JP5262825B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus such as an electronic camera or a digital camera having an autofocus function for irradiating a photographing subject with auxiliary light and detecting a focus adjustment state.

  Conventionally, a technology has been used to improve the accuracy of autofocus processing that automatically performs focus detection by irradiating a shooting subject with auxiliary light (illumination light) when the surroundings are dark or the luminance of the shooting subject is low. (For example, refer to Patent Document 1).

JP 2004-15187 A

When performing close-up shooting of a shooting subject using an electronic camera, the shooting may be performed by approaching the shooting subject beyond the shortest shooting distance of the lens.
In this case, in the state where there is no imaging instruction, the resolution of the through image captured by the imaging element through the lens is low, so that the image is viewed and imaged as if it was captured clearly.
However, if shooting is performed at a distance shorter than the shortest shooting distance, the captured image is blurred due to the out-of-focus state.

In other words, when the subject is out of focus due to a short shooting distance, the autofocus display is within the normal shooting distance range even though it indicates that the subject is out of focus, but the image is formed on the image sensor. The image data of the subject is not in focus and the subject is not in focus because it is out of focus, or the subject is not in focus because the distance between the subject and the electronic camera is shorter than the shortest shooting distance. It is not notified about the distinction.
Since there is no notification, the user does not know that he is trying to take an image at a distance closer than the shortest shooting distance, and a blurred image which is out of focus for close-up shooting is taken.
In addition, when the subject is not in focus, the electronic camera normally fixes the focus position at a preset position corresponding to when the subject is out of focus. When a subject to be photographed is present at a position closer than the shortest photographing distance, the out-focus amount increases, and the photographed image is blurred.

  The present invention has been made in view of such circumstances, and when the distance between the imaging device and the photographic subject is closer than the shortest shooting distance, it is out of focus because the photographic subject is approached beyond the shortest shooting distance. The purpose of this is to reduce the number of photographs that are out of focus during close-up photography and fail to capture.

  The imaging apparatus of the present invention images an imaging subject via an imaging optical system and outputs an image signal, an auxiliary light source that emits auxiliary light for autofocusing the imaging subject, and the auxiliary Difference in gradation level for each pixel in the first image signal obtained by imaging the photographic subject in the state where light is irradiated and the second image signal obtained by imaging the photographic subject in the state where the auxiliary light is not applied. A difference calculating unit for obtaining a difference gradation degree, and determining, based on the difference gradation degree, whether or not the auxiliary light is reflected in a pixel block obtained by dividing the image by a predetermined number of pixels, for each pixel block, A distribution forming unit for obtaining a distribution of the reflection of the auxiliary light in the image based on the determination, and a comparison distribution for storing the distribution of the reflection of the auxiliary light obtained in advance for each distance from the subject as a comparison distribution A distance estimation unit that compares the distribution output from the storage unit, the distribution output unit, and the comparison distribution, and obtains a distance from the photographing subject, and the distance obtained by the distance estimation unit is the photographing optical system A shooting availability determination unit that determines whether or not the shortest possible shooting distance is less than, and a shooting availability notification unit that notifies the photographer that shooting is not possible when the determination result of the shooting availability determination unit is less than the shortest possible shooting distance And have.

  As described above, according to the present invention, the distance between the imaging device and the shooting subject is detected based on the intensity distribution of the reflected light from the shooting subject with respect to the auxiliary light, and the distance between the imaging device and the shooting subject is the shortest shooting distance. If it is closer, it is out of focus because the distance from the shooting subject is close to notify the user that it is out of focus because it is approaching the subject beyond the minimum shooting distance of the reflected light of the auxiliary light. Can be recognized by the user, and it is possible to reduce the number of photographs that are out of focus when the close-up shooting is performed and the imaging fails.

It is a block diagram which shows the structural example of the imaging device by one Embodiment of this invention. It is a conceptual diagram which shows irradiation to the imaging | photography subject of the auxiliary light explaining the operation | movement of the auxiliary light source part. It is a conceptual diagram which shows the relationship between image data, the pixel in this image data, and a pixel block. It is a conceptual diagram explaining the creation process of the reflection distribution in image data. 7 is a conceptual diagram illustrating an example of a comparative reflection distribution stored in a comparative distribution storage unit 7. FIG. 7 is a conceptual diagram illustrating an example of a comparative reflection distribution stored in a comparative distribution storage unit 7. FIG. 7 is a conceptual diagram illustrating an example of a comparative reflection distribution stored in a comparative distribution storage unit 7. FIG. It is a flowchart explaining the operation | movement of the imaging | photography process of the electronic camera by this embodiment.

Hereinafter, an imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration example of an electronic camera as an imaging apparatus according to the embodiment.
In this figure, the electronic camera of this embodiment includes an imaging unit 1, a difference calculation unit 2, a histogram unit 3, a distribution formation unit 4, an auxiliary light source unit 5, a storage unit 6, a comparative distribution storage unit 7, a distance estimation unit 8, A photographing availability determination unit 9, a display unit 10, and a control unit 11 are included.
The imaging unit 1 includes a photographing lens having a zoom lens and a focus lens, and an imaging element configured by a CCD (Charge Coupled Device) or the like. The imaging unit 1 also has a zoom mechanism control unit, and drives the zoom lens to move back and forth in the optical axis direction to control zoom of the photographing lens. Here, the photographing lens, the zoom mechanism control unit, and the focus mechanism control unit constitute a photographing optical system. The imaging unit 1 also has a focus mechanism control unit that performs autofocus, and drives the focus lens forward and backward along the optical axis to adjust the focus of the image of the subject to be imaged on the imaging surface of the image sensor. I do. The imaging element captures an image of a photographic subject formed on the imaging surface via a photographic lens and outputs it as image data.
The storage unit 6 accumulates captured image data, and includes, for example, a removable memory card.

When an instruction signal is input from a power switch, a zoom switch, a setting switch, a half-press switch, or a release switch (full-press switch) (not shown), the control unit 11 corresponds to each instruction signal and controls each part of the electronic camera. Take control.
Further, the control unit 11 displays the image data output from the imaging unit 1 on the display unit 10 formed from a liquid crystal display panel.
When storing image data in the storage unit 6, the control unit 11 stores the image data in the image data recording area of the storage unit 6 after format conversion.
Here, the control unit 11 stores both the image data for estimating the shooting distance and the captured image data in the storage unit 6.

  As shown in FIG. 2A, the auxiliary light source unit 5 is disposed in the vicinity of the photographing lens of the imaging unit 1, has an LED (Light Emitting Diode) as a light source, and as shown in FIG. In addition, the LED is caused to emit light during shooting to illuminate the shooting subject as auxiliary light, and the contrast of the shooting subject image formed on the imaging surface of the image sensor is improved to assist autofocus.

The difference calculation unit 2 calculates, for each pixel of the image data stored in the storage unit 6, a difference gradation that is a difference between the gradation before irradiation of the auxiliary light and the gradation of the state where the auxiliary light is irradiated. It is obtained and stored in the storage unit 6 corresponding to each pixel position.
In the present embodiment, all pixels on the imaging surface (that is, image data) of the imaging device are divided into pixel blocks grouped for a plurality of adjacent pixels as shown in FIG.
The distribution forming unit 4 determines, for each pixel block, whether or not auxiliary light is reflected in a pixel block obtained by dividing the image by a predetermined number of pixels based on the difference gradation, and based on this determination result, reflects the auxiliary light in the image. The reflected light distribution which is the distribution of is obtained.

  In the present embodiment, the distribution forming unit 4 detects the presence / absence of reflected light by the auxiliary light in the area of each pixel block from the histogram for each difference gradation degree in each pixel block, and at the position of each pixel block in the image data, If it is determined that there is reflection, a flag is set to form a reflected light distribution of the image data as shown in FIG. As the reflected light distribution, the distribution forming unit 4 writes “1” at the position of the pixel block where the flag is set, and writes “0” at the position of the pixel block where the flag is not set.

  The histogram unit 3 classifies the pixels included in each of the pixel blocks for each difference gradation degree to be used by the distribution forming unit 4 for distribution formation, and obtains a histogram of the number of pixels with respect to the difference gradation degree.

  Further, the distribution forming unit 4 does not use a histogram, but calculates an average value of the difference gradation of all the pixels in each pixel block, and sets the average value as the block difference gradation of each pixel block. Creates a reflected light distribution by setting a flag as if there was reflection at a pixel block position where the intensity exceeded a preset threshold, while avoiding setting a flag at a pixel block position where the block differential gradation was less than the threshold. You may do it.

  The comparative distribution storage unit 7 stores the reflected light distribution obtained in advance for each product of the electronic camera as the comparative reflected light distribution for each set distance. For example, FIG. 5 is 5 cm, FIG. 6 is 10 cm, and FIG. Also, the correspondence between this distance and the comparative reflected light distribution is provided in units of zoom levels. The comparative reflected light distribution is determined for each distance from the shooting subject (preliminary) between a distance range close to the shooting subject with respect to the shortest shooting distance of the shooting lens and a distance range far from the shooting subject with respect to the shortest shooting distance. The distance is set according to the set step size). Thus, since the distance is determined using the comparative reflected light distribution for each set distance at each zoom level, that is, at each stage of zooming, the determination accuracy can be improved. In addition, the step size is within a predetermined range centered on the shortest shooting distance, and the step size is made shorter (outside this range) to improve the accuracy of distance determination. May be.

In addition, as the distance from the photographic subject increases, the intensity of the reflected light from the photographic subject decreases, and the flag in the comparative reflection distribution decreases. Sex will be detected.
Therefore, after this distance (maximum comparison distance), there is one comparative reflection distribution, and the shooting distance is estimated as the maximum comparison distance regardless of the actual distance. Naturally, this maximum comparison distance is set to a value sufficiently larger than the shortest shooting distance (a distance away from the shooting subject from the shortest shooting distance).

The distance estimation unit 8 reads the comparative reflected light distribution in order from the comparative distribution storage unit 7, for example, in the order of the distance close to the shortest shooting distance, and sequentially compares the comparative reflected light distribution and the reflected light distribution obtained by the distribution forming unit 4. Are compared to obtain a comparative reflection distribution having the highest similarity to the reflection distribution, and a distance corresponding to the comparative reflection distribution is detected as a shooting distance between the shooting subject and the electronic camera.
Here, in the reflected light distribution and the comparative reflected light distribution, the distance estimation unit 8 matches the flag state (“1” or “0”) at the corresponding position for each pixel block corresponding to the position. The comparison reflected light distribution with the largest number of matching pixel blocks is detected as having a high similarity with the reflected light distribution obtained by the distribution forming unit 4 and matching.

  The photographing availability determination unit 9 compares the photographing distance obtained by the distance estimating unit 8 with the shortest photographing distance corresponding to the zoom level, detects whether the photographing distance is less than the shortest photographing distance, and the photographing distance is The fact that the distance is less than the shortest shooting distance is displayed on the display unit via the control unit 11, and the user is notified that the subject is out of focus because the shooting distance is short.

Next, with reference to FIG. 1 and FIG. 8, the operation of the determination process for determining whether or not the distance between the electronic camera and the subject to be photographed is closer than the shortest photographing distance will be described. FIG. 8 is a flowchart showing an operation example of the determination process of the electronic camera in FIG.
The user turns on the power switch of the electronic camera (step S1) and activates the electronic camera in order to take an image of the photographic subject with the electronic camera.
Then, the user changes the operation mode of the electronic camera to a photographing mode for photographing a photographing subject using the setting switch (step S2). Thereby, the control unit 11 starts control of each unit of the electronic camera, and displays the image data of the through image from the imaging unit 1 on the display unit 10. Further, in the following description, it is assumed that the user selects an autofocus mode with a setting switch and takes a picture of a shooting subject.

The control unit 11 detects whether or not the user half-presses the shutter to perform autofocus, that is, whether or not the half-press switch is on, and determines whether or not to perform focus adjustment (step S3). .
At this time, if the half-press switch is in the on state, the control unit 11 proceeds to step S4. If the half-press switch is in the off state, the control unit 11 repeats the process in step S3.

When executing the focus adjustment, the control unit 11 writes the through image when the half-press switch is turned on as the image data A to the storage unit 6 and emits the LED to the auxiliary light source unit 5 to emit light. Output a signal.
When the light emission control signal is input, the auxiliary light source unit 5 causes the LED to emit light.
Then, the control unit 11 writes the through image after the auxiliary light source unit 5 emits the LED as the image data B to the storage unit 6 and ends the acquisition of the image data for distance estimation (step S4).

  After the acquisition of the image data for distance estimation is completed, the control unit 11 drives the focus mechanism control unit of the imaging unit 1, reads the image data of the photographic subject imaged on the imaging device of the imaging unit 1, and focuses As the lens advances and retreats, autofocus processing is performed so that the contrast of the photographic subject in the image data is maximized (step S5).

  Then, the difference calculation unit 2 obtains the difference between the image data B and the image data A stored in the storage unit 6 and the gradation of the pixel at the corresponding position of each image data, and obtains the difference gradation degree. . At this time, it corresponds to the color of light emitted from the LED of the auxiliary light source unit 5. For example, when the LED is red, the gradation of the pixels of the image data B and the image data A is R (red) in RGB. The difference gradation is obtained from the gradation and is output to the histogram unit 3.

When the difference gradation degree of each pixel of the image data is calculated, the histogram unit 3 calculates a histogram by adding the number of pixels for each difference gradation degree for each pixel block, and calculates the pixel block of each pixel block of the calculated image data. The histogram is output to the distribution forming unit 4.
When the histogram is calculated, the distribution forming unit 4 determines whether or not the reflected light from the photographing subject of the auxiliary light is incident on each unit block based on the histogram. A process of setting the flag at the position of the corresponding pixel block is performed, a reflected light distribution is formed, and output to the distance estimation unit 8 (step S6).

The distribution forming unit 4 performs the following processing to determine the presence or absence of reflected light from the photographic subject in each pixel block using the histogram.
For example, the distribution forming unit 4 uses the difference gradation having the maximum number of pixels of the histogram in the pixel block as the difference gradation of the pixel block, and when this difference gradation exceeds a preset threshold, there is reflected light. Flag as you do.
Further, as another method, the distribution forming unit 4 takes an average value of the number of pixels of the difference gradation that is not 0 in the pixel block histogram, and calculates the difference gradation of the number of pixels close to the average value of the pixel block. A difference gradation degree may be set, and when the difference gradation degree exceeds a preset threshold value, a flag may be set to indicate that reflected light exists.
Furthermore, as another method, the distribution forming unit 4 sets the difference gradation of the intermediate number of pixels between the maximum number of pixels in the histogram of the pixel block and the minimum number of pixels other than 0 as the difference gradation of the pixel block. When this difference gradation degree exceeds a preset threshold value, a flag may be set up so that reflected light is present.

  When the reflected light distribution is obtained, the distance estimation unit 8 sequentially reads out the comparison reflection distribution stored corresponding to each distance stored in the comparison distribution storage unit 7, and reads out the read comparison reflection distribution and distribution forming unit. 4 is compared to extract a comparative reflection distribution with high similarity, and the distance corresponding to the extracted comparative reflection distribution is output to the imaging availability determination unit 9 as an imaging distance (step S7).

When the shooting distance is input, the shooting availability determination unit 9 compares the shortest shooting distance set corresponding to the zoom level at that time with the input shooting distance, and this shooting distance is the shortest shooting distance. It is determined whether the distance is less than the distance (step S8).
At this time, if the shooting distance is less than the shortest shooting distance, the shooting availability determination unit 9 advances the process to step S9. On the other hand, if the shooting distance is equal to or longer than the shortest shooting distance, the process advances to step S10.

  When the shooting distance is less than the shortest shooting distance, the shooting possibility determination unit 9 is out of focus because the distance between the shooting subject and the electronic camera is shorter than the shortest shooting distance to the display unit 10 via the control unit 11. An image or character indicating that it is present is displayed (or by a sound such as a buzzer sound), and the user is informed that the distance between the photographing subject and the electronic camera is shorter than the shortest photographing distance and the photograph is blurred when the image is taken (step) S9). The user performs an operation such as shooting or changing the shooting distance by this display.

  On the other hand, when the shooting distance is less than the shortest shooting distance, the shooting availability determination unit 9 focuses the display unit 10 via the control unit 11 because the distance between the shooting subject and the electronic camera is longer than the shortest shooting distance. An image or characters indicating that a sharp picture can be taken is displayed (or by a sound such as a buzzer), and the distance between the subject and the electronic camera is longer than the shortest shooting distance to the user. Notify that photos are not blurred. When the user who sees this notification presses the shutter completely, the release switch is turned on, and when the control unit 11 detects that the release switch is turned on by an on signal from the release switch, The image data imaged on the imaging surface is read, image identification information for identifying the image data is added, and the image data recording area of the storage unit 6 is recorded together with the date / time information of the image corresponding to the image identification information. The stored photographing process is performed (step S10).

Next, the control unit 11 determines whether or not the power switch is in an off state (step S11). If the power switch is in an off state, the process of each unit is terminated, while the power switch is in an off state. If not, the process returns to step S3 to continue the photographing process.
As described above, in the present embodiment, the auxiliary light source unit 5 emits auxiliary light, and the distribution forming unit 4 obtains a reflected light distribution that is an intensity distribution of reflected light from the photographing subject with respect to the auxiliary light, and estimates the distance. The unit 8 extracts a comparative reflected light distribution having a high similarity to the reflected light distribution from the comparative reflected light distribution for each predetermined distance.
According to this embodiment, the distance corresponding to the comparative reflected light distribution extracted by the distance estimation unit 8 is set as the shooting distance between the electronic camera and the shooting subject, and the shooting availability determination unit 9 has the shortest shooting distance. When it is closer than the shooting distance, the user is notified that the subject is too close to the shooting subject and is out of focus, so the user can recognize that the subject is out of focus because the distance from the shooting subject is short, and close-up shooting is performed. At this time, it is possible to reduce photographs that are out of focus and fail to be captured.

  1 is recorded in a computer-readable recording medium, and the program recorded in the recording medium is read into a computer system and executed, thereby executing close-up shooting support processing. May be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Image pick-up part 2 ... Difference calculation part 3 ... Histogram part 4 ... Distribution formation part 5 ... Auxiliary light source part 6 ... Memory | storage part 7 ... Comparison distribution memory | storage part 8 ... Distance estimation part 9 ... Shooting possibility determination part 10 ... Display part 11 ... Control unit

Claims (7)

An imaging unit that captures an image of a photographic subject via an imaging optical system and outputs an image signal;
An auxiliary light source that emits auxiliary light for performing autofocus on the subject to be photographed;
The gradation level for each pixel in the first image signal obtained by imaging the photographic subject in the state where the auxiliary light is illuminated and the second image signal obtained by imaging the photographic subject in the state where the auxiliary light is not illuminated. A difference calculation unit for obtaining a difference gradation which is a difference between
Based on the difference gradation, the presence or absence of reflection of the auxiliary light in a pixel block obtained by dividing the image by a predetermined number of pixels is determined for each pixel block, and reflection of the auxiliary light in the image is performed based on the determination. A distribution forming unit for obtaining the distribution of
A comparison distribution storage unit that stores, as a comparison distribution, the reflection distribution of the auxiliary light obtained in advance for each distance from the subject;
A distance estimation unit that compares the distribution output from the distribution forming unit with the comparison distribution to obtain a distance from the photographic subject;
A shooting availability determination unit that determines whether the distance obtained by the distance estimation unit is less than the shortest possible shooting distance of the imaging optical system;
An imaging apparatus comprising: a shooting availability notification unit that notifies the photographer that shooting is not possible when the determination result of the shooting availability determination unit is less than the shortest possible shooting distance.   2. The imaging apparatus according to claim 1, wherein the comparison distribution is set such that a step size of the distance within a predetermined distance range including the shortest photographic distance is shorter than a distance step outside the distance range. . The photographing optical system includes a zoom optical system whose focal length can be changed,
The imaging apparatus according to claim 1, wherein the comparison distribution is set for each zoom position of the zoom optical system.   4. The histogram section according to claim 1, further comprising a histogram section for obtaining a histogram of the number of pixels for each difference gradation degree in the pixel block based on the difference gradation degree obtained by the difference calculation section. The imaging device according to any one of the above.   When the distribution forming unit sets the difference gradation degree of the maximum number of pixels of the histogram in the pixel block as the difference gradation degree of the pixel block, and the difference gradation degree exceeds a preset threshold, there is reflected light. The imaging apparatus according to claim 4, wherein the determination is performed.   The distribution forming unit takes an average value of the number of pixels of the difference gradation that is not 0 in the histogram of the pixel block, and sets the difference gradation of the number of pixels close to the average value as the difference gradation of the pixel block. The imaging apparatus according to claim 4, wherein when the difference gradation level exceeds a preset threshold value, a flag is set as reflected light is present.   The distribution forming unit sets the difference gradation of the pixel block having the intermediate value between the maximum number of pixels and the minimum number of non-zero pixels in the histogram of the pixel block as the difference gradation of the pixel block, and the difference gradation The imaging device according to claim 4, wherein when the value exceeds a preset threshold value, a flag is set as reflected light is present.

Images