JPS604936A - Optical scanning exposure device - Google Patents

Abstract

PURPOSE:To correct intensity of illumination irregularity in a scanning direction and uniform intensity of illumination by arranging a light shield member which is parallel to the lengthwise direction of a slit for exposure between a projection lens and a photosensitive body. CONSTITUTION:When pieces of focusing luminous flux (a)-(d) having angles of views from a film 1 to a lens 2 are projected on the photosensitive body 5, the quantities of light are limited by the slit 7 for exposure. The light shield member 6 is arranged fixedly between moving optical systems 3 and 4, and slit 7 for exposure in the lengthwise direction of the slit; and part of the forcussing luminous flux (a) at the center part of the film is cut off so that the amount of light shielding decreases gradually according to the distance from the center part, and neither the pieces (b) nor (c) of focussing luminous flux at a film end part is cut off. The quantity of exposure becomes less and less toward the film center part, so the intensity of illumination irregularity in the scanning direction is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical scanning exposure device that projects an image of a stationary document such as a microfilm using a moving optical system, and exposes the projected image to a moving photoreceptor using a slit. The present invention relates to the above device for correcting uneven illuminance.

Conventionally, methods for enlarging and projecting a stationary document, such as microfilm, onto a moving photoreceptor include a film movement method, a projection lens movement method, and an image field scanning method. Since it is necessary to change the speed of movement of the lens and the moving speed of the lens, and the configuration becomes complicated, an image field scanning method as shown in FIG. 7 has been proposed. In this method, as shown in Fig. 1, the projected image of a fixed film by a fixed projection lens unit is transferred to a movable photoreceptor 3 via an optical system (mirror) 3 that moves synchronously on the image field side. Although this is a slit exposure method, the scanning speed of the moving optical system 3 and the moving optical system 3 is constant even when changing the magnification, so the configuration is relatively simple.

However, in this method, as shown in FIG.
, ll/, the slit is projected at different angles onto E of the photoconductor (that is, the angle of incidence of the light beam on the lens changes as the original is scanned).As a result, there is illuminance unevenness on the photoconductor due to the 6089th power law of the lens. occurs. Furthermore, unevenness due to the microfilm lighting system is added. In order to correct such uneven illuminance, conventional methods have used optical filters that make the amount of transmitted light uneven, or rotated the entire exposure slit in one piece, but the foreground is difficult to manufacture. However, the latter has the disadvantage that the configuration is complicated.

The present invention has been made to eliminate the above-mentioned drawbacks, and includes an exposure slit arranged near the photoconductor in the optical path between the projection lens and the photoconductor, and a fixed slit parallel to the longitudinal direction of the slit. An object of the present invention is to provide an optical scanning exposure device that can correct illuminance unevenness in the scanning direction and make the illuminance uniform in the moving direction on the surface of a photoreceptor over the entire exposure area by arranging a light shielding member. shall be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to FIG. 2, which shows an embodiment of the present invention. A, b, c, and d are imaging light fluxes at respective angles of view of the film and the lens, respectively, and when projected onto the photoreceptor S, the amount of light is limited by the exposure slit 7. The exposure slit has an opening that varies in its longitudinal direction, and has the function of correcting uneven illuminance in the longitudinal direction.

Reference numeral B denotes a light shielding member, which is fixedly arranged between the moving optical system and the exposure slit 7 in parallel to the longitudinal direction of the exposure slit. The light shielding member B is the imaging light beam a at the center of the film.
As you move away from the center of the film, at first the light is blocked by almost the same amount, but then the amount of light blocked from the imaging light flux d gradually decreases, and the imaging light flux at the edge of the film is completely blocked. .

In C, do not block light.

If such a light shielding member is provided, the amount of exposure decreases as the film gets closer to the center, so it becomes possible to correct uneven illuminance in the scanning direction.

Furthermore, as another example, as shown in FIG. 3, unevenness in illuminance in the scanning direction can be similarly corrected by using several light shielding members and arranging them approximately parallel to the imaging light beams C and C. can do.

In this case, the amount of light shielding gradually decreases as the distance from the center of the film increases.

Further, as for the shape of the light shielding member B, in addition to the plate shape used in this embodiment, the effect can also be obtained by using a wire shape with a circular cross section.

As described above, the present invention provides an optical scanning exposure device that has an exposure slit and changes the angle of incidence of a light beam onto a photoreceptor as a document is scanned. Providing the light shielding member has the effect of making it possible to correct illuminance unevenness, especially in the scanning direction.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an image field scanning type optical scanning exposure apparatus to which the present invention is applied, and FIGS. 2 and 3 show one embodiment of an illuminance unevenness correction member (light shielding member) and another embodiment, respectively. This is an example. /...Film, e2. ...projection lens. 3.'l...Moving optical system, 5...Photoreceptor. B: Light shielding member, 7: Exposure slit. Patent applicant: Canon Co., Ltd. Figure 3

Claims (1)

[Claims] An optical scanning exposure device having an exposure slit and in which the angle of incidence of a light beam on a photoreceptor changes as a document is scanned, characterized in that a fixed light shielding member is disposed parallel to the longitudinal direction of the slit. Optical scanning exposure device.