 9 is a block diagram illustrating a schematic configuration of an imaging apparatus according to the third embodiment of the present invention. In the imaging apparatus shown in FIG. 9, the same components and signals as those in the first embodiment are assigned the same reference numerals, and detailed descriptions thereof are omitted.

  9, in addition to the imaging apparatus of FIG. 1, the imaging apparatus includes a reliability calculation unit 901, a fifth memory interface 902, a memory for storing reliability data 903, a sixth memory interface 904, and a reliability evaluation unit 905. Is provided.

  The reliability calculation unit 901 digitizes the statistical tendency of the filtered image signal S107 to generate reliability light data S901 that represents the reliability of the first contrast evaluation light data S108. The reliability write data S901 is stored as reliability data 903 in an external memory such as a DRAM via the fifth memory interface 902. The reliability data 903 is read into the reliability evaluation unit 905 as reliability read data S902 via the sixth memory interface 904. Although not shown, the reliability write data S901 is written to an external memory such as a DRAM at substantially the same timing as the first contrast evaluation write data S108. The reliability read data S902 is read from an external memory such as a DRAM at substantially the same timing as the first contrast evaluation read data S109.

  The reliability evaluation unit 905 refers to the reliability write data S901, generates reliability determination data S903, and passes it to the second contrast evaluation calculation unit 916. The second contrast evaluation calculation unit 916 generates the second contrast evaluation data S111 using the reliability determination data S903, the first contrast evaluation lead data S109, and the AF evaluation frame setting S110, and outputs the second contrast evaluation data S111 to the microcomputer 117. As described above, the second contrast evaluation calculation unit 916 is different from the second contrast evaluation calculation unit 116 in FIG. 1 in that the reliability determination data S903 is referred to.

  The difference from the first embodiment in the above operation is that the second contrast evaluation data S111 is generated using the highly reliable first contrast evaluation value data 114, and the focus lens drive instruction data S112 is generated. It becomes.

  FIG. 10 is a block diagram showing a schematic configuration of the reliability calculation unit 901 in FIG. The same reference numerals are assigned to the same components and signals as those of the first contrast evaluation calculation unit 112 in FIG.

  In FIG. 10, the reliability calculation unit 901 includes a first reliability calculation subcircuit 1001, a second reliability calculation subcircuit 1002, a third reliability calculation subcircuit 1003, a fourth reliability calculation subcircuit 1004, and a fifth reliability. A sex operation subcircuit 1005 is provided. Further, the reliability calculation unit 901 includes a sixth reliability calculation subcircuit 1006, a seventh reliability calculation subcircuit 1007, and an eighth reliability calculation subcircuit 1008.

  The difference from the first contrast evaluation calculation unit shown in FIG. 2 is that the absolute value filtered image processing signal S218 is commonly supplied to the first to eighth reliability calculation subcircuits 1001 to 1008. Furthermore, the first to eighth sub reliability S1009 to S1017 are generated from the first to eighth reliability calculation subcircuits 1001 to 1008. The operation of the other components is the same as that described in FIG. 2 except that the reliability calculation unit 901 outputs the reliability write data S901.

  Next, the operation of the first reliability calculation subcircuit 1001 will be described with reference to FIG. Note that the second reliability calculation subcircuit 1002 to the eighth reliability calculation subcircuit 1008 perform the same operations as the first reliability calculation subcircuit 1001, and therefore their description is omitted.

  FIG. 11 is a block diagram showing a schematic configuration of the first reliability calculation subcircuit 1001 in FIG. For the first reliability calculation subcircuit 1001 shown in the figure, the same components and signals as those in the first contrast evaluation value calculation subcircuit in FIG. 3 are assigned the same reference numerals, and the description thereof is omitted.

  The first reliability calculation subcircuit 1001 includes an integration calculation circuit 1101, an integration calculation enable selector 1102, an integration calculation reset circuit 1103, an integration calculation data buffer 1104, an integration data load selector 1105, and an integration result output buffer 1106. Further, S1104 is integration data, which is configured by configuring each component of 301 to 306 and the same function and the same signal as S304 in parallel.

  The first reliability calculation subcircuit 1001 includes a signal level determination circuit 1107, a first integration calculation enable gate 1108, and a second integration calculation enable gate 1109. S1110 is a large level determination flag, S1111 is a small level determination flag, S1112 is a large level pixel count enable signal, and S1113 is a small level pixel count enable signal.

  The operational differences from the configuration example of the evaluation value calculation subcircuit in FIG. 3 are as follows.

  In the signal level determination circuit 1107, when the signal level of the absolute valued filtered image processing signal S218 is equal to or higher than a predetermined threshold (not shown), the large level determination flag S1110 becomes High and the small level determination flag S1111 becomes Low. Like that. When the signal level of the absolute value filtered image processing signal S218 is less than a predetermined threshold (not shown), the large level determination flag S1110 is set to Low and the small level determination flag S1111 is set to High.

  Accordingly, the first integration calculation enable gate 1108 masks the integration enable signal S302 Low when the large level determination flag S1110 is Low. The large level pixel count enable signal S1112 remains Low regardless of the integration enable signal S302. On the other hand, in the second integration calculation enable gate 1109, the integration enable signal S302 is masked low when the small level determination flag S1111 is low. The small level pixel count enable signal S1113 remains Low regardless of the integration enable signal S302.

  As described above, the large level determination flag S1110 and the small level determination flag S1111 are exclusively High and Low. Therefore, in the period when the integration enable signal S302 is High, when the absolute value filter image processing signal S218 is equal to or greater than a predetermined threshold, only the integration calculation enable selector 302 becomes High and the integration calculation circuit 301 performs +1 calculation. The integration result output buffer 306 counts the number of pixels for which the absolute value filtered image processing signal S218 is equal to or greater than a predetermined threshold.

  If the absolute value filter image processing signal S218 is less than the predetermined threshold value, only the integration calculation enable selector 1102 becomes High, and the integration calculation circuit 1101 calculates +1. As a result, the integration result output buffer 1106 counts the number of pixels for which the absolute value filtered image processing signal S218 is less than a predetermined threshold.

  In the first sub-reliability S1009, the count pixel numbers of the integration result output buffer 306 and the integration result output buffer 1106 are bit-coupled and output. Note that the second sub-reliability S1010 to the eighth sub-reliability S1017 perform the same operation as the first sub-reliability S1009.

  FIG. 12B is a diagram showing only the state in the subject tracking AF evaluation area in the first sub-reliability S1009 to the eighth sub-reliability S1016 described above. Note that the area outside the subject tracking AF area is not subject to calculation, and will not be described.

  In FIG. 12B, in the small area indicating 0, the number of pixels in which the absolute value filter image processing signal S218 is less than a predetermined threshold is, for example, more than half of the total number of pixels in the small area. Indicates the area. In addition, the small area indicating 1 indicates an area in which the number of pixels in which the absolute value filter image processing signal S218 is equal to or greater than a predetermined threshold is, for example, more than half of the total number of pixels in the small area. Here, it can be said that the absolute value filtered image processing signal S218 is more reliable because it captures the energy of a predetermined frequency component indicating the degree of focus of the subject better as the signal level increases. Conversely, it can be said that the smaller the signal level, the less the contrast of the subject, the dominant noise energy, and the lower the reliability.

  Accordingly, in FIG. 12B, the first contrast evaluation value data corresponding to the small area indicated as 1, that is, C, D, E, F, G, H, and J shown in FIG. Is done. And as shown in FIG.12 (c), the 2nd contrast evaluation data S111 with higher reliability can be produced | generated by calculating 2nd contrast evaluation data S111 by the following Formula (2).

S111 = (C + D + E + F + G + H + J) / 7 (2)
As described above, according to the third embodiment, a plurality of grid-like small areas are set for a frame image, and an intermediate AF evaluation value is generated for each small area, while the tracking detection is performed. An AF evaluation frame is set for an area corresponding to the position of the main subject. Further, the reliability of the small area is determined from the signal level of the small area set for the frame image. Then, a final AF evaluation value is generated using the set AF evaluation frame, the intermediate AF evaluation value, and the reliability determination result of the small area, and the focus lens is generated based on the generated final AF evaluation value. AF control is performed by adjusting the position of. Thereby, the performance of the tracking AF to the main subject can be improved, and the AF evaluation value for the position of the main subject with higher reliability can be obtained.

[Fourth Embodiment]
FIG. 13 is a block diagram illustrating a schematic configuration of an imaging apparatus according to the fourth embodiment of the present invention. In the imaging apparatus shown in FIG. 13, the same components and signals as those in the first embodiment are assigned the same reference numerals, and detailed descriptions thereof are omitted.

  In FIG. 13, the imaging apparatus includes a zoom lens 1301, an optical aperture 1302, and a blur spread amount estimation unit 1303 in addition to the imaging apparatus of FIG. 1. Details of the focal length information S1301, optical aperture information (F value) S1302, focus lens position information S1303, and estimated blur spread S1304 will be described later.

  FIG. 14 is a diagram illustrating a temporal transition of the focus lens position in the imaging apparatus of FIG.

  In FIG. 14, t1401 is a shutter pressing (S-pressing) timing, t1402 is a lens scanning start timing, t1403 is a lens scanning end timing, and t1404 is a lens stop timing. T1401 is a continuous AF period before S is pushed, P1401 is a lens position at the time of S push, P1402 is a lens scan start position, P1403 is a lens scan end position, and P1404 is a lens stop position.

  T1401 is a continuous AF period before S is pressed. In the continuous AF period T1401, the microcomputer 117 uses the first contrast evaluation lead data S109 or the second contrast evaluation data S111 and the tracking detection lead data S106 to perform the tracking AF operation on the main subject even before S is pressed. When S is pressed at t1401, the lens position of the focus lens 101 is the lens position P1401 when S is pressed. Thereafter, the lens position of the focus lens 101 is moved to the lens scan start position P1402 by the microcomputer 117 in a predetermined sequence at the lens scan start timing t1402. Next, at the lens scan end timing t1403, the lens moves to the lens scan end position P1403. Then, the lens position of the focus lens 101 indicating the maximum change in the second contrast evaluation data S111 obtained between the lens scan start position P1402 and the lens scan end position P1403 is obtained. Then, the focus lens 101 is moved to the lens stop position P1404 at the lens stop timing t1404. This lens stop position P1404 is a focus position for the main subject. The above control is the contrast AF operation at the time of existing still image shooting.

  The focus lens position information S1303 represents the lens position P1401. The focal length information S1301 represents the state of the zoom lens 1301. Optical aperture information (F value) S1302 represents the state of the optical aperture 1302.

  The blur spread amount estimation unit 1303 generates an estimated blur spread amount S1304 from t1402 to t1403 using the focus lens position information S1303, focal length information S1301, and optical aperture information (F value) S1302.

  FIG. 15 is a diagram illustrating a state of blur expansion of the main subject caused by a change in the focus state with respect to the main subject.

  As the blur state of the focus lens 101 is larger, the fine edge of the main subject is not imaged and the entire main subject becomes a blurred image as shown in FIG. The size of the main subject image is large at the time of large blur and becomes smaller as the focus is near.

  While the lens position of the focus lens 101 is moved from the lens scan start position P1402 to the lens scan end position P1403, the main subject image changes from a large blurred state to an in-focus state to a large blurred state shown in FIG. Note that the degree of the large blur depends on the focal length of the zoom lens 1301 and the diaphragm state (F value) of the optical diaphragm 1302 in addition to the lens position of the focus lens 101.

  The estimated blur spread amount S1304 by the blur spread amount estimation unit 1303 is the degree of change in the size of the main subject while moving the position of the focus lens 101 described in FIG. 15 from the lens scan start position P1402 to the lens scan end position P1403. Represents. Therefore, the microcomputer 117 uses the tracking detection read data S106 and the estimated blur spread S1304, and considers the position of the main subject and the size of the main subject (the degree of blur spread) accompanying the movement of the focus lens (lens scan). An evaluation frame setting S110 is generated. As a result, as shown in FIG. 15, it is possible to exclude a small area in which the subject edge has disappeared from the AF evaluation frame, and it is possible to improve the accuracy of the AF evaluation frame.

  As described above, according to the fourth embodiment, it is possible to generate the second AF evaluation value in consideration of the degree of blur spread of the main subject accompanying the movement of the position of the focus lens 101 (lens scan). As a result, the performance of the tracking AF for the main subject during the lens scanning operation can be improved.

  In the first to fourth embodiments, for the sake of simplicity, the number of vertical scanning lines shown in FIG. 4A is 10 lines, but any number of vertical scanning lines may be used. Further, as shown in FIG. 4B, the obtained first contrast evaluation value data 114 is eight in the horizontal direction and three in the vertical direction, but there is no restriction on the number thereof.

  In FIG. 5, the vertical evaluation periods T501, T502, and T503 are set to one line width, but there is no restriction on the line width.

  Furthermore, although the single tracking detection unit 107 has been described with reference to FIG. 1, there are various known techniques for the tracking detection method itself, and even if a plurality of tracking detection units are used, the common effect of the present invention is achieved. There is.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

112 First contrast evaluation calculation unit 117 Microcomputer 201 First contrast evaluation calculation subcircuit 210 Evaluation value selection selector 301 Integration calculation circuit

Claims (5)

Imaging means including a focus lens;
Subject tracking means for generating data indicating the position of the subject from the output signal of the imaging means;
AF evaluation frame setting means for setting an AF evaluation frame from data generated by the subject tracking means;
First generation means for generating a first AF evaluation value from an output signal of the imaging means;
Second generation means for generating a second AF evaluation value using the AF evaluation frame set by the AF evaluation frame setting means and the first AF evaluation value generated by the first generation means;
An image pickup apparatus comprising: a control unit that performs AF control by adjusting a position of the focus lens based on a second AF evaluation value generated by the second generation unit.   The first generation means sets a plurality of grid-like small areas in a frame image obtained from the output signal of the imaging means according to the resolution of the AF evaluation frame setting means, and the first generation means sets the first for each small area. The imaging apparatus according to claim 1, wherein an AF evaluation value is generated.   The second generation unit is close to the center of the AF evaluation frame among the AF evaluation frame set by the AF evaluation frame setting unit and the first AF evaluation value generated by the first generation unit. The imaging apparatus according to claim 2, wherein the second AF evaluation value is generated using the first AF evaluation value of a position. A reliability determination unit that determines the reliability of the first AF evaluation value generated by the first generation unit;
The second generation unit includes a reliability evaluation unit configured to determine reliability among the AF evaluation frame set by the AF evaluation frame setting unit and the first AF evaluation value generated by the first generation unit. The imaging apparatus according to claim 1, wherein the second AF evaluation value is generated using the first AF evaluation value determined to be high. AF operation means for performing contrast AF operation during still image shooting;
Blur spread amount estimating means for generating a blur spread amount indicating a blur spread degree of a subject image using information including the position of the focus lens, the state of the aperture, and the focal length obtained during the operation of the AF operation means; In addition,
The AF evaluation frame setting unit sets an AF evaluation frame according to the blur spread amount generated by the blur spread amount estimation unit from the set AF evaluation frame. The imaging device described.