JPH057696B2 - - Google Patents

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 above-mentioned pre-scan type has a configuration in which the document is exposed to light before performing an 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 original while performing the image forming operation and set the optimum power applied to the light source for the density of the original at each point in time.

In either method, it is necessary to initialize the received light amount-appropriate exposure amount characteristics for automatic exposure.
Performing manual operation.

To explain in more detail, the above-mentioned manual operation involves visually checking the density of the copy by copying the newspaper and the standard original for setting one sheet at a time, and manually adjusting the density of the copy to an appropriate value. Adjustments are being made.

<Problems to be Solved by the Invention> In any of the above-mentioned automatic exposure devices, in order to perform initial settings, it is necessary to copy newspapers and standard originals for settings one by one, and the density of the resulting copies. It is necessary to adjust the exposure amount based on the above information, and it is necessary to repeat the above operation many times. There is a problem that not only the work becomes complicated, but also the required time becomes long.

<Object of the Invention> The present invention has been made in view of the above-mentioned problems, and is an automatic exposure method that can simplify the work for initially setting the received light amount-appropriate exposure amount characteristic for automatic exposure. The purpose is to provide equipment.

<Means for Solving the Problems> In order to achieve the above object, the automatic exposure apparatus of the present invention can process two types of standard originals with different densities.
A received light amount acquisition means that exposes each document with a preset suitable exposure amount and obtains the received light amount, and a received light amount - appropriate exposure based on the two sets of received light amount and appropriate exposure amount obtained by the received light amount acquisition means. A calculating means for generating quantity characteristics, and light reception obtained by exposing an actual copy document to a temporary exposure amount that is within the appropriate exposure amount range preset for the two types of standard documents with different densities. The amount of light received and the amount of light received corresponding to the provisional exposure amount determined from the above-mentioned received light amount-appropriate exposure amount characteristic, and based on this comparison, the amount of exposure that should be applied to the actual copy original. and an exposure amount calculation means for calculating.

However, the above two types of originals are preferably newspapers and standard setting originals, and the calculation means may be one that generates a linear received light amount-appropriate exposure amount characteristic. .

<Function> With the automatic exposure device configured as described above, the exposure amount is changed based on the density of the original to obtain a copy with an appropriate density. The received light amount and the appropriate exposure amount corresponding to the original are obtained, and the received light amount-appropriate exposure amount characteristic is generated by the calculation means based on the two received light amounts obtained by the received light amount acquisition means and the appropriate exposure amount. , perform initial settings for automatic exposure, and then automatically select the appropriate exposure amount corresponding to the density of the original based on the above-mentioned received light amount-appropriate exposure amount characteristic to obtain copies with appropriate density. can.

In addition, when the above two types of originals are a newspaper and a standard original for settings, based on the two originals with considerably different densities, a received light amount-appropriate exposure amount characteristic that approximates the desired received light amount-appropriate exposure amount characteristic is determined. can be generated.

Furthermore, when the calculation means generates a linear received light amount-appropriate exposure amount characteristic, 2
The received light amount-appropriate exposure amount characteristic can be generated based only on the received light amount and the appropriate exposure amount for each type of document.

<Examples> Hereinafter, examples 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 is used to expose an original D set on the upper surface of an original platen 1 which is movable back and forth.
, 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 placed at a predetermined position below the document table 1.
have.

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, ROM via an A/D converter (not shown) and an input interface.
A control signal outputted from the microcomputer 6 is also supplied to an exposure lamp lighting circuit 7 via an output interface (not shown) and a D/A converter.

1 and 2 are flowcharts for explaining the operation of the automatic exposure apparatus, with FIG. 1 showing the initial setting operation and FIG. 2 showing the automatic exposure apparatus.

First, to explain the initial setting operation, a standard document for setting (hereinafter abbreviated as NTC) is set in step, and after waiting until the print key is turned ON, movement of document glass 1 is started in step; , the exposure lamp S is turned on so that the exposure amount reaches the intermediate value EXP5 (see Figure 3) of the allowable range, and in step, the document leading edge timing switch (not shown), which also serves as the timing for conveying the copy paper, is turned on. After waiting for a predetermined time in step, the reflected light from the leading edge of the document is sampled (required time is about several milliseconds), that is,
In a normal manuscript, the leading edge is the background, so
The shading of the background is detected, and in a step, the average value of the sampled received light amount (see FIG. 3) is calculated and stored in the memory. Next, in step, the exposure amount of the exposure lamp S is set to the lower limit value EXP4.
(See Figure 3), wait until the exposure amount of the exposure lamp S stabilizes in the step, and then perform the step for a fairly long time (the required time is several seconds).
The reflected light is sampled over a period of about 10 msec), and in a step, the average value of the sampled received light amount (see Fig. 3) is calculated and stored in the memory.

Thereafter, in step 1, the document table 1 is returned to the home position, a newspaper or a standard document for newspapers is set, and the same discrimination and processing as in the above steps is performed. However, the average value (see Figure 3) is calculated based on the amount of received light sampled at the exposure amount EXP5, and the average value is calculated by sampling at the upper limit EXP6 (see Figure 3) instead of sampling at the lower limit EXP4. The difference is that the value (see Figure 3) is calculated.

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 It is possible to obtain the average value of the amount of received light corresponding to the upper limit value and the intermediate value of the amount of light.

Next, automatic exposure operation will be explained.

In the step, set the exposure amount to the intermediate value EXP5, wait until the document leading edge timing switch is turned ON in the step, wait for a predetermined time in the step, and detect the reflected light from the leading edge of the document for a short time (about a few milliseconds) in the step. is sampled, and the average value of the sampled received light amount is calculated in step. Then, in a step, the intermediate value between the average value and the average value is calculated, and in the step, the magnitude relationship between the average value and the intermediate value is determined, and if the average value is larger, the exposure amount is set to the lower limit in the step. Set the value EXP4, and if the average value is smaller, set the exposure amount to the upper limit value in the step.
Set to EXP6. After processing any of the above steps, the step waits for a predetermined time until the exposure stabilizes, and the step samples the reflected light from the document for a predetermined time and calculates the average value. In this step, a ratio A of the difference between the current exposure value and the lower limit value EXP4 to the difference between the upper limit value EXP6 and the lower limit value EXP4 is calculated. After that, in a step, the appropriate amount of received light B corresponding to the current exposure value is calculated (specifically, it is obtained by calculating B=A{-}+), and in the step, the above average value and the appropriate amount of received light are calculated. A determination reference value C is calculated by dividing the difference from B by a predetermined value n determined by the copying machine, and it is determined in step whether or not the determination reference value C is positive.

If the judgment reference value C is determined to be positive in the above step, that is, if it is judged that the document is pale, then in the step it is determined whether or not the judgment reference value C is 1 or more. If it is determined that this is the above, then in step, a value D obtained by dividing the determination reference value C from the current exposure value is set as the appropriate exposure value, and in step, it is determined whether or not the value D is smaller than the lower limit value EXP4. and,
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 26, and it is determined in step 26 whether or not the exposure has ended. If it is determined in step 26 that the exposure has been completed, the exposure lamp S is turned off in step 27, and conversely, if it is determined that the exposure has not been completed, the process continues in the following steps. By doing this, the automatic exposure operation is continued.

In addition, if it is determined in the above step that the determination reference value C is less than 1, in order to prevent flickering of the copy, the determination and processing in step 26 and below are performed without changing the exposure value. If it is determined in step that the exposure value is equal to or higher than the lower limit value EXP4, the determination and processing in step 26 and subsequent steps are performed based on the exposure value obtained in step.

Furthermore, if the judgment reference value C is determined to be negative in the above step, the judgment reference value C is converted to a positive value C' in the step, and the step
21, determine whether the value C′ is greater than or equal to 1,
If it is determined that the current exposure value is 1 or more, it is determined in step 22 whether or not the current exposure value is larger than the lower limit value EXP4. If it is determined that the current exposure value is larger than the lower limit value EXP4, the current exposure value The value D obtained by adding the value C' to the exposure value is set as the appropriate exposure value, and in step 24, the above value D is set as the upper limit value EXP.
It is determined whether the value is greater than 6 or not. And the upper limit
If it is determined that the exposure value is larger than EXP6, the upper limit value EXP6 is set as the appropriate exposure value in step 25, and the determination and processing in step 26 and subsequent steps are performed.

If the value C' is determined to be less than 1 in step 21, the determination and processing in step 26 and below are performed without changing the exposure value in order to prevent flickering of the copy. Even if it is determined in step 22 that the lower limit EXP is less than 4, the process continues to the determination in step 26 or less.
The upper limit value is set in step 24 above.
If it is determined that the EXP is 6 or more, the determination and processing in steps 26 and below are performed based on the exposure value obtained in step 23.

In summary, 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,
By performing simple arithmetic operations and determining magnitude relationships, it is possible to obtain the appropriate exposure amount and obtain copies with appropriate density. In addition, once the appropriate exposure amount is set to the lower limit value EXP4, 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. Never.

It should be noted that the present invention is not limited to the above-mentioned embodiment; for example, in the embodiment shown in FIG. By installing a dedicated switch for detecting the timing of receiving reflected light from a document, it is possible to omit the steps in FIG. 1 and FIG. 2. Various design changes can be made within the same range.

<Effects of the invention> As described above, this invention provides two
By exposing each type of original once, the exposure value and the light reception value from the original are obtained. By obtaining these various types, initial settings for automatic exposure are completed, and when performing automatic exposure operation, each of the above values is obtained. This has the unique effect of being able to obtain an appropriate exposure value based on the original density based on the original density, and thereby significantly shortening the time required for initial setting for automatic exposure.

[Brief explanation of the drawing]

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 flowchart explaining the initial setting operation and automatic exposure operation. FIG. 4 is a block diagram showing the electrical configuration of an embodiment of the automatic exposure apparatus, and FIG. 5 is a schematic diagram showing the main parts of the automatic exposure copying machine. 5... Optical sensor, 6... Microcomputer, 7... Exposure lamp lighting circuit, S... Exposure lamp.

Claims (1)

[Claims] 1. Two types of standard originals with different densities are exposed at an appropriate exposure amount set in advance for each original,
a received light amount acquisition means for obtaining the received light amount; a calculation means for generating a received light amount-appropriate exposure amount characteristic based on the two sets of received light amount and appropriate exposure amount obtained by the received light amount acquisition means; The amount of light received was obtained by exposing the two types of standard originals with different densities at a provisional exposure amount that is within the preset appropriate exposure amount range, and the amount of received light obtained from the above-mentioned received light amount-appropriate exposure amount characteristic. , an exposure amount calculation means for comparing the received light amount with the corresponding provisional exposure amount and calculating the exposure amount to be applied to the actual copy document based on this comparison. Features automatic exposure equipment. 2. The exposure amount calculation means calculates the amount of received light obtained by exposing the actual copy original with a provisional exposure amount, and the amount of received light corresponding to the provisional exposure amount obtained from the above-mentioned received light amount-appropriate exposure amount characteristic. Take the difference between, and for this difference,
A correction process is performed according to the sensitivity of the photoreceptor built into the image forming device, and the above-mentioned provisional exposure amount is increased or decreased based on the corrected result to determine the exposure that should be applied to the actual copy document. 2. An automatic exposure apparatus according to claim 1, wherein the automatic exposure apparatus is an automatic exposure apparatus according to claim 1. 3 limit value setting means for setting the upper and lower limits of the exposure amount; determining means for determining whether the exposure amount calculated by the exposure amount calculation means exceeds the limit value; 2. The automatic exposure apparatus according to claim 1, further comprising setting means for setting an exceeded limit value as the exposure amount in response to a discrimination signal from the discrimination means indicating that the exposure amount has exceeded the limit value. 4. The automatic exposure apparatus according to claim 1, wherein the two types of standard documents are a newspaper and a standard document for setting. 5. Claim 1 above, wherein the calculation means generates a linear received light amount-appropriate exposure amount characteristic.
Automatic exposure device as described in section.