JPS6183555A - Automatic image density control device in copying machines - 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 TECHNICAL FIELD The present invention relates to an automatic image density control device for a copying machine.

Conventional technology FIG. 9 shows an illumination system in a conventional copying machine.

This irradiates light from a fluorescent lamp 1 onto an original 3 placed on a movable contact crow 2.

The reflected light from the original 3 is focused onto the photoreceptor 5 via the light focusing member 4 f5! This is to form an electrostatic latent image. Here, it is difficult to turn on the fluorescent lamp 1 to a predetermined amount of light in a short period of time due to various factors such as temperature dependence.

Therefore, some devices detect the amount of light from the fluorescent lamp 1 and perform dimming control to maintain a constant amount of light. First, the amount of light from the fluorescent lamp 1 is detected by receiving direct light from the fluorescent lamp 1 through the aperture 6a of the reflector plate 6 by a light amount sensor unit 8 including a light amount sensor 7 such as a photodiode. Then, based on this detection signal, as shown in FIG. 10, the CPU 9 as the main controller outputs a full duty dimming signal to the dimming type ballast 10 to light the fluorescent lamp 1 at full power. It is something. After that, the light intensity sensor unit 8 continues to detect the light intensity of the fluorescent lamp 1, and inputs a voltage proportional to this light intensity to the CPU 9, and compares it with a preset reference value.If there is a difference from the reference value, In order to change the time of the dimming control signal, a command is given to the dimming type ballast 10, and duty control is performed so that the lamp light intensity matches the base i' (Q value. By repeating such detection and control operations, This is to keep the amount of light from the fluorescent lamp 1 constant.

On the other hand, in a copying machine, the optimum image density differs depending on the background density of the original to be copied, so the density of the original to be copied is detected by a density sensor and the exposure amount or developing bias voltage of the original is automatically controlled. Therefore, various proposals have been made regarding automatic image density control devices that control the optimum image once. For example, JP-A-59-7354, JP-A-58-106
571, JP-A-50-42856, JP-A-58-200230, etc.

However, in the past, no proposal has been made for a copying machine equipped with a mechanism for maintaining the light intensity of the fluorescent lamp l at a constant level as described above, which is also equipped with such an automatic image density control device. Not yet. Although it is possible to install both mechanisms, since there is no direct relationship between them, they would have to be installed completely separately, which would increase the size of the circuit configuration.

This will lead to complications, etc.

Purpose The present invention has been made in view of the above points, and is an automatic side (
The purpose is to obtain a 91 Vi degree control device.

Structure In order to achieve the above object, the present invention provides a light amount sensor unit that detects the light amount of the document illumination lamp in order to maintain the light amount of the document illumination lamp constant at all times, and a light amount sensor unit that detects the light amount of the document illumination lamp in order to maintain the light amount of the document illumination lamp constant. Detecting document density: This device is characterized in that it is integrated with a density sensor unit.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 8. First, FIG. 1 shows an illumination system. Basically, light from a fluorescent lamp 11 is irradiated onto an original 13 placed on a movable contact glass 12, and the light from this original 13 is illuminated. An electrostatic latent image is formed by forming an image on a photoreceptor 15 via a focusing member 14 (for example, Rinse (trade name)). Here, the fluorescent lamp 11 is of an aperture type, and the irradiation direction of the fluorescent lamp 11 is regulated and the efficiently focused light is transmitted through the opening 16a+ of the light-shielding cover 16, which serves to prevent glare, prevent stray light, and improve aesthetic appearance. The original 13 on the contact glass 12 is irradiated through the i-.

The reflected light from the original 13 is imaged onto the photoreceptor 15 by the light focusing member 14.

Therefore, the direct light from the fluorescent lamp 11 is reflected by the reflecting plate 1.
A light amount sensor unit 19 including a light amount sensor 18 such as a photodiode received through the opening 17a of the fluorescent lamp 1 is mounted on the circuit board 20.
It is configured to detect a light amount of 1. Further, on this circuit board 20, there is a document folding line f'Jri of the document 13.
Concentration sensor 2 using a photodiode, etc. to detect the concentration
A concentration sensor unit 22 including the light amount sensor unit 19 is also mounted, and is integrated with the light amount sensor unit 19.

Here, the light amount sensor unit 19 and the density sensor unit 22 will be explained in more detail.

First, the light amount sensor 18 of the light amount sensor unit 19 is oriented horizontally toward the fluorescent lamp 11 side as shown in FIGS.
The lead wire 24 is fixed to the circuit board Fi20 with solder 25. On the other hand, the concentration sensor 21 of the concentration sensor unit 22 is oriented upward toward the contact glass 12 as shown in FIG. It is fixed to the circuit board 20 by 28.

The concentration sensor 21 is located near the fluorescent lamp 11 so that it does not receive direct light from the fluorescent lamp 11 as well as specularly reflected light from the contact glass I2. That is, in FIG. 1, the light emitted from the fluorescent lamp 11 is irradiated onto the original 13 between the line a and b that can pass through the opening 16a of the light shielding cover 16, and the light between the line a and a' is irradiated onto the document 13. Although the image information is reflected to the light focusing member 14 side, the concentration sensor 21 is arranged in a position where the irradiated light is placed almost directly below the irradiated surface on the PB side to avoid regular reflection on the lower surface of the contact glass 12. ing.

Therefore, the light shielding cover 16 has a hole 1 for protruding the light shielding tube 2G.
6b is formed.

Next, FIG. 6 shows the arrangement seen in a plan view. The copying machine of this embodiment has a central convex mark 30 and a size indication tjlc31.
Accordingly, a central reference method is adopted in which the document 13 is set on the contact glass 12, and the density sensor 21 is placed near an extension of the central reference mark 30. The light amount sensor 18 is arranged at the end of the circuit board +ff20 near the concentration sensor 21.

The detection outputs of the light amount sensor unit 19 and the degree sensor unit 22 are input to the CPU 32 as a main controller, and the lighting state of the fluorescent lamp 11 is controlled via the dimming type ballast 33. It is configured.

With such a configuration, basically in a method of dimming control to a constant light amount, the density sensor unit 22 is provided to detect the reflected density of the original, and its detection output is input to the CPU 32 and sent to the dimming type stabilizer 33. By issuing a command, it is possible to set the optimal amount of lamp light for correcting the background density of the document. This operation will be explained with reference to the flowchart in FIG. First, by setting the original 13 to be copied on the contact glass 12, closing the original pressing plate (not shown), and pressing the print key.

A copy operation is started. Here, the optimum copying conditions are set before copying when the exposure run actually starts.

When the print key is pressed, the CPU 32 outputs a full duty dimming signal to the dimming type ballast 33, and the fluorescent lamp 11 lights up at full power. In this state, direct light from the fluorescent lamp 1 is received by the light sensor 18 of the light sensor unit 19 through the opening 17a of the reflector 17.

A voltage proportional to the amount of light is input to the CPU 32, and this CPU
32, the time of the tip control signal is changed so as to reach the reference value, and it is monitored whether the amount of light becomes constant at the reference light amount. When it is confirmed that the amount of light has become constant, the contact glass 12, which had been stopped at the center, returns to the exposure start position. At the time of return, the density sensor 21 of the density sensor unit 22 reads the document information and inputs it to the CPU 32, so that the CPU 32 sets a light amount reference value that provides the optimum exposure light amount. When the light amount reference value corresponding to the document 13 is set in this way, the constant light control by the light amount sensor unit 19 is performed again, and the fluorescent lamp 1
Dimming control is performed so that the light amount of No. 1 becomes a constant light amount at this light amount reference value. In this way, when it is confirmed that a constant light amount has been reached with the light amount reference value suitable for the original document 13, the contact glass 12 starts traveling for exposure, and the copying operation is actually performed. When copying is completed, the contact glass 12 stops again at the center of the machine.

Prepare for the next copy.

Here, when detecting the quality of the original, the density sensor 21 is placed near the fluorescent lamp 11 at a position where it does not receive the direct light from the fluorescent lamp [1] as well as the specularly reflected light from the contact glass 12; Since stray light is prevented by the light-shielding tube 26, a relatively large photocurrent can be obtained.
The S/N ratio is also good, and the configuration of the amplifier circuit in the ε degree sensor unit 22 can be simplified. Specifically, the amount of light received by the density sensor 21 is only about 115 to 1/20 of the amount of light received by the light amount sensor 18. This is because if the density sensor 21 is placed in a position where it can receive the specularly reflected light from the lower surface of the contact glass 12 even if it avoids direct light from the fluorescent lamp [1], a slight amount of reflected light from the original 13 will be detected. This is because the user will receive a larger amount of light close to direct light, and no original information can be obtained.・Here, the diameter of the light-shielding tube 26 is the same as that of the concentration sensor 2.
It is also preferable from the viewpoint of S/N that the diameter is several times or less than the diameter of 1. Moreover, since such a concentration sensor 2I is arranged near the extension line of the central Kisho mark 30,
Even if the size of the document 13 is different, the detection operation can be performed reliably. Also, for the concentration sensor 21 facing upward,
Since the contact glass 12 is always present above it,
There is no need to worry about contamination due to dust, detection failure, etc.

On the other hand, as shown in FIG. 6, the light amount sensor 18 is not necessarily placed near the concentration sensor 21, and may be placed anywhere that receives direct light. By arranging it together with the sensor 21 in the center and integrating it, it is possible to make it compact and inexpensive. FIG. 7 shows an example of the circuit configuration of the light amount sensor unit 19 and the concentration sensor unit 22 that are integrally mounted on the circuit board Vj, 20. To explain briefly, the light amount sensor unit 19 is the light amount sensor 18
and two OP amplifiers 34 and 35, and the concentration sensor unit 22 is similarly composed of a concentration sensor 21 and OP amplifiers 36 and 37. Here, both sensors 18 and 21 have a photodiode configuration, and are connected directly between the + and - of the OP amplifier 34 and 36, so that they are used at fm without applying voltage to prevent dark current from flowing. It is configured. However, as mentioned above, the photocurrent of the two sensors 18.21 is at most 5:1~20.
:The difference is only about 1, and basically the resistance values of the resistors Ra and Rb of the OP amplifier 34 and 36 for converting photocurrent into voltage can be adjusted to this ratio, so as shown in Fig. 7. In addition, one so-called quad-type OP amplifier rC, which has four OP amplifier circuits in one IC package, has two
Circuits for two sensor units 19.22 can be integrated. This makes it possible to share the power @Vcc line, ground GND line, etc., reduce connector pins, save space, make it smaller and more compact, and lower costs, making it possible to perform the specified functions. .

In this embodiment, a lamp light amount control method using pre-scanning was explained as a method for automatically controlling the optimum image density. However, it is possible to control the developing bias voltage according to the document density without pre-scanning. ,
The image density may be automatically controlled to the optimum image quality.

Effects In the present invention, since the light amount sensor unit and the concentration sensor unit are integrally provided as described above, one ○P
The amplifier EC can be equipped with two sensor amplifier circuits, so the number of connector bins can be reduced by sharing the power supply, ground, etc., space-saving, compact size, and low cost. It is possible to achieve constant light amount adjustment and optimal image density adjustment.

[Brief explanation of the drawing]

1 to 8 show an embodiment of the present invention,
Figure 1 is a vertical side view, Figure 2 is a block diagram, Figure 3 is a front view showing how the light sensor is installed, Figure 1 is a vertical side view, and Figure 5 is a 15 degree sensor installation. 6 is a plan view, 7 is a circuit diagram, and 8 is a longitudinal side view showing the state.
The figure is a flowchart, FIG. 9 is a longitudinal sectional side view showing a conventional example, and FIG. 10 is a block diagram. 11 Fluorescent lamp (original illumination lamp), 19 Light sensor unit, 22 Concentration sensor unit 1 ~ Applicant Ricoh Co., Ltd. - Figure 36 Figure 1Eq Figure 0 Figure 0

Claims (1)

[Claims] A light intensity sensor unit that detects the light intensity of the document illumination lamp in order to keep the light intensity of the document illumination lamp constant at all times, and a density sensor unit that detects the document density to automatically control the optimum image density are integrated. An automatic image density control device for a copying machine, characterized in that it is incorporated into a copying machine.