JP2003319246A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera in which depth of field is easily confirmed. <P>SOLUTION: The digital camera finds depth (d) of field based upon a focal distance (f) of a photographing lens, a diaphragm value (F number) FNO of a diaphragm set by AF control and a distance (u) to an object detected by a range finding sensor. Then, the found depth (d) of field is displayed on a display part 46. On the display part 46, an indicator 60 representing the depth of field (focused range) and character information 62 representing a range of the depth of field with characters are displayed on the downside. Thus, a photographer easily grasps the focused range and the photographer can easily adjust the diaphragm, a shutter speed, and the like in accordance with an intention of photographing. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital camera, and more particularly to a digital camera capable of detecting a depth of field.

[0002]

2. Description of the Related Art In recent years, many digital cameras equipped with an image pickup device such as a CCD have been distributed. In such a digital camera, a subject image is formed on the light receiving surface of the CCD at the time of shooting, and converted into signal charges of an amount corresponding to the amount of incident light by each sensor of the CCD. Then, the signal charge accumulated in the CCD is read for each pixel and converted into image data, and this image data is recorded in a recording medium such as a memory card.

Further, conventionally, in order to effectively shoot various shooting scenes, a technique of shooting by controlling the depth of field has been proposed. For example, when a person is photographed, the depth of field is shallowed so that the person is in focus and the background is appropriately blurred, so that the person can be photographed.

In Japanese Patent Laid-Open No. 6-303491, it is determined whether or not a subject is a person, and when the subject is a person, control is performed so that the entire face of the person has a substantially depth of field. The technology is disclosed.

[0005]

The depth of field becomes shallower as the size of the image sensor increases. In addition, the depth of field becomes shallower as the distance to the subject becomes smaller. Therefore, when the subject is at a short distance, the focus range becomes narrow, and it may not be possible to photograph according to the photographer's intention. .

However, it is difficult to actually confirm the depth of field with the finder because the optical finder, which is the mainstream in digital cameras, is an optical system different from the lens for photographing.

Further, a digital camera is generally equipped with a display device such as a liquid crystal panel instead of or in addition to the finder, and is capable of displaying a through image of a subject photographed in real time. The photographer can confirm the shooting range by checking the through image displayed on this LCD panel.However, the aperture value when displaying the through image on the LCD panel and the aperture value when actually shooting are Are usually different, and again, it is difficult to check the depth of field.

The present invention has been made in view of such circumstances, and an object thereof is to provide a digital camera capable of easily confirming the depth of field.

[0009]

In order to achieve the above object, a digital camera according to a first aspect of the present invention comprises an image pickup device for picking up an image of a subject, a lens for forming an image of the subject on the image pickup device, Distance measuring means for detecting the distance to the subject, setting means for adjusting the aperture value of the aperture for adjusting the brightness of the lens, focal length of the lens, aperture value of the aperture, and the distance measuring means Calculating means for obtaining the depth of field based on the distance to the subject; notifying means for notifying the depth of field obtained by the calculating means;
It is characterized by having.

According to the present invention, the image of the subject is picked up by forming the image of the subject on the image pickup device by the lens. The distance measuring means detects a distance to a subject to be imaged.

The setting means determines the aperture value of the aperture for adjusting the brightness of the lens. The aperture value is determined, for example, from the brightness value of the subject obtained by photometry of the subject, and is set so that the subject has an optimum exposure amount.

The calculating means determines the depth of field based on the focal length of the lens, the aperture value of the diaphragm, and the distance to the object detected by the distance measuring means. This depth of field can be obtained by a predetermined arithmetic expression, for example.

The notification means notifies the depth of field obtained by the calculation means. The notification of the depth of field may be performed by displaying the depth of field or by outputting the depth of field by voice.

Further, as described in claim 2, the calculating means stores a look-up table showing a correspondence relationship between the focal length, the aperture value, the distance to the subject, and the depth of field. Including the focal length, the aperture value,
And a depth of field corresponding to the distance to the subject may be obtained from the correspondence.

As described above, by obtaining the depth of field from the predetermined correspondence, the depth of field can be obtained more quickly.

Further, as described in claim 3, the notifying means further comprises display means for displaying a picked-up image picked up by the image pickup device, and the notifying means sets the obtained depth of field as an image. It may be configured to generate and combine with the captured image to be displayed on the display unit.

As described above, an image representing the obtained depth of field is generated, and the generated image is combined with the captured image of the subject, that is, the captured image of the subject is overlaid on the captured image. By displaying the image showing the depth of field, the photographer can easily confirm the depth of field. Therefore, the photographer can easily adjust the aperture and the like according to the intention of photographing.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. The present embodiment is an application of the present invention to a digital camera.

FIG. 1 shows a block diagram of a digital camera according to an embodiment of the present invention. The taking optical system 12 of the camera 10 includes a taking lens 14 and a diaphragm 16. The taking lens 14 is composed of one or a plurality of lenses, and may be a lens having a single focal length (fixed focus) or a variable focal length such as a zoom lens or a telephoto / wide-angle bifocal switchable lens. Good.

The subject image formed on the light-receiving surface of the CCD 18 via the photographing optical system 12 is converted by each sensor into a signal charge of an amount corresponding to the amount of incident light. The signal charge accumulated in this way is CC applied from the CCD drive circuit 20.
It is read by the D drive pulse and is sequentially output from the CCD 18 as a voltage signal (analog image signal) corresponding to the signal charge.

The CCD 18 is provided with a shutter drain via a shutter gate. By driving the shutter gate with a shutter gate pulse, accumulated signal charges can be swept out to the shutter drain. That is, the CCD 18 has a so-called electronic shutter function that controls the accumulation time (shutter speed) of the charges accumulated in each sensor by the shutter gate pulse.

The signal read from the CCD 18 is a CD
Correlated double sampling (CDS) processing is performed in the S circuit 22, color separation processing is performed on each of the R, G, and B color signals, and the signal level of each color signal is adjusted (pre-white balance processing).

The image signal subjected to the predetermined analog signal processing is applied to the A / D converter 24 and converted into R, G, B digital signals by the A / D converter 24, and thereafter,
It is stored in the memory 26.

The timing signal generation circuit (TG) 28 is
CCD drive circuit 2 in response to a command from the CPU 30
0, an appropriate timing signal is given to the CDS circuit 22 and the A / D converter 24, and each circuit is driven in synchronization with the timing signal applied from the timing signal generation circuit 28.

The CPU 30 is a control unit that controls each circuit of the camera 10 in a centralized manner, and includes a gain adjusting circuit 34, a gamma correction circuit 36, a luminance / color difference signal processing circuit (referred to as YC processing circuit) 38 via a bus 32. The compression / expansion circuit 40, the card interface 44 of the memory card 42, the display driver 48 for driving the display unit 46, and the like are connected.

The CPU 30 controls the corresponding circuit block based on the input signal from the operation unit 50, and also performs the zooming operation of the photographing lens 14 and the automatic focus adjustment (AF).
It controls operations and controls automatic exposure adjustment (AE).

A distance measuring sensor 58 is connected to the CPU 30. Although the details will be described later, the CPU 30 calculates the depth of field based on the distance to the subject detected by the distance measuring sensor 58, the aperture value set by the AE control described later, and the focal length of the photographing lens 14. To do.
The calculated depth of field is displayed on the display unit 46.

The operation section 50 includes a release button for giving an instruction to start recording an image, a mode selection means for the camera, a zoom operation means, and various other input means. These input means have various forms such as switch buttons, dials, and sliding knobs, and there is also a mode in which a setting menu or a selection item is displayed on the screen of the touch panel or the liquid crystal monitor display unit and a desired item is selected with a cursor. . The operation unit 50 may be provided in the camera body, or may be configured as a remote control transmitter separated from the camera body.

The CPU 30 performs various calculations such as focus evaluation calculation and AE calculation based on the image signal output from the CCD 18, and based on the calculations, driving means for the taking lens 14 and the diaphragm 16 (for example, AF motor). Or iris motor) 52 to move the focus lens to the in-focus position and set the aperture 16 to an appropriate aperture value.

For AF control, for example, a contrast AF method is adopted in which the focus lens is moved so that the high frequency component of the G signal is maximized. In the AE control, the subject brightness (shooting EV) is obtained based on the integrated value obtained by integrating the R, G, and B signals for one frame, the aperture value and the shutter speed are determined based on this shooting EV, and the driving means 52 is operated. The aperture 16 is driven via the CCD and an electronic shutter is used to achieve the determined shutter speed.
The charge accumulation time of 18 charges is controlled. Therefore, only by directing the taking lens 14 of the camera 10 to the subject, optimum exposure adjustment is performed and focusing is automatically performed.

At the time of shooting and recording, the above-described photometric operation is repeated a plurality of times when the release button is "half pressed" to obtain an accurate shooting EV, and the aperture value and shutter speed at the time of shooting are finally determined based on this shooting EV. To decide. Then, when the release button is “fully pressed”, the aperture 16 is driven so as to reach the finally determined aperture value, and the charge accumulation time is controlled by the electronic shutter so as to achieve the determined shutter speed. In addition to the method of controlling AE and AF based on the image signal obtained from the CCD 18, a known photometric sensor or a distance measuring sensor including an AF light emitting / receiving sensor may be used.

Further, the camera 10 has a strobe light emitting device 54 and a light receiving element 56 for dimming, and the strobe light emitting device 54 is operated at a low brightness according to the operation of a strobe mode setting button included in the operation section 50. It is set to "low-brightness automatic flashing mode" that automatically flashes, "forced flashing mode" that flashes the strobe flashing device 54 regardless of subject brightness, or "flashing prohibition mode" that disables flashing of the strobe flashing device 54. It

The CPU 30 controls the charging of the main capacitor of the strobe light emitting device 54 and the discharge (light emission) timing to the light emitting tube (for example, a xenon tube) according to the strobe mode selected by the user, and the light receiving element 56. The stop of light emission is controlled based on the measurement result from.
The light receiving element 56 receives the reflected light from the subject illuminated by the strobe light and converts it into an electric signal according to the amount of received light. The signals of the light receiving element 56 are integrated by an integrating circuit (not shown), and when the integrated amount of received light reaches a predetermined appropriate amount of received light, the flash light emission is stopped.

The data output from the A / D converter 24 is stored in the memory 26 and added to the integrating circuit 60. The integrating circuit 60 divides the photographing screen into a plurality of blocks (for example, 64 blocks of 8 × 8), and performs an integrating operation of the G signal received for each block. In addition,
A luminance signal (Y signal) may be generated from the R, G, and B data, and the luminance signal may be integrated. The integrating circuit 60 can also be used as an AE arithmetic circuit. Information on the integrated value (calculation result) obtained by the integrating circuit 60 is stored in the CPU 3
Input to 0.

Based on the information from the integrating circuit 60, the CPU 30 uses a predetermined algorithm to evaluate the photographic screen evaluation value E.
Is calculated, and the gain adjustment circuit 34 is calculated by using the obtained evaluation value E.
The gain value (amplification factor) at is determined. The CPU 30 controls the gain amount in the gain adjusting circuit 34 according to the determined gain value.

The R, G, and B image data stored in the memory 26 is sent to the gain adjusting circuit 34, where it is amplified. The amplified image data is subjected to gamma correction processing in the gamma correction circuit 36 and then sent to the YC processing circuit 38 to convert the RGB data into a luminance signal (Y signal) and a color difference signal (Cr, Cb signal). To be converted.

The luminance / color difference signal (abbreviated as YC signal) generated in the YC processing circuit 38 is written back to the memory 26. The YC signal stored in the memory 26 is supplied to the display driver 48, and a signal of a predetermined system (for example,
It is converted to an NTSC color composite video signal and output to the display unit 46. A liquid crystal display or other display device capable of color display is used for the display unit 46. The display unit 46 may be of a YC signal input type or RGB signal input type, and a driver corresponding to a display device may be used.

Image data is periodically rewritten by the image signal output from the CCD 18, and a video signal generated from the image data is supplied to the display unit 46, whereby the image captured by the CCD 18 is a moving image in real time ( It is displayed on the display unit 46 as a live image) or as a substantially continuous image although not in real time.

The display unit 46 can be used as an electronic viewfinder, and the photographer can confirm the photographing field angle by the display image of the display unit 46 or an optical finder (not shown). In response to a predetermined recording instruction (imaging start instruction) operation such as a release button pressing operation, the capture of image data for recording is started.

When the photographer inputs a photographing / recording instruction from the operation section 50, the CPU 30 causes the compression / expansion circuit 4 to operate as necessary.
The command is sent to 0, whereby the compression / expansion circuit 40 compresses the YC data on the memory 26 in accordance with a predetermined format such as JPEG. The compressed image data is recorded in the memory card 42 via the card interface 44.

When the mode for recording uncompressed image data (non-compression mode) is selected, the compression processing by the compression / expansion circuit 40 is not performed, and the image data remains uncompressed in the memory card 42. Recorded in.

The camera 10 of the present embodiment uses the memory card 42 as a means for storing image data. Specifically, for example, a recording medium such as smart media is applied. The form of the recording medium is not limited to the above, and various forms such as a PC card, a micro drive, a multimedia card (MMC), a magnetic disk, an optical disk, a magneto-optical disk, and a memory stick can be used. Appropriate signal processing means and interface are applied.

In the reproduction mode, the memory card 42
The image data read from is expanded by the compression / expansion circuit 40 and output to the display unit 46 via the display driver 48.

Next, the calculation of the depth of field according to this embodiment will be described.

The CPU 30 is based on the focal length f of the taking lens 14, the aperture value (F number) F _{NO of} the aperture 16 optimally set by the AE control, and the distance u to the object detected by the distance measuring sensor 58. Find the depth of field d.
Specifically, the depth of field d can be calculated by the following equation.

[0046]

[Equation 1]

However, d1 is the depth of field at the far point,
d2 is the depth of field at the near point, u is the distance from the front principal point to the subject, u1 is the distance from the front principal point to the far point, u
2 is the distance from the front principal point to the near point, and δ is the permissible circle of confusion diameter. The permissible circle of confusion diameter δ is set to n times the pixel pitch of the CCD 18.

The depth of field d is calculated in this manner, and the calculated depth of field d is displayed on the display unit 46.

FIG. 2 is a functional block diagram functionally showing the configuration of the camera 10.

As shown in FIG. 2, the camera 10 includes a calculating means 70, a setting means 72, a distance measuring means 74, and an informing means 7.
6 is provided. The notification unit 76 includes a generation unit 78, a combination unit 80, and a display unit 82.

The calculating means 70 has a focal length f represented by the focal length information 86 of the taking lens 14, an aperture value F _{NO of the} diaphragm 16 set by the setting means, and a distance to the object detected by the distance measuring means 74. Based on u, the depth of field d is obtained and output to the generation means 78.

The generating means 78 generates an image representing the depth of field d and outputs it to the synthesizing means 80. The synthesizing means 80 is
The captured image 88 captured by the CCD 18 and the image representing the depth of field generated by the generation unit 78 are combined and output to the display unit 82. Thus, the display unit 82 displays an image in which the image representing the depth of field is superimposed on the captured image of the subject. Thereby, the photographer can easily confirm the depth of field.

Further, for example, the distance measuring means 74 is realized by the distance measuring sensor 58, the calculating means 70, the setting means 72, and a part of the notifying means are realized by the CPU 30, and the synthesizing means 80 and the display means 82 are display portions. It is realized by 46.

The CCD 18 corresponds to the image pickup device of the present invention, the taking lens 14 corresponds to the lens of the present invention, the distance measuring means 74 corresponds to the distance measuring means of the present invention, and the setting means 72.
Corresponds to the setting means of the present invention, the arithmetic means 70 corresponds to the arithmetic means of the present invention, and the notification means 76 corresponds to the notification means of the present invention.

Next, as an operation of this embodiment, the CPU
The control routine executed in 30 will be described with reference to the flowchart shown in FIG.

First, in step 100, it is determined whether or not the release button has been half-depressed. If the release button has not been half pressed, the determination in step 100 is denied, and the process waits until the release button is half pressed.

On the other hand, if the release button is pressed halfway, the determination in step 100 is affirmative and step 10
Move to 2.

In step 102, distance measurement processing is performed. That is, the distance measuring sensor 58 detects the distance to the subject, and takes in the detected distance to the subject.

In the next step 104, photometric processing is performed. That is, as described above, one frame of R, G,
Subject brightness (shooting E
V) is calculated. This photometric operation is repeated a plurality of times, and accurate photographing EV is required.

At the next step 106, AE control and A
F control is performed. That is, as described above, the aperture value and the shutter speed are determined based on the obtained shooting EV,
The diaphragm 16 is driven via the drive means 52, and the charge accumulation time of the CCD 18 is controlled by the electronic shutter so that the shutter speed is determined. As a result, optimum exposure adjustment is performed.

Further, the CPU 30 performs various calculations such as focus evaluation calculation and AE calculation based on the image signal output from the CCD 18, and controls the driving means 52 of the taking lens 14 and the diaphragm 16 based on the calculations. Then, the focus lens is moved to the in-focus position, and the diaphragm 16 is set to a proper diaphragm value (F number F _NO ). The AF control is performed by, for example, a contrast AF method in which the focus lens is moved so that the high frequency component of the G signal becomes maximum.

Then, in the next step 106, the depth of field is calculated. That is, the set focal length f of the taking lens 14 and the aperture value F set by the AE control
_NO , distance u to the subject detected by the distance measuring sensor 58
From the above, the depth of field d is calculated by the above equation (3).

In the next step 108, step 106
The depth of field obtained in step 3 is displayed on the display unit 46. Specifically, an image representing the calculated depth of field is generated, the generated image is combined with a captured image of a subject to be displayed on the display unit 46, and the combined image is displayed on the display unit 46. Let That is, the image representing the depth of field is displayed on the captured image of the subject to be displayed on the display unit 46.

For example, as shown in FIGS. 4A and 4B, the depth of field, that is, the indicator 60 indicating the focused range and the range of the depth of field are displayed on the lower side of the display unit 46. The image including the character information 62 represented by is superimposed and displayed on the captured image of the subject. In addition, FIG.
In the example of (B), the black-painted portion of the indicator 60 represents the depth of field, FIG. 4 (A) is an example of a macro image of a flower, and FIG. 4 (B) is a landscape. This is an example of the case where the image was taken at a wide angle.

As described above, in the present embodiment, the depth of field is displayed on the display unit 46 by the indicator and the characters, so that the photographer can easily grasp the focus range. As a result, the photographer can easily adjust the aperture and the shutter speed according to the intention of photographing. This is particularly effective when the size of the CCD 18 is relatively large, the subject is in a short distance as in the example of FIG. 4A, and the focus range is narrow.

Next, at step 112, it is judged if the release button has been fully pressed. Then, when the release button is fully pressed, the determination in step 112 is affirmed, and the process proceeds to step 114.

In step 114, an image pickup process is performed,
The image data is recorded in the memory card 42.

On the other hand, if the release button has not been fully pressed, the determination at step 112 is denied and the routine proceeds to step 116.

In step 116, it is determined whether or not the half press of the release button has been released. Then, if the half-press of the release button has not been released, the determination in step 116 is negative, the process proceeds to step 112, and it is determined whether or not the release button has been fully pressed as in the above.

On the other hand, when the release button is half-pushed, the determination at step 116 is affirmative, and the routine proceeds to step 100, where it waits until the release button is half-pushed again. When the release button is pressed halfway again, the same processing as described above is performed, and the depth of field is calculated and displayed on the display unit 46.

With this, every time the release button is pressed halfway, the depth of field d is calculated based on the focal length f of the taking lens 14, the aperture value F _NO , and the distance u to the subject at that time, and the display unit 46 is displayed.

As described above, in the present embodiment, since the depth of field is obtained and displayed on the display unit 46 with the indicator and the characters, the photographer can easily grasp the focus range. As a result, the photographer can easily adjust the aperture and shutter speed according to the intention of the photograph, and can effectively assist the photographer in photographing.

In this embodiment, the case where the depth of field d is calculated by the above equation (3) has been described.
The present invention is not limited to this, and a look-up table representing the correspondence relationship between the focal length f, the aperture value F _NO , the distance u to the subject, and the depth of field d is provided in advance, and the look-up table is used to calculate the focal length. f, the aperture value F _NO , and the depth of field d corresponding to the distance u to the subject may be obtained. Thereby, the depth of field can be quickly obtained. The lookup table is stored in the memory 2
It may be provided within 6, or may be provided separately.

Further, in the present embodiment, the case has been described in which the obtained depth of field is displayed and displayed on the display unit 46, but the present invention is not limited to this, and the depth of field is displayed in the viewfinder of the camera 10. You may do it. That is, it may be configured such that the photographer can confirm the depth of field when the finder is removed. Further, instead of the display, or together with the display, the depth of field may be notified by voice.

[0075]

As described above, according to the present invention, an image pickup device for picking up an image of a subject, a lens for forming an image of the subject on the image pickup device, and a distance measuring means for detecting the distance to the subject. And a diaphragm for adjusting the brightness of the lens, and a calculating means for obtaining the depth of field based on the focal length of the lens, the aperture value of the diaphragm, and the distance to the subject detected by the distance measuring means. Since the notification means for notifying the depth of field calculated by the calculation means is provided, there is an effect that the depth of field can be easily confirmed.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of a digital camera according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of the digital camera according to the embodiment of the present invention.

FIG. 3 is a flowchart of a control routine executed by a CPU.

FIG. 4 is an image diagram showing a display example of depth of field.

[Explanation of symbols]

10 cameras 12 Shooting optical system 14 Shooting lens 16 aperture 18 CCD 26 memory 30 CPU 42 memory card 46 Display 50 Operation part 58 distance measuring sensor

Claims (3)

[Claims] 1. An image pickup device for picking up an image of a subject, a lens for forming an image of the subject on the image pickup device, a distance measuring unit for detecting a distance to the subject, and a diaphragm for adjusting the brightness of the lens. Setting means for determining an aperture value, a calculation means for obtaining a depth of field based on a focal length of the lens, an aperture value of the aperture, and a distance to the subject detected by the distance measuring means, and the calculation means A digital camera comprising: a notifying unit for notifying the depth of field obtained by. 2. The calculation means includes a look-up table showing a correspondence relationship between the focal length, the aperture value, the distance to the subject, and the depth of field, the focal length, the aperture value. , And the depth of field corresponding to the distance to the subject is obtained from the correspondence relationship. 3. The notifying means further comprises a display means for displaying a picked-up image picked up by the image pickup element, and the notifying means generates the obtained depth of field as an image and displays it on the display means. The digital camera according to claim 1 or 2, wherein the digital camera is combined with the captured image to be captured.