JP4342926B2 - Image input method and image input apparatus - Google Patents

Description

  The present invention relates to an image input method and an image input apparatus such as an electronic still camera, and more particularly to an image input method and an image input apparatus that perform long exposure.

  Normally, when imaging a subject with insufficient light quantity, long exposure is performed by opening the shutter for a long time in order to increase the charge accumulation time of the image sensor in the image input device. This is because it is possible to capture an image without using an auxiliary illumination such as a strobe or image the starry sky even under low illumination. However, when a long exposure is performed, a dark current, which is a kind of noise, is generated on the image sensor, causing problems such as a narrow dynamic range and noise in the obtained captured image. .

  As a countermeasure against this problem, for example, the following imaging method is described in Patent Document 1 below. First, the total charge accumulation time for securing the brightness necessary for imaging the subject, that is, the imaging time is obtained. Next, the imaging time of one image is set to a short time such that an increase in dark current does not cause a problem, and each image is captured at the set time. Imaging is performed until the total imaging time of each image reaches the total imaging time obtained earlier. Finally, the final image data is obtained by integrating the obtained image data.

JP-A-9-18793 (for example, paragraphs 0063 to 0065)

  However, in the above method, for example, when the total imaging time is 128 seconds, the time when the increase in dark current is not a problem is 2 seconds, and the memory capacity for storing images is 8 bits = 256 gradations, 128 (seconds) / 2 (seconds / sheet) = 64 (sheets) images are required. However, 256 (gradation) / 64 (sheet) = 4 (gradation / sheet) due to memory capacity limitations, and only four gradations can be assigned to one sheet. Even if 64 images of such a low gradation of 4 gradations are integrated, the obtained image is still of a low gradation or an image different from the original image.

  For example, when the memory capacity is 8 bits = 256 gradations and the time when the increase in dark current is not a problem is 1 second, the required number of images is 256 (gradation) / 1 (gradation / sheet) = 256. (Sheets). Accordingly, the number of gradations assigned to one image is only 256 (gradation) / 256 (sheets) = 1 (gradation / sheet). Furthermore, if the total imaging time required for securing the light amount is longer than 256 seconds, the number of gradations that can be assigned to one image is 1 or less, and imaging cannot be performed. This means that the amount of light of the subject is very small and a dark image cannot be captured.

  As described above, in the conventional image input method, the number of images to be captured is determined after measuring the light amount of the subject. Therefore, when capturing a dark subject with insufficient light amount, the obtained image has a low gradation or the original image. In some cases, imaging may not be possible. The present invention has been made to solve such a problem, and an image input method and image input capable of obtaining high gradation image data even with the same memory capacity as that of a conventional image input apparatus. An object is to provide an apparatus.

The present invention provides a photometric step for measuring the amount of light of a subject and outputting a photometric result;
A first imaging time output step for outputting an imaging time based on the photometric result;
A second imaging time output step for outputting an imaging time per image from the imaging time;
A first bright image capturing step of opening a mechanical shutter and capturing a bright image at an image capturing time per image;
A first memory calculation step of accumulating the bright image data of the captured bright image in a memory and storing it as corrected image data;
Determining the brightness of the image based on the corrected image data, and forcibly ending the imaging of the bright image based on the result of the determination ,
The corrected image data is obtained by subtracting dark image data of a dark image captured at the imaging time per image from the bright image data captured in the first bright image capturing step. The cumulative addition is stored in the memory .

  According to the present invention, high gradation image data can be obtained even with a limited memory capacity.

Embodiment 1 FIG.
The image input method according to the present invention measures the amount of light of a subject and outputs the entire exposure time necessary for obtaining a bright image from the measurement result. Then, the output exposure time is divided into a plurality of times based on a predetermined number of captured images, and bright image data is acquired at each division time. Each dark image is also picked up based on the output divided time. Finally, the final image data is obtained by subtracting the dark image data from the bright image data.
Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.

FIG. 1 is a block diagram illustrating a configuration of an image input device 20 according to the first embodiment. The outline of the image input process will be described with reference to FIG.
First, the process starts by depressing the release button in the operation unit 10. The depression of the release button is input from the operation unit 10 to the system controller 7. The system controller 7 estimates the drive timing of the CCD 3 via a timing generator (hereinafter referred to as “TG”) 6, drives the shutter drive unit 8, and opens and closes the mechanical shutter 1. The exposure time during which the mechanical shutter 1 is opened is determined by the system controller 7 based on the subject output from the photometry unit 9 and the amount of light around it. An analog image signal of a subject imaged on the CCD 3 via the lens 2 passes through a correlated double sampling unit (hereinafter referred to as “CDS”) 4 and an A / D converter 5, and is then stored in an internal memory 11. It is stored as original image data above. The original image data stored in the internal memory 11 is subjected to image processing such as colorization and correction in the system controller 7 having an image processing function. The image data subjected to the image processing is displayed on a display unit 13 constituted by an LCD or the like, or recorded on a recording medium 12 capable of transferring data to the outside of the apparatus.

  Note that the measurement of the amount of light in the subject and the surrounding area performed by the photometric unit 9 can also be performed by the CCD 3. In other words, the amount of light incident on the CCD 3 is calculated from image data output through the CDS 4 and the A / D converter 5. In addition, the photometry method includes other methods such as priority photometry and multi-pattern photometry, but any method may be adopted in the present invention.

  FIG. 2 is a diagram showing a flow of image input processing in the first embodiment. In the image processing flow, the step of determining the exposure time of the bright image in steps 1 and 2, the step of acquiring dark image data from step 3 to step 9, and the bright image data from step 10 to step 14 are acquired. It is roughly divided into processes. The dark image data is used for detection of fixed pattern noise unique to each image input device. Hereinafter, it demonstrates in detail using FIG.

  In this embodiment, for example, the memory capacity is 8 bits = 256 gradations, the short time in which the dark current is not a problem is 2 seconds, and the total imaging time required to secure the light amount is 128 seconds. In such a condition, if the conventional image input method is used, only four gradation images can be obtained per sheet as described above.

  First, by depressing the release button in the operation unit 10, the following series of processes starts. The photometric device 9 measures the amount of light in the subject and its surroundings, and the system controller 7 calculates an exposure time T that can secure the amount of light necessary for imaging (step 1). Now, as explained above, T = 128 seconds. Further, due to hardware restrictions such as the memory capacity of the A / D converter 5, a predetermined number n of images is used to secure the exposure time of each bright image Ai, that is, the amount of light in one image. The accumulation time Tn is obtained as T / n (step 2). If n = 8, Tn = 128 (seconds) / 8 (sheets) = 16 (seconds / sheet). The gradation of one image data is 256 (gradation) / 8 (sheet) = 32 (gradation / sheet). This means that it is possible to obtain image data with 8 times the gradation of the conventional image data.

  It should be noted that the number of gradations of image data to be acquired can be determined in advance, and the number n of captured images can be determined from the number of gradations and the memory capacity. For example, when the number of gradations of one piece of image data is 64 (gradation / sheet) and the memory capacity is 10 bits = 1024 (gradation), the number of captured images n = 1024 (gradation) / 64 (gradation / sheet) = 16 (sheets).

  Next, step 3 to step 7, which are dark image data acquisition steps, will be described. The dark image data is used for detection of fixed pattern noise unique to each image input device. First, the mechanical shutter 1 is closed (step 3), and a dark image is captured at the accumulation time Tn calculated in step 2 (step 4). The acquired dark image data Bj is stored in the memory B by the operation described in FIG. 4 (M11) (step 5). The memory B is a certain area in the internal memory 11 of FIG. Similarly, a memory A and a memory B, which will be described later, indicate a certain area in the internal memory 11.

  Next, it is determined whether or not the number of captured dark images has reached m−1 (step 6). If not, the process returns to step 4 (step 7), and further dark images are captured. The number m of dark images is determined in advance by hardware restrictions such as the memory capacity of the A / D converter 5 in the same manner as the number n of bright images. When the number of captured dark images has reached m (step 8), as described in FIG. 4 (M12), the dark image data Bm newly output from the A / D converter 5 and the memory After adding up to m−1th dark image data stored in B, and dividing the added data by the number m of images to be captured, the calculation result is stored in memory B as average dark image data Bave. Now, for example, if m = 6 sheets, the time required to obtain the average dark image data Bave is 16 (seconds / sheet) × 6 (sheets) = 96 (seconds) or more.

  Next, step 10 to step 15 which are processes for obtaining bright image data will be described. After the mechanical shutter 1 is opened (step 10), a bright image is taken at the accumulation time Tn calculated in step 2 (step 11). Further, as shown in FIG. 4 (M13), the average dark image data Bave is subtracted from the bright image data Ai newly output from the A / D converter 5, and the correction already stored in the memory A is performed. After adding the image data, it is stored in the memory A as new corrected image data Yi (step 12). The corrected image data Yi read from the memory A is subjected to image processing by the system controller 7 having an image processing function, and then sent to the display unit 13 and displayed as an image (step 13). In step 14, it is determined whether or not the number of bright images Ai taken has reached n. If not, the procedure returns to step 10 (step 15), and further bright images are taken. If the number of bright images picked up reaches n, the process ends. At the stage where a series of processing is completed, n pieces of corrected image data Yi are accumulated, and the long-exposure image data Yadd is stored in the memory A, and the image data Yadd is displayed on the display unit 13. Note that Tn · n = 128 seconds or longer in the image data acquisition step.

  FIG. 3 is a timing chart showing the operation of the image input apparatus and the timing of acquiring bright image data and dark image data. As shown in FIG. 3A, the image input apparatus starts operation by pressing the release button. The system controller 7 determines the total exposure time from the output from the photometry device, and calculates the accumulation time Tn (steps 1 and 2). As shown in FIG. 3B, after the mechanical shutter 1 is closed, as shown in FIG. 3C, m dark images are taken at the imaging time Tn. The captured dark image is output to the memory B as dark image data Bj via the A / D converter 5, as shown in FIG. 3 (d) (steps 3 to 9). Next, the mechanical shutter 1 is opened, and n bright images are taken at the charge accumulation time Tn. The captured bright image is output to the memory A as the bright image data Ai through the A / D converter 5 (steps 10 to 15).

  In the image input method according to the present embodiment, as shown in FIG. 4 (M13), the bright image data A1 to An are not input to the memory A by a single process, but are stored in the order in which charges are accumulated. Accumulated in A. Therefore, the image data displayed on the display unit 13 becomes brighter with time as shown in FIG.

  Thus, in the image input method according to the present embodiment, for example, even if the memory capacity is 8 bits = 256 gradations, the number of images to be captured is determined as n = 8 in advance so that the image can be captured with this memory capacity. By doing so, it is possible to obtain image data having a high gradation of 32 gradations per image. That is, even with a limited memory capacity, high gradation image data can be obtained.

  The point here is that the conventional image input method determines the number of images to be captured after measuring the amount of light of the subject, whereas the image input method according to the present embodiment determines the number of images to be captured in advance. There is a point. As a result, even a dark subject that cannot be imaged conventionally can be imaged.

  It should be noted that the image input method according to the present embodiment is not limited to the numerical values used in the description, and it is needless to say that it can be applied to any memory capacity and required number of gradations.

  In the timing chart shown in FIG. 3, after the dark image data Bm is taken into the memory B, the mechanical shutter 1 is opened, and the charge accumulation of the bright image and the taking of the bright image data A1 are started. However, as shown in FIG. 6, after the dark image is captured, the mechanical shutter 1 may be opened to capture the bright image without waiting for the dark image data Bm to be taken into the memory B. Thereby, it is possible to further shorten the entire imaging time.

Embodiment 2. FIG.
In this embodiment, a description will be given of an image input method that can cope with an increase in the amount of light in the subject and its surroundings. In other words, in the image input method described in the first embodiment, when the amount of light from the subject increases during the bright image capturing, the finally obtained image may become too bright. In the present embodiment, an image input method that can cope with such a phenomenon that the amount of light increases during bright image capturing will be described.

  FIG. 7 is a diagram illustrating a flow of image input processing according to the second embodiment. The image processing flow includes the steps of determining the exposure time of the bright image in steps 21 and 22, the step of acquiring dark image data from step 23 to step 29, and the bright image data from step 30 to step 36. It is roughly divided into processes. The difference from the flow of the image input process in the first embodiment is that step 34 is added so that the capture of bright image data can be forcibly terminated.

  In step 21, the amount of light of the subject is measured and an appropriate exposure time T is calculated. However, thereafter, the amount of light from the subject increases, and when a bright image is captured, the exposure time may be shorter than the calculated exposure time T. In such a case, an image with appropriate brightness is obtained by forcibly terminating the capture of the bright image data while confirming gradually brightening image data as shown in FIG. 5 by the display unit 13 (step 34). Data can be obtained. It is also possible to forcibly end bright image data capture by a command from the system controller 7 by causing the system controller 7 to confirm the brightness of the image data Yadd.

Embodiment 3 FIG.
In this embodiment, a description will be given of an image input method that can cope with a case where the amount of light in the subject and its surroundings increases or decreases. That is, in the second embodiment, the image input method that can be used only when the amount of light of the subject increases after calculating the appropriate exposure time T has been described. However, in the present embodiment, the light amount of the subject increases after the calculation of the appropriate exposure time T. As a result, the obtained image data is too bright, or the light amount of the subject decreases after the calculation of the appropriate exposure time T. An image input method capable of handling the case will be described.

  FIGS. 8.1 and 8.2 are diagrams showing a flow of image input processing in the third embodiment. The image processing flow includes a step of determining the exposure time of the bright image in steps 41 and 42, a step of acquiring dark image data in steps 43 to 49, and a step of acquiring bright image data in steps 50 to 56. The process is roughly divided into steps 57 to 65 for adjusting the brightness of the image data. The difference from the flow of the image input process in the second embodiment is that a process for adjusting the brightness of the image data in steps 57 to 65 is added.

  9 (M21) to (M25) show memory calculation operations in each step of the image processing flow according to the third embodiment shown in FIGS. 8.1 and 8.2. 9 (M21), (M22), and (M23) are memory calculation operations in steps 45, 49, and 52, respectively. Steps 45, 49, and 52 correspond to steps 5, 9, and 12 in FIG. 9 (M21), (M22), and (M23) are the same as those in FIGS. 4 (M11), (M12), and (M13), and thus detailed description thereof is omitted.

  First, until step 56, image data Yadd is once acquired. However, for example, after the exposure time T is calculated, the amount of light of the subject decreases, and the obtained image data may be too dark. If it is expected that the amount of light of the subject will increase and the resulting image will be bright, the bright image data can be forcibly terminated in step 54. However, as a result of the forced termination not being performed at an appropriate timing, the obtained image data may be too bright. In such a case, the brightness of the image data is adjusted in steps 57 to 65 described below.

  First, it is determined whether the brightness of the obtained image data is appropriate (step 57). If appropriate, terminate the process. If it is determined that the image data is too bright, an operation for reducing the brightness of the image data is performed as shown in steps 58 to 61. That is, first, a bright image is captured at the accumulation time Tn (step 58). Then, as shown in FIG. 9 (M24), the average dark image data Bave stored in the memory B is subtracted from the bright image data Ai newly output from the A / D converter 5, and this subtraction result is obtained. Then, the brightness of the corrected image data Y is lowered by subtracting it from the corrected image data already stored in the memory A (step 59). Since the corrected image data Y is displayed on the display unit 13 (step 60), it is determined whether or not the brightness is further adjusted while checking the image content (step 61).

  If it is determined in step 57 that the image data is too dark, as shown in steps 62 to 65, an operation for increasing the brightness of the image data is performed. That is, a bright image is captured at the accumulation time Tn (step 62). Then, as shown in FIG. 9 (M25), the average dark image data Bave stored in the memory B is subtracted from the bright image data Ai newly output from the A / D converter 5, and the memory A has already been subtracted. The brightness of the corrected image data Y is increased by adding to the corrected image data stored in (step 63). Since the corrected image data Y is displayed on the display unit 13 (step 64), it is determined whether or not the brightness is further adjusted while checking the image content (step 65).

  Thus, in the image input method according to the present embodiment, the brightness of the image data can be adjusted. That is, even when the obtained image data is too bright or too dark, it is possible to adjust the brightness of the image data while checking the display unit 13, so that the image data has an appropriate brightness. Is possible. It is also possible to forcibly end bright image data capture by a command from the system controller 7 by causing the system controller 7 to confirm the brightness of the image data Yadd.

Embodiment 4 FIG.
In this embodiment, an image input method capable of setting the number m of dark images taken in consideration of the temperature of the CCD 3 will be described.

  In the first embodiment, it has been described that the number m of dark image images is determined in advance from the S / N of the image signal output from the CDS 4, the bit accuracy of the A / D converter 5, and the like. However, it is conceivable that the temperature of the CCD 3 changes when the temperature around the device changes or due to the heat generated by the operation of the device. As shown in FIG. 10, it is known that dark current, which is a kind of noise, increases exponentially with increasing temperature. Therefore, the number of captured dark images used for detecting fixed pattern noise due to dark current or the like may be increased or decreased according to the temperature change. That is, by setting the number m of dark images to be taken into consideration, the accuracy of the dark image data Bave is improved and the accuracy of the finally obtained image data Yadd is also improved.

  FIG. 11 is a timing chart showing the operation of the image input apparatus according to the fourth embodiment and the timing of obtaining bright image data and dark image data. As shown in FIG. 11A, the operation is first started by pressing the release button. Next, as shown in FIG. 11B, after the mechanical shutter 1 is closed, a sample image is captured at an imaging time C. The imaging time C is the shortest time when the electronic shutter of the CCD 3 operates. Then, the screen average luminance value P1 of all pixels in the obtained sample image data C1 is calculated. The calculated average luminance value P1 is compared with, for example, P0 measured and recorded at 25 ° C. before shipment of the image input device, and the number m of dark image data captured is determined from the difference value between P0 and P1. decide. Then, m dark images are taken, and m dark image data Bj are obtained as shown in FIG. Subsequent bright image capturing and bright image data acquisition are the same as in the case shown in FIG.

  When obtaining the number of dark images to be picked up from the average luminance values P0 and P1, the number of picked-up images m is determined by calculation from the difference value between P0 and P1, but a lookup table is obtained from the difference value between P0 and P1. The image pickup number m may be determined by referring to it.

  Further, in FIG. 11, the case where the number of times of capturing the sample image has been described, but as illustrated in FIG. As a result, a plurality of image data Cl can be used, the accuracy of the average luminance value P1 is improved, and the number m of dark images can be determined.

  Furthermore, although the imaging time C is the shortest time when the electronic shutter of the CCD 3 operates, it may be shorter than the imaging time of the dark image or the bright image, and may be longer than the minimum operating time of the electronic shutter. .

  As described above, in the image input method according to the present embodiment, the number m of dark images that can be taken can be set in consideration of the temperature of the CCD 3, and the accuracy of the obtained dark image data is improved. The accuracy of Yadd is also improved.

Embodiment 5 FIG.
In this embodiment, an image processing method in consideration of memory capacity in the image input methods described in the first to fourth embodiments will be described.

  In Embodiments 1 to 4, as shown in FIG. 4 (M11) and FIG. 9 (M21), the dark image data Bj is simply added to the memory B, and then finally divided by the number of images to be picked up m to obtain the average darkness. The image data Bave is obtained. Therefore, there is a high possibility that a phenomenon of “digit overflow” in which the memory capacity is insufficient during the simple integration of the dark image data will occur. When such a phenomenon called “overflow” occurs, a memory operation such as increasing the number of bits allocated to the operation becomes necessary. For such a memory operation, more time than the normal calculation time is required. Therefore, this problem is addressed by the following method.

  FIG. 13.1 and FIG. 13.2 are diagrams showing the flow of the image input process in the fifth embodiment. The image processing flow includes a step of determining the exposure time of the bright image in steps 71 and 72, a step of acquiring image data from steps 73 to 79, and a step of acquiring dark image data from step 80 to step 85. The process is roughly divided into steps 86 to 91 for obtaining bright image data. In the present embodiment, steps 73 to 79 and steps 80 to 85 and FIG. 14 (M31) to (M35) are the image processing flow of the present embodiment shown in FIG. 13.1 and FIG. 13.2. The memory calculation operation in each step is shown. 14 (M31), (M32), (M33), (M34), and (M35) are memory calculation operations in steps 75, 79, 81, 85, and 88, respectively. FIG. 15 is a timing chart showing the operation of the image input apparatus according to the fifth embodiment and the timing of obtaining bright image data and dark image data.

  Hereinafter, the flow will be described. First, as shown in FIG. 15A, first, the operation is started by pressing the release button. Next, the exposure time of the bright image is determined (steps 71 and 72). Then, as shown in FIG. 15B, the mechanical shutter 1 is closed (step 73), and as shown in FIG. 15C, the sample image is taken in the shortest charge accumulation time during which the electronic shutter of the CCD 3 operates. Do. Next, the number m of dark image data Bj to be captured is determined from the sample image data C1, and m images are also captured for the sample image Ck (steps 74 to 79). At this time, the memory calculation in step 75 is stored in the memory C by adding the data already stored in the memory C to the newly input sample image data Ck as shown in FIG. 14 (M31). The

  As shown in FIG. 14 (M32), the memory operation relating to the image data Cm (step 79) includes the sample image data Cm newly output from the A / D converter 5 and the m−1 stored in the memory C. The sample image data up to the first sheet is added, and the added data is divided by the number m of captured images, and the calculation result is stored in the memory C as average sample image data Cave.

  Since the process of acquiring dark image data (steps 80 to 85) is basically the same as that of the first embodiment, detailed description thereof is omitted. However, in the memory operation in step 81, the average sample image data Cave is subtracted from the dark image data Bj newly output from the A / D converter 5, as shown in FIG. Are stored in the memory B as dark image data Bj. Further, in the memory operation in step 85, as shown in FIG. 14 (M34), the average sample image data Cave is subtracted from the dark image data Bm newly output from the A / D converter 5, and the subtraction result is obtained. The dark image data already accumulated in the memory B is added, divided by the number m of captured images, and stored in the memory B as dark image data Bj. By this operation, image data Bave is obtained.

  Since the process of obtaining bright image data (steps 86 to 91) is the same as that of the first embodiment, its details are omitted.

  Thus, in this embodiment, since the dark image data obtained by subtracting the sample image data Cave is stored in the memory B, the capacity of the memory B is smaller than that in the first embodiment. ”Can be reduced.

Embodiment 6 FIG.
In this embodiment, the accumulation time for capturing a dark image is changed.

  That is, in the first to fifth embodiments, each dark image is captured with the charge accumulation time as Tn. However, as shown in FIG. 16, the accumulation time is Tp = Tn × m. It is also possible to perform imaging by an imaging operation. By adopting such an imaging method, the operation of opening and closing the electronic shutter of the CCD 3 becomes unnecessary, so that the blank period between the dark images Bj and Bj + 1 can be reduced, so that the overall exposure time can be reduced. It becomes possible.

1 is a block diagram illustrating a configuration of an image input device according to Embodiment 1. FIG. FIG. 5 is a diagram showing a flow of image input processing in the first embodiment. 6 is a diagram illustrating operation timing of the image input apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating an operation of memory calculation in the first embodiment. FIG. 6 is a diagram illustrating a time lapse of an image displayed on the display unit in the first embodiment. FIG. 6 is a diagram illustrating operation timing of the image input apparatus according to Embodiment 1. FIG. FIG. 10 is a diagram illustrating a flow of image input processing in the second embodiment. FIG. 10 is a diagram illustrating a flow of image input processing in the third embodiment. FIG. 10 is a diagram illustrating a flow of image input processing in the third embodiment. FIG. 10 is a diagram illustrating an operation of memory calculation in the third embodiment. It is a figure which shows a response | compatibility with dark current and temperature. FIG. 20 is a diagram illustrating operation timing of the image input apparatus according to the fourth embodiment. FIG. 20 is a diagram illustrating operation timing of the image input apparatus according to the fourth embodiment. FIG. 20 is a diagram illustrating a flow of image input processing in the fifth embodiment. FIG. 20 is a diagram illustrating a flow of image input processing in the fifth embodiment. FIG. 20 is a diagram illustrating an operation of memory calculation in the fifth embodiment. FIG. 20 is a diagram illustrating operation timing of the image input apparatus according to the sixth embodiment. FIG. 20 is a diagram illustrating operation timing of the image input apparatus according to the sixth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mechanical shutter, 2 Lens, 3 CCD, 4 CDS, 5 A / D converter, 6 Timing generator, 7 System controller, 8 Shutter drive part, 9 Photometry part, 10 Operation part, 11 Internal memory, 12 Recording medium, 13 Display unit, 14 compression / decompression unit, 20 image input device

Claims (6)

A metering step that measures the amount of light of the subject and outputs the metering result; and
A first imaging time output step for outputting an imaging time based on the photometric result;
A second imaging time output step for outputting an imaging time per image from the imaging time;
A first bright image capturing step of opening a mechanical shutter and capturing a bright image at an image capturing time per image;
A first memory calculation step of accumulating the bright image data of the captured bright image in a memory and storing it as corrected image data;
Determining the brightness of the image based on the corrected image data, and forcibly ending the imaging of the bright image based on the result of the determination ,
The corrected image data is obtained by subtracting dark image data of a dark image captured at the imaging time per image from the bright image data captured in the first bright image capturing step. An image input method characterized by being accumulated and stored in the memory . The imaging time per image output in the second imaging time output step is obtained by dividing the imaging time output in the first imaging time output step by a predetermined number of images. The image input method according to claim 1, wherein: When it is determined that the corrected image data is brighter than a predetermined brightness,
A second bright image capturing step of opening a mechanical shutter and capturing one more bright image at an image capturing time per image;
The brightness of the corrected image data is reduced by subtracting the image data captured in the second bright image capturing step from the image accumulated and added to the memory by the first memory calculation step and storing the image data in the memory. A second memory calculation step to lower;
With
When it is determined that the corrected image data is darker than a predetermined brightness,
A third bright image capturing step of opening a mechanical shutter and capturing one more bright image at the image capturing time per image;
The image data captured in the third bright image capturing step is added to the image accumulated and stored in the memory in the first memory calculation step, and the brightness of the corrected image data is stored in the memory. A third memory calculation step to raise and
The image input method according to claim 1 or 2, characterized in that it comprises a. For the image calculated in the second memory calculation step, the mechanical shutter is closed from the bright image captured in the second bright image capturing step, and the dark image captured in the imaging time per one image is subtracted. the image input method according to claim 3, characterized in <br/> be images. A photometric means for measuring the amount of light of the subject and outputting a photometric result;
Imaging means for converting the optical image of the subject into electrical image data;
Storage means for storing image data output from the imaging means;
Based on the output of the photometric result and a predetermined number of images, the imaging time per image is determined, the mechanical shutter is opened, and the image is captured at the imaging time per image and output from the imaging means. Image processing means for accumulating the bright image data of the bright image to be added to the corrected image data stored in the storage means and storing it as corrected image data in the storage means,
The image processing means determines the brightness of the corrected image data, forcibly ends bright image capturing based on the determination result,
The corrected image data stored in the storage unit by the image processing unit is obtained by subtracting dark image data of a dark image captured at the imaging time per one image from the bright image data by closing a mechanical shutter. after, the storage means images input device you characterized in that it is stored in the storage means cumulatively adds the stored correction image data. When the image processing means determines that the corrected image data is brighter than a predetermined brightness,
A further bright image is captured by the imaging means, and the brightness of the corrected image data is lowered by subtracting the bright image data of the bright image from the cumulatively added corrected image data stored in the storage means,
When the image processing means determines that the corrected image data is darker than a predetermined brightness,
A further bright image is picked up by the image pickup means, and the bright image data of the bright image is added to the corrected correction image data stored in the storage means to increase the brightness of the corrected image data. The image input device according to claim 5 .

Images