JP2005184173A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader quickly starting reading without the need for addition of particular hardware to the image reader. <P>SOLUTION: The image reader is provided with: a light source 28 for emitting light to an original; a CCD image sensor 21 for applying photoelectric conversion to the light from the original to generate an image signal; image signal processing means (an AFE circuit 22, an A/D conversion section 23, and a scanner image processing circuit 24 or the like) for processing the image signal from the CCD image sensor 21; a test chart 32; and a discrimination circuit 40 for discriminating the lightness of the light source 28 on the basis of the image signal obtained when the test chart 32 is read. The AGC circuit 22b of the AFE circuit 22 adjusts the gain on the basis of a discrimination result (lightness of the light source 28) from the discrimination circuit 40. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus used in a copying machine, a facsimile machine, a multifunction machine having both a copying function and a facsimile function, for example, using a fluorescent tube or a cold cathode tube as a light source.

When a fluorescent tube or a cold cathode tube is used as a light source for illuminating a document by the image reading apparatus, there is a problem that it takes time until the predetermined amount of light is reached after the fluorescent tube or the cold cathode tube is turned on. One approach to solve this is to increase the applied voltage or frequency during lighting, rapidly increase the amount of light, monitor the amount of light with a separately provided light amount sensor, and when the amount of light is stable, read the image. There is a method of starting (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 10-285338

  However, according to the prior art, a configuration in which a light amount sensor is provided or the voltage (or frequency) of an inverter that applies a voltage to a fluorescent tube or a cold cathode tube is variable is required, which increases the cost of the apparatus. was there.

  The present invention has been made paying attention to such problems, and an object of the present invention is to provide an image reading apparatus capable of starting reading at an early stage without adding special hardware.

  In order to achieve the above object, an image reading apparatus of the present invention includes a light source that irradiates light on a document, a reading unit that photoelectrically converts light from the document, and an image signal from the reading unit. The image signal processing means for processing includes a test chart and a determination means for determining the brightness of the light source based on the image signal when the test chart is read, and based on the determination result of the determination means, the image The image signal processing of the signal processing means is changed.

  In this image reading apparatus, the image signal processing can be changed by varying the gain of the amplifying means in the image signal processing means according to the brightness of the light source determined by the determining means, or by the determining means. Depending on the determined brightness of the light source, the gamma correction characteristic in the image signal processing means is varied.

  According to the present invention, by applying image processing according to the brightness of the light source, it is possible to read an image until the light source is completely stabilized, and to shorten the time for which the user waits. . Further, it is not necessary to add new hardware by changing constants of existing circuits such as AGC and gamma correction tables or contents of tables.

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

  FIG. 1 is a block diagram showing a configuration example of a facsimile apparatus as an image reading apparatus according to the embodiment. This facsimile apparatus is configured as a multifunction machine having both a facsimile function and a copy function.

  The facsimile apparatus includes a CPU (Central Processing Unit) 1 as a main control unit, an NCU (Network Control Unit) 2, a MODEM 3, a ROM 4, a RAM 5, an image memory 6, and a display unit 7. , An operation panel 8, an image reading unit 9, a printer 10, and a CODEC (Coder and Decoder) 11, which are connected via a bus 13.

  The CPU 1 comprehensively controls each part constituting this apparatus according to a program stored in the ROM 4. The NCU 2 is controlled by the CPU 1 to control connection with the public telephone line network (PSTN) 14 that is a communication line and to send a dial pulse corresponding to the telephone number (including FAX number) of the communication partner. And a function of detecting an incoming call.

  MODEM3 is an ITU (International Telecommunication Union) -T recommendation T.264. 30, T.M. 4 according to the facsimile transmission control procedure (facsimile communication procedure) according to FIG. 17, V. 27ter, V.I. The transmission data is modulated and the received data is demodulated in accordance with 29. The MODEM 3 also has a function of modulating transmission data, which is a digital signal, into an analog voice signal for transmission to the public telephone line network 14 via the NCU 2, and an analog received from the public telephone line network 14 via the NCU 2. The audio signal is demodulated into a digital signal.

  The ROM 4 stores a program for controlling the operation of the entire apparatus. The RAM 5 stores data necessary for control by the CPU 1 and data that needs to be temporarily stored during the control operation. The image memory 6 encodes the image data read by the image reading unit 9 and stores it in a compressed state. The image memory 6 has a storage area for storing encoded and compressed data and a storage area for storing image data obtained by decoding the image data stored in the storage area.

  The display unit 7 displays icons, key buttons, message contents necessary for data transmission / reception, telephone numbers and FAX numbers input from the operation panel 8, and the like. As the display unit 7, an LCD (Liquid Crystal Display) is used. The operation panel 8 includes a numeric keypad, a mode switching key, a one-touch key, an abbreviated key, a registration key, a start key, a stop key, and the like.

  The image reading unit 9 includes a CCD image sensor 21 serving as reading means, an AFE (analog front end) circuit 22, an A / D conversion unit 23, a scanner image processing circuit 24, a scanner mechanism control circuit 25, and an inverter 27. And a cold cathode tube 28 as a light source. Here, the AFE circuit 22, the A / D converter 23, the scanner image processing circuit 24, and the like constitute an image signal processing means.

  The CCD image sensor 21 reads an image of one scanning line of an original illuminated with light from the cold cathode tube 28, and sequentially reads the next scanning line image at a predetermined interval. The AFE circuit 22 analog-amplifies the output of the CCD image sensor 21. The A / D converter 23 converts the analog output of the AFE circuit 22 into a digital signal. The scanner image processing circuit 24 performs image processing such as shading correction and gamma correction on the input digital image signal. The scanner mechanism control circuit 25 controls a carriage motor (not shown) of the scanner mechanism unit and also controls a driving voltage applied from the inverter 27 to the cold cathode tube 28.

  The printer 10 is of an electrophotographic system, and records received image data and image data of a document read by the image reading unit 9 in a copying operation on a recording sheet. The CODEC 11 encodes (encodes) the read image data by the MH, MR, MMR method, or the like in order to transmit or store the read image data. Also, the CODEC 11 decodes (decodes) the image data received in a compression-coded state for recording by the printer 10.

  The feature of this facsimile apparatus is that the brightness of the light source (cold cathode tube 28) is determined based on the image signal when the test chart 32 described later is read, and the image signal processing of the image signal processing means is changed based on the determination result. The change in the image signal processing includes (1) varying the gain of the AGC circuit 22b described later in the image signal processing means in accordance with the brightness of the light source determined by the determination circuit 40 described later. ) Varying the gamma correction characteristics in the image signal processing means according to the brightness of the light source determined by the determination circuit 40, (3) The reference voltage (Vref) at the time of conversion by the A / D conversion unit 23 To change.

  Next, the feature points will be described. FIG. 2 shows a scanner mechanism unit and a scanner circuit unit of the image reading unit 9 of the facsimile apparatus. A test chart 32 is attached to the lower surface of the support plate 30 that supports the glass substrate 31 on which the document is placed. As shown in FIG. 3, the test chart 32 has gradation in the main scanning direction (longitudinal direction), and is arranged with the longitudinal direction facing the main scanning direction. By irradiating the test chart 32 with light from the cold cathode tube 28 and receiving it with the CCD image sensor 21, the light quantity of the cold cathode tube 28 (light source) can be accurately detected.

  An optical system 38 including a CCD image sensor 21, a cold cathode tube 28, mirrors 34, 35, and 36 and a lens 37 is disposed below the support plate 30 and the glass substrate 31, and this optical system 38 is arranged in the main scanning direction by a carriage. It is configured to be movable.

  The AFE circuit 22 includes a sample hold (S / H) circuit 22a that captures an image signal from the CCD image sensor 21, and an AGC circuit 22b that amplifies the output and adjusts the gain. The scanner image processing circuit 24 includes a shading correction circuit 24a, a γ correction table 24b, and a binarization circuit 24c.

  The shading correction circuit 24a performs shading correction using the shading correction data stored in the shading RAM and outputs the output of the A / D conversion unit 23 at the time of reading the document. Here, the γ correction table 24b stores tables corresponding to condition 0, condition 1, and condition 2, respectively, and outputs a shading correction output by using the γ correction characteristics.

  In addition, a determination circuit 40 is provided as a determination unit that determines the brightness of the cold cathode tube 28 based on an image signal (shading correction output) obtained when the test chart 32 is read. Here, Condition 0, Condition 1, and Condition 2 are set according to the brightness of the cold cathode tube 28 (light source) when the test chart 32 is read (see FIG. 3).

  Next, a case where the change (1) of the image signal processing is performed will be described. When the cold cathode tube 28 is turned on when starting document reading, the light from the cold cathode tube 28 is applied to the test chart 32, and the test chart 32 (its gradation image) is read. The determination circuit 40 determines the shading correction output from the shading correction circuit 24 a of the scanner image processing circuit 24, that is, the brightness of the cold cathode tube 28. Here, the determination circuit 40 determines whether the condition 0, condition 1, or condition 2 is satisfied according to the brightness of the light source as shown in FIG.

  The determination circuit 40 inputs the determination result to the AGC circuit 22 b of the AFE circuit 22. The AGC circuit 22b adjusts the gain according to the input determination result. For example, in condition 2, the gain is increased, conversely, in condition 0, the gain is decreased, and in condition 1, the gain is set to the middle.

  FIG. 4 shows the relationship between the time from when the cold-cathode tube 28 is turned on until the reading of the original starts and the brightness of the light source. The brightness (light emission amount) of the light source becomes substantially constant after time t4, but in this embodiment, the document is satisfied under condition 2 from time t1 to time t2 during which the brightness increases without waiting for that time. The second page of the original is read under condition 1 from time t2 to time t3, and the third page of the original is read under condition 0 from time t3 to time t4. As described above, by adjusting the gain, even when the light emission output of the cold cathode tube 28 (light source) is stabilized, it is possible to perform the same reading as when reading with a constant light emission amount. Thereby, the time which makes a user wait can be shortened.

  When changing the image signal processing (2), as described above, the scanner image processing circuit 24 stores the tables corresponding to the conditions 0, 1 and 2 as the γ correction table 24b. The selector 41 for selecting any one of the tables is provided, and the γ correction table corresponding to the result (condition 0, condition 1, condition 2) determined by the determination circuit 40 is selected by the selector 41. FIG. 5 shows γ correction curves selected corresponding to these conditions 0, 1 and 2.

  In this case, if the brightness of the light source determined by the determination circuit 40 corresponds to, for example, the condition 0, the output subjected to the shading correction by the shading correction circuit 24a is gamma corrected using the γ correction table corresponding to the condition 0. It is output to the binarization circuit 24c. In this case as well, the image can be read and the waiting time of the user can be shortened until the light source is completely stabilized as described above.

  When changing the image signal processing (3), the determination circuit 40 inputs the shading correction output from the shading correction circuit 24a of the scanner image processing circuit 24 when the test chart 32 is read to the D / A converter 42. To do. The D / A converter 42 converts the input shading correction output into an analog value, and provides the analog value to the A / D converter 23 as a reference voltage (Vref). The reference voltage (Vref) applied to the A / D converter 23 is changed according to the shading correction output, that is, the brightness of the cold cathode tube 28, and the dynamic range of the A / D converter 23 is changed. Is done. Therefore, even if the image signal input from the AFE circuit 22 is the same, the output of the A / D conversion unit 23 varies depending on the brightness of the cold cathode tube 28.

  In the above embodiment, the determination circuit 40 determines the brightness of the cold cathode tube 28 (light source) in three stages of condition 0, condition 1, and condition 2, and changes the image signal processing based on the determination. However, the image signal processing may be changed at each stage by dividing into two stages or more stages than three stages.

  In the above embodiment, when the gain of the AFE circuit 22 is made variable according to the brightness of the cold cathode tube 28 (light source) [change of image signal processing (1)], the gamma correction of the scanner image processing circuit 24 is performed. The case of changing the characteristics [change of image signal processing (2)] and the case of changing the reference voltage (Vref) at the time of conversion by the A / D converter 23 [change of image signal processing (3)] will be described. However, these may be used in appropriate combination.

1 is a block diagram illustrating a configuration example of a facsimile apparatus (a multi-function machine having both a facsimile function and a copy function) according to an embodiment. FIG. 2 is a block diagram illustrating a scanner mechanism unit and a scanner circuit unit of an image reading unit of the facsimile apparatus. It is a figure which shows the condition 0, the condition 1, and the condition 2 selected according to the brightness | luminance of the light source when the test chart used in the same facsimile machine and a test chart are read. FIG. 6 is a diagram illustrating a relationship between a time from when a light source is turned on until reading of a document is started and brightness of the light source in the facsimile apparatus. It is a figure which shows each (gamma) correction curve corresponding to the conditions 0, the conditions 1, and the conditions 2 shown in FIG.

Explanation of symbols

1 CPU
9 Image reading unit 21 CCD image sensor (reading means)
22 AFE (Analog Front End) Circuit 22a Sample Hold Circuit 22b AGC Circuit 23 A / D Converter 24 Scanner Image Processing Circuit 24a Shading Correction Circuit 24b Gamma Correction Table 24c Binarization Circuit 28 Cold Cathode Tube (Light Source)
32 Test chart 38 Optical system 40 Judgment circuit (judgment means)
41 selector 42 D / A converter

Claims (3)

In an image reading apparatus comprising: a light source that irradiates light on a document; a reading unit that photoelectrically converts light from the document to generate an image signal; and an image signal processing unit that processes an image signal from the reading unit;
A test chart; and a determination unit that determines the brightness of the light source based on an image signal obtained by reading the test chart, and the image signal processing of the image signal processing unit is changed based on a determination result of the determination unit. An image reading apparatus.   2. The image reading apparatus according to claim 1, wherein the gain of the amplification means in the image signal processing means is varied according to the brightness of the light source determined by the determination means.   2. The image reading apparatus according to claim 1, wherein the gamma correction characteristic in the image signal processing means is varied in accordance with the brightness of the light source determined by the determination means.

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