JPS6014333B2 - Copier optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical device for a copying machine that supports a document to be copied on a fixed flat document table and performs slit scanning and illumination scanning of the document.

The projection lens is moved back and forth a short distance in a direction perpendicular to its optical axis,
Alternatively, there are two types of optical illumination for originals in copying machines that scan the original by slit scanning by rotating a scanning mirror. In connection with the mechanism of
There is an illumination scanning method in which illumination light is moved over the document.

The former illuminates the entire surface, so the power consumption of the light source is large.
The drawback is that it generates a large amount of heat, which changes the sensitivity of the photoreceptor and the discharge power of the charger, resulting in image deterioration.

The latter is: ■ A light source movement method that moves the illumination light source in parallel with the slit scanning, ■ A mirror translation method that moves the light from the illumination light source in parallel with the slit scanning, and ■ A synchronous movement method that moves the illumination light source in parallel with the slit scanning. There is a reflector rotation method in which a reflector is rotated to reflect light from a fixed illumination light source.

Both (1) and (2) must have a reciprocating parallel movement mechanism. It goes without saying that the reciprocating speed needs to match the copying speed, but it is also necessary to make the reciprocating speed as fast as possible and shorten the time required per cycle of image processing. However, in reality, the backward movement speed will be about 2 to 3 times the forward movement speed. ■
In this case, rotating the reflector near a fixed illumination light source may cause electrical shock, electrical leakage, and other risks unless the contacts of the illumination light source are adequately protected.

Another drawback is that the intensity of illumination varies depending on the irradiation distance between the fixed illumination light source and the fixed document. The present invention eliminates these drawbacks and provides a fast and efficient illumination device with a simple mechanism. That is, the present invention includes a first and a second light source, and each of them is spread around a fulcrum distant from the light source to illuminate and scan the surface of a document held in a flat Z position. The second light source mainly contributes to document illumination in the first half of the slit scanning range, and the second light source mainly contributes to document illumination in the second half of the slit scanning range.

The first light source is arranged so that the distance between the optical scanning slit on the document and the first light source is kept almost constant in the front Z half of the slit scanning range, and the second light source is arranged in the rear half of the slit scanning range. The second light source is rotated in such a way that the distance between the optical scanning slit on the document and the second light source is kept substantially constant. By doing so, it is possible to speed up the illumination scanning of the original, and thus to speed up the slit scanning, and at the same time, it is possible to sufficiently reduce the variation in illuminance on the original in the illumination scanning direction. It becomes possible.
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of an embodiment of the present invention. P in the figure is a transparent flat plate serving as a document table, and the upper surface thereof is used as a document supporting surface. The document table P is a fixed document table. D has an electrophotographic photoreceptor on the peripheral surface 3
The drum rotates at a constant speed in the direction of the arrow. As the drum D rotates, the photoreceptor is first charged to a predetermined polarity, then subjected to slit exposure of the original image by the optical system described above,
As a result, a static exposure latent image of the original is formed, this latent image is then developed to form a toner image 3, this toner image is then transferred to a predetermined transfer material, and the transferred toner image is transferred While the image is fixed on the material, the photoreceptor is cleaned after the transfer is completed and the above cycle is repeated again. M,,1,
M2 and S are optical systems for exposing the original image to the photoreceptor through 4 slits, M is a scanning mirror, 1 is a projection lens, and M2 is
is a fixed mirror, and S is a closed slit.

The scanning mirror M, rotates back and forth between the solid line position and the broken line position around the axis M^, and moves the document support surface from the PL position to the PR position during the previous loading.
Scan the slit at a constant speed to the desired position. Mirror M after scanning
, rotates and returns to the starting position. Lens 1 is mirror M,
The light reflected from the original is converted into imaging light to form an image of the original on the photoreceptor. M2 is a fixed mirror that bends the optical path, and deflects the light from the lens 1 to direct it toward the photoreceptor. The slit opening OS is for restricting the imaging light from the mirror ground and exposing the original image to the photoreceptor through the slit. In other words, the image of the document area included in the image S' of the slit opening S projected onto the document support surface through the lens 1 is formed on the photoreceptor. Note that the slit Sekiguchi S is not placed in close contact with the photoreceptor, but is placed near it, so the lens 1, which is placed so that the document support surface and the photoreceptor are in a conjugate positional relationship, In this case, the perfectly focused image of the slit opening □S is focused above the document support surface.However, the image formation position is near the document support surface, and therefore the slit focus on the document support surface is The amount of blur in the mouth image S' is also small and can be ignored in terms of copy image formation.In this specification, the image S' of the slit Sekiguchi on the document support surface is
is called the slit Sekiguchi image or optical scanning slit.
Scanning the document by moving the slit closed image on the document support surface in this manner is called slit scanning, and the range from the start position to the end position of scanning the document by the slit open image is called the slit scanning range. . In Fig. 1, the slit scanning range is between PL and PR, and the slit closing image S' moves at a constant speed from PL to PR direction with the forward rotation of mirror M, but the moving speed is limited to the circumference of the photoreceptor. This speed is based on the reciprocal of the imaging magnification by the lens 1. Of course, the image S' moves back from the PR direction to the PL direction by the backward rotation of the mirror M. Note that the rotation axis M^ of the mirror M is arranged on a line perpendicular to the document support surface at the center of the slit scanning range. Even if it is not geometrically on this perpendicular line, by placing a fixed mirror between the original and the mirror M, and placing the mackerel M^ on the reflection line of this perpendicular line by the same fixed mirror, optically It may also be placed on a line equivalent to . Needless to say, the axis M^ is parallel to the document support surface and perpendicular to the slit scanning direction. In synchronization with the above document slit scanning, the document is illuminated and scanned by the following mechanism.

For the first half of the slit scanning range, that is, from the scanning start position of the unwanted document to the center of the slit scanning range (between PL and Pc in the figure), the first illumination scanning means mainly illuminates and scans the document. The second half of the slit scanning range, that is, the range from the center of the slit scanning range to the scanning end position of the original (P in the figure)
c, PR), the second illumination scanning means plays a central role in illuminating and scanning the document. Hereinafter, the first illumination scanning means, the second
The codes of Fumura et al. regarding the illumination scanning means of the L. R
Attach the suffix. Now, the first and second illumination scanning means are respectively tube Z-shaped lamps LL and LR and a reflector shade RL.
, RR, and the lamp and reflector are integrally fixed to each other and supported by arms SL and SR, respectively.

The arms SL and SR are provided so as to be able to move back and forth around the wheels OL and OR, respectively, which are provided in the positioning almanac away from the lamp and the reflector. Therefore, lamps LL,L
R, reflective shade RL, RR are integrated with arms SL, SR,
Mirror M between positions AL, AR darkness, counterfeit BL and BR, respectively.
It rotates back and forth in synchronization with the reciprocating rotation of. The reflective shade RL,
Each of the RRs has a reflecting surface that forms a quadratic curve on a cross section perpendicular to the generatrix, and reflects the light from the lamps LL and LR, respectively, to form a reflected light beam having convergence within the cross section. And the reflection shade RL, RR is such that the above reflection light east is
The arrangement is such that wherever the light is incident on the document support surface within the cut scanning range, it has a convergence property within the above-mentioned cross section. The plane that includes the convergence point of Koto and the central axis of the lamp in the above cross section is tentatively named the principal light plane. Usually, an elliptical cylindrical mirror in which the quadratic curve of the above reflecting shade is a part of an ellipse is useful, and when elliptical cylindrical mirrors are used as the reflecting shade RL and RR, the lamp L is directed to the first focal line of each, and the LR is the respective second focal lines are located on the opposite side of the document support surface from the first focal lines. In this case, the principal light plane is a plane connecting the first focal line and the second focal line of each of the elliptical cylinder mirrors RL and RR. In any case, reflective hat RL
, RR forms a slit-like document illumination area that is elongated in the direction perpendicular to the slit scanning direction on the document support surface (lamps LL, LR,
The caps RL and RR have a length equal to or longer than the width of the document support surface in the direction perpendicular to the scanning direction, and each longitudinal direction is parallel to the document support surface and perpendicular to the slit scanning direction. Needless to say).

The first illumination scanning means and the second illumination scanning means cause the respective slit-like illumination regions to overlap at least partially on the document support surface, and on the same surface, the slit aperture image S' in the slit scanning direction. can be moved at the same speed. As a result, the slit closed image S' always remains within both illumination areas, at least during movement. More specifically, the first illumination scanning means and the second illumination scanning means move the respective lines of intersection of the principal light plane and the document support surface in the same direction and at the same speed as the slit scanning, and both of the lines of intersection move The arms SL and SR are moved forward and backward so that they always exist within the slit Sekiguchi image S' at least throughout the forward slit scanning period. It is desirable that both of them match). To explain further with reference to the figure, when the mirror M is at the solid line position in Figure 1 (when the slit Sekiguchi image S' is at PL), the lamp L
L, LR, and reflective shades RL and RR are located at the AL and BL positions, respectively, and form the slit-like illumination area at the PL position of the document support surface (the two principal light planes intersect at PL). Next, when the mirror M rotates to the intermediate position between the solid line and the broken line (the slit aperture image S' reaches the position Pc), the lamps LL, LR,
The reflective shades RL and RR are rotated to the Ac and Ac positions, respectively, to form the slit-like illumination area at the Pc position on the document support surface,
The two principal light planes intersect at Pc. Furthermore, Miller M. moves to the broken line position and the slit Sekiguchi image S' moves to the PR position, the lamps LL, LR and the reflectors RL, RR become AR, respectively.
The slit-like illumination area is formed at the PR position of the document support surface by rotating to the BR position, and the two main planes intersect at the PR position. This completes the forward scanning of the document slit and illumination. When this scanning is completed, the mirror M returns from the broken line position to the solid line position, and in synchronization with this, the lamp LL
, LR, and the reflectors RL and RR are reinstalled from the AR and BR positions to the AL and BL positions, respectively. It is desirable that this return lamp be turned off. Next, the positions of the koji OL and OR will be explained.

Regarding linear light sources, which are often used as illumination light sources not only for the apparatus shown in this embodiment but also for copying apparatuses currently on the market, it is necessary to eliminate unevenness in the amount of light in the linear direction or to improve the characteristics of the optical projection system. In order to adapt, various ideas have been made to change the light quantity distribution in the linear direction so that it increases on the end side. One of them is a multi-spot halogen lamp. As is well known, this direction is perpendicular to the optical scanning direction (
Five to seven light emitting parts are distributed in the linear direction of the lamp), so that the amount of light from each light emitting part is smoothly superimposed and is compatible with the characteristics of the optical system as described above (Fig. 3A). (Reference: E is a light emitting unit, 1 is a light amount distribution by each light emitting unit E at a predetermined distance from the lamp, and 12 is a light distribution that is the sum of 1). However, if the distance between the lamp and the illuminated part of the document surface (the slit open image part) changes from the predetermined distance above, the degree of superimposition of the light amount by each light emitting part will change, and the light amount distribution in the longitudinal direction of the lamp will deviate from the predetermined design value. There are drawbacks to doing so.

Furthermore, when only a lamp is placed, the amount of illumination light decreases in inverse proportion to the square of the distance from the lamp, and even if the degree of illumination can be improved somewhat by correcting it with a reflector or other means, it will still decrease as the distance changes. The inconvenience that the amount of light changes remains. Therefore, it is desirable to minimize variations in the distance between the lamp and the irradiated portion of the document surface even in a rotating scanning illumination system (see Figure 3B. The numbers are the same as in Figure 3A, but In the case shown, the distance between the lamp and the illuminated portion of the document surface is larger than in the case shown in FIG. 3A). For the above reasons, the rotation center axis OL of the first illumination scanning means is PL. At the midpoint Pc between Pc, the rotational center axis OR of the second illumination scanning means is on the perpendicular to the document support surface at the midpoint Pc2 between Pc and PR. Position each on the perpendicular line.

In other words, the Fuji OL is on a perpendicular line set on the document support surface at a distance of 1/4 of the slit scanning range in the slit scanning direction from the document scanning start position, and the axis 〇R is on the slit from the document scanning start position. They are each positioned on a perpendicular line to the document support surface at a distance of 3'4 from the slit scanning range in the scanning direction. Therefore, the axis OL is equidistant from PL and Pc, and the axis ○R is equidistant from Pc and PR. Then, the lengths of arms SL and SR (therefore, O
In this embodiment, the distance between L and RL and the distance between OR and RR are the same, the light emission distribution and light emission amount of the lamps LL and LR are the same, and the shapes and dimensions of the reflectors RL and RR are the same. The respective distances (OLPc, ORPc2) between Fuji OL, OR and the document support surface on each of the perpendicular lines are equal. (Needless to say, the axes ○L and OR are located below the document support surface as shown in the figure, and are oriented parallel to the document support surface and perpendicular to the slit scanning direction. In the case where a fixed mirror is arranged between the system consisting of LL, LR and the reflector RL, RR and the document support surface to make the east optical path of the illumination light coincident with each other, the axes ○L and OR are not on the perpendicular line. , on the line of reflection of the perpendicular by the fixed mirror, that is, on a line optically equivalent to the perpendicular). , ALPL=Ac
Pc'OBcPc BRPR, and then AL
It becomes clear that PL=BRPR, AcPc=BcPc.

On the other hand, ALP is performed from lamp LL on the main light plane (=AcPc
) is the center of the OL in the first half of the scan, PL.
, Pc on the circular arc (PLPc), and also on the main surface from the lamp LR to BcPc (=BRPR=Ac
It is also clear that a point at a distance of PL) moves on an arc (PcPR) centering on OR and passing through Pc and PR in the second half of the scan (2). Therefore, OLPc, (=ORPc2)
be more than twice PLPc (=PcPR)0, and AL
If PL (=BRPR) is made more than 1 times PLPc (=PcPR), the arc PLPc and the chord P on the principal light plane
LPc and the ratio of the distance between the arc PcPR and the chord PcPR to ALPL and BRPR, respectively.
The occurrence of undesirable light intensity unevenness in the longitudinal direction of the rattan shown in FIG. B is generally so small that it can be ignored. In any case, by providing OL and OR on the perpendicular line to the document support surface in Pc and Pc2, the distance between the lamp LL and the slit aperture image OS' can be reduced in the first half of the scan (3). "And in the second half of the scan, it became possible to scan the original with the slit and illumination while keeping the distance between the lamp LR and the slit Sekiguchi image S' almost constant.And in the first half of the scan, In the latter half of scanning, the light intensity of the second illumination and scanning means is mainly utilized, respectively. The illuminance of the illumination light will be explained below.

The same can be said symmetrically about the second illumination scanning means, so unless necessary, the first illumination scanning means will be described below. The illumination light illuminance at the slit Sekiguchi image S' on the document support surface is proportional to the value obtained by multiplying the amount of illumination light incident on the aperture image S' by cos^.

Therefore, the amount of illumination light incident on the slit open image S' is PL
Assuming that it is the same everywhere from position Pc to position Pc, the illuminance changes as shown in FIG. Note that the above ^ is the angle of incidence of the main light plane on the document table, or in other words, the angle of incidence of the illumination light east on it, and in the embodiment shown in FIG. The value gradually increases. Here, it is desirable that the input at the Pc position is at most about 6 degrees. This is because when the angle of incidence exceeds 60 degrees, the reflectance on the surface of the document table glass Z rapidly increases, and the amount of light reaching the document rapidly decreases. FIG. 3D shows the relationship between the change in input (therefore, the change in scanning position) and the efficiency of light incident on the document support surface. In addition, the minimum value of ^ (the incident Z of the illumination light east at the PL position
The angle) is preferably about 25o.

This is done so that the image of the lamp LL is not reflected on the lower surface of the document table and formed on the photoreceptor via the lens 1, so that the mirror M,
This is because the rotation angle 2 needs to be larger than the maximum rotation angle of the optical koji of the lens 1 in the first half of scanning (<PLM^Pc in FIG. 1). The above <PLM^Pc is generally set to a maximum of 2y in this type of copying machine. Next, if we show the change in the amount of illumination light on the document support surface due to the change in distance from the lamp, assuming that there is no partially reflective surface such as a glass surface up to the document surface, as shown in Figure 3E, Become.

As can be easily understood from the explanation of Figure 1,
In the range of 250 to 60o, that is, at the positions of PL and Pc, the curve is approximately parallel to the vertical axis and hardly changes. As a total of the effects described above with reference to FIGS. 3C, D, and E, the illuminance within the slit aperture image S' on the document supporting surface is as shown in FIG. 3F.

In this figure, the curve ■ shows the relationship between the illuminance and the position (scanning position) of the slit closed image S' by the first illumination scanning means, the curve ■ shows the relationship between the illuminance by the second illumination scanning means, and the curve ■ It is shown by scanning means. As can be seen from this figure, from the document scanning start edge (PL) to the center of the scanning range (Pc), that is, in the first half of scanning, the first illumination scanning means mainly contributes to document illumination, and from the center of the scanning range (Pc) From the beginning to the end of document scanning (PR), that is, in the latter half of scanning, the second illumination scanning means mainly contributes to document illumination. Therefore, as is clear from FIG. 3F, the illuminance is substantially uniform in the document scanning direction. Also, in the first half of the scan, the distance between the lamp LL and the slit Sekiguchi image S', and in the second half of the scan, the distance between the lamp LR and the slit Sekiguchi image S',
Since the illuminance distribution is kept almost constant, the illuminance distribution on the document support surface is the same as that of the third one throughout the scanning range, even in the direction perpendicular to the scanning direction.
The state shown in Figure A will be maintained.

An example of a lamp rotation drive mechanism will be explained with reference to FIG.

A reflective shade RL (RR) is fixed to the side plate 1. A lamp holder 2 is also fixed to the side plate 1, and a halogen lamp LL (LR) is fixedly supported on the lamp holder 2. Further, an arm SL (SR) is also fixed to the side plate 1. This arm SL (SR) is L-shaped, and a fulcrum shaft (OR) is fixed to the bent portion. Fulcrum shaft OL
(OR) is rotatably supported by a bearing of a stationary member on the copying machine main body side (not shown). A cam follower 3 is provided on the side opposite to the side plate 1 with respect to the fulcrum OL (OR) of the L-shaped arm SL (SR), but this follower 3 is always attached to the cam surface of the cam 4 by a spring, etc. It is urged to press elastically.

On the other hand, the cam 4 is fixed to a shaft 5, and this shaft is rotatably supported by a bearing of a stationary member on the copying machine main body side (not shown). Further, a gear 6 is fixed to the shaft 5, and this gear 6 is a gear 8 fixed to a rotating shaft of a motor 7 fixed to a stationary member on the copying machine main body side (not shown).
It meshes with the The motor 7 rotates at a constant speed in synchronization with the rotation of the mirror M. This causes the cam 5 to displace the follower 3, so that the lamp LL (LR) and the reflector RL (RR
) rotates back and forth around the axis (OR) as described above. As is clear from the detailed description above, according to the present invention, a flat document surface can be scanned with illumination at high speed while minimizing changes in illuminance, and the configuration is simple. Therefore, it is possible to obtain high-quality copied images at high speed, which is a great contribution to this industrial field.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of one embodiment of the present invention, Fig. 2 is an explanatory diagram of an example of the drive mechanism of the same embodiment, and Figs. 3 A, B, C, D, E, F.
1 is a diagram for explaining the effect of the embodiment of FIG. 1. FIG. In the figure, P is a flat document table, 1 is a lens, M is a rotating mirror, S is a slit Sekiguchi, D is a photosensitive drum, LL and LR are lamps, RL and RR are reflective shades, SL and SR are arms, O
L and OR are pivot points. Crocodile illustration. Younger brother

Claims (1)

[Scope of Claims] 1. A flat document table on which a document to be copied is placed, a slit scanning means for scanning the document through a slit and projecting the image onto a photoreceptor, and illuminating and scanning the document in synchronization with the slit scanning. In the optical device of a copying machine, the illumination scanning means includes a first light source, a second light source, and an optical device on the original document. The first supporting means rotatably supported around the first fulcrum and the second light source are connected to the second light source so that the distance between the target scanning slit and the second light source can be maintained substantially constant in the first half of the slit scanning range. a second support means rotatably supported around a second fulcrum so that the distance between the light source and the optical scanning slit on the document can be maintained substantially constant in the latter half of the slit scanning range; The first and second light sources are rotated in synchronization with the slit scanning, and the first light source is used mainly for the first half of the slit scanning range, and the second light source is used for the second half of the slit scanning range. An optical device for a copying machine, characterized in that it illuminates and scans a document. 2 The first fulcrum is located at 1/4 of the slit scanning range in the slit scanning direction from the slit scanning start position of the document.
The second fulcrum is located on a vertical line erected on the document table, or on a line optically equivalent thereto, and the second fulcrum is located within 3/3 of the slit scanning range in the slit scanning direction from the slit scanning start position of the document. 4. The optical device of a copying machine according to claim 1, wherein the optical device is located on a vertical line erected on the document table at point 4, or on a line optically equivalent thereto.