JP6247513B2 - Imaging apparatus, control method, and program - Google Patents

Description

The present invention relates to an imaging apparatus, a control method, and a program, and more particularly to a technique for generating an image for confirming a focus state of the imaging apparatus.

  With the advancement of auto focus (hereinafter referred to as AF) technology, AF is mainly used for focus detection in an imaging apparatus such as a digital still camera or a digital video camera.

  However, manual focus adjustment (hereinafter referred to as MF) may also be used when it is necessary to focus precisely as in macro shooting, or when shooting intentionally blurred images. Many.

  Some imaging apparatuses capable of MF operation have a function (focus assist function) for displaying an auxiliary image for allowing a photographer to more easily grasp a focused state (focus state).

  The auxiliary image (focus assist image) displayed by the focus assist function includes, for example, an image for highlighting (peaking) a focused contour portion of a captured image, and a partial enlargement for confirming the focus state There is an image.

  Further, a waveform image representing the relationship between the position and level of a contour (edge) component on a video image in a predetermined direction as described in Patent Document 1 is also known.

JP 2010-243923 A JP 2002-196744 A

  Conventionally, as disclosed in Patent Document 1, a focus assist image is generated using image data after development processing. Generally, predetermined gamma processing (tone correction processing) is used for development processing. It is included.

  The gamma processing is originally processing for correcting the gradation characteristics of the input image so that the gradation of the subject is correctly displayed in a display device with non-linear input / output characteristics. However, gamma processing may be performed for other purposes, such as to sufficiently express the color of the subject or to suppress blackout and overexposure on the premise of post-editing.

  Further, as described in Patent Document 2, when simultaneously displaying movie and graphics image data on a display device such as an LCD, different gamma processing is performed for the movie display region and the graphics display region. It is also known to apply.

  The degree of focusing can be determined by the high contrast of the image, and the generation of the peaking and the waveform image of the edge portion includes processing for detecting a high contrast portion. Also, when displaying a partially enlarged image, the user performs an MF operation so that the sharpness of the partially enlarged image is increased.

  Therefore, when the tone correction characteristic (also referred to as gamma curve or gamma characteristic) applied in the gamma process of the development process is a characteristic that lowers the contrast of the image, it affects the effectiveness of the focus assist function. As the most prominent example of such gradation correction characteristics, there is a gradation correction characteristic applied for the purpose of suppressing blackout and overexposure on the premise of post-editing. When gamma processing that reduces image contrast is applied during development processing, if the focus assist function is executed based on the image data after development processing, an appropriate focus assist image cannot be generated, and the effectiveness of the focus assist function may be reduced. It will decline.

The present invention has been made in view of the problems of prior art described above, the gradation corrected even when the image is input, the image pickup apparatus capable of providing an effective focus assist image An object of the present invention is to provide a control method and a program.

In order to achieve the above object, an image processing apparatus of the present invention is characterized by comprising the following arrangement. Specifically, in the imaging device having a focus assist function, one first gradation selected from a plurality of first gradation correction characteristics having different characteristics with respect to image data obtained by imaging a developing unit configured to generate a developed image data by performing a development process including tone correction processing using the correction characteristics, the developing image data, a first gradation correction characteristic gradation used in the developing means A correction unit that applies a gradation correction process using the second gradation correction characteristic that reduces the influence on the image and a generation that generates auxiliary image data used for focus assist from the developed image data corrected by the correction unit and wherein the obtaining Bei and means.

  With such a configuration, according to the present invention, an effective focus assist image can be provided even when a tone-corrected image is input.

1 is a block diagram illustrating a functional configuration example of a camera as an example of an image processing apparatus according to an embodiment of the present invention. Diagram showing an example of gamma processing

(Embodiment 1)
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. In the following, an example in which the present invention is applied to a digital video camera having a focus assist function as an example of an image processing apparatus will be described. However, the present invention can be applied not only to any electronic device having an imaging function, but also to an electronic device that does not have a function relating to shooting and recording. These electronic devices include mobile phones, game machines, tablet terminals, personal computers, etc., but these are merely examples.

(Configuration of image processing apparatus)
FIG. 1 is a block diagram illustrating a functional configuration example of a digital video camera as an example of an image processing apparatus according to an embodiment of the present invention.

  One or more of the functional blocks shown in FIG. 1 may be realized by hardware such as an ASIC or a programmable logic array (PLA), or may be realized by executing software by a programmable processor such as a CPU or MPU. May be. Further, it may be realized by a combination of software and hardware. Therefore, in the following description, even when different functional blocks are described as the operation subject, the same hardware can actually be realized as the subject.

  In FIG. 1, a photographing lens group 123 constitutes an optical system that forms a subject image on the imaging surface of the sensor unit 101, and has an adjustment of incident light amount and focus, and a diaphragm adjustment function.

  The sensor unit 101 has a configuration in which a plurality of pixels having photoelectric conversion elements are two-dimensionally arranged. The sensor unit 101 photoelectrically converts a subject optical image formed by the photographing lens group 123 at each pixel, and further performs analog / digital conversion by an A / D conversion circuit to output a digital signal (image data) in units of pixels. To do.

  The sensor unit 101 may be an imaging device such as a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. The sensor unit 101 includes, for example, a primary color Bayer array color filter, and each pixel is provided with one of R (red), G (green), and B (blue) color filters. The sensor unit 101 outputs image data in the RGB format separated for each of these color components.

  The sensor unit 101 may output pixel data in RGB format by performing pixel addition processing for reducing the output image by obtaining one pixel value from a plurality of pixel values for high-speed output.

  The sensor correction unit 102 performs correction processing of aberration generated by the photographic lens group 123 and processing of interpolating defective pixels of the sensor on the image data output from the sensor unit 101, and outputs RGB format image data.

  The development processing unit 103 receives the RGB image data obtained from the sensor correction unit 102, and performs RGB offset adjustment, gain adjustment, Bayer array interpolation processing, development gamma processing, and the like as input image data. .

  The development gamma processing in the present embodiment is, for example, processing for correcting input image data based on the relationship between input luminance and output luminance (gradation correction characteristics, called gamma curve, gamma characteristics, etc.) shown in FIG. Point to. The gradation correction characteristic (first gradation correction characteristic) used for the development gamma processing generates an image having a gradation characteristic desired by the user in consideration of characteristics of the sensor unit 101, the photographing lens group 123, and the like. In this embodiment, it is called a development gamma characteristic.

  The development processing unit 103 sets development gamma characteristics to be applied when performing development processing according to an instruction from the CPU 121. The CPU 121 may determine the development gamma characteristic according to the characteristics of the sensor unit 101, the photographing lens group 123, and the like that are known in advance and the display device. Further, the CPU 121 may determine the development gamma characteristic based on a user instruction input through the operation unit 122. The development gamma characteristic can be set by notifying the development processing unit 103 of information specifying one of a plurality of development gamma characteristics preset in the development processing unit 103, but other methods can be used. It may be used.

  As described above, in this embodiment, the development gamma characteristic used by the development processing unit 103 can be selected from a plurality of development gamma characteristics, so that image data having gradation characteristics according to the purpose can be generated. These gradation characteristics include, for example, gradation characteristics suitable for display on various display devices such as a TV monitor, and gradation characteristics that enable input of a high dynamic range image assuming post-editing. .

  An example of development gamma characteristics used for high dynamic range images is so-called log gamma. The log gamma is a gradation correction characteristic indicating a characteristic that an output value increases logarithmically with respect to an input value. By using log gamma, it is possible to express gradations in a range larger than the range expressed by the number of bits of image data, and image data suitable for post-editing that is less likely to cause over-exposure or under-exposure. Can be generated.

  The color signal conversion unit 104 converts the RGB format image data from the development processing unit 103 into YCC format image data including a luminance component (Y) and color difference components (Cb, Cr), and outputs the image data.

  The encoding unit 105 performs compression encoding according to the YCC format image data and recording format, and generates a recording image file including additional information such as a header. The encoding unit 105 records the image file on a recording medium 106 such as a semiconductor memory card.

  The display image correction unit 107 corrects the output image data of the development processing unit 103 for display on the display unit 110. This correction may be a gradation correction process according to the input / output characteristics of the display unit 110, for example. For example, when the display unit 110 has an input / output characteristic with a gamma value of 2.2, the input / output characteristic of the display unit 110 is reversed so that the gradation of the output image data of the development processing unit 103 is correctly displayed on the display unit 110. Correction is performed using a gamma characteristic having characteristics. Since the input / output characteristics of the display unit 110 are generally fixed, the gamma characteristics used by the display image correction unit 107 can be set in advance.

  The first selection unit 108 outputs one of the output image data of the development processing unit 103 and the output image data of the display image correction unit 107 in accordance with an instruction from the CPU 121.

  If the development gamma characteristic is the reverse characteristic of the input / output characteristic of the display unit 110, the correction process in the display image correction unit 107 is unnecessary. Therefore, the CPU 121 first determines whether or not the development gamma characteristic set in the development processing unit 103 and the input / output characteristic of the display unit 110 satisfy the relationship of the reverse characteristics. Then, when it is determined that the reverse characteristic relationship is satisfied, the first selection unit 108 is instructed to output the output image data of the development processing unit 103. In this determination, for example, which development gamma characteristic is opposite to the input / output characteristic of the display unit 110 is stored in advance, and the currently set development gamma characteristic matches the stored development gamma characteristic. Can be done based on whether or not.

  The evaluation image correction unit 111 applies gradation correction processing to the image data from the development processing unit 103 in order to generate image data to be evaluated by the auxiliary image generation unit 113.

  The gradation correction process in the evaluation image correction unit 111 is a process for reducing the influence of the gradation property of the image data output from the sensor correction unit 102 on the development gamma process, in other words, before the development gamma process. This is a process for approximating image data. Therefore, the gradation correction characteristic (second gradation correction characteristic) used in the evaluation image correction unit 111 is determined according to the development gamma characteristic in the development processing unit 103.

  For example, when the development gamma characteristic shown in FIG. 2A is used, if the gradation correction characteristic (FIG. 2B) which is the reverse characteristic of the development gamma characteristic is used in the evaluation image correction unit 111, the scale of the image data is obtained. It is possible to cancel the influence of the tonality on the development gamma processing (FIG. 2C).

  Even when a development gamma characteristic that reduces the contrast of an image is used by generating focus assist image data based on image data that has been subjected to tone correction processing by the evaluation image correction unit 111, effective focus assist is used. Function can be provided.

  For ease of explanation and understanding, the case where the gradation correction characteristic used in the evaluation image correction unit 111 is an inverse characteristic of the development gamma characteristic is illustrated, but the gradation correction characteristic used in the evaluation image correction unit 111 is It may not be the reverse characteristic of the development gamma characteristic.

  Further, the characteristic output from the evaluation image correction unit 111, that is, the gradation correction characteristic obtained by the combination of the development gamma characteristic and the gradation correction characteristic used in the evaluation image correction unit 111 may not necessarily be a linear characteristic. . The effect of the present embodiment can be obtained as long as the gradation compression by the development gamma characteristic is reduced.

  The gradation correction characteristics used by the evaluation image correction unit 111 may be set by the user through the operation unit 122 and the CPU 121.

  Similar to the first selection unit 108, the second selection unit 112 outputs one of the output image data of the development processing unit 103 and the output image data of the evaluation image correction unit 111 according to an instruction from the CPU 121.

  For example, when a development gamma characteristic that does not need to be subjected to gradation correction processing by the evaluation image correction unit 111 is used, the CPU 121 uses the development processing unit 103 for the second selection unit 112. May be instructed to output image data from.

  Here, the development gamma characteristic that does not require the gradation correction processing by the evaluation image correction unit 111 is the same development gamma characteristic as the case where the first selection unit 108 outputs the image data from the development processing unit 103. Good. Alternatively, if the currently set development gamma characteristic is a predetermined characteristic that has little influence on the focus assist function, the output image data of the development processing unit 103 is supplied to the auxiliary image generation unit 113 as it is. May be.

  The auxiliary image generation unit 113 generates focus assist image data from the image data input from the second selection unit 112. As described above, the focus assist function includes peaking, partial enlarged display, and edge monitor function.

  Peaking is a function that highlights the edge of a focused part, and the partial enlarged display is a function that enlarges a part of the screen and makes it easy to visually recognize the degree of focus. The edge monitor is a function that displays the in-focus state as a waveform, and displays a larger waveform as the degree of focus is higher.

  The auxiliary image generation unit 113 generates and outputs data of a focus assist image corresponding to the currently set focus assist function. In addition, since a well-known structure can be used about the focus assist function and the data generation of a focus assist image, the description about the detail is abbreviate | omitted.

  The display composition unit 109 is a circuit that generates composite image data obtained by combining the display image data from the first selection unit 108 with the focus assist image data (auxiliary image data) from the auxiliary image generation unit 113 and supplies the composite image data to the display unit 110. It is. The composite image data is displayed on the display unit 110. Note that how the focus assist image data is combined with the display image data is determined in advance for each focus assist function, for example. The focus assist image may be combined so as to be superimposed on the display image, or may be combined so as to be displayed in a separate display area (including a case where the display device is a separate display device). In any case, the focus assist image is displayed simultaneously with the display image (captured image). The display unit 110 may be connected to the outside.

  The processing described above can be performed on each frame image at the time of moving image shooting such as during live view display, but the generation of the focus assist image may be performed every several frames.

  The CPU 121 outputs a control signal to the focus adjustment unit 120 in response to a manual focus operation input from the user through the operation unit 122. The focus adjustment unit 120 drives a focusing lens included in the photographic lens group 123 by, for example, a motor, and changes the focus position of the photographic lens group 123. An image reflecting the change of the in-focus position is captured, and the focus assist image changes according to the captured image. Therefore, the user can obtain a desired in-focus state by performing a manual focus operation while observing a change in the focus assist image.

  Note that when the image processing apparatus according to the embodiment has a configuration that does not include the development processing unit 103 (a form in which the output image data of the development processing unit 103 is input), the information about the development gamma characteristic includes the development processing unit 103. What is necessary is just to acquire from an apparatus (for example, imaging device). Alternatively, the development gamma characteristic information may be acquired from the additional information of the input image data.

  As described above, according to the present embodiment, the gradation correction processing that reduces the influence of the applied gradation correction characteristics on the gradation is applied to the image data to which the gradation correction processing is applied. After further application, a focus assist image is generated. Therefore, for example, an effective focus assist image can be generated even when image data that has been subjected to gradation correction processing that significantly reduces contrast is input.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. The image processing apparatus according to the present embodiment is the same as that of the first embodiment except for the operations of the development processing unit 103 and the evaluation image correction unit 111. Therefore, overlapping description will be omitted, and differences will be described mainly.

  In this embodiment, the development processing unit 103 selectively uses one of a plurality of development gamma characteristics to perform development gamma processing, and the gradation correction characteristic of the evaluation image correction unit 111 is a gradation based on a change in the development gamma characteristic. It differs from the first embodiment in that it is determined so as to reduce the fluctuation of the influence on sex.

  When the development gamma characteristic is switched, the gradation of the image data output from the development processing unit 103 changes. When the gradation correction characteristic applied by the evaluation image correction unit 111 is constant, the focus assist image generated by the auxiliary image generation unit 113 changes even though the actual subject luminance does not change. For this reason, the in-focus state cannot be accurately grasped, and focus adjustment may be hindered.

  The development processing unit 103 performs development gamma processing using one of the plurality of development gamma characteristics prepared in advance, which is set by the CPU 121. The CPU 121 may set or change the development gamma characteristic based on a user instruction regarding the development gamma characteristic input through the operation unit 122.

  The development processing unit 103 applies development gamma processing to the input image data as in the first embodiment, and outputs image data having gradation according to the set development gamma characteristic.

  As described above, the gradation correction processing of the evaluation image correction unit 111 in the present embodiment is processing for reducing fluctuation in gradation of output image data due to a change in the development gamma characteristic. For example, the gradation correction characteristic set in the evaluation image correction unit 111 depends on the development gamma characteristic so that the gradation correction characteristic realized by the combination with the development gamma characteristic being used is substantially constant. Is set.

  Typically, the inverse characteristic of the development gamma characteristic can be set in the evaluation image correction unit 111. By setting the evaluation image correction unit 111 to use a reverse characteristic of the development gamma characteristic, the development gamma characteristic changes the influence of the development gamma process on the gradation of the image data, and hence the influence on the focus assist image. Can be offset.

  The gradation characteristics used in the evaluation image correction unit 111 can be determined by the CPU 121 and set in the evaluation image correction unit 111. Since the CPU 121 also sets the development gamma characteristic as described above, for example, when setting (or changing) the development gamma characteristic in the development processing unit 103, the gradation correction characteristic corresponding to the development gamma characteristic is set in the evaluation image correction unit 111. Can be set. Of course, the setting method and timing of the gradation correction characteristic to the evaluation image correction unit 111 are not limited to this.

  Depending on the development gamma characteristic, which gradation correction characteristic should be set in the evaluation image correction unit 111 can be determined by various methods. For example, when each of the development processing unit 103 and the evaluation image correction unit 111 stores a plurality of applicable gradation correction characteristics, a combination that is reverse characteristics may be stored in advance.

  The gradation correction characteristic is set by specifying the gradation correction characteristic to be applied to the evaluation image correction unit 111 when the CPU 121 notifies the development processing unit 103 of information for specifying the development gamma characteristic. This can be done by notifying information, but other methods may be used.

  For example, the development processing unit 103 may notify the evaluation image correction unit 111 of development gamma characteristic information, and the evaluation image correction unit 111 may change the gradation correction characteristic used according to the correspondence stored in advance. In addition, when the information related to the development gamma characteristic is included in the additional information of the image data or the like, the evaluation image correction unit 111 monitors this information and changes its own gradation correction characteristic when the development gamma characteristic changes. May be.

  As described above, in this embodiment, the evaluation image correction unit 111 applies a gradation correction process that reduces a change in gradation of output image data due to a change in the development gamma characteristic. Therefore, it is possible to reduce the fluctuation of the influence of the change in the development gamma characteristic used in the development processing unit 103 on the gradation property of the focus assist image, and to generate an effective focus assist image.

  For ease of explanation and understanding, the case where the gradation correction characteristic used in the evaluation image correction unit 111 is an inverse characteristic of the development gamma characteristic is illustrated. However, the gradation correction characteristic used in the evaluation image correction unit 111 may not necessarily be the reverse characteristic of the development gamma characteristic as long as the variation in gradation of the output image data due to the change of the development gamma characteristic can be reduced. Further, the gradation correction characteristic obtained by the combination of the development gamma characteristic and the gradation correction characteristic used in the evaluation image correction unit 111 is not necessarily a linear characteristic.

  While the present invention has been described with reference to exemplary embodiments, the scope of the present invention is defined only by the claims and is not limited to the configurations described in these embodiments. Various modifications and changes are possible within the scope of the present invention.

[Other Embodiments]
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed.

Claims (8)

An imaging device having a focus assist function,
Development processing including gradation correction processing using one first gradation correction characteristic selected from a plurality of first gradation correction characteristics having different characteristics is performed on image data obtained by imaging. a developing unit configured to generate a developed image data,
A gradation correction process using a second gradation correction characteristic that reduces the influence of the first gradation correction characteristic used in the developing unit on the gradation is applied to the developed image data. Correction means to
Wherein from the developed image data corrected by the correction means, the image pickup apparatus characterized by obtaining Bei generating means for generating an auxiliary image data used for focus assist, the. In the correction unit, a gradation correction characteristic obtained by a combination of the second gradation correction characteristic and the first gradation correction characteristic used in the developing unit becomes a predetermined gradation correction characteristic. The imaging apparatus according to claim 1, wherein the second gradation correction characteristic is used. The correction unit is configured such that a gradation correction characteristic obtained by a combination of the second gradation correction characteristic and the first gradation correction characteristic used in the developing unit becomes a linear gradation correction characteristic. the imaging apparatus according to claim 1 or 2, characterized by using a Do the second gradation correction characteristic. Said second gradation correction characteristic, an imaging apparatus according to any one of claims 1 to 3, wherein the the inverse characteristic of the first gradation correction characteristic used in the developing means . Wherein the developed image data developing means has a developing imaging apparatus according to any one of claims 1 to 4, characterized in that it comprises a display means for displaying said auxiliary image data. The display means, the image pickup apparatus according to claim 5, wherein the developing unit to the developing image data developing, and displaying the auxiliary image data at the same time. A method for controlling an imaging apparatus having a focus assist function,
Development including a gradation correction process in which the developing unit uses one first gradation correction characteristic selected from a plurality of first gradation correction characteristics having different characteristics with respect to image data obtained by imaging. A development step for performing processing to generate developed image data;
A gradation using a second gradation correction characteristic for the correction means to reduce the influence of the first gradation correction characteristic used in the development step on the gradation property with respect to the developed image data A correction process for applying the correction process;
The method of the imaging apparatus generating means, characterized in that said the developed image data corrected in the correction step, obtain Preparations and generating step, the generating the auxiliary image data used for focus assist. The program for functioning a computer as each means of the imaging device of any one of Claims 1 thru | or 6 .

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