JPS60145763A - Original reading device - Google Patents

Abstract

PURPOSE:To set proper preliminary lighting time avoiding loss by providing a device that measures rate of change of quantity of light of a light source in an original reading device and making time until the rate of change of light quantity of the light source after lighting becomes a prescribed value preliminary lighting time. CONSTITUTION:A photoelectric converting element 8 is placed on the side of an illuminating light source 7, and the quantity of light of the light source 7 is detected by a plate 9 having a reflecting face placed on an original platen 2. When reading start signal of an original 1 is received, the illuminating light source 7 puts the light on, and the quantity of light changes following a prescribed curve. The converting element 8 detects change of this quantity of light, and gives the detection signal to a comparator 10. When the detected quantity of light arrives at a reference level, that is, when the quantity of light arrives at saturation level, the comparator 10 generates output D. After generation of this output, reading mechanisms such as the illuminating light source 7, reflecting mirror 3 etc. start moving, and reading of the original is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a document reading device that breaks down image information on a document into minute parts and reads them as electrical signals.

<Prior Art> Recently, in addition to the conventional processing of code information, processing as image information has been implemented.

In this image processing, a document reading device functions as an input unit for inputting image information. Initially, the input section of a facsimile machine was used as the original document reading device, but as there was a demand for inputting image information faster and more precisely,
Dedicated manuscript reading devices became available.

Furthermore, there is now a need for a document reading device that can suitably handle various kinds of documents, such as book-shaped documents, without being limited to sheet-shaped documents.

Here, the general structure of the document reading device will be explained.

The reading element uses a lyomage sensor in which a plurality of pixels are arranged in a straight line. The typical one is IC
The sensor is a CCD light/noise sensor.

The length of the sensor is usually less than 30m.

On the other hand, the reading width of a document is, for example, the short side of A3 paper is 29
It is as wide as 7 m, and therefore requires an optical system to focus the image of the document as a reduced image on the second pixel of the sensor.

A lens unit composed of a plurality of lenses is used as this optical system.

Further, when reading a document, light is irradiated by an illumination light source such as a halogen lamp or a fluorescent lamp.

The document, the sensor, the lens unit, and the illumination light source described in l- move relative to each other in a direction perpendicular to the reading line, and correspondingly, electrical signals corresponding to the contents of the document are sequentially extracted from the pixels of the sensor. The resulting document content information is converted into electrical signals.

Methods for relatively moving the document, sensor, lens unit, and illumination light source include a method in which the document is moved using a feed roller, a method in which the document table on which the document is placed is moved, and a method in which the document is fixed and the lens unit and sensor are moved relative to each other. There is also a method in which the illumination light source moves together, and a method in which the document, lens unit, and sensor are fixed and the reflecting mirror and the illumination light source are moved in the middle of the optical path.

Therefore, we will discuss the above-mentioned document reading device in which the reflection mirror and the illumination light source move in the middle of the optical path.

FIG. 1 shows the structure of the document reading device.

In the figure, a document 1 is placed on a document table 2 made of transparent glass. At this time, the original 1 is placed so that the surface to be read is in contact with the original table 2.

The image of the document 1 on the document table 2 passes through a reflection mirror 3 and a reflection mirror 4, and is formed as a reduced image on a pixel surface of a reading element section 6 by a reading lens unit 5.

When the reading of the original is started, the illumination light source 7 starts to move and illuminates the reading part of the original 1 through the original platen 2 with a brightness that allows the reading element section 6 to sufficiently read the information of the original image.

Subsequently, the illumination light source 7 and the reflection mirror 3 start moving in the direction indicated by arrow A while maintaining the same distance from the original 1.

In synchronization with this, the reflecting mirror 4 starts moving in the direction of arrow B by a moving amount that is half the moving amount of the illumination light source 7 and the reflecting mirror 3.

Therefore, the optical path length from the document surface to the reading element section 6 is kept the same despite the movement of the illumination light source 7 and the reflecting mirrors 3 and 4.

In this way, all information on the document surface is transmitted to each pixel on the reading element section 6 by moving the illumination light source 7 and the reflection mirror 3 below the document I from right to left in the figure.

At this time, an electrical signal is extracted from the reading element section 6 at a timing corresponding to the amount of movement of the illumination light source 7 and the reflecting mirror 3, depending on the brightness of the image formed.

When the document reading is completed, the illumination light source 7 is turned off,
The illumination light source 7 and the reflecting mirrors 3 and 4 start moving in the opposite direction to the reading direction and return to their initial set positions.

Incidentally, when reading starts, the illumination light source 7 is turned on, but the light amount of the illumination light source 7 does not instantly reach a constant value, but gradually increases and gradually converges to a constant value.

Therefore, the lighting and reading operations will be explained using the timing chart shown in FIG. 2.

When the reading command signal S1 is input, the illumination light source turn-on signal S2 is output at the same time to instruct lighting, but the signal S3 that operates the drive device that moves the illumination light source 7 and the reflection mirrors 3 and 4 is The signal S2 was output after a predetermined time (preliminary lighting time) T had elapsed after the signal S2 was output.

As shown in FIG. 3, the intensity of light from the illumination light source 7 varies when the temperature inside the illumination light source 7 is high (as shown by curve a) and when the temperature inside the illumination light #j7 is low (as shown by the curve a). There is a difference between the two. That is, when the temperature inside the illumination light source 7 is high, the light amount rises faster than when the temperature inside the illumination light source 7 is low.

That is why, conventionally, the above-mentioned time T is the illumination light source 7
It was determined with some margin so that even if the internal temperature is low and the light intensity rises slowly, the change in light intensity will be small within the reading time.

However, when reading operations are performed continuously, at the start of reading, the temperature inside the illumination light source 7 is high due to residual heat from lighting during the previous reading operation, and the light intensity of the illumination light source 7 inevitably increases. It becomes early.

Therefore, in conventional document reading devices, there is an unnecessary pre-lighting time during high-speed continuous reading.

<Object of the Invention> In view of the above, the present invention provides a document reading device with a means for measuring the rate of change in the light amount of the light source, and measures the time it takes for the rate of change in the light amount of the light source of the light source to reach a predetermined value. To set an appropriate preliminary lighting time without waste as a preliminary lighting time.

<Example> The configuration of the present invention will be described below along with examples.

FIG. 4 shows a structural diagram of a document reading device according to an embodiment of the present invention.

In the figure, since the configuration of the main body of the apparatus is equivalent to that shown in FIG. 1, the same parts are given the same reference numerals.

Point C on the document table 2 is a point where image information is transmitted to the reading element section 6 through the reflecting mirrors 3, 4 and the reading lens unit 5 when the main body of the document reading apparatus is in a standby state before starting the reading operation, and is the point where image information is transmitted to the reading element section 6 through the reflecting mirrors 3, 4 and the reading lens unit 5. This is the location that is illuminated by the illumination light source 7 when the illumination light source lighting signal S2 is output and the illumination light source 7 is turned on.

A photoelectric conversion element 8 is arranged opposite to point C of the document table 2. At this time, the photoelectric conversion element 8 is attached so that its light receiving portion faces the document table.

When the illumination light source 7 is turned on, the light receiving section of the photoelectric conversion element 8 receives the light from the illumination light source 7 through the document table 2. The amount of light received by the photoelectric conversion element 8 is amplified and detected as a potential difference at an output pin D of a circuit electrically connected to the photoelectric conversion element 8. Therefore, in the output bin D, the rate of change in the current of the circuit, that is, the rate of change in the amount of light can be measured.

Next, the relationship between the rate of change in light amount of the illumination light source 7 and the start of reading will be described.

In FIG. 5, (a) shows the change in the amount of light from when the illumination light source 7 is turned on, (b) shows the rate of change in the amount of light that can be measured at the output point D, and (c) shows the change in the amount of light that can be measured at the output point D. The timing waveform is shown.

As can be clearly seen in Figure 5 (a), middle), the document reading start command signal is input (at time (1), the illumination light source 7 is turned on, and as shown by the curve in (a), the amount of light is (Current according to the amount of light) changes.Correspondingly, the rate of change in the amount of light changes as shown in the curve (b).This rate of change in the amount of light changes to a preset reference level (indicated by the broken line) When reaching (time 12), the illumination light source 7 and reflection mirrors 3 and 4 start moving, and reading of the document is executed.

Thus, in this embodiment, the preliminary lighting time of the illumination light source 7 is set as the time from the time t1 to the time t2.

In the above embodiment, a fluorescent lamp or the like is specifically used as the illumination light source 7, and the sensor of the reading element section in the above embodiment is not limited to a CCD.

FIG. 6 shows a partial structural diagram of a document reading device according to another embodiment of the present invention.

In the figure, parts that are the same as those in the previous embodiment are given the same reference numerals.

In this embodiment, the photoelectric conversion element 8 is placed on the side surface of the illumination light source 7, and a reflective surface placed on the document table 2 (on the surface of the document table 2 opposite to the surface facing the illumination light source 7) The light amount of the illumination light source 7 is detected by passing through the reflective surface of the plate 9 using a plate 9 having the following structure. The other parts are the same as those in the above embodiment.

Effect> As described above, according to the present invention, the document table on which the document is placed;
In a document reading device that includes a light source, an optical system, and a drive section, and scans and reads the document by varying the relative position of the document table, the light source, or the optical system by the operation of the drive section, the light source is turned on. Since the time until the drive section operates, that is, the preliminary lighting time, is determined by the rate of change in the light amount of the light source, the time has an appropriate time width regardless of the temperature of the light source.

[Brief explanation of the drawing]

Fig. 1 is a structural diagram of a document reading device, Fig. 2 is a diagram showing the timing of lighting and reading operations of a conventional document reading device, Fig. 3 is a diagram showing a change curve when the illumination light source is turned on, and Fig. 4 FIG. 5(A) is a structural diagram of a document reading device according to an embodiment of the present invention. (O) and (C) are diagrams showing the amount of light (current according to the light wind) of the illumination light source of the document reading device according to the embodiment of the present invention, its rate of change, and the timing of the reading operation, respectively; The figure is a partial structural diagram of a document reading device according to another embodiment of the present invention. 1 Original document, 2... Document table, 3.4... Reflection mirror,
5... Reading lens unit, 6... Reading element section, 7... Illumination light source, 8... Photoelectric conversion element, 9... Plate material. Agent Patent Attorney Aihiko Fukushi (and 2 others) Figure 1 Tortoise 21'2+ Rod 3 Gi 1 4th Simple

Claims (1)

[Claims] l. - comprising a document table on which a document is placed, a light source, an optical system, and a drive section, and scans the document by varying the relative position of the document table, light source, or optical system by the operation of the drive section; The document reading device reads the document, and includes a means for measuring a rate of change in the light amount of the light source, and measures the time from when the light source is turned on until the drive section operates after the light source is turned on and the light amount of the light source. A document reading device characterized in that the time required for a rate of change of to reach a predetermined value is set.