JPH0587957B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a system for copying an original image to be reproduced via an optical system such as photolithography, in which the light intensity is used to stabilize the light intensity of a fluorescent lamp illuminating the original image to be reproduced. The present invention relates to a stabilizing device, and particularly to a light amount stabilizing device that stabilizes the amount of light by controlling the coldest point. (Prior art and its problems) Fluorescent lamps, which are commonly used as illumination light sources, have a spectral distribution that is almost equal to the luminous efficiency, and have a low calorific value. It has high utility value as a cold light source with little irradiation. In particular, in image reading devices that use semiconductor optical sensors such as CCDs, which have become popular in recent years, light sources with spectral characteristics that include a large amount of infrared light, such as halogen lamps,
It is considered desirable to be able to apply fluorescent lighting to reduce the quality of the reproduced image. The factors that determine the amount of light from such fluorescent lamps include mercury vapor pressure and tube current in the fluorescent lamp.
Among these, the mercury vapor pressure depends on the temperature, so the luminous efficiency is also determined by the temperature. Furthermore, the temperature at the lowest point (hereinafter referred to as the "coldest point") of the tube wall temperature of a fluorescent lamp determines the mercury vapor pressure.
Mercury vapor pressure determines luminous efficiency. Therefore, the luminous efficiency can be controlled by providing the coldest point somewhere on the wall of the fluorescent lamp tube and controlling its temperature. Therefore, techniques have been proposed to keep the position and temperature of the coldest point constant. For example, in Japanese Unexamined Patent Publication No. 62-8134 (hereinafter referred to as "Publication 1"), the coldest point of a fluorescent lamp is artificially reduced by bringing a heat dissipating member such as aluminum into contact with or close to a part of the tube wall of the fluorescent lamp. The temperature at the coldest point is controlled by detecting the pipe wall temperature at that point using a temperature sensor, heating it with a heater when the temperature drops, and operating a cooling fan to radiate heat when the temperature rises. However, in the above-mentioned publication 1, since the heat dissipating member having high thermal conductivity such as aluminum is brought into contact with or in close proximity to a part of the tube wall of the fluorescent lamp, the following problem occurs. In other words, when the heat dissipation member is in contact with the tube wall of a fluorescent lamp, if the temperature around the heat dissipation member changes due to the operation of a cooling fan, for example,
The temperature of the heat dissipating member, which has a high thermal conductivity, also fluctuates easily, causing a sudden change in the temperature of the coldest spot on the tube wall of the fluorescent lamp. Generally, the time required to read an original image using a copy machine or facsimile machine is the same as the maximum size.
Even for an original picture of A3 size, the exposure time is usually about 1 second, so the change in light amount corresponding to the temperature change is negligible and poses no practical problem. However, in the field of photolithography, which scans the original image line-by-line and reads the image density information at high density, the time required to read the original image is usually longer than that of a copier, etc., and the temperature changes The corresponding change in light amount cannot be ignored. On the other hand, when the heat dissipation member is placed close to the tube wall of the fluorescent lamp, the thermal conductivity of the air layer interposed between the fluorescent light tube wall and the heat dissipation member is low, so the heat dissipation member will not be affected by changes in the ambient temperature. This suppresses sudden changes in the coldest point on the wall of the fluorescent tube, but the temperature at the coldest point on the wall of the fluorescent tube becomes unstable because the thermal conductivity becomes unstable due to convection phenomena in the air layer. There's a problem. In addition to the above-mentioned Publication 1, for example,
As shown in Publication No. 129737 (hereinafter referred to as "Publication 2"), a technique has also been developed in which the position and temperature of the coldest spot are controlled to be constant using a Peltier element. However, although the Peltier element is ON/OFF controlled by a thermistor to keep the temperature of the coldest point constant, the temperature of the coldest point changes according to the ON/OFF control. Therefore, the amount of light may become unstable. When the Peltier element changes from heat generation to cooling and from cooling to heat generation, the temperature at the coldest point similarly changes, so the amount of light may become unstable. Furthermore, in order to keep the Peltier element cooled, it is necessary to radiate heat from one side of the element. Therefore, a fan for heat dissipation is required, which poses a problem in that the device becomes expensive. (Objective of the Invention) Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, to prevent sudden changes in the temperature of the coldest spot due to fluctuations in the ambient temperature of fluorescent lamps, and to reduce the time required for scanning an original image. It is an object of the present invention to provide an inexpensive light amount stabilizing device for a fluorescent lamp that can keep the light amount of the fluorescent lamp stable. (Means for Achieving the Object) In order to achieve the above object, according to the first invention, the surface temperature of the tube wall of the fluorescent lamp is detected and the temperature is set at a predetermined temperature higher than the coldest point temperature of the fluorescent lamp. The tube wall of the fluorescent lamp includes a heating control means for controlling heating of a predetermined portion of the fluorescent lamp tube wall, and a heat storage layer made of at least a material with low thermal conductivity, and the tube wall of the fluorescent lamp is provided in a region other than the area heated by the heating control means. and a heat conductive buffer member that is brought into contact with the area of the heat conductive buffer member and has the contact point as the coldest point. According to a second invention, in the original image scanning device using a fluorescent lamp as a light source for illuminating the original image, the surface temperature of the tube wall of the fluorescent lamp is detected and a predetermined temperature higher than the coldest point temperature of the fluorescent lamp is set. and a heat storage layer made of at least a material with low thermal conductivity, the region of the tube wall of the fluorescent lamp heated by the heating control means. a heat conduction buffer member that is in contact with an area other than the above and whose contact point is the coldest point, a light amount detection means for detecting the amount of light of the fluorescent lamp, and a tube that applies a detection signal from the light amount detection means to the fluorescent lamp. and tube current control means for controlling the current. (Embodiment) FIG. 9 is a schematic diagram showing an example of an original image scanning device to which the present invention is applied. In the figure, a white reference plate 15 and an original image to be copied 16 are mounted on an original stand (not shown) and are transported in the direction of an arrow 17 by a suitable driving means. The light from the fluorescent lamp 1 first passes through the white reference plate 15.
Then, the original image to be copied 16 is irradiated, and the reflected light is changed direction by a mirror 18 and projected onto a photoelectric element such as a CCD line sensor 20 through a lens 19 to form an image, and from the CCD line sensor 20 the original image to be copied is reflected. 16 image signals are output. The present invention is a means for stabilizing the light amount of the fluorescent lamp 1 in such a scanning device or the like. FIG. 1 is a diagram showing an embodiment of the light amount stabilizing device for a fluorescent lamp according to the present invention, FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 1, and FIG. FIG. 2 is a perspective view of the vicinity of one end of the fluorescent lamp shown in FIG. Here, two fluorescent lamps 1 are arranged in parallel and housed in an aluminum body case 2 having a U-shaped cross section, and are fixed by holders 3 provided at both ends of the body case 2. . In addition, except for the part where the light of the fluorescent lamp 1 is taken out, the heater 4 is provided in contact with the tube wall at the approximate center of the fluorescent lamp 1. A heat conductive buffer member 5 constituted by the heat storage layer 5b is provided in contact with a part of the tube wall at one end portion. Here, one surface of the heat transfer layer 5a of the heat transfer buffer member 5 is in contact with the tube wall of the fluorescent lamp 1,
The heat storage layer 5b is superposed and connected to the other side surface of the heat transfer layer 5a. And heat transfer layer 5
Silicone grease (not shown) is interposed on the contact surfaces between the fluorescent lamp 1 and the fluorescent lamp 1 and the contact surfaces between the heat transfer layer 5a and the heat storage layer 5b to improve thermal conductivity. A temperature sensor (not shown) such as a thermistor is provided on the surface of the heater 4, and the drive of the heater 4 is controlled by a temperature control means (not shown) according to the detected value of this temperature sensor. The fluorescent lamp tube wall that 4 is in contact with is heated to a predetermined temperature higher than the coldest point temperature, and as a result, the temperature of the fluorescent lamp tube wall that the heat conduction buffer member 5 is in contact with reaches the predetermined coldest point temperature. It is configured to be maintained. FIG. 4 is a block diagram of the original image scanning device using the fluorescent lamp shown in FIG. In the figure, light from a fluorescent lamp 1 is received by a light sensor 6 for monitoring the amount of light, and the output from the light sensor 6 is sent to an amplifier 7.
It is configured to be input to the light amount feedback unit 8 via the light amount feedback unit 8. The output side of the light intensity feedback unit 8 is connected to the "a" contact side of a switch 10 whose opening/closing is controlled by a switch driving device 9. Here, the switch driving device 9 is configured to be controlled by a host computer 11. The output side of the light intensity feedback unit 8 is connected to the "b" of the switch 10 via an A/D converter 12 and a D/A converter 13 controlled by a host computer 11.
Also connected to the contact side. That is, switch 10
When the switch 10 is switched to the "a" contact side, the output from the light intensity feedback unit 8 is given directly to the fluorescent lamp inverter 14, and when the switch 10 is switched to the "b" contact side, , the output from the light intensity feedback unit 8 is input to a fluorescent lamp inverter 14 via an A/D converter 12 and a D/A converter 13.
Here, this light amount feedback unit 8 is
The fluorescent lamp inverter 14 is controlled according to the signal level from the optical sensor 6, and the tube current flowing through the fluorescent lamp 1 is adjusted so that the output level of the optical sensor 6 is always constant. Next, the operation of the fourth illustrated device will be explained step by step. A First, turn on the power, start heater 4,
Wait for the required time (about several minutes) until the temperature of the fluorescent lamp 1 reaches an equilibrium state. This step A is usually performed at the beginning of the day. The switch 10 is switched to the "a" contact side by the B switch drive device 9, and the fluorescent lamp is turned on.
At this time, the reference density image and the original image to be copied are attached to the surface to be scanned, and while the reference density image is being scanned, the amount of light incident on the optical sensor 6 is set to be a constant value for calibration. do. It is desirable to use a white reference plate (FIG. 9, 15) as the reference density image. A few seconds after performing step B, the host computer 11 sends the A/D converter 12 a
An A/D conversion command is given, and the tube current control value output by the light intensity feedback unit 8 is converted into an A/D converter.
Convert. This A/D converted value is sent from the host computer 11 until the next A/D conversion command is input to the A/D converter 12.
While being held in the D converter 12, the D/
The signal is transferred to the A converter 13 and subjected to D/A conversion. In response to a command from the D host computer 11, the switch driving device 9 switches the switch 10 to the "b" contact side. As a result, the constant value (tube current control value) held in the A/D converter 12 is input to the fluorescent lamp inverter 14, and the tube current value of the fluorescent lamp 1 is maintained constant. ETherefore, the image that is connected to the rear of the reference density image (white reference plate) for calibration,
The required original image to be copied (FIG. 9, 16) is scanned. F When the original image scanning is completed, the fluorescent lamp is turned off.
However, if you continue to scan the original image,
It is sufficient to continue scanning without turning off the light. Note that, from the viewpoint of work efficiency, it is preferable to keep the heater 4 energized until the end of the day's work. If the original image scanning is to be resumed after the G light is turned off, steps B and subsequent steps are repeated. Here, in step A, the operation from when the power is turned on until the temperature of the fluorescent lamp 1 reaches an equilibrium state will be described. First, when the power is turned on, the heater 4 is activated. Then, the surface temperature of the fluorescent lamp 1 measured by the thermistor is the coldest point temperature (48
The driving of the heater 4 is controlled so as to maintain a constant temperature of 0.degree. C.) or higher. At this time, a heat conduction buffer member 5 is in contact with a part of the tube wall of the fluorescent lamp 1, and through this heat conduction buffer member 5, the heat of the tube wall of the fluorescent lamp 1 is naturally radiated to the outside and cooled. Therefore, the temperature of the portion of the fluorescent lamp tube wall where the heat conduction buffer member 5 abuts is a constant temperature lower than the tube wall temperature of the fluorescent lamp 1 other than that portion, that is, the coldest point temperature. Such control of the coldest point temperature is generally performed at 1 while the heater 4 is energized.
It is executed continuously from the start of the day's work until the end of the day's work. In this device, since a heat storage layer 5b with low thermal conductivity is provided in the heat conduction buffer member 5 for forming the coldest point of the fluorescent lamp 1, for example, during the original image scanning period (usually about 1 to 2 minutes), Even if the ambient temperature of the heat conduction buffer member 5 suddenly changes due to a change in room temperature, etc., the coldest point on the fluorescent lamp tube wall is less affected by the surrounding temperature due to the heat storage effect of the heat storage layer 5b, and the coldest point temperature changes are small. Therefore, the temperature of the coldest spot hardly changes during the original image scanning period in the above device, and a change in the amount of light from the fluorescent lamp 1 is prevented. Furthermore, at the start of scanning the original image, the amount of light reflected by the reference density image of the fluorescent lamp 1 is detected by the optical sensor 6, and during the scanning period of the original image to be copied, the optical sensor 6 detects the amount of light reflected by the reference density image of the fluorescent lamp 1.
The light amount feedback unit 8 controls the fluorescent lamp inverter 14 based on the detected data to adjust the tube current of the fluorescent lamp 1 to be constant, so the light amount of the fluorescent lamp 1 is stabilized in this respect as well. Ru. Actually, in the apparatus shown in FIG.
FIG. 5 shows the results of examining the change in light amount when the fluorescent lamp 1 is turned on after the temperature of the lamp reaches an equilibrium state. In FIG. 5, the horizontal axis represents the time since lighting, and the vertical axis represents the illuminance at approximately the center of the fluorescent lamp 1. As can be seen from the figure, when the fluorescent lamp 1 was turned on, the illuminance instantaneously reached a certain value, and after that, the value decreased by 0.5 to 1.0%, and then stabilized at a substantially constant value. Note that similar results were obtained when the room temperature was between 10 [°C] and 40 [°C]. It was also confirmed that when the room temperature is suddenly changed while the light intensity is stable, there is almost no change in the light intensity during the period required to scan the original image (usually about 1 to 2 minutes). . This shows that the device shown in FIG. 4 has excellent stability of the amount of light. In the above embodiment, glass is used as the heat storage layer 5b, but the heat storage layer 5b may be formed of a material with low thermal conductivity other than glass. Table 1 shows the heat storage layer 5
Alumina, 18-8 stainless steel, or polyethylene is used as b, and the results of actual measurement of the coldest point temperature at room temperature of 10 [°C] and 40 [°C] are shown.

[Table] As shown in Table 1, these aluminas, 18-8
It has been suggested that stainless steel and polyethylene can also be used as the heat storage layer 5b, and it is thought that they have the same effect as when glass is used as the heat storage layer 5b. In either case, the control temperature of the temperature sensor on the surface of the heater 4 is set several degrees higher than the temperature in Table 1 to ensure the coldest point temperature. It is experimentally known that the luminous efficiency of fluorescent lamps is highest when the coldest spot temperature is approximately 40 [°C], and that luminous efficiency decreases both below and above that temperature. However, this value is based on the amount of initial luminous flux obtained when the fluorescent lamp is turned on after it has been left in a constant temperature chamber maintained at approximately 40 [℃] for 2 hours without any preheating means such as a heater. This value was obtained under the condition that the maximum temperature is reached, and it was confirmed that under different conditions, such as continuous lighting conditions, it is desirable to maintain the coldest point temperature at approximately 48 [°C]. Further, in the above embodiment, the heat transfer layer 5a and the heat storage layer 5b
Although the case has been described in which the heat conductive buffer member 5 is constructed by overlapping the heat conductive buffer members 5 and the heat conductive layer 5a is brought into contact with the tube wall of the fluorescent lamp 1, as shown in FIG. 5 may be composed only of the heat storage layer 5b. Further, as shown in FIG. 7, a heat conduction buffer member 5 is composed of a heat dissipation layer 5c and a heat storage layer 5b made of a material with high thermal conductivity such as aluminum, and the heat storage layer 5b is connected to the tube wall of the fluorescent lamp 1. It may be made to contact. Alternatively, as shown in FIG. 8, a heat transfer layer 5a and a heat dissipation layer 5c are provided on both sides of the heat storage layer 5b.
The heat conductive buffer member 5 is constructed by connecting these layers so as to overlap each other, and the heat conductive layer 5a is connected to the fluorescent lamp 1.
It may be made to contact the pipe wall. In either case, the same effects as in the above embodiments are achieved. Further, in the above embodiment, the amount of light is stabilized by combining the heat storage effect of the thermally conductive buffer member 5 and the tube current control, but the tube current control may be omitted. In this case, for example, the electrical signal from the reference plate obtained from the CCD line sensor 20 shown in FIG. 9 may be gain-controlled to obtain a constant value. Further, the tube current control method is not limited to that shown in FIG.
0, a sample holder controlled by the host computer 11 is provided in place of the A/D converter 12 and the D/A converter 13, and first, a tube current control signal that becomes a reference at the start of image scanning is stored in this sample holder. However, during the image scanning period, the fluorescent lamp inverter 14 may be controlled using this tube current control signal so that the tube current is constant. Furthermore, instead of using an independent optical sensor 6 to detect the amount of light from a fluorescent lamp, a line sensor, such as a CCD line sensor, is used to pick up image signals during line-sequential scanning of the original image. The computer may control the fluorescent lamp inverter based on the signal from the fluorescent lamp so that the tube current of the fluorescent lamp is constant. In the above embodiments, the original image scanning device is described as being of a photoelectric scanning type, but it is not limited thereto, and may be a purely optical type that projects an original image onto the surface of a photosensitive material through an imaging lens. It may be hot. (Effects of the Invention) As described above, according to the present invention, the heat conduction buffer member including the heat storage layer made of at least a material with low thermal conductivity is brought into contact with a part of the tube wall of the fluorescent lamp, Since the contact point is configured to be the coldest point, even if the temperature around the coldest point changes, the temperature change at the coldest point is suppressed by the heat storage action of the heat storage layer, and fluctuations in the amount of light are prevented. In addition, it is not necessary to provide something like a conventional Peltier element to stabilize the coldest spot temperature, and it is possible to provide a light amount stabilizing device for a fluorescent lamp that is inexpensive and easy to maintain. Furthermore, when tube current control is used in addition to the heat conduction buffer member, the tube current is stabilized and the amount of light is further stabilized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the light amount stabilizing device for a fluorescent lamp according to the present invention, and FIG.
3 is a perspective view near one end of the fluorescent lamp shown in FIG. 1, FIG. 4 is a block diagram of an original image scanning device using the fluorescent lamp shown in FIG. 1, and FIG. 5 is a sectional view taken along line A. 4
Figures 6 to 8 are diagrams showing other embodiments of the present invention, and Figure 9 is an object to which the present invention is applied. FIG. 1 is a schematic diagram showing an example of an original image scanning device. 1... Fluorescent lamp, 4... Heater, 5... Heat conduction buffer member, 5a... Conductive layer, 5b... Heat storage layer, 5c
... heat dissipation layer, 6 ... optical sensor, 7 ... amplifier,
8...Light intensity feedback unit, 9...Switch drive device, 10...Switch, 11...Host computer, 12...A/D converter, 13...
...D/A converter, 14...Fluorescent lamp inverter, 1
8...Mirror, 19...Lens, 20...CCD
line sensor.

Claims (1)

[Scope of Claims] 1. Heating control means that detects the surface temperature of the tube wall of a fluorescent lamp and controls heating of a required location on the wall of the fluorescent lamp at a predetermined temperature higher than the temperature of the coldest point of the fluorescent lamp; It includes a heat storage layer made of at least a material with low thermal conductivity, and is in contact with an area of the tube wall of the fluorescent lamp other than the area heated by the heating control means,
A light amount stabilizing device for a fluorescent lamp, comprising a heat conductive buffer member whose contact point is the coldest point. 2. In an original image scanning device that uses a fluorescent lamp as a light source for illuminating an original image, the surface temperature of the tube wall of the fluorescent lamp is detected, and a predetermined temperature higher than the temperature of the coldest point of the fluorescent lamp is applied to a required location on the fluorescent lamp tube wall. and a heat storage member made of at least a material with low thermal conductivity, the lamp is in contact with an area of the tube wall of the fluorescent lamp other than the area heated by the heating control means, and A heat conductive buffer member whose contact point is the coldest point; a light amount detection means for detecting the light amount of the fluorescent lamp; and a tube current control means for controlling the tube current applied to the fluorescent lamp based on a detection signal from the light amount detection means. Fluorescent lamp light stabilization device. 3. The heat conduction buffer member further includes a heat transfer layer overlaid on the heat storage layer and having a higher thermal conductivity than the heat storage layer, and the tube wall of the fluorescent lamp is provided with a heat transfer layer of the heat conduction buffer member. The light amount stabilizing device for a fluorescent lamp according to claim 1 or 2, wherein the layers are in contact with each other. 4. The heat conductive buffer member further includes a heat dissipation layer that is superimposed on the heat storage layer and has a higher thermal conductivity than the heat storage layer, and the heat storage layer of the heat conductive buffer member is on the tube wall of the fluorescent lamp. The light amount stabilizing device for a fluorescent lamp according to claim 1 or 2, wherein the device is brought into contact with the light amount stabilizing device. 5. The heat conduction buffer member further includes a heat transfer layer and a heat dissipation layer having a higher thermal conductivity than the heat storage layer superimposed on both sides of the heat storage layer, and the tube wall of the fluorescent lamp is provided with the heat transfer layer. 3. The light amount stabilizing device for a fluorescent lamp according to claim 1, wherein the heat transfer layer of the conduction buffer member is brought into contact with the heat transfer layer.