Detecting abnormality of image capturing apparatus

A digital still camera having a photographing lens system set in a lens tube, a CCD solid image-capturing device, and a mechanical shutter. The mechanical shutter is set on a light path between the photographing lens system and the CCD solid image capturing device. The CCD solid image-capturing device divides a frame of an image into a plurality of fields and transmits the fields serially. The camera compares at least two fields of them, and detects abnormality caused by, for example, abnormal operation of the mechanical shutter or light leakage of the lens body. The camera also displays or announces the abnormality to a user.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique of an image-capturing apparatus having an image-capturing device. And more particularly to an apparatus, method and computer program suitable for detecting abnormality of an image-capturing apparatus.

2. Discussion of the Background

In an image-capturing apparatus using an interlace-CCD (coupled charge device), a CCD solid image-capturing device is exposed by an at least 2-dimensional optical image projected through an optical system, and converts the optical image to electric signals. After the CCD solid image-capturing device is exposed by the optical image for a predetermined time, the CCD image-capturing device divides a frame of the electric signals into a plurality of fields, and transmits them serially. In this case, a light shield such as a mechanical shutter shuts to prevent an incoming light, and prevents a second or later field from being exposed more during transmission the first field, and makes each field have the same exposure time. Japanese Patent Laid Open No. 2001-285688 describes this type of an image-capturing apparatus having interlace-CCD with a filter of an elementary color system and a mechanical shutter.

SUMMARY OF THE INVENTION

In an image-capturing apparatus like above, the second field is exposed during transmission the first field if light leaks into a lens body. Such leakage makes the value of the second field incorrectly bigger than the first field, because the second field has longer exposure time than the first field. The third field and later fields also have incorrectly bigger values than the second field. This problem can arise when a mechanical shutter fails to shut correctly there by allowing incoming light to leak through to the image-capturing device. Image data taken in these cases include incorrect data. This situation is a serious problem and must be detected and fixed quickly when light leaks into a lens body or a mechanical shutter fails to work correctly.

In view of the foregoing, it is an object of the present invention to provide an image-capturing apparatus, method and computer program that can detect an abnormality in an image-capturing apparatus and indicate or announce to a user that an abnormality exists.

In addition to the novel image-capturing apparatus just described, this patent specification may be implemented in many other specific forms, including in an apparatus, method, or computer program, as will be apparent to those skilled in the relevant art(s), without departing from the spirit or scope of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In describing preferred embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology selected and it is to be understood that each specific element includes all equivalents that operate in a similar manner.

An outside view of a digital still camera101as an image-capturing apparatus relating to the embodiment of the present invention is shown inFIGS. 1A-1D. At a front surface101aof the digital still camera101, there is provided a photographing lens102and a lens body103.

At back surface101bof the digital camera101, there is provided a display device104, an operating button105, an ENTER button105a, a CANCEL Button105b, a zooming button106and a viewfinder107. The display device104is composed of a liquid crystal display, an electro luminescence display, a field emitting display or the like, and displays the subject when photographing or playing and displaying a photographed image. The operating button105carries out various operations such as a photographing condition setting, photographing mode changing or selecting of played image or the like.

Other than a normal mode for carrying out a normal photographing, the digital camera101has various photographing modes such as a self-timer mode in which the photographing is carried out after a certain time has passed after pressing a shutter release button, a close photographing mode for photographing by going close to the subject, a remote control photographing mode for carrying out the photographing by receiving a photographing signal from the remote control device, or an interval photographical mode for carrying out the photographing repeatedly in every predetermined time interval after the shutter release button is pressed. The changing of those photographing modes can be carried out by an operation of the operating button105.

The ENTER button105aand the CANCEL button105bare buttons for confirming and canceling the various operations by the operating button105, and the zooming button106is a button for carrying out a zooming operation of a photographing image to the subject. The viewfinder107is an observation window for viewing the subject when photographing and it transmits the image of the subject from the front surface101a.

There is provided on an upper surface101cof the digital camera101a power button108, a switching over dial109, and a shutter release button110. The power button108is a button for carrying out an on-off operation of a main power provided in a body of the digital camera101, and the switching over dial109is for switching between operating modes.

It is possible to switch the operating mode of the digital camera101to the photographing mode for photographing a subject, or to a playing mode for playing and displaying the photographed image on the display device104.

The shutter release button110is retained and biased upwardly by a spring201as shown inFIG. 2. Signal lines A-C are arranged in order in such a manner as to overlap above and below at a lower part of a lower end portion110aof the shutter release button110, and contact points a-c are respectively provided directly under the lower end portion110a. The signal lines A-C are retained so as to provide a certain space by spacers202to prevent the contact points a-c from contacting each other when the shutter release button110is not pressed.

The signal lines A and B have flexibility. When the shutter release button110is pressed downward, first of all the contact points a and b are contacted (half-pressed condition) by flexing of the signal line A which is pressed by the lower end portion110aof the shutter release button110, and the contact points b and c are contacted (full-pressed condition) by flexing of the signal line B by the further pressing of the shutter release button110.

The contact points a and b are a part of an inputting device for inputting a focusing starting trigger (means for inputting a focusing starting trigger), and the contact points b and c are a part of an inputting device for inputting a photographing starting trigger (means for inputting a photographing starting trigger). That is to say, the focusing starting trigger is inputted by a short circuit of the signal lines A and B when the contact points a and b are contacted, and the photographing starting trigger is inputted by the short circuit of the signal lines B and C when the contact points b and c are contacted.

At side surface101dof the digital camera101, there is provided a slot111to insert a memory card320.

FIG. 3is a schematic block diagram of the digital still camera101. This embodiment is mainly explained as a digital still camera101using a CCD solid image-capturing device301with a primary color filter as an image-capturing device. A primary color filter is composed of small filters and each small filter penetrates a light of red, green and blue respectively. However, the present invention can be embodied in a digital still camera using a CCD solid image-capturing device with a complementary color filter. A complementary color filter is composed of small filters and each small filter penetrates a light of Yellow, Cyan, Magenta and Green respectively.

The digital still camera101has a photographing lens102, a mechanical shutter302, a CCD solid image capturing device301, a front-end signal processing unit303, a signal processing unit304, a RAM (random access memory)305, a display device104, a CPU (central processing unit)306, an operating unit307, an audio output device308, a ROM (read-only memory)309and a motor driver310.

The photographing lens102is an optical system, which focuses a subject image on a light-receiving surface of the CCD solid image-capturing device301. The mechanical shutter302is set between the photographing lens102and the CCD solid image capturing device301, and controls exposure of the CCD solid image-capturing device301by shutting the light path. When the mechanical shutter302is open, incoming light through the photographing lens102exposes the CCD solid image-capturing device301. When the mechanical shutter302is closed, the incoming light is prevented from exposing the CCD solid image-capturing device302. The CCD solid image-capturing device302exchanges incoming a subject image exposed on the light-receiving surface to a frame of electric signals, and holds them temporally. Then the CCD solid image-capturing device301transmits the frame of electric signals with three-fields interlace-transmission.FIG. 4explains the three-fields interlace-transmission of the CCD solid image-capturing device301. The CCD solid image-capturing device301separates the frame of electric signals into three fields and transmits them serially.

FIG. 5is a timing chart when a mechanical shutter302shuts normally during transmission of the three fields. The shutter is set between a photographing lens102and the CCD solid image-capturing device301, and controls incoming-light to the CCD solid image-capturing device301.

FIG. 6is a timing chart when the mechanical shutter302fails to close during transmission of the three fields, which shows how much the exposure time of each field changes in comparison to the normal exposure time.

FIG. 7is a timing chart when the mechanical shutter302delayed in closing, which shows how much the exposure time of each field changes in comparison to the normal exposure time.

The front-end signal processing unit303has a CDS (correlated double sampling) circuit311, an AGC (auto gain controller) circuit312, an A/D (analog-digital) converter313and a timing generator314, and processes signals from the CCD solid image capturing device301. The CDS circuit311processes correlated double sampling to the image signals outputted from the CCD solid image-capturing device301. The AGC circuit312adjusts a signal outputted by the CDS circuit311to a proper signal level automatically. The A/D converter313converts an analog signal outputted by the AGC circuit312to a digital signal. The timing generator314generates timing signals in response to VD signals (vertically synchronized driving signal) and HD signals (horizontally synchronized driving signal) and in cooperation with the CPU306.

The signal processing IC304has a CCD interface315, a memory controller316, a display device interface317, an image compressor318and a YUV converter319. The CCD interface315inputs the VD and HD signals to the timing generator314. Thus the timing generator314inputs the timing signals to the CCD solid image-capturing device301, the CDS circuit311, the AGC circuit312and the A/D converter313, and synchronizes them correctly. The signal processing IC304stores digital image data into the RAM305and processes one in cooperation with the CPU306. The memory controller stores digital image data given by the A/D converter313in the front-end signal-processing unit303to the RAM305. The image compressor318compresses the digital image data. The YUV converter319converts the digital image data from in RGB-format to in YUV-format and stores them to RAM305. The memory controller316sends digital image data, outputted by A/D converter313or restored from the RAM305, to the display device104through the display device interface317. The image compressor318compresses digital image data outputted by the A/D converter313or restored from the RAM305. The memory controller316also stores the digital image data restored from the RAM305to the memory card320.

We can use a semiconductor memory such as SDRAM (synchronous dynamic random access memory) as the RAM305. The RAM305stores raw RGB-format data, converted YUV-format data and compressed JPEG data. The display device104can be a device which shows images, such as a LCD (liquid crystal display). The display device104receives image data out of the A/D converter313through the display device interface117, or out of the RAM205. And, the display device304indicates an abnormality and a way to dealing with the abnormality when the abnormality occurs as described below. The motor driver310drives a motor to move the photographing lens102for focusing or zooming under the control of the CPU306. The motor driver310also drives a motor opening or closing the mechanical shutter302in cooperation with the timing generator314under control of the CPU306. The operating portion307is composed of the power button108, the switching over dial109, the shutter release button110, the operating button105, the ENTER button105a, the CANCEL Button105band the zooming button106. The operating portion307sends signals to the CPU306to control actions of the digital still camera101. The shutter release button110sends a signal to take a picture. The mode switch sends a signal to select a mode from several modes, such as a photographing mode, a self-timer mode, a setting preference mode, a reproduction mode and so on. The audio reproduction device308announces an abnormality and a way to deal with the abnormality by voice when the abnormality occurs. It also announces a way to use the digital still camera101to help a users operation, or tells the time to shoot at the self-timer mode. The memory card320is an IC memory type memory with built-in semiconductor nonvolatile memory such as a flash-memory (called a small card). The digital still camera101uses the memory card320as a detachable external memory. The memory card320is attached into the slot111of the digital camera detachably. The memory card320stores JPEG compressed image data, as a taken picture, out of the RAM305through the memory controller316under control of the CPU306.

The CPU306controls each device described above and commands a normal procedure to take a picture. The CPU306also detects an abnormality of the mechanical shutter302based on a difference between at least two fields transmitted from the CCD solid image-capturing device301by comparing exposure amounts of these fields. The ROM309stores programs executed by the CPU306to control each device of the digital still camera101.

InFIG. 3, the CCD solid image-capturing device301converts an optical image received on the receiving surface through the photographing lens102to a frame of electric signals, and generates a frame of analog image signals corresponding to the optical image.FIG. 4explains a way to transmit the analog image signals from the CCD solid image-capturing device301. The CCD solid image-capturing device divides the frame of analog image signals into three fields, and transmits the three fields serially. The front-end signal-processing unit303converts the transmitted analog image signals to digital image signals with correlated double sampling by CDS circuit311, auto gain control by AGC circuit312and analog-digital conversion by A/D converter313. The front-end signal-processing unit303sends the digital image signals to the signal-processing IC304. The signal-processing IC304receives the digital image signals through the CCD interface315and sends the signals to RAM305through the memory controller316. At this time, the CCD interface315sums up each signal value of R (red), Gr (green in red line), Gb (green in blue line) and B (blue), respectively, for each divided area of a frame and for each field of digital image signals. For instance, we can divide a frames to 256 areas by sixteen horizontally and vertically.

The CPU306uses the sum to figure out a control-value such as a control-value for auto white balance. The signal-processing IC304converts a raw RGB-format data, having all three fields of a frame transmitted and stored in the RAM305, to YUV-format data with YUV converter319. YUV is the color space expressed by the luminance component (the brightness) Y and the chrominance (color) components U, V. Then the signal-processing IC304sends the YUV-format data to the RAM305through the memory controller316again. During this conversion, the YUV converter319uses the control-value figured by the CPU306. And then the signal-processing IC304reads the YUV-format data out of the RAM305once again and compresses the data to JPEG compression format data with image compressor318and sends the data back to the RAM305. The CPU306adds header data to the JPEG compression format data, formats the data as formatted data such as Exif (Exchangeable image file format) data and stores the data into the memory card320. Exif data includes metadata such as information about a photographing condition.

FIG. 4is a schematic diagram showing an order to transmit each field when the CCD solid image-capturing device301transmits a frame of image signals by divided three fields as an interlace-transmission. The CCD solid image-capturing device301divides a frame of image signals into three fields by grouping each three lines vertically and transmits them serially in three times. As shown in the timing chart ofFIG. 5, the mechanical shutter302closes when an exposure has finished. Thus the mechanical shutter2shuts incoming light from exposure of the receiving surface of the CCD solid image-capturing device301. Then there is no difference between each exposure time of field when the mechanical shutter302shuts normally.

On the other hand, some difference comes up between each exposure time of field when the mechanical shutter2fails to shut, as shown inFIG. 6. In detail, the second field is exposed while the first field is being transmitted, which makes the exposure time of the second field longer than the exposure time of the first field by the transmitting time of the first field. Additionally, the third field is exposed while the first and second field are being transmitted, which makes the exposure time of the third field longer than exposure times of the first and the second field by the transmitting time of the first and second field. Therefore the exposure time of the third field is the longest in the output of the CCD solid image-capturing device301. Thus the value of the third field, exposed for the longest time, becomes the highest level in the output of the CCD solid image-capturing device301. This difference makes a difference of RGB sums figured by the signal processing IC304between each field. The CPU306detects a difference of exposure time when it finds that a difference of the RGB sum is bigger than a threshold value. Then it commands the display device104to indicate an abnormality and a way to deal with the abnormality through the display device interface317. And it commands audio output device308to play sounds for alert such as a beep.

The exposure time of the first field is different from the exposure time of the second and third field when the mechanical shutter302delays shutting, as shown inFIG. 7. In detail, the second and the third field are exposed after the first field starts to be transmitted. It makes the exposure time of the second and third field longer than the exposure time of the first field by the delayed time of the mechanical shutter302. Therefore, the exposure time of the second and the third field are the longest in the output of the CCD solid image-capturing device301. Thus, the second and the third field, exposed for longer time, have a higher level than the first field. This difference also makes a difference in RGB sum figured by the signal processing IC304between each field. The CPU306detects a difference in exposure time when it finds that a difference of the RGB sums is bigger than a threshold value. Then it commands the display device104to indicate an abnormality and a way to deal with the abnormality through the display device interface317. And it commands audio output device308to play sounds for alert such as a beep.

In this embodiment, an abnormality is detected by comparing levels of the sums of each color area of the elementary color filter transmitted from the CCD solid image-capturing device301. However, an abnormality can alternatively be detected by the CPU309reading a data stored in the RAM305and comparing levels thereof. An abnormality can also be detected by comparing levels of averages of the similar areas. An abnormality can be detected by comparing levels of sums or averages of brightness derived from raw RGB format data.

The above embodiment utilizes a three-fields interlace-transmission, however, an abnormality can be detected in a case of two-fields interlace transmission, or greater than three fields interlace-transmission in the same manner. Furthermore, the above embodiment utilizes a CCD solid image-capturing device301with a color filter, however, the present invention can be used with a monochrome CCD.

For more detail, several more preferred embodiments are described below.

For instance, a difference of exposure amount due to a difference in exposure time also happens when light leaks into a light path to an image-capturing device because of breakage or defect of an optical part such as lens body103. In this case, the difference between the first field and the third field is biggest in a three-fields transmission. Therefore, the abnormality can be found by estimating data of first and second fields or the difference between the first and third fields. In this case, the data of the first and the third fields are utilized. However, the abnormality can alternatively be found by comparing the first and the second fields, or the second and the third fields.

An abnormality can be detected by comparing any pair of the three fields when the mechanical shutter302does not shut at all, as described above. This is because each two of exposure amounts of three fields are different. However, an abnormality cannot be detected by comparing the second and the third fields when the mechanical shutter302delays shutting a little bit as shown inFIG. 7. But, an incorrect timing of the mechanical shutter302can be determining by comparing the second and the third fields after an abnormality is found by comparing the first and the second fields or the first and the third fields.

For more accurate detection of an abnormality, the sums of data of a plurality of specified areas in the compared fields can be used. If only one area is specified as the area of interest and, for instance, the value of the area is so big that it is saturated, then cannot be detected. For dealing with such situation, one frame is divided into 256 areas by sixteen horizontal rows and sixteen vertical columns, and R, G and B values are respectively summed up in each of the 256 areas. The CPU306chooses four areas at the corners and five areas at the center and compares the fields. Such a procedure prevents the problem of saturation. Alternatively, the sums of brightness outputted by the YUV converter319can be used.

Alternatively average values can be used instead of sums. The CPU can process such values quicker because the average value has fewer digits than the sum, thereby reducing overhead in data transmission.

The R, G and B values are respectively summed as described above, and the most sensitive color is used in comparing the values. Such a procedure allows for the detection of a slight leak of light. The R, G and B values can also be compared independently. For instance, if a photographing subject is blue, the data will be too big, or the green and red data will be too small. To compare all color data of R, G and B independently, allows for the detection of an abnormality independent of the color of photographing subject. Or, the most and the least sensitive color both can be used in comparing the data. An abnormality can be detected by using the least sensitive color even if the most sensitive color is saturated.

An abnormality can be detected in the same way described above in the case of a CCD solid image-capturing device301with a complementary color filter system, as well as with the filter of an elementary color system.

As described above, the biggest difference is usually the difference between the first and the last field in a frame when the difference of exposure time exists. Therefore, an abnormality can be detected by comparing the first and the last fields.

The threshold value for detecting abnormality should be changed depending on a specified exposure time for photographing. InFIG. 6, the longer the exposure time, the less influence of the difference of the exposure time. Thus, a threshold value should be reduced for detecting abnormality when the exposure time is long. Furthermore, if the specified exposure time is too long, it is difficult to determine whether the difference comes from just noise or the difference of exposure time. Therefore, detection of abnormality should not be performed. For instance, the threshold value is specified with a larger value in order not to detect abnormality substantially.

Alternative ways can be used to inform a user of the occurrence of an abnormality, as described below. A camera, such as a digital still camera, usually has a display device. The display device can be used to indicate an abnormality and a way to deal with the abnormality such as a way to contact a repairer. However, when a user turns the display device off or does not see the display, then an audio output device308can also be used to beep or to announce a guide in order to avoid the user failing to recognize that an abnormality exists.

The present invention thus also includes a computer-based product which may be hosted on a storage medium and include instructions which can be used to program a microprocessor to perform a process in accordance with the present invention. This storage medium can include any type of disk including floppy disks, optical disks, CD-ROMs, magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, flash memory, magnetic or optical cards, or any type of media suitable for storing electronic instructions.

This patent specification is based on Japanese patent application, No. JPAP2003-421498 filed on Dec. 18, 2003, in the Japanese Patent Office, the entire contents of which are incorporated by reference herein.