JPH0341478A - Image density reader - Google Patents

Abstract

PURPOSE:To simplify a manufacturing process and to shorten time by automatically adjusting a gain based on an output from a sensor receiving light reflected by an original. CONSTITUTION:An exposing lamp 2 is turned off, and digital outputs from the ports A4 to A8 of a CPU 8 are changed over to switch a gain to 16 stages via analog switches 8 to 21 of a gain selecting circuit 16. An output related to each gain, obtained as light reflected by an original, and received by an EE sensor 4, is fetched to the CPU 7 and stored therein as black data from the port A2 with the aid of an arithmetic amplifier 8 and voltage dividing resistances R6 and R7. Similarly, when the lamp 2 is turned on, white data is stored, and the difference between the black and white data on each gain is operated. In the increasing order, arithmetic results are compared with an appropriate, upper gain limit, and the gain corresponding to the first data just below the upper gain limit is automatically set. Offsetting is adjusted in a simi lar manner. Consequently, manual adjustment is not needed any more; therefore the manufacturing process of an image density reader is simplified, and the production time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image density reading device used in a copying machine.

(Background of the Invention) Copying machines are generally equipped with a function that automatically adjusts the developing sleeve bias according to the density of the original to obtain transfer paper with the optimum density.

This automatic adjustment is performed by amplifying the image density signal (hereinafter referred to as FEB signal) obtained from the sensor by BE scanning (an operation in which a light source is moved along the original to obtain density information of the original), and then the CPU (Central Processing Unit) ), create an EE histogram based on this to understand the density distribution of the document, and determine the optimal developing sleeve bias.

Therefore, accurate processing of the BE signal is the basis for obtaining an appropriate bias, and copying machine manufacturers have to adjust the EE of the image density reading device for each device in the production process.
By fine-tuning the amplification factor (gain) and offset of the signal processing circuit, we eliminate variations in reading density caused by sensor accuracy and errors in the resistance values of the resistors that make up the circuit, allowing uniform density reading for the same document. We are making adjustments to make it possible.

FIG. 7 is a circuit diagram of a conventional image density reading device.

This conventional example processes IE signals obtained by EE scanning, and the light from the exposure lamp 2 reflected on the copy surface of the original 1 is transmitted to the EE sensor (
The light receiving element) 4 converts the signal into an EE signal. This EE multiplied signal is amplified by the gain selection circuit 5 and the offset adjustment circuit 6, and converted into a voltage that can be input manually to the analog terminal of the CPU 7.

The gain selection circuit 5 is composed of an operational amplifier 8, a gain adjustment resistor R1, and resistors R2 to R7. A voltage obtained by dividing the power supply (1, OV) by resistors R3 and R4 is input to the non-inverting terminal. Further, a resistor R5 is provided between the output terminal of the operational amplifier 8 and the non-inverting input terminal r.
6 and R7 divide the output signal of the operational amplifier 8, and the voltage dividing point thereof is connected to the M side of the switch SWI. The amplification factor (gain) of this gain selection circuit is R5/R
1+R2 (however, the resistance value of each resistor is assumed to match the reference number), so the gain adjustment resistor R
By manually fine-tuning the resistance value of 1, the amplification factor can be adjusted to
For example, it can be varied within a range of 2 to 10 times.

The offset adjustment circuit 6 includes an operational amplifier 9, a variable resistor RLO for offset adjustment, and resistors R8, R9, R1, and I.
, R1, 2, and R1-3. The output signal of the operational amplifier 8 is input to the inverting terminal of the operational amplifier 9 via the resistor R8, and the power supply (IO
A voltage obtained by dividing V) by a resistor R9, a variable resistor R], 0, and a resistor R11 is input manually. The resistor RI2 is provided between the output end of the operational amplifier 9 and the inverting input terminal, and the resistor R13 is provided between the ground. Further, the offset adjustment resistor RIO is manually adjusted.

The switch 5171 is switched to the P side in the actual operation mode (the mode when actually reading the document density), and to the M side in the adjustment mode.

The monitor device 10 performs a predetermined display corresponding to the input EE multiplied signal level.

The bias circuit 12 receives instructions from the CPU 7 and
An appropriate developing bias is supplied according to the E times signal level. By adjusting the developing bias, the amount of toner 14 that lands on the drum 13 is controlled.

Next, the operation of this conventional example will be explained.

In adjustment mode, in order to make the analog signal (BE multiplied signal) corresponding to the white and black levels obtained from the EE sensor 4 correspond accurately to the power supply level of the CPU 7, the gain adjustment resistor R1 and the offset adjustment resistor RIO are manually adjusted. Adjustments are mainly made by line workers in the production factory.

As mentioned above, this gain adjustment prevents the center of the BE diagram created by the CPU 7 based on the signal from the EE sensor 4 from varying between mass-produced devices due to sensor accuracy, resistance error, etc. It is something we do for the purpose of doing so.

The outline of the adjustment procedure is as follows.

First, the operator opens the back cover of the copy machine and sets the changeover switch SWI to the M side. Next, press the copy button to start a gain adjustment scan, and adjust the resistance value of the resistor R by turning a gain adjustment volume (not shown) so that a predetermined display is obtained while visually observing the monitor device IO.

Next, the changeover switch SWI is set to the P side, and the resistance value of the resistor R1O is adjusted by turning the offset adjustment volume (not shown) while visually observing the monitor device TO.

During actual operation Switch SWI is set to the P side.

Place the original 1 in a predetermined position, press the copy button (not shown), and start EC scanning. The light from the exposure lamp 2 reflected on the document surface is guided to the drum 13 via a reflection mirror and an optical system 3, and is converted into an electric signal by an EE sensor 4, which is then output as an EE multiplied signal. This EC
In scanning, for example, average photometry is performed, and as shown in FIG. 6, the density of the shaded area on the document surface is read. In the figure, L] is 20 mm, L2 is 120 mm, L
3 is 50 mm, and reference number i5 indicates the leading edge of the document.

The BE multiplied signal gain selection circuit 5 and offset adjustment circuit 6 amplify the signal, and the output thereof is inputted to the CPU 7 via the switch Sw1. CPU 7 is a human-powered EE
Based on the double signal, an EE (density) histogram as shown in FIG. 5 is created, and based on this, the bias circuit 12 is instructed to supply a developing bias suitable for the density of the original. If the bias voltage of the developing sleeve 11 is high, the drum 1
3 (=I) The amount of toner 14 deposited decreases and the density becomes lighter, and the lower the density, the darker the density becomes. By adjusting this bias voltage, it is possible to obtain clear and sharp line drawings, whether it is light line drawings, photographic drawings, or dark line drawings. Copying is possible.

(Problems to be Solved by the Invention) In the conventional image density reading device described above, the rear cover must be opened when performing initial adjustment, and adjustment is performed manually while looking at the monitor display. The problem is that the adjustment method is complicated, takes time and effort, and reduces the throughput of the production line.

(Means for Solving the Problems) The image density reading device of the present invention includes a sensor that receives reflected light from a document and outputs an analog signal according to the amount of light, and amplifies the output signal of the sensor. A concentration signal amplification means capable of changing the amplification factor stepwise, and an amplification factor control means that monitors the output level of the concentration signal amplification means and sends a control signal according to the monitoring result to switch the amplification factor. are doing.

(Effect) Both input Ig! Based on the concentration signal, the amplification factor control means automatically sets the optimum amplification factor, eliminating the need for manual adjustment.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of an image density reading device according to the present invention, and in the figure, the same or corresponding parts as in the conventional example are designated by the same reference numerals.

In this embodiment, the gain selection circuit 16 eliminates the manual gain adjustment resistor R1 that was present in the conventional example, and instead uses the output of the CPU 7 to control the four analog switches 18 to 16.
The opening and closing of 21 is controlled, and the resistance R2~
This configuration uses RL7 to create 16 types of combined resistance.

That is, analog switch 18 and resistor R14, analog switch 19 and resistor R (
5, analog switch 20 and resistor R1B.

Analog switch 2t and resistor R17 are connected, and analog switches 18 to 21 are opened and closed by inverters 22 to 25.
It is designed to be controlled by the output of the CPU 7 via the CPU 7. As a result, 16 ways, for example 2.0, 2.53
．． 0. ...The gain can be changed in steps of 0.5 times 9.5 times.

Also, in the offset adjustment circuit 17, an offset adjustment resistor RIO and a resistor R9 for manual adjustment are provided.
R11 is removed and the offset voltage is automatically set.

That is, a voltage follower consisting of an operational amplifier 2G and resistors R1 and B is connected to the analog port A3 of the CPU 7, and its output is connected to the operational amplifier 27. The signal is amplified by an inverting amplifier constituted by resistors RL9 and R20 and a reference voltage source VRI, and is supplied to the non-inverting input terminal of the operational amplifier 9.

Next, the gain and offset adjustment operations of this embodiment will be explained with reference to FIGS. 2 and 3.

Figure 2 is a flowchart showing the automatic gain adjustment procedure, and Figure 3 is a flowchart 1 showing the automatic offset adjustment procedure.
It is.

Automatic gain adjustment operation With exposure lamp 2 turned off, A4 to A of CPU 7
8-port digital output switching, gain selection circuit 16
Switch the gain in 16 steps from maximum to minimum,
The EIE signal (signal obtained by dividing the voltage at the output end of the operational amplifier 8 into two by resistors R6 and R7) at each gain is read from the analog port 1-A2 as black data and stored (
Step 30).

Next, while performing an EE scan with the exposure lamp 2 on, the gain is similarly switched to 16 levels, and the EE multiplied signal white data at each gain is read out from the analog port A2 and stored (step 80). Next, calculate the difference between white data, black data, and 0 for each gain, and store the result (step 32).
).

Next, the exposure lamp 2 is turned off and the optical system is returned to the home position (step 33).

Next, load the stored differences between the own data and the black data for each gain from the memory in descending order of magnitude, compare it with the optimal gain upper limit (0,925V), and store the first data smaller than that as gain width data. and selects a gain (step 34).

Automatic offset adjustment operation Analog voltage output from A3 port from OV to IO
The offset voltage is changed in a range of about 2V to 6V by switching the voltage in 63 steps, and the black data at each offset voltage is read and stored (step 40).

Next, detect the first offset voltage that exceeds a predetermined upper limit value, and select an offset voltage one step lower than this (
Step 4 ().

Automatic adjustment is performed as described above.

Next, the procedure for setting the bias of the developing sleeve 11 will be explained with reference to FIG.

First, using the white data and black data read in each step described above, six types of threshold voltages J2D, J2. J3D, J3. J4. BJ (
(The later the value is, the larger the value becomes.)

Next, execute the bias determination flow. The lightest density is compared with the threshold value BJ (step 50), and if it is determined that the lightest density is greater, the platen is over and bias 4 is outputted (step 51), and when the following is the case, the average density is set to the threshold Compare with the value J2 (step 52), if
Step 53) compared with the threshold value J2D, outputs bias 3.5 or bias 4 depending on the magnitude relationship (
Steps 54.55). When the average density is greater than the threshold J2, the magnitude with respect to the threshold J3D is determined (step 56), and when it is below, the bias 45 is output (step 57).

When it is larger than the threshold J31), it is determined whether it is larger than the threshold J3, and when it is less than that, output bias 5 (step 59), and when it is larger, it is judged whether it is larger or smaller than the threshold J4 (step 59). 60). Average density marlin] 1 If the value is below J4, output bias 6. Step 6
1), if it is large, output bias 7 (step 6
2).

In this embodiment, stepwise gain switching is performed by opening/closing control of an analog switch, so high-speed dynamic gain adjustment can be performed. Furthermore, since the offset adjustment is automated, the effect of time reduction is significant, and as a result of actually applying this embodiment, the time required for adjustment was reduced by more than one minute compared to the conventional method.

(Effects of the Invention) As described above, the present invention has the effect of simplifying the production process and shortening the time by automatically adjusting the gain based on the EE multiplied signal.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an embodiment of the image density reading device of the present invention, Fig. 2 is a flowchart showing an automatic gain adjustment procedure, 2 Fig. 3 is a flowchart showing an automatic offset adjustment procedure, and Fig. 4 is a flowchart showing an automatic offset adjustment procedure. Flowchart 1 showing the developing sleeve bias setting procedure, Figure 5 is a diagram showing an example of the read image density histogram, Figure 6 is a diagram showing the document density reading range during EE scan, and Figure 7 is the conventional example. It is a circuit diagram. 1... Original 2... Exposure lamp 3...
Optical system 4...EE all sensors 7...CPU8.9
...Operational amplifier 11.Developing sleeve 12..Bias circuit 13..Drum 14..Toner
15... Edge of document 16... Gain selection circuit 17... Offset adjustment circuit 18-2 (... Analog switch 22-25... Inverter 28, 27... Operational amplifier R2-R20 ・Resistance

Claims (1)

[Claims] A sensor that receives reflected light from a document and outputs an analog signal according to the amount of light, and a density signal amplification device that can amplify the output signal of the sensor and change the amplification factor in stages. and amplification factor control means for monitoring the output level of the density signal amplifying means and for switching the amplification factor by sending out a control signal according to the monitoring result.