JP2002287195A - Image pickup device and camera-shake detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a camera-shake with ease without requiring special additive structures, etc. SOLUTION: This device has a motor 11 for automatically focusing a an object image by driving a lens 12 and has a CPU 22 which calculates respective focusing evaluation values just before photographing and during photographing while occasionally driving this motor 11 and detects the camera-shake of the photographed image by comparing the two focusing evaluation values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image pickup apparatus such as a digital camera having an automatic focusing function and a camera shake detection method performed by the image pickup apparatus.

[0002]

2. Description of the Related Art In recent years, with the spread of personal computers, digital still cameras (hereinafter referred to as "digital cameras") for recording images in the form of digital data on a memory card in which a nonvolatile semiconductor memory is enclosed instead of a silver halide film. ) Is widely and widely used.

Some digital cameras of this type have a mechanism for correcting a so-called camera shake, in which a captured image is blurred particularly at the time of low-speed shutter or telephoto shooting.

In this method, the lens barrel has an acceleration sensor and a mechanism for decentering the lens optical axis, and the lens optical axis is decentered in the opposite phase in accordance with the phase of the camera shake detected by the acceleration sensor. Absorb the swing of the captured image,
This is generally referred to as an optical image stabilization mechanism.

Further, the state of camera shake is detected by an acceleration sensor, and digital data of an image obtained by photographing is processed in accordance with the state of camera shake, thereby obtaining image data excluding the influence of camera shake. In addition, a camera which performs image stabilization using an image processing technique has been considered.

[0006]

The above-mentioned optical camera shake correction mechanism requires an acceleration sensor for detecting camera shake in the lens barrel and a mechanism for decentering the optical axis of the lens. Therefore, it is used only in some effective models.

The image stabilization technique using image processing also requires a great deal of time for image processing, and sometimes a digital camera in which image data must be sequentially written at high speed to a medium in order not to miss a photo opportunity. It is an unsuitable technique and requires a structure such as an acceleration sensor, and has not been put to practical use.

The present invention has been made in view of the above-mentioned circumstances, and has as its object the purpose of simply detecting the state of occurrence of camera shake without requiring a special additional structure or the like, and retrieving the information. An object of the present invention is to provide an imaging device and a camera shake detection method that can be used for an image to be recorded.

[0009]

According to the first aspect of the present invention,
Automatic focusing means for driving a photographic lens to perform automatic focusing of a subject image; evaluation value calculating means for calculating a focus evaluation value for evaluating a focusing state of the automatic focusing means; The focus evaluation value obtained by the evaluation value calculation means is compared with the focus evaluation value obtained by the evaluation value calculation means corresponding to the captured image, and the camera shake state of the captured image is detected based on the comparison result. A camera shake detecting means.

With such a configuration, the occurrence of camera shake can be detected from the comparison result of the focus evaluation values before and after photographing. Therefore, if the image pickup apparatus has an automatic focusing function, a special additional structure is required. This makes it possible to easily detect camera shake without the need for such operations.

According to a second aspect of the present invention, in the first aspect of the present invention, the automatic focusing means determines a position where the contrast of the subject image is the highest as an in-focus position, and the evaluation value calculating means includes: The high frequency component of the spatial frequency of the obtained image is used as the focus evaluation value.

With this configuration, in addition to the operation of the first aspect of the present invention, when performing automatic focusing by the contrast method, a high spatial frequency that can be obtained in the process of compressing image data is obtained. By using the area component as the focus evaluation value, the camera shake can be detected more easily and accurately.

According to a third aspect of the present invention, in the first aspect of the present invention, the camera shake detecting means detects a camera shake state of a photographed image at a plurality of levels, and the camera shake state detected by the camera shake detecting means. And recording control means for determining whether or not to record the photographed image in accordance with the level.

According to this structure, in addition to the effect of the first aspect of the present invention, for example, if a camera shake is not generated at all or a very small image is generated, the image is automatically recorded on a medium. On the other hand, the presence or absence of recording on the medium can be controlled according to the level of the camera shake state, such as not recording an image with a large degree of camera shake on the medium, and the medium has a limited capacity. Even those can be used efficiently.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the camera shake detecting means detects a camera shake state of the photographed image at a plurality of levels, and detects the camera shake state detected by the camera shake detecting means. And a recording control means for judging whether or not to record a photographed image by an operation performed based on the result displayed on the display means.

With this configuration, in addition to the operation of the first aspect of the present invention, it is possible to select the recording of an image having a camera shake corresponding to the user's intention.

According to a fifth aspect of the present invention, in the first aspect of the present invention, there is further provided a recording control means for recording information of a camera shake state detected by the camera shake detection means together with a photographed image. .

With this configuration, in addition to the operation of the first aspect of the present invention, it is possible to know the degree of camera shake of the recorded image during reproduction of the image.

According to a sixth aspect of the present invention, there is provided an automatic focusing step of driving a photographic lens to automatically focus an object image, and calculating a focus evaluation value for evaluating a focusing state in the automatic focusing step. And comparing the focus evaluation value obtained in the above-described evaluation value calculation step before photographing with the focus evaluation value obtained in the above-described evaluation value calculation step corresponding to the captured image, and comparing the values. A camera shake detecting step of detecting a camera shake level of an image photographed based on the result.

According to such a method, the state of occurrence of camera shake can be detected from the comparison result of the focus evaluation values before and after photographing, so that an image pickup apparatus having an automatic focusing function has a special additional structure. This makes it possible to easily detect camera shake without the need for such operations.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a digital camera will be described below with reference to the drawings.

FIG. 1 shows the circuit configuration, and reference numeral 10 denotes a digital camera. The digital camera 10 can set a recording mode and a reproduction mode. In a monitoring state of the recording mode, a CCD 13 arranged behind a photographing optical axis of a lens 12 whose focusing position is driven by a motor 11 is provided. The scanning is driven by a timing generator (TG) 14 and a vertical driver 15, and a photoelectric conversion output for one screen is output at regular intervals.

The photoelectric conversion output is appropriately adjusted in gain for each of the RGB primary color components in the state of an analog value signal, sampled and held by a sample and hold circuit (S / H) 16, and then subjected to an A / D converter 17. Are converted to digital data, and color processing including pixel interpolation is performed by the color processing circuit 18 to generate a luminance signal Y and color difference signals Cb and Cr of digital values, and the DMA (Dir)
ect MemoryAccess) controller 19
Is output to

The DMA controller 19 includes a luminance signal Y and color difference signals Cb and C output from the color process circuit 18.
r is once written into a buffer inside the DMA controller 19 using the composite synchronizing signal, the memory write enable signal, and the clock signal from the color process circuit 18, and is DMA-transferred to the DRAM 21 via the DRAM interface (I / F) 20. Perform

The CPU 22 calculates the D and D of the luminance and color difference signals.
After the completion of the DMA transfer to the RAM 21, the luminance and color difference signals are transferred to the DRAM 2 via the DRAM interface 20.
1 and VR via the VRAM controller 23.
Write to AM24.

A digital video encoder (hereinafter abbreviated as "video encoder") 25 periodically reads out the luminance and color difference signals from the VRAM 24 via the VRAM controller 23, and generates a video signal based on these data. Output to the display unit 26.

The display section 26 comprises, for example, a color liquid crystal display panel with a backlight and its driving circuit.
It is located on the back side of the camera body,
VF (Electronic View Find)
r: an electronic viewfinder), and performs display based on a video signal from the video encoder 25, thereby displaying an image based on image information taken in from the VRAM controller 23 at that time. .

In the state where the image at that time is displayed on the display unit 26 in real time as a monitor image, the shutter in the plurality of keys constituting the key input unit 27 at the timing when it is desired to record and save the image is displayed. When a key is operated, a trigger signal is generated.

In response to the trigger signal, the CPU 22 stops the path from the CCD 13 to the DRAM 21 immediately after the completion of the DMA transfer of the luminance and color difference signals for one screen taken in from the CCD 13 to the DRAM 21 at that time. ,
Transit to the record save state.

In this recording and storage state, the CPU 2
The luminance and color difference signals for one frame written in the AM 21 are transferred to the Y, Cb,
Each component of Cr is read out in a unit called a basic block of 8 pixels vertically by 8 pixels horizontally and read out in a JPEG circuit 28
And the ADCT (Adapt
five Discrete Cosine Tran
sform: adaptive discrete cosine transform) and data compression by processing such as Huffman coding which is an entropy coding method, and the obtained coded data is read out from the JPEG circuit 28 as a data file of one image.
Is written in a flash memory 29 which is a non-volatile memory, which is detachably mounted as a storage medium for (1).

When the compression processing of the luminance and chrominance signals for one frame and the writing of all the compressed data to the flash memory 29 are completed, the CPU 22 again operates the CCD 13.
Again from the path to the DRAM 21.

At this time, the CPU 22 also creates image data in which the number of constituent pixels of the original image data has been significantly thinned out, associates this with the original image data as a preview image also called a thumbnail image, and 29.

The key input unit 27 has a recording (REC) mode and a reproduction (PL) mode in addition to the shutter key.
AY) Record / replay mode switch key to switch between modes, "Menu" key to display various menu items, up / down / left / right directions for selection of image and mode, designation of important adjustment position on white balance screen, etc. And an "Enter" key for deciding the selection, and a signal accompanying the key operation is sent directly to the CPU 2.
2 is sent.

Further, in the reproduction mode, the CPU 22
The path from D13 to the DRAM 21 is stopped, and the CPU 22 reads the code data of a specific one frame from the flash memory 29 according to the operation of the image selection key or the like of the key input unit 27 and writes it to the JPEG circuit 28, and the JPEG circuit 2
The luminance and chrominance signals for one frame are developed and stored in the VRAM 24 via the VRAM controller 23 in units of 8 × 8 basic blocks obtained by performing the decompression processing at 8. Then, the video encoder 25 outputs the VR
A video signal is generated based on the luminance and color difference signals for one frame which are developed and stored in the AM 24 and displayed on the display unit 26.

Next, the operation of the above embodiment will be described.

FIG. 2 exemplifies mainly the processing contents of the CPU 22 from the monitoring state in the recording mode to the taking of an image in response to the operation of the shutter key and the recording of the obtained image data in the flash memory 29 as a recording medium. Is what you do.

In the monitoring state, it is determined whether or not the shutter key of the key input unit 27 has been turned on while determining whether or not it is time to perform automatic focusing (AF) at a predetermined cycle (step S01). (Step S
02) is repeatedly executed to wait for these.

The automatic focus timing determination in step S01 is performed at a timing prior to the driving of the CCD 13 for monitoring, which is performed in parallel, and an image displayed on the display unit 26 by monitoring is determined. For example, a general video rate, ie, 1/30 [second]
If it is updated one by one, this 1/30 [second]
Is set in advance as a predetermined cycle.

If it is determined in step S01 that it is time to perform automatic focusing, the lens 12 is driven by the motor 11 so that the optimal focusing position is obtained by automatic focusing, and the focusing is performed. Is obtained and updated and stored in, for example, an internal register of the CPU 22 (step S03).

In this case, assuming that the digital camera 10 adopts, for example, a contrast method which is one of the passive autofocus techniques, the CPU 22
The high frequency component of the spatial frequency of the luminance signal Y obtained through the M interface 20 is extracted, and the lens 12 is driven by the motor 11 so that the value is maximized. The extracted value of the high-frequency component at that time is sequentially updated and stored as a focus evaluation value.

When it is determined in step S02 that the shutter key of the key input unit 27 has been turned on, automatic focusing is performed again for photographing, and the evaluation value is acquired together (step S04). The automatic exposure (AE) in the focused state is performed to obtain an appropriate exposure value, and the aperture and the shutter speed (not shown) are set here. (Step S05).

Then, the CCD 13 is driven under the conditions obtained by the above-mentioned automatic focusing and automatic exposure to obtain image data. The obtained image data is subjected to automatic white balance (AWB) adjustment by the color process circuit 18 and then transferred to the DRAM 21. Transfer (step S06) Here, the CPU 22 compares the focus evaluation value stored immediately before the shutter key is turned on with the focus evaluation value obtained in step S04, and sets the comparison result in advance. Depending on the threshold value, for example, 5
It is expressed by the camera shake levels 0 to 4 (step S0
7).

In this case, for example, it is assumed that the focus evaluation value is different only when the camera shake level 0 is within the range of the error, and that no camera shake occurs, and conversely, the camera shake level 4 is different from the focus evaluation value. Is extremely large and unsuitable for viewing, and the camera shake levels 0 and 1 are assumed to be within an allowable range for photographing, and are unconditionally recorded in the flash memory 29.

Therefore, in step S07, the two focus evaluation values immediately before and at the time of photographing are compared, and the comparison result is expressed by the value of the camera shake level. It is determined whether or not the level is equal to or lower than, for example, the camera shake level 1 (step S08).

When the camera shake level is 0 or the camera shake level is 1, it is determined that there is no problem in the in-focus state, and
The luminance and color difference signals for one frame written in the AM 21 are read out through the DRAM
The data is sent to the PEG circuit 28 to compress the data, and the obtained code data is recorded and stored in the flash memory 29 as a data file of one image (step S09), and then returns to the monitoring state from step S01.

If it is determined in step S08 that the comparison result between the two focus evaluation values immediately before and at the time of photographing is higher than a certain camera shake level, for example, camera shake level 1, the value of the camera shake level is displayed. While displaying on the unit 26 (step S10), the digital camera 10 waits for any selection operation by the user of the digital camera 10 (step S11).

FIG. 3 shows a message indicating whether or not the image data is recorded and stored in the flash memory 29 together with a preview image of the image data when the camera shake level of the image obtained by photographing is 2. FIG.

In this case, if the image is to be stored in the flash memory 29, the "Ent"
If the "er" key is not stored, the "menu" key may be operated as indicated by a message. In step S11, the process waits until one of these keys is operated.

When it is determined in step S11 that one of the above key operations has been performed, the next operation is the "Enter" key, which is used to record an image in the flash memory 29. Is determined (step S12), and if so, the flow advances to step S09 to read out the luminance and color difference signals for one frame written in the DRAM 21 through the DRAM interface 20 and perform the JPEG operation. The data is sent to the circuit 28 and compressed, and the obtained code data is recorded and stored in the flash memory 29 as a data file of one image, and then returns to the monitoring state from step S01.

Also, what is operated in step S12 is not the "Enter" key but the "menu" key,
If it is determined that the operation is not an operation for recording an image in the flash memory 29,
The content of the image data written in the DRAM 21 is deleted as it is (step S13), and the state returns to the monitoring state from step S01 again in preparation for the next photographing.

As described above, since the state of occurrence of camera shake can be detected from the result of comparison between the two focus evaluation values immediately before and at the time of shooting, it is very common to have an automatic focusing function except for pan-focus. The digital camera 10 can easily detect camera shake without requiring a special additional structure or the like.

In particular, since the camera shake state of a photographed image is detected at a plurality of levels, and it is determined whether or not to record the photographed image in accordance with the detected camera shake state level. If the image has not been raised at all, or if it has been raised, only a few images are automatically recorded on the medium, while an image with a large degree of camera shake is not immediately recorded on the medium. Flash memory 29 as a medium corresponding to the level
Can be controlled, and even if the flash memory 29 has a limited capacity, it can be used efficiently.

In particular, the camera shake state of the photographed image is detected at a plurality of levels, the detected camera shake state level is displayed on the display unit 26, and then the photographed image is recorded by an operation performed by the user. Since the determination is made as to whether or not to perform the recording, it is possible to freely select whether or not to record the image in which the camera shake has occurred, according to the intention of the user.

In the step S09, the DRAM
The JPEG circuit 28
Although it has been described that the data is compressed and stored in the flash memory 29 after the data compression, the image data may be recorded with the information of the camera shake level added thereto.

When such an image is read out from the flash memory 29 and reproduced, if the information of the camera shake level can be displayed together with a part of the image by setting, how much the image is It is possible to know whether or not the image was shot in a camera shake state, and this can be used for editing image data and learning the shooting technique of the user.

FIG. 4 shows a display section 26 for displaying such image data.
5 illustrates that the image shake level of the image is 2.

In the above embodiment, the automatic focusing is performed in accordance with the contrast of the image, and the high frequency component of the spatial frequency of the obtained image is used as the focus evaluation value.

For this reason, when performing the automatic focusing of the contrast method, which is a more general and widely used focusing method, a high frequency component of a spatial frequency which can be obtained in the process of compressing image data. Is used as the focus evaluation value, the camera shake can be detected more easily and accurately.

The present invention is not limited to the automatic focusing of the contrast method. For example, an infrared light receiving element receives reflected light of infrared light emitted from an infrared LED and directly obtains a distance value to a subject image by a time difference. In the case of the active type automatic focusing, the distance value may be used as the focus evaluation value, and the camera shake state may be detected based on the degree of time-series change.

In addition, the present invention is not limited to the above-described embodiment, but can be variously modified and implemented without departing from the gist thereof.

Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiments, at least one of the problems described in the column of the problem to be solved by the invention can be solved and the effects described in the column of the effect of the invention can be solved. In a case where at least one of the effects described above is obtained, a configuration in which this component is deleted can be extracted as an invention.

[0062]

According to the first aspect of the present invention, since the state of occurrence of camera shake can be detected from the comparison result of the focus evaluation values before and after shooting, any imaging apparatus having an automatic focusing function can be used. The camera shake can be easily detected without requiring a special additional structure or the like.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, in the case of performing the automatic focusing by the contrast method, the spatial frequency which can be obtained in the process of compressing the image data. By using the high-frequency component as the focus evaluation value, the camera shake can be detected more easily and accurately.

According to the third aspect of the present invention, in addition to the effects of the first aspect of the present invention, for example, if a camera shake is not generated at all or a very small image is generated, the medium is automatically stored. On the other hand, the presence or absence of recording on the medium can be controlled according to the level of the camera shake state, such as not recording an image with a large degree of camera shake on the medium. Can be used efficiently.

According to the fourth aspect of the present invention, in addition to the effect of the first aspect of the present invention, it is possible to select the recording of an image having a camera shake corresponding to the user's intention.

According to the fifth aspect of the present invention, in addition to the effects of the first aspect of the present invention, it is possible to know the degree of camera shake of the recorded image when reproducing the image.

According to the sixth aspect of the present invention, since the occurrence of camera shake can be detected from the comparison result of the focus evaluation values before and after shooting, any image pickup apparatus having an automatic focusing function can be used.
The camera shake can be easily detected without requiring a special additional structure or the like.

[Brief description of the drawings]

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

FIG. 2 mainly shows C in a recording mode according to the embodiment;
9 is a flowchart showing processing by a PU.

FIG. 3 is an exemplary view showing a screen display state during operation in a recording mode according to the embodiment.

FIG. 4 is an exemplary view showing a screen display state during operation in a reproduction mode according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Digital camera 11 ... Motor 12 ... Lens 13 ... CCD 14 ... Timing generator (TG) 15 ... Vertical driver 16 ... Sample hold circuit (S / H) 17 ... A / D converter 18 ... Color process circuit 19 ... DMA Controller 20 ... DRAM interface (I / F) 21 ... DRAM 22 ... CPU 23 ... VRAM controller 24 ... VRAM 25 ... Video encoder 26 ... Display unit 27 ... Key input unit 28 ... JPEG circuit 29 ... Flash memory

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 5/232 G02B 7/11 NB // H04N 101: 00 G03B 3/00 A F term (reference) 2H011 AA03 BA11 BA31 BB04 DA00 2H051 AA08 BA45 BB11 CE30 EB10 5C022 AA13 AB24 AB55 AC03 AC18 AC42 AC52 AC69 AC74

Claims (6)

[Claims] An automatic focusing means for driving an imaging lens to perform automatic focusing of a subject image; and an evaluation value calculating means for calculating a focus evaluation value for evaluating a focusing state of the automatic focusing means. Comparing the focus evaluation value obtained by the evaluation value calculating means before shooting with the focus evaluation value obtained by the evaluation value calculating means corresponding to the shot image; An image pickup apparatus comprising: a camera shake detection unit that detects a camera shake state. 2. The automatic focusing means determines a position where the contrast of an object image is highest as a focus position, and the evaluation value calculating means determines a high frequency component of a spatial frequency of an obtained image as a focus evaluation value. The imaging device according to claim 1, wherein the imaging device is used as a device. 3. The camera shake detecting means detects a camera shake state of a photographed image at a plurality of levels, and determines whether to record the photographed image in accordance with the camera shake state detected by the camera shake detecting means. 2. The image pickup apparatus according to claim 1, further comprising a recording control unit for judging the condition. 4. A camera shake detecting means for detecting a camera shake state of a photographed image at a plurality of levels, a display means for displaying the level of the camera shake state detected by the camera shake detection means, and a display means for displaying the level. 2. The imaging apparatus according to claim 1, further comprising a recording control unit that determines whether or not to record the captured image by an operation performed based on the result. 5. The image pickup apparatus according to claim 1, further comprising a recording control unit for recording information on a camera shake state detected by said camera shake detection unit together with a photographed image. 6. An automatic focusing step of driving a photographing lens to automatically focus an object image, and an evaluation value calculating step of calculating a focus evaluation value for evaluating a focusing state in the automatic focusing step. Comparing the focus evaluation value obtained in the evaluation value calculation step before shooting with the focus evaluation value obtained in the evaluation value calculation step corresponding to the shot image, A camera shake detecting method for detecting a camera shake level.