JPH0315183B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical printer, and the method of printing line picture elements, which are constituent elements of printed characters or figures, is continuous in a solid line or separated in a dotted line. The purpose of this is to make it possible to change the printing condition according to one's preference.

Conventionally, optical printers use a gas laser or semiconductor laser as a light source, modulate this light source with an electrical signal, and scan the light beam laterally with a rotating polygon mirror to form a latent image on a drum of a photosensitive recording medium. was. FIG. 1 shows an example of an optical printer using a semiconductor laser. The light beam A modulated by the electric signal and emitted by the semiconductor laser 11 is irradiated onto the photosensitive drum 14 through the lens 13 by rotating the rotating polygon mirror 12 at high speed. A charged corona generator 18 charges the photosensitive recording medium drum 14 in advance, and the light beam A
A latent image of charge is formed on the drum 14 depending on the presence or absence of the latent image, which is developed by a developing device 15 comprising toner application means and transferred onto plain paper 10 by a transfer drum 16. The remaining toner and the like are cleaned by a cleaner 17.

In this case, when the rotation speed of the rotating polygon mirror 12 is kept constant, the pulse width of the electric signal to the modulator 19 of the semiconductor laser 11 causes the constituent line pixels of the printed character or figure to be printed as a solid line. They can be connected in a shape or separated in a dotted line. However, changing the time axis of the electrical signal is difficult in terms of timing with mechanical systems and the like.

The present invention has been made to solve the above problems, and uses a light emitting diode array in which light-emitting parts are separated at predetermined intervals as a light source, and uses an operating current when the light emitting diode array is lit to determine the operating current of the light emitting diode array. By adjusting the current so that the maximum value is within 2.5 times the minimum value, constituent line pixels such as printed characters or figures can be connected in a solid line or separated into dotted lines. This is what I did.

The principle of the present invention will be explained below.

Consider the case where output light from a light emitting diode or semiconductor laser is focused through a lens system. As shown in Figure 2a, the light emitting spot 21 of the semiconductor laser
When the image is formed using the lens 23, the image becomes sharp like 22. This is thought to be because the coherence of the light emission of the semiconductor laser and the strong directionality of the light emission are strong, so that the influence of lens aberrations is small. However, when the light emitting spot 25 of the light emitting diode is imaged using the lens 23 as shown in FIG. This is thought to be because the light emission is non-coherent and because the directivity is approximately 180 degrees wide, it is likely to be affected by lens aberrations. In such a halation image, as the current of the light emitting diode is increased, the area of the image 26 irradiated with constant energy becomes wider and wider. For this reason, even if light emitting diode arrays arranged in a straight line so as to have separate light emitting parts are turned on simultaneously, in an imaging experiment similar to that shown in Fig. 2b, the shape will change from a dotted line to a dotted line shape depending on the operating current level as shown in Fig. 3. Changes like a solid line. In other words, when the operating current is at the level of _IF , the light-emitting spot from the separate light-emitting section is originally formed into a dotted line 31 as shown in Figure 3a, but when the operating current is increased to about _1.5IF , it forms an image as shown in b. It takes the form of a continuous line.

Figure 3c shows the relationship between the writing spot diameter and the operating current when writing is performed by lighting one LED on the photoreceptor. Assuming that the operating current A in the figure is the minimum value for writing, as the current increases, the spot diameter increases almost linearly, but when the operating current exceeds B, a nonlinear change occurs, which is considered to be a thermal effect. . The value of point B varies somewhat depending on various heat dissipation conditions, but it is approximately within 2.5 times the minimum operating current. Utilizing these characteristics, the present invention
By adjusting the operating current when the LED is lit within a range where the maximum value of the operating current is within 2.5 times the minimum value of the operating current, line picture elements such as characters or figures to be printed become solid lines. The object of the present invention is to provide a device that allows the user to move closer to the dotted line.

An embodiment of the present invention will be described below.

FIG. 4 shows an embodiment of the present invention.
First, a light source 40 consisting of a light emitting diode array, in which light emitting parts 41 are arranged separately at predetermined intervals as shown in FIG. The operating current level is set by an operating current control circuit 42 to control the printing state of the A, and an input signal from A is applied to a drive circuit 44 that causes the light source 40 to be turned on in an appropriate manner, for example, by scanning or simultaneously.
The light source 40 is turned on, and an image of this light spot array is formed on the photosensitive recording medium drum 14 by the lens system 43. A charge is placed on the photosensitive drum 14 in advance by the charged corona generator 18, and this drum 1
4, an image of the light spot array is formed, and a latent image of charge is created by the photoelectric effect. Next, a developing device 15 forms a toner image, and a transfer drum 16 transfers this onto plain paper 10. The remaining toner is collinated by a cleaner 17.

The above operation enables the basic operation of the present invention. Specifically, the operating current control circuit 42 may be configured as shown in FIG. 5, for example. That is, the drive signal input Vin turns on the transistor Tr and lights up the light emitting diode LED. At this time, Ro is a resistor that limits the maximum amount of light, and the operating current is controlled by providing a variable resistor Rx. The volume of this variable resistance Rx can be attached to the control position from outside the device.

As described above, the present invention forms an image of light from a light source consisting of an array of light emitting diodes in which light emitting points are separated at predetermined intervals on a photosensitive recording medium through an optical system, and images of these lights being lit or not being lit. In an electrophotographic optical printer that forms a latent image by exposure to light, by adjusting the operating current when the light emitting diode is turned on so that the maximum value of the operating current is within 2.5 times the minimum value of the operating current. The present invention provides an optical printer that can make line picture elements such as printed characters or figures into solid lines or dotted lines, and has the advantage that the printing condition can be changed depending on the preference of the object to be printed. This will also lead to expanded uses for printers.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the concept of a conventional optical printer, and FIGS. 2 a and b are diagrams showing image formation when a light emitting diode and a semiconductor laser are used as the light source.
Figures 3a, b, and c are diagrams showing changes in spot diameter due to operating current; Figure 4a is a configuration diagram of an optical printer according to an embodiment of the present invention; Figure 4b is a perspective view of a light source used in the printer. , FIG. 5 is a wiring diagram showing a specific example of the circuit configuration of the operating current control circuit. 10... Plain paper, 14... Photosensitive drum, 15
...Developer, 16... Transfer drum, 17... Cleaner, 18... Charged corona, 40... Light emitting diode array light source, 41... Light emitting section, 42... Operating current control circuit, 43... Lens system, 44...Drive circuit.

Claims (1)

[Claims] 1. A light emitting diode row in which a plurality of light emitting diodes are separated from each other at a predetermined interval, a lens system for forming a light image from the light emitting diode row onto a photosensitive recording medium, and a light emitting diode row for each light emitting diode in the light emitting diode row. and a drive circuit that adjusts the applied drive current within a range of 2.5 times from the minimum value of the operating current, and the photosensitive recording medium is located at a position where the lens system forms a light image from the light emitting diode array. An optical printer characterized by being placed in a.