GB2125248A

GB2125248A - Aperture mask for image scanning and recording apparatus

Info

Publication number: GB2125248A
Application number: GB08221291A
Authority: GB
Inventors: Ikuo Mitsuka
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1982-07-23
Filing date: 1982-07-23
Publication date: 1984-02-29
Also published as: DE3230073A1; GB2125248B; FR2530904A1

Abstract

An aperture mask 22 for use in the recording section of an image scanning and recording system is disclosed. The aperture mask defines a pair of apertures 29 of preferably identical size and shape in alignment with the optical path of a light beam 24 for exposing a recording material. Due to dispersion of the twin light beams after passing through the apertures, and to exposure spread in the recording material, scanning the twin light beams in a direction 26 at right angles to their direction of separation produces an exposed strip 27' having substantially straight ends (as against the round ends produced by a single scanning beam). <IMAGE>

Description

SPECIFICATION Aperture mask for image scanning and recording apparatus The present invention relates to an image scanning and recording apparatus for reproducing images on a recording sheet having a sensitive material by image signals obtained by photoelectrically scanning original images, and particularly to an aperture mask in the recording section thereof.

This type of image scanning and recording apparatus is used for example in fascimile equipment and in color scanners for producing color-separated images from a color original in the field of photomechanics.

According to the present invention there is provided, in the recording section of an image scanning and recording apparatus, an aperture mask defining a pair of apertures in alignment with the optical path of a light beam for exposing a recording material, the said apertures being arranged in spaced apart relation at a predetermined distance from one another.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of an image scanning and recording apparatus of the prior art; Fig. 2 is a schematic view of the recording section of the apparatus of Fig. 1; Fig. 3 iliustrates the type of image produced in the apparatus of Fig. 1; Fig. 4 shows a known type of aperture mask; and Fig. 5 illustrates an aperture mask according to the invention and the image which it produces.

The general arrangement of a known color scanner will first be described with reference to Fig. 1. A color original is mounted on an original cylinder 1 in the scanning section, while in the recording section, a recording film 4 is mounted on a recording cylinder 3, said two cylinders 1 and 3 being synchronously rotated by a common shaft 5. The shaft 5 is driven by a motor 6 through a speed reducer 7. The rotation of said motor 6 is also transmitted to a screw shaft 8 in a different speed reduction ratio to drive a recording head 9 along the recording cylinder 3. The rotation of said screw shaft 8 is transmitted to a screw shaft 11 through a stepless speed changer 10 to drive a pick-up head 12 along the original cylinder 1.The pickup head 12 is associated with an original illuminating device 1 3 comprising a light source 14, focusing lens 1 5 and a mirror 1 6. The pickup head 12 contains color filters, photoelectric tubes, etc., and produces image signals according to the tones and gradations of the original, said image signals being transferred to a color correction circuit 1 7. The image signals amplieid and compensated in the color correction circuit 1 7 enter the recording head 9, and the recording film 4 is exposed to light for color-separated images as by a laser beam source.

An outline of a recording optical system using a laser beam source A is shown in Fig. 2. For a laser beam, He-Ne is used because of its superiority, and for a light modulator for laser beam, an acousto-optic modulator 18 is used. The image signals obtained from the original 2 and corrected are applied, with variations in their intensity, to an acousto-optic modulator driving circuit 1 9 to produce- high frequency signals, which drive a piezoelectric transducer 20. The piezoelectric transducer 20 converts the high frequency signals into acoustic signals, which are led into an acousto-optic medium 21.Thus, when the laser beam from the laser beam source A is introduced into the acousto-optic medium 21, it is diffracted by sound waves and thereby modulated, and the laser beam emitted therefrom passes through an aperture 29 in an aperture mask 22 and then through a focusing lens 23 to impinge on the recording film 4 on the recording cylinder 3 for exposure and recording of color-separated images.

In the case of exposure-wise describing lines on the recording film 4 using the conventional image scanning and recording device described above, the intensity distribution of a flat laser beam 24 emitted from the focusing lens 23 is as shovvn in Fig. 3 (a) presenting a normal distribution curve 25 around the beam. As a result, if exposure is effected in a main scanning direction 26, which is associated with scanning in the direction of the circumference of the rotating recording cylinder 3, the film is exposed and developed in a manner shown by an area surrounded with a dotted line 27 as shown in Fig. 3 (b) wherein upper and lower arcuate portions 28 of depth approximately 20ym represent unnecessary exposure, owing to an adjacency effect caused by the exposure and development of the film.If, therefore, scanning exposure is effected in the main scanning direction 26 and secondary scanning direction 26' as shown in Fig. 3 (c), waves are formed in the upper and lower arcuate portions 28 in the transverse direction (secondary scanning direction 26'); thus, straight edges cannot be formed.

To eliminate this drawback, it has been proposed to use a concave lens shape for an aperture 29 formed in an aperture mask 22, as shown in Fig. 4. However, formation of such shape is expensive.

The present invention, in its preferred form, uses an aperture mask 22 having a pair of circular apertures 29 of diameter d spaced a distance L apart from each other, as shown in Fig. 5 (a). Thus, if exposure is effected with this aperture mask 22 in the main scanning direction 26, the laser beam 24 becomes tiny twin beams as it passes through the pair of apertures 29. The intensity distribution obtained after they pass through the focusing lens is as shown in Fig. 5 (c), while one obtained by exposure and development of a film is as shown in Fig. 5 (b) due to adjacency effect. If it is scanned, a portion surrounded with a dotted line 27' shown in Fig. 5 (d) is exposed.Even if the upper and lower horizontal lines have unevenness as a result of scanning exposure in the main scanning direction 26 and secondary scanning direction 26', such unevenness is only about 1-2 -2,um in cases where, e.g., d=0.3 mm and L = 1 mm, so that they are substantially smooth and lines can be accurately described as shown in Fig. 5 (e).

In brief, the present invention has the following advantages.

(1) The respective intensities of beams immediately after leaving the two apertures are as shown in Fig. 5 (a), but the beam intensities between the two apertures are superimposed on each other owing to fuzziness due to the lens, and adjacency effect due to exposure and development, as a result of which an even intensity distribution is obtained, ensuring that smooth lines are described on the portion exposed by scanning.

(2) Since it is only necessary to form two simple apertures in a thin aperture mask, the processing is easy.

It goes without saying that the shape of the apertures is not limited to a circle but may be variously changed according to required conditions.

Claims

1. In the recording section of an image scanning and recording apparatus, an aperture mask defining a pair of apertures in alignment with the optical path of a light beam for exposing a recording material, the said apertures being arranged in spaced apart relation at a predetermined distance from one another.

2. Apparatus as claimed in claim 1, wherein said pair of apertures are mutually spaced in a direction parallel to the secondary scanning direction of the recording material.

3. Apparatus as claimed in claim 1 or 2, wherein said pair of apertures are of identical size and shape.

4. Apparatus as claimed in claim 3, wherein each of said apertures is of circular shape.

5. Apparatus as claimed in claim 1, substantially as hereinbefore described with reference to the accompanying drawings.