JPH04369635A - Controller for copying machine - Google Patents

Abstract

PURPOSE:To execute copying well by correcting a signal corresponding to the light transmittivity of an original measured considering the wavelength dependency of the light transmittivity of the original, and the sensitivity of a photosensitive paper. CONSTITUTION:On a copying machine in which a substance obtained by superposing the original 26 and the photosensitive paper 32 is carried and carrying speed is controlled, so that exposing printing control to the photosensitive paper 32 is executed; (a) (n) degree polynomial expression in which an optimum carrying speed with respect to the light transmittivity of the original 26 is appropriated is previously found, (b) the light transmittivity of the original 26 is measured, and (c) the carrying speed is controlled by using the light transmittivity measured and the (n) degree polynomial expression.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a copying machine, and more particularly to a control device for a copying machine (for example, a diazo copying machine) that exposes and prints an original and photosensitive paper one on top of the other. Although the present invention is applicable to all copying machines that overlap and expose and print an original and photosensitive paper, for convenience of explanation, a diazo copying machine will be described as an example.

0002

2. Description of the Related Art In a conventional diazo copying machine that automatically controls exposure, the conveyance speed of photosensitive paper and the polymer of the original is controlled in proportion to the measured light transmittance of the original. However, the method of controlling the conveyance speed in proportion to the measured original light transmittance has a problem in that it is not always possible to obtain good copy density. The reasons for this are (a) the light transmittance of the original changes depending on the wavelength of the measurement light (wavelength dependence of light transmittance), and (b) the sensitivity of the photosensitive paper to the wavelength of the exposure light source and the light transmission of the original. This is thought to be due to a difference in the sensitivity of the light amount detection sensor that measures the rate.

0003

[Problem to be solved by the invention] To solve the problem that it is difficult to always make good copies with a method of controlling the conveyance speed of the original and the polymer of photosensitive paper in proportion to the measured light transmittance of the original. .

Therefore, it is an object of the present invention to correct a signal corresponding to the measured light transmittance of an original by taking into consideration the wavelength dependence of the light transmittance of the original and the sensitivity of the photosensitive paper, so that good copying can be achieved at all times. An object of the present invention is to provide a control device for a copying machine that can perform the following operations.

[0005]

[Means for Solving the Problems] A first embodiment of the present invention is as follows:
In a copying machine that conveys a polymer of an original and photosensitive paper and controls exposure printing on the photosensitive paper by controlling the conveyance speed, (a) an n-th degree polynomial that approximates the optimal conveyance speed for the light transmittance of the original is calculated. (b) measure the light transmittance of the original, and (c) combine the light transmittance measured in (b) above and (a) above.
), and the second embodiment of the present invention is a control device for a copying machine, which controls the conveyance speed using an n-th polynomial of In a copying machine that performs exposure printing control on photosensitive paper by controlling the (c) Create a correspondence table between the light transmittance determined in (a) and (b) above and the optimal transport speed, and (d) Calculate the light transmittance of the document inserted into the copying machine. This control device for a copying machine is characterized in that it measures the conveyance speed and controls the conveyance speed at an optimum conveyance speed based on the above-mentioned correspondence table.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a part of a diazo copying machine to which the present invention is applied. 10 is the main body of the diazo copying machine, 12
14 is a cylinder glass (baking glass); 16 is an exposure light source (for example, a mercury lamp) housed inside the cylinder glass 14; As is well known, a conveyor belt (not shown) rotates in contact with the cylinder glass 14, and the stacked document and photosensitive paper are conveyed by the conveyor belt along the outer surface of the cylinder glass 14, while Exposure to photosensitive paper is performed. One end of the optical fiber 18 serving as a light guiding means is provided outside or inside the cylinder glass 14 to take in the light from the light source 16, and the other end is provided on the light amount detection sensor 20 side. 22 is a drive motor of the copying machine, 24 is a document table, 26 is a document, 28 is a first document detection circuit, 29 is a second document detection circuit, 30 is a standby roll for documents;
32 is photosensitive paper, 34 is a transport roll, and 36 is a developing device.

When the original 26 is inserted into the copying machine and the leading edge of the original 26 reaches the first original detection circuit 28, the light amount detection sensor 20 detects the amount of light Lt from the optical fiber 18. The original 26 is further carried in, and the second original detection circuit 2
9 detects the leading edge of the document, it starts measuring the amount of light transmitted through the document. The reason for providing the second document detection circuit 29 is to measure the amount of transmitted light of the document while ensuring that the document exists between the end of the optical fiber 18 and the light amount detection sensor 20. The measurement of the amount of light transmitted through the original is performed for a certain period of time from the time when the second original detection circuit 29 detects the leading edge of the original 26 . That is, the maximum value among the measured amounts of light transmitted through the original is set as the amount Ls of light transmitted through the original. This is to avoid the mistake of assuming that the amount of transmitted light in a non-ground portion of the document (a portion where characters, graphics, etc. are present) is the amount of transmitted light of the document. The light transmittance Sk of the original is determined by the following equation 1.

[Math 1] Sk = Ls/Lt (0　　＜　Sk　　＜　　1)

Before explaining the present invention in detail, the causes of the conventional problems will be briefly explained. Conventionally, the conveying speed V of the polymer between the original and photosensitive paper has been determined in proportion to the light transmittance Sk of the original, as shown in Equation 2.

[Formula 2] V = K (Ls/Lt) Lp where, K
is a proportionality constant, and Lp is the light amount of the exposure light source. In other words,
Conventionally, as shown by a solid line 50 in FIG. 2, the conveyance speed V was made proportional to the light transmittance Sk of the document.

However, according to experiments conducted by the present inventors, in order to obtain good copies, the relationship between the light transmittance Sk of the original and the transport speed V must be non-linear, as shown by the broken line 52 in FIG. It turned out that.

The reason for this is thought to be as follows. First, the light transmittance of the document is not constant with respect to the wavelength of the light source, but changes as shown in FIG. 3, for example (the wavelength and transmittance numbers in FIG. 3 are merely examples). Furthermore, as shown in FIG. 4, the sensitivity of the light amount detection sensor 20 to the light source wavelength (
54) and the sensitivity of the photosensitive paper to the light source wavelength (56
), and it is extremely difficult to match these sensitivities. On the other hand, the light transmittance Sk of the document obtained by the light amount detection sensor 20 is given by Equation 3.

[Equation 3] Sk = Hkd Here, d is the thickness of the original, and Hk is a constant (0<Hk<1) determined by the light amount detection sensor and the type of the original.

Furthermore, if the optimum transmittance considering the sensitivity of the photosensitive paper is Sr, then

[Equation 4] Sr=Hrd Here, Hr is a constant (0<Hr<1) determined by the sensitivity of the photosensitive paper and the type of document. That is, since Hk and Hr are different, it is considered that good copying cannot be achieved even if the conveying speed is determined in proportion to the light transmittance of the original.

Therefore, in the first embodiment of the present invention, as shown below, the optimum transmittance Sr is determined in consideration of the sensitivity of the photosensitive paper.
is expressed by an n-th polynomial of the actually measured original light transmittance Sk, and by substituting the actually measured Sk into the n-th polynomial, S
The transport speed is controlled by determining r. Formula 3 and Formula 4
With reference to

[Formula 5] M = log(Hr)/log(Hk)
given that,

[Formula 6] Sr = SkM. Here, M is the wavelength-dependent light amount detection sensor 2
This is a coefficient determined by the difference between the sensitivity of 0 and the sensitivity of photosensitive paper.

As is well known, Sr shown in Equation 6 can be approximated by the following n-th degree polynomial.

[Formula 7] Sr=a0+a1Sk+a2Sk2+...+anSk
nAssuming that the simplest method is to take up to the first-order term,

[Formula 8] Sr = a0 + a1Sk.

On the other hand, the optimum conveyance speed V is

[Math. 9]V
= C·Lp·Sr = C·Lp (a0+a1Sk) Here, C is a constant, and Lp is the amount of light during exposure as described above. FIG. 5 is a diagram showing the relationship between the measured document light transmittance Sk and the optimum transport speed V, where the broken line 52 shows a characteristic curve that provides the optimum transport speed, and the solid line 60 is a characteristic straight line obtained from Equation 9. . Therefore, the coefficient a0 is
If and a1 are determined in advance, good copying can be expected.

[0015] Furthermore, if we take up to the quadratic term of Equation 7, we get

[Formula 10] Sr=a0+a1Sk+a2Sk2. In this case, there are three unknown coefficients, so the original transmittance Sk=
If we assume that Sr=0 when Sk=1 and Sr=1 when Sk=1, then a0 = 0 a1 + a2 =1, so

[Formula 11] The number of constants can be reduced to one, as in Sr=a1Sk+(1-a1)Sk2. Therefore, it is very easy to find a1 to obtain a good copy. According to the present inventors, a1 was obtained by experiment and the formula 1
1 could be brought close to the ideal curve 52 in FIG.

[0016] Equation 11 is stored in a suitable storage means, Sr is determined from the light transmittance Sk of the document using a central processing unit (CPU), and the optimum conveyance speed V is calculated using Equation 9.
All you have to do is ask for. In the above explanation, approximate expressions up to the first-order and second-order terms were used, but the present invention is not limited to this.
An approximate expression of a polynomial of higher order than third order may be used.

In the first embodiment described above, an approximate formula for Sr was obtained and a good copy was obtained. However, as will be explained next, a plurality of originals and photosensitive materials with different light transmittances that are expected to be actually used will be used. It is also possible to prepare a sheet of paper, determine through experiments the conveying speed at which the best copy can be obtained with respect to the light transmittance of each original, and create a correspondence table. That is, (a) find the light transmittance of each of the different documents, (b) find the optimal transport speed for each of the light transmittances of the different documents found in (a) above, and (c)
) Create a correspondence table between the light transmittance obtained in (a) and (b) above and the optimum transport speed and store it in an appropriate storage means in the copying machine, and (d) calculate the light transmission of the original inserted into the copying machine. The transport rate may be measured and the transport speed may be controlled at an optimum transport speed based on the above-mentioned correspondence table.

[0018]

As described above, according to the present invention, the sensitivity of photosensitive paper and the sensitivity of the light amount detection sensor for measuring the light transmittance of the document are different from each other, and the wavelength of the light transmittance of the document is This method has the remarkable effect of solving the problem of not being able to obtain good copies due to dependencies.

[Brief explanation of drawings]

FIG. 1 is a diagram briefly explaining the operation of a diazo copying machine to which the present invention is applied.

FIG. 2 is a diagram showing the relationship between the light transmittance of a document and the conveyance speed.

FIG. 3 is a diagram illustrating that the light transmittance of a document depends on the wavelength of a light source.

FIG. 4 is a diagram illustrating the difference between the sensitivity of a light amount detection sensor and the sensitivity of photosensitive paper.

FIG. 5 is a diagram illustrating the optimum conveyance speed with respect to the light transmittance of a document.

[Explanation of symbols]

20 Light amount detection sensor 26 Original 32 Photosensitive paper 54 Curve showing the sensitivity of the light amount detection sensor to the light source wavelength

Claims (2)

[Claims] [Claim 1] In a copying machine that conveys a polymer of an original and photosensitive paper and controls exposure printing on the photosensitive paper by controlling the conveyance speed, (a) approximating the optimum conveyance speed for the light transmittance of the original; (b) Measure the light transmittance of the document; (c) Calculate the transport speed using the light transmittance measured in (b) above and the n-th polynomial in (a) above. A control device for a copying machine characterized by controlling the copying machine. 2. In a copying machine that conveys a polymer between an original and photosensitive paper and controls exposure printing on the photosensitive paper by controlling the conveyance speed, (a) determining the light transmittance of each of the different originals; (b) Find the optimal transport speed for each light transmittance of the different documents found in (a) above, and (c)
Create a correspondence table between the light transmittance obtained in a) and (b) and the optimal transport speed, and (d) measure the light transmittance of the original inserted into the copying machine, and determine the optimal transport speed based on the above correspondence table. A control device for a copying machine, characterized in that the conveyance speed is controlled by.