JPS6313298A - Lighting apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION -1 The present invention generally relates to an illumination device that can be used for various purposes, and in particular to a document reading device, that is, an exposure means, that illuminates a document and reads the document image in office equipment, etc. The present invention relates to a lighting device with a variable amount of light that can be suitably used for applications such as the following. Hereinafter, in this specification, the present invention will be explained mainly in relation to a document reading device for office equipment, but the present invention relates to! ! ! Ming? However, its use is not limited to this device.

′ It is a long length (
As elongated light sources, elongated fluorescent lamps, halogen lamps, and the like are frequently used.

Fluorescent lamps have a small amount of light (1) and are usually used as lighting devices for low-speed office equipment.In order to use fluorescent lamps as lighting devices for high-speed office equipment, which has recently been in demand, the power supply has been increased and the brightness ( When increasing the amount of light emitted, the internal filament installed inside the fluorescent tube dissolves,
There is also a limit to the increase in power supply, and in reality it is not suitable for use as a lighting system for high-speed office equipment.

On the other hand, halogen lamps emit a large amount of light.

Although it is used for high-speed office work 411 review, it generates more light with wavelengths in the infrared region than the visible light region required for document reading by office equipment, and it not only has poor luminous efficiency but also It generates a large amount of heat, and in order to reduce this heat generation effect, a cooling device, especially a large cooling device, is required, and it cannot be said to be a desirable lighting device in today's world where office equipment is desired to be smaller and cheaper. .

The applicant solves the drawbacks of the above-mentioned conventional fluorescent lamps and halogen lamps. We have proposed an elongated illumination device suitable not only for general illumination but also particularly as a document reading device for office equipment (Japanese Patent Application No. 1982-78782).The illumination device 100 is as shown in FIG. , a discharge tube 1 that emits light by a high-frequency electromagnetic field, an electrode 2 disposed on the outer wall of the discharge tube, and a high-frequency applying means 3 that applies a high frequency to the electrode.

To explain further, in FIG. 2, the discharge tube 1 is formed by coating a phosphor inside a long and narrow glass tube usually made of soda glass or pyrex glass. A Ml initiator and an inert gas such as Ar are included. Further, at or near both ends of the discharge tube 1, electrodes 2 made of a conductive material, such as copper or stainless steel, which are less susceptible to aging, are arranged. Although the electrode can be provided slightly apart from the outer wall of the discharge tube, it is usually preferable to provide the electrode in close contact with the outer wall of the discharge tube because the power loss applied to the discharge tube is small.

A high frequency voltage is applied to the electrode 2 by a high frequency applying means 3. The high frequency application means 3 may have any configuration, but 1
For example, as illustrated in FIG. 3, a Takaoka wave oscillation circuit 4 that oscillates a high frequency voltage, an input power source 5 for the high frequency oscillation circuit 4, and a high frequency voltage from the high frequency oscillation circuit 5 to a desired voltage. It has an amplification circuit 286 for amplification, and an LC coupler 7 for matching the high frequency voltage from the amplification circuit 6 with the impedance of the discharge tube l.

When a high frequency voltage is applied to the electrode 2 from the high frequency applying means 3 having such a structure, the mercury gas in the discharge tube becomes excited by the high frequency electromagnetic field.

Generates ultraviolet light. The ultraviolet rays act on the phosphor coated on the inner wall of the discharge tube to generate light in the visible light range.

FIG. 4 shows another embodiment of the illumination device, which is different from the illumination device of FIG. 2 in the structure of the electrodes. In other words, the electrode 2a of this example is wound in a coil shape multiple times along the longitudinal direction of the elongated discharge tube l, which has the same configuration as the discharge tube l explained in connection with FIG. The difference is that the high frequency applying means 3 is provided on the outer wall of the discharge tube 1, and the high frequency applying means 3 has the same structure as described in connection with FIG. The illumination device shown in FIG. 4 has the advantage of being able to apply a larger amount of power to the electrode 2a and obtain a larger amount of light than the illumination device shown in FIG. This is preferable for applications where a large amount of light is required, such as.

In the lighting device shown in FIGS. 2 to 4 above, the electrode 2.2a is provided outside the discharge tube, and unlike conventional fluorescent lamps and halogen lamps, the lighting device does not have a filament inside the discharge tube. First, the degree of deterioration of the electrodes is extremely small, and the electrodes can be replaced once they have deteriorated, making it possible to always obtain a desired level of brightness (light amount). Furthermore, such a lighting device can apply a large amount of power to the electrodes, making it possible to increase the amount of light.

Such a lighting device has the advantage that since the discharge tube can be formed into a long length, it is extremely effective, especially when used as a document reading device, since uneven illuminance does not occur in the direction of the document.

However, according to research conducted by the present inventors, in conventional devices of this type, after high-frequency power is supplied from the high-frequency application means 3 to the discharge tube 1 to start discharge, the amount of light decreases over time. I found that there is a tendency to In other words, as shown in FIG. 5, the amount of light emitted from the discharge tube 1 rises all at once at the start of discharge, decreases for several minutes (t'-t'') after the start of discharge, and after a certain period of time (t ″) maintained at a stable value. Such a phenomenon is inconvenient for a document reading device that illuminates a document and reads the document image in office equipment, that is, an illumination device used as an exposure means or the like.

The object of the present invention is to provide a lighting device that can instantly obtain stable light by reducing fluctuations in the amount of light emitted due to a decrease in the amount of light after the start of discharge. The goal is to provide the following.

The above objective for occupying uI is achieved with the lighting device according to the present invention. To summarize, the present invention includes a discharge tube that emits light by a high-frequency electromagnetic field, an electrode disposed outside the discharge tube, and a high-frequency application means that applies a high-frequency electromagnetic field to the discharge tube via the electrode. The lighting device includes a control means for sending a duty signal to the high frequency application means and controlling an output of the high frequency application means, and the control means transmits the duty signal from the control means after the start of tB11. The lighting device is characterized in that the output of the high frequency applying means is controlled according to the time, and the amount of light emitted after the start of discharge is maintained constant.

Support 1j Next, the lighting device H according to the present invention will be explained in more detail.

FIG. 1 is a block diagram schematically showing the configuration of an embodiment of a lighting device 100A according to the present invention. In this embodiment, the discharge tube l is the same as that described in connection with FIGS. 2 and 4. In this embodiment, the discharge tube 1 has an electrode 2a having the structure shown in FIG. To give a more specific example, the discharge tube l has a diameter of 5 to 30 mm and a length of 30 mm.
0 mm, and several To
r r.

Furthermore, when Hg is injected as a discharge initiating material into a discharge tube having an electrode 2a having the structure shown in FIG.
Hz -102MHz, ? lt pressure is 2 at Vpp
00V or more, duty ratio of high frequency pulse is 5 to 90%
A high frequency voltage is applied.

Good illumination is achieved.

According to the present invention, the high frequency applying means 3 can have any configuration; for example, as illustrated in FIG. and a high-frequency amplification unit 6 that amplifies the high-frequency voltage from the high-frequency oscillation unit 5 to a desired voltage.
and has.

Furthermore, according to the present invention, the high frequency applying means 3 is configured to vary the duty ratio of the output high frequency power from the high frequency applying means 3 applied to the electrode 2 in accordance with a signal from the control means 200, which will be described in detail later. A switch element 25 is provided. The switch element 25 is arranged between the power supply section 5 and the high frequency oscillation section 4 in this embodiment. The switch element 25 does not need to be disposed between the power supply unit 5 and the high-frequency oscillation unit 4, and can be provided at any position within the high-frequency applying means 3 as long as the high-frequency output can be modulated.

The illumination device 21100A according to the present invention further includes a light amount detection means 30 for detecting the amount of light emitted from the discharge tube l. and a control means 200 that acts on the output switch element 25 of the high frequency applying means 3 to control the output of the high frequency applying means 3, that is, the duty ratio of high frequency power applied to the electrode 2a according to the light amount detecting means 30. do.

As the light amount detection means 30, for example, a photocell or the like which emits an electric signal according to the amount of light from the discharge tube 1 is suitable, and it is arranged at an arbitrary position to detect the amount of light from the discharge tube 1. The control means 200 also includes an A/D converter 21 for converting an analog electrical signal from the light amount detection means 30 into a digital signal, a ROM 22 in which appropriate light amount value data for the original image is stored in advance, and the A/D converter. It has an arithmetic unit 23 that compares the digital signal from 21 with appropriate light amount value data from ROM 22 and generates a difference value signal, and an output unit 24 thereof.

Further, in a preferred embodiment of the present invention, the above-mentioned
Heating means for heating the discharge tube by contacting the tube 1, ie, a heater 26, and a heater control section 27 are provided. This heater 26 is used to facilitate the start-up of discharge in this type of lighting device.

As mentioned above, the discharge tube l used in the lighting device of the present invention is filled with Hg, Ar gas, etc., and when the tube is heated to a certain level, it contains more Hg than when it is cold. According to the research of the present inventors, uniform light emission occurs over the entire length of the discharge tube when the tube wall temperature of the discharge tube is low. However, by increasing the heating temperature of the discharge tube l by the heater 26 to 60° C. or higher, uniform light emission was generated over the entire length of the tube. It has been found that it is possible to make stand-up easier at the same time.

When a high frequency voltage is applied to the electrode 2 from the high frequency applying means 3 configured as described above, the mercury gas in the discharge tube is excited by the high frequency electromagnetic field and generates ultraviolet light (253.7 nm). The ultraviolet rays act on the phosphor coated on the inner wall of the discharge tube to generate light in the visible light range.

Next, the operation of the lighting device of the present invention configured as described above will be explained.

According to the present invention, basically, the duty signal outputted from the control means 200 to the switch element 25 of the high-frequency applying means 3 is varied according to the time after the start of discharge, and the high-frequency Application means 3
The high-frequency power from the source varies depending on the time, and the amount of light emitted after the start of discharge is maintained constant.

To explain in more detail, FIG. 6 shows an example of the relationship between the passage of time after the start of discharge and the duty ratio α of the signal outputted from the output section 23 in the control means and controlling the switch element 25 according to this embodiment. and time 0 to t1. In other words, from the start of discharge until time t1, the high-frequency output from the high-frequency applying means is 100% of the previous output, and at time 1+, it is switched to the duty ratio α, and from t1 to tz, it is output at the duty ratio α1. , switch to α2 at time tz and switch to α2 at time tz-
Until t3, a mode is shown in which output is performed with duty α2.

FIG. 7 shows the relationship between light and time when the above control is performed. In FIG. 7, time 0 to t1
Until then, the output is at a duty ratio of 100%, so the discharge rises vigorously (■), and when the light amount detection means 30 detects that it has fully risen (time 1+), the output from the output section 23 of the control means 200 is immediately activated. Switch the pulse duty ratio to α1%. As a result, the light amount drops suddenly (■), but gradually decreases to the appropriate light amount value Lo.
When the duty ratio decreases to α2 (α1 × α
If you raise it to 2), the light intensity will rise once and then gradually decrease (
(2) By repeating this operation, the light amount gradually approaches the appropriate stable light amount value, and at time t'' the light amount shows a stable value.

FIG. 8 shows the above operation in a sequence flow, and shows the illumination according to the present invention! The operation of the lt position will be explained in more detail.

When the power is turned on to start operation (step 1),
In order to achieve discharge ramp-up at the start of discharge, high-frequency power is output from the high-frequency applying means 3 at a duty ratio of 100% (step 2), and the amount of light emitted from the discharge tube 1 is detected by the light amount detecting means 30 ( In step 3), the arithmetic unit 23 compares the appropriate stable light amount value Lo stored in advance in the ROM 22, and in step 4), if the light amount value has not reached Lo, the light amount value is measured again, and the operation is continued until Lo is reached. The rise of the discharge is detected by the LO, and when the light intensity reaches close to the LO, it is assumed that the discharge rise at the start of the discharge has been achieved, and the duty ratio data α- is fetched from the ROM 22 in the control means 200, and the duty ratio data αI is set as the duty ratio data α-. The ratio signal is output from the output section 24 to the high frequency application means 3 to control the switch element 25 (step 5).

Next, a timer is started (step 6), and the set time of this timer is set to the time (t5at) for determining whether the amount of light has stabilized. Subsequently, the light amount is taken in from the light amount detection means 30 (step 7), and the light amount after changing the duty ratio is again determined.

Check whether the value has decreased (Step 8) and see if it is at an appropriate value.

If the duty ratio has decreased to the appropriate value L after changing the duty ratio.
The time it takes for the time to drop to o is the timer setting time tsat
Compare whether the timer is exceeded (step 9), and if it is not, clear the timer and return to step 5 (
Step 5) In this way, the process returns from step 9 to step 5, and this cycle is repeated until a stable light amount value is shown.

When it is determined in step 9 that a stable light amount value is shown, it is determined as END (end), and this sequence is terminated.

In the above description, the light amount is measured by the light amount detection means 30,
The light amount is fed back to the control means 200 and compared with the appropriate light amount value each time to change the duty ratio. However, according to another embodiment of the present invention, as shown in FIG. It is also possible to omit the feedback system by configuring to send out a constant duty signal after a certain period of time has elapsed, and by predetermining the time and duty ratio.

The operation mode of the lighting device according to the present invention by the control method according to FIG. 1O is shown in a flowchart.

In FIG. 10, the output of the high frequency application means at the time of discharge start-up is performed at a duty ratio of 100%, and the discharge is started at once (step 13).The duty ratio for the subsequent time elapsed is determined in advance by experiment and stored in the ROM 22. Data is sequentially extracted as a pulse and sent to the switch element 25 in the high frequency application means. For example, time 1.
．． is set to α 5%, tz is set to α2%, etc., and the light quantity is finally stabilized at an output with a duty ratio of 100%.

By controlling the output at an appropriate duty ratio at an appropriate time based on experiments in advance in this way, the light amount detection means 30 becomes unnecessary.

11 vertical difference] As described above, the lighting device according to the present invention is provided at a stage before the high frequency amplifying section 6 in the high frequency pressurizing means.

In particular, the amount of light can be controlled by a simple configuration in which a switch element 25 is provided between the power supply section 5 and the high frequency oscillation section 4,
In particular, it has the advantage that fluctuations in the amount of light emitted after the start of discharge can be uniformly controlled to a stable amount of light emitted.

Further, the lighting device according to the present invention heats the discharge tube at the time of starting discharge by providing a heater in the discharge tube, and furthermore, by setting the duty ratio at the time of starting discharge to 100%, it is possible to ensure the start-up of discharge. It has become possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of a lighting device according to the present invention. FIG. 2 is a schematic configuration diagram of another embodiment of a lighting device to which the present invention can be applied. FIG. 3 is a block diagram of an embodiment of high frequency application means of a lighting device to which the present invention can be applied. FIG. 4 is a schematic diagram of another embodiment of a lighting device to which the present invention can be applied. FIG. 5 is a graph showing temporal changes in the amount of light of a conventional lighting device. FIG. 6 is a graph showing the relationship between the duty ratio of pulses sent from the output section of the control means used in the lighting device according to the present invention and time. FIG. 7 is a graph showing the relationship between the amount of light emitted by the lighting device according to the present invention and time. FIG. 8 is a sequence flowchart showing the operating mode of the lighting device according to the present invention. FIG. 9 is a graph showing the relationship between the amount of light emitted and time when the illumination device according to the present invention is operated in another manner. FIG. 10 is a sequence flowchart showing another operating mode of the lighting device according to the present invention. l: discharge tube 2.2a: fi pole 3: high frequency application means 4: high frequency oscillation section 5: power supply section 6: high frequency amplification section 25: switch element 30: light amount detection means 200: control element Fig. 1 Fig. 2 Fig. 3 Figure 4 Figure 10 Figure 9

Claims (1)

[Scope of Claims] 1) A discharge tube that emits light by a high-frequency electromagnetic field, an electrode disposed outside the discharge tube, and a high-frequency application means that applies a high-frequency electromagnetic field to the discharge tube via the electrode. The lighting device includes a control means for sending a duty signal to the high frequency application means and controlling an output of the high frequency application means, and the control means transmits the duty signal from the control means to the high frequency application means after the discharge starts. An illumination device characterized in that the output of the high frequency applying means is controlled according to the time to maintain a constant amount of light emitted after discharge starts. 2) A patent claim in which the high frequency application means comprises a power supply section, a high frequency oscillation section, a high frequency amplification section, and a switch element disposed between the power supply section and the high frequency oscillation section and receiving a duty signal from the control means. The lighting device according to item 1. 3) The lighting device according to claim 1 or 2, wherein the discharge tube is provided with a heating means. 4) The control means sends out a 100% duty signal at the start of discharge, and sends out a duty signal of 100% or less after detecting a rise in the amount of light emitted after the start of discharge. The lighting device described in any of the paragraphs.