JP5082996B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus that captures a subject image and generates image data, and an image processing program that performs image processing on image data generated by the imaging apparatus.

  Digital images are handled by devices such as digital cameras, displays, and printers. In a digital image, data that is the maximum value of signal encoding has the highest luminance and represents an achromatic color, and this point can be treated as white. For example, when white paper (an object with a reflectance of nearly 100%) appears in a certain area of a digital image, if the data in this area is close to the maximum value, the image appears to have a natural brightness. . However, this is not always the case. For example, in addition to the above-described white paper, there are cases in which an object having brightness characteristics higher than that of white paper, such as a metal-like object or a light source, is reflected in the digital image. In such a case, it is necessary to adjust the signal level of the area corresponding to the white paper to be lower in order to obtain a satisfactory gradation-free gradation of images of these high-brightness objects. There is.

Therefore, in the invention of Patent Document 1, a color gamut based on white of diffuse reflection (complete diffuse reflection) by an object whose reflectance is close to 100%, and a color gamut based on white that can include specular reflection; A total of two color gamuts are defined. By making such a definition, stable brightness can be reproduced in color management.
US 2005/0047648

  However, when the definition according to the invention of Patent Document 1 is applied to image data generated by an electronic camera, the color gamut based on diffusely reflected white cannot be defined in the same manner as the invention of Patent Document 1. In an electronic camera, the average brightness of the entire screen of image data is set to a constant value (for example, 18%) with respect to the maximum value of the final output state by exposure control. This is because it is adjusted. In a certain image, when the reflectance of the subject is distributed uniformly, the diffuse reflection white is adjusted so that the signal level becomes relatively high. However, if a subject with high reflectivity such as a specular reflection object or a light source occupies a lot, and the gradation of these subjects is to be maintained, white of diffuse reflection has a relatively low signal level. Adjusted. Therefore, for example, when outputting image data generated by an electronic camera to a display device, the color gamut based on diffusely reflected white is not unified, and as a result, the brightness is unified by the displayed image data. It is not preferable because it may not be performed.

  An object of the present invention is to reproduce a stable brightness by setting each gradation property in a good state without saturation even when white regions having different reflection characteristics exist in image data.

In one embodiment of the present invention, an imaging device captures a subject image to generate image data, and representative image data of a predetermined region of an image obtained by capturing an image of a predetermined subject by the imaging unit. A data acquisition imaging control unit that performs imaging for data acquisition that stores the imaging conditions as reference image data and reference imaging conditions, and a user operation that issues an instruction to make the imaging for data acquisition executable A data acquisition imaging instruction unit, a general imaging condition acquisition unit that stores the imaging condition as a general imaging condition when normal subject imaging is performed, the reference image data, the reference imaging condition, and the general imaging condition. Based on this, a reference level for calculating a reference level, which is a level of representative image data when it is assumed that an image of the predetermined subject is imaged under the general imaging conditions. Comprising a calculation unit, and the reference level recording unit for recording in addition to the image data generated in the normal object imaging.
In addition, as techniques related to the present invention, there are the following.
An imaging apparatus according to a technique related to the present invention includes an imaging unit that captures a subject image to generate image data, reference image data that is generated by capturing an image of a reference subject by the imaging unit, and the reference image data. An acquisition unit that acquires the imaging conditions at the time of generation and the reflection characteristics of the reference subject, and a reference information generation unit that generates reference information based on the reference image data, the imaging conditions, and the reflection characteristics Prepare.

Another imaging apparatus of technology related to the present invention, generates a reference information acquiring unit that acquires the reference information generated by the imaging device of art related to the present invention described above, the image data by capturing a subject image And an image recording unit that records the generated image data and the reference information in association with each other when the image data is generated by the image capturing unit.

Another imaging apparatus according to a technique related to the present invention includes an imaging unit that captures a subject image to generate image data, reference image data that is generated by capturing an image of a reference subject by the imaging unit, and the reference image An acquisition unit that acquires imaging conditions at the time of generating data and the reflection characteristics of the reference subject, and a reference information generation unit that generates reference information based on the reference image data, the imaging conditions, and the reflection characteristics And a recording unit that records the generated image data and the reference information in association with each other when the image data is generated by the imaging unit.

  Preferably, the image processing apparatus includes a diffused white information generating unit that generates diffused white information related to a diffused white level based on the reference information and the shooting conditions when the image data is generated, and the recording unit includes the image Data and the diffuse white information may be recorded in association with each other.

  Preferably, a reception unit that receives a user operation for setting the reflection characteristic of the reference subject is provided, and the acquisition unit may acquire the reflection characteristic based on the user operation.

  Preferably, the recording unit may record the image data and the diffused white information in association with each other in a RAW format.

  Preferably, the recording unit may record the image data and the diffused white information in association with each other in JPEG format.

An image processing program related to the present invention is an image processing program for performing image processing on the image data recorded by any of the imaging devices related to the present invention described above. A diffused white that generates diffused white information related to a diffused white level based on an acquisition step of acquiring the reference information associated with the image data, and the reference information and a photographing condition when the image data is generated An information generation step, and a gradation conversion processing step for performing gradation conversion processing on the image data using the diffused white information.

  Preferably, an image processing step of performing image processing other than the gradation conversion processing on the image data using the reference information may be provided.

  According to the present invention, even if white regions having different reflection characteristics exist in the image data, it is possible to obtain a stable brightness with each gradation being in a good state without saturation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a single-lens reflex type electronic camera will be described as an example of the camera of the present invention.

  FIG. 1 is a diagram illustrating a configuration of an electronic camera 1 according to the present embodiment. As shown in FIG. 1, an electronic camera 1 includes a photographing lens 2, an aperture 3, a quick return mirror 4, a sub mirror 5, a diffusion screen 6, a condenser lens 7, a pentaprism 8, a beam splitter 9, an eyepiece lens 10, and an imaging lens. 11, a photometric sensor 12, a shutter 13, an image sensor 14, and a focus detection unit 15.

  The photometric sensor 12 is, for example, a five-part photometric sensor. The imaging element 14 is a semiconductor device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). For example, the focus detection unit 15 detects a focus state of the photographic lens 2 by performing phase difference type focus detection. The electronic camera 1 detects the focus state of the photographic lens 2 by performing contrast-type focus detection based on the luminance detected by the photometric sensor 12. It is preferable that whether to perform phase difference type focus detection or contrast type focus detection is set according to a user operation. Further, the focus state of the photographing lens 2 may be detected by combining phase difference type focus detection and contrast type focus detection.

  The electronic camera 1 further includes a monitor 16 such as a liquid crystal monitor that displays an image generated by imaging, and a control unit 17 that controls each unit. The control unit 17 includes a memory (not shown) therein, and records a program for controlling each unit in advance.

  When not photographing, that is, when photographing is not performed, the quick return mirror 4 is disposed at an angle of 45 ° as shown in FIG. The light beam that has passed through the photographing lens 2 and the diaphragm 3 is reflected by the quick return mirror 4 and guided to the eyepiece lens 10 through the diffusion screen 6, the condenser lens 7, the pentaprism 8, and the beam splitter 9. The user confirms the composition by viewing the subject image through the eyepiece 10. That is, the eyepiece 10 functions as a finder. On the other hand, the light beam split upward by the beam splitter 9 is re-imaged on the imaging surface of the photometric sensor 12 via the imaging lens 11. Further, the light beam transmitted through the quick return mirror 4 is guided to the focus detection unit 15 via the sub mirror 5.

  On the other hand, at the time of photographing, the quick return mirror 4 is retracted to the position indicated by the broken line, the shutter 13 is opened, and the light flux from the photographing lens 2 is guided to the image sensor 14.

  FIG. 2 is a functional block diagram of the electronic camera 1 of the present embodiment. 2, the electronic camera 1 includes a timing generator 20, a signal processing unit 21, an A / D conversion unit 22, a buffer memory 23, a bus 24, a card interface 25, and a compression / decompression unit in addition to the configuration of FIG. 26, an image display unit 27, and a communication unit 30. The timing generator 20 supplies output pulses to the image sensor 14. The image data generated by the image sensor 14 is temporarily stored in the buffer memory 23 via the signal processing unit 21 (including a gain adjustment unit corresponding to the imaging sensitivity) and the A / D conversion unit 22. The buffer memory 23 is connected to the bus 24. The bus 24 is connected to the card interface 25, the control unit 17, the compression / decompression unit 26, the image display unit 27, and the communication unit 30 described in FIG. The card interface 25 is connected to a removable memory card 28 and records image data on the memory card 28. The control unit 17 is connected to a switch group 29 (including a release button (not shown)) of the electronic camera 1, a timing generator 20, and a photometric sensor 12. Further, the image display unit 27 displays an image or the like on the monitor 16 provided on the back surface of the electronic camera 1. The communication unit 30 can be connected to an external device of the electronic camera 1 and can exchange various information wirelessly or by wire.

  Next, the operation of the electronic camera 1 having the above-described configuration will be described.

  First, reference imaging will be described using the flowchart shown in FIG. The reference photographing is photographing performed prior to the main photographing, and is photographing for obtaining reference information necessary for quantifying the white level of diffuse reflection. Further, in the reference shooting, unlike normal shooting (hereinafter referred to as “main shooting”), image data generated by shooting is temporarily stored in the buffer memory 23, but a recording medium such as a memory card 28 or the like. Is not recorded. In addition, the shooting target in the reference shooting is an achromatic subject (hereinafter referred to as “reference subject”) such as a gray plate or a standard diffusion plate. An instruction to execute reference shooting is performed by a user operation via the switch group 29, a menu display on the monitor 16, or the like.

  When execution of the reference photographing is instructed, in step S1, the control unit 17 controls the image display unit 27 to display the reference area in the viewfinder. The reference area is an area for which reference white data to be described later is obtained. For example, as illustrated in FIG. 4, the control unit 17 displays a frame F indicating the reference area in the finder. Since the frame F is preferably filled with the reference subject, the control unit 17 may display a message M1 in the finder, for example, as shown in FIG.

  In step S <b> 2, the control unit 17 determines whether the user has instructed to start imaging via the switch group 29. The control unit 17 waits until the start of imaging is instructed, and proceeds to step S3 when determining that the imaging start is instructed.

In step S <b> 3, the control unit 17 determines reference imaging conditions based on the output of the photometric sensor 12. The control unit 17 determines, for example, an ISO sensitivity I ₀ , a shutter speed T ₀ , and an aperture value F ₀ as reference imaging conditions.

In step S4, the control unit 17 stores the reference photographing conditions (ISO sensitivity I ₀ , shutter speed T ₀ , aperture value F ₀ ) determined in step S3 in a memory (not shown) in the control unit 17.

  In step S5, the control unit 17 controls each unit to perform reference shooting, and generates image data. At this time, the control unit 17 evaluates whether the image data generated by the reference photographing is appropriate, and if there is a possibility that the gradation is saturated at the upper and lower ends, the user uses the monitor 16 or the like. It is good also as a structure which alert | reports to.

In step S6, the control unit 17 obtains reference white data from the image data generated in step S5. The reference white data (R ₀ , G ₀ , B ₀ ) is obtained by calculating an average value for each color of RGB in the image data values in the reference area described in step S1 among the image data generated in step S5. Desired.

In step S 7, the control unit 17 stores the reference white data (R ₀ , G ₀ , B ₀ ) obtained in step S 6 in a memory (not shown) in the control unit 17.

  In step S <b> 8, the control unit 17 controls the image display unit 27 to display a reflection characteristic setting screen on the monitor 16. For example, the control unit 17 displays a reflection characteristic setting screen shown in FIG. In the example of FIG. 5, “18% gray plate” and “standard diffusion plate” are cited as settable reference subjects. “Reflectance numerical value designation” is a setting item for numerically designating the reflectance of the reference subject. The user sets the reflection characteristic of the reference subject by selecting an item while viewing the monitor 16.

  In step S <b> 9, the control unit 17 determines whether or not the reflection characteristic is set by the user via the switch group 29. The control unit 17 waits until the reflection characteristic is set, and proceeds to step S10 when determining that the reflection characteristic is set.

  In step S10, the control unit 17 stores, for example, the reflectance n of the reference subject in a memory (not shown) in the control unit 17 based on the reflection characteristics set in step S9 (for example, reflection of 18% gray plate). The rate n = 0.18), and the reference shooting is finished.

At the time when the reference photographing is finished, the reference photographing conditions (ISO sensitivity I ₀ , shutter speed T ₀ , aperture value F ₀ ), reference white data (R ₀ , G ₀ , B ₀ ), and the reflection of the reference subject The rate n is stored in a memory (not shown) in the control unit 17.

  In the example of the flowchart in FIG. 3, the example in which the reflection characteristic is set after performing the reference imaging in step S <b> 5 has been described. However, the reflection characteristic may be set before performing the reference imaging.

  In addition, when the electronic camera 1 includes a flash device, the reflection characteristics can be automatically set. For example, the reference photographing is performed twice with and without the flash device, and difference data between the image data at the time of light emission and the image data at the time of non-light emission is calculated. The reflectance n can be obtained by calculating the ratio of the difference data to the difference data when the reference subject is a completely diffuse reflection object. In this case, difference data in the case where the reference subject is a completely diffuse reflection object may be obtained in advance through experiments or the like and recorded in the electronic camera 1.

  It is preferable that such automatic setting of the reflection characteristic can be turned ON / OFF by the user's specification. Alternatively, the reflection characteristic may be automatically set using a flash device when the reflection characteristic is not set before or after the reference photographing or when an error occurs in the setting.

  Next, the actual photographing will be described using the flowchart shown in FIG. It is assumed that the above-described reference photographing has already been performed at the start of the main photographing. Further, it is assumed that the ambient light at the time of actual photographing has not changed from the ambient light at the time of reference photographing.

  In step S21, when an instruction to start imaging is given by the user via the switch group 29, the control unit 17 proceeds to step S22.

  In step S <b> 22, the control unit 17 determines the main photographing condition based on the output of the photometric sensor 12. The control unit 17 determines, for example, ISO sensitivity I, shutter speed T, and aperture value F as main imaging conditions.

  In step S23, the control unit 17 stores the main photographing conditions (ISO sensitivity I, shutter speed T, aperture value F) determined in step S22 in a memory (not shown) in the control unit 17.

  In step S <b> 24, the control unit 17 controls each unit to perform main photographing and generates image data.

In step S25, the control unit 17 obtains diffuse white data (W _R , W _G , W _B ) from the image data generated in step S24. The diffused white data (W _R , W _G , W _B ) is obtained by the following equations 1 to 3.

W _R = R ₀ · (I / I ₀ ) ^-1 · (T / T ₀ ) · (F ² / F ₀ ² ) · (1 / n) (Formula 1)
W _G = G ₀ · (I / I ₀ ) ^-1 · (T / T ₀ ) · (F ² / F ₀ ² ) · (1 / n) (Formula 2)
W _B = B ₀ · (I / I ₀ ) ^-1 · (T / T ₀ ) · (F ² / F ₀ ² ) · (1 / n) (Formula 3)
In step S26, the control unit 17 performs gradation conversion processing on the image data generated in step S24, using the diffused white data (W _R , W _G , W _B ) obtained in step S25. If the image data generated in step S24 is RAW data (R _raw , G _raw , B _raw ), the control unit 17 first uses the following equations 4 to 6 to generate RAW data (R _raw , G _raw , B _raw ).

R ₁ = (1 / W _G ) · (W _G / W _R ) · R _raw = (1 / W _R ) · R _raw (Formula 4)
_{G 1 = (1 / W G} ) · (W G / W G) · G raw = (1 / W G) · G raw ... ( Equation 5)
B ₁ = (1 / W _G ) · (W _G / W _B ) · B _raw = (1 / W _B ) · B _raw (Formula 6)
Next, the control unit 17 performs input / output-related gradation conversion processing on the standardized RAW data (R ₁ , G ₁ , B ₁ ) using Expression 7 and Expression 8 below.

y = f (x) (where x ≦ 1) (Expression 7)
y = f ′ (1) · (x−1) + f (1) (where x> 1) (Equation 8)
In Expressions 7 and 8, x indicates an input and y indicates an output. FIG. 7 shows a graph (tone conversion curve) showing the relationship between x and y.

By the gradation conversion processing using Expression 7 and Expression 8, the diffuse white data (W _R , W _G , W _B ) can always be reproduced with the same brightness. For example, assuming that the diffused white data W _R = w in FIG. 7, when the diffused white data W _R = w / 2, the gradation conversion curve shown in FIG. 8 is applied.

  In step S27, the control unit 17 controls the compression / decompression unit 26 to perform compression processing on the image data that has undergone the gradation conversion processing in step S26.

  In step S28, the control unit 17 records the image data subjected to the compression process in step S27 on the memory card 28 via the card interface 25, and ends the main photographing.

<Modification>
In the above embodiment, the case where the reference photographing and the main photographing are performed with the same electronic camera has been described as an example. However, the reference photographing and the main photographing may be performed with different devices. Such a configuration is useful, for example, when shooting with a plurality of electronic cameras having the same characteristics under the same ambient light conditions, such as news shooting. In this case, reference photographing may be performed with one digital camera, and the reference information may be transmitted to another electronic camera having the same characteristics by wireless communication or the like. The electronic camera that has received the transmission can perform the above-described main photographing using the reference information. The reference information includes reference photographing conditions (ISO sensitivity I ₀ , shutter speed T ₀ , aperture value F ₀ ), reference white data (R ₀ , G ₀ , B ₀ ), and reference object reflectance n. In addition, image data itself generated by reference photographing (including the address of the reference area), information indicating the type of the reference subject, and the like can be used. Further, reference data may be the image data itself at the time of light emission and non-light emission. Furthermore, the reference information does not necessarily have to be generated by an electronic camera, and may be generated by a device such as an exposure meter. Moreover, the structure which acquires a part of reference information based on user operation may be sufficient.

Further, the processing described in the present embodiment may be realized by software using a computer and an image processing program. In this case, what is necessary is just to make it the structure which implement | achieves part or all of the process after step S25 demonstrated with the flowchart of FIG. 6 with a computer. In order to be realized by a computer, together with the image data generated by the main photographing, the reference information described above, the main photographing conditions (ISO sensitivity I, shutter speed T, aperture value F), diffuse white data (W _R , W _G , W _B ) and the like may be supplied to the computer. Such information can be supplied using the EXIF information of the image data. When compression processing such as JPEG compression is performed on image data generated by actual shooting, the same compression processing is also applied to the diffused white data (W _R , W _G , W _B ) and the reference information and It is preferable to do this.

  Moreover, it is good also as a structure which performs simultaneously the process demonstrated in the said embodiment combining preset white balance. Preset white balance performs the same processing as the reference photographing described above to obtain parameters for white balance. Therefore, a configuration may be used in which the white balance parameter is obtained using the result of the reference photographing described above.

  As described above, according to the present embodiment, the reference image data generated by capturing the image of the reference subject, the shooting conditions when the reference image data is generated, and the reflection characteristics of the reference subject are acquired. Reference information is generated based on the acquired information. Therefore, by performing gradation conversion processing using this reference information, even if there is a white region with different reflection characteristics in the image data, each gradation is brought into a good state without saturation and stable. Brightness can be reproduced.

  In the present embodiment, the example in which the gradation conversion process is performed using the reference information has been described. However, the reference information may be used for processes other than the gradation conversion process. For example, reference information may be used for gain adjustment or the like.

  In the present embodiment, an example in which the technology of the present invention is realized in the electronic camera 1 has been described. However, the present invention is not limited to this. For example, the present invention can be similarly applied to a compact type electronic camera, a movie camera for taking a moving image, and the like.

  In addition, the present invention can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, the above-described embodiments are merely examples in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the scope of claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

It is a figure which shows the structure of the electronic camera 1 of this embodiment. It is a functional block diagram of electronic camera 1 of this embodiment. It is a flowchart explaining reference imaging | photography. It is a figure explaining a reference field. It is a figure explaining a reflection characteristic setting screen. It is a flowchart explaining this imaging | photography. A gradation conversion curve is shown. A gradation conversion curve is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electronic camera, 2 ... Shooting lens, 14 ... Imaging element, 16 ... Monitor, 17 ... Control part, 23 ... Buffer memory, 27 ... Image display part, 29 ... Switch group, 30 ... Communication part

Claims (5)

An imaging unit that captures a subject image and generates image data;
Data acquisition imaging control for performing imaging for data acquisition that stores representative image data of a predetermined region of an image obtained by imaging an image of a predetermined subject by the imaging unit and the imaging conditions as reference image data and reference imaging conditions And
A data acquisition imaging instruction unit for accepting a user operation to give an instruction to make the data acquisition imaging executable;
A general imaging condition acquisition unit that stores the imaging condition as a general imaging condition when normal subject imaging is performed;
Based on the reference image data, the reference imaging condition, and the general imaging condition, a reference level that is a level of representative image data when the image of the predetermined subject is assumed to be imaged under the general imaging condition is calculated. A reference level calculator,
An imaging apparatus comprising: a recording unit that records the reference level added to the image data generated by the normal subject imaging . The imaging device according to claim 1,
The recording unit records image data generated by the normal subject imaging by applying image processing such that the reference level becomes a predetermined level.
An imaging apparatus characterized by that . In the imaging device according to claim 1 or 2,
The reference level is diffuse white information related to a diffuse white level.
An imaging apparatus characterized by that . The imaging device according to claim 3 .
The image recording apparatus, wherein the recording unit adds and records the diffused white information in RAW format to image data generated by the normal subject imaging . The imaging device according to claim 3 .
The image recording apparatus, wherein the recording unit adds and records the diffuse white information in the JPEG format to image data generated by the normal subject imaging .

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