JPS6358432A - Automatic exposing device - Google Patents

Abstract

PURPOSE:To prevent a white omission by setting the upper limit value and the lower limit value of exposure values allowed to be changed according to the density of an original, and selecting the limit value of exceeded side as a proper exposure value when an exposure value exceeding the limit values is calculated. CONSTITUTION:When the amount of exposure is changed based on the density of the original to obtain the copy of proper density, the upper limit value and lower limit value of the amount of exposure are set beforehand, calculate the amount of exposure to be changed based on the original density obtained by exposing the original, and the calculated amount of exposure discriminates whether it exceeds the limit values or not. When the amount of exposure does not exceed the limit values, the copy of proper density is obtained by exposing the original based on calculated amount of exposure. When the amount of exposure exceeds limit values, the limit value of exceeded side is set as the amount of exposure, and the original is exposed based on the set amount of exposure. Thus, the white omission can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an automatic exposure apparatus, and more particularly, to an automatic exposure apparatus that controls the output light intensity of a light source in accordance with the density of a document.

<Prior Art> Conventionally, automatic exposure apparatuses have been provided in a pre-scan type and a real-time type.

The pre-scan method described above has a configuration in which the document is exposed to light before performing the image forming operation, and the optimum power applied to the light source is set for the portion with the lightest density.

Further, the real-time method is configured to read the density of the document while performing the image forming operation and set the optimum light source application force for the density of the document at each point in time.

<Problems to be Solved by the Invention> In the above-mentioned pre-scan type automatic exposure device, it is necessary to expose the document before performing the image forming operation.
There is a problem in that it takes a long time to perform the first image formation on each document.

In addition, in the above-mentioned real-time automatic exposure device -C
Since the power applied to the light source is changed in accordance with the density of the original at each exposure point, if there is a solid black area in the density reading area of the original, white spots will occur on both sides of the solid black area, and normal There is a problem in that image formation corresponding to character information, etc., is no longer performed.

<Object of the invention> This invention was made in view of the above problems,
It is an object of the present invention to provide an automatic exposure device that can shorten the time until the first image formation is performed on one document and can reliably prevent the occurrence of white spots.

Means for Solving the Problems> In order to achieve the above object, an automatic exposure apparatus of the present invention includes a limit value setting means for setting an upper limit value and a lower limit value of the exposure amount, and a limit value setting means for setting an upper limit value and a lower limit value of the exposure amount, and a an exposure amount calculation means for calculating the exposure amount to be changed; a determining means for determining whether the exposure amount calculated by the exposure amount calculation means exceeds a limit value; and an indication means for indicating that the exposure amount exceeds the limit value. It has a setting means which receives the discrimination signal from the discrimination means and sets the exceeding limit value as the exposure amount.

However, it is preferable that the upper limit and lower limit of the exposure amount be values corresponding to a newspaper and a standard document for setting, respectively.

With the automatic exposure device having the above configuration, when changing the exposure amount based on the density of the original and obtaining a copy with an appropriate density, the upper limit value and lower limit value of the exposure amount can be set in advance by the limit value setting means. is set, the exposure amount to be changed is calculated by the exposure amount calculation means based on the original density obtained by exposing the original, and the exposure amount calculated by the exposure amount calculation means is the limit value. A determining means determines whether or not the value exceeds the maximum value.

Then, when the exposure amount does not exceed the limit value, by exposing the original document based on the calculated exposure amount, a copy with an appropriate density can be obtained.

On the other hand, when the exposure amount exceeds the limit value, the setting means sets the exceeding limit value as the exposure amount, and the document is exposed based on the set exposure amount. It is possible to obtain a copy without white areas etc.

In addition, if the upper and lower limits of the exposure amount above correspond to newspapers and standard manuscripts for settings, respectively,
Even if the manuscript has solid black parts, newspaper, etc.
By performing exposure at an exposure amount corresponding to the standard document for setting, it is possible to prevent white spots and the like from occurring.

Furthermore, since the present invention can be incorporated into a real-time automatic exposure device without any inconvenience, a copy can be obtained by exposing the document once with a light source.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

FIG. 5 is a schematic diagram showing an embodiment of the automatic exposure apparatus of the present invention, in which an exposure lamp (S) for exposing an original (D) set on the old market of the reciprocally movable original platen (1); , a slit [2] that guides reflected light from the document (D) to the photosensitive drum (4), and a lens (3). A light receiving sensor (5) is provided at a predetermined position below the document table (1).

FIG. 4 is a block diagram showing the electrical configuration of the automatic exposure apparatus, in which the reflected light amount detection signal from the light receiving sensor (5) is sent to the CPU, RAM, and ROM via an A/D converter (not shown) and an input interface. The control signal output from the microcomputer (6) is supplied to the exposure lamp lighting circuit ('7) via an output interface (not shown) and a D/A converter. supplying.

1 and 2 are flowcharts explaining the operation of the automatic exposure device, and FIG. 1 shows the initial setting operation and the second
The figures each show an automatic exposure operation.

First, to explain the initial setting operation, set the standard document for setting (hereinafter abbreviated as NTC) in step ■, wait until the print key is turned ON, and then start moving the document table (1) in step ■. , In step (2), the exposure lamp (S) is turned on so that the exposure amount reaches the intermediate value EXP5 (see Fig. 3), and
In step ■, wait until the document leading edge timing switch (not shown in the figure), which also serves as the timing for transporting the copy paper, is turned on, wait for a predetermined time in step ■, and sample the reflected light from the leading edge of the document in step ■. In other words, in a normal document, the leading edge is the background, so the shading of the background is detected, and in step
I) (see Figure 3) is calculated and stored in memory. Next, in step (2), the exposure amount of the exposure lamp (S) is set to the lower limit value EXP4 (for example, the appropriate exposure value corresponding to NTC, see FIG. 3), and in step (2), the exposure amount of the exposure lamp (S) is
After waiting until the exposure amount of S) becomes stable, step [phase]
In step 2, the reflected light is sampled over a fairly long period of time (the required time is about several 10 m5 ec), and in step 2, the average value (2) of the amount of sampled received light (see FIG. 3) is calculated and stored in the memory.

Thereafter, in step @, the original table (1) is returned to the home position, a newspaper or a standard original for newspapers is set, and the same determination and processing as in steps (2) to (0) are performed.

However, the average value 0[) (see Figure 3) is calculated based on the amount of received light sampled at exposure gEXP5, and instead of sampling at the lower limit EXP4, the upper limit EXP6 (newspaper or standard newspaper manuscript) is calculated. (see Figure 3), and average value [V
) (see Figure 3).

Therefore, by performing the above series of operations, it is possible to obtain the average value of the received light amount corresponding to the lower limit and the intermediate value of the exposure amount for NTC, and also to obtain the average value of the amount of light received corresponding to the lower limit value of the exposure amount for NTC and the intermediate value, and also to obtain the average value of the amount of light received corresponding to the lower limit value of the exposure amount for NTC and the intermediate value, and also The average value of the amount of received light corresponding to the upper limit value and the intermediate value can be obtained.

Next, automatic exposure operation will be explained.

In step ■, set the exposure amount to the intermediate value EXP5,
In step ■, the document leading edge timing switch is turned on.
After waiting for a predetermined time in step (2), the reflected light from the leading edge of the document is sampled for a short time (about several 15 ec) in step (2), and the average value M of the sampled received light amount is calculated in step (2). . Then, in step ■, the intermediate value ■ between the average value (1) and the average value circle is calculated, and in step ■, the magnitude relationship between the average value M and the intermediate value plane is determined, and the average value M is larger. In this case, the exposure amount is set to the lower limit value EXP4 in step
, and if the average value M is smaller, step ■
The exposure amount is set to the upper limit value EXP6. After performing any of the above steps, wait for the predetermined opening time until the exposure stabilizes in step [stock].
In step 0, the reflected light from the original is sampled for a predetermined period of time to calculate the average value ■, and in step 0, the difference between the current exposure value and the lower limit value EXP4, the difference between the upper limit value EXP6 and the lower limit value EXP4 is calculated. Calculate the ratio A. After that, in step (2), the appropriate amount of received light B corresponding to the current exposure value is calculated. Specifically, B-A (
(IVI - (IF)) + (I)), by dividing the difference between the above average value - and the appropriate amount of received light B by a predetermined value n determined by the copying machine in step (3). , calculate the judgment reference value C, and proceed to step ■
It is determined whether the determination reference value C is positive or not.

If the judgment reference value C is determined to be positive in the above step If it is determined that the value is 1 or more, the value obtained by dividing the judgment reference value C from the above-mentioned current exposure value is set as the appropriate exposure value in step (2), and in step (2) it is determined whether the above value is smaller than the lower limit value EXP4. Determine whether or not. If it is determined that the exposure value is smaller than the lower limit value EXP4, the lower limit value EXP4 is set as the appropriate exposure value in step (3), and it is determined in step [phase] whether or not the exposure has ended. If it is determined in step [phase] that the exposure has been completed, the exposure lamp (S) is turned off in step O, and conversely, if it is determined that the exposure has not been completed, the step O is continued as is. The automatic exposure operation is continued by performing the following determination and processing.

In addition, if it is determined that the determination reference value C is less than 1 in the above step [phase], step [phase] is performed without changing the exposure value in order to prevent flickering of the copy.
If the lower limit value EXP is determined to be equal to or higher than the lower limit EXP4 in the above step (2), step [3] is performed based on the exposure value obtained in step (2).
Phase] The following judgments and processing are performed.

Furthermore, if the judgment reference value C is determined to be negative in the above step (■), the judgment reference value C is converted into a positive value C' in the step [phase], and the value C is determined in the step (■).
'' is greater than or equal to 1. If it is determined to be greater than or equal to 1, in step (2) it is determined whether or not the current exposure value is greater than the lower limit value EXP4, and the lower limit value EXP4 is determined.
If it is determined that the exposure value is larger than that, the value obtained by adding the value C to the current exposure value is set as the appropriate exposure value in step 0, and it is determined in step 2 whether or not the above value is greater than the upper limit value EXP6. do. If it is determined that the exposure value is larger than the upper limit value EXP6, the upper limit value EXP6 is set as the appropriate exposure value in step 2, and the upper limit value EXP6 is set as the appropriate exposure value in step [
Phase] The following judgments and processing are performed.

In addition, if the value C' is determined to be less than 1 in step (3) above, in order to prevent flickering of the copy, the determination and processing in step [phase] and below are performed without changing the exposure value. , Even if it is determined that the lower limit value EXP is equal to or less than 4 in the above step [phase], the determination and processing below the step [phase] is performed as is, and if it is determined that the upper limit value EXP is equal to or greater than 6 in the above step [phase]. In this case, the determination and processing in step [phase] and subsequent steps are performed based on the exposure value obtained in step 0.

To summarize the above, four simple arithmetic operations and determination of size relationships are performed based on the initial setting values obtained in the flowchart of Fig. 1 and the amount of received light obtained by actually exposing the original. Accordingly, it is possible to obtain an appropriate amount of exposure and obtain a copy with an appropriate density. In addition, if the appropriate exposure amount is set to the lower limit value EXP4 -1, it continues to be held at the lower limit value EXP4, so even if a solid black part is detected midway through, the image quality will deteriorate at the periphery of the solid black part. There's nothing to do.

Note that the present invention is not limited to the above-mentioned embodiment. For example, in the embodiment shown in FIG. 2, it is possible to calculate the value obtained by adding the temperature correction value in step (■) as the determination reference value C. In addition, by installing a dedicated switch for detecting the timing of receiving reflected light from a document, it is possible to omit step 1 in FIG. 1 and step 2 in FIG. Various design changes can be made without changing the gist of the invention.

<Effects of the Invention> As described above, the present invention sets the upper and lower limits of the exposure value to be changed in accordance with the density of the original, and automatically changes the exposure value when the exposure value exceeds the limit value. The side limit value is selected as the appropriate exposure value, so even when exposing a document with partial black solid areas, high-quality copies can be obtained without white areas etc. It has the unique effect of being able to In particular, since the present invention can be applied to a real-time type automatic exposure apparatus, it also has the unique effect of shortening the time required to obtain the first copy.

[Brief explanation of drawings]

Fig. 1 is a flowchart explaining the initial setting operation of the automatic exposure device, Fig. 2 is a flowchart explaining the automatic exposure operation, and Fig. 3 is a received light amount-appropriate exposure amount characteristic explaining the initial setting operation and automatic exposure operation. FIG. 4 is a block diagram showing the electrical configuration of an embodiment of an automatic exposure apparatus, and FIG. 5 is a schematic diagram showing the main parts of an automatic exposure copying machine.

Claims (1)

[Claims] 1. Limit value setting means for setting an upper limit value and a lower limit value of the exposure amount in an automatic exposure device that changes the exposure amount based on the density of the original to obtain a copy with an appropriate density. an exposure amount calculation means for calculating an exposure amount to be changed based on the original density; and a determination means for determining whether the exposure amount calculated by the exposure amount calculation means exceeds a limit value;
1. An automatic exposure apparatus comprising: a setting means that receives a discrimination signal from a discrimination means indicating that a limit value has been exceeded and sets the exceeded limit value as an exposure amount. 2. The automatic exposure apparatus according to claim 1, wherein the upper limit and lower limit of the exposure amount are values corresponding to a newspaper and a standard document for setting, respectively.