JPS59157663A - Image recording control method - Google Patents

Abstract

PURPOSE:To obtain the invariably constant quantity of detection from images with the same density and perform stable image recording by correcting the computed value of density of a recording image even when image recording condition changes during variable power or owing to environmental variation, etc. CONSTITUTION:The signal of a surface potential sensor 7 is made constant in level by a potential measuring circuit 12 and inputted to an integration circuit 13 during original density detection. A control circuit 14 for the quantity of light controls a halogen lamp 9 through a regulator 15 according to the integral value of the circuit 13. A latent image at a white part 16 is detected by the sensor 7 to control the lamp 9 through circuits 17, 14, and 15 so that a set value VL is obtained. Exposure amount-latent image potential characteristics and EV characteristics vary even during variable power or in case of environmental variation, so signals of an operation part 18 and a temperature and humidity sensor are sent to the circuit 13 to make specific corrections on the basis of predetermined temperature and humidity or a corresponding value of variable power.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for detecting document density and controlling image recording means based on the detected value.

BACKGROUND TECHNOLOGY Conventionally, a method has been proposed in which, in an image recording device such as a copying machine, a document is exposed and scanned in advance before the copying process to detect the condition of the document, and the exposure amount, development bias, etc. are controlled according to the detected value. has been done.

An example of this method will be explained with reference to FIG. Prior to the actual copying process, a latent image of one document 20 is formed on the photoreceptor drum 21 by exposing and scanning the optical system 24 from the starting point P in the direction of arrow A to the ending point Q.

This latent image potential is measured by a potential sensor 22, and an integrating circuit 26
By integrating the latent image potential of the document from P to Q, This integrated value is detected as the density of the document.

In this method of detecting document density using the latent image potential on the photoreceptor drum, the exposure amount-latent image potential characteristic (hereinafter referred to as E-V characteristic), which is the sensitivity characteristic of the photoreceptor drum, must always be constant. Otherwise, the original density cannot always be detected correctly. However, the EV characteristics change due to changes in exposure position due to changes in copying magnification, environmental changes, and the like. For example, in the same magnification mode, the E-V characteristic is as shown in Figure 2 + 5, and the dark area potential (
The potential (black) is Vo and the bright area potential (white) is vL. and,
The latent image potential of the original is measured by exposing the original to an exposure amount of Ew on a white original. Here, the reflection density of the original is expressed as D=log 1/R, where R is the reflectance.

Generally, the reflection density of a white original is D=0.07, so R=
8.51 (ch). In addition, in the case of a -7 tone original with a reflection density of 0.3, R = 5.01 (H), but the exposure amount in this case is about 60% of that in the case of D = 0.07. 6Ew, and its latent image potential becomes VHT.

Assume that this EV characteristic becomes K as shown in FIG. 2(b) due to a change in the exposure position when the copying magnification is reduced to 0.7 times.

At this time, the exposure amount of the white original is Ew, and the reflection density is 0.
The exposure amount of halftone 6 is about 0.6 yen and its potential is v
Become commonplace. Therefore, if the sensitivity characteristics of the photosensitive drum change, even if the original is exactly the same, it cannot be detected integrally.

Purpose The present invention has been made in view of the above points, and an object of the present invention is to provide an image recording control method that can always record a stable image even if the image recording conditions fluctuate.

A further object of the present invention is to provide an image recording control method in which the detected value of document density for the same document is kept constant regardless of variations in image recording conditions.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 6 is a schematic configuration diagram showing the configuration of a copying machine to which the present invention is applied. Reference numeral 1 denotes a photosensitive drum, which is composed of three layers, an insulating layer, a photoconductive layer, and a conductive layer 6 from the surface, and is supported rotatably in the direction of the arrow.

Around this photosensitive drum 1, a primary charger 2,
Secondary charger 3. Full exposure rung 4. The position sensor 7, the developing roller 5 of the developing device. A transfer charger 6°, a lamp 7 for pre-static elimination, and a charger 8 are arranged.

The entire surface of the photosensitive drum 1, which has been neutralized by the lamp 7 and the charger 8 before each process, is uniformly charged by the primary charger 2.
After being charged with a trap, the original 100 is illuminated by a halogen lamp 9 for exposing the original, and the reflection source is the mirror 9a~
The image is formed on the photosensitive drum 11 via the lens 9C and the lens 9d. A simultaneous trap secondary charger 6 removes charges according to the image of the document and forms a latent image. Subsequently, the entire surface is exposed by a full-surface exposure lamp 4, and then toner is developed by a developing roller 5. As will be described later, an alternating current bias voltage is applied to the developing roller 5 to improve the gradation of the image by jumping development. Continuing to step 1, the transfer charger 6 is activated to apply a transfer force 1 to a recording paper (not shown). Toner remaining on the photosensitive drum 1 after transfer is removed by a cleaner 11.

Also, a photosensitive drum 1 is placed between the entire surface exposure lamp 4 and the developing roller 5.
A surface potential sensor 7 is arranged to measure the surface potential of the surface potential sensor 7, and the signals from the surface potential sensor 7 are converted into a signal at a predetermined level by a potential measuring circuit 12, and then sent to an integrating circuit 13 when detecting the density of the document. Enter. According to the integral value by the integrating circuit 15, the light amount control circuit 14 controls the
A control signal is output to the lamp regulator 15 to control the input voltage to the halogen lamp 9 so that the amount of light is appropriate for the original 10. The time constant of the integrating circuit 150 is selected from the key force signal equal pressure from the operating section 18 in accordance with the copying magnification.

In addition, prior to detecting the original density, the standard white plate 16 is heated to G+ by the halogen lamp 9, and its latent image potential is detected by the potential sensor 7, and is adjusted according to the output from the VL control circuit 17 so as to reach the set value VL. , a control signal is output from the light amount control circuit 14 to the lamp regulator 15, and the control signal is output from the light amount control circuit 14 to the lamp regulator 15. is controlled. This allows the 7
- The light amount of the rogen lamp 9 is determined.

In the above configuration device, before scanning for document density detection, the potential of the standard white plate 16 is set to the set value of the white background potential −VL.
7. The voltage applied to the rogen lamp 9 is controlled so that the voltage becomes K. The E-V% characteristic at the same magnification is shown in Figure 2 (a), and the electrostatic latent image surface potential is the dark area potential (black) V.

is set to about 500 V, and the bright area potential (white) VL is set to about 0.

First, the original white plate 16 in front of row 5 is illuminated with a halogen lamp 9, and the surface potential VL at this time is measured by the potential sensor 7.
If the voltage is measured by the potential measurement circuit 12 and deviates from %VL=O(V), the VL control circuit controls the applied voltage.
The light amount of the halogen lamp 9 is corrected and a control signal is sent to the lamp regulator 15 so that VL:0 (V).

With this vL control, document detection is 'XHCVL=0(V)
The light intensity of the halogen lamp 9 is as follows. When the VL control is completed, the optical system is scanned once in the direction of the arrow, for example,
The photosensitive drum is moved by the minimum original scanning distance to form a latent image potential of the IK original. This potential is converted to potential 7. Potential measurement circuit 12, integration circuit 13. Light amount control circuit 14. The exposure amount of the halogen rung 9 before copying is adjusted to be appropriate depending on the density of the original via the lamp regulator 15. τ is the integral constant of the integrating circuit when detecting the density of the original.

Assuming that the integration time is t, in the case of a halftone original with a reflection density of 0.6 as described above, the integrated value is HT7t.

However, during reduction, the EV characteristic changes to K as shown in Figure 2(b) due to a change in the exposure position, so when a halftone original with the same reflection density of 0.6 is detected, this integral value becomes v4r,...
t. Therefore, during reduction, the integration time constant τ' becomes equal to the time constant τ according to the signal from the operation unit 18. To explain this with reference to FIG. 4, when the magnification is the same, the slope of the incline when the vehicle enters the vehicle is the same sum both when the magnification is the same and when the magnification is changed, and the detected amount is the same K at Vc. If no correction is made and the integration is performed with the same time constant τ, then vC'
This results in different detection amounts even though the original is the same. Since the E-V% characteristic is almost a straight line between 0.6Bw and Bw, and the average density of general originals is almost always a reflection density of 0.5 to 0.07, E-
Even if the V characteristic changes, the document density can always be detected correctly by correcting the integral value using the time constant.

In the above embodiment, the integral value is corrected using the time constant τ, but it can also be done by changing the integral time t. Since the integration time t is the time during which the detection part of the document is being detected,
If the detection width of the original is l and the scanning speed of the optical system is υ, then t
It is determined by = l/ll. Therefore, the time constant τ may be kept constant and the scanning speed of the optical system may be selected when reducing the integration time t. The above correction is shown in Fig. 5. The time constant τ is the same for equal reduction, but since the inputs are v+v and V4v, the slope of the rise is different, so if the integration time and t are the same, the detected amount is It becomes Vc when it is the same size, and Vc' when it is reduced. However, the integration time becomes longer and the detected amount coincides with Vc, which is the same as that of the same magnification.

In addition, the correction at the same magnification and reduction is performed using the signal from the operation unit 18.
Although the E-V characteristics change due to environmental changes, the signal from the temperature/humidity sensor is sent to the integration circuit 15, and the above integration constant τ and integration time t are set in a predetermined temperature or humidity range. By selecting K, it is also possible to correct the detected amount.

Effects As described above, according to the present invention, even if image recording conditions change due to changes in magnification or environmental changes, the calculated value of the density of the image to be recorded is corrected, so that images of the same density can be recorded. On the other hand, it is possible to always maintain a constant detection amount and to record a stable image at all times.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a copying machine for explaining a conventional image recording control method, FIG. 2 is a diagram showing changes in the EV characteristics of a photosensitive drum, and FIG. 6 is an embodiment of the present invention. FIGS. 4 and 5, which are schematic configuration diagrams of a certain copying machine, are diagrams for explaining the amount of integration of an integrating circuit. In the figure, 1 is a photosensitive drum, 9 is a burnt/rung, 12 is a potential measurement circuit, 15 is an integration circuit, 14 is a light amount control circuit,
15 is a Lambre 4 corulator, and 18 is an operation section.

Claims (1)

[Claims] (1) Detecting the density of the original (in a method of controlling an image recording means, image recording control is characterized in that the detected value of the original density for the same original is kept constant regardless of fluctuations in image recording conditions) Method: Q) The image recording control method according to claim 1, wherein the detected value is an integral value of document density, and the integral value is corrected in accordance with fluctuations in the image recording conditions. C5) In claim 2, the image recording control system is characterized in that an integration time constant or integration time is selected in accordance with fluctuations in the image recording conditions.(4) In claim 1, The image recording control method is characterized in that the image recording means has a photoconductor, and the variation in the image recording condition is a variation in sensitivity of the photoconductor.