JPS60680Y2 - Light source device for optical reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light source device for optical reading devices such as OCR and facsimile machines, and is intended to improve the lifespan and reliability of the light source.

BACKGROUND OF THE INVENTION Conventionally, optical reading devices (hereinafter referred to as reading devices) such as OCR and facsimile machines that are constructed by integrally arranging reading elements such as diode arrays use fluorescent lamps or tungsten lamps as light sources.

However, fluorescent lamp light sources have the following drawbacks.

B. In order to cope with the demand for higher speed reading devices, it is necessary to increase the current flowing in order to increase the amount of light per unit length of the fluorescent lamp.

However, since the amount of light emitted per unit area of the phosphor cannot be increased due to the lifetime of the tube, it is necessary to increase the diameter of the tube, increase the area of the phosphor per unit length of the tube, and then increase the applied current.

However, in this case, the distance from the light source to the irradiated object is usually very close, so increasing the diameter of the tube will inevitably increase the average distance from the light emitter to the irradiated surface. The brightness does not increase as much as the applied current increases.

Normally, the amount of light emitted by fluorescent lamps decreases as the energization time passes, but the degree of this decreases is not uniform along the length of the tube.

That is, it decreases most significantly near the electrodes at both ends, and the degree of decrease decreases toward the center.

Therefore, as the length of time the tube is energized increases, the light intensity distribution in the longitudinal direction changes, so it is necessary to compensate the read signal in accordance with the change in the light intensity distribution.

C. In a reading device that moves the form horizontally when viewed from the reading device operator, the length of the end of the fluorescent lamp has a negative effect on light emission, especially the part on the front side facing the operator, which can be a hindrance to operation. It tends to be difficult to put together in terms of design.

Second, tungsten lamps generate a large amount of heat and require careful consideration for heat dissipation, and there are problems with the readable spectral range depending on the emission wavelength range.

However, conventionally, tubes made of thick glass tubes with a relatively small outer diameter (approximately 6 mm φ) and a narrow inner diameter (approximately 1 m φ) and relatively high gas pressure (2-3° art Hg) Noble gas discharge tubes are used as electroscopes.

However, this discharge tube has the characteristic that if the power source is appropriately selected, it can become a light source with a nearly uniform amount of light emitted per unit length of the tube.

Furthermore, such discharge tubes usually have a thicker tube inner diameter only at the electrode section, which is designed to keep the current per unit area of the electrode section low, but this structure also serves to prevent blackening inside the thin tube. There is.

In other words, the wall of the thick tube part of the electrode portion becomes blackened with the passage of time, but the blackening does not penetrate into the thin tube part.

The present invention focuses on the fact that the light intensity distribution does not change due to blackening in the narrow tube even after long-term use, and shapes such a discharge tube into a shape suitable for a reading device, thereby eliminating the flicker that would be a hindrance to the reading device. By lighting the lamp with alternating current at a frequency that is low enough to provide a uniform reading range and illuminating with necessary and sufficient brightness, a light source with a long life can be obtained.

The drawings show an embodiment of the present invention; 1 is a light source lamp; in FIG. 1, the thin tube part 11 is U-shaped;
, 13 are parallel on one side of the form.

1a and 1b are electrode terminals, and Figure 2 shows an example of double electrode terminals.
FIG. 3 shows an example in which the number is increased even further.

Here, 3 is a projection lens, and 4 is a reading element such as a diode array.

FIG. 4 shows details of the electrode section 12, which is a discharge electrode.

Figure 5 shows the relationship between the bent part of the lamp 1 shown in Figure 1 and the casing that holds it, and 14.15 is an L-shaped lamp holder with a cushioning material that can withstand high heat. The lamp 1 is held through the lamps 16 and 17, and the upper surface is covered with a cover plate having a slit 18 for guiding the reflected light irradiated onto the form 2 to the reading element 4 side.

In the lamp 1, it is desirable that the length of the thin tube 11 (the length from the electrode section side to the bent part [one side of the form 2]) is set to a length suitable for reading characters written on the form 2.

As described above with reference to the embodiments, in the present invention, a discharge tube with relatively high gas pressure used in a high-voltage detector tube, etc., is constructed so that the tube wall thickness is relatively thick and the relatively narrow inner diameter part surrounds a long and narrow irradiated surface. It is characterized by having a U-shaped or flattened spiral bottom shape, and having the power feeding part (electrode part) gathered on one side to form a light source device suitable for optical reading devices such as OCR and facsimile.

Therefore, a light source with a long life can be obtained, and there is no problem due to blackening, and no change in the light amount distribution occurs.

Furthermore, since the power supply section (electrode section) is gathered on one side, power supply processing can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a light source device for an optical reader which is an embodiment of the present invention, FIG. 2 is a perspective view of another embodiment, FIG. 3 is a side sectional view of still another embodiment, and FIG. The figure is a cross-sectional view of the electrode portion of the light source device, and FIG. 5 is a diagram showing the relationship between the lamp and the housing. 1... Lamp, 11... Thin tube part, 12
, 13... Electrode part.

Claims (1)

[Scope of Claim for Utility Model Registration] A discharge tube with a relatively high gas pressure and a relatively thick wall has an inner diameter at the center smaller than the inner diameter at both ends, and. An optical device characterized in that the central narrow tube part of the discharge tube is formed into a U-shape or a flattened shape so as to surround the elongated irradiated surface of the optical reading device, and a power supply part is provided on one side. Light source device for target reader.