JPH0786650B2 - Method and device for stabilizing fluorescent light quantity in original image scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a method of scanning an original image to be reproduced such as photoengraving with a photoelectric scanning unit to obtain an image signal for recording the original image. The present invention relates to a fluorescent light quantity stabilizing method and apparatus in an original image scanning apparatus that eliminates fluctuations in the light quantity of a fluorescent lamp used as an illumination light source.

[Prior Art] Fluorescent lamps generally used as an illumination light source are also used in the field of printing plate making, for example, in the case of color separation plate making of an original color image, the spectral distribution is almost equal to the luminosity factor and the heat generation amount is small. It is highly useful as a light source. In particular, in image reading devices using semiconductor photosensors such as CCDs, which have been widely spread in recent years, a light source having a spectral characteristic containing a large amount of infrared light such as a halogen lamp deteriorates the quality of a duplicate image, and It is considered desirable to be able to apply lights.

However, in spite of such demand, conventionally,
Fluorescent light sources are rarely used in the field of photolithography.

The reason for this is that the light quantity of the fluorescent light source is unstable especially for a while immediately after lighting, and the light quantity fluctuates within a relatively short time during lighting. That is, in the field of photoengraving in which the original image is scanned line-sequentially and the image density information is read at high density, if the amount of light irradiating the original image changes within the scanning period, an error occurs in the read density data,
There is a problem in using a fluorescent lamp, and a light source such as a halogen lamp with little fluctuation in light amount is used.

On the other hand, a fluorescent lamp is used as a light source of a copying machine or the like.
This is because the time required to read the original image is
This is because even an original image of about A3 size, which is the maximum size, usually takes only a short time of about 1 second, and the fluctuation of the light amount during that time is minute and can be ignored.

In addition, even in scanning devices such as Facsimile, fluorescent lamps are used as the light source.
In many cases, the image is binarized in black and white and there is no intermediate density, and there is no problem even if there is a slight change in the amount of light, so it is possible to apply a fluorescent light source.

Further, as a means for stabilizing the light quantity and the light quantity distribution of the fluorescent light source, it is known to keep the position of the lowest temperature (hereinafter referred to as the coldest point) in the fluorescent lamp tube and its temperature constant. There is.

FIG. 5 is a block diagram showing the outline of the device of the first embodiment, in which light from a fluorescent lamp (1) is received by an optical sensor (2) for monitoring the amount of light, and its output is output to an amplifier (3) and an amount of light. Input to the fluorescent lamp inverter (5) via the feedback unit (4).

The light intensity feedback unit (4) is equipped with an optical sensor (2).
The fluorescent lamp inverter (5) is controlled according to the signal level from (1) to adjust the tube current flowing through the fluorescent lamp (1), and the output level of the optical sensor (2) is always maintained at a constant value.

On the other hand, in order to control the position of the coldest spot of the fluorescent lamp (1) and its temperature, a cooling element (6) such as a Peltier element is installed in contact with the tube wall at an appropriate position on the tube end, and the cooling element ( A temperature sensor (7) such as a thermistor is inserted between 6) and the pipe wall, and the detected value is sent to the cooling element driver (8) so that the temperature at the coldest point is maintained at a desired value. A cooling element (6)
To control.

Also, in order to ensure that the place where the cooling element (6) is installed is the coldest spot, the other part of the fluorescent lamp (1) is heated by a heater (9) arranged in a line with an appropriate pitch. , The temperature of the fluorescent lamp (1) is detected by a temperature sensor (10) installed at an appropriate place, and the heater (9) is controlled by a control means (not shown) to keep the temperature at a temperature higher than the temperature of the coldest spot. To do.

[Problems to be Solved by the Invention] In the conventional means shown in FIG. 5, the optical sensor (2) is a fluorescent lamp (1).
When only the amount of light from the light source is received, the desired light amount stabilization effect can be obtained, but when applied to the original image scanning device, in addition to the amount of direct light from the fluorescent lamp (1), reflection on the duplicated original screen is achieved. There is a problem that an error occurs because the generated light beam is incident on the optical sensor (2).

That is, when the original image has a gradation of light and shade, the amount of light incident on the optical sensor (2) during scanning of the high density region (dark portion) of the original image is smaller than that during scanning of the low density region (light portion). Therefore, the light quantity feedback unit (4) controls the fluorescent lamp inverter (5) so as to increase the tube current in the same manner as when the light quantity of the fluorescent lamp (1) is reduced. On the contrary, when scanning the low-density region of the original image, control is performed so as to reduce the tube current. Therefore, the means shown in FIG. 5 cannot keep the fluctuation of the light quantity of the fluorescent lamp (1) at the accuracy required for scanning the original image in photoengraving (usually, preferably within 1%). .

No matter how the position of the optical sensor is considered, the change in the original image density affects the amount of light received by the optical sensor, so it is impossible to eliminate this inconvenience as long as the light amount feedback control is activated during scanning of the original image. .

[Means for Solving the Problem] The present invention aims to solve the above-mentioned problems.
It is configured as follows:

That is, the method of the present invention, while maintaining a part of the tube wall of the fluorescent lamp for irradiating the scanned original image at a constant temperature lower than other parts, while detecting the light amount of the fluorescent lamp, the detected value Feedback control means based on, so that the detection value is constant, in the fluorescent lamp light amount stabilization method in the original image scanning device for controlling the tube current of the fluorescent lamp, the step of irradiating the reference density image by the fluorescent lamp, The step of receiving the reflected light or the transmitted light from the reference density image by the optical sensor and detecting the light intensity value, and the feedback control of the tube current value of the fluorescent lamp so that the detected light intensity value becomes a constant value. To stop the feedback control to keep the tube current value of the fluorescent lamp constant, and the step of irradiating and scanning the original image to be scanned by the fluorescent lamp having the tube current value kept constant. And flop, a fluorescent lamp light intensity stabilization process, the original scanning device is characterized in that more configurations.

Further, the apparatus of the present invention comprises a fluorescent lamp for irradiating the original image to be scanned, and a cooling means for setting the coldest point for keeping a predetermined position of the tube end portion of the fluorescent lamp at a constant temperature lower than other parts, Based on the detection value of the light amount detecting means for detecting the light amount of the reflected light or the transmitted light irradiated with the reference density image by the fluorescent lamp, and controlling the tube current of the fluorescent lamp to detect the detected light amount. Feedback control is performed so that it becomes a constant value, feedback control is canceled when the light amount detection value becomes a constant value, and the tube current value at that time is held to maintain the light amount of the fluorescent lamp at a constant value. A fluorescent lamp light quantity stabilizing device in the original image scanning device, comprising:
Is.

[Operation] A predetermined light amount value was obtained by maintaining the tube wall temperature of the fluorescent light constant and feedback-controlling the fluorescent light so that the reflected or transmitted light amount value from the reference density image becomes a constant value. After that, by stopping the feedback control and scanning the scanned original image while keeping the tube current of the fluorescent lamp constant, the original image can be scanned with an appropriate constant light amount value regardless of the density of the original image. .

First Embodiment FIG. 4 is a schematic view showing an example of the original image scanning device according to the present invention.

The white reference plate (32) and the original image to be duplicated (38) are mounted on an original stage (not shown) and are transferred in the direction of the arrow (31) by an appropriate driving means.

The light from the fluorescent lamp (1) first passes through the white reference plate (32).
Next, the original image (38) to be duplicated is irradiated, and the reflected light is changed in direction by the mirror (33) and passed through the lens (34) to the CCD (3
The image is projected and formed on the photoelectric element such as 5), and the image signal of the duplicated original image (38) is output from the CCD (35).

The present invention is means for stabilizing the light quantity of the fluorescent lamp (1) in such a scanning device, and FIG. 1 shows a block diagram of the device of the first embodiment of the present invention.

A fluorescent lamp (1), a cooling element (6) for keeping the temperature of the tube wall at a predetermined position of the tube end at a constant temperature of the coldest point, a temperature sensor (7) and a cooling element driver (8), A temperature control system such as a heater (9) and a control temperature sensor (10) for heating a pipe wall other than the coldest spot to a required temperature higher than the coldest spot, and an optical sensor (2) in the light quantity control system. ), The amplifier (3) and the light quantity feedback unit (4) are constructed in the same manner as in the fifth illustrated means.

The output of the light quantity feedback unit (4) is directly connected to the fluorescent lamp inverter (5) when the switch (15) is connected to the "a" contact side via the path branched into two.
To enter. This state is the same as the fifth illustrated means.

The switch (15) has a host computer (20) described later.
By the switch drive device (16) controlled by
When switched to the "b" contact side, the output of the light amount feedback unit (4) is sequentially passed through the A / D converter (18) and the D / A converter (19), and then the "b" of the switch (15). Via the contact to the fluorescent light inverter (5).

The host computer (20) outputs an A / D conversion instruction to the A / D converter (18) and a switching command signal to the switch driving device (16), and the A / D converter (18) outputs A
It also has a function of reading the output value (tube current control value) of the light quantity feedback unit (4) that has been / D converted.

The operation of the first illustrated device will be described in the order of steps.

(A) First, the power supply is turned on to activate the cooling element (6) and the heater (9), and wait for a required time (about several minutes) until the temperature of the fluorescent lamp (1) becomes a uniform state. During this waiting period, the fluorescent lamp is not turned on.

This step (A) is usually performed at the start of the work for one day.

(B) The switch driving device (16) switches the switch (15) to the "a" contact side to turn on the fluorescent lamp. At this time,
On the surface to be scanned, attach the reference density image and the original copy image,
While scanning the reference density image, the amount of light incident on the optical sensor (2) is set to be a constant value for calibration. It is desirable to apply a white reference plate (Fig. 4 (32)) as the reference density image.

(C) A few seconds after step (B), the host computer (20) gives an A / D conversion command to the A / D converter (18) and controls the tube current output by the light quantity feedback unit (4). A / D convert the value. The A / D-converted value is held in the A / D converter (18) from the host computer (20) until the next A / D conversion instruction is input to the A / D converter (18). On the other hand, the data is transferred to the D / A converter (19) at the next stage and D / A converted.

(D) In response to a command from the host computer (20), the switch driving device (16) switches the switch (15) to the "b" contact side. As a result, the fluorescent lamp inverter (5) is connected to the A / D
Constant value (tube current control value) held in the converter (18)
Is input to maintain the tube current value of the fluorescent lamp (1) constant.

In addition, since the position of the coldest spot on the tube wall and the temperature thereof are maintained at constant values throughout, the amount of light of the fluorescent lamp (1) and the light amount of the fluorescent lamp (1) after the steps (B) to (D) are performed. No change occurs in the light quantity distribution.

(E) Then, the required original image to be duplicated, which is connected to the subsequent stage of the reference density image for calibration (white reference plate), is scanned.

(F) When the original image scanning is completed, the fluorescent lamp is turned off. However, when the original image scanning is subsequently performed, the scanning may be continued without turning off the light. In addition, in terms of work efficiency, it is preferable that the cooling element (6) and the heater (9) be energized until the end of the work for one day.

(G) If the original image scanning is to be restarted after the light is turned off, step (B) and subsequent steps are repeated.

By the above procedure, the stable state of the light quantity and the light quantity distribution of the fluorescent lamp (1) is realized. Furthermore, in step (C), the output value of the light quantity feedback unit (4), that is, the change of the light quantity of the fluorescent lamp is detected. , A / D converter (18) A / D converts the tube current control signal for instructing the fluorescent lamp inverter (5) to increase or decrease the tube current, and transfers it to the host computer (20) for display. This makes it possible to know when to replace the fluorescent lamp.

That is, it is known that the fluorescent lamp needs to increase the tube current in order to obtain a constant amount of light as it approaches the end of the life period. Therefore, step (C)
By this, the tube current control signal transferred to the host computer (20) is digitally displayed on the display means, and if it is judged that the value exceeds a certain level, it is possible to know the replacement time very accurately. .

In the above, the A / D converted value does not indicate the tube current value as it is, but for example, the A / D converted value is “10.
The tube current value of "0" is "200 mA", and the tube current value of "1000" is "400 mA".

Second Embodiment FIG. 2 is a block diagram showing the configuration of the second embodiment device of the present invention.

Of the fluorescent lamp (1), the cooling element (6), the temperature sensor (7), the cooling element driver (8), the heater (9), the heater temperature sensor (10), and the like, and the light amount control system The optical sensor (2), the amplifier (3) and the light quantity feedback unit (4) are the same as in the first embodiment device.

In this embodiment, the A / D converter (1
8), the D / A converter (19), the switch (15) and the switch driving device (16) are replaced with a sample holder (25), which is a droop
It is necessary to use one having a small rate, that is, one in which the held tube current control signal does not change or the amount of change is as small as possible.

The sample holder (25) passes or holds a tube current control signal to the fluorescent lamp inverter (5) input from the light quantity feedback unit (4) in accordance with a command from the host computer (20).

The operation of the device of the second embodiment will be described in the order of steps.

(A) As in the step (A) of the first embodiment, the power is turned on to activate the cooling element (6) and the heater (9),
Wait a few minutes for equilibrium.

(B) With the sample holder (25) in the sample state, that is, with the feedback control in which the tube current control signal from the light quantity feedback unit (4) is input to the fluorescent lamp inverter (5), the fluorescent lamp (1) Lights up. At this time, on the surface to be scanned, as in the first embodiment,
Attach the standard density image (white standard plate) and the original image to be duplicated,
First, the reference density image is scanned.

(C) A few seconds after step (B), the sample holder (25) is instructed by the host computer (20).
Is switched to the hold state, and the tube current control signal at that time is held.

As a result, the fluorescent lamp inverter (5) causes the fluorescent lamp (1) to operate with a constant tube current corresponding to the held control signal.
Is lit in a state where the light amount and the light amount distribution are stable.

(D) A reference density image (white reference plate) is scanned, and then a desired original copy image is scanned.

(E) When the original image scanning is completed, the fluorescent lamp (1) is turned off. However, when the original image scanning is continued, the scanning is continued without turning off the light.

(F) When restarting after turning off the fluorescent lamp, step (B) and subsequent steps are repeated.

Also in this second embodiment, the tube current input to the fluorescent lamp (1) having a part of the tube end as the coldest point of a constant temperature corresponds to the control signal value held in the sample holder (25). Since the light is turned on at a constant value, the light amount and the light amount distribution can be stabilized.

[Third Embodiment] A third embodiment of the present invention does not use an independent optical sensor for detecting the light quantity of a fluorescent lamp, but a line sensor for picking up an image signal during line-sequential scanning of an original image,
For example, the CCD is also applied to control the light quantity stabilization of the fluorescent lamp. FIG. 3 is a perspective view showing the outline of the device of the third embodiment.

The fluorescent lamp (1) is provided with a cooling means (6) for keeping the position of the coldest point and its temperature constant, a temperature sensor (7), and a heater (not shown), as in the apparatus of each of the embodiments. It is attached.

On the surface to be scanned illuminated by the fluorescent lamp (1), a white reference plate (3
2), and the duplicate original image (3
8) is attached, and the reflected light from them is projected and imaged on the CCD line sensor (35) by the mirror (33) and the lens (34). At this time, a light-shielding plate (not shown) is attached to the fluorescent lamp (1) to prevent direct light from entering the lens (34).

Output signal of CCD line sensor (35) is A / D converter (16)
Is input to the host computer (20) via the host computer (20), and the host computer (20) outputs the tube current control value to the fluorescent lamp inverter (5) via the D / A converter (19) based on the data. .

The operation of the third embodiment device will be described in the order of steps according to the above description.

(A) Turn on the power to operate the cooling element and the heater,
Allow a waiting time to stabilize the temperature of the fluorescent lamp. (Similar to each of the above embodiments) (B) The host computer (20) causes the D / A converter (1
The tube current control value is output to the fluorescent lamp inverter (5) via 9) to turn on the fluorescent lamp (1). The tube current control value designated here is “A”. This designated value is a substantially constant value when the fluorescent lamp is new.

(C) The reference density image (white reference plate) is aligned with the position to be scanned, and is projected and imaged on the CCD line sensor (35) by the lens (34). The line sensor (35) transfers a light amount signal having a level corresponding to the received light amount to the host computer (20) via the A / D converter (16).

(D) The host computer (20) determines, based on the transferred data, whether the amount of light of the fluorescent lamp being turned on is at an appropriate level or whether there is an excess or deficiency. This decision is
It is performed by comparing with a light amount value of an appropriate level set in advance.

(E) When it is determined that the light amount is at an appropriate level, the designated tube current control value "A" is held, and then the original image to be duplicated is scanned.

(F) If the host computer (20) determines that there is an excess or deficiency in the amount of light, the host computer (20) calculates the amount by which the tube current value should be increased or decreased, and the tube current control value “A ′” corresponding to that value is set to D / A
Input to the fluorescent lamp inverter (5) via the converter (19). After this correction, if there is still an excess or deficiency in the light quantity, the same operation is repeated until the light quantity of an appropriate level is obtained. If the light amount is at a desired level, the host computer (20) stores the corrected tube current control value "A '" as "A". That is, the operation of “A ′ → A” is performed.
As a result, the fluorescent lamp is turned on with the light amount of the level corresponding to the tube current control value "A '", and the tube current control value is held,
The original image is scanned.

(G) When the original image scanning is completed, the fluorescent lamp is turned off. However, when the original image scanning is continued, the work is continued without turning off the light.

(H) When the work is restarted after the fluorescent lamp is turned off, the steps from (B) are repeated.

Also in this third embodiment, since the tube current value is controlled to be constant by the host computer (20), the light quantity and the light quantity distribution should be stabilized if the position and temperature of the coldest point are kept constant. You can Further, it is possible to display the corrected tube current value calculated in step (F) on an appropriate display means to grasp the progress of the life period of the fluorescent lamp, as in the first embodiment.

Further, in the device of the third embodiment, since the light quantity of the fluorescent lamp is detected by the line sensor for image scanning, it is not necessary to separately provide an optical sensor, and the feedback control is performed by the function of the host computer. Since this is performed, there is an advantage that the light quantity feedback unit in both the first and second embodiments can be omitted.

In each of the above-described embodiments, the operation for stabilizing the light amount is performed during irradiation of the white reference plate, but if the white reference plate has a certain fixed density, a white reference plate other than that is used. It is also possible.

Further, the above description is based on the embodiment in which the present invention is applied to the reflection type original image scanning device, but it goes without saying that it is also applicable to the case of a transmission type original image.

[Advantages of the Invention] The tube current value of the fluorescent lamp is feed-back controlled so that the light intensity detection value irradiated with the reference density image becomes a constant value, and the feedback control is stopped when the constant light intensity detection value is obtained. Since the tube current value of the fluorescent lamp is maintained at the value at that time, as in the conventional feedback control,
The amount of detected light is affected by the density change of the scanned image,
The inconvenience that causes an error can be eliminated, and the light amount and the light amount distribution can be stabilized.

[Brief description of drawings]

FIG. 1 is a block diagram showing the structure of a first embodiment device of the present invention, FIG. 2 is a block diagram showing the structure of a second embodiment device, and FIG. 3 is a structure of the third embodiment device. FIG. 4 is a perspective view, FIG. 4 is a schematic diagram showing an outline of an original image scanning device to which the present invention is applied, and FIG. 5 is a block diagram showing conventional means. (1) ... Fluorescent lamp, (2) ... Optical sensor, (3) ... Amplifier, (4) ... Light quantity feedback unit, (5)
...... Fluorescent lamp inverter, (6) …… Cooling element, (7)…
… Temperature sensor, (8)… Cooling element driver, (9)…
… Heater, (10) …… Temperature sensor for heater, (15) ……
Switch, (16) …… Switch drive, (18) …… A /
D converter, (19) …… D / A converter, (20) …… Host computer, (25) …… Sample holder, (32) …… White reference plate, (33) …… Mirror, (34) ...... Lens, (35)
…… Line sensor, (38) …… Reproduced original image.

Claims (2)

[Claims] 1. A fluorescent lamp for irradiating an original image to be scanned is held at a constant temperature, which is lower than other parts of the fluorescent lamp, while detecting the light quantity of the fluorescent lamp and feeding back the detected value. By the control means, so that the detection value becomes constant,
In a fluorescent light quantity stabilizing method in an original image scanning device for controlling a tube current of the fluorescent lamp, a step of irradiating a reference density image with the fluorescent lamp, and a reflected light or a transmitted light from the reference density image is received by an optical sensor. Then, the step of detecting the light intensity value, the step of feedback controlling the tube current value of the fluorescent lamp so that the detected light intensity value becomes a constant value, the feedback control is stopped, and the tube current value of the fluorescent lamp is stopped. The method for stabilizing the quantity of fluorescent lamp light in the original image scanning device is characterized by comprising: a step for holding the tube current value constant; and a step for irradiating and scanning the original image to be scanned with the fluorescent lamp for which the tube current value is held constant. , 2. A fluorescent lamp for irradiating an original image to be scanned, and a cooling means for setting a coldest point for holding a predetermined position of a tube end portion of the fluorescent lamp at a constant temperature lower than other parts, the fluorescent lamp. The light amount detecting means for detecting the light amount of the reflected light or the transmitted light irradiated with the reference density image by means of, and the tube current of the fluorescent lamp is controlled based on the detection value of the light amount detecting means so that the detected light amount becomes a constant value. Feedback control so that the feedback control is released when the light amount detection value becomes a constant value, and the tube current value at that time is held, and the light amount of the fluorescent lamp is maintained at a constant value. A fluorescent lamp light quantity stabilizing device in an original image scanning device.