JPH0253792B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact scanning exposure type copying apparatus that has a scanning mirror on the image field side and is capable of variable magnification.

Conventionally, in a slit exposure scanning type copying machine, the original is fixed and two scanning mirrors are placed on the object side, that is, in the optical path, between the original surface and the projection lens, and are parallel to the original surface with a relative ratio of 2:1. A device that moves with a hand is known from US Pat. No. 330,181 and other publications.

By the way, it is desirable for the moving speed of the photoreceptor to always remain constant even when the copying magnification is changed due to processes such as paper feeding and development. The absolute speeds of the two scanning mirrors on the field side must be varied.

That is, when the peripheral speed of the photoreceptor is v ₀ and the magnification is m, the first scanning mirror near the document surface side and the second scanning mirror near the projection lens side in the optical path each have v ₀ /m,
The moving speed is v ₀ /2m, and the absolute speed changes every time the magnification is changed. Therefore, as a system in which the moving speed of the scanning mirror is always kept constant even when the magnification is changed, the original is fixed and two scanning mirrors are installed on the image field side, that is, between the projection lens and the photosensitive surface, and the scanning mirrors are moved in a predetermined direction. JP-A-53-102041, which moves at a constant speed,
It is known from Japanese Patent Application Publication No. 54-122132, Utility Model Application Publication No. 54-52233, etc. In all of these, the light incident on the photoreceptor is perpendicular to the surface of the document.

Here, if you want to change the direction of the incident light on the photoconductor due to the optical arrangement, for example, for a system where the light enters the photoconductor from the lateral direction parallel to the document table, use a fixed mirror to bend the optical path. Is required.

Generally, if the total number of mirrors in the optical path is an odd number, the image projected onto the photoreceptor will be a mirror image, and in order to form a normal image, it is necessary to make the total number of mirrors in the optical path an even number.

That is, in addition to the two scanning mirrors on the image field side,
Furthermore, at least two mirrors are required for bending the optical path, which hinders miniaturization of the device.
Furthermore, an increase in the number of mirrors is also undesirable from the standpoint of light loss due to reflection.

It is an object of the present invention to solve the above-mentioned problems and provide a compact scanning exposure type copying apparatus that uses only two scanning mirrors and in which the incident light path to the photoreceptor is parallel to the photoreceptor. do. The purpose of this is to provide a scanning exposure type copying device capable of projecting the surface of a document at variable magnification.
It has a second scanning mirror, and is arranged so that the optical path of incidence to the first scanning mirror and the optical path of output from the second scanning mirror intersect, and the first and second scanning mirrors are
The first,
The intersection point of the second scanning mirror is relative to the document surface.
This is achieved by moving in a 45° direction.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an optical explanatory diagram of a conventional scanning exposure type copying apparatus. A document surface 1 is projected onto a photosensitive drum 2 by a fixed projection lens 3. A light flux regulating member 4 for regulating the slit width is disposed near the photosensitive drum 2 in the optical path. Further, in the optical path, a scanning mirror 5 is disposed between the projection lens 3 and the photosensitive drum 2.
5' is disposed, and these scanning mirrors 5, 5' move parallel to the document surface 1 at a speed of 1/2 of the circumferential speed of the photosensitive drum 2 to slit scan the document surface 1. Further, when changing the magnification, the scanning mirrors 5 and 5' are initially displaced perpendicular to the document surface 1 to correct the optical path length accompanying the magnification conversion.

Once the initial position is set, the scanner moves parallel to the original surface 1 at the same speed as when it is at the same magnification, and scans the original surface 1 through the slit.

FIG. 2 shows an embodiment of the invention.

The scanning mirrors 6, 6' form an angle of 45 degrees and move in a predetermined direction relative to the document surface 1. scanning mirror 6,
6', the optical path intersects at right angles and enters the photoreceptor 2 almost parallel to the document surface 1. When changing magnification, the scanning mirrors 6 and 6' are initially displaced in a direction perpendicular to the direction of movement during scanning, correcting the optical path length due to magnification conversion, and then displacing the mirrors 6 and 6' in the same direction as the direction of movement before changing magnification. It moves at the same speed and scans the document surface 1 through the slit.

Next, in FIG. 3, the moving direction of the scanning mirrors 6, 6',
Explain the distance traveled.

Now, if only the scanning mirror 6 is moved by a distance d along the output optical axis, ΔPQR becomes an isosceles triangle according to the law of reflection, PR = PQ = d, the output optical axis moves downward by d sin α, and the image The surface is d+d
Move to the right by cos α.

Next, if mirror 6' is similarly moved by d' along the input optical axis, the optical axis exiting mirror 6' will be further
Moves downward by d′ sin β, and the image plane is d′+d′ cos
Move upward by β.

As a result, the image plane movement amount Δ becomes as follows.

Δ=(d+d cos α)−(d′+d′ cos β) In order to realize an image field scanning system, Δ=0 must be satisfied.

That is, d'=1+cos α/1+cos β×d (1) Also, since the angle of the scanning mirrors 6 and 6' is 45°, the following equation holds true.

α＋β＝90゜……(2) From (1) and (2), the following equation holds true.

d'=2d/(1+tan α/2) ² ...(3) By the way, what has been described above is to move the scanning mirror 6 from point P in the direction of point Q in FIG. When the mirror is moved from the point Q toward the point R, that is, when it is moved in the direction of displacement of the reflection point, the size of the mirror becomes minimum.

Furthermore, it is also possible to move the scanning mirrors 6, 6' integrally in the same direction. Scanning mirror 6, 6'
It is assumed that an intersection point S moves to a point T while maintaining the relative relationship between the scanning mirrors 6 and 6'.

Here, the trajectory from point S to point T will be considered in two stages.

That is, it is assumed that point S moves perpendicularly to the document surface 1 to point U, and from point U to point T in the setting direction of the scanning mirror 6'.

Here, SU=d′.

If TU=x, then TW=x cos β/2, WV=d−x cosβ/2, UW=x sinβ/2, SW= d′−x sinβ/2, WV/SW=tanα/2, so x= √2(d cosα/2−d′ sinα/2) Also, from (3), x=√2/−d/cosα/2(1+tanα/2
) ² ...(4) That is, from point S to point U, 2d/(1+tanα/2) ² , and from point U to point T, √2/-d/cosα/2(1+tan
α/2) It is sufficient to move only ² in one piece.

Incidentally, when α=β=45°, ST=SU=d′ moves the document surface 1 in the direction of 45°. In other words, two scanning mirrors are integrally constructed with an included angle of 45°,
If the intersection of the two scanning mirrors is moved in a direction of 45 degrees with respect to the document surface, it becomes possible to linearly move the two scanning mirrors integrally. Incidentally, the scanning area L is given by the following equation.

L=d sinα+d′ sinβ=2d/1+tanα/2...
...(5) Incidentally, when α=β=45°, the scanning mirror moves integrally by L/√2.

Next, FIGS. 4 and 5 show the scanning mirror 6 during magnification change,
6' initial displacement is shown.

Generally, when the optical axis length on the object side is a, the optical axis length on the image field side is b, the magnification is m, and the fixed focal length of the lens is f, the following equation holds true.

1/a+1/b=1/f b/a=m From this, a=f(1+1/m) b=f(m+1) From this, when changing magnification, the object world side optical axis length and the image field side optical axis length are There is a need to change together.

The former can be achieved by initially displacing the lens by a predetermined distance in the optical axis direction, and the latter by initially displacing the scanning mirror by a predetermined distance in a direction perpendicular to the scanning direction. Once the initial position is determined, the scanning mirror moves at the same speed as before the magnification change, thereby performing slit exposure scanning during the magnification change. If the projection lens is replaced with a projection lens having a different focal length or a zoom lens with a variable focal length is used as the projection lens, the initial position of the scanning mirror during zooming does not need to be changed.

Hereinafter, the amount of mirror displacement during zooming will be described quantitatively, assuming that the angle between the two scanning mirrors is θ.

In Figure 5, the incident ray and the outgoing ray are
Let the intersection of the two mirrors be X, and consider a symmetrical system.

If <A×B=θ, then the following equation holds true using the law of sine for ΔXBC.

= BC/tan θ/2 Also, using the law of sine for ΔABC, the following equation holds true.

=2·cosθ Here, considering the optical path length L=++, the following equation holds true.

L=2・sinθ In other words, if the mirror intersection point X is moved away by δ from the extension to the position of .

As described above, according to the present invention, it is possible to provide a compact scanning exposure type copying apparatus capable of variable magnification in which the incident and reflected optical paths of two scanning mirrors on the image field side intersect.

[Brief explanation of the drawing]

FIG. 1 is an optical explanatory diagram of a conventional scanning exposure type copying apparatus, FIG. 2 is a diagram showing an embodiment of the scanning exposure type copying apparatus according to the present invention, and FIG. 3 is a diagram illustrating the principle of the present invention. FIG. 4 is an optical explanatory diagram when changing the magnification according to the present invention, and FIG. 5 is an explanatory diagram of the mirror displacement amount when changing the magnification according to the present invention. In the figure, 1 is a document surface, 2 is a photoreceptor, 3 is a projection lens, 4 is a light flux regulating member, and 5, 5', 6, and 6' are scanning mirrors.

Claims (1)

[Claims] 1. A scanning exposure type copying apparatus capable of projecting the surface of a document at variable magnification, which has first and second scanning mirrors in the optical path between a projection lens and a photoreceptor, and has an optical path of incidence on the first scanning mirror and a second scanning mirror. The output optical paths from the scanning mirrors are arranged so as to intersect, and the first and second scanning mirrors are integrally formed with an included angle of 45°, and the intersection of the first and second scanning mirrors A scanning exposure type copying apparatus, wherein the scanning exposure type copying apparatus moves in a direction of 45 degrees with respect to the original surface.