JPS6153616A - Scanner - Google Patents

Abstract

PURPOSE:To generate hardly focal dislocation on an object to be scanned, by providing a beam detector for detecting a focal position by receiving a beam, in a scanning range of the beam, and executing a focal control to the object to be scanned of the beam in accordance with a detecting signal of said detector. CONSTITUTION:A light emitted from a laser 1 is condensed by a lens 2 and scanned in the direction b-b' by a rotating body 3. A beam detector 6 is placed at a focused position of lens 4, and this detector 6 detects a write timing of the time of scanning of one line, and an expanse of a beam on the photodetecting surface by using, for instance, a line sensor, and detects a focal dislocation quantity. That is to say, the surface of a drum 5 can be held in a focused state at all times by calculating the focal dislocation quantity by a processing circuit 7, moving the lens 4 by the quantity corresponding to the defocus quantity by a driving circuit 8, and varying the image forming position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a scanning device that scans an object while converging a radiation beam used in, for example, a laser beam printer (hereinafter referred to as LBP).

[Prior art]

Conventionally, scanning devices such as I and BP+2 were constructed using a fixed focus system, which required extremely high precision for the individual components that made up the device, and also required a precise optical adjustment car during assembly. A plastic lens was also used as a beam focusing means.

[Purpose of the invention]

The present invention was made in view of the above-mentioned conventional example, and its purpose is to provide a scanning device that has a simple and inexpensive configuration, does not cause a focus shift on an object to be scanned, and is easy to assemble with only 1 force. koto (= there is).

[Structure of the invention]

The above-mentioned object of the present invention is to use a scanning device (=1, %) that scans a radiation beam while converging the object to be scanned (=a scanning device (=1,%) that scans a radiation beam while converging the object (=1, %), a beam that detects the focal position by receiving this beam. A detector is set up, and the detection signal of the beam detector is therefore scanned by the beam.

〔Example〕

Hereinafter, the present invention (two l/) will be referred to as LBI! - An applied embodiment will be explained with reference to the drawings.

First, an example of a general configuration of the LBP will be described with reference to FIG. 6.

Reference numeral 1 designates a laser oscillator, and a light beam 1 is focused by a lens 2 and irradiated onto the surface of a polygon 6. Since the polygon 6 is rotating at a predetermined number of rotations, the emitted light ray l is directed in the a a' direction (
= having an expanse. Reference numeral 4 denotes a lens, which is structured to form an image of light onto the light-receiving surfaces of the drum 5 and the beam detector 6.

FIG. 1 is a schematic top view of an embodiment of the scanning device of the present invention.
A mechanism similar to that shown in FIG. 6 (two to which the present invention is applied) is shown.

The light emitted from the laser 1 is focused by a lens 2' and sent to a rotating body 6.
(The beam detector 6 is scanned in the b-b' force direction from the second position. The beam detector 6 is located at the focal position of the lens 4. The beam detector 6 is configured to determine the writing timing when scanning one line using, for example, a line centimeter. It has a function of detecting the spread of the beam on the light receiving surface and detecting the amount of defocus as shown in FIG.

The timing of defocus measurement may be when the power is turned on, at regular intervals, or every time. Now, the out-of-focus amount dZ and the extent L of the blur between the two images are expressed as L:dZ/F (F is the F number of the lens 4).

That is, the amount of defocus is calculated by the processing circuit 7, and the corresponding amount is determined by the amount of defocus dZ +. It is possible to maintain a focused state. The present invention (=
According to the current situation, due to environmental issues (temperature, humidity), it is also possible to use plastic lenses, which have a change in optical performance that is 1 to 2 orders of magnitude larger than glass lenses.

In the above embodiment, two methods were described in which the lens is moved in the focal direction, but methods for correcting defocus include (but are not limited to) methods such as changing the refractive index by changing the electric field intensity using an electro-optic crystal, or using a wedge. The focal position may be changed by placing a single layer of glass in a focused beam and moving them in a direction perpendicular to the optical axis (= =).In addition, in the example, a beam detector was used to measure the timing of writing. However, it is also possible to provide a beam detector for focus detection completely independently of such a detector for timing detection.Also, the detection method is not limited to one that uses line centimeters, but can also use a detector with a divided light-receiving surface. Furthermore, it is possible to provide the beam detector with a focus detection function (two tilt detection functions, etc.) to correct the tilt of the lens, for example.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a beam detector having a focus detection function in a conventional scanning device (=), it is possible to perform scanning without defocusing with a simple configuration. It has also become possible to use plastic lenses, which are inexpensive and easy to manufacture.

[Brief explanation of the drawing]

FIG. 1 is a schematic top view of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the amount of blur in an image, and FIG. 6 is a perspective view of a general configuration example of a laser beam finter.

Claims (1)

[Claims] In a scanning device that scans a radiation beam while focusing it on an object to be scanned, a beam detector that receives the beam and detects the focal position is provided within the scanning range of the beam, and detects the focal position of the beam according to the detection signal of the beam detector. A scanning device characterized by performing focus control on an object to be scanned.