JP2005159950A - Image input apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image input apparatus and method in which the optimal result of scanning is obtained by controlling a scanning speed if a photographic status of a negative film is over exposure. <P>SOLUTION: In the image input apparatus, a negative film is expressed as 403. In a pre-scanning, an image on the negative film is read by a CCD (405). The image is histogram-analyzed by an exposure condition judging unit (410) and it is judged whether the image is an overexposed image. The image judged as overexposed is scanned, in the case of a fine scanning, while decelerating the scanning speed by a scanning speed control unit. As a result, an image that has excellent gradations and reduced noise, is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image input apparatus and method, and more particularly to an image input apparatus and method for inputting image information recorded on a film as digital data.

  A conventional image input apparatus includes a film scanner for obtaining image information recorded on a film as digital data.

  FIG. 1 is a block diagram showing the overall configuration of a conventional film scanner.

  In FIG. 1, a film scanner includes a light source unit 101, a projection lens 102, an imaging lens 104, an image reading sensor 105 including a CCD (Charge Coupled Device), a signal amplifier 106 (AMP), and an A / D. A converter 107 (A / D), a lookup table converter 108 (LUT), a memory 109, an image analysis unit 110, an image conversion unit 111, and an I / O 112 are included.

  The light source unit 101 is a light source composed of a halogen lamp, a white fluorescent tube, or the like. The projection lens 102 is a lens for irradiating the light from the light source unit 101 as parallel rays onto a developed film (hereinafter simply referred to as “film”) 103 in which an image taken by a camera is recorded. The imaging lens 104 is an optical system for forming an image on the film 103 on the image reading sensor 105. Note that the projection lens 102 and the imaging lens 104 may be composed of a plurality of lens groups.

  The image reading sensor 105 is provided with R, G, and B color separation filters on the sensor, and converts light transmitted through the film 103 into R, G, and B electrical signals. As a result, the image information on the film 103 can be obtained as an electrical signal. The signal amplifier 106 is a signal amplifier that amplifies the signal from the image reading sensor 105. The A / D converter 107 converts the analog signal obtained from the signal amplifier 106 into a digital signal. The look-up table converter 108 performs gradation conversion such as gamma conversion on the image signal obtained from the A / D converter 107. The memory 109 stores the image signal obtained from the lookup table converter 108. The image analysis unit 110 analyzes an image obtained at the time of pre-scanning and determines an amplification factor that is a parameter given to the signal amplifier 106. The image conversion unit 111 automatically corrects the color balance for each of R, G, and B for the image data obtained from the memory 109. The I / O 112 is an interface for connecting a film scanner and a computer (not shown) (hereinafter referred to as “PC”).

  Next, an image reading operation in the film scanner will be described.

  In a general scanner, a document image is scanned twice (image reading), which are called pre-scan and fine scan, respectively. The pre-scan determines various parameters in the scan conditions for performing fine scan.

  Usually, when the user sets the film 103 on the film scanner, the pre-scan is automatically performed. In that case, the signal amplifier 106 is set to an amplification factor that does not cause an overflow even if an image photographed under any exposure condition is scanned. The pre-scan is performed at a low resolution because it is only used for user image confirmation by a monitor (not shown) on the film scanner, in addition to determination of the scan condition during fine scan.

  The look-up table converter 108 sets a pre-scan look-up table and performs pre-scan. That is, the look-up table converter 108 performs a negative to positive inversion process for any film type and any scene image. The result is once written in the memory 109 and sent to the image analysis unit 110.

  The image analysis unit 110 calculates feature quantities representing image characteristics such as the highest density, the lowest density, and the average density for each color for each image, and sets scan conditions during fine scanning based on the feature quantities. decide. For example, the image is classified into low density, normal density, high density, and maximum density by comparing the maximum density, minimum density, and average density with predetermined values, and the signal amplification factor is determined for each image. To set the signal amplifier 106. Further, the color balance is analyzed, a lookup table at the time of fine scanning is determined for each image so as to obtain an appropriate color balance, and the lookup table converter 108 is set.

  The image conversion unit 111 performs a simulation based on the result obtained by the image analysis unit 110 and generates an optimal pre-scan image. The generated result is sent to the memory 109. For example, the user can visually confirm the result of the simulation on the monitor of the PC connected to the I / O 112.

  Next, the signal amplifier 106 and the look-up table converter 108 are controlled using the parameters determined by the image analysis unit 110, and fine scanning is performed with high resolution. As a result, each image is scanned under optimum conditions, so that a fine scan image with a well-balanced brightness and gray balance can be obtained.

  The pre-scan image is subjected to image conversion twice in total by the look-up table converter 108 and the image conversion unit 111. On the other hand, the fine scan image is optimally amplified at the stage of an analog signal by the signal amplifier 106, and is subjected to gradation conversion only once by the look-up table converter 108 under the optimal conditions. Therefore, the input data width is larger than that of the pre-scan image, and an image with good gradation can be obtained. The fine scan image converted by the lookup table converter 108 is sent to the memory 109 and transferred to the PC via the I / O 112.

  However, in the above-described conventional film scanner, in the case of a negative film taken with overexposure, scanning is performed by increasing the amplification factor of the signal amplifier 106 in the fine scan. As a result, noise components on the film are also amplified, resulting in an image with coarse graininess.

In order to solve the problem, a method has been disclosed in which the density of an image at the time of pre-scanning is determined, and when the density is high, the scanning speed at the time of fine scanning is reduced (for example, see Patent Document 1). By reducing the speed, it is possible to capture in the optimum density range, and by increasing the amount of light irradiated to the CCD, the S / N ratio increases and an image with less noise can be obtained. Here, the image density means the average density of the image.
Japanese Patent Laid-Open No. 10-243174

  However, in this system, since the exposure state is determined and the scan speed is changed based only on the image density, scanning at an optimum speed may not be performed. This will be specifically described below with reference to the drawings. FIG. 2 is a diagram showing the relationship between density and histogram in a pre-scan image in a standard scene shot with overexposure. Ave means the average density of the image. In a standard scene, in the case of a negative film shot with overexposure, Ave is greater than a certain value. In this case, a fine scan is performed at a low scan speed. As described above, when a standard scene is shot with overexposure, an appropriate determination is made. As a result, since the data is captured in the range of density Min to Max in FIG. 2, an image with good gradation and less noise can be obtained. However, when a dark scene such as a night scene is photographed with overexposure, the method of Japanese Patent Laid-Open No. 10-243174 cannot make an appropriate determination. FIG. 3 shows the relationship between density and histogram in a pre-scan image taken with overexposure. In the case of an entirely dark scene, the average density value Ave is lower than Ave in FIG. For this reason, Ave becomes smaller than the specified value, so it is not determined that the exposure is overexposed, and fine scan is performed at a normal speed. As a result, in FIG. 3, the capturing is performed in the range from the density Min to the Max, and the high density portion above the Max is discarded. This is, for example, a light portion in a night view or a face portion when a person is photographed with a flash against a night view. If the data is truncated, the light part and the gradation of the face disappear and are destroyed.

  The present invention has been made in view of the above problems, and provides an image input apparatus and method capable of appropriately determining the exposure at the time of shooting and controlling the scanning speed at the time of fine scanning regardless of the scene and the subject. The purpose is to provide.

  In order to achieve the above object, an image input device according to claim 1 is an image reading device for irradiating light from a light source to a developed film using a light irradiation means and a line sensor. Obtained by reading means, scanning means for moving the film or sensor in order to read the entire image on the film by the image reading means, scanning speed control means capable of variably controlling the operation speed of the film or sensor, obtained by the image reading means An exposure condition determining unit that obtains a histogram of an image and determines an exposure condition at the time of image capturing using the histogram is provided, and the scanning speed is changed based on the determination result of the exposure condition.

  The image input device according to claim 2, wherein the developed film is irradiated with light from a light source, the image reading means for reading an image on the film using a line sensor, and the entire image on the film. In order to read the image by the image reading means, a scanning means for moving the film or sensor, a scanning speed control means capable of variably controlling the operation speed of the film or sensor, a histogram of the image obtained by the image reading means is obtained, and the histogram is obtained. Using an exposure condition determination means for determining an exposure condition at the time of image shooting, a mode selection means capable of selecting speed priority or image quality priority, and when image quality priority is selected, based on the determination result of the exposure condition, The scanning speed is changed.

  As described above in detail, according to the present invention, since the histogram is analyzed for each image at the time of pre-scanning, the exposure condition is judged from the result, and the fine scan is performed at a speed according to the exposure condition. Therefore, it is possible to obtain a good image with good gradation and high S / N ratio.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 4 is a block diagram showing the overall configuration of the film scanner of the present invention.

  In FIG. 4, the film scanner includes a light source unit 401, a projection lens 402, an imaging lens 404, an image reading sensor 405 including a charge coupled device (CCD), a signal amplifier 406 (AMP), and an A / D. It comprises a converter 407 (A / D), an image conversion unit 408, a memory 409, an exposure condition determination unit 410, a scanning speed control unit 411, and an I / O 412.

  The light source unit 401 is a light source composed of a halogen lamp, a white fluorescent tube, or the like. The projection lens 402 is a lens for irradiating light from the light source unit 401 as parallel rays onto a developed film (hereinafter simply referred to as “film”) 403 on which an image taken by a camera is recorded. The imaging lens 404 is an optical system for forming an image on the film 403 on the image reading sensor 405. Note that the projection lens 402 and the imaging lens 404 may be composed of a plurality of lens groups.

  The image reading sensor 405 has R, G, and B color separation filters mounted on the sensor, and converts the light transmitted through the film 403 into R, G, and B electrical signals. As a result, the image information on the film 403 can be obtained as an electrical signal. The signal amplifier 406 is a signal amplifier that amplifies the signal from the image reading sensor 405. The A / D converter 407 converts the analog signal obtained from the signal amplifier 406 into a digital signal. The image conversion unit 408 performs gradation conversion such as gamma conversion on the image signal obtained from the A / D converter 407. The memory 409 stores the image signal obtained from the image conversion unit 408. The exposure condition determination unit 410 analyzes an image obtained at the time of pre-scanning, determines a speed parameter to be given to the scanning speed control unit 411, and performs fine scanning at the determined scanning speed. The I / O 412 is an interface for connecting a film scanner and a computer (not shown) (hereinafter referred to as “PC”).

  Next, an image reading operation in the film scanner according to the present invention will be described.

  The document image is scanned twice (image reading), which are called pre-scan and fine scan, respectively. The pre-scan determines various parameters in the scan conditions for performing fine scan.

  When the user sets the film 403 on the film scanner, pre-scanning is automatically performed. In that case, the signal amplifier 406 is set to an amplification factor that does not cause overflow even if an image photographed under any exposure condition is scanned. The pre-scan is performed at a low resolution because it is only used for user image confirmation by a monitor (not shown) on the film scanner, in addition to determination of the scan condition during fine scan.

  In the image conversion unit 408, a pre-scan lookup table is set and pre-scan is performed. The result is once written in the memory 409 and sent to the exposure condition determination unit 410.

The exposure condition determination unit 410 calculates a histogram for each color for each image, and calculates a feature amount representing image characteristics such as the highest density, the lowest density, and the average density. Based on these feature amounts, scanning conditions for fine scanning are determined.
For example, if the maximum density of the image is Dmax, the minimum density Dmin, the difference Dmax-Dmin is Ddif, the average density is Dave, and the predetermined values Da, Db, Dc, Dd,
Dmax> Da
Dmin> Db
Dave> Dc
Ddif <Dd
The relationship holds. When this condition is satisfied, it is determined that overexposure is performed, and a parameter for slowing the scanning speed is set in the scanning speed control unit, and fine scanning is performed. As a result, the fine scan scans at a slower speed than the normal scan, so that the amount of light received by the CCD 405 increases and an image with a high S / N ratio and less noise can be obtained. Also, as described with reference to FIG. 2 in “Problems to be solved by the invention”, the density range that can be taken into the CCD shifts to a higher density side than in the normal case, so the higher density side is crushed. Thus, data with good gradation can be obtained. An image that does not satisfy the above conditions is determined not to be an overexposed image, and a normal scan speed parameter is set in the scan speed control unit 411, and a fine scan is performed at the normal scan speed. The fine scan image is sent to the memory 109 and transferred to the PC via the I / O 112.

(Second Embodiment)
In the first embodiment, it is possible to simplify the determination conditions for overexposure as follows.
Dave> Dc
Ddif <Dd
Or
Dmax> Da
Dave> Dc
Or
Dmin> Db
Dave> Dc
Or
Dmax> Da
Ddif <Dd
Or
Dmin> Db
Ddif <Dd
(Third embodiment)
FIG. 5 is a block diagram showing the overall configuration of the film scanner of this embodiment. The difference from the first embodiment is that a mode selection unit 513 is added. Only differences from the first embodiment will be described below.

  In the case of the first embodiment, the over-exposure frame always has a low scanning speed in fine scanning. In addition, the image quality is improved, but the scanning speed is decreased. However, depending on the purpose of scanning, scanning speed may be prioritized over image quality. For example, one of them is “CD-R writing service”. The “CD-R writing service” is a service that scans a plurality of films at a low resolution and writes the read image data to the CD-R. For this reason, for example, when writing 5 films of 36 shots, 180 images recorded on the film must be scanned at a time. Therefore, in the case of this service, priority is given to shortening the scan time over the good gradation of the image.

  In the present embodiment, a mode selection unit 513 is added so as to cope with such a case. Specifically, the user selects either the speed priority mode or the image quality priority mode before starting the fine scan. When the speed priority is selected, the mode selection unit 513 sends a signal to invalidate the determination to the exposure condition determination unit 510 so that all frames are scanned at a standard speed during the fine scan. Do. When the image quality priority mode is selected, the scan speed is reduced only for an image that is overexposed during fine scan by sending a signal for validating the judgment to the exposure condition judgment unit 510. And scan. As a result, an optimum scan can be performed according to the purpose of the scan.

  In the first to third embodiments, for the sake of simplicity of explanation, two scan speeds are prepared in advance as over-exposure or other cases. It is also possible to provide a speed.

  Although the said 1st-3rd embodiment demonstrated the case in the case of a negative film, the case of a positive film is applicable similarly.

  In the first to third embodiments, the exposure condition may be determined for each of R, G, and B colors, and it may be determined whether all the colors satisfy the condition, or whether the exposure is overexposed. It is also possible to use one or three of the three colors as a color for determination. Alternatively, a luminance signal can be obtained from R, G, and B, and it can be determined whether the luminance signal is overexposed.

  The first to third embodiments may be applied to a system including a plurality of devices such as a computer, an interface device, and a scanner, for example, and may be applied to a single device having these functions. May be.

  An object of the present invention is to supply a storage medium (or recording medium) storing a software program for realizing the functions of the above-described first to third embodiments to a system or apparatus, and a computer of the system or apparatus. Needless to say, this can also be achieved by (or CPU or MPU) reading and executing a program stored in a storage medium.

  In this case, the program itself read from the storage medium realizes the functions of the above-described embodiment, and the storage medium storing the program constitutes the present invention. Further, by executing the program read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Further, after the program read from the storage medium is written in a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function expansion card is based on the instruction of the program code. Needless to say, the CPU of the function expansion unit or the like performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing.

  In the above-described embodiment, the program is stored in the memory 409. However, the present invention is not limited to this, and examples of the storage medium for supplying the program include RAM, NV-RAM, floppy (registered trademark) disk, The above programs such as hard disk, optical disk, magneto-optical disk, CD-ROM, MO, CD-ROM, CD-RW, DVD (DVD-ROM, DVD-R), magnetic tape, non-volatile memory card, other ROM, etc. Anything can be stored.

It is a block diagram which shows the whole structure of the conventional image input device. It is a figure which shows the histogram of a standard overexposure image. It is a figure which shows the histogram of the overexposure image in an entirely dark scene. 1 is a block diagram showing an overall configuration of an image input apparatus according to a first embodiment of the present invention. It is a block diagram which shows the whole structure of the image input device which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

401 Light Source 402 Projection Lens 403 Film 404 Imaging Lens 405 Image Reading Sensor 406 Signal Amplifier 407 A / D Converter 408 Image Conversion Unit 409 Memory 410 Exposure Condition Judgment Unit 411 Scan Speed Control Unit 412 I / O

Claims (2)

  Light irradiation means for irradiating the developed film with light from a light source, image reading means for reading an image on the film using a line sensor, film for reading the entire image on the film with the image reading means Alternatively, a scanning means for moving the sensor, a scanning speed control means for variably controlling the scanning speed of the film or sensor, a histogram of the image obtained by the image reading means is obtained, and the exposure condition at the time of image shooting is determined using the histogram. An image input apparatus and method comprising: an exposure condition determination unit configured to change the scanning speed based on a determination result of the exposure condition. Light irradiation means for irradiating the developed film with light from a light source, image reading means for reading an image on the film using a line sensor, film for reading the entire image on the film with the image reading means Alternatively, a scanning means for moving the sensor, a scanning speed control means for variably controlling the scanning speed of the film or sensor, a histogram of the image obtained by the image reading means is obtained, and the exposure condition at the time of image shooting is determined using the histogram. Exposure condition determination means, mode selection means for selecting speed priority or image quality priority. When image quality priority is selected, the scanning speed is changed based on the determination result of the exposure condition. Image input apparatus and method.

Images