JPS6366552A - Scanning exposure system - Google Patents

Abstract

PURPOSE:To reduce the space of a scanning system to make a device compact by constituting the scanning exposure system of three mirrors which can be moved while keeping the optical path length of a principal beam constant. CONSTITUTION:The scanning exposure system consists of three mirrors M1, M2, and M3 which are moved while keeping the optical path length of the principal beam constant. In such a case, the trajectories of mirrors M1-M3 describe an arc FIG, an arc S'T'U', and a line DE, respectively. A guide bar 13 is used as a member for the axis DE, and mirrors M1 and M3 and mirrors M2 and M3 are connected by connecting bard 5 having a certain length for the purpose of describing these trajectories by mirrors M1-M3. When mirrors M1 and M3 are moved, the optical path length of the principal beam between mirrors M1 and M2 and mirrors M2 and M3 is kept at a value determined by the length of connecting bars 5; and thus, the space of the scanning exposure system is reduced to make the device compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a scanning exposure system for a copying machine with a fixed document table.

[Prior art]

Conventionally, a scanning system with a relatively long object-to-image distance has required a large space for its optical system. Therefore, it was difficult to make the machine body compact.

In addition, in mirror-moving optical devices, the entire radial movement is closely related to the amount of υ movement of the photoreceptor, so a very complicated swing is required to control the independently moving mirror.
There were a lot of things.

(Object of the Invention) The present invention effectively saves space in a scanning system within a limited range.
The purpose is to reduce the space inside the machine body and make it more compact.

In addition, consideration was given to making it possible to keep the mirror stationary while being deeply involved in driving the photoreceptor, thereby reducing the complexity of driving the device.

In the scanning exposure system of the present invention, the above object is achieved by configuring the scanning exposure system with three mirrors that move from the female while keeping the optical path length of the principal ray constant. be.

[Description of the structure and operation of the invention]

FIG. 1 is a diagram showing an embodiment of the scanning exposure system according to the present invention, and FIG. 2 shows a special length relationship for the scanning exposure system shown in FIG. 1 to make the system shown in FIG. 41 is a diagram showing a simplified scanning exposure system. First, in Figures 1 and 2, B
is the exit pupil of the lens L, BP is the optical axis, and OPQ is the temporary imaging plane by the lens. Furthermore, although the diagram is drawn symmetrically with respect to the optical axis, it is not necessary that 0P=PQ. ED is the trajectory of the second mirror M2 that moves while keeping the principal ray optical path length constant with the first mirror M1 and the third mirror M3, and is given by a straight line in the figure. Also, D is
The position of the second mirror M2 is shown, and the reflective surface need not be perpendicular to the trajectory (as in Figure 1). Furthermore, ED
is drawn with an inclination of 45° with respect to the optical axis PB,
This is not limited either. Also, 1 gun) is Ml,
r〒view is the orbit of M3. Further, Bi represents an image forming point on the photoreceptor.

Next, the scanning exposure system according to the present invention will be described in detail with reference to FIG. In Figure 1, first, optical system B-OPQ is placed on plane J.
HK is divided into B-JHK and JHK-QPO. Face J
There is no restriction that HK has to be flat, but in Figure 1, for the sake of simplicity, we use light! IIIhBP
given as a plane perpendicular to . First, the chief ray of each ray passing through the dividing plane JHK is set to have a constant length from the dividing plane JHK, that is, KG=HI=JF, KY
Consider the endpoints so that =HX=JW, and the trajectories rtc, fma) created by connecting them. At this time, the curve f〒
) is given as the orbit of Ml, and M2 is Ml
While moving, the beam always moves along the axis DE such that the optical path length of the chief ray from Ml is kept constant at GK. This makes it possible to associate the point on the dividing plane JHK with the mirror M2 located at the moving point on the axis DE. Next, consider S' with a constant length KY (=HX=JW) from each moving point and the trajectory σ of M3 corresponding to v''C1WxY. This is not equal to Q. [Shape of convex' How to obtain σ and how to arrange it in the optical system will be described later.If σ〒〕′ is determined by the method described later, wo, xp.

It becomes possible to make YQ equal to 1fK, τ', and S'l and gather them at one point.

As a result, this scanning system can make the optical path length to the temporary imaging point OPQ on the left side of the following equation equal to the optical path length to the imaging point K on the photoreceptor on the right side.

BG+GD+D+1fK:' =BG+GK+KY+YQ It is obvious that similar relational expressions can be obtained for other points as well.

Next, regarding the angle of the mirror, mirror M1 is designed to reflect the rays of light incident from pupil B toward mirror M2. The reflective surface is 2 of the apex angle of the isosceles triangle GKD.
Change the slope to match the equal dividing line.゛Also, B
G.G.K.

When KY and YQ do not have a specific length relationship, the fixed reflective surfaces of the support DE and the mirror M2 are generally not perpendicular.

If they were made vertical, the optical axes Bl and τ would not be symmetrical with respect to the axis DE. However, it is possible to implement in either case. Further, the reflecting surface of the mirror M3 moves while changing its inclination in the same manner as the mirror M1 so as to reflect the light beam arriving from the mirror M2 toward I(.

Next, the trajectories of mirrors M1 and M3 will be shown using mathematical expressions. In FIG. 1, the trajectory of mirror M1 is determined. For simplicity, if we assume that the dividing plane JHK is a plane with the optical axis BP as its normal, and that the mirror M2 moves on a straight trajectory, then when B is the origin of the polar coordinates and θ is the half angle of view, The dividing plane JHK is represented by BHsecθ. Therefore, by subtracting the constant chief ray optical path length IH from there, the trajectory r of the mirror M becomes r=-IH+BHsecθ. Next, the position and inclination of the axis DE are determined appropriately, and D corresponding to each point on the orbit r is determined. next,
A method for determining the trajectory tJ'"r's' of mirror M3 corresponding to WXY will be described. As shown in Fig. 1, BK≠K
At the end of Q, the orbital lengths of f〒) and f〒1' are different, and G
When Kf=KY, the trajectory shapes of FIG and σ〒]' should be different. Therefore, the trajectory is determined using Fig. 3. Figure 3 is a redrawn version of the trapezoid JKQO in Figure 1.

Now, draw a straight line parallel to JO from point K and let V be the alternating current with the image plane OPQ.At this time, if we apply the same scanning to △KVQ as we did when finding the orbit r from △BJK, the mirror will naturally appear. M3's Ichikudo r' (Ma, r'=-TR+KRse
It is clear that it is expressed as c θ . Here, R is the leg of the perpendicular line drawn from K to VQ, and U, T.

S corresponds to σ, f, and S' to be determined, respectively. And the shape knee 1f'T'S' can be done here - UTS
It is joint with. In addition, the method of arranging K-UTS at '-U' and S' is due to the inclination of the reflecting surface of mirror M2.
Not determined.

In Fig. 1, Bl and τ () are selected to be symmetrical with respect to IFthDE.The selection method shown in Fig. 2 realizes the simplest shape. , the inclination of DE with respect to the optical axis BP is set to 45@, and I
H=HX, BH=HP, and mirror M
This is the case where the reflecting surface of No. 2 is perpendicular to DE. At this time, the mirrors M1 and M2 move symmetrically with respect to the orbit DE, so the axis DE becomes the axis of symmetry of the main scanning system.

FIG. 4 is a diagram showing an embodiment of a moving mechanism for the mirrors M1 and M3. In the figure, 1 is a mirror, la is a side plate fixed to the mirror 1, and 2, 3.4 are guide grooves. Reference numeral 6 denotes a member that supports the mirror by inserting a pin (not shown) into a hole (not shown) provided in the center of the side plate [a] of the mirror. The mirror 1 is pivotally supported so as to be swingable in a direction not shown by an arrow A1 using this pin (not shown) as a swing axis. 7 is a guide rod, and the mirror support member 6
is provided slidably along this guide rod.

A pin 9 is fixed to the guide rod 7, and the pin 9
is fitted with the guide, *1η2. The guide groove 2 has a shape that guides the mirror 1 in a straight line in the direction A2, and the guide rod 7 is moved at a constant speed (uniform speed) along the guide groove 2 by a driving means (not shown). I am made to do so. A pin 10 is fixed to the mirror support member, and the pin 10 is fitted into the guide groove 3. The guide groove 3 has a shape as shown by r-re, 1) in Figs. 1 and 2, and when the guide rod 7 moves in the left-right direction A2, it follows the shape of this kite groove. Mirror 1 is in vertical direction A
Move to 3. A pin 11 is fixed to the end of the side plate 1a of the mirror 1, and the pin 11 is fitted into the guide groove 4. The guide groove 4 has a shape that changes the inclination angle of the mirror 1 so that the incident chief ray is always reflected in the desired direction while the mirror 1 is moving. Therefore, when the guide rod 7 moves to A2, the mirror 1 follows the shape of the guide groove.
The mirror support member 6 swings around a pin (not shown).

FIG. 5 is a diagram showing an embodiment of the mobile unit +l'IJ of mirror M2 shown in FIGS. 1 and 2. FIG. In the figure, the same reference numerals as in FIG. 4 represent the same members. 12 is a mirror support member fixed to the center of the side plate 1a of the mirror;
The member 12 is provided so as to be slidable in the direction indicated by arrow A4 with respect to a fixed kite rod 13. The guide rod 13 is a member corresponding to the glaze DE shown in FIGS. 1 and 2. A member 5 not shown in FIGS. 4 and 5 is a connecting rod of constant length that connects the mirrors M1 and M2 and the mirrors M2 and M3. The connecting rod 5 is rotatably attached to the pin 10 on the mirrors M1 and M3, as shown in FIG. It is provided so as to be rotatable in the direction shown by arrow A5 about a pin 14 fixed to member 12 as an axis. Connecting rod 5 like this
Both ends of the mirrors are rotatably provided with respect to pins 10 and 14 provided near the center of each mirror. Therefore, mirror? , (When mirror 1 and mirror 13 are moved by the driving means, the optical path length of the chief ray between mirrors M1 and M2 and between M2 and M3 is
The mirror M2 is guided by the guide 'p' so as to maintain the value determined by the length of the mirror M2.
J13). Therefore, when mirror M1 and mirror M3 move, the angle W of the two connecting rods 5 shown in FIG. 5 changes. In this way, with the moving mechanism shown in FIGS. 4 and 5, the mirror 11. M2. M3 can be moved eight times along the trajectory shown in FIGS. 1 and 2.

The scanning exposure system according to the present invention includes the mirror M1. M2
．． It is possible to give two degrees of freedom to the arrangement of M3, such as t, X, etc. Figure 6(a).

(b) shows mirror M1 when moving it so that it is parallel to the φ entry DE of mirror M2 or the light @BP of lens L.
．． FIG. 3 is a diagram schematically showing a hexakinetic trajectory (Ω, Ω′) of M3.

As described above, the present invention has the effect that the arrangement of the scanning system can be selected with a large degree of freedom due to the space arrangement with other systems other than the scanning system.

As explained above, as is clear from FIG. 1, it is possible to package an optical system that includes various degrees of freedom and takes up a large space, such as the V-PQR, in a space-saving manner. It also has sufficient adaptability to the drive system and the arrangement of photoreceptors, etc., allowing the image surface to be reproduced on the photoreceptor without creating an optical path difference. Furthermore, the movement between the mirrors in the multi-PIE is relatively easy to realize under the condition that the principal ray optical path length is constant.
Since the mirror can be driven at a constant speed, synchronization with the drum can also be achieved easily.

[Brief explanation of drawings]

1 and 2 are diagrams schematically showing the optical path of an embodiment of the scanning exposure system according to the present invention, FIG. 3 is a diagram illustrating the trajectory of the mirror M3, and FIGS. FIGS. 6(a) and 6(b) are schematic diagrams of other embodiments of the scanning exposure system according to the present invention. FIGS. L-lens, BP-optical axis, Ml, M2. M3 - moving mirror, [〒) - trajectory of mirror M1, DE - trajectory of mirror M2, q〒1' - trajectory of mirror M3.

Claims (1)

[Claims] (1) A scanning exposure system characterized by being composed of three mirrors that move while keeping the optical path length of the chief ray constant.