JPH0766939A - Image forming device - Google Patents

Abstract

PURPOSE:To detect a document state with high accuracy and at a high speed without being accompanied with an increase of cost by executing a pre-scan of a document by a first document state detecting means before an image is formed, and controlling the pre-scan of the document by a second document state detecting means by its data. CONSTITUTION:A first scan to a document 15 by an image sensor 13 determines the maximum coordinate and the minimum coordinate in the main scanning direction and the sub-scanning direction, respectively of the document 15 against the document platen glass 14 surface. Subsequently, in a second scan to the document 15, a front/rear prescribed range in the main scanning direction is calculated as a parameter from the maximum coordinate and the minimum coordinate determined by a first scan, and while switching a document scanning speed, a line image of the document 15 is fetched. That is, in a second scan, the scan is executed with high accuracy and at a low speed by using document position data read out with low accuracy and at a high speed by a first scan, therefore, the document position can be determined with high accuracy finally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
More specifically, the present invention relates to an image forming apparatus including a document state detecting unit.

[0002]

2. Description of the Related Art Some conventional image forming apparatuses detect a document state such as a position. FIG. 7 is a diagram showing a schematic configuration of an example of a document reading system in such a conventional image forming apparatus.

In the figure, 1 is an exposure lamp and 2 is a CCD
Original 4 placed on the platen glass 3 with the line sensor
The image of one line of can be read. The image of the original 4 is read by moving the exposure lamp 1 and the CCD line sensor 2 in the S direction by the pulse motor 5. Note that A indicates the main scanning direction of the original 4 and B indicates the sub scanning direction of the original 4.

FIG. 8 shows a schematic flowchart of the task of detecting the original 4. In step S41, variables Amax and Ami representing the maximum and minimum values of the original 4 in the main scanning direction are displayed.
n and a variable Bma representing the maximum and minimum values in the sub-scanning direction
The initial values of x and Bmin are set to -1. Step S4
2, the scanning of the original 4 is started, and the scanning is performed in step S44 until the scanning is completed in step S43.
Repeat the update of x, Amin, Bmax, Bmin,
The maximum and minimum values in the main scanning direction and the sub scanning direction are obtained.

FIG. 9 is a detailed flowchart showing the task of step S44. The image data of one line read by the CCD line sensor 2 in step S51 is
Transfer to the memory connected to the CPU. Step S5
2. In S53, it is determined whether or not the original 4 exists on the line read from the transferred image data, and if it is present and the line is the first line of the original 4 after the start of scanning, , The current reading position is Amin
And In steps S54 and S55, it is determined whether or not the original 4 exists on the line read from the transferred image data, and it is the first line that does not exist and the original 4 does not exist after updating Amin. If so, the current reading position is set to Amax.

In steps S56 and S57, the minimum main scanning position on the line is calculated and substituted for Tmin to obtain Tmi.
If n is smaller than Bmin or the initial value of Bmin is -1, Tmin is substituted for Bmin. In steps S58 and S59, the maximum main scanning position on the line is calculated and assigned to Tmax. If Tmax is greater than Bmax, then Tmin is assigned to Bmin.

[0007]

However, in the above-described conventional example, in order to more accurately obtain the maximum value and the minimum value in the main scanning direction and the sub scanning direction of the document, the main scanning direction (CC
It is necessary to reduce the reading density in the D line direction) to increase the number of pixels in one line and to sequentially read the image data of one line at a smaller pitch with respect to the document. For this purpose, the reading cycle in units of one line is shortened, or C for the original in the main scanning direction is set.
It is necessary to slow down the moving speed of the CD.

For this reason, there is a possibility that a great deal of cost is required for detecting the state of the original or a long time is required for detecting the state of the original.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of realizing high-precision and high-speed detection of a document state without increasing cost. .

[0010]

SUMMARY OF THE INVENTION An image forming apparatus provided by the present invention is an image forming apparatus having an original reading unit, and an original prescanning unit capable of scanning an original before image formation and an original prescanning unit. First original state detecting means for detecting the state of the original by scanning, second original state detecting means for detecting the state of the original by prescanning the original, and second original state detecting means by the data from the first original state detecting means. And a means for determining the control method.

The image forming apparatus provided by the present invention is
In the above-mentioned image forming apparatus, the document prescan is performed by the first document state detecting means on the outward path of one scanning operation, and the document prescan is performed by the second document state detecting means on the return path.

[0012]

In the present invention, the original document prescan is performed by the first original document state detecting means before the image formation, and the original document prescanning by the second original document state detecting means is controlled by the data from the detecting means. Therefore, it is possible to detect the document state with high accuracy and high speed, and use the data of the document state to realize a high-quality and high-precision image at low cost.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram of a reader unit of a digital color copying machine according to this embodiment. In the figure, 11 is an exposure lamp, 12 is a lens, and 13 is a full-color image sensor capable of reading a line image (in this embodiment, a CCD sensor is used), which is placed on the platen glass 14. The image of the document 15 is read. Reference numeral 16 is a scanning motor for driving the exposure lamp 11, lens 12, and image sensor 13 to scan the platen glass 14, and 17 is a sensor for determining the home position of the image sensor 13.

Image processing on the image information read by the image sensor 13 is performed by the CCD sensor driving section 18 and the main control section 19, and then the read and image-processed information is sent to the printer 20. It is recorded on recording paper. The scanning motor 16 is controlled by the reader control unit 21 according to the command of the main control unit 19.

When the document is scanned by the image sensor 13 in the above document scanning system, the exposure lamp 11, the lens 12, and the image sensor 13 are reciprocated by the scanning motor 16 in the left-right direction in the drawing, The original table glass 14 is scanned.

Next, the main controller 19 in this embodiment.
Details of the document position detection sequence executed by the CPU in the CPU will be described with reference to the flowchart of FIG.

In step S1, the maximum and minimum coordinates Amax, Amin, Bmax, Bmin of the document 15 in the main scanning direction A and the sub-scanning direction B (see FIG. 4), respectively.
Initializes the memory that stores the. In step S2, a command for starting the first scan of the document 15 is issued to the reader control unit 21. By this command, thereafter, line images of the document 15 are sequentially captured at a constant cycle p until the scanning of the entire surface of the document table glass 14 is completed. In step S3, it is determined whether the first scan is completed, and Amax, Amin, Bmax, Bmin are updated in step S4 until the first scan is completed.

The task of step S4 will now be described in detail with reference to the flow chart shown in FIG.

In step S21, the image data of one line read by the image sensor 13 is transferred to the memory connected to the CPU. In steps S22 and S23,
The original 15 is placed on the line read from the transferred image data.
Is present, and if the line is the first line on which the document 15 exists after the start of scanning, the current reading position is set to Amin. In steps S24 and S25, it is determined whether or not the document 15 exists on the line read from the transferred image data. If the document 15 does not exist and the line is the first line without the document after updating Amin. For example, the current reading position is Amax. In steps S26 and S27, the minimum main-scanning position on the line is calculated and substituted into Tmin so that Tmin is smaller than Bmin or Bmi.
If the initial value of n is -1, Tmin is substituted for Bmin. In S28 and S29, the maximum main scanning position on the line is calculated and substituted for Tmax. If Tmax is larger than Bmax, Tmin is substituted for Bmin.

FIG. 4 shows a line image of the document 15 read in the first scan. Line images are sequentially read on the surface of the platen glass 14 at a cycle p, and the maximum coordinates and minimum coordinates Amax, Amin, in the main scanning direction A and the sub-scanning direction B of the original 15 are read.
Bmax and Bmin are determined.

In step S5, the second copy of the original 15 is performed.
Determine the command that starts the scan. In this command, as shown in FIG. 5, the maximum coordinates and the minimum coordinates Amax, Amin, Bmax, Bmi determined in the first scan.
From n, in the main scanning direction Amax, Amin, Bmax,
A constant range R40, R42, R44 before and after Bmin is calculated, and the calculated range is used as a command parameter. In step S7, a command to start the second scan on the original 15 is issued to the reader controller 21.
Until the scanning of the entire surface of the document table glass 14 is completed, the line images of the document 15 are sequentially captured while switching the document scanning speed in accordance with the command parameters R40, R42, and R44.

In steps S8 and S9, step S3,
Similar to S4, the line image is sequentially read and the original 1
5, the maximum coordinate and the minimum coordinate Amax, Amin, Bmax, Bmin in the main scanning direction A and the sub-scanning direction B, respectively.
To decide. In step S10, Amax, Ami
RAm with n, Bmax, and Bmin as final decision values
Transfer to ax, RAmin, RBmax, RBmin.

FIG. 5 shows an area for scanning a document at low speed in steps S7, S8 and S9. In the reader control unit 21, the maximum coordinates and the minimum coordinates Amax, Amin, Bmax, Bm determined in the first scan are set.
Using in as a parameter, Amax, Ami
Ranges R40, R42, and R44 of n, Bmax, and Bmin in the front and rear direction p in the main scanning direction A are determined. Since the read line image is read at a constant cycle, the range R
At 40, R42, and R44, higher density reading is performed.

Thus, in the second scan, the original position data Amax, Amin, Bmax, Bmin read at low accuracy and high speed in the first scan are used to selectively and highly accurately scan the surface of the original platen glass 14. By scanning at low speed, the maximum coordinate and the minimum coordinate A of the main scanning direction A and the sub-scanning direction B of the document are finally obtained with high accuracy.
Max, Amin, Bmax, Bmin can be determined. At this time, the range of high precision and low speed scanning is
Since it is limited by the first scan, the position of the original can be detected in a shorter time as a whole as compared with the conventional example in which the entire surface of the original platen glass 14 is scanned with high accuracy and low speed.

(Other Embodiments) Next, other embodiments of the present invention will be described. In the above-described embodiment, the document position is detected, but the invention is not limited to the document position. This embodiment relates to document color detection.

Details of the maximum original document color detection sequence executed by the CPU in the main control unit 19 in the above-described embodiment will be described below with reference to the flowchart of FIG.

In step S31, the maximum color R of the original 15
Initialize the memory that stores max, Gmax, Bmax. In step S32, a command to start the first scan of the document 15 is issued to the reader controller 21. By this command, thereafter, line images of the original 14 are sequentially captured at a constant period until scanning of the entire surface of the original glass 14 is completed. In step S33, the first
It is determined whether the scan is completed, and the color histogram is updated in step S34 until the first scan is completed. Here, in the color histogram, each of R, G, and B is divided into 32 levels, and the histogram is created with a low accuracy of 32 × 32 × 32.

In step S35, the maximum color having the maximum number of samples in the low precision histogram is determined, and the constant range of R, G, and B of the maximum color is set as the sampling range of the second scan, and the command of the second scan is determined. Determine the parameters of. This fixed range is determined by the level of decomposition required. In step S36, the document 15
The memory for storing the maximum colors Rmax, Gmax, Bmax of is initialized.

In step S37, a command for starting the second scan of the document 15 is issued to the reader control section 21. After this command, the platen glass 1
4 Until the scanning of the entire surface is completed, the line images of the document 15 are sequentially taken in at a constant cycle.

In step S38, it is determined whether the second scan is completed, and the color histogram is updated in step S39 until the second scan is completed. Here, the color histogram is ignored except for the sampling range obtained in the first scan, and each of R, G, and B is divided into 32 levels within the sampling range, and a histogram is created with high accuracy of 32 × 32 × 32. . In step S40, the maximum color having the maximum number of samples in the high-precision histogram is determined and set as the maximum color of the document.

As described above, the histogram is generated with high accuracy by limiting the area within a certain range before and after the maximum color obtained by the first scan, so that the original 15 can be printed with a small memory capacity of 32 × 32 × 32. It can detect the maximum color,
It is possible to reduce the memory required for the histogram and the calculation time for obtaining the maximum value of the histogram.

In the above-described embodiment, the first and second scanning operations are independent scanning operations for performing reciprocating scanning. However, if the document information can be sampled twice from the platen glass 14, the first document state detection may be performed in the forward pass of one scan operation, and the second document state detection may be performed in the return pass.

Further, in the above-described embodiment, the flat bed type reader is provided. However, a drum-type reader or another type may be used as long as the document information can be sampled from the document multiple times.

[0035]

As described above, according to the present invention,
With the above configuration, high-precision and high-speed document state detection is realized without increasing costs, and high-quality, high-accuracy image formation is realized at low cost using the document state data. The effect of being able to be obtained is obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a reader unit of a digital color copying machine according to an embodiment.

FIG. 2 is a flowchart of a document position detection sequence executed by the CPU of the main control unit according to the embodiment.

FIG. 3 is a flowchart of step S4 in FIG.

FIG. 4 is a diagram showing a line image of a document read in a first scan of the embodiment.

FIG. 5 is a diagram showing an area in which an original is scanned at a low speed in steps S7, S8, and S9 of FIG.

FIG. 6 is a flowchart of a maximum original document color detection sequence executed by a CPU of a main control unit according to another embodiment.

FIG. 7 is a schematic configuration diagram of a reader unit of a conventional image forming apparatus.

8 is a flowchart of document detection in the reader unit of FIG.

9 is a flowchart of step S44 in FIG.

[Explanation of symbols]

 11 exposure lamp 12 lens 13 image sensor 14 platen glass 15 document 16 scanning motor 17 sensor

Claims (2)

[Claims] 1. An image forming apparatus including a document reading unit, a document prescan unit capable of scanning a document before image formation, and a first document state detection unit for detecting a document state by the document prescan. A second original state detecting means for detecting the state of the original by the original prescan, and a second state based on the data from the first original state detecting means.
An image forming apparatus comprising: a means for determining a control method of the document state detecting means. 2. The document prescan by the first document state detecting means is performed on the outward path of one scan operation, and the document prescan is performed by the second document state detecting means on the return path. The image forming apparatus described.