JPH10210353A - Digital camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent wrong photographing of a white board in which character information is unclear due to the regular reflection of an illumination light. SOLUTION: The photographed image of a character information written on a white board and fetched by a CCD 20 is inputted in a histogram production part 323c via an A/D converter 321. The part 323c produces a histogram for every small image, consisting of blocks which are divided from the photographed image. A regular reflection detection part 323g decides whether any one of small image includes an image of illumination light reflected regularly on the white board, based on the shape of every histogram. If the regular reflection light is detected in a small image, a warning is produced via a buzzer, an LED display, etc. The regular reflected light, included in the photographed image is detected for every small image, and the regular reflection warning is produced according to this detection result Thus, it is possible to prevent erroneous photographing of an image having ambiguous character information, due to the regular reflection light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera that photoelectrically converts a still object light image into an electric signal and captures the electric signal.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a digital copying machine, in order to enhance the clarity of information such as characters and figures copied on a recording sheet, an image captured by photoelectric conversion into an electric signal is taken. Image processing (gamma correction processing) is performed using a γ characteristic having a relatively large γ value (γ characteristic having a characteristic close to the binarization processing). In this gamma correction processing, generally, in order to reduce the influence of uneven illuminance, as shown in FIG. 36, the captured image G is divided into a plurality of rectangular blocks B (1), B (2) in the sub-scanning direction. ,... B (n), and based on a histogram indicating the level distribution of the pixel data included in each block B (r), γ characteristics γ (1), γ (2),. n) and set each block B (r)
The pixel data in (r = 1, 2,... N) is subjected to gamma correction using the γ characteristic γ (r) for the block.

[0003] By this gamma correction, a white background portion above a predetermined level is uniformly converted to a constant white color, and a character portion (black character portion) below a predetermined level is uniformly converted to a constant black color. An image quality similar to the processing can be obtained.

Japanese Patent Laid-Open Publication No. Hei 6-113139 discloses that a captured image is divided into a plurality of partial image blocks, and a selected partial image block (partial image block of interest) and a plurality of adjacent partial image blocks. For each partial image block, a histogram of the level distribution of the pixel data included in the block is created for each block, and a threshold value of the partial image block of interest is set by a neural network using the data of the histogram.
An image binarization device that performs a binarization process on pixel data in a partial image block of interest using this threshold value is shown.

Further, in an image forming apparatus such as a digital copying machine, when illumination light is specularly reflected by a document, the density of characters and the like written on the document is significantly reduced by the specular reflection light, and the document image is accurately formed. Can not be imported to
Heretofore, in order to prevent such a problem, there has been known a technique for detecting illumination light that is specularly reflected from a document.

[0006] This detection technique uses C for each sensor line.
Create a histogram of the level distribution of pixel signals captured by an image sensor such as a CD (Charge Coupled Device),
The presence or absence of specularly reflected light is determined from the shape of the histogram. More specifically, when specular reflection light is included, a pixel signal at a saturated level is output from a pixel that has received specular reflection light. The presence or absence of specularly reflected light is determined by determining whether or not the light is reflected.

[0007]

By the way, a digital camera can freely control the image quality of an image photographed by image processing, so that the image quality of a photographed image can be appropriately adjusted according to the purpose of photographing and the type of subject. By doing so, there is an advantage that an image with more favorable image quality can be captured as compared with a camera that shoots on a normal silver halide film. For this reason, it is used not only for ordinary photography but also as a device for copying information such as characters and figures written on a whiteboard in a conference hall.

When photographing a whiteboard on which characters and figures are written by a digital camera, the main purpose of the photographing is to record information such as characters and figures on the whiteboard. On the other hand, similarly to the digital copying machine, it is desirable to perform gamma correction so that a white background portion (whiteboard portion) is skipped white to enhance the clarity of an information portion (character or graphic portion).

In this case, since the variation in character density and uneven illuminance on the whiteboard are large, the captured image is two-dimensionally divided into a plurality of blocks, and gamma correction is performed for each block to correct illuminance unevenness (shading). Correction).

That is, assuming that the whiteboard is illuminated by the ceiling light in the room and the sunlight outside the window, the illuminance unevenness occurs due to the unevenness of the illumination light, and the angle .omega. The image of the off-axis object point incident at is cos ⁴
Due to the synergistic effect of the incident light amount distribution according to the so-called cosine fourth law, which becomes darker in proportion to ω, and the illuminance non-uniformity, the output distribution of an imaging device such as a CCD fluctuates greatly in the two-dimensional direction within the imaging surface.

For this reason, it is desirable to divide the captured image two-dimensionally into a plurality of blocks, and perform gamma correction in accordance with the illuminance in each block to perform illuminance unevenness correction. More preferably, when the γ characteristic set for each block greatly changes between adjacent blocks, a block size is set to avoid generation of a false line at a block boundary due to a sudden change in the γ characteristic. Is set as small as possible to set an appropriate γ characteristic for each block.

In this case, in a photographing position where illumination light such as a ceiling light or sunlight is regularly reflected by the whiteboard, characters and the like on the whiteboard fly white due to the regularly reflected illumination light. A low-value image will be captured. In particular, if the above-described illuminance unevenness correction is performed in image processing, an accurate histogram cannot be created in a block including specularly reflected light, and not only can effective illuminance unevenness correction not be performed, but also specularly reflected light around the block. Blocks that do not include the reflected light also have an adverse effect, which causes a problem that image quality and information value are significantly reduced.

In a digital copying machine, an original is illuminated by an artificial light source under predetermined conditions, so that regular reflection light can be sufficiently detected by a line-by-line detection process of a sensor. The illumination conditions of the illumination light are not constant, and particularly, external light such as sunlight enters the whiteboard in a spot shape and is specularly reflected. It is difficult to reliably detect the spot-like regular reflected light if the detection processing is performed in step (1), and sufficient detection accuracy cannot be obtained.

On the other hand, the binarization processing technique described in Japanese Patent Application Laid-Open No. Hei 6-113139 mainly relates to binarization processing in a copying apparatus or a facsimile apparatus. There is no specific specular reflection problem or description suggesting it.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of a situation in which information such as characters written on a board is photographed under a photographing condition in which illumination light is regularly reflected by a whiteboard. Is provided with high accuracy, and a digital camera capable of reliably preventing a shooting error of shooting a low-quality video.

[0016]

According to the present invention, there is provided a digital camera for photoelectrically converting a subject light image into a pixel signal by an image pickup means comprising a plurality of photoelectric conversion elements, capturing the image, and recording the image formed from the pixel signal on a recording medium. An image dividing unit that divides an image captured by the imaging unit into a plurality of small images; a histogram creating unit that creates a histogram of a level distribution of pixel signals constituting each small image for each small image; For each, using the created histogram, determining means for determining whether or not the small image includes illumination light regularly reflected by the main subject, and determining whether the illumination light regularly reflected by any of the small images is included. And a specific processing means for performing a specific process when included.

Further, according to the present invention, in the above digital camera, a warning means is provided, and the specific processing means warns the main subject that the illumination light is regularly reflected by the warning means. Item 2).

According to the above arrangement, the image captured by the imaging means is divided into a plurality of small images, and a histogram of the level distribution of the pixel signals constituting each small image is created for each small image. In addition, for each small image, it is determined whether or not the small image includes illumination light that has been regularly reflected by the main subject, using the created histogram, and any one of the small images includes the regular reflection light. Then, a specific process such as warning that the image is a photographed image including specularly reflected light or performing gamma correction with a γ characteristic different from normal photographing is performed.

Further, according to the present invention, in the digital camera, the specific processing means prohibits the recording of the captured image in the recording means (claim 3).

According to the above arrangement, if any of the small images contains the illumination light that is specularly reflected by the main subject, the recording of the captured image on the recording means is prohibited. That is, photography of the subject including the specularly reflected light is prohibited.

As a result, the photographer erroneously shoots a low-quality subject image (for example, an image in which characters or the like written on a white board are obscure due to specular reflection light) which is partially obscure due to specular reflection light. Can be reliably prevented.

[0022]

FIG. 1 is a perspective view showing the appearance of a digital camera according to the present invention. FIG. 2 is a rear view of the digital camera.

The camera 1 shown in FIG.
A D area sensor is provided, and image data captured by the CCD area sensor is recorded on a PCMCIA-compliant hard disk card (not shown). In addition,
In this embodiment, a case where an area sensor is used as an image sensor will be described. However, a configuration may be adopted in which a subject optical image is scanned by a line sensor to capture image data.

The camera 1 applies illumination light (a ceiling light, a window, etc.) to a whiteboard to a photographed image of information such as characters and figures written on the whiteboard (hereinafter, such binary information is referred to as character information). It is provided with a correction function for illuminance unevenness caused by unevenness of outside sunlight or the like and variation in sensitivity of the CCD area sensor.

That is, as shown in FIG. 4, for example, assuming that the whiteboard 23 is illuminated by the ceiling light in the room and the sunlight outside the window, illuminance unevenness occurs due to uneven illumination light, and The image of the off-axis object point incident on the entrance pupil of the photographing lens at an angle ω darkens in proportion to cos ⁴ ω. As shown in FIGS. 5A and 5B, the output distribution of the CCD area sensor greatly varies two-dimensionally within the imaging plane. In the camera 1, when shooting in a character image mode described later, an appropriate γ characteristic is set for each pixel data or a plurality of pixel data units,
By performing gamma correction for each pixel data or each pixel data unit using the γ characteristic, the output fluctuation of the CCD area sensor which occurs two-dimensionally is reduced as much as possible.

In FIG. 5, the solid line indicates the case where nothing is written on the white board 23,
3 shows an output distribution of a white background portion, and a dotted line shows an output distribution of a character portion when a character is written on the whiteboard 23.

Here, the illuminance unevenness correction will be briefly described. The image of the text information is mainly used for recording information, and it is required that the image quality is higher than the descriptiveness. It is desirable to clarify the information and reduce unevenness of the illuminance to make it easier to see as a whole.

In this embodiment, as shown in FIG. 6, a captured image G is divided into a plurality of square blocks B (I) (I = 1, 2,... 18 in FIG. The white background level W calculated using the histogram of the level distribution of the pixel data included in B (I), as shown in FIG.
The characteristic is set as a γ characteristic γ (I) with respect to the center position O (I) of the block (I), and the center position O (I) of each block B (I) is further determined by using the set γ characteristic γ (I). ), The γ characteristics γ (P) of the pixel positions P other than those are interpolated, and the gamma correction of the pixel data of the corresponding pixel positions O (I), P is performed using these γ characteristics γ (I), γ (P). By doing so, clarification of character information and correction of illuminance unevenness are performed.

FIG. 7 shows a case where the pixel data is A / D converted to 8-bit data, and the level value "255" of the input / output level indicates the maximum value. Further, in the γ characteristic shown in the figure, since all the pixel data at the input level W or higher are converted to pixel data saturated to the maximum level, the captured image has a uniform white background portion including the pixel data at the input level W or higher. The image is corrected to an image quality of white lightness. Thereby, the contrast of the character information portion with respect to the white background portion is enhanced, and the character information is clarified.

If necessary, gamma correction is performed on the image after the illuminance non-uniformity correction using the gamma characteristic as shown in FIG. That is, the image after the illuminance unevenness correction is corrected to the image quality in which the black background portion formed of the pixel data of the input level B or less becomes black with the minimum brightness uniformly.
The character portion is highlighted in black in accordance with the density, line thickness, and line density of the characters and figures written in No. 3 so that the character information can be clarified properly. The details of the gamma correction process in the illuminance unevenness correction will be described later.

Referring back to FIG. 1, the camera 1 has a photographing lens 2 composed of a zoom lens disposed substantially at the center of the front surface, and a light projecting window 4 and a light receiving window for measuring a subject distance by an active distance measuring method. 5 is provided, and a photometric window 3 for measuring the brightness of the subject is provided between the two windows. A finder objective window 6 is provided on the left side of the light projecting window 4, and a flash 7 is provided on the right side of the light receiving window 5.

As shown in FIG. 3, a horizontally long rectangular CCD area sensor 21 (hereinafter, abbreviated as CCD 21) is provided at an image forming position of the taking lens 2 in the camera body.
An aperture 22 is provided between the CCD 21 and the taking lens 2.

The light projecting window 4 is a window for irradiating the subject with infrared light, and the light receiving window 5 is a window for receiving the reflected light of the infrared light from the subject. In the present embodiment, the active distance measuring method is adopted as the distance measuring method, but a passive distance measuring method may be used.

On the side of the camera 1, there is provided a card insertion slot 8 into which the hard disk card 13 is inserted and removed. Above the card insertion slot 8, a card ejection button 9 for ejecting the hard disk card 13 is provided. . When printing out the photographing result, the user can press the card ejection button 9 to remove the hard disk card 13 from the camera 1 and mount the hard disk card 13 in a printer to which the hard disk card can be mounted to print out.

The camera 1 is provided with an interface of a SCSI cable, and the camera 1 and the printer are connected to the SCSI cable.
The image data may be directly transferred from the camera 1 to the printer by connecting with a cable, and the photographed image may be printed out.

In this embodiment, a hard disk card conforming to PCMCIA is used as a recording medium for image data. However, if a photographing result can be stored as image data, a memory card or a mini disk (MD)
And other recording media.

On the upper surface of the camera 1, a shutter button 10 is provided at the left end, and a zoom switch 11 and a photographing / playback switch 12 are provided at the right end. The shutter button 10 is an operation button that turns on an S1 switch for instructing shooting preparation such as focal length adjustment and exposure control value setting when pressed halfway, and turns on an S2 switch for instructing release when fully pressed. The zoom switch 11 can slide left and right
It consists of a contact switch, and the zoom switch 11 is set to T (TEL
Slide to the E) side to the telephoto side and W (WID
By sliding to the E) side, the zoom ratio of the taking lens 2 can be continuously changed to the wide angle side.

The photographing / reproducing switch 12 is a switch for switching between a photographing mode and a reproducing mode. The photographing / playback switch 12 is composed of a two-contact changeover switch slidable left and right. When the photographing / playback switch 12 is set to the photographing (REC) side, photographing of a subject (recording of a photographed image on the hard disk card 13) And playback (PL
AY), the hard disk card 13
LCD display section 19 of the captured image recorded in the camera (see FIG. 2)
Monitor display on the computer.

On the back of the camera 1, as shown in FIG.
A power switch main switch 14 and a finder eyepiece window 15 are provided at the upper left end and substantially at the center, respectively, and a buzzer 16 is provided at the upper right corner. The buzzer 16 warns the photographer that when illuminating light is specularly reflected by the whiteboard 23 and character information becomes unclear when character information on the whiteboard 23 is photographed. Hereinafter, this warning is referred to as “specular reflection warning”.

An illumination unevenness correction switch 17 and a black density adjustment switch 18 are provided below the main switch 14, and a regular reflection warning switch 20 is provided on the right side of the black density adjustment switch 18. Further, an LCD display unit 19 is provided at the lower right corner on the back surface of the camera 1.

The illuminance unevenness correction switch 17 is a switch for instructing the illuminance unevenness correction described above. Illumination unevenness correction switch 17 is ON / OF in which the operation button slides left and right
It is composed of an F switch. Illuminance unevenness correction switch 1
When the illuminance non-uniformity correction is instructed by the block 7, the captured image is divided into a plurality of blocks (small images), and the blocks are divided into blocks according to the γ characteristics set using the pixel data included in the blocks as shown in FIG. Gamma correction is performed. On the other hand, when the illuminance non-uniformity correction switch 17 is turned off, a γ characteristic suitable for normal photographing that has been set in advance (image quality with high descriptiveness capable of reproducing the gradation of the subject as faithfully as possible) is obtained. Gamma correction processing of the captured image is performed using the obtained γ characteristic).

The illuminance non-uniformity correction is intended to improve image quality deterioration due to illuminance non-uniformity when photographing character information written on a whiteboard, and is mainly applied when such character information is photographed. Therefore, if an image obtained by capturing information such as characters and figures is referred to as a “character image” and an image obtained by capturing a landscape or a person is referred to as a “natural image” and the content of the captured image is divided into two types, the illuminance unevenness correction switch 17 is used for The switch switches image processing (especially gamma correction processing) of an image between a character image mode and a natural image mode.

When photographing a character image, the photographer sets the illuminance unevenness correction switch 17 to "ON" so that an image quality suitable for the character image (white information is appropriately emphasized by skipping white portions white). Illuminance unevenness correction switch 1 when shooting a natural image.
By setting “7” to “OFF”, a captured image having an image quality suitable for a natural image (image quality with high descriptiveness) can be obtained.

The black density adjustment switch 18 is a switch for adjusting the black saturation level B (see FIG. 8) of the γ characteristic in the gamma correction of black emphasis on the image after the illuminance unevenness correction. The black density adjusting switch 18 is constituted by a three-contact switch whose operation button slides left and right. The black density adjustment switch 18 functions only when the illuminance unevenness correction switch 17 is set to “ON” (when the character image mode is set). In the character image mode, when the black density adjustment switch 18 is set to the OFF state, as shown in FIG. 9, the black saturation level of the γ characteristic is set to a predetermined level B0, and the black density adjustment switch When 18 is set to “dark”, the black saturation level of the γ characteristic is switched to a predetermined level B1 (> B0) larger than the predetermined level B0, and when set to “light”, black saturation of the γ characteristic is set. The level is switched and set to a predetermined level B2 (<B0) smaller than the predetermined level B0.

In the image processing in the character image mode, the white saturation level of the γ characteristic is automatically adjusted so as to remove the background portion white, but the density of the character portion is further changed by changing the black saturation level by the black density adjustment switch 18. Can be changed to adjust the contrast with the base (white background).

For example, comparing the characters written on the whiteboard with the characters written on the document, the characters on the whiteboard are generally thicker and larger than the characters on the document. When the same gamma correction is performed as in the case, the contrast of the character with respect to the background is reduced as compared with the case of the whiteboard. Therefore, when photographing an original, the black density adjustment switch 1
By setting “8” to “dark”, the black of the character portion can be enhanced, and the contrast of the character portion with respect to the background can be suitably adjusted.

In the present embodiment, the black saturation level is switched and set in two stages. However, a multi-stage switching system may be used, or the black saturation level may be switched continuously.

The LCD display section 19 displays a captured image on a monitor. When the photographing / reproduction switch 12 is set to the reproduction side, a captured image of a frame designated by a selection switch (not shown) is read from the hard disk card 13 and reproduced and displayed on the LCD display unit 19.

The regular reflection warning switch 20 is a switch for giving an instruction to issue the above-described regular reflection warning. The regular reflection warning switch 20 is ON when the operation button slides left and right.
/ OFF switch. When "warning" is instructed by the regular reflection warning switch 20, the captured image is divided into a plurality of blocks (small images), and each block is forwarded using a histogram of the level distribution of the pixel data included in the block. The presence or absence of reflected light is determined, and if specularly reflected light is detected in any of the blocks, the buzzer 16
Beep sounds. Also, as shown in FIG.
The LED display 24 for regular reflection warning provided in the viewfinder field frame 42 emits light to warn that the image quality of a captured image may be degraded by the regular reflection light. On the other hand, when the regular reflection warning switch 20 is "OFF",
The detection of the regular reflection light and the regular reflection warning are not performed.

It is to be noted that whether or not to issue a regular reflection warning is left to the photographer as described above. Regular reflection light is a problem mainly in photographing in the character image mode, and is the same as in ordinary photographing. On the other hand, in the natural image mode in which shooting is performed, specular reflection light may be effectively used as a shooting effect, so that a specular reflection warning can be issued as necessary in consideration of a shooting purpose, a shooting scene, and the like. Things. Therefore, the regular reflection warning may be always performed without providing the regular reflection warning switch 20.

FIG. 11 is a block diagram of the camera 1 according to the present invention. In the figure, the same members as those described above are denoted by the same reference numerals. Also, the CCD driving unit 3
1 controls the imaging operation of the CCD 21 based on the shutter speed of the exposure control value input from the CPU 30. The CCD 21 includes a color area sensor, performs an imaging operation (charge accumulation operation) based on a control signal input from the CCD driving unit 31, converts pixel signals of each of R, G, and B color components into a time-series signal and converts the image into an image. Processing unit 32
Output to

The image processing section 32 performs predetermined signal processing on the pixel signal output from the CCD 21 and outputs the processed signal to the hard disk card 13. The image processing unit 32 has A /
D converter 321, image memory 322, first γ characteristic setting unit 323, second γ characteristic setting unit 324, first γ correction unit 32
5. Second gamma correction unit 326 and switch circuits 327 and 32
8 and when illuminance unevenness correction is instructed, illuminance unevenness correction is performed. Illuminance unevenness correction is performed by setting a γ characteristic for illuminance unevenness correction for each block, and performing gamma correction using the γ characteristic. At this time, the γ characteristics for the portion between the center positions of the blocks are interpolated, and the image signal of this portion is gamma-corrected using the interpolated γ characteristics, whereby discontinuity in image quality based on the difference in γ characteristics between the blocks is reduced. Be relaxed.

The A / D converter 321 converts each pixel signal included in the image signal read from the CCD 21 into a digital signal (hereinafter, referred to as pixel data).

The image memory 322 stores the pixel data output from the A / D converter 321. The image memory 322 has a capacity capable of storing pixel data of one captured image, and can perform image processing of the captured image at a time.

When the image data is divided into blocks, the capacity of the image memory 322 of the memory is divided into a plurality of blocks at the maximum block size that can be set so that image processing can be performed in units of rows of the blocks. In this case, the capacity may be set to be able to store the pixel data included in the blocks arranged in at least one row, and the memory may be reduced. That is, for example, as shown in FIG.
Is the maximum block size of 3 × 3 blocks B (1) to B
Assuming that the image memory 322 is divided into (9), the capacity of the image memory 322 is changed to blocks B (1) to B (3),
(4) to B (6) and a capacity capable of storing the pixel data included in the blocks B (7) to B (9).

The first γ characteristic setting section 323 sets a γ characteristic for correcting illuminance unevenness of a captured image. The first γ characteristic setting unit 323 divides the captured image into a plurality of blocks, and sets γ characteristics for illuminance unevenness correction using pixel data included in each block for each block. The second γ characteristic setting unit 324 sets the γ characteristic for enhancing the black density of the image after the illuminance unevenness correction. The second γ characteristic setting unit 324 sets C
The gamma characteristic for black density enhancement is set based on the operation information of the black density adjustment switch 18 input from the PU 30.

The first γ correction section 325 is a circuit for performing gamma correction on a natural image, and the second γ correction section 326
Is a circuit for performing gamma correction on a character image. First
The γ correction unit 325 performs gamma correction on pixel data read from the image memory 322 using a γ characteristic suitable for a natural image set in advance. The second γ correction unit 326 divides the captured image of the character image into a plurality of blocks, and
After performing gamma correction of the pixel data constituting the captured image using the γ characteristic for illuminance unevenness set by the γ characteristic setting unit 323, the γ for black density enhancement set by the second γ characteristic setting unit 324. Gamma correction of pixel data is performed using characteristics. Note that gamma correction for a character image will be described later.

The switch circuit 327 is connected to the image memory 3.
22 and the connection between the first and second γ correction units 325 and 326. The switch circuit 328 includes the first and second γ correction units 325 and 326.
The connection between the γ correction units 325 and 326 and the hard disk card 13 is switched. Switch circuit 327,
The switching control at 328 is performed by a control signal output from the CPU 30 in accordance with the setting state of the illuminance unevenness correction switch 17, and the illuminance unevenness correction switch 17 is set to “OFF” (the natural image mode is set). The image memory 322, the first γ correction unit 325, the first γ correction unit 325, and the hard disk card 13 are connected, and the illuminance unevenness correction switch 17 is set to “ON” (the character image mode is set). ), The image memory 322, the second γ correction unit 326, the second γ correction unit 326, and the hard disk card 13 are connected.

Here, a method of gamma correction (illuminance unevenness correction and black enhancement correction) for a character image will be described.

As described above, in the case of a character image, it is desirable to increase the clarity of the character portion relative to the white background portion. Therefore, as shown in FIG. A γ characteristic in which the output level is saturated at a predetermined input level W is used.

The white saturation level W in the γ characteristic is
For example, a histogram of the level distribution of the pixel data of the green component forming the image of the character image is created, and the class having the maximum frequency within the range corresponding to the white background portion is set. That is, when a histogram of the level distribution of the pixel data of the green component is created for an image obtained by photographing the whiteboard 23 on which characters, graphics, and the like are drawn, as shown in FIG. 15, the histogram generally corresponds to a white background portion (board portion). A level w corresponding to a peak of the mountain U corresponding to a mountain U and a mountain C corresponding to a black character portion (character portion) is set as a white saturation level W of the γ characteristic.

The white saturation level W is determined from the histogram of the green component pixel data constituting the entire captured image.
The gamma correction may be performed on the entire captured image by using the gamma characteristic.
3 has a large variation in character density (ratio of a character portion to a white background portion), and in the case of photographing, unlike a copier or the like equipped with a lighting device, the light source is not constant, and Since the illuminance distribution greatly changes within the illuminance, illuminance unevenness in the imaging screen becomes large. It is desirable to correct the illuminance non-uniformity.

In the camera 1 according to the present embodiment, in the case of a normal photographing mode (ie, in the case of front photographing), FIG.
As shown in FIG. 6, the captured image G is vertically and horizontally n (= K (vertical) ×
L (horizontal) blocks B (I, J) (I = 1, 2,... K,
J = 1, 2,... L), and γ characteristics for illuminance unevenness correction representing the block B (I, J) are set for each block B (I, J). In this case, block B
The size (area) of (I, J) is set to a size that can accommodate approximately 9 (= 3 × 3) characters. Thus block B
The reason why the size of (I, J) is relatively set in relation to the number of characters is that when a histogram is created using the pixel data in the block, the peak U of the portion corresponding to the whiteboard 23 has an appropriate size. This is to make it possible to reliably detect the peak position w of the peak U.

That is, as shown in FIG. 17A, when the block size is set to be relatively small with respect to the character, the area occupied by the character portion in the block B (I, J) is large, and Since the peak U of the portion corresponding to the whiteboard 23 becomes low, the peak position w of the peak U may be erroneously detected. As shown in FIG. If the size is set to a large size, the illuminance unevenness in the block B (I, J) is large, and the peak U of the portion corresponding to the whiteboard 23 of the histogram becomes gentle. This is because it may be detected.

In order to determine the block size, it is necessary to know the size of the character projected on the shooting screen. The size y ′ of the character projected on the shooting screen is determined by the size of the character written on the whiteboard 23. Y ′ = y ·
m, and the size y of the characters written on the whiteboard 23 is considered to be within a certain range even though there are individual differences.
The representative value y0 of the character size y written in 3 and the photographing magnification m
If 0 is experimentally determined, the size y ′ of the character projected on the photographing screen can be uniquely determined from the photographing magnification m.

In this embodiment, a reference block size S0 is determined based on the size y0 of a character projected on a photographing screen at a certain photographing magnification m0, and the block size S0 at an arbitrary photographing magnification m is determined. Is calculated from the photographing magnification m0 and the block size S0 by an arithmetic expression of S = S0 · m / m0. Therefore, if it is assumed that a block having the block size S0 includes vertical and horizontal (i × j) pixel data, the number i ′ of the pixel data included in the block size S in the vertical direction is i · m / m0, Number in the horizontal direction
j ′ is j · m / m0.

In the present embodiment, the block size S is set so that the number of characters in the block is nine. However, this is an example, and the size y of the character written on the whiteboard 23 is set. Is changed, the number of characters in the block also changes. Therefore, the block size S is appropriately set to include an appropriate number of characters according to the setting of the representative value y0.

In the present embodiment, the block size S is changed according to the photographing magnification m. However, the block size S0 is fixed, and in photographing a character image, the photographing magnification m is changed to the block size. Predetermined value m for S0
The adjustment may be made to be zero. That is,
As shown in FIG. 18, a block frame 43 corresponding to the block size S0 is displayed in the finder visual field frame 42,
The photographer may adjust the zoom ratio of the photographing lens 2 or the subject distance so that nine characters written on the whiteboard 23 in the block frame 43 are included. Further, the block frame 43 may be always displayed, or may be displayed only when the character image mode is set.

Further, in the above embodiment, histograms are created for all the set blocks B (I, J),
The white saturation level W of the γ characteristic for illuminance unevenness correction is set from this histogram. FIG. 19 shows the case where the illuminance unevenness is relatively small in the vertical direction and large in the horizontal direction only. B (3,1), B (3,2),... B (3,9) in the horizontal direction passing through the center of the captured image G
, A white saturation level W of the γ characteristic is set from the histogram, and other blocks B (I, J) (I = 1, 2, 4, 5, J = 1, 2,... 9) For, the γ characteristic set in the block B (3, r) set in the column including the block may be applied. For example, block B (1,1) included in the first column,
Block B (3,1) for B (2,1), B (4,1), B (5,1)
Apply the γ characteristic set in.

Conversely, when the illuminance unevenness is relatively small in the vertical direction and is large only in the horizontal direction, as shown in FIG. 20, a vertical block B (1,5, ), B (2,5),..., B (5,5), a histogram is created, a white saturation level W of the γ characteristic is set from the histogram, and other blocks B (I, J) (I = 1 , 2,
.. 5, J = 1 to 4, 6 to 9), the γ characteristic set in the block B (r, 5) set in the row including the block may be applied. For example, blocks B (1,1), B (1,2), B (1,3), B (1,1) included in the first row
4), B (1,6), B (1,7), B (1,8), B (1,9) apply the γ characteristic set in the block B (1,5). In this way, the calculation time of the γ characteristic can be reduced and the set γ
The capacity of the memory for storing the characteristics can be reduced.

Further, in the above embodiment, the entire captured image G is equally divided into a matrix and divided into blocks B (I, J).
Are set continuously, but a plurality of blocks B (I, J) may be set discretely in the imaging screen G as shown in FIG. In this manner, the number of blocks is reduced, so that the calculation time for setting the γ characteristic can be reduced as in the above example, and the capacity of the memory for storing the calculated γ characteristic can be reduced. Can be.

Next, a method for determining a γ characteristic for correcting uneven illuminance from a histogram of pixel data of a green component will be described.

(I × j) included in block B (I, J)
Pixel data g (1,1), g (1,2),... G (i-1, j), g (i,
In j), pixel data of X (%) set in advance is removed by integrating from the maximum level to the low level side, and a histogram of a level distribution is created using the remaining pixel data.
For example, if the total number of pixel data contained in a block is 1000
Assuming that there are no pixel data and X = 3%, 300 pixel data obtained by integrating sequentially from the pixel data at the maximum level q to the low level side is removed, and a histogram is formed using the remaining 9700 pixel data. Created. X% on high level
The reason for removing the pixel data is to avoid adverse effects such as noise.

This histogram generally has a two-peak distribution as shown in FIG. 22. The high-level peak U corresponds to the background portion of the whiteboard 23, and the low-level peak C
Is equivalent to the character part. The class p in FIG.
Is the maximum level of the pixel data included in the block B (I, J), and the class q (<p) is the maximum value of the class of the histogram.

When the histogram is created, the maximum class p
, The class w having the highest frequency in the distribution included in the range d set in advance to the low level is calculated, and this class w is set as the white saturation level W of the γ characteristic for illuminance unevenness correction. Since the block size is set to a predetermined size in relation to the number of characters in the range d, it is estimated that only the high-level mountain U is surely included in a block photographed with normal illuminance. Range. For example, when the pixel data is 8 bits and has a gradation of 0 to 255, the range d is set to about 48.

Therefore, for example, if the maximum class q is 200, a class w having the maximum frequency within the class range 152 to 200 is calculated. If the class w is, for example, w = 180, the white saturation level W = 180, and the γ characteristic as shown in FIG. 23 is determined.

If the whiteboard 23 is not completely white and slightly colored, or if the white balance adjustment of the camera 1 is improper, the γ for correcting unevenness of illuminance is used.
Since the gamma value of the equivalent gamma characteristic of the gamma correction performed according to the characteristic and the gamma characteristic for black enhancement is relatively large, the gamma characteristic for illumination unevenness correction set using the pixel data of the green component is changed to the red component. It cannot be applied to gamma correction of pixel data of blue and pixel data of blue component.

That is, the photographing data in a certain area of the whiteboard 23 is not completely white, and the levels D _R , D _G , and D _B of the pixel data of each of the R, G, and B color components are, for example, (D _R , D _G , D _B ) = (130, 140, 125), and the equivalent γ characteristic of the γ characteristic for illuminance unevenness correction and the γ characteristic for black enhancement set using the pixel data of the green component ( The γ characteristic obtained by superimposing both γ characteristics) is shown in FIG.
When the gamma correction is performed on the pixel data of the red component and the pixel data of the blue component using the γ characteristic, the output of each color component becomes (D) as shown in FIG.
_R , D _G , D _B ) = (185, 255, 140)
The image after the gamma correction causes a large color shift in yellow-green.

If the γ value of the γ characteristic shown in FIG. 24 is small (if the inclination is gentle), the output difference between the respective color components after the gamma correction is small, so that the color misregistration hardly causes a problem.
Since the γ characteristic applied to the character image mode is for performing gamma correction close to the binarization process, the γ value is set relatively large, so that the γ characteristic set using the green component pixel data is used. It is difficult to apply gamma correction to pixel data of red component and pixel data of blue component.

As a method of avoiding the above-described coloring phenomenon of the white portion, pixel data of each of the R, G, and B color components is converted into luminance data and color difference data, and gamma correction is performed using only the luminance data. Again, a method of reverse conversion to pixel data of R, G, B color components is conceivable. However, in this method, since color difference data is stored, for example, characters written on a white board are thinned with ink. If the character is a color character, the character remains faint even after gamma correction, and it is difficult to clearly reproduce the faint character.

In the present embodiment, the gamma characteristic for illuminance unevenness correction set by the pixel data of the green component is corrected to set a dedicated gamma characteristic for each color component, and a dedicated gamma characteristic is set for each color component.
By performing gamma correction on the characteristics, even light-colored characters can be clearly reproduced.

The gamma characteristic for each color component is, for example, a level margin value of "5" and an input level (D _R -5,
D _G -5, D _B -5) are formed so that white saturation level is set using the pixel data of each color component. For example, FIG.
In the example of the γ characteristic shown in FIG. 25, as shown in FIGS. 25A to 25C, the input level (125, 1) of each of the R, G, and B color components
35, 120) becomes the white saturation level 255,
The γ characteristics of each of the R, G, and B color components are set.

The gamma correction is performed so that the colored white portion becomes white, so that the colored portion is shifted from the original color. However, in character images, information is more important than color reproducibility. It is considered that some color misregistration is acceptable.

In the above description, a histogram of the level distribution of the pixel data included in the block is created, and the white saturation level is determined using the histogram (ie, the γ characteristic is set). Alternatively, the γ characteristic may be set by calculating pixel data instead of the histogram.

Now, each block B (I,
J) A gamma characteristic for illuminance non-uniformity correction is set for each block, and the gamma correction of the image is performed in block units using the γ characteristic. The image quality changes suddenly, which may cause a boundary line (false line). That is, the level of the white background suddenly changes at the boundary of the block, and this discontinuity in the level of the white background may occur as a boundary line.

Therefore, in this embodiment, each block B
The gamma characteristic for illuminance unevenness correction set for each (I, J) is defined as the γ characteristic for the pixel data at the center position of the block B (I, J), and the illuminance unevenness for the pixel data between the center positions of the adjacent blocks. The γ characteristic for correction is linearly interpolated using the γ characteristic for illuminance unevenness correction of both blocks, and the linearly interpolated γ characteristic
By performing gamma correction on pixel data other than the center position in characteristics, discontinuity in image quality based on differences in γ characteristics between blocks is reduced.

That is, as shown in FIG. 26, each of the blocks B (I, J), B (I, J + 1), B (I + 1, J), and B (I + 1, J + 1) Assuming that the center positions are A, B, C, and D, γ for illuminance unevenness correction with respect to an arbitrary position P in an area AR1 surrounded by ABCD.
The characteristics are represented by blocks B (I, J), B (I, J + 1), B (I + 1, J), B
Linear interpolation is performed using the γ characteristic for illuminance unevenness set for each (I + 1, J + 1), and gamma correction of the pixel data at the position P is performed using the interpolated γ characteristic.

The interpolated γ characteristics for illuminance unevenness correction with respect to the position P are represented by blocks B (I, J), B (I, J + 1), B (I + 1,
J) and B (I + 1, J + 1), the calculated white saturation levels W _A , W _B , W _C , and W _D are treated as for positions A, B, C, and D. White saturation level W
_A value W _P which is internally divided into the position P from the positions _A , W _B , W _C and W _{D with} respect to the positions A, B, C and D is calculated and set by the following equation (1).

[0089]

(Equation 1)

In the above internal division method, blocks B (1,1) to B (1, L), B (2, L) to B (K, L),
In B (K, L-1) to B (K, 1) and B (K-1,1) to B (2,1), the gamma characteristic of the portion outside the center position of each block is not interpolated. For this portion, linear interpolation of the γ characteristic may be performed by the external division method.

The γ characteristic may be interpolated at all positions except the center position of each block B (I, J). The block may be divided into blocks containing data (for example, 4 × 4 pixels to 6 × 6 pixels), and the γ characteristic may be linearly interpolated on a block-by-block basis to reduce the time for the interpolation operation.

In the above-described interpolation processing of the γ characteristic for illuminance unevenness correction, since the γ characteristic is set for each pixel position, a block centering on each pixel position is set, and the pixels included in the block are set. A similar result can be obtained by setting the γ characteristic using the histogram of the data level distribution. However, this method requires a long time to calculate the γ characteristic because a large number of blocks are set in the captured image G. There is a disadvantage that requires. Further, since almost all of the pixel data overlaps between adjacent blocks, there is almost no difference in the created histogram, and there is no benefit in creating histograms for both blocks. It employs linear interpolation processing of γ characteristics that can perform calculations and can reduce the memory capacity.

FIG. 12 shows A / D converters 321 to first and second γ correction sections 325 for performing image processing of a color image.
326 is a block diagram showing the configuration up to 326. FIG.

Image memory 322, first γ characteristic setting unit 32
3. The first and second γ correction units 325 and 326 and the switch circuit 327 have three processing circuits having the same structure corresponding to the pixel data of each of the R, G, and B color components.

For example, the pixel signal of the R color component is A / D converted into pixel data by the A / D converter 321A, and then temporarily recorded in the image memory 322A. In the natural image mode, the pixel data of the R color component stored in the image memory 322A is read out to the first γ correction unit 325A via the switch circuit 327, and the gamma correction is performed using the predetermined natural image γ characteristic. Is performed.

On the other hand, in the character image mode, the γ characteristic for illuminance unevenness correction is set by the first γ characteristic setting section 323A from the histogram of the level distribution of the R pixel data included in each block, and the second γ characteristic is set. Setting part 3
24 sets the γ characteristic for black adjustment based on the adjustment value of the black density adjustment switch 17. Then, the pixel data of the R color component stored in the image memory 322A is read out to the second γ correction unit 326A via the switch circuit 327, and each block has a γ characteristic for illuminance unevenness correction and performs gamma correction. After that, gamma correction is performed using the gamma characteristic for adjusting black density.

The pixel signal of each of the G and B color components is processed in the same manner as the pixel signal of the R color component.

FIG. 13 shows the first color component of G.
FIG. 13 is a block diagram illustrating an internal configuration of a γ characteristic setting unit 323B. In the figure, a block size setting unit 323a sets a block size for dividing a captured image into small image blocks B (I, J). The block size setting unit 323a is configured to divide the captured image into blocks.
The block size S is set using the photographing magnification m at the center of the photographing screen input from the CPU 30 and the preset reference size S0 and reference photographing magnification m0.

The address generator 323b generates an address of the pixel data included in each block B (I, J) based on the block size S set by the block size setting unit 323a. This address data is stored in the CCD2
The A / D converter 321 reads out the pixel signal from No. 1 and uses it for A / D conversion, and also uses the white saturation level interpolation calculation unit 323e for interpolation calculation.

The histogram creating section 323c creates a histogram (see FIG. 22) of the level distribution of the pixel data contained in each block B (I, J). The white saturation level setting unit 323d sets the white saturation level W of the γ characteristic with respect to the center position of each block B (I, j) using the histogram created by the histogram creation unit 323c (see FIG. 23). The white saturation level interpolation calculator 323e uses the white saturation level W of the γ characteristic set for each block B (I, j) to
The white saturation level W of the γ characteristic for the portion other than the center position of (I, j) is set by interpolation.

The γ-characteristic setting unit 323f sets the γ-characteristic for illuminance unevenness correction for each pixel data of the captured image using the white saturation level W set by the white saturation level setting unit 323d and the white saturation level interpolation calculation unit 323e. Is what you do.

When the specular reflection warning switch 20 has instructed the specular reflection warning, the specular reflection detection unit 323g determines whether the captured image includes an image of the illumination light specularly reflected by the main subject in block units. This is to determine and detect a photographed image including a specularly reflected light image. 323g regular reflection detector
Determines whether or not each block B (I, J) contains an image of specularly reflected light based on the shape of the histogram created for each block.

That is, when character information such as characters and figures written on the whiteboard 23 is photographed, if illumination light such as sunlight from a ceiling light or the outside of a window is specularly reflected by the whiteboard 23, Since the pixel data having received the specular reflected light outputs the pixel data of the saturation level, in the block including the image of the specular reflection light, most of the pixel data constituting the image of the whiteboard 23 is the pixel data of the saturation level. ing. Therefore, as shown in FIG. 27, the shape of the histogram for this block is such that the class w having the maximum frequency of the mountain U corresponding to the whiteboard 23 substantially matches the maximum class p.

The specular reflection detecting section 323g calculates the class w having the maximum frequency of the mountain U corresponding to the whiteboard 23 of the histogram in the same manner as the method of setting the white saturation level W in the γ characteristic for correcting the illuminance unevenness. In addition, the calculation result is compared with the maximum class p, and the class w is changed to the maximum class p.
When it substantially matches, it is determined that the block includes an image of specularly reflected light. Then, the result of this determination is
Output to U30.

The CPU 30 sounds the buzzer 16 in accordance with the result of the discrimination by the specular reflection detection section 323g,
4 is turned on to warn that the captured image contains specularly reflected light.

The first γ characteristic setting sections 323A and 323C for the R and B color components have the same internal configuration as the first γ characteristic setting section 323B for the G color component except for the regular reflection detection section 323g. .

Returning to FIG. 11, the card drive unit 33 controls the drive of the hard disk card 13 to record image data. The light emission control unit 34 controls light emission of the flash 7. The LCD drive unit 35 controls a monitor display of a captured image on the LCD display unit 19 based on a control signal from the CPU 30. The memory 36 stores various data calculated by the CPU 30.

The lens driving section 37 controls the focusing operation of the taking lens 2 based on the AF control value input from the CPU 30. Further, the zoom drive unit 38 is provided with
The zoom operation of the photographing lens 2 is controlled based on the drive signal input from the camera. The aperture driving unit 39 is a CPU 3
The aperture of the aperture 22 is controlled based on the aperture value Av of the exposure control value input from 0.

The photometric section 40 is composed of a light receiving element such as an SPC provided at a position behind the photometric window 3 and measures the luminance of the subject. The distance measuring unit 41 detects the subject distance, and is provided at a position behind the light projecting window 4, and is provided at a position behind the light projecting unit 411 that emits infrared light and the light receiving window 5, and reflected by the subject. A light receiving section 412 for receiving infrared light.

The CPU 30 centrally controls the photographing operation of the camera. CPU30 has an imaging magnification calculator 301 calculates the photographing magnification m _A in object distance D _A and its distance measuring point in the detected distance measuring point in the distance measurement unit 41 (the center position A of the imaging surface of the CCD 21) . CPU3
Reference numeral 0 denotes an exposure control value calculation unit 302, which controls an exposure control value (aperture value A) based on luminance information of a subject detected by the photometry unit 40.
v, shutter speed Tv), and outputs the calculation results to the aperture drive unit 39 and the CCD drive unit 31, respectively. Further, CPU 30 has an AF control value calculation unit 303, a photographing lens 2 based on the detected object distance D _A distance measuring unit 41 calculates the lens driving amount for setting the in-focus position, the calculation result Is output to the lens drive unit 37 as an AF control value.

Next, regarding the photographing control of the camera 1,
This will be described with reference to the flowcharts in FIGS. It is assumed that the shooting / playback switch 12 is set to the shooting side. Further, when the camera 1 is activated and the S1 switch is turned on by the shutter button 10, capture of the subject image and image processing are performed by the CCD 21 at a predetermined cycle, and when the S2 switch is turned on, the image captured thereafter is displayed. The data is recorded on the hard disk card 13 through predetermined image processing.

When the main switch 14 is turned on, the camera 1
Is activated, the camera is ready for shooting. When the zoom switch 11 is operated in this state (YES in # 2), the zoom lens in the photographing lens 2 is driven according to the operation direction and the operation amount, and the zoom ratio is changed (# 4). Thereafter, when the shutter button 10 is half-pressed and the S1 switch is turned on (YES in # 6), the process shifts to step # 8, and processing for photographing preparation is performed.

[0113] That is, first, the object distance D _A is detected by the distance measuring unit 41 (# 8). The distance measuring unit 41 is the light emitting unit 4
11 emits infrared light for distance measurement toward the object, receives the reflected light of the infrared light from the object at the light receiving unit 412, captures the data for distance measurement, and uses this data to capture an image. calculates a distance D _a from the imaging surface to the subject in the center of the screen. Subsequently, the lens driving amount for setting imaging lens 2 to an in-focus position based on the calculated object distance D _A is calculated (# 10).

Subsequently, it is determined whether or not a regular reflection warning is instructed by the regular reflection warning switch 20 (# 1).
2) If a specular reflection warning is instructed (YE in # 12)
S), regular reflection warning processing is performed in steps # 14 to # 20, and if a regular reflection warning is not instructed (N in # 12)
O), Steps # 14 to # 20 are skipped, and the regular reflection warning process is not performed.

In the regular reflection warning process, first, the subject distance D
_{From A} and the focal length f of the photographic lens 2, a photographic magnification m _A (= a · f / D _A , a; proportional coefficient) at the center of the photographic screen is calculated (# 14), and then the subroutine “Positive” shown in FIG. In accordance with the flowchart of "reflection light detection", an image of specular reflection light in the captured image is detected (# 16).

The detection of the image of the specularly reflected light in the photographed image is performed by first detecting the photographing magnification m _A and a preset reference photographing magnification m 0.
And a block size S (= S0 · m _A / m) for dividing the captured image into blocks using the block size S0 and the block size S0.
0) is calculated (# 70), and the number n of blocks to be divided is calculated from the block size S and the size of the imaging surface (# 72).

Subsequently, the counter M for counting the number of blocks is set to "1"(# 74). Since the order of the blocks in the regular reflection light detection processing is performed in the raster direction in the block division shown in FIG. 16, M = L · (I−1) + J, and the block B (I,
J) corresponds to the block B (L · (I−1) + J).

Subsequently, all the pixel data contained in the block B (M) are read out (# 76), and the pixel data obtained by excluding the high-level X% of these pixel data is shown in FIG. A histogram as shown in FIG. 22 or FIG. 27 is created (# 78). Subsequently, a class w corresponding to the peak value of the mountain U corresponding to the white background portion of the histogram is calculated (# 80), and this class w is used as the maximum class p of the histogram.
(= 255) or not (##).
82).

If the class w substantially coincides with the maximum class p (YES in # 82), it is determined that the image of the regular reflection light is included in the block, and the flag FLAGH is set to "1" ( # 90), and return. Note that the flag FLA
GH is a regular reflection light detection flag. When set to “1”, it indicates that the regular reflection light image is included in the photographed image. Indicates that an image of specularly reflected light is not included in.

If the class w does not substantially coincide with the maximum class p in step # 82, the count value of the counter M becomes "1".
Then, it is determined whether or not the count value M is larger than the total number of blocks n (# 84).
86), if M ≦ n (NO in # 86), step #
Returning to 76, it is determined whether or not an image of specular reflection light is included in the next block B (M) (# 76 to # 76).
# 82).

If the image of the specular reflection light is not detected in all the blocks B (M) (YES in # 86), it is determined that the captured image does not include the image of the specular reflection light, and the flag FLAGGH is determined. Is reset to "0"(# 88), and the routine returns.

Returning to FIG. 28, when the process of detecting the regular reflection light is completed, the presence or absence of the image of the regular reflection light is determined by the flag FLAGH (# 18), and the flag FLAGH is set to "1" (the image of the regular reflection light). If there is) (Y in # 18)
ES), a regular reflection warning is given by the buzzer 16 and the LED display 24 (# 20). On the other hand, if the flag FLAGH is reset to “0” (no image of specular reflection light) (NO in # 18), step # 20 is skipped, and the specular reflection warning by the buzzer 16 and the LED display 24 is not performed. .

Subsequently, the luminance data (photometric data) of the subject is taken in by the photometric section 40 (# 22), and an exposure control value is calculated based on the photometric data (# 24).
Further, it is determined whether or not the illuminance unevenness correction is instructed by the illuminance unevenness correction switch 17 (# 26 in FIG. 29). If the illuminance unevenness correction is instructed (YES in # 24), the light emission control unit 34 emits light. If the control signal for prohibition is output and the light emission of the flash 7 is prohibited (# 28), and the illuminance unevenness correction is not instructed (NO in # 24), step # 28
Is skipped, and flash emission of the flash 7 is not inhibited. As a result, the photographing preparation processing ends, and the camera enters a release standby state.

The reason why the emission of the flash 7 is inhibited when the illumination unevenness correction is instructed is as follows.
For example, when the flash 7 is automatically fired in a scene in which a picture is taken from the front of the whiteboard 23, the flashlight is totally reflected by the whiteboard 23 and characters in the captured image may not be legible. This is to prevent a shooting mistake.

In the release standby state, the shutter button 10
Is fully pressed and the S2 switch is turned on (YES in # 30), the flow shifts to step # 34 to perform a release operation. On the other hand, if the shutter button 10 is half-pressed and the S1 switch is on (Y in # 32)
ES), the flow returns to step # 8, and the above-described shooting preparation processing is repeated (loop of # 8 to # 32). When the operation of the shutter button 10 is released and the S1 switch is turned off (NO in # 32), the process returns to step # 2.

When the operation shifts to the release operation, first, the data of the lens driving amount is output to the lens driving section 37, and after the focus of the photographing lens 2 is adjusted (# 34), the data of the aperture value Av of the exposure control value is obtained. Is output to the aperture drive unit 39,
The aperture of the stop 22 is adjusted (# 36).

Subsequently, it is determined whether or not illuminance unevenness correction is instructed (# 38). If the illuminance unevenness correction is instructed (YES in # 38), it is determined whether the image is divided into a plurality of blocks. The block size S is calculated (# 40).
This calculation is performed by the same method as in step # 70 in the regular reflection light detection processing.

When the setting process of the block size is completed,
The data of the shutter speed calculated in step # 24 is output to the CCD driving section 31, and the image pickup operation (integration operation) by the CCD 21 is started (# 42). CCD21
Resets the electric charge of the photosensitive section based on the drive control signal from the CCD driving section 31, and then accumulates the electric charge in the photosensitive section for a predetermined time (charge integration) to image the subject.

When the imaging operation by the CCD 21 is completed,
Reading of charges (pixel data) accumulated in each pixel of the photosensitive unit to the image processing unit 32 is started (# 4 in FIG. 30, FIG. 30).
4). As shown in FIG. 35, the pixel data of the CCD 21 is sequentially read in the direction of the arrow for each vertical line and input to the image processing unit 32. The pixel signal input to the image processing unit 32 is converted into pixel data by the A / D converter 321, stored in the image memory 322, and input to the first γ characteristic setting unit 323.

Subsequently, it is determined whether or not illuminance unevenness correction is instructed (# 46). If illuminance unevenness correction is instructed (YES in # 46), a subroutine "γ characteristic setting" shown in FIG. According to the flowchart of the above, the γ characteristic for illuminance unevenness correction is set for each block by the first γ characteristic setting section 323 (# 48).

For setting the γ characteristic for correcting the illuminance unevenness of each block, first, a counter M for counting the number of blocks is set to “1” (# 100). Note that the order of the blocks in the γ characteristic setting process is the same as the order of the blocks in the above-described regular reflection light detection process.

Subsequently, all the pixel data contained in the block B (M) are read out (# 102), and the pixel data obtained by excluding the high-level X% of the pixel data is used. A histogram as shown in FIG. 22 or FIG. 27 is created (# 104). Subsequently, a class w corresponding to the peak value of the mountain U corresponding to the white background portion of the histogram is calculated (# 106), and the class w is stored as the white saturation level W (M) of the γ characteristic for the block (M). (#
108).

Subsequently, the count value of the counter M becomes "1".
Then, it is determined whether or not the count value M is greater than the total block number n (# 112). If M ≦ n (NO in # 112), the process returns to step # 100. The white saturation level W (I) is set for the next block B (M) (# 102 to # 102).
110). When M> n (YE in # 102)
S), it is determined that the setting of the white saturation level W (M) of the γ characteristic has been completed for all the blocks B (M), and the process returns.

Returning to the flowchart of FIG.
Interpolation is performed on the white saturation level W (I) of the γ characteristic for illuminance non-uniformity set for each block B (I), to correct illuminance non-uniformity at pixel positions other than the center position of each block B (I). Is set (# 50). Subsequently, while the set γ characteristic is input to the second γ correction unit 326,
From the image memory 322 via the switch circuit 327, the second
The pixel data is read out to the γ correction unit 326, and the pixel data is subjected to gamma correction using the γ characteristic for illuminance unevenness correction corresponding to the pixel position, and further using the γ characteristic for black enhancement. Gamma correction is performed (# 52).

On the other hand, if illuminance unevenness correction has not been instructed in step # 46 (NO in # 46), image memory 322
, Pixel data is read out to the first γ correction unit 325 via the switch circuit 327, and the pixel data is subjected to gamma correction according to a preset natural image γ characteristic (# 54). Subsequently, the pixel data after gamma correction is written to the hard disk card 13 via the switch circuit 328 (# 56).

The pixel data on which the gamma correction has been performed are sequentially written to the hard disk card 13 via the switch circuit 328 (# 46 to # 58 loop).
When the writing of all pixel data to the hard disk card 13 is completed (YES in # 58), a control signal for ending the reading of the pixel data is output to the CCD driving unit 31, and the writing of the pixel data to the card driving unit 33 is performed. An end control signal is output, and the photographing operation for one image is completed (# 60), and the process returns to step # 2 to perform the next photographing process.

As described above, in the photographing preparation processing, the captured image is divided into a plurality of blocks, and the main subject (whiteboard 23) is placed in each block using a histogram created for each block. Since the regular reflection light is detected by determining whether or not the image of the regularly reflected illumination light is included, even the spot-like regular reflection light can be reliably detected. Since a regular reflection warning is issued to the photographer according to the detection result, for example, the subject is a character or a figure written on the whiteboard 23, and the character is reflected by the regular reflection of the illumination light on the whiteboard 23. When the information such as a figure or the like becomes unclear, it is possible to prevent such an erroneous photographing of an image having a low information value by a regular reflection warning.

In the above embodiment, when specular reflection light is detected, only a specular reflection warning is issued. However, an image in which character information becomes unclear due to specular reflection of illumination light is a recording value. Therefore, in consideration of the effective use of the memory capacity of the hard disk card 13, not only the regular reflection warning but also the recording of the captured image on the hard disk card 13 may be prohibited. In this case, as shown in FIG. 33, in the flowchart of FIG. 29, for example, the determination of the setting state of the flag FLAGGH between step # 30 and step # 34 (the presence or absence of the image of the specular reflection light corresponding to step # 18) Step # 31 is performed, and if the flag FLAGH is set to "1" (YES in # 31), the flow returns to step # 8 to perform the shooting preparation process, and the flag FLAGH is set to "0". If it has been reset (NO in # 31), the process may proceed to step # 34. That is, as long as the flag FLAGH is not reset to “0”, even if the S2 switch is turned on, this processing may be ignored and the shooting preparation processing may be repeated.

In the above embodiment, when the shutter button 10 is fully pressed, regardless of the presence or absence of the regular reflection warning,
After performing predetermined image processing (illuminance unevenness correction) in accordance with an instruction from the illuminance unevenness correction switch 17 on the captured image, the image is recorded on the hard disk card 13, but a regular reflection warning is issued. In some cases, regardless of the setting of the illuminance unevenness correction switch 17, the captured image is subjected to image processing for normal photographing (that is, illuminance unevenness correction is not performed) and then recorded on the hard disk card 13. You may make it.

In this case, as shown in FIG.
9. In the flowchart of FIG. 30, step # 36
Between step # 38 and step # 44 and step #
Steps # 37 and # 45 for discriminating the presence or absence of an image of specularly reflected light by the flag FLAGGH are inserted between steps # 46 and # 46. If the flag FLAGGH is set to "1" in step 37 (# 37) YES), skip steps # 38 and # 40, and in step # 45
If the flag FLAGH is set to “1” (# 4
5 is YES), the process may proceed to step # 54.

As described above, when the captured image includes the image of the specular reflection light, the image processing is performed by switching the gamma correction to the gamma correction for normal photographing even if the illumination unevenness correction is instructed. It is possible to prevent the character information that has become unclear due to the specular reflection light from being further obscured by the illuminance non-uniformity correction, thereby preventing the adverse effect of increasing the deterioration in image quality and information value.

[0142]

As described above, according to the present invention,
In a digital camera that photoelectrically converts a subject light image into a pixel signal by an imaging unit including a plurality of photoelectric conversion elements and captures the image including the pixel signal on a recording medium, the captured image is divided into small images, For each small image,
Using the created histogram, the presence or absence of illumination light that is regularly reflected by the main subject is determined, and if regular reflection light is detected in any of the small images, a specific process such as a warning is performed. Even if the specular reflection light is in the shape of a circle, warning of the specular reflection light is performed with high accuracy, and it is possible to prevent erroneous photographing of a low-quality subject image that has become unclear due to the specular reflection light.

If the specular reflection light is detected in any of the small images, the recording of the captured image on the recording medium is prohibited. Erroneous photographing of the subject image can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a perspective view showing the appearance of a digital camera according to the present invention.

FIG. 2 is a rear view of the digital camera according to the present invention.

FIG. 3 is a schematic configuration diagram of an optical system of the digital camera according to the present invention.

FIG. 4 is a diagram illustrating an example of an illumination direction of illumination light of a whiteboard.

FIGS. 5A and 5B show output distributions of an image sensor, in which FIG. 5A shows a vertical output distribution, and FIG. 5B shows a horizontal output distribution.

FIG. 6 is a diagram showing a state in which a captured image is divided into a plurality of blocks.

FIG. 7 is a diagram illustrating an example of a γ characteristic that emphasizes a white background set for each block.

FIG. 8 is a diagram illustrating an example of a γ characteristic in which a black portion is emphasized.

FIG. 9 is a diagram illustrating a relationship between black adjustment by a black density adjustment switch and a γ characteristic that emphasizes a black portion.

FIG. 10 is a view showing an LED display for warning regular reflection light in the viewfinder.

FIG. 11 is a block diagram of a digital camera according to the present invention.

FIG. 12 shows an A / D for performing image processing of a color image.
FIG. 2 is a block diagram showing a configuration from a converter to first and second γ correction units.

FIG. 13 is a block diagram illustrating an internal configuration of a first γ characteristic setting unit for a G color component.

FIG. 14 is a diagram for explaining the capacity of an image memory.

FIG. 15 is a diagram showing a general form of a histogram of pixel data constituting a character image.

FIG. 16 is a diagram showing a state in which a captured image is divided into small images of a plurality of blocks.

17A and 17B show a state where a captured image is divided into blocks of inappropriate sizes, where FIG. 17A shows a case where the block size is smaller than an appropriate value, and FIG. 17B shows a case where the block size is larger than an appropriate value. FIG.

FIG. 18 is a diagram showing a state in which a block frame is displayed in a finder field frame.

FIG. 19 is a diagram for explaining a method of setting γ characteristics for illuminance unevenness correction for another block using γ characteristics for illuminance unevenness set in blocks arranged in the horizontal direction.

FIG. 20 is a diagram for explaining a method of setting γ characteristics for illuminance unevenness correction for another block using γ characteristics for illuminance unevenness set in blocks arranged in the vertical direction.

FIG. 21 is a diagram illustrating another block division method of a captured image for performing illumination intensity unevenness correction.

FIG. 22 is a diagram illustrating an example of a histogram of pixel data constituting a small image divided into blocks.

FIG. 23 is a diagram illustrating a γ characteristic determined using a histogram of pixel data.

FIG. 24 shows γ set using green component pixel data.
It is a figure showing an example of a characteristic.

25A and 25B are diagrams showing γ characteristics set for each image of each color component, where FIG. 25A shows γ characteristics for a red component image, and FIG.
Is a γ characteristic for a green component image, and (c) is a γ characteristic for a blue component image.

FIG. 26 is a diagram for describing interpolation calculation of γ characteristics for pixel data in an area surrounded by the center positions of four adjacent blocks.

FIG. 27 is a diagram illustrating a shape of a histogram of pixel data of a block including an image of specular reflection light.

FIG. 28 is a flowchart illustrating shooting control of the camera according to the present invention.

FIG. 29 is a flowchart showing shooting control of the camera according to the present invention.

FIG. 30 is a flowchart illustrating shooting control of the camera according to the present invention.

FIG. 31 is a flowchart of a subroutine “specular reflection light detection”.

FIG. 32 is a flowchart of a subroutine “γ characteristic setting”.

FIG. 33 is a diagram showing a modification of a flowchart for prohibiting recording of a captured image on a hard disk card when specular reflected light is detected.

FIG. 34 is a diagram showing a modification of a flowchart for forcibly switching gamma correction of a captured image to normal gamma correction when specular reflected light is detected.

FIG. 35 is a diagram illustrating a reading direction of pixel data of a CCD.

FIG. 36 is a diagram illustrating a method of dividing a captured image into blocks in a digital copying machine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Camera (digital camera) 2 Shooting lens 3 Metering window 4 Distance measuring light emitting window 5 Distance measuring light receiving window 6 Viewfinder objective window 7 Flash 8 Card slot 9 Card eject button 10 Shutter button 11 Zoom switch 12 Shooting / playback switch Reference Signs List 13 hard disk card (recording medium) 14 main switch 15 finder eyepiece window 16 buzzer (warning means) 17 illumination unevenness correction switch 18 black density adjustment switch 19 LCD display unit 20 regular reflection warning switch 21 CCD area sensor (imaging means) 22 aperture 23 White board 24 LED display (warning means) 30 CPU (specific processing means) 31 CCD drive section 32 Image processing section 321 A / D converter 322 Image memory 323 First γ characteristic setting section 323a Block size setting section (Image dividing means) 32 3b Address generation section 323c Histogram creation section (histogram creation means) 323d White saturation level setting section 323e White saturation level interpolation calculation section 323f γ characteristic setting section 323g Regular reflection detection section (determination means) 324 Second γ characteristic setting section 325 First γ correction Unit 326 Second γ correction unit 327 Switch circuit 33 Card drive unit 34 Light emission control unit 35 LCD drive unit 36 Memory 37 Lens drive unit 38 Zoom drive unit 39 Aperture drive unit 40 Photometry unit 41 Distance measurement unit 42 Viewfinder field frame 43 Block frame

Claims (3)

[Claims] 1. A digital camera which photoelectrically converts a subject light image into a pixel signal by an image pickup means comprising a plurality of photoelectric conversion elements and captures the image, and records an image comprising the pixel signal on a recording medium. Image dividing means for dividing the divided image into a plurality of small images, a histogram creating means for creating a histogram of a level distribution of pixel signals constituting each small image for each small image, and a histogram created for each small image. A determining means for determining whether or not the small image includes illumination light that is regularly reflected by the main subject, and when any of the small images includes the regularly reflected illumination light, a specific A digital camera comprising a specific processing unit for performing processing. 2. The digital camera according to claim 1, further comprising a warning unit, wherein the specific processing unit warns the main subject that the illumination light is regularly reflected by the warning unit. Digital camera that features. 3. The digital camera according to claim 1, wherein said specific processing means prohibits recording of the captured image in said recording means.