JPH07219315A - Image forming device - Google Patents

Abstract

PURPOSE:To improve the efficiency in the use of an image forming device by setting a quantity of light required at the time of reading the density of an original lower than that required at the time of normal image exposure, thereby shortening standby time when taking a copy in density detection mode. CONSTITUTION:A light-quantity detection means 103 controls a quantity of light of a fluorescent lamp 4 as the exposure light source according to a quantity of light detected by a photodetector 103a, and an original density detection means 40 controls a quantity of light of the fluorescent lamp 4 according to the density of the original detected by a photodetector 40a. When a copy is taken in the density detection mode, an original reading device moves to a prescribed position and the density of the original is detected by the original density detection means 40. Here, in the normal image exposure, a large quantity of light is required to form a latent image on a photoreceptor. However, in the detection of the density of the original, the density can be controlled even with a small quantity of light by amplifying a minute signal detected by the photodetector 103a. Therefore, by separately setting the quantity of light required for the density detection and the quantity of light required for the normal exposure, the quantity of light required for reading can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a document reading device using a fluorescent lamp as an exposure light source.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine having an original reading device using a fluorescent lamp, when reading in the original density detection mode, the reading needs a light amount equivalent to that in normal image exposure. Met.

[0003]

However, in the conventional example as described above, when the power of the copying machine is turned on and the first copy is made in the density detection mode, the light amount required for reading is the normal image. The same amount of light as during exposure was required. Light quantity of such fluorescent lamps are generally after lighting, to the temporal change such as shown in an example of the time characteristic curve in FIG. 6 by the environmental temperature, the waiting time t ₂ until the quantity of light required to read Is required, and especially in a low temperature environment, time t ₃ is required.

Therefore, in the conventional image forming apparatus of this type, even when copying is performed in the original density detection mode,
Especially when the environmental temperature is low, there is a waste of time in that the reading requires a relatively long waiting time equivalent to that in the normal image exposure.

The present invention has been made in order to solve the above problems in the prior art, and an object thereof is to provide a means for shortening the waiting time when copying is performed in the density detection mode.

[0006]

Therefore, in the present invention, in this type of image forming apparatus, a fluorescent lamp as an exposure light source, a lighting means for lighting the fluorescent lamp, and a lighting means are controlled. Control means, a light amount detecting means for detecting the light amount of the fluorescent lamp, and a density detecting means for reading the density of the original, and when reading the original density by the density detecting means, the reading is performed. By configuring the required light intensity to be lower than during normal image exposure,
It is intended to achieve the above object.

[0007]

With the configuration of the present invention as described above, the time required for reading the original density during copying in the original density mode can be shortened and the utilization efficiency of the image forming apparatus can be improved.

[0008]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a schematic structural explanatory diagram of an embodiment of a copying machine according to the present invention.

In FIG. 1, 101 is a fluorescent lamp 4 as an exposure lamp and a light receiving element 103 such as a photodiode.
An original reading device including a light amount detection unit 103 including a and a first mirror stand 5, 12 is a photoconductor (drum) that forms a latent image, and 40 is an original including a light receiving element 40a such as a photodiode. The density detecting means, 102 is a controller section for controlling the above means.

In FIG. 1, numeral 3 is a platen glass,
4 is a fluorescent lamp, 5, 6, 7, 8, 9, 10, 11 are first to first
A sixth mirror stand, 13 is a primary charger, 14 is a transfer unit, 15 is a developing unit, 20 is a transport unit, 21 is a fixing unit, 23 is a paper feed cassette, 24 is a manual feed unit, and 25 is a driving synchronous motor. Since these and other respective components shown in the drawing are the same as those in the conventional general image forming apparatus of this type and are known and have no direct relation to the gist of the present invention, description thereof will be omitted.

FIG. 2 shows a control means 103 for controlling the light quantity of the fluorescent lamp 4 according to the light quantity detected by the photodiode 103a, and the photodiode 40a.
6 is a block diagram showing a document density detecting means 40 for controlling the light amount of the fluorescent lamp 4 in accordance with the document density detected by.

In FIG. 2, 103a is a light receiving element shown in FIG. 1 for detecting the light quantity of the fluorescent lamp 4, and 103a.
Reference numeral b is a current-voltage conversion circuit for converting the detection signal of the light receiving element 103a into a voltage. 102 is the light receiving element 10
Reference light amount setting circuit 104 for setting a reference light amount (light amount necessary for exposure) for comparison with the detection signal from 3a.
And a comparison circuit 107 for comparing the detected light quantity with the reference light quantity, and a lighting control means 105 for controlling the lighting of the fluorescent lamp 4, 106 is a document, 4
Reference numeral 0a is a light receiving element shown in FIG. 1 for detecting the original density, and 40b is a current-voltage conversion circuit for converting the detection signal of the light receiving element 40a into a voltage.

Next, the operation in FIG. 2 will be described; when the operator performs a copying operation in the normal mode, when a copy key (not shown) is pressed, the fluorescent lamp 4 of the original reading apparatus 101 in FIG. The fluorescent lamp 4 is turned on. that time,
The light receiving element 103a detects the light amount of the fluorescent lamp 4 and compares it with the normal image exposure reference light amount set in the comparison circuit 107. When the detected light amount reaches a predetermined reference light amount, the original on the original platen glass 3 is read, First to sixth mirror stands 5, 6,
Photoconductor (drum) 12 along the path of 7, 8, 9, 10, and 11
A latent image is formed on it. The subsequent processing operations are the same as those of the conventional general image forming apparatus of this type and are known, and therefore the description thereof is omitted.

On the other hand, when the original 106 in FIG. 2 is copied in the density detection mode, the original density is read by pressing a copy key (not shown).
01 moves to a predetermined position in the direction of the arrow in FIG. 1, and the document density detecting means 40 detects the document density. 3 is an output characteristic diagram of the density detection output voltage with respect to the document concentration, and FIG. 4 is a characteristic diagram of the developing bias voltage with respect to the detection output voltage. Here, when the original density is "dark", the developing bias voltage is increased in the negative direction, and the toner adhered to the photoconductor 12 is controlled to be reduced. On the contrary, when the document density is in the “light” direction, more toner adheres to the photoconductor 12, but when the detection output voltage is below a certain value, too much toner adheres to the photoconductor 12. It also controls to prevent it.

FIG. 5 is a characteristic diagram showing changes in the required light amount with respect to the document density detection required light amount L1 and the normal image exposure required light amount L2 preset by the reference light amount setting circuit of this embodiment. .

Generally, image exposure usually requires a high light amount for forming a latent image on the photoconductor 12, but in the case of document density detection, a small signal detected by the light receiving element 103a is detected even with a low light amount. The amplification enables control of the concentration. Therefore, as shown in FIG. 5, by separately setting the document density detection required light amount L1 and the normal image exposure required light amount L2, the light amount required for reading (original density detection required light amount) can be reduced. It will be possible.

[0017]

As described above, according to the present invention,
Since the light amount required for reading the original density is set to be lower than that for normal image exposure, the waiting time can be shortened when copying is performed in the density detection mode, and the use efficiency of the image forming apparatus can be improved. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a copying machine.

FIG. 2 is a configuration block diagram of an embodiment of a control device.

FIG. 3 Characteristic diagram of document density vs. document density detection output

FIG. 4 is a characteristic diagram of document density detection output vs. developing bias voltage.

FIG. 5 is a characteristic diagram of time vs. required light amount according to an embodiment.

[Fig. 6] Time-dependent characteristic curve of exposure light amount depending on ambient temperature

[Explanation of symbols]

 4 Fluorescent Lamp 40 Document Density Detecting Unit 101 Document Reading Device 102 Controller for Each Unit 103 Light Quantity Detecting Unit 104 Reference Light Quantity Setting Circuit 105 Lighting Control Means 106 Document

Claims (1)

[Claims] 1. A fluorescent lamp as an exposure light source, lighting means for lighting the fluorescent lamp, control means for controlling the lighting means, and light quantity detection means for detecting the light quantity of the fluorescent lamp. And a density detecting means for reading the density of the original, and when the density of the original is read by the density detecting means, the amount of light necessary for reading is set to be lower than that during normal image exposure. Image forming apparatus.