JP2003270521A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a camera which can more rapidly perform focusing operation in spite of simple constitution. <P>SOLUTION: A histogram is formed in accordance with the information relating to the lens position stored in an EEPROM20 and if a proximity range R estimated to be close to the lens position in next photographing is estimated, the possibility that focusing can be achieved is enhanced simply by moving a focusing lens of a lens unit 1 thereto. If a digital still camera 100 has a function to search the interior of the proximity range R, the more rapid focusing operation than that in searching the same from a predetermined initial position is made possible by, for example, searching the interior of the proximity range R. <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, and more particularly to a camera that can perform an autofocus operation quickly.

[0002]

2. Description of the Related Art There is known a camera having an autofocus function capable of focusing a lens on a subject. Here, in the auto focus, the infrared light or the like is emitted to the subject, the infrared light or the like reflected from the subject is received, and the incident angle is converted into a distance or the phase difference is detected to detect the distance. The so-called active AF method (often used in silver-salt cameras) that measures the image and the optical image that has passed through the lens by an image sensor such as CCD, and image processing the corresponding image data A so-called image plane AF method (often used in electronic cameras) for determining the focus position is known.

[0003]

[Means for Solving the Problems] The active AF method is
In order to be able to directly measure the subject distance using infrared light,
On the other hand, it has the advantage that the focusing operation can be performed quickly, but when infrared light or the like is radiated on a subject (for example, the background) different from the main subject, a focus position different from the photographer's intention is determined. There is a fear that it will end up. On the other hand, the image-plane AF method actually captures an image each time while moving the lens a small distance in the optical axis direction from the initial position and searches for the most focused position. Although the focusing accuracy is high, there is a problem that it takes time from the start to the end of focusing.

To solve such a problem, for example, a camera is provided with both an active AF method and an image plane AF method. First, a rough focus position is determined by the active AF method, and then the image plane AF method is used for accurate focusing. By finding the focal position,
It may be possible to achieve both quickness and accuracy of focusing.
However, the provision of a plurality of autofocus mechanisms, which should be sufficient if one is originally provided, causes an increase in cost, and also complicates and enlarges the configuration of the camera.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a camera capable of performing a focusing operation more quickly while having a simple structure.

[0006]

A camera according to a first aspect of the present invention is based on storage means for storing information on a lens position obtained for each photographing, and information on the lens position stored in the storage means. , And the driving means for moving the lens to the proximity range estimated by the estimation means, and therefore, for example, the stored lens position. If the proximity range that is estimated to be close to the lens position in the next shooting can be estimated by statistically processing the information regarding, the possibility that focus can be achieved only by moving the lens there is increased. Further, if the camera has a function of searching a focus position based on an image captured while moving the lens, for example, if searching in the proximity range, the camera searches from a predetermined initial position. The possibility that the focusing operation can be performed more quickly is increased. However, if the proximity range can be accurately estimated in a narrow range (including one point), even if the proximity range is slightly deviated from the actual in-focus position, there is a high possibility that the proximity range will fall within the depth of field. In such a case, shooting can be performed without performing the distance measuring operation.

The camera of the second aspect of the present invention is a camera having a function of searching a focus position based on an image captured while moving the lens, and stores information on the lens position obtained at each photographing. A storage unit, an estimation unit that estimates a lens position (which may be a range instead of a single point) in the next shooting based on information about the lens position stored in the storage unit, and the lens estimated by the estimation unit. Predetermined distance to the position (distance = 0
Drive means for moving the lens, and a search means for searching a focusing position in a direction in which the lens position is located from the predetermined position. Here, for example, if the lens position in the next shooting can be estimated by statistically processing the stored information on the lens position, the possibility of achieving focus only by moving the lens there is increased, There is a possibility that such estimation is incorrect. Therefore, if the predetermined position that is apart from the estimated lens position by a predetermined distance is obtained and the focus position is searched in the direction in which the lens position is in the starting point, the focus operation may be quickly achieved. Is extremely high.

Further, the estimating means obtains a range of lens positions having a high appearance frequency based on the information on the plurality of lens positions stored in the storage means, and the searching means makes the obtained appearance frequency. If the end of the high lens position range is set to the predetermined position and the focusing position is searched from there, the focusing position is included in the range with a high probability. The possibility that the focusing operation can be performed increases.

Further, when the storage unit updates the stored lens position for each photographing, more accurate estimation can be performed based on the latest information.

Further, the storage means stores the photographing mode in association with the lens position, and the estimating means further estimates the lens position in the next photographing based on the mode, and according to the mode. It is possible to perform more accurate estimation by utilizing the fact that the focal length of the subject changes.

The lens is preferably a focusing lens, and an electronic camera is preferable because the image plane AF method can be originally adopted due to its structure, but a silver salt camera may be used.

[0012]

DETAILED DESCRIPTION OF THE INVENTION A camera according to an embodiment of the present invention will be described in detail below with reference to the drawings. 1A and 1B are external views showing an embodiment of a digital still camera 100 to which the present invention is applied. FIG. 1A is a front perspective view of the digital still camera 100, and FIG. 1B is a rear perspective view. is there.

In FIG. 1, a digital still camera 10 is shown.
On the front side of 0, an image pickup unit 24 for picking up an image of a subject, a flash light emitting unit (flash device) 22 for emitting a flash light as auxiliary light to the subject, and a viewfinder 25 for confirming a composition including the subject when the photographer looks in. An image display unit 8 for displaying photographed images and the like, an information display unit 26 for displaying photographing setting status and the like, and an operation SW (switch) 21 for operating setting and switching of various functions are provided on the rear surface thereof. A release SW 21a for performing shutter release is provided on the upper surface of the digital still camera 100. The detailed description of each component will be given together with the description of the functional configuration described later.

FIG. 2 is a block diagram showing the functional configuration of the digital still camera 100. In FIG. 2, the digital still camera 100 includes a lens unit 1, a diaphragm 2, an image pickup unit 24 including a CCD 3, an image pickup circuit 4, and an A / D.
Conversion circuit 5, memory 6, D / A conversion circuit 7, image display unit 8, recording memory 9, compression / expansion circuit 10, CPU 11,
TG 12, AE / AF processing circuit 13, CCD driver 1
4, first motor 15, first motor drive circuit 16, second motor 17, second motor drive circuit 18, battery 19, EEP
It is composed of a ROM 20, an operation SW 21, a flash light emitting section 22, and a switching circuit 23.

The image pickup section 24 includes a lens unit 1 composed of a focusing lens group for taking in an optical image of a subject, which will be described later, a diaphragm 2 for adjusting the light amount of a light flux transmitted through the lens unit 1 and an exposure, and a lens unit 1 for the lens unit 1. A CCD (Charge Coupled Device) that photoelectrically converts an optical image of a subject formed on the optical path.
e) An image signal (analog signal) composed of 3 and photoelectrically converted is output to the image pickup circuit 4. That is, the imaging unit 24 has a function as an imaging unit.

The image pickup circuit 4 performs various kinds of image processing such as sensitivity correction of the image signal input from the CCD 3 in synchronization with the timing signal input from the TG 12 to generate a predetermined image signal and A / D-convert it. Output to the circuit 5. The A / D conversion circuit 5 converts the input image signal from an analog signal into a digital signal, and outputs the image data to the memory 6 or the AE / AF processing circuit 13 according to an instruction from the CPU 11.

The memory 6 is composed of a buffer memory or the like, and temporarily stores the input image signal. Further, when the memory 6 receives an image display instruction from the CPU 11,
The image display commanded image data is output to the A / A conversion circuit 7, and the D / A conversion circuit 7 performs analog conversion of the input image data and performs processing to adapt to output display, and the image display unit 8 The output is displayed. On the other hand, the memory 6
When the CPU 11 receives an image recording instruction, the image data is output to the compression / expansion circuit 10 and the compression / expansion circuit 10 outputs the input image data to the recording memory 9.

The image display unit 8 includes a TFT (Thin Fi).
lm Transistor), D / A
The image signal input from the conversion circuit 5 is output and displayed. The display is not limited to an image, and may be a text screen such as a menu screen for selecting a function.

The recording memory 9 is a recording memory composed of a semiconductor memory or the like, and is a recording memory having an image data recording area for recording the image data input from the compression / expansion circuit 10. The recording memory 9 may be, for example, a built-in memory such as a flash memory, a removable memory card or a memory stick, or a magnetic disk such as a hard disk or a floppy (registered trademark) disk. It may be a recording memory or the like. That is, the recording memory 9 has a function as a recording unit.

Upon receiving an image read instruction from the CPU 11, the recording memory 9 outputs the read image data to the compression / expansion circuit 10, and the compression / expansion circuit 10 outputs the image data.
Performs the decompression process of the input image data to execute the memory 6
Output to.

The compression / expansion circuit 10 compresses the image data input from the memory 6 by a predetermined encoding method, and the recording memory 9 for displaying the read-instructed image data on the screen. A decompression circuit for decoding and decompressing image data. That is, the compression / expansion circuit 10 has a function as a compression unit.

CPU (Central Process)
ing Unit) 11 reads out various application programs related to shooting stored in the EEPROM 9 to a work area (not shown), executes various processing such as shooting processing according to the programs, and displays the processing result in the image display unit 8 or information display. It is displayed on the section 26.

The CPU 11 drives and controls the AE / AF processing circuit 13 in response to the half-pressing of the release SW 21a to determine the exposure condition from the obtained photometric value, and when the lens unit 1 is detected by the AF processing. After being driven to the focal position, the exposure process is executed in response to the full depression of the release SW 21a, the generated image signal is subjected to image processing and digital conversion and temporarily stored in the memory 6, and then the compression / expansion circuit 10 converts the image data. It is compressed and output to the recording memory 9.

TG (Timing Generato)
r) 12 generates a predetermined timing signal and outputs it to the image pickup circuit 4, the CPU 11, and the CCD driver 14.

An AE (Auto Exposure: automatic exposure control) / AF (Auto Focus: automatic focus control) processing circuit 13 detects an appropriate AE processing circuit for executing an AE processing for detecting an appropriate exposure condition. AF
And an AF processing circuit that executes processing.
Each process is executed on the image data input from the A / D conversion circuit 5 according to an instruction from the CPU 11.

In the AE processing, the AE processing circuit performs arithmetic processing such as cumulative addition with respect to the brightness value of the input one screen or a predetermined area in the screen, and from this processing result, an appropriate value at the time of actual exposure is obtained. The exposure condition is calculated and output to the CPU 11. On the other hand, the AF processing circuit calculates the AF evaluation value for the input one screen or a predetermined area in the screen in the AF processing, and the calculated result is calculated by the CPU 1
Output to 1.

This AF evaluation value has such a characteristic that it becomes larger as the focus is improved. When a graph is created with the focusing lens position of the lens unit 1 on the horizontal axis and the AF evaluation value on the vertical axis, the in-focus point is obtained. A mountain with the top as the peak is formed. That is, by comparing the AF evaluation values obtained while moving the focusing lens with each other, the peak of the mountain, that is, the in-focus point can be obtained. The operation of obtaining the AF evaluation value in this way is called a search operation. In addition, A
The F evaluation value is calculated by analyzing the frequency of the image data for the input one screen or a predetermined area in the screen. In the frequency analysis, a band-pass filter is constructed by software, the integral value of the image signal intensity passed through this band-pass filter is calculated, and the calculation result is used as the AF evaluation value. That is, the AF evaluation value is contrast (brightness / darkness) information, and is calculated by performing an operation for obtaining the intensity of a specific frequency included in the image.

Now, the AF processing by the CPU 11 and the AF processing circuit will be described. The CPU 11 drives and controls the second motor drive circuit 18, which is a drive unit, to move the focusing lens of the lens unit 1 and gradually generate an image signal by the CCD 3 at each lens position. A
The E / AF processing circuit 13 calculates an AF evaluation value for each image data input from the A / D conversion circuit 5, compares the AF evaluation values, detects the lens position which is the maximum AF evaluation value as the in-focus point, and the CPU 11 Output to. That is, the AE / AF processing circuit 13 has a function as a search means.

Upon receiving an instruction from the CPU 11, the CCD driver 14 drives and controls the CCD 3 in synchronization with the timing signal input from the TG 12. Specifically, the charge storage time of the CCD 3 is controlled according to the exposure adjustment control.

The first motor drive circuit 16 controls the drive of the first motor 15 according to an instruction from the CPU 11, and the first motor 15 drives the diaphragm 2. In addition, the second motor drive circuit 18 receives the second motor 17 according to an instruction from the CPU 11.
And the second motor 17 drives the focusing lens of the lens unit 1.

The battery 19 is used in the digital still camera 100.
Is a power source that supplies power to each component, and, for example, a lithium battery or an alkaline dry battery is applied.

EEPROM (Electrically)
Erasable Programmable Re
The ad-only memory) 20 stores various application programs, processing programs, and the like related to image pickup of the digital still camera 100.

The operation SW (switch) 21 is a release S
W21a, a mode SW for switching functions, a menu SW for selecting settings, and the like are provided with various operation switches. When each switch is operated, a signal is generated and output to the CPU 11. The release SW 21a is
It is composed of a two-stage switch consisting of a half-press release SW for starting the AE and AF processing prior to the photographing operation and a full-press release SW for starting the actual exposure processing.

The flash light emitting section 22 is a light emitting section for emitting strobe light to the subject when the brightness of the surrounding environment detected at the time of photographing is insufficient, and the light emitting timing, the light emitting amount, etc. are controlled by the switching circuit 23. It

Next, the operation of this embodiment will be described with reference to the drawings. FIG. 3 is a flowchart illustrating a shooting process executed by the digital still camera 100 to which the present invention is applied.

In step S101 of FIG. 3, if the power switch (not shown) is on and the shooting mode is set, the CPU 11 waits for the release SW 21a to be half-pressed in step S102.

In step S102, the CPU 11 half-presses the release SW 21a to release the release SW2 of the first stage.
If it is determined that the push-down signal (S1 signal) of 1a is input, in step S103, the EEPROM that is the storage means.
The lens position information (and mode) stored in 20 is read. Subsequently, the CPU 11, which is an estimation unit, estimates the lens position (here, the proximity range) in the next shooting based on the read lens position information (and mode). This will be described below.

First, the relationship between the lens position and the subject distance is shown in FIG. The lens position is divided into 22 steps from infinity (∞) to very close (306 mm). First, the CPU 11 displays a lens position of a past shooting operation in a histogram based on the lens position information (also referred to as lens position information) stored in the EEPR0M20. An example thereof is shown in FIGS.

Here, it is assumed that the histogram shown in FIG. 5A is obtained. Since the histogram in FIG. 5A approximately follows the normal distribution, the CPU 11 estimates the range of ± 2σ of the average value (or maximum value) as the proximity range R (step S104), and thus with a high probability, The proximity range R can include the lens position at the time of the next shooting.
Therefore, in step S105, the CPU 11 drives and controls the second motor drive circuit 18 to the position of −2σ (lens position 5 here) which is the end thereof, moves the focusing lens, and drives the AE / AF processing circuit 13. By controlling the image obtained from the CCD 3 and moving the focusing lens to the high step (closest) side starting from that, the obtained AF evaluation values are compared to determine the optimum focus position. Obtained (step S106). Alternatively, the focusing lens may be moved to a position of + 2σ (lens position 9 in this case), which is another end of the proximity range R, and the focusing lens may be moved to the low step (infinity) side starting from that position.

Further, when the histogram shown in FIG. 5 (b) is obtained, the histogram of FIG. 5 (b) also substantially follows the normal distribution, so that the CPU 11 has a mean value (or maximum value) of ± 2σ. A range (not limited to this, ± σ or ± 3σ may be used, or a range including a mountain ridge) may be estimated as the proximity range R (step S).
104). Therefore, in step S105, the CPU 11
Is the position of -2σ (here, lens position 1
In 7), the second motor drive circuit 18 is drive-controlled to move the focusing lens, and the AE / AF processing circuit 13 is drive-controlled to process the image obtained from the CCD 3.
The optimum focusing position is obtained by comparing the obtained AF evaluation values while moving the focusing lens to the high step (closest) side with that point as the starting point (step S10).
6). It is also possible to move the focusing lens to a position of + 2σ (lens position 21 in this case), which is another end of the proximity range R, and move the focusing lens to the low step (infinity) side starting from that position.

Further, when the histogram shown in FIG. 5 (c) is obtained, the histogram in FIG. 5 (c) does not follow a normal distribution, but in such a camera, the lens position at the time of photographing is zero, that is, the scenery or the like. It shows that the in-focus position is infinite at a high frequency for shooting
The CPU 11 can estimate the proximity range R with the lens position 0 as the end (step S104). Therefore, in step S105, the CPU 11 moves the focusing lens to the lens position 0 which is the end thereof, processes the image obtained from the CCD 3, and moves the focusing lens to the high step (nearest) side starting from that point. By comparing the obtained AF evaluation values, the optimum focus position can be obtained (step S106). In the above three examples, if the focusing position does not exist within the proximity range R, the CPU 11 can obtain the correct focusing position by moving the focusing lens to a position other than the proximity distance R. . Also, without estimating the proximity range R,
For example, from a position mechanically separated by a predetermined step (for example, 5 steps) from the average value or the maximum value of the appearance frequency,
The search operation may be performed toward the average value or the maximum value.

However, a histogram as shown in FIG. 5 (d) may be obtained. In such a case, FIG.
The histogram in (d) does not follow a normal distribution, so ± 2
Even if the position of σ is determined, the in-focus position does not always exist within the range. Therefore, in such a case, the CPU 11 estimates the entire range to be the proximity range R in step S104, moves the focusing lens to the lens position 0 or 21 in step S105, and in step S106, uses that point as a starting point to move to a high step (close range). ) Side or low step (infinity) side, the focusing position can be obtained by comparing the obtained AF evaluation values while moving the focusing lens.

Further, a histogram as shown in FIG. 5 (e) may be obtained. In such a case, in the histogram of FIG. 5E, two peaks A and B having the appearance frequencies appear, and the proximity range cannot be simply determined. In this case, the CPU
11, in step S104, the range including the mountains A and B is estimated as the proximity range R, and in step S105, the focusing lens is moved to the lens position 3 which is −2σ of the mountain A,
In step S106, the focusing position can be obtained by comparing the obtained AF evaluation values while moving the focusing lens to the high step (closest) side or the low step (infinity) side with that as the starting point. it can. Note that the focusing lens may be moved to a position of + 2σ (lens position 19 in this case), which is another end of the proximity range R, and the focusing lens may be moved to the low step (infinity) side starting from that position.

However, even when the histogram shown in FIG. 5D or 5E is obtained, the proximity range R can be estimated with a certain degree of accuracy according to the set photographing mode. For example, when the red-eye prevention mode is set by the operation of the photographer, the CPU 11 determines that the main subject is within the range (for example, 3 m ahead of the camera) where the irradiation light from the flash light emitting unit 22 reaches, and the lens position 0 The optimum focusing position can be obtained while moving the focusing lens to the high step (closest) side with the focusing lens as the starting point. Also, when the bulb mode is set, the CPU 11 determines that night view photography or the like is performed, and moves the focusing lens to the lens position 0,
The optimum focusing position can be obtained while moving the focusing lens from that point to the high step (closest) side. On the other hand, when the flash light emission prohibition mode is set, the CPU 11 determines that macro photography or the like will be performed, moves the focusing lens to the lens position 22, and the focusing lens moves to the low step (infinity) side from that point. The optimum focus position can be obtained while moving the.

The above-mentioned examples of the photographing modes are based on a general empirical rule. However, by storing the photographing mode information in the EEPROM 20 in association with the lens position information, when any one of the photographing modes, If data is obtained that the frequency of shooting is high at this subject distance, the proximity range may be estimated using this data.

After the in-focus position is obtained as described above, in step S107 in FIG. 3, the release SW 21a is released.
Wait for is pressed. Although not shown in the figure, it is assumed that the photometric processing is completed at this point.

In step S107, the CPU 11 fully presses the release SW 21a to release the second release SW2a.
If it is determined that the push-down signal (S2 signal) of 1a is input, the image data is taken in at step S108. In step S109, the CPU 11 calculates image processing parameters necessary for image processing such as gradation correction and white balance based on the captured image data, and after performing image processing on the image data using the obtained image parameters. In step S110, the processed image data is recorded in the recording memory 9. Furthermore, the CPU 11
In step S111, the lens position and the shooting mode at the time of shooting can be written in the EEPROM 20 as information. Some cameras are controlled to move a lens to a hyperfocal position and take an image when the peak of the AF evaluation value cannot be detected (that is, when the in-focus position cannot be detected). In the case of such a camera, since the lens is not always in the in-focus position in the shooting result, the accuracy of estimation becomes low if the lens position information is recorded for each shooting. Therefore, when shooting is performed without being able to detect the in-focus position, the lens position information is not recorded, and it is not always necessary to write for each shooting. Since the old information may reduce the accuracy of the estimation of the proximity range R, the lens position information to be written in the EEPROM 20, for example, may be up to 50 items from the latest shooting, and the old information may be automatically updated. It is desirable to update it by deleting it. After that, the flow returns to step S101.

Although the present invention has been described with reference to the embodiments, the present invention should not be construed as being limited to the above embodiments, and it goes without saying that appropriate modifications and improvements are possible. is there. For example, the present invention is applicable not only to electronic cameras such as digital still cameras, but also to silver halide cameras.

[0049]

According to the present invention, it is possible to provide a camera having a simple structure and capable of performing a focusing operation more quickly.

[Brief description of drawings]

FIG. 1 is a digital still camera 100 to which the present invention is applied.
It is an external view which shows one Embodiment.

FIG. 2 is a block diagram showing a functional configuration of a digital still camera 100.

FIG. 3 is a flowchart showing the operation of the digital still camera according to the present embodiment.

FIG. 4 is a diagram showing a relationship between a lens position and a subject distance.

FIG. 5 is a histogram showing the appearance frequency of stored lens positions.

[Explanation of symbols] 1 lens 11 CPU 13 AE / AF processing circuit 18 Second motor drive circuit 20 EEPROM

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Claims (7)

[Claims] 1. A storage unit that stores information about a lens position obtained for each shooting, and a proximity range that is close to a lens position in the next shooting based on the information about the lens position stored in the storage unit. A camera, comprising: an estimating unit for estimating; and a driving unit for moving a lens within the proximity range estimated by the estimating unit. 2. A camera having a function of searching a focus position based on an image captured while moving the lens, a storage unit for storing information on the lens position obtained for each photographing, and the storage unit. Estimating means for estimating the lens position in the next photographing based on the information relating to the lens position stored in, and the lens at a predetermined position separated by a predetermined distance from the lens position estimated by the estimating means. A camera comprising: a drive unit that moves the lens and a search unit that searches for a focus position in the direction in which the lens position is located from the predetermined position. 3. The estimating means obtains a range of lens positions having a high appearance frequency based on the information on the plurality of lens positions stored in the storage means, and the searching means has the obtained appearance frequency. The camera according to claim 2, wherein an end of a range of a high lens position is set as the predetermined position, and a focusing position is searched from there toward the range. 4. The camera according to claim 1, wherein the storage unit updates the stored lens position every time photographing is performed. 5. The storage means stores a shooting mode in association with the lens position, and the estimating means further estimates the lens position in the next shooting based on the mode. The camera according to claim 1. 6. The camera according to claim 1, wherein the lens is a focusing lens. 7. The camera according to claim 1, which is an electronic camera.