JPS6055766A - Optical output controller - Google Patents

Abstract

PURPOSE:To keep the wall of a tube at optimum temperatures by switching an optical output setting means when an illumination light source is not used. CONSTITUTION:The optical output of a lamp 3 is detected by a sensor circuit 7 and converted into voltage VL. This voltage VL is compared with the reference voltage VREF of an error amplifier 8, and this error of comparison is amplified to obtain voltage V0. An optical control circuit 9 delivers an optical control signal P in response to the voltage V0 to an optical control/lighting device 6. Then the circuit 9 supplies a lamp current I corresponding to the signal P to the lamp 3. In such a system, the voltage V0 reduces and the signal P reduces the current I when the optical output increases and the VL is larger than the VREF. When a mode changeover switch 4 is set in a copy mode, the volume 5 is applied as the voltage VREF. While the voltage Va is applied in a waiting mode. The value of the Va is set so as to obtain an optical output that sets the temperature of a tube wall at optimum levels 30-40 deg.C.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a light output control device for an illumination light source (hereinafter referred to as a light source) used in an illumination device such as a copying machine, facsimile, or scanner. It is concerned with compensation of the rise characteristics, especially the rise characteristics.

(Technical Field) The light output of a light source, such as a fluorescent lamp, greatly depends on the temperature of the tube wall.The luminous efficiency is particularly low at low temperatures.For example, when the tube wall temperature changes from 10°C to 60°C, the light output The change in output is F170%. Therefore, when used as a light source for copying, there are serious problems such as the occurrence of copy errors. Therefore, various means have been proposed to prevent the tube wall temperature from decreasing.

One of them is a tube wall preheating heater. However, although this technique has the effect of increasing the tube wall temperature to a predetermined value or higher, it requires an increased number of configurations and poses safety problems. Further, since it is not necessary after the lamp is turned on, a control circuit is required to turn off the heater accordingly.

A continuous lamp lighting system is also used. That is, the lamp is turned on even when not in use to prevent the temperature of the tube wall from decreasing. However, when the lamp is lit, it is generally 60
℃ or higher, and in this method, the effect of preheating the lamp is not only excessive but also causes an increase in the temperature inside the machine. Moreover, continuous lighting has a negative effect on the life of the lamp. Furthermore, in the case of copying machines, glare when setting originals,
A shutter is necessary because it causes partial fatigue of the photoreceptor.

Ten thousand light output stabilizers are also known. This detects light and feeds it back to the lamp power, but in order to prevent a drop in luminous efficiency at low temperatures, it is necessary to input several times as much power as in normal conditions. Therefore, there are disadvantages in that the lighting device has a large output and the life of the lamp is shortened.

As described above, various conventional means have been proposed, but each of them has advantages and disadvantages. Among these, a method in which fluorescent lamps are turned on continuously regardless of whether they are used or not does not require a particularly complicated configuration and is a simple and effective method. However, as mentioned above, fluorescent lamps have drawbacks in terms of lifespan, glare to the user, and impression.

(Purpose) The present invention improves the shortcomings of this single prior art, and realizes a lighting device that does not have rise characteristics even at low temperatures and always lights with stable light output without adding any special components. The aim is to achieve this without causing any side effects such as shortening the lifespan of fluorescent lamps.

(Structure) In the case of a fluorescent lamp, as described above, when the tube wall temperature falls below 40°C, the luminous efficiency rapidly decreases and the light output decreases. Moreover, at temperatures above 40° C., the optical output decreases, albeit slowly. In the case of copying, the reduction in light output at low temperatures is a particularly serious problem.In order to prevent leakage, it is sufficient to maintain the tube wall temperature at about 40° C. when the lamp is to be lit. Moreover, it would be convenient to obtain a predetermined temperature by keeping the lamp itself lit, without adding a special part to the means for maintaining the temperature.

If the lamp was lit the same way when not in use as in the past, the temperature of the tube wall would not necessarily reach 40QC, but would generally reach 60 to 70°C (as explained in the conventional technology). There are various side effects. Therefore, in the present invention, when the lamp is not in use, the lamp power is adjusted so that the tube wall temperature becomes 30 to 40°C.

To do this, store the lamp power to reach that temperature in advance, and set it automatically to that power when not in use, and detect the tube wall temperature only when it is used for a lifetime. 40
The lamp power may be adjusted so that the temperature is at °C.

When not in use, the lamp is treated as a ninth heater that heats itself.

An example of a copying machine will be described below.

Three examples are shown.

First, an example of application to a dimming type lighting device is shown in FIG.

Copying machines often allow a user to adjust the light output of a lamp depending on the density of the original.

In the figure, 1 is a power supply, 2 is a dimming ballast, 3 is a lamp (fluorescent light), 4 is a mode changeover switch that allows setting voltage to be reflected on the dimming ballast 2, 4a is a copy mode terminal, and 4b is a standby This is a mode (mode when not in use) pin. The copy mode terminal 4a is connected to the exposure cylinder m body IJ needle 5, while a voltage Va is applied to the standby i mode terminal 4b.

In the normal copy mode, the exposure control volume set by the user or service personnel adjusts the light control level Vc.
is given, and a corresponding optical output is obtained.

On the other hand, in the standby mode, the mode changeover switch 4 is switched and a constant voltage Va is applied as a dimming level.

The value of Va is set in advance so that when the lamp 3 is turned on, a lamp power is applied to the lamp such that the temperature of the tube wall is such that the temperature does not exhibit rise characteristics.

Therefore, when the mode changeover switch 4 is set to the copy mode side at the same time as copying, the lamp 3 does not have any rising characteristics and instantly
Lights up with light output corresponding to R.

Generally, when lit normally, the tube wall temperature of a fluorescent lamp is 60
It can reach ~70°C. On the other hand, during standby 30~40°Cσ)
By maintaining the temperature, the rise characteristic can be prevented, so the light output and power during standby can be reduced.

In this way, the optimal temperature for fluorescent lamps is 30 ~
40°C can be obtained.

An embodiment of the optical output stabilizing device is shown in FIG. 2.

In the figure, 6 is a dimming lighting device, and a lamp current I is applied to the lamp 3.

The light output of the lamp 3 is detected by a sensor circuit 7 and converted into Vl. VL is a predetermined reference voltage V of the error amplifier 8.
It is compared with REF, the error is amplified, and 0 is obtained.

The dimming control circuit 9 gives a dimming signal P according to Vo to the output 1 to the dimming lighting device 6.

The lighting device 6 supplies lamp current according to P to the lamp 3. In this system, when the optical output increases and v becomes larger than VREF, Vo decreases, and P becomes a signal that reduces the lamp current.

Generally, P may be a pulse whose pulse width is modulated according to vo, and if Vo is low, the duty ratio of P is set to decrease. The lamp current I is supplied with a duty ratio of P, and therefore the lamp average current also decreases according to P. Therefore, the light output and vL also decrease.

On the other hand, when the optical output decreases and VL decreases, the movement is opposite to the above and the optical output is corrected in the direction of increasing it.

As a result, the entire system works to make V L ''= V REF and the optical output is stabilized.If you change the setting of V REF, the optical output will follow accordingly and be stably maintained at that level. .

When the mode changeover switch 4 is in the copy mode, the exposure adjustment volume 5 is employed as VRgF, and the desired light output is maintained constant. On the other hand, when the standby mode is entered, another value V a fs is adopted as VREF. This Va value is set in advance so as to obtain a light output that makes the tube wall temperature 30 to 40°C (the optimum temperature for the lamp).

Therefore, during standby, the tube wall temperature can be maintained at an optimum level by a simple operation of switching from VREF k Vl< to ■avc to 0. As a result, when the arrow returns to copy mode, the luminous efficiency will not decrease even in low temperature environments.
That is, the optical output corresponding to the desired V and ζ can be obtained.

A method for more precise temperature control in this embodiment will be described next.

Pipe wall temperature (hereinafter referred to as 'rs) 2il-30~40°C
The exact value of Va to be maintained varies depending on the ambient temperature (hereinafter referred to as T).

When Ta is as low as 5 to 10°C, vF has a relatively large force value, and when Ta is 30°C or higher, va
may be small, or may be O (lamp not lit during standby). A circuit for reflecting this relationship is shown in FIG.

Lamp ambient temperature Ta? Detected by the thermistor 10. T
When a is low, va is high and potency, and lamp power is also increased to obtain a predetermined Ts. Conversely, when Ta increases, Va decreases, lamp power also decreases, and the same predetermined Ts is obtained. The relationship between the lamp power (light output) and Ifa required to obtain a predetermined Ts (30 to 40°C) is determined in advance, and the thermistor 1 having a temperature f number that matches the relationship is determined in advance.
If you select 0, it will be T.

Regardless of the temperature, Ts during standby is approximately the same temperature.

On the other hand, as an optical output stabilizing device, instead of using an analog configuration as shown in Figure 2, an error amplification and dimming control circuit 'rCPU'i is used.
It can also be configured digitally using i-.

In that case, the relationship between the required lamp power and Ta can be created as a table on the program, and there is no need to match the temperature coefficient of the thermistor as described above. Alternatively, the tube wall temperature Ts may be detected. That is, in the standby mode, the lamp is operated as a heater. It is clear that such temperature control can also be applied to FIG.

(Effects) The present invention is as described above, and according to the present invention,
The tube wall temperature can be maintained at an optimum level for light sources with severe temperature characteristics such as light lamps, and the rise in light output can be kept to a minimum. Furthermore, in combination with a light output stabilizing device, the light output can be consistently stabilized in all environments, and furthermore, it is possible to prevent the device from becoming larger.

Especially for compensation at low temperatures, will the structure become more complicated and the cost increase without using another component such as a heater? It can be prevented. In addition, side effects such as effects on lamp life can be minimized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a light output control device according to a first embodiment, FIG. 2 is a circuit diagram according to a second embodiment, and FIG. 3 is a circuit diagram showing a temperature detection section thereof. 3...Light source for illumination, 4...Light output setting means.

Claims (1)

[Claims] In a light output device in which power to an illumination light source is set by a light output setting means, when the illumination light source is not in use, the light output is adjusted so as to suppress the power according to the temperature of the illumination light source or its surrounding temperature. A light output control device characterized in that an output setting means is switched.