JP2510528B2 - Scanning exposure system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a scanning exposure system of a fixed platen type copying machine.

[Prior art]

Conventionally, a scanning system having a relatively long object-image distance requires a large space for its optical system. Therefore, it is difficult to make the machine body compact. Further, in the mirror moving type optical device, since the moving amount thereof is closely related to the moving amount of the photoconductor, it often requires a very complicated device to control the independently moving mirrors. .

[Object of the Invention]

It is an object of the present invention to effectively use the space of a scanning system within a limited range, thereby reducing the space inside the machine body and achieving miniaturization.

Moreover, it is considered that the mirror can be moved while being deeply involved in the driving of the photoconductor and the complexity of driving the apparatus can be suppressed.

In the scanning exposure system according to the present invention, the scanning system provided between the lens and the photoconductor is composed of three mirrors M1, M2 and M3 from the lens side. In the scanning exposure system, the constant chief ray path length between the mirror M1 and the mirror M2 is IH, and the chief ray path on the optical axis of the lens between the pupil of the lens and the mirror M2. When the length is BH and the half angle of view of the lens is θ, the mirror M1 moves on a curved orbit r with r = −IH + BHsecθ with the pupil of the lens as an origin, and the mirror M2 and the mirror TR is a constant principal ray optical path length with respect to M3, and K is a principal ray optical path length on the optical axis of the lens between the image forming point of the lens on the photoreceptor and the mirror M2.
R, and the half angle of view of the lens is θ, the mirror M3
Moves on a curved orbit r ′ with r ′ = − TR + KRsec θ with the image forming point of the lens on the photoconductor as an origin, and the mirror M2 moves while the mirror M1 and the mirror M3 move. The principal ray optical path length between the mirror M1 and the mirror M2 is fixed to the IH, and the principal ray optical path length between the mirror M2 and the mirror M3 is moved to a straight line kept at the constant TR. By doing so, the above objectives will be achieved.

[Explanation of Structure and Operation of Invention]

FIG. 1 is a diagram showing one embodiment of the scanning exposure system according to the present invention, and FIG. 2 gives a special length relationship to the scanning exposure system shown in FIG. It is a figure which shows the simplified scanning exposure system. First, in FIGS. 1 and 2, B
Is the exit pupil of the lens L, BP is the optical axis, and OPQ is the tentative image forming plane of the lens. Moreover, although the drawing is drawn symmetrically with respect to the optical axis, it is not necessary that OP = PQ. ED
Is a trajectory of the first mirror M1, the third mirror M3, and the second mirror M2 that moves while keeping the principal ray optical path length constant, and is given by a straight line in the figure. Further, D indicates the position of the second mirror M2, and the reflecting surface need not be perpendicular to the orbit (in the case of FIG. 1). Furthermore, the ED is drawn with an inclination of 45 ° with respect to the optical axis PB, but this is not a limitation. Also, Is M1, Is the orbit of M3. K'represents an image forming point on the photosensitive pair.

Next, the scanning exposure system according to the present invention will be described in detail with reference to FIG. In Fig. 1, the optical system B-OPQ is shown on the surface JHK.
Now, split into B-JHK and JHK-QPO. Face JHK is a plane,
In FIG. 1, a plane perpendicular to the optical axis BP is given in order to simplify the explanation. First, the chief ray of each ray passing through the split surface JHK is set to have a fixed length in the front and back from the split surface JHK, that is, KG = HI = JF, KY = HX = JW, and the end points are taken. A locus formed by connecting them think of. At this time, the curve Is given as the orbit of M1 as it is, and M2 always moves on the axis DE such that the optical path length of the chief ray from M1 is kept constant at GK during the movement of M1. This makes it possible to associate the point on the split surface JHK with the mirror M2 at the moving point D on the axis DE. Next, a fixed length KY (= HX =
JW), Orbit of M3 corresponding to think of. this is, How to obtain the shape of and the arrangement in the optical system will be described later. In a way that will be described later, To determine WO, XP, YQ as U'K ', T'K', S '
It is possible to collect at K'-points while equalizing K '.

As a result, the main scanning system can equalize the optical path length to the temporary image forming point OPQ on the left side and the optical path length to the image forming point K'on the photoconductor on the right side of the following equation.

BG + GD + DU '+ U'K' = BG + GK + KY + YQ It is clear that similar relational expressions can be obtained for other points.

Next, regarding the angle of the mirror, when the mirror M1 reflects the light beam incident from the pupil B toward the mirror M2 while moving, in FIG. The inclination of the reflecting surface is changed so as to coincide with the bisector of the apex angle of the isosceles triangle GKD. Also, BG, GK, KY, Y
When Q is not in a specific length relationship, the axis DE and the fixed reflecting surface of the mirror M2 are generally not perpendicular. If they are made vertical, the optical axes BI and T'K 'are not symmetrical with respect to the axis DE. However, both cases are feasible. Also,
The reflecting surface of the mirror M3 moves the light ray arriving from the mirror M2 toward K ', changing the inclination in the same manner as the mirror M1 so as to reflect the light ray.

Next, the orbits of the mirrors M1 and M3 will be shown using mathematical expressions. In FIG. 1, the trajectory of the mirror M1 is obtained. For the sake of simplicity, if the split surface JHK is a plane with the optical axis BP as the normal, and the mirror M2 moves on a linear orbit, then B is the origin of the polar coordinates and θ is the half angle of view of the lens L. The time division plane JHK is represented by BHsecθ. Therefore, by subtracting a constant chief ray path length IH from that, the trajectory r of the mirror M1
Is r = -IH + BHsecθ. Next, decide the position and inclination of the axis DE appropriately,
The D corresponding to each point on the trajectory r is determined. next, Orbit of mirror M3 corresponding to The method of determining is described. As shown in Fig. 1, BK ≠ KQ
When Orbital length of is different, and when GK ≠ KY, When The orbital shapes of should be different. Therefore, the orbit is determined using FIG. Figure 3 is a rewrite of the trapezoid JKQO in Figure 1. Now, a straight line is drawn from the point K in parallel with JO, and the alternating current with the image plane OPQ is V. At this time, if ΔKVQ is subjected to the same operation as when the orbit r was previously obtained from ΔBJK, it is obvious that the orbit r ′ of the mirror M3 is naturally expressed as r ′ = − TR + KRsecθ. Where R is from K
It is a foot of a vertical line drawn on VQ, and U, T, S correspond to U ', T', S'to be obtained, respectively. And the figure K'-U'T '
S'is congruent with K-UTS, which can be made here. Also, K-UTS
The method for arranging K'-U'T'S 'is not uniquely determined by the inclination of the reflecting surface of the mirror M2.

In FIG. 1, BI and T'K 'are chosen to be symmetrical with respect to the axis DE. The selection method as shown in FIG. 2 realizes the simplest shape. This is shown in FIG.
IH = HX, BH = HP with the inclination of DE relative to the optical axis BP of 45 °
And the reflecting surface of the mirror M2 is perpendicular to DE. At this time, the mirrors M1 and M2 move symmetrically with respect to the trajectory DE, and therefore 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, 1a is a side plate fixed to the mirror 1, and 2, 3 and 4 are guide grooves. Reference numeral 6 denotes a member for supporting a mirror by inserting a pin (not shown) into a hole (not shown) provided in the central portion of the side plate 1a of the mirror. The mirror 1 is pivotally supported in a direction indicated by an arrow A1 about this pin (not shown) as a pivot shaft. Reference numeral 7 denotes a guide rod, and the mirror support member 6 is swingably provided along the guide rod. A pin 9 is fixedly mounted on the guide rod 7, and the pin 9 is fitted in the guide groove 2. The guide groove 2 has a shape that guides the mirror 1 in a straight line in the lateral direction A2, and the guide rod 7 is moved at a constant speed (constant speed) along the guide groove 2 by a driving means (not shown). To be Reference numeral 10 is a pin fixed to the mirror support member, and the pin 10 is fitted in the guide groove 3. The guide groove 3 is shown in FIG. 1 and FIG. When the guide rod 7 moves in the left-right direction A2 in the guide groove having a shape as shown by, the mirror 1 moves in the up-down direction A3 along the shape of the guide groove. Reference numeral 11 is a pin fixed to the end of the side plate 1a of the mirror 1, and the pin 11 is fitted in the guide groove 4. The guide groove 4 has such a shape that the tilt angle of the mirror 1 is changed so that the incident principal ray is always reflected in a desired direction while the mirror 1 is moving. Hence the mirror 1
When the guide rod 7 moves to A2, it swings around a pin (not shown) of the mirror support member 6 according to the shape of the guide groove.

FIG. 5 is a diagram showing an embodiment of a moving mechanism of the mirror M2 shown in FIGS. 1 and 2. In the figure, the same reference numerals as those in FIG. 4 represent the same members. 12 is the side plate 1a of the mirror
This is a mirror support member fixed to the center of the member, and the member 12 is provided so as to be swingable in the direction indicated by arrow A4 with respect to the fixed guide rod 13. The guide rod 13 is the same as that shown in FIGS.
It is a member corresponding to the axis DE shown in the figure. 4 and 5
The member 5 shown in the figure is a connecting rod that connects the mirrors M1 and M2 and the mirrors M2 and M3 and has a constant length. Connecting rod 5 is mirror M1, M
3, the pin 10 is rotatably provided on the pin 10 about the pin 10 as shown in FIG. 4, while the mirror M2 has a pin 14 fixed to the member 12 as shown in FIG. It is provided so as to be rotatable in the direction indicated by arrow A5 about the axis. In this manner, the connecting rod 5 is rotatably provided at both ends thereof with respect to the pins 10 and 14 provided near the center of the mirror. Therefore, when the mirror M1 and the mirror M3 are moved by the driving means, the optical path lengths of the principal rays between the mirrors M1 and M2 and between the mirrors M2 and M3 are maintained at the values determined by the length of the connecting rod 5. First, the mirror M2 moves along the guide rod 13. Therefore, when the mirrors M1 and M3 move, the angle w formed by the two connecting rods 5 shown in FIG. 5 changes. In this way, the fourth
In the moving mechanism shown in FIGS. 5 and 5, the mirrors M1, M2 and M3 are moved to the first position.
It can be moved along the movement locus shown in FIGS.

The scanning exposure system according to the present invention includes the above-mentioned mirrors M1, M2, M3.
It is possible to give various arrangement degrees of freedom to the arrangement. FIGS. 6A and 6B are movement trajectories of the mirrors M1 and M3 when the trajectory DE of the mirror M2 is moved so as to be parallel to the optical axis BP of the lens L. It is a figure which shows the outline of. As described above, the present invention has an effect that the arrangement of the scanning system can be selected with a large degree of freedom because of the space arrangement with the system other than the scanning system.

As described above, as is apparent from FIG. 1, it is possible to combine an optical system having a large space of V-PQR with various degrees of freedom in a space-saving manner. Further, since the drive system and the arrangement of the photoconductor and the like also have sufficient adaptability, the image plane can be reproduced on the photoconductor without causing an optical path difference. Furthermore, the complicated movements between the mirrors are relatively easy to realize under the condition that the optical path length of the chief ray is constant, and the mirrors can be driven at a constant speed. It has the effect that it is also easy to realize synchronization.

[Brief description of drawings]

FIGS. 1 and 2 are diagrams showing an outline of an optical path of an embodiment of a scanning exposure system according to the present invention, and FIG. 3 is a diagram showing a trajectory of a mirror M3, FIGS. 4 and 5 FIG. 6 is a diagram showing an embodiment of a mirror moving mechanism of a scanning exposure system according to the present invention, and FIGS. 6A and 6B are schematic diagrams of another embodiment of the scanning exposure system according to the present invention. L ... Lens, BP ... Optical axis, M1, M2, M3 ... Moving mirror, ...... Orbit of mirror M1, DE …… Orbit of mirror M2, ... Orbit of the mirror M3.

Claims (1)

(57) [Claims] 1. A scanning exposure system in which a scanning system provided between a lens and a photoconductor is composed of three mirrors, a mirror M1, a mirror M2, and a mirror M3 from the lens side, The constant chief ray path length between the mirror M1 and the mirror M2 is IH, the chief ray path length on the optical axis of the lens between the lens pupil and the mirror M2 is BH, the lens half When the angle of view is θ, the mirror M1 moves on a curved orbit r with r = −IH + BHsec θ with the pupil of the lens as an origin, and a constant main distance between the mirror M2 and the mirror M3. TR is the ray path length, KR is the principal ray path length on the optical axis of the lens between the image point of the lens on the photoreceptor and the mirror M2,
When the half angle of view of the lens is θ, the mirror M3
Moves on a curved orbit r ′ with r ′ = − TR + KRsec θ with the image forming point of the lens on the photoconductor as an origin, and the mirror M2 moves while the mirror M1 and the mirror M3 move. The principal ray optical path length between the mirror M1 and the mirror M2 is fixed to the IH, and the principal ray optical path length between the mirror M2 and the mirror M3 is moved to a straight line kept at the constant TR. A scanning exposure system characterized by: