JPS636861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compact slit exposure type optical scanning device in which an original and a lens are fixed and a scanning system is provided on the image field side.

2. Description of the Related Art Conventionally, in slit exposure scanning type copying machines, there are those that have a scanning system on the object world side and those that have a scanning system on the image field side. Here, the object world side is the area from the document to the lens in the optical path, and the image field side is the area from the lens to the photoreceptor.

Examples of the former are Tokuko No. 6647, 1976, and Jikko No. 54.
-6456, etc., and as an example of the latter, the
- No. 30013, Actual Publication No. 13075, Special Publication No. 13075 -
No. 10259, Special Publication No. 13474, No. 102041, No. 102041
There are numbers etc. Generally, if there is a scanning system on the object world side, it is necessary to change the moving speed of the scanning system according to the copying magnification, but if there is a scanning system on the image field side, the moving speed of the scanning system does not depend on the copying magnification. It can be kept constant. By the way, regarding the conventional example in which the scanning system is located on the image field side, Japanese Patent Publication No. 46-30013 has the problem that it requires a lens with a wide angle of view because it cannot use the vicinity where the chief ray coincides with the optical axis. Also, Jikoko 46
-No. 13075, Special Publication No. 10259, Special Publication No. 10259, Special Publication No. 10259-
No. 13474 involves rotational movement as well as translational movement, making it mechanically complex. By the way, Tokukai Akira
No. 53-102041 discloses that a lens with a maximum angle of view relative to the optical axis that is approximately half that of Japanese Patent Publication No. 46-30013 is sufficient, and that the scanning system on the image field side only needs to be moved linearly. However, since the reflection points of the two reflecting mirrors that make up the image-field side scanning system change every moment during scanning, it is necessary to make the effective part of the reflecting mirror larger, and the dead space ( This poses a problem in that a dead space (dead space) must be secured and the weight increases, which is disadvantageous for scanning.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact slit exposure type optical scanning device having a scanning system on the image field side, which solves these problems.

The purpose of this is to move the supports of the two small reflecting mirrors constituting the image field side scanning system at a constant speed in a predetermined linear direction, and to move the two small reflecting mirrors along quadratic curves accordingly. This is achieved by moving non-uniformly.

The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows an optical system disclosed in Japanese Patent Application Laid-open No. 102041/1983, which is a conventional example using a scanning system on the image field side.

The angle between the incident optical axis of mirror M ₁ (M ₁ A, M ₁ B, M ₁ C) and the exit optical axis of mirror M ₂ (M ₂ A, , M ₂ B, M ₂ C) is θ. If the circumferential speed of the body is U ₀ ,
The scanning mirrors M ₁ and M ₂ are integrally moved translationally in the O _A O _B O _C direction, that is, in a direction making an angle of 90° + θ/2 with the incident optical axis, at a constant velocity of Uo/2 cos θ/2. Here, since mirrors M ₁ and M ₂ move translationally as a unit, the reflection points change to A ₁ , B ₁ , C ₁ for mirror M ₁ , and A ₂ , B ₂ , C 1 for mirror M ₂ . Changes to ₂ . It can be seen from this that it is necessary to make the effective part of the mirror larger.

By the way, the coordinates of the intersection of the mirror and the principal ray are calculated below.

The optical axis is the y-axis, and the image plane when there is no mirror is the x-axis. The scanning image points are A(h, o), B(o,
o), C(-h, o). Further, the pupil of the lens on the photoreceptor side is assumed to be (O, L). The image points A, B, and C are aligned with the photoreceptor slit position D by the scanning mirror system. The intersection of the chief ray reaching the image point A and the mirror M ₁ A is A ₁ (X ₁ , y ₁ ), and the intersection with the mirror M ₂ A is A ₂ (X ₂ ,
y ₂ ), and similarly, let B ₁ (o, l) and B ₂ be the intersections of the principal ray and the mirror that reach the image point B, and let C ₁ and C ₂ be the intersections of the principal ray and the mirror that reach the image point C. Further, the angle of incidence of the incident optical axis on mirror M ₁ is defined as i ₁ , and the angle of incidence on mirror M ₂ as i ₂ . Here, (180°−2i ₁ ) + (180°−2i ₂ )+
θ=180°. Intersection 0 of mirror M ₁ and mirror M ₂
The movement distance of (0 _A , 0 _B , 0 _C ) is 0 _A 0 _B = h/2 cos θ/2 for the scanning distance h from image point A to image point B, which is θ/2 tilted to the x axis. Moving.

The formula for mirror M ₁ A is = 0 _A 0 _B = h/2cosθ/2 The equation of the principal ray at image point A is y=-L/hX+L. Therefore, the intersection A ₁ (X ₁ , y ₁ ) is as follows.

Here, if we eliminate h _, we get y ² ₁ - (L ₊ l + X ₁ tan i ₁ ) y ₁ + L {1/2 (tan i ₁ + tan θ/2) It is known that the trajectory is generally a quadratic curve.

Similarly, the locus of the intersection point (X ₂ , y ₂ ) between mirror M ₂ and the chief ray generally becomes a quadratic curve. Then the second
As shown in the figure, consider small mirrors N ₁ and N ₂ consisting of partial areas of mirrors M ₁ and M ₂ , and mirrors M ₁ and M ₂
Instead of moving the support body of small mirror N ₁ in the straight line a 1 direction, and the support body of small mirror N ₂ in the straight line a ₁ direction, instead of moving it in the 0 _A 0 _B 0 _C direction,
a Move in _two directions, and the small mirrors N ₁ and N ₂
Let us consider a system in which b ₁ and b 2 move on predetermined quadratic curves b 1 and b ₂ , respectively.

Here, the moving speed of the supports of the small mirrors N ₁ and N ₂ is calculated.

When the angle between the straight line a ₁ and the y-axis is β ₁ , the angle between the straight line a ₂ and the y-axis is β ₂ , and the circumferential speed of the photoreceptor is υ ₀ , the moving speed of the small mirror N ₁ in the β ₁ direction is υ ₁ is =・sin(i ₁ −θ/2)/sin(90°+i ₁ −β
₁ ), = 0 _A 0 _B , υ ₁ = υ ₀ sin(i ₁ −θ/2)/2cosθ/2・cos(i ₁ −β
₁ ), and the moving speed υ ₂ of the small mirror N ₂ in the β ₂ direction is equal to =・ in Fig. 1.
sin(90゜−.i ₁ )/sin(β ₂ −θ/2−i ₁ ), = 0
From _A 0 _B , the speed is constant, υ ₂ = υ ₀ cosi ₁ /2cosθ/2・sin (β ₂ −θ/2−i ₁ ).

small mirrors N ₁ and N ₂ at their reflection points, namely A ₁ , B ₁ , C ₁
Furthermore, moving along predetermined quadratic curves along A ₂ , B ₂ , and C ₂ results in non-uniform movement, but this is because the support of the small mirror N ₁ is moved at a constant speed in the straight line a ₁ direction as described above. υ ₁
The support body of the small mirror N ₂ may be moved in the direction of the straight line a ₂ at a constant speed υ ₂ , and the small mirrors N ₁ and N ₂ may each follow on a predetermined quadratic curve. As a result, the effective dimensions of mirrors N ₁ and N ₂ can be reduced to the minimum required dimensions. Ideally, it is desirable for the scanning mirror to move on the quadratic curve of the above-mentioned equation, but in view of the gist of the present invention, as long as the purpose of the present invention can be achieved, the above-mentioned equation 2 Of course, even curves that deviate somewhat from the following curves fall within the scope of the present invention. Furthermore, when the copy magnification changes, the quadratic curves b ₁ and b ₂ generally change, but the difference before and after the copy magnification change can be kept small by arranging lenses and small mirrors.

Further, although the reflection point of the mirror changes depending on the copying magnification, the effective portion only needs to be made larger by that amount, and even if this is taken into account, the size of the mirror can be made smaller than before.

Next, the mechanism according to the present invention is shown in FIGS. 3 and 4.

In Fig. 3, 1 is the original to be copied, 2 is a document table made of a transparent material, 3 is a projection lens, 4 is a movable first small mirror, and 5 is a movable first small mirror 4. a cam plate for regulating the movement trajectory, 6
is a movable second small mirror, 7 is a second small mirror 6
8, a belt for moving the first small mirror 4; 9, a belt for moving the second small mirror 6; 10, a belt; 8, 9; 13a, 13b, 13c, 13d, 13e are guide rollers, 15 is a charging corona, 16 is a developing device, 17 is a transfer corona, and 18 is a separation motor. Laura, 19
is a paper feed cassette, 20 is a paper feed roller, 21a,
21b is a fixing roller, 22a, 22b, 22c,
22d is a paper feed roller, 23 is a paper ejection tray, 2
4 is a main body of the copying machine, 25a and 25b are illumination lamps that illuminate the entire surface of the original 1, and 26 is a cleaning blade. When the motor 10 rotates in the _A1 direction, the photoreceptor 14 rotates in the _A2 direction, causing the small mirrors 4,
6 moves in the A ₃ and A ₄ directions, respectively, and the scanning on the document surface is performed.
A It is carried out in ₅ directions. FIG. 4 shows a quadratic curve movement mechanism for the small mirror. 27 is a first small mirror support block fixed to the belt 8; 28, 29;
34 is a guide rod for moving the first small mirror support block 27 to a predetermined position by following the linear groove 32 of the cam plate 5 when the belt 8 moves; The shaft is fixed to the small mirror support block 27 at an angle α, and the shaft 34 is fixed to the first small mirror 4 by a bearing 30.
In contrast, the first small mirror 4 is slidable. Further, the shaft 31 fixed to the bearing 30 is fitted into a groove 33 of the cam plate 5 carved to form a predetermined quadratic curve, and as the first small mirror support block 27 moves linearly, the first small mirror supports the first small mirror. The mirror 4 will move on a predetermined quadratic curve. The second small mirror also has the same structure as the first small mirror.

To explain the overall process, a document 1 is placed on a document table 2 and a copy button (not shown) is pressed. Then, the motor 10 rotates in the _A1 direction, the photoreceptor 14 starts rotating in _{the A2} direction, the first small mirror 4 starts moving in the _A3 direction, and the second small mirror 6 starts moving in the _A4 direction. At this time, the angles of the first small mirror 4 and the second small mirror 6 are in a positional relationship that satisfies the optical path described above, and the speed υ ₁ of the first small mirror 4 and the speed υ ₂ of the second small mirror 6 are respectively This can be achieved by selecting appropriate diameters of the pulleys 11 and 12. Images scanned by the first small mirror 4 and the second small mirror 6 are sequentially exposed onto the rotating photoreceptor 14. During this time, a charging corona 15, a developing device 16, and a transfer corona 1 are placed around the photoreceptor.
7. The cleaning blade 26 may operate in a normal copying process. Further, at a predetermined time, the paper is fed from the cassette 19 by the paper feed roller 20 in synchronization with the rotation of the photoreceptor 14, and after transfer, the paper is transferred to the separation roller 1.
8, fixing rollers 21a and 21b, and is discharged to a paper discharge tray 23.

As described above, according to the present invention, a compact optical scanning device can be realized by moving the support of the small mirror at a constant speed in a predetermined linear direction and moving the small mirror at a non-uniform speed on a predetermined quadratic curve. Can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a conventional optical device, FIG. 2 is an explanatory diagram of an embodiment of the present invention, and FIGS. 3 and 4 are explanatory diagrams of a mechanism according to the present invention. In the figure, 1 is a document, 3 is a projection lens, 4 is a first small mirror, 6 is a second small mirror, and 14 is a photoreceptor.

Claims (1)

[Claims] 1. In a slit exposure type copying machine, etc., the scanning system disposed between the lens and the photoreceptor is a small mirror.
Consisting of M ₁ , M ₂ and supports K ₁ and K ₂ for the small mirrors, the mirror supports move linearly in a predetermined direction at constant speeds V ₁ and V ₂ , and each small mirror moves at a constant angle with respect to the document surface. A predetermined quadratic curve according to the following formula: y ² - (L + l + xtani ₁ ) y + L {1/2 [tani ₁ + tanθ/2] x + l} = O However, the y-axis is the optical axis of the lens, and the x-axis is when there is no mirror. , i ₁ is the angle of incidence of the incident optical axis on one mirror, θ is the angle between the incident optical axis of one mirror and the exit optical axis of the other mirror, and L is the pupil on the photoreceptor side of the lens and the image plane. l is the length of the optical axis of the lens between the reflection point of one mirror and the image plane when the principal ray coincides with the optical axis of the lens. An optical scanning device characterized in that the optical scanning device moves along the