JPS61171271A - Character/picture reader - Google Patents

Abstract

PURPOSE:To increase the peripheral luminous energy of a fluorescent lamp by providing a plate independent of a thermoelectrode in the fluorescent lamp and a reverse flow preventing diode for controlling the direction of an electric current between the fluorescent lamp and an AC lighting device. CONSTITUTION:In the fluorescent lamp 5, plates 7a and 7b, which are electrically isolated and fixed on tube ends, and thermoelectrodes 2a and 2b are disposed, and the plates 7a and 7b are connected to terminals 5a and 5b. The fluorescent lamp 5, heating transformers 3a and 3b and the AC lighting device 4 are reversely connected each other through the reverse flow preventing diodes D6a-D6d. A positive voltage (+) is alternately impressed to the plates 7a and 7b by the AC lighting device 4 through the diodes D6a and D6b, while a negative voltage (-) is impressed to the thermoelectrodes 2a and 2b by the diodes D6c and D6d. Accordingly an electric current flows alternately between the opposite plate 7a and thermoelectrode 2b and between the plate 7b and the thermoelectrode 2a by the work of the diodes D6a-D6d, and the plates 7a and 7b act as an electrode for accelerating a thermoelectron current. Simultaneously the diodes D6c and D6d makes the electrodes 2a and 2b not flow the thermoelectron from the opposite electrodes, thereby increasing the luminous energy in the vicinity of the tube end.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a character/image reading device, and more particularly to a character/image reading device in which the effective light emitting length of a fluorescent lamp is improved.

[Background of the invention]

Conventionally, fluorescent lamps have been used as light sources in OCR (optical character reading devices, image reading devices, etc.).As shown in FIG. The reading area 13 is irradiated with light, the reflected light is reflected by the mirror 12, and the reflected light that passes through the lens 15 is imaged on the reading element image sensor 14 and photoelectrically converted.

FIG. 2 is an operational circuit diagram of a conventional fluorescent lamp.

The fluorescent lamp 1 includes transformers 3a and 3b that heat thermal electrodes 2a and 2b, and an AC lighting device 4. By applying AC power to ACIN to the transformers 3a, 3b and the lighter 4, argon discharge is first started by the kick voltage of the lighter 4, and then the main discharge is caused by mercury vapor.

In this case, since the amount of light is small at both ends of the fluorescent lamp 5,
The signal-to-noise ratio (S/N) of the characters/images written on both ends of the paper 11 is poor in reading. Therefore, as shown in FIG.
It was necessary to use the fluorescent lamp 5 of O), and it was impossible to downsize the reading device.

Note that no method has been proposed to date to increase the amount of peripheral light of a fluorescent lamp.On the other hand, there are many proposals for improving the amount of shedding, but these are mainly based on the following methods:
A shading correction plate was used to reduce the amount of light at the center. That is, as shown in FIG. 5(,), a correction reflection plate 16 is used, which has a dimension a at the center and a dimension a at both ends, which is narrower at the center. In addition, this plate 16 is arranged so as to face the fluorescent lamp 5, so that less light from the fluorescent lamp 5 is reflected at the central portion.

The amount of light on the paper 11 is corrected by applying K so that more light is reflected at both end portions. However, if possible, it is desirable to increase the amount of light at both ends of the fluorescent lamp.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve these problems and provide a small character/image reading device that can increase the amount of peripheral light of a fluorescent lamp and use a compact fluorescent lamp with small shading.

[Summary of the Invention] In order to achieve the above object, the character/image reading device of the present invention uses a fluorescent lamp as a reading light source, and includes a plate independent of the thermal electrode in the fluorescent lamp. Further, a backflow prevention diode for controlling the direction of current is provided between the fluorescent lamp and the AC lighting device, and between the plate and the thermal electrode facing each other,
The feature is that currents flow in opposite directions alternately.

[Embodiments of the invention]

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

FIGS. 1(a) and 1(b) are an operating circuit diagram of a fluorescent lamp and a perspective view of the vicinity of a thermal electrode and plate, showing an embodiment of the present invention.

5 is a fluorescent lamp, 7a, 7b are newly installed plates, 8a, 8b are terminals of plates 7a, 7b, 9a, 9
b is the terminal of the thermal electrodes 2a, 2b, 6a, 6b, 6c, 6d
is a newly installed diode.

The fluorescent lamp 5 includes thermal electrodes 2a, 2b, plates 7a, 7
It is composed of b. Plate 7a.

7b and the thermal electrodes 2a, 2b are independent electrodes that are electrically insulated within the fluorescent lamp 5, and the plates 7a, 7b are the tube inside the fluorescent lamp 5. It is fixed at the end and connected to terminals 8a and 8b. Fluorescent lamp 5, heating transformers 3a, 3b, AC lighting lI4
and are connected in opposite directions to each other via backflow prevention diodes 6a, 6b, 5e, and 6d, as shown in FIG. The plates 7a and 7b are made of an electrochemically stable metal such as nickel or nickel-plated iron.

In FIG. 1(,), the plates 7a and 7b are alternately switched on by the AC igniter 4 via the diodes 6a and 6b (
+) is applied to the heating electrode 2a at the same time.

2b is also applied to (-) via diodes 6d and 6c. Thermal electrodes 2a, 2b are connected to transformers 3a, 3 in advance.
b and the surface is constructed of well-known materials to facilitate thermionic emission. Therefore, by applying the AC power, alternating currents in opposite directions flow in the following circuits.

(1) 4 a→6a→8a→7 B-+21)-+9
b-+5 d→4b.

(2) 4 b → 6b → 8b → 7b → 2a → 9a → 6c →
4a.

That is, the plate 7a and the thermal electrode 2b facing each other
Alternatively, current alternately flows between the prenidoor b and the hot electrode 2a due to the action of the diodes 6a, 6b, 6c, and 6d. In this case, the plates 7a and 7b always operate as electrodes that accelerate the flow of thermionic electrons, and the thermal electrodes 2a and 2b that are immediately in front of them are equipped with diodes 5c for preventing backflow.
, 6d prevent thermionic electrons emitted from the opposing thermal electrodes from flowing into the electrode. Namely.

In the conventional fluorescent lamp 1, an alternating current flows between opposing thermal electrodes (space) and collides with the enclosed Hg vapor to emit ultraviolet light, which irradiates the phosphor coated on the tube wall. On the other hand, in the fluorescent lamp 5 according to the invention, the plate 7a,
Since the current flows from 7b to the opposing thermal electrodes 2b and 2a, one essential point is that the current flows to the tube end of the fluorescent lamp 5 compared to the conventional case. When a current flows through the space near the end of the tube of the fluorescent lamp 5, the amount of ultraviolet rays increases near the end of the tube, and therefore the amount of light at the end increases.

Thermal electrodes 2a and 2b are generally installed several cm inside the tube end, but this reaches a high temperature of several hundred degrees, so it is necessary to maintain the high temperature with a small amount of electric power, and the sealing of the cap part (airtightness) is required. sex)
This is because it is necessary to maintain it stably for a long period of time. Therefore, conventionally, it has been technically difficult to bring the thermal electrode into close contact with the tube end. On the other hand, in one embodiment of the present invention, the plate 7a.

7b only needs to have the function of a cold anode.

It can be easily placed at the end of the tube.

When the present invention is applied to a character/image reading device.

As shown in FIG. 4, the length A of the fluorescent lamp 5 is
The light from the lamp 5 illuminates the reading area 13 on the paper 11, the reflected light is reflected by the mirror 12, and the light from the lamp 5 is reflected by the lens 15.
An image is formed on the image sensor 4. Image sensor 1
The electrical signal from 4 is digitized by a well-known circuit 1.
It is processed as a character/image reading signal by a control circuit using a microcomputer or the like.

FIG. 3 is a comparison diagram showing the relative illuminance distribution of the present invention with the conventional one.

Another case is when the fluorescent lamp 5 of the present invention is used.

Compare on the graph the case of using the conventional one.

In the illuminance distribution graph of FIG. 3, the horizontal axis shows the longitudinal direction of the fluorescent lamp, and the vertical axis shows the relative brightness on the straight line irradiating the paper 11 from the fluorescent lamp at the irradiation distance d. . In the graph, the solid line 10a is an example using a conventional fluorescent lamp, and the broken line 10b is an example using a fluorescent lamp according to the present invention. As is clear from the graph, in the present invention,
In the example shown in FIG. 3, which increases the amount of light at the end of the fluorescent lamp, the length of the illuminance distribution that allows a shading amount (-) of 20% is extended by Ω2 fit in the present invention. In the example of FIG.
This is to expand the width W of the paper 11 that can be effectively read by the image reading device. Furthermore, while improving the ratio of the effective irradiation width to the total length Q of the fluorescent lamp 5, the amount of shading can be reduced in the case of the same irradiation width. Although not shown, if the amount of peripheral light is increased and the amount of shading is decreased as a whole, the S/
N improvements contribute, and a high-speed character/image reading device can be realized in a compact manner.

Image sensors are usually used at 30 to 50% of the saturation exposure, but if
In the case of 0%, it is unavoidable that the amount of light will drop to 70-60% at the periphery. This is because in addition to the shading of the fluorescent lamp, there is always a reduction in the amount of peripheral light based on the cos'θ side of the lens. Therefore, the periphery tends to suffer from a decrease in S/N due to insufficient light quantity, and as a result, the variation in image quality between the center and the periphery increases.

For example, the tube length of a JIS standard 15W size fluorescent lamp is 436 mm, but in order to increase the illumination efficiency as a reading light source, a fluorescent lamp with an opening of 601 to 90 inches (only this part is not coated with fluorescent material) is used. , when used at an illumination distance of around 20 mm, the shading (
The effective length that can be illuminated within -)20 to (-)30% is
It is approximately 260 mrn. This is B4 size (25
It can illuminate only 257 mm of the short side of the tube (7 mm x 364 mm), which is about 60% of the tube length. Now, if we were to illuminate the short side of an A3 size (297 mm x 420 mm) under the same conditions as above, we would have to manufacture a fluorescent lamp with the tube length extended by about 40 mm, but this is not the case.

The reading device is large, which is not a big deal.

As a light source for an A3 size reading device, even the 15W tube length of 436 mm is too long, which is one of the obstacles to realizing a compact reading device.

Therefore, simply increasing the length of the tube may cause new problems.The present invention installs a new Wt pole between the end of the tube and the heating electrode, and also changes the route through which the current flows. By controlling with an external circuit, the amount of peripheral light emitted from the fluorescent lamp is increased, and the effective illumination length is increased without changing the tube length. The expected increase in the effective lighting length according to the present invention is approximately 40 m.
It is m. Also, set the lighting length to 25cm on the short side of B4 size.
When m is fixed, it is clear that the present invention increases the amount of peripheral light and reduces the amount of shading.

〔Effect of the invention〕

As explained above, according to the present invention, the amount of peripheral light is increased using a fluorescent lamp of the same tube length, and an illumination light source with less shading as a whole can be obtained.By applying this to a character/image reading device, It is possible to realize a compact reading device with little variation in reading image quality between the periphery and the center.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the operation of a fluorescent lamp showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of the operation of a conventional fluorescent lamp, Fig. 3 is a diagram showing the illuminance distribution of the fluorescent lamp, and Fig. 4 is a diagram showing the characters. - A perspective view of an image reading device, and FIG. 5 is an explanatory diagram of a conventional correction plate for improving the amount of shading. l, 5: Fluorescent lamp, 2a, 2b: Thermal electrode, 3a, 3b
: Heat transformer, 4: AC lighting device, 6a, 6b, 5c
, 6d: diode, 7a, 7b nibrate, ga, 8
bt 9a, 9b: terminal, 11: paper, 13: reading area, 17: light shielding plate. Figure 1 (a) bl Figure 2 Figure 3 Fermentation diagram

Claims (1)

[Claims] (1) In a character/image reading device using a fluorescent lamp as a reading light source, a plate independent of the thermal electrode is installed inside the fluorescent lamp, and a plate is installed between the fluorescent lamp and the AC lighting device to control the direction of the current. What is claimed is: 1. A character/image reading device characterized in that reverse current prevention diodes are provided respectively, and currents in opposite directions are caused to alternately flow between the plates and the heating electrodes that face each other.