JPS597943A - Method and device for automatic printing level detection of diazo copying machine - Google Patents

Abstract

PURPOSE:To perform automatic printing in diazo copying whose density is uniformed for vaiours originals by setting the interval of detection points for the light transmittivity of an original on the basis of the rate of variation in photosensitive paper printing sensitivity with the light transmittivity of the original. CONSTITUTION:When the front end of the original moves to between an optical fiber 14 and a photosensor 16, an original light transmission detecting circuit 40 detects the light transmittivity of the original. The circuit 40 consists of the photosensor 16, a transistor (TR) 42 for amplification, and N sets of comparators C1-CN, etc. The rate of variation in printing speed is high at a low- transmittivity part of the original, so the detection point interval is narrowed down; when the transmittivity increases, the detection interval is widened. The output signal of the circuit 40 regarding optimum original light transmittivity is passed through an A/D converting and holding circuit 54 and then respective circuits 56, 62, and 66, and the signal is inputted to a driving motor speed control circuit 70, which controls a driving motor 28 to control the printing speed of photosensitive paper, performing the automatic printing in diazo copying whose density is made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic printing 44 level detection method and apparatus for a diazo copying machine.

Diazo copiers having automatic printing control functions as well as manual printing functions have been known for some time. As is well known, automatic printing control detects the light transmittance of the blank area of the original and adjusts the printing speed (the transport speed of the original and photosensitive paper) or the light source of the copying machine. It controls the amount of light and automatically performs printing control corresponding to the original.

By the way, the copy density (finish density) for various originals
In order to make the image uniform, it is necessary to determine the relationship between the light transmittance of the original and the photosensitive paper printing time (photosensitive paper light irradiation time) (in the case of a method that controls the printing speed), or the relationship between the light transmittance of the original and the amount of light source light. There is a need for an automatic printing control method or device that fully takes into consideration (in the case of a system that controls the light intensity of the light source).

However, in conventional diazo copying machines, the above-mentioned consideration is not sufficient, and therefore, depending on the original, the copy density may not be appropriate. Therefore, if a high-quality copy cannot be obtained with automatic printing control, it is wasteful to switch to manual operation and then carefully set the printing time or the amount of light from the light source and redo the copy. Furthermore, even if this copying is repeated, it is often the case that the optimum copy density cannot be obtained in the first copying operation, resulting in a waste of photosensitive paper and time.

Therefore, an object of the present invention is to improve the rate of change in photosensitive paper printing sensitivity (burning speed or light source light intensity) with respect to changes in the light transmittance of the document in a diazo copying machine that detects the light transmittance of the document and performs automatic printing control. An object of the present invention is to provide an automatic printing level detection method and device for a diazo copying machine that can make the copy density (finish density) uniform for various originals by setting the interval of light transmittance detection points of the original based on the above. be.

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings. In this embodiment, a method of automatically performing printing by controlling the printing speed will be described as an example, or the present invention can of course be applied to a method of controlling the amount of light from a light source.

FIG. 1 is a diagram showing parts of a general diazo copying machine related to the present invention, FIG. 2 is a circuit diagram for explaining the present invention in detail, and FIG. 3 is a diagram for explaining the present invention. It shows the relationship between the light transmittance of the original and the printing sensitivity of the photosensitive paper (printing speed in this embodiment). In FIG. 1, 10 is a light source for exposure, and 12 is a rotating cylinder crow (baked glass) having a light source lO inside. As is well known, the conveyor belt rotates in contact with the cylinder glass 12, and the stacked original and photosensitive paper are conveyed along the outer surface of the cylinder glass 12 by the conveyor belt, during which time the photosensitive paper is exposed. will be held. One end of the optical fiber 14 serving as a light guiding means is provided outside or inside the cylinder glass 12 to take in the light from the light source 10, and the other end is provided on the photosensor 16 side. Reference numeral 18 denotes a document feed roller, 20 a document insertion detection sensor such as a microswitch or a photo sensor, 24 a photosensitive paper feed roller, 26 a printing section conveyance roller, 28 a driving motor of the copying machine, and 30 a part of a printing belt.

Next, the present invention will be explained in detail with reference to FIGS. 1 to 3. When the power switch of the copying machine is turned on, the light source 10 lights up and the drive motor 28 starts rotating at a predetermined speed.

When the light source reaches a steady state, when the original is inserted into the original insertion slot of the copying machine, the original insertion detection sensor 20 detects that the original has been inserted and outputs an insertion detection signal, and the original introduction roller 18 Transport the original into the copier.

When the leading edge of the document reaches between the optical fiber 14 and the photosensor 16, the document light transmittance detection circuit 40 detects the light transmittance of the "base" portion of the document.

The original light transmittance detection circuit 40 includes, in addition to the photosensor 16,
Amplifying transistor 42, N (arbitrary integer) comparators C1-CN, resistors RIA and RIB that apply a reference voltage to the inverting input terminal of comparator C1 (the connection point is PL),
A resistor R that applies a reference voltage to the inverting input terminal of the comparator C2
2A, R2B (connection point is P2), , , , ,
, resistors R(N-1)A and R(N-1)B that apply a reference voltage to the inverting input terminal of the comparator C(N-1) (the connection point is P(N-1)), Resistors RNA and RNB apply the reference voltage to the inverting input terminal of the comparator CN (the connection point is
), a resistor 50 provided between the photosensor 16 and the base of the transistor 42, a resistor 52 provided between the collector of the transistor 42 and ground, and the output terminals of the comparators Cl-CN and the positive voltage source 1B. It has a resistor (no reference number) etc. connected between the two.

When light transmitted through the document conveyed between one end of the optical fiber 14 and the photosensor 16 reaches the photosensor 16, and a voltage proportional to the amount of light that has reached appears at the collector of the transistor 42, this collector voltage is applied to the comparator Cl- applied to each non-inverting input of CN. Each of the comparators C1-CN compares the voltages applied to the inverting and non-inverting input terminals, and if the voltage applied to the non-inverting input terminal is higher than the reference voltage applied to the inverting input terminal, F Outputs a "high" level signal. In other words, the output changes depending on the light transmittance of the original.
The number of comparators (CI to CN) that have a high J level is determined.

By the way, as mentioned above, in order to make the copy density uniform for various originals, the light transmittance of the original and the printing sensitivity of the photosensitive paper (i.e., the printing speed of the photosensitive paper in the case of this embodiment) are required. It is necessary to fully consider the correlation between In this embodiment, the light transmittance of the original corresponds to the collector voltage of the transistor 42 (ie, the output of the comparators 01 to CN), and the photosensitive paper printing sensitivity is related to the rotational speed of the motor 28. According to the experimental results, the relationship between the light transmittance of the original and the printing sensitivity of the photosensitive paper is
As shown in the figure, the slope is not straight, but steep in areas where the light transmittance of the document is low, and becomes gentler as the light transmittance of the document increases. That is, in areas of the document with low light transmission.

The rate of change in the photosensitive paper printing sensitivity with respect to a change in the light transmittance of the original is large, and the rate of change in the photosensitive paper printing sensitivity with respect to a change in the light transmittance of the document is small in portions of the document where the light transmittance is high.

Therefore, if the values of the reference voltages applied to the inverting input terminals of the comparators 01 to CN are set at equal intervals as in the past, it is not possible to finely control the printing sensitivity of the original in parts of the original where the light transmittance is low. There is a problem. On the other hand, if the number of comparators is increased in order to solve this problem, there is a problem that the number of circuit elements increases and control becomes complicated.

Therefore, in the present invention, as shown in FIG. 3, the light transmittance detection point (Di-
The interval (indicated by DN) is narrowed, and the interval is widened as the light transmittance of the original increases. The light transmittance detection points may be set, for example, so that the intervals of the photosensitive paper printing sensitivity (vertical axis) are equal. That is, the connection point P in FIG.
Each voltage dividing resistor circuit (RIA-RIB-R) determines the reference voltage generated in l to PN (document transparency detection circuit 40).
Appropriately select the resistance value of NA/RNB) and connect the connection point Pi-
The reference voltages generated at PN may be made to correspond to the light transmittance detection points Di-DN, respectively, for example. By doing this, the detection points are made denser in areas where the rate of change in photosensitive paper printing sensitivity relative to changes in light transmittance of the original is large, and are made coarser in areas where the change -16 is small.
It is possible to efficiently detect the light transmittance of a document with a small number of comparators.

Now, the analog signal output from the comparator Cl-CN (the value of the analog signal is how many F
is applied to the next stage analog/digital (A/D) converter and holding circuit (hereinafter simply referred to as the conversion/holding circuit) 54. A conversion/holding circuit 54tt receives an analog signal from the original light transmittance detection circuit 40, converts it into a corresponding digital signal, and holds the digital signal corresponding to the optimum thickness f/light transmittance. Here, the digital signal corresponding to the optimum original light transmittance is the signal at the lowest -L position among the outputs of the comparators C1-CN (i.e.,
Highest light transmittance of the original 1. This is a digital 4f number corresponding to the signal output corresponding to the % part number. A digital signal t corresponding to the optimum thickness f and light transmittance held in the conversion holding circuit 54 is applied to the encoder 56, and the encoder 561 outputs a signal corresponding to the input signal number.

On the other hand, a signal output from the document insertion detection sensor 20 in response to the insertion of the document is applied to the document detection circuit 58, and the document detection circuit 58 detects that the document has been inserted. The output signal of the document detection circuit 58 is applied to a timing circuit 60, and the timing circuit 60 applies a control signal to the latch circuit 62 after a predetermined period of time has elapsed. The predetermined period of time refers to the period of time after the insertion of a document into the copying machine is detected until just before the drive motor 28 is controlled. The latch circuit 62 receiving the control signal from the timing circuit 60 latches the output signal of the encoder 56 and outputs the latched signal to a D/A (digital/analog) conversion circuit 66. The D/A conversion circuit 66 converts the digital signal from the latch circuit 62 into an analog signal and applies it to the drive motor speed control circuit 70. This control circuit 70 controls the rotational speed of the motor 28 based on the applied analog signal and performs automatic burning.

In the above description, automatic printing control is performed by controlling the rotational speed of the motor, but the present invention is not limited to this, and as described above, the present invention can also be applied to a method of controlling the amount of light from the light source 10. be able to. Furthermore, in this embodiment, the optical fiber 14 is used to guide the light from the light source 1O to measure the light transmittance of the document, or the optical fiber 14 is not used to guide the light from the light source 10, or other suitable light emitters such as light emitters or light emitting diodes are used instead of using the optical fiber. may be used.

As described above, according to the present invention, the interval between the light transmittance detection points of the document is set based on the rate of change in the photosensitive paper printing sensitivity with respect to the change in the light transmittance of the document. This has the effect of making the copy density (filling moisture) uniform for the original.

[Brief explanation of the drawing]

Fig. 1 is a simple diagram of a diazo copying machine for explaining the present invention, Fig. 2 is a circuit diagram showing an example of a control circuit used in the present invention, and Fig. 3 is a photosensitive paper printing sensitivity with respect to light transmittance of an original. FIG. 40: Original light transmittance detection circuit C1-CN: Comparator Pi-PN: Circuit element connection point (reference voltage 54: A/
D converter and holding circuit patent applicant Copia Co., Ltd. agent Patent attorney Examiner Toshiaki No. 1-4

Claims (2)

[Claims] (1) In a diazo copying machine that detects the light transmittance of the original and performs automatic printing control, the interval between the light transmittance detection points of the original is determined based on the rate of change in photosensitive paper printing sensitivity with respect to changes in the light transmittance of the original. An automatic printing level detection method for a diazo copying machine, which is characterized by setting and detecting the light transmittance of a document. (2) A diazo copying machine that detects the light transmittance of the original and performs automatic printing control, which includes a conversion means that outputs an electrical signal corresponding to the amount of light transmitted through the original, and a plurality of comparators that receive the output of the conversion means. an original light transmittance detection circuit, and a reference voltage applied to each of the plurality of comparators is set based on a rate of change in photosensitive paper printing sensitivity with respect to a change in light transmittance of the original. Automatic burn level detection device for diazo copying machines.