JP2005303560A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading apparatus capable of preventing an image from being deteriorated due to saturation of electric charges resulting from maximally received light. <P>SOLUTION: The image reading apparatus is provided in which a light source inverter 15 supplies a drive current to a cold cathode tube 16 as a light source of illuminating the original via a switch 17 to glow the cold cathode tube 16, the light from the cold cathode tube 16 is reflected in the original and a CCD sensor 18 receives the reflected light for reading the image of the original. In the image reading apparatus, the switch 17 is turned ON / OFF for a reading period by a command from an MPU 1 to intermittently glow the cold cathode tube 16 thereby suppressing an amount of light received by the CCD sensor 18 and reducing saturation of the electric charges. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image reading apparatus having an image reading function having a light source and a photoelectric conversion element.

  Copiers, facsimile machines, multifunction machines with multiple functions such as copying / facsimile functions, and scanners receive a light source for projecting light onto a document and that light from this light source is reflected off the document surface. However, it is known to have an image reading device including a photoelectric conversion element (CCD) for reading a document image.

By the way, in this type of image reading apparatus, attention is paid to a shutter closing signal that controls the exposure time of the photoelectric conversion element in order to prevent heat generation and light amount change of the light source, and the light source is turned off based on the shutter closing signal. A lighting control method is disclosed (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 10-233891

  In recent years, cold cathode tubes and fluorescent tubes used as the light source of the image reading apparatus tend to increase the amount of light due to a demand for improvement in reading speed, and the light receiving sensitivity of a CCD (photoelectric conversion element) is also improved. For this reason, when the light source is continuously turned on and the CCD receives reflected light from the document, the photocell may be saturated with electric charge and the image may be blurred.

  The present invention has been made paying attention to the above problems, and an object thereof is to provide an image reading apparatus capable of preventing image deterioration due to charge saturation.

  Note that the technique described in Patent Document 1 uses a shutter closing signal that controls the exposure time of a color signal and turns off the light source during that period, so it is difficult to reduce charge saturation.

  An image reading apparatus according to the present invention is an image reading apparatus including a light source that illuminates a document, a lighting circuit that turns on the light source, and a photoelectric conversion element that receives reflected light from the document and converts it into an electrical signal. Control means for controlling a lighting circuit to intermittently light the light source within a line reading period is provided.

  According to another aspect of the present invention, there is provided an image reading apparatus including: a light source that illuminates a document; a lighting circuit that lights the light source; and a photoelectric conversion element that receives reflected light from the document and converts the light into an electrical signal. Control means for opening and closing a circuit connecting the lighting circuit and the light source so as to intermittently light the light source within a period of one line reading is provided.

  In the image reading apparatus according to the present invention, it is preferable that the received light amount of the photoelectric element in the one-line reading period is controlled to be equal for each line.

  According to the present invention, since the light source is intermittently lit within the reading period of one line, the amount of light received by the photoelectric conversion element is reduced by that amount, so that deterioration of the image due to charge saturation can be prevented.

  In addition, since the light reception within the reading period of each line is made uniform, it is possible to further prevent image degradation.

  Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a block diagram showing a circuit configuration of a multifunction machine according to an embodiment of the present invention. The MFP according to this embodiment includes an MPU 1, an NCU (Network Control Unit) 2, a MODEM 3, a ROM 4, a RAM 5, an image memory 6, an image reading unit 7, and a CODEC (encoder / decoder). (Corder and Decoder) 8, a display unit 9, an operation unit 10, a printer 11, and a bus 12.

  The MPU 1 executes the processing operation of the entire apparatus according to the program stored in the ROM 4. The NCU 2 is controlled by the MPU 1 to control connection with a telephone network (PSTN) 13 that is a communication line. Further, the NCU 2 has a function of sending a dial pulse corresponding to a telephone number (including a FAX number) of a communication partner and a function of detecting an incoming call.

  MODEM3 is an ITU (International Telecommunication Union) -T recommendation T.264. 30, T.M. Based on 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. MODEM3 is a V. 8, V. 34 is also applicable to Super G3 FAX. Specifically, the MODEM 3 has a function of modulating transmission data, which is a digital signal, into an analog signal in order to send it to the telephone line network 13 via the NCU 2. The MODEM 3 has a function of demodulating an analog voice signal received from the telephone line network 13 via the NCU 2 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 MPU 1 and data that needs to be temporarily stored during the control operation. The image memory 6 stores image data received from an external device such as a personal computer via a network or image data read from a recording medium in a compressed state (JPEG or the like).

  The image reading unit 7 optically scans and reads image data of a document when performing facsimile transmission or copying. The image reading unit 7 can also read a color image. In the case of color reading, the image reading unit 7 optically scans a document image, obtains RGB color separation signals, and performs predetermined image processing. The image reading unit 7 will be described in detail later.

  The CODEC 8 encodes (encodes) the read image data by the MH, MR, MM method or the like in order to transmit or store the image data. Also, the CODEC 8 decodes (decodes) the image data received in the compressed and encoded state for recording by the printer 11.

  The display unit 9 displays icons, key buttons, message contents necessary for data transmission / reception, input telephone numbers, FAX numbers, and the like by operation of the operation unit 10. As the display unit 9, an LCD (Liquid Crystal Display) is used. The operation unit 11 includes keys such as a numeric keypad, a one-touch key, an abbreviated key, a mode switching key, a start key, and a stop key. The printer 11 employs an electrophotographic system, and records received image data and image data of a document read by the image reading unit 7 on a recording sheet in a copying operation.

  The image reading unit 7 includes a scanner mechanism control circuit 14, a light source inverter 15, a cold cathode tube 16, a switch 17, a CCD sensor 18, an analog front end circuit 19, an A / D converter 20, and a scanner image. And a processing circuit 21.

  The scanner mechanism control circuit 14 drives a motor 14 a that moves the scanner mechanism in response to a command from the MPU 1 and inputs a lighting signal to the light source inverter 15. The light source inverter 15 sends a lighting current to the cold cathode tube 16 via the switch 17 to light the cold cathode tube 16. The switch 17 is turned on / off by a signal from the MPU 1.

  The CCD sensor 18 is a line image sensor for scanning and reading a document image. The CCD sensor 18 receives a sample hold signal SH from the scanner image processing circuit 21 and accumulates charges corresponding to the amount of received light. The analog front end circuit 19 amplifies the analog signal output from the CCD sensor 18. The A / D converter 20 converts the analog output signal of the analog front end circuit 19 into a digital signal. The scanner image processing circuit 21 performs image processing such as shading correction, gamma correction, and binarization processing on the read image data digitally converted by the A / D converter 20. The read image data subjected to image processing is encoded by the CODEC 8 and stored in the image memory 6.

  When the image reading unit 7 performs a reading operation, the cold cathode tube 16 that is a light source of the scanner is turned on. In this embodiment, the cold-cathode tube 16 is controlled to blink every reading cycle of one line by the CCD sensor 18. The CCD sensor 18 reads one line for every application period of the sample hold signal SH shown in FIG. 2A shows the progress of the read timings n, n + 1, n + 2, n + 3,..., And FIG. 2E shows the read data for each line.

  As shown in FIG. 2C, the lighting pattern of the cold cathode tube 16 is ON / OFF once with a duty ratio of 1/2 in one line reading cycle. A control signal having a pattern shown in FIG. 2C is supplied from the MPU 1 to the scanner mechanism control circuit 14, and the light source inverter 15 is turned ON / OFF by a signal corresponding to this waveform. Further, instead of turning on / off the operation of the photoelectric inverter 15, the cold cathode tube 16 may be turned on intermittently by turning on / off the switch 17 with a signal shown in FIG. .

  Further, as shown in FIG. 2D, the duty ratio of the cold cathode tube 16 is 1/2 as in the case of FIG. 2C, as shown in FIG. It is possible to repeat the OFF twice.

  In this embodiment, the cold cathode fluorescent lamp (light source) is intermittently lit within the reading period of one line. Therefore, the amount of light received by the CCD sensor (photoelectric conversion element) is reduced, and the image is deteriorated due to charge saturation. Can be prevented.

  The present invention can be applied regardless of whether the scanner is an automatic document feeder (ADF) scanner or a flatbed scanner (FBS).

1 is a block diagram illustrating a configuration of a multifunction machine according to an embodiment of the present invention. 6 is a time chart for explaining lighting control of a light source of an image reading unit of the MFP.

Explanation of symbols

1 MPU
2 NCU
3 MODEM
4 ROM
5 RAM
6 Image memory 7 Image reader 8 CODEC
DESCRIPTION OF SYMBOLS 9 Optical part 10 Operation part 11 Printer 14 Scanner mechanism control circuit 14a Scanner drive motor 15 Light source inverter 16 Cold cathode tube 17 Switch 18 CCD sensor 19 Analog front end circuit 20 A / D converter 21 Scanner image processing circuit

Claims (3)

In an image reading apparatus comprising a light source that illuminates a document, a lighting circuit that lights the light source, and a photoelectric conversion element that receives reflected light from the document and converts it into an electrical signal,
An image reading apparatus comprising control means for controlling a lighting circuit to intermittently light the light source within a period of one line reading. In an image reading apparatus comprising a light source that illuminates a document, a lighting circuit that lights the light source, and a photoelectric conversion element that receives reflected light from the document and converts it into an electrical signal,
An image reading apparatus comprising control means for opening and closing a circuit connecting a lighting circuit and a light source so that the light source is intermittently lit during a period of one line reading.   3. The image reading apparatus according to claim 1, wherein the light receiving amount of the photoelectric element in the one line reading period is controlled to be equal in each line. 4.

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