JP2003259196A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an auxiliary light irradiating device which has less power consumption and time lag than an auxiliary light irradiating device such as an electronic flash. <P>SOLUTION: For irradiation with auxiliary light, the light of a high-luminance lamp 13a is converged by a condenser lens 13c to irradiate a subject. To correct unevenness in the lightness of an image due to the converging operation, the center of the irradiation with the light is calculated from a subject distance measured by a range finder 2 and a photographed image is corrected according to the previously known light intensity distribution characteristic of the high- luminance lamp 13a. At the same time, problems of coloring of a subject caused by the high-luminance lamp 13a is also corrected through digital image processing. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera using an auxiliary light irradiating device capable of irradiating an object with auxiliary light to perform photographing.

[0002]

2. Description of the Related Art Conventionally, in order to enable shooting in a dark scene, light from a flash valve or xenon (Xe) is used.
There is known a camera using an auxiliary light irradiation device that compensates for exposure by light from a strobe device using a tube.

Further, in recent years, with the development of a non-flash type high-intensity lamp, a camera using this high-intensity lamp as a light source of an auxiliary light irradiating device instead of the strobe device is disclosed in Japanese Patent Laid-Open No. 10-268391. Is disclosed in.
In this way, a camera that uses a high-intensity lamp as a light source for an auxiliary light irradiation device consumes less power than a camera that uses a strobe device as a light source for an auxiliary light irradiation device, and there is no time lag due to high-voltage charging of the strobe device. ,
Further, since a charging circuit for charging is not necessary, it is possible to shorten the photographing time and downsize the camera.

Further, Japanese Patent Application Laid-Open No. 11-327012 discloses a technique for changing the brightness and color of a background image by digital image processing and synthesizing the image with a main subject image.

[0005]

However, since the light from the high-intensity lamp is insufficient in brightness as compared with the light from the strobe device or the like, the above-mentioned Japanese Patent Laid-Open No. 10-268 is known.
When the high-intensity lamp is used in the camera of Japanese Patent No. 391, it is premised that the high-intensity lamp is used in a short distance where the irradiation intensity is small. Further, the photographing system disclosed in Japanese Patent Laid-Open No. 11-327012 is a technique mainly used for a 3-minute photographing system and the like, and is a technique for producing a specific effect in the photographing box.

The present invention has been made in view of the above circumstances, and consumes less power than a camera using a strobe device or the like as a light source of an auxiliary light irradiation device, and has a small auxiliary light irradiation without a time lag due to charging. While using the device,
An object of the present invention is to provide a camera capable of taking a picture with natural exposure.

[0007]

In order to achieve the above object, a camera according to the present invention comprises an irradiation means for irradiating auxiliary light for exposure to an object within a limited area within a photographing field angle. A distance measuring means for measuring the distance to the subject, and an image processing means for performing image processing on the image taken according to the distance to the subject measured by the distance measuring means and the irradiation intensity distribution of the auxiliary light in the irradiation means. And.

According to the camera of the present invention, even when an object is illuminated with auxiliary light having a low illumination intensity and an image is taken, the area to be illuminated with light is narrowed down to a limited area within the angle of view of photography. This allows the image to reach far away, and the uneven brightness and color unevenness of the image caused by narrowing down the light can be corrected by digital image processing, so that a natural exposure can be taken even when using a light source with low irradiation intensity. it can.

In order to achieve the above object, the camera according to the present invention uses an image captured by using the light source according to an image pattern changed before and after illuminating the subject with auxiliary light from the light source. A color correction area determining means for determining the color correction area is provided.

According to the camera of the present invention, by comparing the image before illuminating the subject with the auxiliary light and the image after illuminating the auxiliary light, the colors of the portions where the image patterns of both are changed are corrected. , Finer color correction can be performed.

That is, according to the present invention, the distance measuring means measures the unevenness in the brightness of the photographed image due to the unevenness of the irradiation intensity distribution caused by the difference between the field of view of the photographing lens and the irradiation range of the illumination light source such as a lamp or LED. Corrected by the result,
In addition, the problem of coloring the image when an illumination light source that does not have a wavelength distribution characteristic close to that of sunlight, such as strobe light, illuminates the subject is stored in advance. It is intended to obtain a digital image without any unnaturalness by correcting it.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram showing a configuration including an electronic circuit of a camera according to a first embodiment of the present invention.

That is, the camera according to the first embodiment includes a CPU 1, a distance measuring device 2, a taking lens 6, a taking lens drive circuit (LD) 7, an image pickup device 8, an image processing circuit 9, a memory 10 and a display. The device 11, the photometric device 12, and the auxiliary light irradiation device 13 are included.

The distance measuring device 2 corresponds to the distance measuring means. Further, the image processing circuit 9 corresponds to the image processing means, and the auxiliary light irradiation device 13 corresponds to the irradiation means.

The CPU 1 is composed of a one-chip microcomputer or the like, and is a control circuit for controlling the photographing sequence of the camera according to the control program stored in the EEPROM 1b according to the operating state of various switches such as the release switch 1a.

The distance measuring device 2 includes an infrared light emitting diode (IR
ED) drive circuit 3a, IRED 3b, light projecting lens 4, light receiving lens 5, semiconductor light position detecting element (PSD) 6
a, a distance measuring IC (AFIC) 6b. Hereinafter, for the sake of simplicity, the distance measuring device 2 will be treated as a device capable of measuring the distance only in the central portion of the photographing screen 20.

The IRED drive circuit 3a drives the IR
When the ED 3b emits light, the light from the IRED 3b is projected through the light projecting lens 4 as distance measuring light toward a subject in the photographing screen 20 that is present at a position separated by the distance D ₁ .

The distance measuring light projected from the IRED 3b toward the subject existing in the photographing screen 20 is reflected by the subject. The reflected light reflected by the subject enters the PSD 6a via the light receiving lens 5. Here, x is between the subject distance D ₁ , the incident position x when the reflected light is incident on the PSD 6a, the principal point distance B between the light projecting lens 4 and the light receiving lens 5 and the focal length f of the light receiving lens 5. The relational expression of = Bf / D ₁ is established. PSD6 for AFIC6b
x is obtained from the output of a and this result is output to the CPU 1. In the CPU 1, the subject distance D is calculated based on the above relational expression.
Calculate ₁ .

After the subject distance D ₁ is calculated, the focus position for the taking lens 6 is calculated by utilizing the fact that the focus position is substantially proportional to the reciprocal of the subject distance D ₁ . Then, the CPU 1 sets the LD according to the calculated focus position.
7 is controlled to focus on the taking lens 6.

The image pickup device 8 converts an image of a subject received through the taking lens 6 into an electric signal to obtain an image.
It is an element composed of a plurality of pixels. The image acquired by the image sensor 8 is controlled by the CPU 1 and subjected to image processing such as compression in the image processing circuit 9. Then, the processed image can be stored in the memory 10 or displayed on the display device 11.

When shooting outdoors in the daytime, a clear image can be obtained because sufficient light enters the image pickup element 8 from the subject without auxiliary light. However, in a dark scene, the subject is not illuminated with the auxiliary light. You cannot get the image. Therefore, the photometric device 12 is operated to obtain the luminance information. The CPU 1 determines whether or not the subject needs to be irradiated with the auxiliary light from the auxiliary light irradiation device 13 based on the brightness information.

The photometric device 12 comprises a light receiving lens 12a for photometry, a photometric sensor 12b, and a photometric circuit 12c. At the time of shooting, the photometric sensor 12b receives light from the subject through the light receiving lens 12a. Then, the photometric circuit 12c obtains luminance information based on the output from the photometric sensor 12a, and outputs the result to the CPU 1.

Further, in this embodiment, a high-intensity lamp (lamp) 13a is used as a light source of the auxiliary light irradiation device 13. That is, the light source drive circuit 13b is driven to supply power to the lamp 13a, so that the light from the lamp 13a is emitted to the subject. Where the lamp 1
Since the light of 3a is weaker than the light of the auxiliary light irradiation device using a conventional strobe device or the like, it is necessary to sufficiently collect the light by the condenser lens 13c when the light is emitted from the lamp 13a. However, due to this condensing action, the positional difference between the condensing lens 13c and the taking lens 6 easily influences the image acquired by the imaging element 8.

That is, when the auxiliary light from the lamp 13a is condensed by the condenser lens 13c and is irradiated toward the subject existing in the photographing screen 20, the irradiation range of the auxiliary light is narrowed by the condensing action. Therefore, the irradiation range of light on the photographing screen 20 varies depending on the subject distance.

FIG. 2A is a diagram showing the irradiation range of the light irradiated on the photographing screen. For example, when the distance to the camera is D ₁ , the irradiation range is L ₁ , and when the distance to the camera is D ₂ , the irradiation range is L ₂ .

An example of the light intensity distribution of the lamp 13a is shown in FIG. 2 (B). Brightness _G 0 of the irradiation center, the first _{G 0}
The brightness of / 2 is G ₁ , and the brightness of 1/2 of G ₁ is G ₂ , G
When ₂ Brightness 1/2 of the G _3, when performing as described above taken using a lamp 13a having such light intensity distribution is made narrow irradiation range of the auxiliary light by the condensing action Therefore, the light of the lamp 13a on the shooting screen is attenuated as it deviates from the center of the irradiation position of the light. As a result, as shown in (a) of FIG. 3 (A), unevenness of exposure occurs such as B ₁ , B ₂ , B _3, ... According to the light intensity distribution.

Further, the image obtained by causing the image pickup device 8 to receive the reflected light from the subject in the photographic screen also has unevenness. At this time, the light receiving position on the image sensor 8 changes according to the object distances C ₁ and C ₂ . That is, the irradiation range of the auxiliary light changes according to the subject distance, and the light receiving position on the image pickup element also changes according to C ₁ and C ₂ and the subject distance. Therefore, the uneven brightness of the image on the image pickup element 8 is caused. Also changes depending on the subject distance.

Therefore, the object distance is measured by the distance measuring device 2, and which pixel of the image sensor 8 the center position C of the light intensity distribution of the auxiliary light is incident on is calculated based on the measured object distance. At this time, if the light intensity distribution is known in advance as shown in FIG. 2B, it is possible to understand how the light of the lamp 13a is attenuated from the center C of the light intensity distribution. That is, if the brightness of the image acquired by the image sensor 8 is corrected according to the amount of light attenuation of the lamp 13a, the uneven exposure can be corrected.

FIG. 3 is a state diagram of an image of a subject before and after the image is corrected and a distribution diagram of brightness on the image pickup device 8 corresponding to this image. For example, the image of the subject before image correction is in the state shown in (a) of FIG. 3A, and the brightness distribution on the image sensor 8 at that time is shown in FIG.
It is assumed that it is like (b) of (A). In this case, the distribution map shown in (a) of FIG.
2B, the output of the pixel C _A corresponding to the vicinity of the central position C of the light intensity distribution of FIG. 2B is reduced so that the peripheral portions P ₁ and P _{2 are} close to each other. By performing the correction to increase the output of the pixel of, the corrected image becomes
The image has a natural light intensity distribution without unevenness in brightness as shown in (a) of FIG.

Further, in the case of a digital camera, there is an example in which an image around the main subject is cut out and exchanged by e-mail or posted on a homepage. Not as important as a camera. Therefore, even a high-intensity lamp that emits light weaker than that of a strobe device can be used by focusing. Further, the unevenness of the brightness of the image caused by the light collection can be corrected by the digital image processing as described above.

With the above measures, the size of the light source in the auxiliary light irradiating device, its drive circuit, and the entire device can be reduced.

In the case of a lamp whose wavelength distribution characteristic is known in advance, not only the correction of the brightness by the light irradiation position as described above but also the sunlight and the lamp 13 shown in FIG.
The difference in the wavelength distribution of light from a can also be color-corrected to obtain a natural hue. Generally, the light of the lamp has a longer wavelength component (red component) and a shorter wavelength component (blue component) than sunlight, so by weakening the long wavelength component and strengthening the short wavelength component in the obtained image, , The image has a natural hue. The degree of this enhancement can be determined by the wavelength distribution characteristic of the lamp 13a as described above.

The control operation as described above is performed by the CPU 1 of the camera controlling the photographing sequence in the order shown in the flowchart of FIG. By such operation control, it is possible to provide an inexpensive camera that is capable of shooting in a bright place or a dark place, has a small size, consumes less power, and has a small release time lag.

First, the subject distance D is measured by the AFIC 6b (step S1). Then, the photographing lens 8 is focused via the LD 7 according to the measurement result (step S2). At this time, the light receiving lens 1
Luminance information is acquired by the photometric circuit 12c from the light received via 2a (step S3). Based on this brightness information, the CPU 1 determines whether or not the subject needs to be irradiated with the auxiliary light by the lamp 13a (step S4).

When it is determined that the auxiliary light irradiation from the lamp 13a is not necessary, the image pickup is performed without the auxiliary light irradiation from the lamp 13a (step S10). Next, after performing white balance processing for correcting the color components of the obtained image to obtain an image having a natural tint (step S11), the process proceeds to step S12.

When it is determined in step S4 that the illumination of the auxiliary light from the lamp 13a is necessary, the auxiliary light from the lamp 13a is emitted to the subject to capture an image (step S5). Next, based on the subject distance D measured in step S1, which pixel on the image sensor 8 corresponds to the center of the light intensity distribution is calculated (step S6), and the position of this pixel is determined. The center position is C. If the center position C is known, the output of the pixel located far from the center position C can be emphasized and the output of the pixel near the center position C can be corrected to be smaller than the pattern of the known light intensity distribution.

First, the brightness of the photographing screen is divided into areas by the output of the image pickup device 8 (step S7). For example,
In the present embodiment, as shown in (a) of FIG. 3 (A), five levels (B ₁ , B ₂ , B ₃ ,
The brightness was divided into areas with B ₄ and B ₅ ). Next, FIG.
In (a) of (A), for example, with reference to the region B ₃ , the brightness of the regions B ₁ and B _{2 that} are brighter than this is suppressed,
The brightness of the area B ₄ darker than the area B ₃ is emphasized (step S8). Note that, as described above, the strict brightness correction is not required for the peripheral area B ₅ , and therefore the processing regarding B ₅ is omitted here.

After the correction based on the light irradiation position, the color is corrected. As shown in FIG. 4, since the light of the lamp 13a has a long wavelength component and a short wavelength component, a correction is performed to strengthen the blue component and weaken the red component of the obtained image (step S9). In addition, since the color reproducibility deteriorates if the color of the portion where the lamp 13a does not illuminate is also corrected, for example, only the area B ₁ near the center C position is corrected.

As a more advanced color correction, the images before and after irradiation of the auxiliary light by the lamp 13a are compared, and among the images captured by irradiating the auxiliary light, the image changed from the image before irradiation of the auxiliary light. It is also possible to perform color correction only for the portion corresponding to. It should be noted that such control corresponds to the color correction area determination means and is included in the function of the CPU 1. The control of this color correction is shown in the flowchart of FIG.

First, an image is taken without irradiating the auxiliary light (step S40), and subsequently, an image is taken by irradiating the auxiliary light from the lamp 13a (step S41).

Next, these two images are compared with each other, and a portion corresponding to an image changed from the image before irradiation of the auxiliary light is detected in the image captured during irradiation of the auxiliary light (step S).
42). And weaken the red component of this detected part,
Correction is performed to strengthen the blue component (step S43).

After the image correction including the color correction in step S9 is completed, the image processing circuit 9 compresses the image (step S12) and stores the compressed image in the memory 13 (step S12). S13).

Next, the CPU 1 determines whether or not the captured image is displayed on the display device 11 by operating a monitor switch (not shown) or the like (step S14). When it is determined that the display is performed, the display is performed on the display device 11 (step S15), and then the control of this flowchart is finished. On the other hand, when it is determined that the display is not performed, the control of this flowchart is finished as it is.

As described above, according to the present embodiment, a high-intensity lamp that emits light that is weaker than strobe light is condensed by a condensing lens and is used. It can be used as auxiliary light. As a result, problems such as charging time and power consumption due to the use of a strobe device can be solved. Further, it is possible to correct the unevenness of the captured image caused by the condensing action of the condensing lens by digital image processing.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The embodiment will be described. The second embodiment uses a light emitting diode (LED) instead of the high brightness lamp.

The color of the LED when emitted is significantly different depending on the element used as the light-emitting body and its configuration, and the LED outputs almost monochromatic light. Therefore, in this embodiment, in order to obtain a color similar to that of sunlight, for example, as shown in FIG. 7, three LEDs that output lights of different colors of red, yellow, and blue are used.

In this embodiment, the lamp 13 shown in FIG.
It is configured by changing the part a as shown in FIG.
Of course, the number of LEDs is not limited to the above three.

FIG. 9A is a diagram showing a state in which LED light is projected onto the subject as auxiliary light to perform photographing. In addition,
As an example, consider a case where a night view is used as a background for shooting.

When the light from each LED is projected onto the subject, as shown in FIG.
It is called a "color range". ), It is possible to perform imaging with the same effect as sunlight by performing the same image processing as in the first embodiment. On the other hand, in the region where the three lights do not overlap, the reproducibility of one or two colors deteriorates, so that it is not possible to perform imaging with the same effect as sunlight. Therefore, the area is set as a black and white image as shown in FIG. 9C so that the dark part of the background and the black image are naturally continuous. In addition, no image processing is performed on a place where no LED light is projected.

As a result, for example, (a) of FIG.
In a scene where there is a night view light next to a person,
The colors of the person and the nightscape are properly reproduced to create a photograph with an atmosphere.

[0052] FIG. 9 (B) red LED _(C R), yellow LE
The reflection patterns of D (C _Y ) and blue LED (C _B ) are shown. This is an example of a reflection pattern when the light of the LED is irradiated toward a chart of uniform reflectance placed at a certain predetermined distance. Since the luminous efficiency and forward voltage characteristics of the LEDs of each color are different, the brightness of each LED is generally not uniform. Therefore, the camera according to the second embodiment also corrects this difference in brightness. Further, similarly to the first embodiment, the light intensity distribution is corrected according to the irradiation position. By performing such processing, the portion where the three colors overlap, as in (b) of FIG. 9C, can be an image as if the image was taken under the same conditions as sunlight.

FIG. 10 shows the light source of the auxiliary light irradiation device.
It is a flow chart explaining operation control of a camera when using a LED.

First, the object distance D is determined by the AFIC 6b.
Is measured (step S20). Next, the auxiliary light from each LED is projected onto the subject, and an image is taken by the image sensor 8 (step S21). Next, from the subject distance D to each L
The center positions C _B , C _R and C _Y of the ED projected light are calculated (step S22). As a result, the area where the three colors are overlapped by the known reflection pattern, that is, FIG.
The color range shown in (b) of (C) is detected (step S23). Next, the output of the pixel corresponding to this color range is corrected according to the characteristics of each LED to optimize the color (step S24).

As a result of the correction in step S24, CPU1
Determines whether or not the correction has been performed within the limit of the camera correction according to the present embodiment (step S25).
When it is determined that the correction cannot be performed, a warning is given (step S26), and the process proceeds to step S27. If it is determined that the correction can be performed, the process directly proceeds to step S27.

Next, the area of the black and white image in which the auxiliary light from the LED overlaps one or two colors is determined. That is, a region in which light overlaps only one color or two colors, that is, from the known pattern and the center positions C _R , C _Y , and C _B calculated in step S22, that is, (b) in FIG. 9C. The black-and-white range indicated by is detected (step S27), and the area is made a black-and-white image (step S28).

After the image correction is completed, the image is compressed (step S29), stored in the memory 13 (step S30), and displayed on the display device 14 (step S31). The operation of this flowchart ends.

As described above, according to the present embodiment, it is possible to take a picture using an LED, which has a longer life than the lamp and has a high luminous efficiency, as the auxiliary light. Further, the unevenness of the captured image that occurs when the LED is used as the auxiliary light can be corrected by digital image processing.

Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications and applications are possible within the scope of the present invention. Of course.

For example, in the present invention, in order to simplify the explanation, the autofocus technique used is one that can measure the distance only in the central portion of the screen, but in order to obtain more accurate color reproducibility,
A so-called multi-AF technique may be used to enable finer image processing such as color correction according to the position on the screen.

[0061]

As described in detail above, according to the present invention,
By condensing and using a lamp or LED that does not require high voltage charging, the light of the lamp or LED can be used in a wide distance range.

Further, depending on the image processing technology, a lamp or LE can be used.
It is possible to solve the problem of uneven light distribution and coloring when D is applied to a subject, and to provide a camera that is advantageous for shooting in a dark place with less power consumption and shooting time lag.

Further, since the charging circuit is not required, it is possible to contribute to downsizing of the camera, cost reduction, and shortening of release time lag.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration including an electronic circuit of a camera according to a first embodiment of the present invention.

FIG. 2A is a diagram showing an irradiation range of a light source,
FIG. 2B is a graph showing the relationship between the irradiation position on the photographing screen and the brightness of the light source.

FIG. 3 is a state diagram of an image of a subject before and after image correction and a distribution diagram of brightness on the image sensor 8 corresponding to the image of the subject.

FIG. 4 is a wavelength distribution diagram of sunlight and a wavelength distribution diagram of a lamp.

FIG. 5 is a flowchart showing a sequence of operation control of the camera of the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating a modified example of color correction.

FIG. 7 is a wavelength distribution diagram of sunlight and a wavelength distribution diagram of an LED.

FIG. 8 is a configuration diagram of an LED, which is an illumination light source of a camera according to a second embodiment of the present invention.

FIG. 9 is an explanatory diagram when an LED is used as an illumination light source.

FIG. 10 is a flowchart showing the order of operation control of the camera of the second embodiment of the present invention.

[Explanation of symbols]

1 CPU 2 ranging device 6 Shooting lens 7 Photography lens drive circuit (LD) 8 image sensor 9 Image processing circuit 10 memory 11 Display 12 Photometric device 13 Auxiliary light irradiation device 13a High-intensity lamp 13c condenser lens

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03B 13/36 H04N 9/04 B 15/02 G02B 7/11 BN H04N 9/04 G03B 3/00 A F term (reference) 2H002 DB14 DB17 DB24 DB25 EB00 EB09 FB22 FB32 FB40 GA32 GA33 HA05 HA06 JA07 2H011 AA01 BA14 DA07 2H051 AA01 BB20 EB00 5C022 AB15 5C065 AA03 BB01 BB41 CC01

Claims (4)

[Claims] 1. An irradiation means for irradiating a subject within a limited region within a photographing angle of view with auxiliary light for exposure, a distance measuring means for measuring a distance to the subject, and the distance measuring means. An image processing unit that performs image processing on an image captured according to the measured distance to the subject and the irradiation intensity distribution of auxiliary light in the irradiation unit. 2. The irradiating means has a light source for irradiating light having a wavelength distribution different from that of sunlight, and the image processing means performs color correction on the photographed image according to the wavelength distribution of the light source. The camera according to claim 1, wherein the camera is a camera. 3. The irradiating means is a plurality of LEDs having different wavelength distributions, and corrects a light quantity ratio and an irradiation intensity distribution of the plurality of LED lights when light from the plurality of LEDs is sequentially irradiated to a subject. The camera according to claim 1, wherein a single image is obtained. 4. A color correction area determining means for determining a color correction area of an image photographed using the light source according to an image pattern changed before and after irradiating a subject with auxiliary light from the light source. A camera characterized by.