JP6151403B1 - Image reader and sorter - Google Patents

Abstract

The problem of color misregistration in an image reading apparatus using a line sensor is solved by a simple method regardless of complicated image processing. An image reading apparatus includes: a plurality of line sensors that generate pixel data at a predetermined scan time interval; a delay memory that stores pixel data from the plurality of line sensors; And image processing means for reading out pixel data corresponding to different scans to form an image, and control means for adjusting the scan time interval. [Selection] Figure 1

Description

  The present invention relates to an image reading apparatus and a sorter. In particular, the present invention relates to an image reading apparatus using a line sensor and a sorter equipped with such an image reading apparatus.

  Conventionally, an image reading apparatus using three line sensors (hereinafter referred to as three line sensors) respectively corresponding to three colors of R (red), G (green), and B (blue) is known. In an image reading apparatus using a three-line sensor, the scan position (reading line) on the subject by each line sensor is different. Therefore, if the pixel data of each line sensor is synthesized as it is, a color shift occurs in the synthesized image. As a correction method for preventing such color misregistration, conventionally, pixel data of each line sensor is held in a delay memory, and the same point on the subject passes through each reading line of each line sensor ( In other words, pixel data scanned at different timings are associated with each other and synthesized into one image (see, for example, Patent Documents 1 and 2).

JP 2006-211122 A Japanese Examined Patent Publication No. 6-20221

  The above correction method is effective when the distance that the subject moves during the scan time interval of the line sensor is an integral multiple of the distance between the read lines of each line sensor. As measures when this condition is not satisfied, the cited references 1 and 2 further show that the problem of color misregistration is solved by adopting complicated image processing.

  SUMMARY An advantage of some aspects of the invention is that it solves a problem of color misregistration in an image reading apparatus using a plurality of line sensors by a simpler method. .

  In order to solve the above-described problem, an aspect of the present invention provides a plurality of line sensors that generate pixel data at a predetermined scan time interval, a delay memory that stores pixel data from the plurality of line sensors, An image reading apparatus comprising: image processing means for reading out pixel data corresponding to different scans for each line sensor from a delay memory to form an image; and control means for adjusting the scan time interval.

  According to another aspect of the present invention, in the above aspect, the scan time interval is a time determined by a count number and a frequency of clock pulses for driving the plurality of line sensors, and the control unit Is an image reading device configured to adjust the scan time interval by changing at least one of the count number and the frequency of the clock pulse.

  According to another aspect of the present invention, in the above aspect, the image reading apparatus further includes user operation means configured to receive a user input for changing at least one of the count number and the frequency of the clock pulse. Device.

  According to another aspect of the present invention, in the above aspect, the storage unit stores a plurality of clock pulse count and frequency pairs in advance as preset data, and selects one of the plurality of pairs. And a user operation unit configured to receive a user input for performing the operation.

  Another aspect of the present invention is the image reading apparatus according to the above aspect, further comprising display means for displaying the formed image before the user input is given.

  According to another aspect of the present invention, in the above aspect, the apparatus further includes speed detection means for detecting a moving speed of a subject imaged by the plurality of line sensors, and the control means detects the subject. An image reading apparatus configured to determine a count number and a frequency of the clock pulse based on a moving speed.

  According to another aspect of the present invention, in the above aspect, the control unit may calculate the count number p and the frequency f of the clock pulse by the following formula p / f = m · (L / V) (where m Is a positive integer, L is a distance between reading lines corresponding to each line sensor, and V is a moving speed of a subject).

  According to another aspect of the present invention, in the above aspect, the image reading apparatus further includes a compensation unit configured to compensate the brightness of the image in accordance with the adjustment of the scan time interval.

  According to another aspect of the present invention, an image reading apparatus according to the above aspect and an object to be selected as a subject imaged by the plurality of line sensors are based on the image formed by the image reading apparatus. And a sorting means for sorting.

  According to the present invention, the problem of color misregistration in an image reading apparatus using a plurality of line sensors can be solved by a simple method without complicated image processing.

It is a figure showing a schematic structure of sorting machine 100 concerning a 1st embodiment. It is a figure which shows the reading line of 3 line sensor 201. FIG. FIG. 6 is a diagram showing a positional relationship between the position of a subject 500 and reading lines 250R, 250G, and 250B at the scanning timing of the three-line sensor 201. FIG. 6 is a diagram showing a positional relationship between the position of a subject 500 and reading lines 250R, 250G, and 250B at the scanning timing of the three-line sensor 201. FIG. 6 is a diagram illustrating a clock pulse from a clock 207 and an accumulation time determination pulse generated by a drive circuit 206. It is a figure which shows schematic structure of 100 A of sorters which concern on 2nd Embodiment. It is a figure which shows schematic structure of the sorter 100B which concerns on 3rd Embodiment.

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

  FIG. 1 is a diagram showing a schematic configuration of a sorter 100 according to the first embodiment of the present invention. The sorter 100 includes an image reading device 200 and an air gun 300. The sorter 100 is configured to eject an air flow 305 from the air gun 300 when the sorting object 500 flowing from the upstream to the downstream is defective. The selection object 500 is, for example, rice grains, beans, cereals, seeds, glass pieces, plastic pieces, or the like. By removing the defective sorting object 500 by the air flow 305, the sorting object 500 is sorted into a non-defective product and a defective product. The air gun 300 is an example of a sorting unit for sorting the object 500, and another mechanism different from the air gun 300 may be used as the sorting unit.

  The image reading apparatus 200 includes a three-line sensor 201, a lens 202, an analog / digital converter 203, a delay memory 204, an image processing circuit 205, a drive circuit 206, a clock 207, a control unit 208, and a user operation unit. 209, a display unit 210, an illumination 214, a light control unit 215, and an image compensation unit 216. The clock 207 generates a clock pulse having a predetermined frequency and supplies it to the drive circuit 206. The drive circuit 206 generates a drive pulse for driving the 3-line sensor 201 using the clock pulse from the clock 207 and supplies the drive pulse to the 3-line sensor 201. The 3-line sensor 201 performs a scan (imaging) operation every time it receives a drive pulse from the drive circuit 206. The three-line sensor 201 captures an image of the subject 500 as an object to be moved that moves at a certain moving speed V through the lens 202. The 3-line sensor 201 includes three line sensors corresponding to the three colors R (red), G (green), and B (blue), and each line sensor outputs an analog pixel signal corresponding to each color. , And output to the analog-digital converter 203 provided for each color. Each analog-digital converter 203 converts an analog pixel signal into digital pixel data and outputs the digital pixel data to the delay memory 204. The image processing circuit 205 reads out the pixel data of each color from the delay memory 204 and forms an image including the subject 500. The display unit 210 displays the image formed by the image processing circuit 205.

  A user who is an operator of the sorter 100 adjusts the time interval (scan time interval) of the driving pulses supplied to the three-line sensor 201 when the image displayed on the display unit 210 includes a color shift. User input is provided to the user operation unit 209. The drive pulse time interval is a length of time determined by the number of clock pulses counted and the frequency. In the present embodiment, the user input is an input that specifies changing (increasing or decreasing) at least one of the count number of clock pulses and the frequency. The control unit 208 instructs the clock 207 of the changed frequency when a user input designating the change of the frequency of the clock pulse is given. The clock 207 generates a clock pulse having a frequency designated by the control unit 208. In addition, when a user input designating change of the clock pulse count number is given, the control unit 208 instructs the drive circuit 206 of the changed count number. The drive circuit 206 operates so as to generate a drive pulse each time a count number of clock pulses instructed from the control unit 208 is input from the clock 207. In this way, the scan time interval of the three-line sensor 201 is adjusted according to user input from the user.

  FIG. 2 is a diagram illustrating a reading line of the three-line sensor 201. As illustrated, the three-line sensor 201 includes a red line sensor 201R, a green line sensor 201G, and a blue line sensor 201B. On the plane Q on which the subject 500 moves, the red line sensor 201R, the green line sensor 201G, and the blue line sensor 201B capture images at the positions of the reading lines 250R, 250G, and 250B, respectively. The distance L between the reading lines is a distance determined by the interval between the color line sensors in the three-line sensor 201 and the magnification of the optical system including the lens 202. As described above, the three-line sensor 201 is configured such that the line sensors 201R, 201G, and 201B of the respective colors scan the reading lines 250R, 250G, and 250B at different positions.

  Since the moving subject 500 passes through the reading lines 250R, 250G, and 250B corresponding to the respective colors at different timings, the pixel data of the red line sensor 201R scanned when the subject 500 passes through the reading line 250R, and the reading line Using the pixel data of the green line sensor 201G scanned at the time of passing through 250G and the pixel data of the blue line sensor 201B scanned at the time of passing through the reading line 250B, a composite image without color misregistration can be obtained. I can. However, depending on the relationship between the scanning time interval of the three-line sensor 201 and the moving speed of the subject 500, the timing at which the same position on the subject 500 passes through the reading lines 250R, 250G, and 250B and the scanning timing of the three-line sensor 201 Is not synchronized with each other, and color misregistration cannot be eliminated completely. This can be a problem especially when the moving speed of the object to be sorted (subject) 500 is not accurately known in the sorter.

Assuming that the scanning time interval of the three line sensor 201 is T, the distance k that the subject 500 moves during one scan is:
(1) k = V · T
It becomes. Also, let U be the moving speed of the subject 500 such that the subject 500 moves just by the distance L between the reading lines during one scan,
(2) (m−1) · U <V ≦ m · U (m = 1, 2, 3,...)
Define a positive integer that satisfies. At this time, for an arbitrary Nth scan, the scan time interval T of the three-line sensor 201 and the moving speed V of the subject 500 are expressed by the relational expression (3) k = m · L, ie V · T = m · L
If the relationship satisfies the above, the N-th, N + m-th, and N + 2m-th scan timings of the 3-line sensor 201 and the timing at which the same position on the subject 500 passes through the reading lines 250R, 250G, and 250B, respectively. To come. On the other hand, when the scan time interval T and the moving speed V do not satisfy the relational expression (3),
(4) ΔL = m · L−k = m · L−V · T
The color misregistration error ΔL expressed by

  3 and 4 are diagrams showing the positional relationship between the position of the subject 500 and the reading lines 250R, 250G, and 250B at the scanning timing of the three-line sensor 201. FIG. FIG. 3 shows a situation in which the relational expression (3) in the case of m = 1 is satisfied (that is, V · T = L). The position X on the subject 500 passes through the reading line 250R at the Nth scanning timing, passes through the reading line 250G at the (N + 1) th scanning timing, and passes through the reading line 250B at the (N + 2) th scanning timing. Therefore, from the delay memory 204, the pixel data corresponding to the Nth scan of the red line sensor 201R, the pixel data corresponding to the N + 1th scan of the green line sensor 201G, and the N + 2th scan of the blue line sensor 201B are supported. By reading out and synthesizing pixel data to be synthesized, a synthesized image without color misregistration can be obtained. On the other hand, FIG. 4 shows a situation (that is, V · T ≠ L) in which the relational expression (3) is not satisfied when m = 1. The position X on the subject 500 that has passed through the reading line 250R at the Nth scanning timing is shifted from the reading lines 250G and 250B at the N + 1th and N + 2th scanning timings, respectively. Therefore, the pixel data corresponding to the Nth scan of the red line sensor 201R, the pixel data corresponding to the N + 1th scan of the green line sensor 201G, and the pixel data corresponding to the N + 2th scan of the blue line sensor 201B are combined. Even if this is the case, the color misregistration is not eliminated and the error ΔL in the equation (4) remains.

  In order to prevent such a color misregistration error ΔL from occurring, the image reading apparatus 200 according to the present embodiment has a charge among driving pulses supplied to the three-line sensor 201 in accordance with a user input given by the user. Is configured to adjust a time interval (scan time interval) T of a drive pulse (hereinafter referred to as an accumulation time determination pulse) for determining the accumulation time. FIG. 5 is a diagram illustrating a clock pulse from the clock 207 and an accumulation time determination pulse generated by the drive circuit 206. The clock pulse is a continuous pulse having a frequency f. The drive circuit 206 counts the clock pulses and generates one accumulation time determination pulse for every count number p instructed from the control unit 208. Generally, the charge accumulation time is proportional to the period (scan time interval) T of the accumulation time determination pulse, and the scan time interval T is expressed as p / f. Therefore, the scan time interval T of the three-line sensor 201 changes according to the clock pulse count number p and the frequency f. The user inputs a user input for changing at least one of the clock pulse count number p and the frequency f from the user operation unit 209 (for example, an operation button for incrementing or decrementing the count number p or the frequency f by a predetermined step width). By giving, the scan time interval T of the three-line sensor 201 can be adjusted.

Here, the relational expression (3) is
(5) p / f = m · (L / V)
Can be rewritten. When at least one of the clock pulse count p and the frequency f is changed by a user input from the user, if the relational expression (5) is satisfied as a result of the change, the image displayed on the display unit 210 Does not include color shift. On the other hand, if the relational expression (5) is still not satisfied even when at least one of the clock pulse count number p and the frequency f is changed, an image including a color shift is displayed on the display unit 210. While confirming the image displayed on the display unit 210, the user continues to provide the user operation unit 209 with user input for changing the clock pulse count number p and the frequency f until the color shift in the image becomes the least noticeable. In this way, finally, color misregistration included in an image formed by the image processing circuit 205 can be minimized.

  The minimum color shift that can be realized at this time is an adjustment resolution of the scan time interval T of the three-line sensor 201, that is, a value that the scan time interval T can take for various values of the clock pulse count number p and the frequency f Depends on resolution. When the resolution of the count number p is Δp, the scan time interval T = p / f when the frequency is f and the count number is p, and the scan time interval T ′ = (p + Δp when the frequency is g and the count number is p + Δp. ) / G, the resolution h of the scan time interval is expressed by the following equation (6).

When a user input for changing only the clock pulse count number p is given, f = g. At this time, the minimum resolution h is Δp = 1. (7) h = 1 / f
It becomes. When a user input for changing only the frequency f of the clock pulse is given, Δp = 0, and therefore the resolution h is expressed by the following equation (8).

  On the other hand, in a conventional image reading apparatus in which the clock pulse count number p and the frequency f are fixed, the resolution of the scan time interval T is equal to T itself. Therefore, if h / T <1, the image reading apparatus 200 according to the present embodiment can correct the color misregistration with higher accuracy than the conventional image reading apparatus. This condition is expressed by the following equation (9), which is transformed to obtain equation (10).

  As described above, in the image reading apparatus 200 of the present embodiment, control is performed to increase or decrease the scan time interval T of the three-line sensor 201, that is, the charge accumulation time. There is a possibility that the brightness of the image formed by the image processing circuit 205 varies due to increase or decrease in the charge accumulation time. In view of this, in the image reading apparatus 200 according to the present embodiment, a dimming unit for dimming the illumination 214 of the subject 500 in order to prevent or reduce variations in the brightness of the image formed by the image processing circuit 205. 215 or an image compensation unit 216 for compensating the brightness of the image in the image processing of the image processing circuit 205 may be provided. As an example, the dimmer 215 is configured to dimm the illumination 214 to an illuminance predetermined according to the scan time interval T determined by the clock pulse count p and the frequency f instructed from the controller 208. Is done. For example, the image compensation unit 216 performs feedback control based on the brightness obtained from the image generated by the image processing circuit 205 so that the brightness of the obtained image is constant. Or the light control part 215 and the image compensation part 216 may be comprised so that it may operate | move according to the setting from a user.

FIG. 6 is a diagram showing a schematic configuration of a sorter 100A according to the second embodiment of the present invention. The sorter 100A is different from the first embodiment in that the image reading apparatus 200A includes a storage unit 211. The storage unit 211 stores preset data 212. The preset data 212 is data including a plurality of pairs of clock pulse counts p and frequencies f. Each pair of the clock pulse count number p and the frequency f may be set for each type of the object to be sorted 500. For example, a pair of count number p ₁ and frequency f ₁ suitable for the case where the sorting object 500 is rice grains, a pair of count number p ₂ and frequency f ₂ suitable for the case where the sorting object 500 is legume, and the sorting object 500 Is a pair of count number p ₃ and frequency f ₃ suitable for the case of cereals, and the like are stored in the storage unit 211 as preset data 212. The user gives a user input for designating the type of the object to be sorted 500 to the user operation unit 209. The control unit 208 reads a count number p and a frequency f pair corresponding to the type of the object 500 specified by the user input from the preset data 212 of the storage unit 211, and drives the read count number p and the frequency f, respectively. The circuit 206 and the clock 207 are instructed. As described above, the user can optimally adjust the scan time interval of the three-line sensor 201 only by specifying the type of the object to be sorted 500.

  FIG. 7 is a diagram showing a schematic configuration of a sorter 100B according to the third embodiment of the present invention. The image reading apparatus 200B of the sorter 100B includes a speed detection unit 213 instead of the user operation unit 209. The speed detection unit 213 is configured to detect the moving speed V of the object to be sorted 500. The speed detection unit 213 supplies data indicating the detected moving speed V to the control unit 208. Based on the moving speed V, the control unit 208 determines the clock pulse count number p and the frequency f that best match the above-described relational expression (5). For example, the control unit 208 is configured to select a pair of the count number p and the frequency f that best matches the relational expression (5) from the preset data 212 of the storage unit 211. Alternatively, when the clock pulse count number p (or frequency f) is a fixed value, the control unit 208 causes the other variable clock pulse frequency f (or count number p) to satisfy the relational expression (5). ) May be obtained by calculation. Thus, according to the present embodiment, the scan time interval of the three-line sensor 201 can be automatically adjusted optimally without any user input from the user.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this, A various change is possible within the range which does not deviate from the summary.

DESCRIPTION OF SYMBOLS 100 Sorting machine 200 Image reader 201 Three line sensor 202 Lens 203 Analog digital converter 204 Delay memory 205 Image processing circuit 206 Drive circuit 207 Clock 208 Control part 209 User operation part 210 Display part 211 Storage part 212 Preset data 213 Speed detection part 214 Illumination 215 Light control unit 216 Image compensation unit 300 Air gun 305 Air flow 500 Subject (object to be selected)

Claims (6)

A plurality of line sensors that generate pixel data at predetermined scan time intervals;
A delay memory for storing pixel data from the plurality of line sensors;
Image processing means for reading out pixel data corresponding to different scans for each line sensor from the delay memory and forming an image; and
Control means for adjusting the scan time interval;
With
The scan time interval is a time determined by a count number and a frequency of clock pulses for driving the plurality of line sensors,
The control means is configured to adjust the scan time interval by changing at least one of the count number and frequency of the clock pulse,
Furthermore,
User operation means configured to receive a user input for changing at least one of a count number and a frequency of the clock pulse;
Display means for displaying the formed image prior to being provided with the user input;
An image reading apparatus comprising: A plurality of line sensors that generate pixel data at predetermined scan time intervals;
A delay memory for storing pixel data from the plurality of line sensors;
Image processing means for reading out pixel data corresponding to different scans for each line sensor from the delay memory and forming an image; and
Control means for adjusting the scan time interval;
With
The scan time interval is a time determined by a count number and a frequency of clock pulses for driving the plurality of line sensors,
The control means is configured to adjust the scan time interval by changing at least one of the count number and frequency of the clock pulse,
Furthermore,
Storage means for storing in advance a plurality of pairs of the clock pulse count and frequency as preset data;
User operation means configured to receive user input for selecting one of the plurality of pairs;
Display means for displaying the formed image prior to being provided with the user input;
An image reading apparatus comprising: A plurality of line sensors that generate pixel data at predetermined scan time intervals;
A delay memory for storing pixel data from the plurality of line sensors;
Image processing means for reading out pixel data corresponding to different scans for each line sensor from the delay memory and forming an image; and
Control means for adjusting the scan time interval;
With
The scan time interval is a time determined by a count number and a frequency of clock pulses for driving the plurality of line sensors,
The control means is configured to adjust the scan time interval by changing at least one of the count number and frequency of the clock pulse,
A speed detecting means for detecting a moving speed of a subject imaged by the plurality of line sensors;
The control means is configured to determine the count number and frequency of the clock pulse based on the detected moving speed of the subject.
Image reading device. The control means calculates the count number p and the frequency f of the clock pulse as follows: p / f = m · (L / V)
(Where m is a positive integer, L is the distance between the reading lines corresponding to each line sensor, and V is the moving speed of the subject)
To meet,
The image reading apparatus according to claim 3. A plurality of line sensors that generate pixel data at predetermined scan time intervals;
A delay memory for storing pixel data from the plurality of line sensors;
Image processing means for reading out pixel data corresponding to different scans for each line sensor from the delay memory and forming an image; and
Control means for adjusting the scan time interval;
Compensation means configured to compensate for brightness of the image in response to adjustment of the scan time interval;
An image reading apparatus comprising: A plurality of line sensors that generate pixel data at predetermined scan time intervals;
A delay memory for storing pixel data from the plurality of line sensors;
Image processing means for reading out pixel data corresponding to different scans for each line sensor from the delay memory and forming an image; and
Control means for adjusting the scan time interval;
Sorting means for sorting an object to be sorted as a subject imaged by the plurality of line sensors based on the image formed by the image processing means;
Sorting machine equipped with.