JPS6330826B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image input device used for reading a document such as a facsimile machine, and more particularly to heater control of a document illumination light source.

There is a conventional image input device as shown in FIG. The figure shows a photoelectric conversion unit of a facsimile transmitter, in which 1 is a document, 2 is a roller for conveying the document 1, 3 is a fluorescent lamp for illuminating the scanning surface of the document 1, 4 is a lens, Reference numeral 5 denotes a one-dimensional solid-state imaging device that photoelectrically converts the image formed on one side of the original through the lens 4, 6 a lighting power source for lighting the fluorescent lamp 3, and 7 a scanning device for the one-dimensional solid-state imaging device 5. This is a control circuit that controls lighting of the lighting power source 6.

Next, the operation will be explained. The document image on one side of the original is imaged by the lens 4 onto the light-receiving surface of the one-dimensional solid-state image sensor 5, and photoelectrically converted by the one-dimensional solid-state image sensor 5. The document 1 is conveyed by the rollers 2, but the conveyance speed is not constant and always changes depending on the amount of information on the surface of the document. This is because the facsimile apparatus transmits signals subjected to band compression processing, so the transmission time per scanning line varies depending on the amount of information. The control circuit 7 is
Each time the original 1 is fed by one scanning line interval, the one-dimensional solid-state image sensor 5 is scanned, and at the same time, the lighting power source is controlled to turn on the fluorescent lamp 3 for a certain period of time.

Figure 2 shows the conveyance a of the original 1 and the lighting c of the fluorescent lamp 3.
and scanning timing b of the one-dimensional solid-state image sensor 5
shows the relationship between In the figure, when the original 1 passes through each reading scanning position, the fluorescent lamp 3 is turned on for a certain period _t1 to illuminate the original, and the one-dimensional solid-state image sensor 5 is scanned. The scanning period t ₂ of the one-dimensional solid-state image sensor 5 and the lighting period t ₁ of the fluorescent lamp 3
are the time it takes to transport document 1 per scanning line.
T ₁ , T ₂ , T ₃ ...... are selected to be equal to or slightly smaller than the minimum value.

Next, the reason why the fluorescent lamp 3 is turned on intermittently will be explained. The photoelectric conversion operation of the one-dimensional solid-state image sensor 5 is as follows:
As is well known, it operates in an accumulation mode, and the photoelectric conversion signal output level is proportional to the exposure amount, that is, the accumulation time, and the brightness of the illumination light. However, in the example shown in FIG. 2, the storage time of the solid-state image sensor 5 is the time to transport the original
t ₁ , t ₂ , t _{3 .} . . are equal, and the accumulation time changes for each scanning line. Therefore, if the document 1 is kept lit all the time, the photoelectric conversion signal level will not be constant. Therefore, by illuminating the fluorescent lamp 3 for a certain period _t2 , the amount of exposure is made constant.

By the way, when the fluorescent lamp 3 is turned on intermittently according to the transport speed of the document 1, the current value flowing through the fluorescent lamp 3 changes depending on the length of the off period, so the spot temperature of the heater of the fluorescent lamp 3 remains constant. It won't happen. Generally, there is an optimal value for the spot temperature of the heater of the fluorescent lamp 3, and if the spot temperature is too high or too low, the life of the fluorescent lamp 3 will be significantly reduced, so conventional lighting methods are not recommended. There was a drawback that the life of the fluorescent lamp 3 was significantly reduced.

This invention was made for the purpose of preventing the lifespan of the illumination light source that is lit intermittently at a variable cycle as explained above from decreasing. An object of the present invention is to provide an image input device that can prevent a reduction in the life of an illumination light source by constantly keeping the heater temperature constant by supplying a heater heating current.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, 8 is a heater heating circuit added in the present invention, 9 is an inverter, 10 is a switch, and 11 is a heater transformer. In addition,
Reference numerals other than 8 to 11 are the same as those in FIG. 1, or indicate corresponding parts.

Next, the operation will be explained. The inverter 9 generates a high frequency voltage and applies the voltage to the heater of the fluorescent lamp 3 via the heater transformer 11 to heat it. A switch 10 is disposed between the inverter 9 and the heater transformer 11, and the switch is closed only during the period when the fluorescent lamp is turned off as shown in FIG. Opening/closing control of the switch 10 is performed by a control circuit 7. The magnitude of the voltage applied to this heater is selected so that the spot temperature of the heater always remains close to the optimum value when the lighting cycle of the fluorescent lamp 3 changes.

In the above embodiment, an example was shown in which the heater is heated only when the fluorescent lamp 3 is turned off. However, if the lighting current of the fluorescent lamp 3 is small, it is better to apply a low heating voltage to the heater even while the fluorescent lamp 3 is turned on. good. That is, by applying a low voltage to the heater when the fluorescent lamp 3 is on and applying a high voltage when it is off, the spot temperature of the heater is always set to the optimum value.

Further, in the above embodiment, an example was explained in which the heater of the fluorescent lamp 3 is heated with high frequency by the inverter 9, but the heater heating power source may be a commercial frequency power source or a DC power source, and the heater heating circuit 8 may be modified in various ways. It can be realized by

Further, in the above embodiment, an example was explained in which the fluorescent lamp 3 is used as the document illumination light source, but the same effect can be obtained even when a discharge lamp (such as a Ne discharge lamp) filled with a strange gas is used.

Furthermore, in the above embodiment, an example was explained in which the document 1 is driven by the roller 2 and photoelectrically converted by the one-dimensional solid-state image sensor 5, but a two-dimensional solid-state image sensor is used as the photoelectric converter. Exactly the same effect can be obtained when a discharge lamp such as a fluorescent lamp is intermittently turned on at a variable period to illuminate the entire document or other object and then photoelectrically converts it all at once.

As described above, according to the present invention, when the document illumination light source is intermittently illuminated at a variable period, by changing the heater heating voltage when the light is on and when the light is off, or by applying the heater heating voltage only when the light is off, Since the spot temperature of the heater is always set to a value close to the optimum value, there is an effect of preventing a decrease in the life of the document illumination light source.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional image input device.
2a, b, and c are diagrams each showing the operation timing of each part of the image input device of FIG. 1, and FIG. 3 is a diagram showing the configuration of the image input device according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Original, 2... Roller, 3... Fluorescent lamp for illuminating the original, 4... Lens, 5... One-dimensional solid-state image sensor, 6... Fluorescent lamp lighting power supply, 7... Control circuit, 8
...Heater heating circuit, 9...Inverter, 10...
...Switch, 11... Heater transformer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A light source that intermittently illuminates a subject at variable intervals;
A lens that forms an image of the subject, a solid-state image sensor that is placed on the lens imaging surface and photoelectrically converts the subject image, and a heater heater that applies a predetermined voltage to the heater of the upper light source during the period when the light source is turned off. An image input device characterized by comprising a circuit. 2. The image input device according to claim 1, wherein the light source is a fluorescent lamp or a discharge lamp sealed with a strange gas.