Toshiba 4511, 3511 manual Image Quality Control, Principle of the Sensor

15. IMAGE QUALITY CONTROL

15.1 General Description

In this equipment, image quality is controlled by the image quality sensor. At this control, image forming conditions are automatically adjusted so as to minimize the change in the image density or tone repro- duction caused by the fluctuation of working environment or life of supply items.

At first, the image quality sensor operates to output reflected light amount voltage when no toner image is formed on the transfer belt. The output voltage is then converted analog-to-digital to be output as the reflected light amount signal. The light source amount voltage of the sensor is adjusted to correspond with the value set in advance and the output value of reflected light amount signal at this adjustment is stored. This output value is considered as the reading of the belt surface. Next, the sensor outputs the reflected light amount signal when a test pattern is developed on the transfer belt. This output value is considered as the reading of the toner image.

The difference between the reading of the transfer belt and that of the toner image is defined as toner adhesion amount. Image forming conditions are determined in approximating this toner adhesion amount to the value set in advance.

In addition, a shutter operated by the solenoid is equipped on the light receiving/emitting surfaces to prevent stain to the sensor and to calibrate the sensor with the reflection from the shutter.

15.2 Principle of the Sensor

Image quality sensor projects light onto the transfer belt and the toner image (test pattern) developed on the transfer belt to output a voltage corresponding to the reflected light amount.

The output voltage is then converted analog-to-digital into reflected light amount signal. The CPU calculates the toner adhesion amount to control the image forming conditions.

15

Transfer belt

Test pattern (toner image)

Light emitting	Light receiving
element	element

Reflected light amount voltage

Light source amount voltage

A/D

D/A

Reflected light amount signal

Light source

amount signal

CPU

Fig. 15-201

November 2003 © TOSHIBA TEC 15 - 1 e-STUDIO3511/4511 IMAGE QUALITY CONTROL