JP3579569B2 - Image reading device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading apparatus that irradiates, for example, an image recorded on a film with light and reads the image using a line sensor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an image reading apparatus of this type, an image reading apparatus that reads an image line by line by intermittently transporting a film to be read along a direction orthogonal to a longitudinal direction of a line sensor is known. That is, while the film is stopped, the light output from the light source is irradiated on the film, and a one-line image is detected by the line sensor. After this detection operation, the film is transported by a predetermined amount by the transport mechanism. . Such detection and transfer of an image are repeatedly executed, and an image for one screen is read.
[0003]
In such an image reading apparatus, when the reading optical path is not blocked, for example, immediately after turning on the power, data for correcting an error generated based on the characteristics of the light source and the line sensor, that is, shading correction data, Data and white distortion data are detected. The black distortion data is obtained in a state where the line sensor is shielded from light, and is greatly affected by dark current generated in the line sensor. The white distortion data corresponds to the uneven light amount caused by the characteristics of the light source and the illumination optical system, and is obtained by directly detecting the light emitted from the light source.
[0004]
[Problems to be solved by the invention]
However, when an image recorded on an elongated film such as a negative strip film or an APS film is read by an image reading device, when the optical path of light emitted from a light source is blocked by the film immediately before reading each image, white distortion occurs. Data cannot be detected. Therefore, conventionally, the shading correction data has not been detected for each reading operation of each image recorded on the film.
[0005]
An object of the present invention is to detect at least black distortion data as frequently as possible to improve the image quality of an image read from a film and reproduced.
[0006]
[Means for Solving the Problems]
An image reading apparatus according to the present invention includes a light source that irradiates light to a reading object (a long and thin film) on which a plurality of images are recorded, and an electric signal corresponding to a received light amount to output light transmitted or reflected by the reading object. A detectable optical sensor, image data detecting means for detecting an image formed on the object to be read based on an electric signal output from the optical sensor, and the object to be read is present in the optical path of light emitted from the light source Scanning target detection means for detecting whether or not each image is read, and shading correction means for performing shading correction based on black distortion data and white distortion data, wherein the image data detection means includes a reading target in an optical path. to time, while the light source is detected and updates the black distortion data while turned off, when the object to be read in the light path does not exist, detects and updates the white strain data in a state where the light source is turned on, Shading Grayed correcting means is characterized by performing shading correction on the basis of the black strain data updated for each updated white level correction data and the image.
[0007]
It is preferable that the reading target detecting means detects the presence of the reading target by comparing the electric signal output from the optical sensor with a predetermined reference value .
[0008]
It is preferable that the image reading device includes a light source control unit that controls on / off of the light source. Further, the image reading apparatus preferably includes a transfer mechanism for moving at least one of the reading target, the light source, and the optical sensor so that the light irradiated from the light source is irradiated to a predetermined range of the reading target.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing an image reading apparatus according to one embodiment of the present invention.
[0010]
The film M to be read is a negative film, that is, a transparent original, on which one color image is recorded. The film M is transported intermittently in the direction of arrow A by the document transport mechanism 10. A light source 20 is provided above the passage of the film M, and an imaging lens 31 and a line sensor 30 are provided below. The turning on and off of the light source 20 is controlled by a light source driving circuit 41, and the operation of detecting an image by the line sensor 30 is controlled by a line sensor driving circuit 42. The document transfer mechanism 10, the light source driving circuit 41 and the line sensor driving circuit 42 operate according to a command signal output from the system control circuit 40.
[0011]
The line sensor 30 has a large number of photodiodes arranged in a row, and each photodiode generates an electric signal according to the amount of received light. The electric signal, that is, the image data read from the line sensor 30 is amplified by the amplifier 43 and converted into a digital signal by the A / D converter 44. The digital image data is temporarily stored in the memory 46 after being subjected to processing such as shading correction in the image processing circuit 45. This image data is read from the memory 46 and subjected to a predetermined arithmetic processing such as gamma correction. Then, the image data is converted into a signal according to a predetermined format in the interface circuit 47 and output to the computer (image processing device) 60 via the output terminal 48. The image processing circuit 45 and the interface circuit 47 are controlled by the system control circuit 40.
[0012]
In the present embodiment, all operations of the image reading apparatus are controlled by the computer 60. However, the switch 49 is connected to the system control circuit 40, and the operation of the image reading apparatus is controlled by operating the switch 49. May be configured.
[0013]
FIG. 2 shows the document transfer mechanism 10, the light source 20, and the line sensor 30. The film M is supported by a frame 11, and the frame 11 is fixed to a plate-like stage 12 by a stopper 13. The stage 12 has an opening (not shown) at a position corresponding to the film M. A rack 14 is formed on a side end surface of the stage 12, and the rack 14 meshes with a pinion 16 provided on an output shaft of a document feed motor 15. The document feed motor 15 is driven based on the control of the system control circuit 40, and the position of the film M is controlled.
[0014]
The light source 20 is located above the stage 12, and is configured by periodically arranging light emitting elements 21R, 21G, and 21B that emit blue (B), green (G), and red (R) light in this order. However, this arrangement can be changed according to the purpose. Although only six light emitting elements are shown in FIG. 2, more or less light emitting elements may be provided. These light emitting elements 21R, 21G, and 21B are supported by an elongated support member 22 extending in the width direction of the stage 12, and a cylindrical lens 23 extending in parallel with the support member 22 is provided between the support member 22 and the stage 12. ing. That is, the light emitted from the light emitting element 21 is condensed by the cylindrical lens 23 and is irradiated on the film M in a line.
[0015]
The line sensor 30 is located below the light source 20 with the stage 12 interposed therebetween, and is provided in parallel with the light source 20 and the cylindrical lens 23. That is, the line sensor 30 extends in a direction substantially perpendicular to the direction in which the film M is transported. An imaging lens 31 is provided between the line sensor 30 and the stage 12. The imaging lens 31 extends in parallel with the line sensor 30 and includes a rod lens array 32. Therefore, when the light is irradiated on the film M by the light source 20, an image recorded on the film M is formed on the light receiving surface of the line sensor 30 via the image forming lens 31.
[0016]
FIG. 3 shows a negative strip film M disposed above the line sensor 30 and the imaging lens 31, and other components are omitted. As shown in FIG. 4, the strip film M is attached to the frame 11, and for example, five images P1 to P5 are recorded. A region where no image is recorded, that is, a band-shaped non-recording region N is formed between the images P1 to P5.
[0017]
The frame 11 is fixed to, for example, a stage 12 shown in FIG. That is, while the stage 12 is moved, the light output from the light source 20 is irradiated on the film M, and the images P1 to P5 are read by the line sensor 30.
[0018]
FIG. 4 shows the APS film M disposed above the line sensor 30 and the imaging lens 31, and other components are omitted. For example, 40 images P are recorded on the APS film M, and a non-recording area N is formed between the images P in the same manner as a normal strip film.
[0019]
The APS film M is not attached to the frame but is held together with the patrone T by a holding mechanism (not shown). Although this holding mechanism is basically different from the stage 12 and the frame 11 shown in FIG. 2, it is not related to the present invention, so that the configuration is omitted. The APS film M is transported by the holding mechanism. During this transport, light from a light source is applied to the film M, and the image P is read by the line sensor 30.
[0020]
5 and 6 are flowcharts of a program for performing the image reading operation. The image reading operation will be described with reference to this flowchart and FIG. This program is applicable when reading all the films M shown in FIGS.
[0021]
This program is started by turning on the power of the image reading apparatus. At this start, the light source 20 is still off, that is, turned off. First, steps 101 to 104 are executed in a state where the film M is not mounted on the stage 12.
[0022]
In step 101, the line sensor 30 is driven, charge is stored for a predetermined time, and black distortion data is obtained. This black distortion data is stored in the memory 46. The black distortion data is data according to the charge generated by the dark current generated in the line sensor 30 in addition to the offset component included in the output signal from the line sensor 30, and the charge changes according to the accumulation time. In step 102, the light source 20 is turned on, and illumination light is emitted.
[0023]
In step 103, illumination calibration is performed. That is, the illumination light is directly applied to the line sensor 30, and an output signal from the line sensor 30, that is, white distortion data is input to the image processing circuit 45. In the image processing circuit 45, a white distortion coefficient is obtained based on the white distortion data and the black distortion data obtained in step 101 according to the following equation (1), and stored in the memory 46.
White distortion coefficient = (1023 / (white distortion data−black distortion data)) (1)
However, “1023” corresponds to the number of quantization bits (10 bits) when A / D converting the output of the line sensor 30. Further, the image processing circuit 45 calculates an “average value in a transparent state”, that is, an average value of output data of the line sensor 30 when the illumination light is directly incident on the line sensor 30. This may be, for example, an arithmetic average of white distortion data output from the line sensor 30 for each pixel, or may be an arithmetic average by thinning out the white distortion data.
[0024]
When the illumination calibration is completed, in step 104, the light source 20 is turned off. In this state, a message indicating that "the film M is mounted on the stage 12" is displayed on the screen of the display device of the computer 60.
[0025]
In step 105, it is determined whether or not to start the pre-scan. For example, by clicking the “prescan” mark displayed on the screen of the display device of the computer 60 using a mouse, the process proceeds from step 105 to step 111, and the prescan is executed.
[0026]
In step 111, black distortion data is obtained and updated as in step 101. That is, the black distortion data is replaced in the memory 46 with the black distortion data obtained in step 101. In step 112, the light source 20 is switched on. In step 113, one line of data is read from the line sensor 30, and the image processing circuit 45 calculates the average value. In step 114, it is determined whether or not this average value is considerably smaller than the "average value in the transparent state" (that is, the reference value) obtained in step 103. When the average value obtained in step 114 is considerably smaller than the reference value, that is, when the output data of the line sensor 30 is considerably small, it is considered that the film M is located between the light source 20 and the line sensor 30, Proceeding to step 118, a prescan is performed.
[0027]
On the other hand, when the average value obtained in step 114 is not much smaller than the reference value, that is, when the output data of the line sensor 30 is relatively large, the film M does not exist between the light source 20 and the line sensor 30. Therefore, the same processing as in step 103 is executed in steps 115 to 117. In step 115, white distortion data is obtained. In step 116, a white distortion coefficient is calculated according to equation (1) based on the white distortion data obtained in step 115 and the black distortion data obtained in step 111. Next, at step 116, the white distortion coefficient obtained at step 115 is stored in the memory 46, and is updated with respect to the white distortion coefficient previously stored in the memory 46. Thereafter, in step 118, a prescan is performed.
[0028]
In the pre-scan, the stage 12 is moved at a pitch that is coarser than the main scan performed in step 123, and the light emitted from the light source 20 is applied to a predetermined area of the film M, that is, an image recording area, so that image data is Is detected. The image data is subjected to predetermined processing such as shading correction using the white distortion coefficient and the black distortion data in the image processing circuit 45, and then displayed on the screen of the display device of the computer 60.
[0029]
When the prescan is completed, the light source 20 is switched to the off state in step 119, and then in step 120, it is determined whether or not to start the main scan. For example, by clicking the “main scan” mark displayed on the screen of the display device using a mouse, the process proceeds from step 120 to 121, and black distortion data is obtained in the same manner as in step 101, and the original black distortion is obtained. Updated for data. Thereafter, the light source 20 is turned on in step 122, and the main scan is executed in step 123. The image data obtained by the main scan is subjected to predetermined processing such as shading correction in the image processing circuit 45 and then displayed on the screen of the display device. After execution of step 123, the process returns to step 104, and the above-described processing is executed again.
[0030]
On the other hand, when it is determined in step 120 that the main scan is not to be performed, the process proceeds to step 124, where it is determined whether or not the prescan is to be performed. Steps 120 and 124 are repeatedly executed while the “pre-scan” mark on the screen of the display device is not clicked. However, when the “pre-scan” mark is clicked, the process returns from step 124 to step 111 and the above-described processing is performed. Is executed again.
[0031]
As described above, in the present embodiment, even when reading a plurality of images recorded on an elongated film M such as a negative strip film, black distortion data is detected every time each image is read, and When M does not block the illumination light, white distortion data is detected. Therefore, the white distortion coefficient and the black distortion data are detected as frequently as possible, and the image quality of the reproduced image can be improved.
[0032]
【The invention's effect】
As described above, according to the present invention, the configuration is such that the black distortion data is detected each time one image is read, so that the image quality of the reproduced image can be improved.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an image reading apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a document transport mechanism, a light source, and a line sensor when a transparent document is used as a film.
FIG. 3 is a perspective view showing a negative strip film disposed above a line sensor and an imaging lens.
FIG. 4 is a perspective view showing an APS film disposed above a line sensor and an imaging lens.
FIG. 5 is a first half of a flowchart of a program for performing an image reading operation.
FIG. 6 is a second half of a flowchart of a program for performing an image reading operation.
[Explanation of symbols]
10 Document transfer mechanism 20 Light source 30 Line sensor (optical sensor)
M film (reading target)

Claims (4)

A light source that irradiates light to a reading object in which a plurality of images are recorded on an elongated film ,
An optical sensor that outputs an electric signal corresponding to the amount of received light and can detect light transmitted or reflected by the object to be read;
Image data detection means for detecting an image formed on the reading target based on the electric signal output from the optical sensor,
A reading target detecting unit that detects whether or not the reading target exists in the optical path of the light emitted from the light source for each image;
A shading correction unit that performs shading correction based on the black distortion data and the white distortion data,
The image data detecting means detects and updates the black distortion data in a state where the light source is turned off when the reading target is present in the optical path, and when the reading target is not present in the optical path, The white distortion data is detected and updated with the light source turned on, and the shading correction unit performs the shading correction based on the updated white distortion data and the black distortion data updated for each image. An image reading apparatus, comprising: 2. The image reading apparatus according to claim 1, wherein the reading target detection unit detects the presence of the reading target by comparing the electric signal output from the optical sensor with a predetermined reference value . 3. The image reading apparatus according to claim 1, further comprising a light source control unit that controls on / off of the light source. 2. A transfer mechanism for moving at least one of the object to be read, the light source, and the optical sensor so that the light emitted from the light source is applied to a predetermined range of the object to be read. An image reading device according to claim 1.

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