JPH05276331A - Picture reader - Google Patents

Abstract

PURPOSE:To detect a focal state through simple configuration and processing by detecting at least one of a maximum value and a minimum value. of picture data obtained by reading an out of focus pattern with an image sensor and discriminating the focal state based on the detected value. CONSTITUTION:An output signal of an image sensor 25 resulting from main- scanning an out of focus discrimination pattern is converted into a digital signal by an A/D converter 31, the result is given to a shading correction circuit 32, in which shading is corrected and the result is inputted to a maximum value detection circuit 41. The maximum value detection circuit 41 detects a maximum value of the input picture data from a detection operation start timing signal till an end timing signal and gives the detected maximum value to a comparator circuit 43. The comparator circuit 43 compares the maximum value detected by the maximum value detection circuit 41 with a reference value 50 from a register 42 and gives the result of discrimination of out of focus to a CPU 34 when the detected maximum value is the reference value or below. The CPU 34 uses a notice circuit 37 to inform the result to the operator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device capable of detecting a focus state.

[0002]

2. Description of the Related Art In recent years, as an image inputting means in a copying machine, a facsimile machine, an image processing apparatus or the like, an image reading apparatus of a type in which a document image is formed on an image sensor by a lens or the like and the image sensor reads the document image. Is widely used. In this image reading apparatus, focus adjustment is performed before shipping, but the optical system may be displaced due to a shock during transportation or during use, and the focus may be displaced. If this happens, the image will be blurred and accurate image reading will not be possible.

To deal with this, for example, Japanese Patent Laid-Open No. 2-23
7363, JP-A-2-237364, JP-A-2-2
In each of Japanese Patent Laid-Open No. 37365 and JP-A-2-237366, a determination original plate is provided outside the original platen surface, and the determination original plate is read to determine the sharpness of an image to determine a focus state. An image reading apparatus having the above is shown.

[0004]

By the way, in the image reading apparatus disclosed in each of the above-mentioned publications, as a document plate for determination, a document plate formed in a stepwise manner in the vertical direction or a document mounted obliquely in the vertical direction. While using a plate, the original plate is read by a plurality of line sensors, and the focus state is determined by comparing the sum of squares of the differences between the read data of each line sensor between adjacent pixels. for that reason,
There is a problem that the structure and attachment of the determination original plate are complicated and require high precision. Further, there is a problem in that the arithmetic processing is complicated, the circuit scale for that is large, and the cost is high.

Further, in the image reading device, there are variations among the devices in the optical system, the image sensor and the like. Therefore, there is a problem in that the data obtained by reading the determination original plate varies among devices, and it may not be possible to accurately detect the focus state depending on the device.

Therefore, a first object of the present invention is to provide an image reading apparatus capable of detecting a focus state with a simple structure and processing.

A second object of the present invention is, in addition to the first object, to provide an image reading apparatus capable of eliminating variations among apparatuses in detecting a focus state.

[0008]

According to another aspect of the present invention, there is provided an image reading apparatus including an image sensor for reading an original image, and an image forming unit for forming the original image on the image sensor.
By forming a focus shift determination pattern, which is formed at a position readable by the image sensor and in which first density regions and second density regions are alternately arranged, and by reading the focus shift determination pattern by the image sensor, It is provided with a detection means for detecting at least one of the maximum value and the minimum value of the obtained image data, and a determination means for determining the focus state based on the value detected by this detection means.

In this image reading apparatus, at least one of the maximum value and the minimum value of the image data obtained by reading the focus shift determination pattern with the image sensor is detected by the detection means, and the determination means is based on the detected value. Determine the focus state. When the focus shifts, the maximum value of the image data decreases and the minimum value increases, so that the focus state can be determined from at least one of the maximum value and the minimum value.

According to another aspect of the image reading apparatus of the present invention, an image sensor for reading a document image, an image forming means for forming a document image on the image sensor, and a position readable by the image sensor are formed. A focus shift determination pattern in which first density regions and second density regions are alternately arranged, and maximum and minimum values of image data obtained by reading the focus shift determination pattern with an image sensor Detection means for detecting at least one of the above, storage means for storing a value detected by the detection means from image data obtained by reading the focus deviation determination pattern with the image sensor during focus adjustment, and during focus determination The focus state is determined by comparing the value detected by the detection means with the value stored in the storage means. It is obtained by a determination unit.

In this image reading apparatus, when the focus is adjusted, the focus deviation determination pattern is read by the image sensor and the value detected by the detection means is stored in the storage means. Then, at the time of focus determination, the determination unit determines the focus state by comparing the value detected by the detection unit with the value stored in the storage unit. As a result, it is possible to eliminate variations between devices in detecting the focus state.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 relate to a first embodiment of the present invention.

FIG. 1 is an explanatory diagram showing a schematic configuration of a reading unit of the image reading apparatus of this embodiment. As shown in this figure,
The reading unit has a reading unit main body (housing) 11, and a platen glass 12 on which an original 10 is placed is provided on the upper surface of the reading unit main body 11. On the platen glass 12, a document holder 13 that can be opened and closed is provided. Also,
A registration plate 14 is provided on the edge of the platen glass 12 on the sub-scanning start side along the main scanning direction.

FIG. 2 is a bottom view showing the platen glass 12 as viewed from below. As shown in this figure, the registration plate 14 is provided on the platen glass 12 with the original reading area 12a.
Is provided adjacent to the sub scanning direction 72 of the registration plate 14, and a white reference plate 15 for shading correction is provided on the back surface of the registration plate 14, that is, the surface on the platen glass 12 side. In the central portion of 71, a focus deviation determination pattern 16 is formed by printing, for example, outside the area used for shading correction. The focus shift determination pattern 16 is a ladder pattern in which white regions and black regions are alternately arranged at a pitch of 1 lp / mm or less along the main scanning direction. In addition, lp is a set of white line and black line (line pair)
Indicates.

As shown in FIG. 1, below the platen glass 12 is provided a carriage 20 movable in the sub-scanning direction. In the carriage 20, a lamp 21 for illuminating the original 10 in a line and a lamp 21
A reflector 2 that irradiates the original 10 with the light emitted from the document 1.
2 and the first mirror 23 that reflects the reflected light from the original 10.
And are provided. A one-dimensional image sensor 25 for reading a document image is provided at the bottom of the reading unit main body 11, and the light from the first mirror 23 is emitted to the inside of the reading unit main body 11 by one.
A second mirror 26 and a third mirror 27 that lead to the three-dimensional image sensor 25 are provided. In addition, on the optical path in front of the image sensor 25, the original image is read by the image sensor 25.
A lens 28 for forming an image on the top is provided.

The carriage 20 is reciprocated in the sub-scanning direction by a driving device (not shown). The second mirror and the third mirror 27 are moved by a driving device (not shown) in the same direction as the moving direction of the carriage 20 at a speed half that of the carriage 20. As a result, the document surface and the image sensor 25
The document surface can be scanned without changing the distance between them. The focus deviation determination pattern 16 is provided, for example, at a position where the carriage 20 is stopped at the start of normal reading.

FIG. 3 is a block diagram showing a signal processing system of the image reading apparatus. As shown in this figure, the signal processing system is an analog-digital converter (hereinafter referred to as A / D) that converts the output signal of the image sensor 25 into digital image data.
Described as a converter. ) 31, a shading correction circuit 32 that performs shading correction on the output image data of the A / D converter 31, and the shading correction circuit 3
2, an image processing circuit 33 that performs image processing on the output image data, a central processing unit (hereinafter referred to as CPU) 34 that controls the entire image reading apparatus, the image sensor 25, and an A / D converter 31. , Shading correction circuit 3
2, a timing signal generating circuit 35 for supplying a timing signal to the image processing circuit 33 and the CPU 34. The CPU 34 includes a read only memory (hereinafter referred to as ROM) that stores programs and the like, and a random access memory (hereinafter referred to as RAM) that serves as a working area.

The signal processing system of the image reading apparatus further includes a maximum value detection circuit 41 that detects the maximum value of the output image data of the shading correction circuit 32, a register 42 that holds a reference value, and a maximum value detection circuit 41. A comparison circuit 43 that compares the detected maximum value with the reference value 50 held in the register 42, and if the detected maximum value is less than or equal to the reference value, determines that the focus is out of focus and sends the determination result to the CPU 34;
A notification circuit 37 that is connected to the CPU 34 and notifies focus abnormality is provided. The reference value is set in the register 42 by the CPU 34 by preliminarily programming by calculating the maximum value detected by the maximum value detection circuit 41 in a focused state by experiments. Further, the maximum value detection circuit 41 is provided with a timing signal indicating the start and end of the detection operation corresponding to the start and end of the reading of the focus shift determination pattern 16 from the timing signal generation circuit 35. There is.

Further, the output image data of the image processing circuit 33 is sent to a communication control device 61 and an image output device 62 which constitute a facsimile / copy system together with an image reading device, and the communication control device 61 sends an image and outputs an image. Device 6
Image output by 2 is possible. The image received by the communication control device 61 is output by the image output device 62. The CPU 34 is connected to the facsimile device 61 and the image output device 62 via a bus (not shown).

Next, the operation of this embodiment will be described.

First, with reference to FIG. 4, a focus state determination method in this embodiment will be described. The image sensor 25 is provided with the focus deviation determination pattern 16 shown in FIG.
The waveform of the output voltage level obtained by reading with .there is high contrast as shown in FIG. 4 (b) when the focus of the optical system is normal, and the maximum value and the minimum value are white in the focus deviation determination pattern 16, respectively. The output voltage level corresponds to the area and the black area. On the other hand, when the focus is shifted, the waveform of the output voltage level is blurred at the boundary between the white area and the black area as shown in FIG. 4C, and the maximum value is decreased and the minimum value is increased. In the figure, reference numeral d represents the amount of decrease in the maximum value of the output voltage due to focus shift. Therefore,
The focus state can be determined by detecting the maximum value of the image data obtained by reading the focus shift determination pattern 16 and comparing it with a preset reference value.

Next, the operation of this embodiment will be specifically described. In this embodiment, the focus state is determined as a focus shift detection mode at a predetermined time such as when the image reading apparatus is turned on or after every copy. In the focus shift detection mode, first, the carriage 20 is moved to below the registration plate 14, and the focus shift determination pattern 16 on the registration plate 14 is moved.
Is main-scanned by the image sensor 25 and is sequentially read for each pixel. The output signal of the image sensor 25 is converted into digital image data by the A / D converter 31, shading corrected by the shading correction circuit 32, and input to the maximum value detection circuit 41. This maximum value detection circuit 41
Receives a timing signal indicating the start of the detection operation,
The previously detected maximum value is cleared, the maximum value of the input image data until the timing signal indicating the end of the detection operation is received, and the detected maximum value is sent to the comparison circuit 43.

Next, in the comparison circuit 43, the maximum value detected by the maximum value detection circuit 41 and the reference value 5 from the register 42
0 is compared, and when the detected maximum value is equal to or less than the reference value, the determination result of the focus deviation is sent to the CPU 34. The CPU 34, which has received the determination result of the out-of-focus, notifies the notification circuit 37.
The operator is informed of the out-of-focus condition by displaying it on a display device such as a control panel or issuing a warning sound, and informs the operator of the service center or the like using the communication control device 61 of the fact. Automatically send and contact you. In the case of automatic transmission, the CPU 34 sends a message stored in advance in the ROM or the RAM to the communication control device 61 and operates the communication control device 61 to transmit the message.

As described above, according to the present embodiment, since the focus deviation determination pattern 16 does not require so high accuracy, it can be produced and installed by an inexpensive method. In addition, the focus state is detected by the focus shift determination pattern 1.
The maximum value of the image data obtained by reading 6 is detected,
Since it is only compared with the reference value, complicated arithmetic processing is not required and the circuit configuration becomes simple. Further, since the means for notifying the operator or the service center when the focus is defective is provided, it is possible to promptly deal with the focus defect.

In this embodiment, the comparison circuit 43
Then, the focus shift amount may be detected from the magnitude of the difference between the maximum value detected by the maximum value detection circuit 41 and the reference value, and the notification method may be changed according to the focus shift amount.

Further, a minimum value detection circuit is provided in place of the maximum value detection circuit 41, a comparison circuit 43 compares the minimum value detected by the minimum value detection circuit with a reference value, and the detected minimum value becomes the reference. When the value is equal to or more than the value, the determination result of the focus deviation may be sent to the CPU 34.

The difference between the maximum value (or average value) of the output image data obtained by reading the white area of the white reference plate 15 and the maximum value of the image data obtained by reading the focus shift determination pattern 16. May be obtained, and if this difference is greater than or equal to the reference value, it may be determined that the focus is out of focus.

Further, the focus deviation judgment pattern 16 is read in a plurality of lines, the maximum value or the minimum value is detected for each line, the maximum value or the minimum value for each line is averaged, and the average value and the reference value are calculated. May be compared to determine the focus state.

FIG. 5 is a block diagram showing the signal processing system of the image reading apparatus according to the second embodiment of the present invention. In this example,
In contrast to the first embodiment, a nonvolatile RAM 44 which is newly controlled by the CPU 34 and stores the output value of the maximum value detection circuit 41 during focus adjustment as the reference value 51.
Then, a subtraction circuit 45 for calculating the difference between the reference value 51 stored in the RAM 44 and the output value of the maximum value detection circuit 41 is provided, and the output value of the subtraction circuit 45 is input to the comparison circuit 43. Further, in this embodiment, the register 42 is
The allowable error (margin) 52 of the output value of the comparison circuit 43 according to the focus shift is stored, and the allowable error 52 is supplied to the comparison circuit 43. The RAM included in the CPU 34 may also serve as the RAM 44.

In this embodiment, at the time of focus adjustment before shipment of the image reading apparatus or during maintenance, the focus deviation determination pattern 16 is read in a focused state, and the maximum value detection circuit 41 causes the shading correction circuit 32. The maximum value of the image data output from is detected. The CPU 34 uses this maximum value as the reference value 51 for RA
Store in M44. Then, when the focus is determined when the image reading apparatus is used, the reference value 51 stored in the RAM 44 is supplied to the subtraction circuit 45. When the focus is determined, the reference value 5 stored in the RAM 44 by the subtraction circuit 45
The difference between 1 and the output value of the maximum value detection circuit 41 is obtained, and the comparison circuit 43 compares the difference obtained by the subtraction circuit 45 with the allowable error 52 stored in the register 42 and obtains it by the subtraction circuit 45. When the obtained difference is larger than the allowable error 52, it is determined to be out of focus and the determination result is sent to the CPU 34.

As described above, according to the present embodiment, the maximum value detected by the maximum value detection circuit 41 by reading the focus shift determination pattern 16 during focus adjustment is stored, and the maximum value is detected during focus determination. Since the maximum value detected by the circuit 41 is compared with the maximum value at the time of focus adjustment, it is possible to eliminate variations among devices in detecting the focus state.

Other configurations, operations and effects are similar to those of the first embodiment.

FIG. 6 is a block diagram showing a main part of a signal processing system of an image reading apparatus according to the third embodiment of the present invention. In the present embodiment, instead of the maximum value detection circuit 41 in the first embodiment, a maximum value detection circuit 41a and a minimum value detection circuit 41b that detect the maximum value and the minimum value of the output image data of the shading correction circuit 32, and a maximum value detection circuit 41b. A subtraction circuit 46 for calculating the difference between the maximum value detected by the value detection circuit 41a and the minimum value detected by the minimum value detection circuit 41b is provided, and the output value of the subtraction circuit 46 is input to the comparison circuit 43. ing. Further, in this embodiment, the register 42 is
The value to be output from the subtraction circuit 46 in the focused state is stored as the reference value 53.

The waveform of the output voltage level obtained by reading the focus shift determination pattern 16 shown in FIG. 7A with the image sensor 25 is as shown in FIG. 7B when the focus of the optical system is normal. The contrast is large and the difference D between the maximum value and the minimum value is large, but when the focus is shifted,
In the waveform of the output voltage level, the maximum value decreases and the minimum value increases as shown in FIG. 7C, so the difference D between the maximum value and the minimum value decreases. Therefore, the focus state can be determined by comparing the difference D with a preset reference value.

In the present embodiment, the maximum value detection circuit 41a and the minimum value detection circuit 41 in the focus shift detection mode.
b, the maximum value and the minimum value of the image data obtained by reading the focus deviation determination pattern 16 are detected, and the subtraction circuit 46 calculates the difference D between the maximum value and the minimum value. When the difference D obtained by the subtraction circuit 46 is less than or equal to the reference value 53,
The result of determination that the image is out of focus is sent to the CPU 34.

Other configurations, operations and effects are similar to those of the first embodiment.

FIG. 8 is a block diagram showing the essential parts of the signal processing system of the image reading apparatus according to the fourth embodiment of the present invention. In the present embodiment, a nonvolatile RAM 44, which is newly controlled by the CPU 34 and stores the output value of the subtraction circuit 46 at the time of focus adjustment as the reference value 54, in contrast to the third embodiment.
Then, a subtraction circuit 47 for calculating the difference between the reference value 54 stored in the RAM 44 and the output value of the subtraction circuit 46 is provided, and the output value of the subtraction circuit 47 is input to the comparison circuit 43. Further, in the present embodiment, the register 42 stores a permissible error (margin) 55 of the output value of the comparison circuit 43 according to the focus shift, and supplies the permissible error 55 to the comparison circuit 43.

In the present embodiment, the focus deviation determination pattern 16 is read in the in-focus state at the time of focus adjustment before shipment of the image reading apparatus or during maintenance, and the subtraction circuit 46 is used as in the third embodiment. Find the difference between the maximum and minimum values. The CPU 34 stores this difference in the RAM 44 as the reference value 54. Then, at the time of focus determination when the image reading apparatus is used, the reference value 54 stored in the RAM 44 is supplied to the subtraction circuit 47. At the time of focus determination, the subtraction circuit 46 obtains the difference D between the maximum value and the minimum value of the image data obtained by reading the focus shift determination pattern 16, and the subtraction circuit 47 further stores the reference value stored in the RAM 44. 54 and subtraction circuit 4
The difference between the output value D of 6 and the output value D of 6 is calculated, the comparison circuit 43 compares the difference calculated by the subtraction circuit 47 with the allowable error 55 stored in the register 42, and the difference calculated by the subtraction circuit 47 is allowable. When it becomes larger than the error 55, it is determined to be out of focus and the determination result is sent to the CPU 34.

As described above, according to the present embodiment, the focus deviation determination pattern 16 is read during focus adjustment and the difference D between the maximum value and the minimum value detected by the subtraction circuit 46 is stored and the focus determination is performed. Subtraction circuit 46
Since the difference D detected by is compared with the difference D at the time of focus adjustment, it is possible to eliminate the variation between devices in the detection of the focus state as in the second embodiment.

Other configurations, operations and effects are similar to those of the first or second embodiment.

FIG. 9 is an explanatory diagram showing a focus shift determination pattern in the fifth embodiment of the present invention. The focus shift determination pattern 16 shown in FIGS. 2 and 4 is for determining the focus state in the main scanning direction. However, the focus state may be different in the main scanning direction and the sub scanning direction. The cause is that the focal point of the lens 28 is different in the vertical direction and the horizontal direction, or the position shift or inclination of the lens 28 or the carriage 20 is caused.

Therefore, in this embodiment, the focus state in the sub-scanning direction can also be determined. In this example,
As shown in FIG. 9A, on the white reference plate 15, a pattern 16a similar to that of the first embodiment is provided as a focus shift determination pattern 16, and strip-shaped white and black regions extending in the main scanning direction. Both of the ladder-shaped patterns 16b, in which are alternately arranged at a pitch of 1 lp / mm or less along the sub-scanning direction, are provided. Other configurations are similar to those of the first embodiment.

Then, this focus shift determination pattern 1
6a and 16b are read, and the focus state in the main scanning direction and the sub scanning direction is determined based on the change in the waveform of the output voltage level as shown in FIGS. 9 (a) and 9 (b). It should be noted that reference numerals d ₁ and d ₂ in the drawing show the amount of decrease in the maximum value of the output voltage due to the focus shifts in the main scanning direction and the sub scanning direction, respectively. Since the determination of the focus state in the main scanning direction is the same as that in the first embodiment, the description will be omitted. When determining the focus state in the sub-scanning direction, the focus shift determination pattern 16b is read while moving the carriage 20, and the timing signal generation circuit 3 is read.
The maximum value detection circuit 41 is operated at the timing when the image data of each line corresponding to the same pixel of the image sensor 25 is input to the maximum value detection circuit 41 by the timing signal from 5. , The maximum value of the image data of each line corresponding to the same pixel of the image sensor 25 is detected. Then, similarly to the determination of the focus state in the main scanning direction, the focus state in the sub scanning direction is determined by comparing the detected maximum value with the reference value. The determination results in the main scanning direction and the sub scanning direction are sent to the CPU 34.

When determining the focus state in the main scanning direction and the sub-scanning direction, a pair of maximum value detection circuit 41, register 42 and comparison circuit 43 are used to determine the focus state in the main scanning direction and the sub-state. The focus state determination operation in the scanning direction may be performed in order, or two sets of the maximum value detection circuit 41, the register 42, and the comparison circuit 43 for the main scanning direction and the sub-scanning direction are provided to provide the focus state in both directions. It is also possible to make the determination in parallel.

As described above, according to this embodiment, the focus states in both the main scanning direction and the sub-scanning direction can be determined, so that the focus state can be determined more accurately, for example, in the main scanning direction. Even if a focus shift that affects only one of the sub-scanning directions occurs, it can be reliably detected.

Other functions and effects are similar to those of the first embodiment.

FIG. 10 is an explanatory diagram showing a focus shift determination pattern in the sixth embodiment of the present invention. In this embodiment, the focus deviation determination pattern 16 is continuously formed over the entire area in the main scanning direction 71. Then, the focus shift determination pattern 16 is divided into a plurality of regions (for example, three regions), and the focus shift is determined for each region. That is, the focus shift determination pattern 16 is read over one line, and the timing signal generation circuit 35 gives a timing signal indicating the start and end of the detection operation to the maximum value detection circuit 41 for each region. Maximum value detection circuit 4
1 receives the timing signal indicating the start of the detection operation, clears the maximum value detected last time, and detects and detects the maximum value of the input image data until the timing signal indicating the end of the detection operation is received. Maximum value comparison circuit 4
Send to 3. The comparison circuit 43 compares the output value of the maximum value detection circuit 41 and the reference value 50 from the register 42 for each area, determines the focus state, and sends the determination result to the CPU 34. Therefore, if a focus shift occurs in at least one of the plurality of regions, this focus shift can be detected.

As described above, according to this embodiment, the distribution of the focus shift in the main scanning direction can be detected, and the focus state may vary depending on the position in the main scanning direction due to the positional shift or the inclination of the lens. In addition, it is possible to reliably detect the focus shift and to easily find the cause of the focus shift.

The focus shift determination pattern 16 does not have to be formed over the entire area in the main scanning direction 71, and may be divided into a plurality of parts. Further, the focus shift determination pattern 16 may be provided at a plurality of positions in the sub-scanning direction so that the focus shift distribution in the sub-scanning direction can be detected.

Other configurations, operations and effects are similar to those of the first embodiment.

[0051]

As described above, according to the first aspect of the invention, the image sensor reads the focus shift determination pattern in which the first density regions and the second density regions are alternately arranged. By detecting at least one of the maximum value and the minimum value of the image data obtained by, and to determine the focus state based on the value, so high accuracy is not required for the focus deviation determination pattern, There is an effect that the focus state can be detected with a simple configuration and processing without requiring complicated arithmetic processing.

According to the second aspect of the present invention, the focus deviation determination pattern is read by the image sensor during focus adjustment, the value detected by the detection means is stored in the storage means, and is detected during focus determination. Since the focus state is determined by comparing the value detected by the means with the value stored in the storage means, in addition to the above effect, it is possible to eliminate the variation between the devices in the detection of the focus state. effective.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a reading unit of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a bottom view showing the platen glass of FIG. 1 as viewed from below.

FIG. 3 is a block diagram showing a signal processing system of the image reading apparatus of the first embodiment.

FIG. 4 is an explanatory diagram illustrating a method of determining a focus state according to the first embodiment.

FIG. 5 is a block diagram showing a signal processing system of an image reading apparatus according to a second embodiment of the present invention.

FIG. 6 is a block diagram showing a main part of a signal processing system of an image reading apparatus according to a third embodiment of the present invention.

FIG. 7 is an explanatory diagram for explaining a focus state determination method in the third embodiment.

FIG. 8 is a block diagram showing a main part of a signal processing system of an image reading apparatus according to a fourth embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining a focus state determination method according to a fifth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a focus shift determination pattern according to the sixth embodiment of the present invention.

[Explanation of symbols]

16 ... Focus deviation determination pattern, 20 ... Carriage,
25 ... Image sensor, 34 ... CPU, 41 ... Maximum value detection circuit, 42 ... Register, 43 ... Comparison circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Nakajima, 3-7-1, Fuchu, Iwatsuki City, Saitama Prefecture, Fujiwa Rocks Co., Ltd., Iwatsuki Plant (72) Kuniomi Hasegawa, 3-7-1, Fuchu, Iwatsuki City, Saitama Prefecture Issue Fuji Xerox Co., Ltd. Iwatsuki Plant (72) Inventor Yasuo Komatsu 3-7-1, Fuchu, Iwatsuki City, Saitama Prefecture Fuji Zerox Co., Ltd. Iwatsuki Plant (72) Atsushi Takahashi 3-7, Iwatsuki City, Saitama Prefecture No. 1 inside Fuji Xerox Co., Ltd. Iwatsuki Plant

Claims (2)

[Claims] 1. An image sensor for reading an original image, an image forming unit for forming the original image on the image sensor, a first density region formed at a position readable by the image sensor, and a second density region. And a detection unit for detecting at least one of the maximum value and the minimum value of the image data obtained by reading the focus deviation determination pattern with the image sensor. An image reading apparatus comprising: a determining unit that determines a focus state based on a value detected by the detecting unit. 2. An image sensor for reading a document image, an image forming unit for forming a document image on the image sensor, a first density region formed at a position readable by the image sensor, and a second density region. And a detection unit for detecting at least one of the maximum value and the minimum value of the image data obtained by reading the focus deviation determination pattern with the image sensor. A storage unit for storing a value detected by the detection unit from image data obtained by reading the focus shift determination pattern with an image sensor during focus adjustment; and a detection unit detected by the detection unit during focus determination. Determination means for determining the focus state by comparing the value with the value stored in the storage means Image reading apparatus characterized by comprising.