JP2001148762A - Device and method for reading image, and storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device and a method for image reading which can read an image by detecting an accurate focused position without being affected by noise, and a storage medium. SOLUTION: Focusing is adjusted according to maximum values XB-MAX and XG-MAX which exceed a threshold S among maximum values of focus evaluation quantities (quantities corresponding to the contrast of a subject) calculated from image data of respective colors read in by a line sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly to determining an in-focus position.

[0002]

2. Description of the Related Art The structure of a conventional image reading apparatus having a focus adjusting function will be described with reference to FIG.

[0003] Light emitted from an illumination light source 801 illuminates a film held by a film holder 802. The film holder 802 holds the film in such a manner that the non-image photographing part (perforation part, etc.) of the film is sandwiched between the back and front sides, and can be moved in the direction of arrow A on the drawing by the sub-scanning motor 803. In reading, it plays the role of sub-scan. The light transmitted through the film is passed through an imaging lens 806 to a CCD (Cage Couple).
ed Device) An image is formed on a linear image sensor 804 (hereinafter, referred to as a CCD). Optical unit 805
Consists of an optical component group (for example, a mirror not shown) including an imaging lens 806 and a CCD 804. CCD
Reference numeral 804 is arranged so that the direction perpendicular to the paper surface is the main scanning direction, and is orthogonal to the sub-scanning direction and the optical axis direction.

The optical unit 805 includes a focus motor 8
The focal point can be adjusted by moving in the optical axis direction B by 07.

[0005] An A / D converter 809 converts an analog signal from the analog circuit 808 into a digital signal. The image processing unit 810 includes a gate array that performs gamma conversion of digital signals and various types of filter processing, and also performs processing such as CCD drive pulses. The line buffer 811 temporarily stores the image data. An I / F 812 indicates an interface for connecting to an external device 813 such as a personal computer. The CPU 814 is an external device 813
The image processing unit 810 and the line buffer 81
1. The I / F 812 is connected to the CPU bus 815. Light source lighting circuit 816, sub-scanning motor driver 81
7. The focus motor driver 818 has a CPU 814
This is a circuit for operating each device in accordance with an instruction from the device.

In the CPU 814, control software (form software) operates, and the control software (form software)
Communication is performed with the driver software 13 and image data is output.

Next, the operation procedure of the film scanner will be described with reference to the flowchart of FIG.

[0008] In the film scanner and the personal computer, software is operating, and conditions such as discrimination of film negative and positive are input and communication is possible. The film is set in a holder and inserted into a predetermined position. It is assumed that

The user instructs the personal computer to start a preview operation (step 901; described as S901 in the figure, the same applies hereinafter) in order to see an outline of the image before the main scan.
The driver software sends information such as a reading range and resolution to the film scanner. The firmware software that has received the information enters into electrical preparation (step 902) corresponding to the information described above. The sub-scanning motor 803 operates to move the film to the initial position of the image to be read (step 903). When the light source is turned on (step 904) and a command is issued to output timing pulses (CCD driving pulse, RAM address control pulse, etc.) related to reading (step 905), the sub-scanning motor 803 is driven at a predetermined speed, The digital image processing unit 810 performs AE processing based on the signal output from the CCD 804, and sets an appropriate brightness (step 906).

Subsequently, focus adjustment (step 907) is performed. FIG. 10 is a flowchart showing an outline of the focus adjustment.

First, the sub-scanning motor 803 is driven to move to the auto focus evaluation position (step 1001).
I do. After moving the optical unit 805 to the origin in the optical axis direction by the focus motor 807 (step 1002),
Scanning is started (step 1003). The moving direction of the optical unit 805 is represented by x. The image processing unit 810 calculates an amount (hereinafter, referred to as a focus evaluation amount F (x)) corresponding to the contrast of the subject from the image data of the single color input from the CCD 804 (step 104) (step 1005).

Although many methods have been proposed for calculating the focus evaluation amount, this embodiment employs a method using the sum of squares of the difference between the outputs t _i between adjacent pixels as shown in the following equation. explain.

[0013]

(Equation 1)

After the scanning of the optical unit 805 is completed (step 1006), the position x at which the focus evaluation amount is maximized.
_MAX is detected (step 1007). Lastly, the optical unit 805 is moved to that position with x _MAX as the focus position X (step 1008) and fixed, thereby completing the focus adjustment.

The sub-scanning motor 803 is driven again to move the film to the reference position, a timing pulse for reading one line at a time is output, and the sub-scanning motor 803 is driven.
A pre-scan operation of reading image data for each line at a predetermined exposure time, processing the image data in an image processing unit 810, and outputting the image data to a personal computer (step 9)
08). After scanning the entire image reading range, the CPU 814 returns the film to the initial position,
Each function is stopped such as turning off the illumination light source 801 and the next command is provided. One of the driver software displays the received image (step 909), the user views the previewed image, further sets image reading conditions (step 910), and issues a main scan instruction to end the preview (step 911). I do. In the main scan (step 912), in addition to the information sent at the time of the pre-scan, information for optimally reading an image obtained by the preview is transmitted to the film scanner for execution. The image data obtained by the main scan can be displayed, saved, processed (step 913) on a personal computer.

[0016]

In the above-described conventional focus adjustment mechanism, when a focus evaluation amount is calculated for a certain color component of image data read by a CCD and a focus position is detected, a selected color is used. Depending on the relationship between the components and the subject, it is not possible to obtain a sufficient focus evaluation amount, and it is not possible to determine an accurate focus, and it is also possible to detect an incorrect position as the focus position due to noise from a film scanner, a personal computer, or the external environment There is.

For example, a positive film of a photograph of a white cloud floating in a blue sky as shown in FIG. 11 is read by three color CCDs of R, G, and B (red, green, and blue) and focuses on each of R, G, and B colors. When the evaluation amount is calculated, F as shown in FIG.
_{It is} assumed that _R (x), F _G (x), and F _B (x). Among them, there is a case where noise stronger than the peak intensity is generated as exemplified in F _R (x). If red is selected as the color for calculating the focus evaluation amount, an accurate focus position cannot be detected due to the influence of noise.

In addition, since the in-focus position for each color is not the same due to the chromatic aberration of the imaging lens or the structure of the film, the in-focus position is determined from information on as many colors as possible. It is desirable.

However, the read data of all colors
The in-focus position from the contrast of all colors obtained from
In other words, the position indicating the maximum value of each focus evaluation amount
X _MAX For example, in the method of obtaining the in-focus position from the average,
Focus evaluation amount affected by noise even for one color
If used, it would lead to detecting the exact focus position.
No.

The present invention has been made under such circumstances, and an image reading apparatus and an image reading method capable of detecting an accurate focus position and reading an image without being affected by noise. , And a storage medium.

[0021]

In order to achieve the above object, the present invention provides an image reading apparatus according to the following (1) to (8), and an image reading method according to the following (9). And the storage medium is configured as in (10) below.

(1) A sensor capable of reading a plurality of colors individually, a focus evaluation amount calculating means for calculating a focus evaluation amount of each color in the plurality of colors based on a signal from the sensor, and a focus evaluation amount calculating means And an in-focus position determining means for determining an in-focus position using a maximum value exceeding a threshold value set for each color among the maximum values of the focus evaluation amounts of the respective colors.

(2) The image reading device according to (1), wherein the threshold values set for the respective colors are the same.

(3) In the image reading apparatus according to the above (1), when the original to be read is a negative film, the threshold value set for each color is reduced in the order of red, green and blue.

(4) In the image reading apparatus as described in (3), the threshold value set for each color is set to a red threshold value S _R , and a green threshold value S _G is set to 0.5 SR _R. an image reading apparatus as 0.2 S _R blue thresholds S _B.

[0026] (5) the (4) The image reading apparatus, wherein when read original is positive film, the red, green and blue for each threshold, the image reading apparatus to be the same as S _R.

(6) In an image reading apparatus provided with a light source, an image forming system, a line sensor capable of reading a plurality of colors, and an autofocus signal processing section, image data of all colors or a plurality of colors read by the line sensor. The focus evaluation amount for each color calculated from is compared with a predetermined condition,
An image reading device that determines an optimum focus position and reads an image using only a focus evaluation amount that satisfies a condition.

(7) The image reading device according to any one of (1) to (6), wherein the image reading device is a film scanner.

(8) The image reading device according to any one of (1) to (6), wherein the image reading device is a flatbed scanner.

(9) Image reading by an image reading apparatus comprising a sensor capable of reading a plurality of colors individually and a focus evaluation amount calculating means for calculating a focus evaluation amount of each of the plurality of colors based on a signal from the sensor. A step A of reading the plurality of colors by the sensor; a step B of calculating a focus evaluation amount of each color by the focus evaluation amount calculating means based on the signal read in the step A; Step C of determining the focus position using the maximum value exceeding the threshold value set for each color among the maximum values of the focus evaluation amounts of each color calculated in B, and the focus position determined in this step C And D) reading an image with the sensor.

(10) A storage medium storing a program for realizing the image reading method according to (9).

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to embodiments of a film scanner and a flatbed scanner (flatbed type image scanner).

The present invention is not limited to the image reading apparatus such as the scanner, but is supported by the description of each embodiment, and includes an image reading method, a CD-ROM or the like storing a program for realizing the method. The present invention can be similarly implemented in the form of a storage medium.

[0034]

(Embodiment 1) FIG. 1 is a flowchart showing an autofocus function of a "film scanner" according to the first embodiment. Note that the hardware configuration is the same as that of FIG.

First, the sub-scanning motor 803 is driven to move to the auto-focus evaluation position (step 10).
2). After the optical unit 805 is moved to the origin in the optical axis direction by the focus motor 807 (step 102), scanning is started (step 103). Image data for a plurality of colors is obtained from the CCD 804 (step 104).
The image processing unit 810 calculates a focus evaluation amount F (x) according to the contrast of the subject (Step 105). After the scanning of the optical unit 805 is completed (step 106), the image processing unit 810 compares the maximum value of the total focus evaluation amount with a predetermined threshold value S (step 107).

The threshold value S is an amount set in accordance with the sensitivity of the CCD 804, the effect of the illumination light source 801, the amount of noise generated in the device, and the like. A different value is set for each color. May be set to the same value for some or all colors. FIG. 2 shows an example in which one threshold value S is used.

Colors for which the maximum value of the focus evaluation amount does not satisfy the predetermined threshold value S are excluded in the subsequent processing (step 108).

Next, the position x _{MAX at} which the focus evaluation amount for each color satisfying the threshold value becomes maximum is detected (step 109). An optimum focus position x is calculated from x _MAX for each color (step 110). The calculation method may be simple averaging, or may be calculated by weighting each color.

Finally, X is focused to the optical unit 80
5 is moved to that position (step 111) and fixed.

As described above, according to this embodiment,
Since focus adjustment is performed using the maximum value of the focus evaluation amount that is not affected by noise, accurate focus adjustment can be performed.

(Embodiment 2) FIG. 3 is a flowchart showing the operation of a "film scanner" according to Embodiment 2. The hardware configuration of this embodiment is the same as that of FIG. 8, and the description will be omitted with reference to FIG.

The focus adjustment of a film scanner capable of reading high-quality images on both negative and positive films will be described. First, the sub-scanning motor 803 is driven to move to the auto focus evaluation position (step 301). After the optical unit 805 is moved to the origin in the optical axis direction by the focus motor 807 (step 302), scanning is started (step 303). The image processing unit 810 calculates the focus evaluation amount F (x) according to the contrast of the subject (Step 305) from the image data of a plurality of colors obtained from the CCD 804 (Step 304).

The scanning of the optical unit is completed (step 30).
6) Then, it is determined whether the film to be read is a negative film or a positive film (step 307). If it is determined that the film is a positive film, as described in Example 1,
The same threshold value S is adopted for all colors. On the other hand, the negative film has a characteristic that the transmittance of blue light is smaller than that of red because the base film is originally orange. Therefore, the contrast of the blue image information is smaller than that of red, and if the same threshold value S is used for all the colors of the positive film, the maximum value of the focus evaluation amount for blue cannot satisfy the threshold value. Increase. In order to prevent this, in the present embodiment, when reading a negative film, the red threshold value employs S _R having the same size as that of the threshold value of the positive film, but the green threshold value adopts S _R
, And 50% of S _G and 20% of S _B are used for the blue threshold value (step 308).

Subsequently, the image processing section 810 compares the maximum value of the total focus evaluation amount with a predetermined threshold value S for each color (step 309).

FIG. 4 illustrates the relationship between the focus evaluation amount and the threshold value when a certain negative film is read. Colors for which the maximum value of the focus evaluation amount does not satisfy the predetermined threshold value S are excluded in the subsequent processing (step 31).
0). In the example of FIG. 4, the blue focus evaluation amount is excluded.
Next, the position x _{MAX at} which the focus evaluation amount for each color that satisfies the threshold is maximized is detected (step 311). An optimum focus position X is calculated from x _MAX for each color (step 312). The calculation method may be simple averaging, or may be calculated by weighting each color. Finally, the optical unit 80 is set with X as the focus position.
5 is moved to that position (step 313) and fixed.

As described above, according to this embodiment,
Since the focus adjustment is performed based on the maximum value of the focus evaluation amount excluding the maximum value of the focus evaluation amount that may be affected by noise, the focus adjustment can be performed accurately.

The first and second embodiments are examples of a film scanner.
When a film original is read by the adapter, the same operation can be performed.

(Embodiment 3) As Embodiment 3, a flatbed scanner having an autofocus function will be described.

FIG. 5 shows a schematic configuration of the "flatbed scanner" of this embodiment.

A document to be read is placed on a document table 501. The scanning unit 506, including the reflection mirror 502, the illumination device 503, the focus motor 504, and the optical unit 505, moves the sub-scanning motor 50 under the platen glass.
7 to read the image. An optical unit 505 including an imaging lens 508 and a CCD 509 is moved in a scanning unit 506 in an optical axis direction by a focus motor 504 to perform focus adjustment.

The flatbed scanner has many uses for reading documents. However, in a general flatbed scanner, lines of text in a document are often in the main scanning direction, and when performing focus adjustment with a single color (one line of information) obtained from a CCD, an area with low contrast between lines is read. Therefore, the possibility of performing focus adjustment increases, and accurate focus adjustment cannot be expected.

In this embodiment, by using each contrast obtained from the CCDs of a plurality of lines, it is possible to adjust the focus using information of a wider area than in the case of a single color.
The accuracy is improved.

The case where the CCD is a three-line CCD of R, G and B will be described as an example. FIG. 6 shows an original reading surface 601.
And the relative relationship between the imaging lens 602 and the 3-line CCD 603 are shown. When reading the three-color data at a time with the scanning unit fixed, the three-color data is read at a position shifted by a distance obtained by multiplying the CCD line interval on the same original surface by the magnification of the imaging lens. In the example of FIG. 6, the line B completely reads the line spacing of the text, and a focus evaluation amount with sufficient strength cannot be obtained.

Also, the line of G is blurring the line of the sentence, but the focus evaluation amount becomes as shown in FIG. 7 and the vertices become extremely gentle, and the maximum value is determined to determine the focus position. Can be difficult.

On the other hand, the R line is in the middle of the sentence, and FIG.
As shown in (1), a sufficient focus evaluation amount can be obtained.

When the focus adjustment is performed with one color data, it is highly probable that the focus evaluation amount obtained from the position such as the B line or the G line described above is used, and is influenced by noise from the apparatus main body. Possibilities are expected. Further, even if a conventional method of calculating from the scanning positions to be applied without imposing a threshold value on the maximum value of the focus evaluation amounts of the three colors, an accurate focusing position cannot be determined. In the present embodiment, a threshold value is imposed as shown by S in FIG. 7 and a focus position is determined from a focus evaluation amount according to a flow similar to the flow chart of FIG. 1, thereby enabling accurate focus adjustment.

[0057]

As described above, according to the present invention,
An accurate in-focus position can be detected and an image can be read without being affected by noise.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an autofocus operation according to a first embodiment.

FIG. 2 is a diagram illustrating a focus evaluation amount used in a first embodiment.

FIG. 3 is a flowchart illustrating an autofocus operation according to a second embodiment.

FIG. 4 is a diagram showing a focus evaluation amount used in a second embodiment.

FIG. 5 is a diagram showing a configuration of a third embodiment.

FIG. 6 is a diagram showing a relative relationship between a character array and a CCD.

FIG. 7 is a diagram showing a focus evaluation amount used in a third embodiment.

FIG. 8 is a diagram showing a configuration of a conventional example.

FIG. 9 is a flowchart showing the operation of the conventional example.

FIG. 10 is a flowchart showing a focus adjustment operation;

FIG. 11 is a diagram showing an example of an image on a positive film.

FIG. 12 is a diagram showing a difference between focus evaluation amounts of respective colors.

[Explanation of symbols]

 804 CCD 810 Image processing unit 814 CPU

Claims (10)

[Claims] 1. A sensor which can individually read a plurality of colors, a focus evaluation amount calculating means for calculating a focus evaluation amount of each color in the plurality of colors based on a signal from the sensor, and a focus evaluation amount calculating means. An image reading apparatus comprising: a focus position determining unit that determines a focus position by using a maximum value exceeding a threshold value set for each color among the maximum values of the focus evaluation amounts of the respective colors. . 2. The image reading apparatus according to claim 1, wherein
An image reading apparatus wherein the threshold values set for the respective colors are the same. 3. The image reading device according to claim 1, wherein
An image reading apparatus characterized in that, when a document to be read is a negative film, the threshold value set for each color is reduced in the order of red, green, and blue. 4. The image reading device according to claim 3, wherein
The threshold value set for each color is set to the red threshold value S _R
As the green threshold S _G and 0.5SR _R, the image reading apparatus is characterized in that the blue threshold S _B and 0.2 S _R. 5. The image reading device according to claim 4, wherein
If read original is positive film, the red, green and blue for each threshold, the image reading apparatus, which comprises the same and S _R. 6. An image reading apparatus comprising a light source, an image forming system, a line sensor capable of reading a plurality of colors, and an auto-focus signal processing unit, wherein image data of all colors or a plurality of colors read by the line sensor is used. An image reading apparatus comprising: comparing a focus evaluation amount for each color to be calculated with a predetermined condition; determining an optimum focus position by using only a focus evaluation amount satisfying the condition; and reading an image. 7. The image reading device according to claim 1, wherein said image reading device is a film scanner. 8. The image reading apparatus according to claim 1, wherein said image reading apparatus is a flatbed scanner. 9. An image reading method for an image reading apparatus, comprising: a sensor capable of individually reading a plurality of colors; and a focus evaluation amount calculating means for calculating a focus evaluation amount of each color in the plurality of colors based on a signal from the sensor. A step A of reading the plurality of colors by the sensor; a step B of calculating a focus evaluation amount of each color by the focus evaluation amount calculating means based on the signal read in the step A; Step C of determining the focus position using the maximum value exceeding the threshold value set for each color among the maximum values of the focus evaluation amounts of the colors calculated in step C; Step D of reading an image by the sensor
An image reading method comprising: 10. A storage medium storing a program for realizing the image reading method according to claim 9.