JPS5937536A - Optical image formation system - Google Patents

Abstract

PURPOSE:To uniform the lengthwise reference illuminance distribution of the photodetection part of an image receiving member, by using an illuminance distribution compensating member formed by stacking two plates, i.e. the 1st correcting plate whose adjacent aperture intervals at the center part are different from those at the left and right end sides, and the 2nd compensating plate which shields some of apertures. CONSTITUTION:Two illuminance compensating members 8a and 8b which have plural longitudinal slit holes 91 of the same area along the lengthwise direction of breadth wide plate surfaces in which holes intervals are made wide in the center and increased to the left and right ends gradually are used while stacked one over another; and they are arranged in the optical path from a light source 3 to the image receiving member 7 so that the array direction coincides with a main scanning direction. Then when the slit plates 8a and 8b are adjusted relatively by upper and lower position movement, individual composite slit holes formed along the lengthwise direction formed by the overlap of both plates vary in aperture hole area, so the transmitted light distribution characteristics of the illuminance distribution compensating member are varied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging optical system in, for example, a facsimile transmitter, various image readers, electrophotographic copying machines, etc., and relates to the if4 COS fourth power law characteristic of an imaging lens.

An adjustment that compensates for the light emission distribution characteristics along the long plane of the light source for illuminating the object and equalizes the reference illuminance distribution along the length of the light-receiving length of the image-receiving member? The purpose is to make it possible to perform tasks accurately, easily, and quickly.

For convenience of explanation, FIG. 1 shows a very schematic configuration of an example of a facsimile transmitter. That is, 1 is the original (subject) to be transmitted, which is set on the original placing table 21 with the image surface facing downward.
The conveyance roller 2 performs step conveyance (sub-scanning conveyance) in the direction of arrow A with a fine pitch corresponding to a predetermined sub-scanning density. 1ili transported in this step
7. When the original with the image plane facing downward passes through the illumination unit 4, it is illuminated by the illumination light source 3Vc in the main scanning direction substantially perpendicular to the transport direction A.
IJ! The illumination light reflected from the document surface passes through the fixed reflection mirror 5 and the imaging lens 6 and collects CO2.
An image is formed on a light receiving portion of a one-dimensional solid-state image sensor (image receiving member) 7 such as D and the like. 8ij An illuminance distribution correction member along the light-receiving length of the element 7, which is an image-receiving member, interposed in the optical path between the light source 3 and the original 1 or between the original 1 and the imaging lens 6,
This will be discussed later.

Then, the imaging light for the element 7vc is read by the light 11 as a time-series electrical digital pixel signal by the self-main scanning function of the element, and is transmitted to a receiving and polarizing section (not shown). In this way, each main scanning line L of the original image surface is read sequentially for each step of transport of the original, and image information of the entire original is finally transmitted, and the image is reproduced (copied and display) or memorization.

In this example, a straight tube fluorescent lamp is used as the light source 6 for illuminating the document. The luminous intensity distribution along the length of the fluorescent lamp, excluding both end portions, is a relatively uniform luminous intensity distribution at each portion, but at both end portions, the luminous amount is lower than the middle portion as described in 1. So, fluorescent lights 3 and 1. For this purpose, use a device that is longer than the maximum document width (dimension in the main scanning direction) that can be processed for transmission, and arrange the fluorescent lamp part in between (excluding both ends) so that it corresponds to the document illumination section. M is arranged so that the entire surface is illuminated as uniformly as possible in the main scanning direction.

The illuminance distribution correction member 8 compensates for the C084 power law characteristic of the imaging lens 6 and the light emission 1 distribution characteristic along the length of the original illumination light source 3, and adjusts the light receiving length (longitudinal direction (c) main scanning direction) of the element 7, which is an image receiving member.
A member for uniformizing the reference illuminance distribution along the light receiving length of the image receiving member (when a blank original or a white reflective plate is placed in the original illumination unit 4 and the image receiving member 7 is imaged and exposed).

Concrete K [As shown in the second figure, it is a slit plate in which a horizontally long slit hole 9 is formed with a width in the central part and the width gradually increases toward the left and right ends.

Suppose that the illuminance distribution correcting member 8 is interposed in the above-mentioned imaging optical system and the reference illuminance distribution along the length of the element 7, which is the image receiving member, is changed to a result like break #c in Fig. 6. Influence of the cosine fourth law characteristic of the image lens 6 f Distribution is sharp. Further, if the light source 3 also has non-uniformity in the light emission distribution along its length, the non-uniformity is further superimposed on the non-uniformity a of the reference illuminance distribution.

If the reference illuminance distribution is non-uniform, density unevenness will occur in the reproduced image corresponding to the non-uniformity.

On the other hand, in advance, the cos fourth law characteristic C of the used imaging lens is
A slit plate in which the shape of the slit hole 9 is designed and set so that the transmitted light distribution characteristic along the longitudinal direction is more like that shown in FIG. 8 in the optical system.

The above C084 power law characteristic C and the non-uniformity a of the reference illuminance distribution due to the light emission distribution characteristic of the light source 3 are compensated and corrected to make the illuminance distribution uniform along the length as shown in #d in the figure. .

However, the slit plate 8, which is the above illuminance distribution correction member, must be placed at a predetermined position in the imaging optical system and in a predetermined posture so that a linear reference illuminance distribution as shown by the solid line d in FIG. 3 is finally obtained. This involves the work of fine adjustment L-& and arranging it with physical fixing members, and it is difficult to injure it to arrange it correctly, and it lacks the ease and speed of the work. Furthermore, the light emission characteristics of light source 3 are not uniform individually, but vary during the winter.
1) Since it is E, there is actually a difference of Kg4 between the slit plate 8 with the slit hole shape designed and set in advance, and this point is also one of the reasons for making the initial adjustment work difficult (2).

Also, the initial adjustment work was done well.

Since the light source 3 deteriorates over time and its light emission level and light emission distribution characteristics change, as the light source deteriorates, the reference illuminance distribution d at the time of initial adjustment becomes non-uniform over time.

If the reference illuminance distribution d becomes non-uniform and falls outside the allowable range, it is necessary to carry out the time-consuming work of readjusting the arrangement position and posture of the slit plate 8.

In the facsimile transmitter of the improved example, which reads image information all photoelectrically, the non-uniformity of the reference reference portion d is electrically detected, and based on the detected data pr,
Some devices are designed to fully automatically correct the time-series electric digital pixel signals output from the element array 7, but this requires a complicated circuit and inevitably increases the size and cost of the device.

Problems like the above can be solved by facsimile transmission (g
Not only machines, but also various other image readers.

This is also common in various image forming apparatuses VC, such as electrophotographic copying machines, which write the entire copy by exposing the surface of a photoreceptor (image receiving member) to a slit image using a t-system that forms an original image.

Similarly to the present invention, an illuminance distribution correction member is interposed in the optical system to compensate for the C084 power law characteristic of the imaging lens and the luminous intensity distribution characteristic of the object illumination light source. Although the aim is to achieve uniformity, it is devised so that initial adjustment and re-adjustment due to VC such as deterioration of the light source over time can be performed accurately, easily and quickly.

That is, one aspect of the present invention is to improve the illumination distribution in an imaging optical system including at least an illuminance distribution correction member that compensates for the C084 power law characteristic of the imaging lens and makes the reference illuminance distribution uniform along the light-receiving length of the image-receiving member. As a correction member.

A first correction plate having a plurality of openings formed along the length of a horizontally long plate surface with the distance between adjacent openings at the center of the plate surface and the distance between adjacent openings at the left and right ends of the plate; 1-9 Use a two-layered correction plate that can shield a portion of each aperture of the second correction plate.1-9 Place the two-layered correction plate in the optical path of the imaging optical system. The relative position movement can be freely adjusted along the board surface.

This is the entire summary of the imaging optical system that is characterized by the following.

FIG. 4 and subsequent figures show one embodiment. As shown in FIG. 4, a plurality of vertically long slit holes 91 having the same area are formed along the length of a horizontally long board surface in the center of the board surface as an illuminance distribution correction member. The distance between adjacent slit holes is wide.

Twelve pieces 8a and 8 of a tortoise-shaped slit hole arrangement in which the distance between adjacent slit holes is gradually narrowed toward the left and right ends of the plate.
1 in the optical path from the light source 6 to the image receiving member 7, as shown in Figure 5. For example, in the optical path from the light source 3 to the first surface of the document, which is the subject, as shown in Figure 7 (it is better to place it closer to the light source 3). , preferably near the U mirror 5 and the imaging lens 6), or in the optical path between the imaging lens 6 and the image receiving member 7 (
The arrangement direction of the slit holes of the same 1 KM number is arranged so that the main scanning direction coincides with that of the slit holes. In this case, the above two slit plates 8
A, sbh, one or both of the slit plates with I/r are arranged so as to be freely adjustable in position relative to each other in the width direction B (FIG. 5, hereinafter referred to as the vertical direction) K. A mechanical mechanism for adjusting the relative position of the slit plate can be easily constructed using HIJ sink screws, levers, etc. In this case, it is preferable that the movement adjustment knobs and levers be exposed outside the exterior of the device so that the positions of the slit plates 8a and 8b can be adjusted outside the device.

In the example shown in FIG. 5, one slit plate 8aij is fixed and held on the chassis of the device, and the other slit plate 8bH is connected and supported as a movable plate to the fixed slit plate 8aK via a vertical screw 81. It is something that was put on display. 82
86 is a fixed nut on the movable slit plate 8b side, 84.84\1 is a vertical long hole formed on the left and right end surfaces of the movable slit plate 8b,
85 and 85 are screw holes formed on the left and right end surfaces of the fixed slit plate 8a, and 86 and 86#- are screw holes formed in the long hole 84.
・This is a screw that is screwed through 84 into holes 85 and 85.

Loosen the screws 86 and turn the vertical screw 81 to the left or right to change the movable slit plate 8b to the fixed slit plate 8a.
It moves up and down and changes its position. Pinu 86 after position adjustment
- Tighten 86 pieces to firmly fix it to the movable slit plate 8b' (r) to the fixed slit plate 8a.

When the above-mentioned slit plates 8a and 8b''f are adjusted by moving up and down as appropriate, the opening area of each composite slit hole 92 along the length of the plate formed by the overlapping of the nine plates 8a and 8b changes in size. That is, two slit plates 8a and 8
The transmitted light distribution characteristic b (Fig. 6) along the length of the illuminance distribution correction member consisting of b is changed as shown by Mb' or b'' in Fig. 6 in response to the adjustment of the vertical position movement of the slit plate. In other words, when the solid line b'l in FIG. The distribution characteristic changes in the direction of b′,
On the contrary, synthetic slit hole 92. When the aperture area is adjusted in the smaller direction, it changes in the b'' direction.

As described above, in the present invention, it is possible to change the transmitted light distribution characteristics of the illuminance distribution correction member by adjusting the relative position movement of the slit plates 8a and 8b.

(1) In the initial adjustment of the reference illuminance distribution for the image receiving member 7, even if the positions and postures of the illuminance distribution correction members 8a and 8b in the optical path are slightly out of alignment, the luminous intensity distribution of the light source 6 Even if the characteristics are slightly different from the expected characteristics due to manufacturing variations, the transmitted light distribution characteristics of the illuminance distribution correction members 8a and 8b can be appropriately changed in the -b' direction or the Fib' direction to compensate for those errors. In addition, the reference illuminance distribution for the image receiving member 7 can be accurately, easily, and quickly adjusted to be substantially uniform in each part as shown in FIG.

(2) Also, readjustment of the reference illuminance distribution d due to deterioration of the light source 3 over time, etc. can be done by adjusting the relative position of the slit plates 8a and 8b, which make up the entire illuminance distribution correction member, in the same way as described above, to adjust the transmitted light distribution characteristic b. 'l It is possible to readjust accurately, easily, and quickly just by making a central adjustment operation of making appropriate changes.

It should be noted that not only the slit plates 8a and 8bH have elongated holes formed as the openings 91 as shown in FIGS. 4 and 5, but also those having key metals formed in other suitable shapes such as squares and circles may also be used.

Also, the distance ij between the openings 91 along the length of the plates 8a and 8b is 4th.
・The spacing is not limited to regular spacing as shown in Figure 5, where the spacing gradually increases toward the left and right ends of the plate, but may be determined at appropriate intervals on a case-by-case basis.

In addition, the 8th illuminance distribution correction member 8a and BbK, which is a set of two sheets, is
・As shown in the example in Figure 9, 10,000 8b full slit plate, and the other 8a
'? It may be configured as a simple light shielding plate. Also, there are 10,000 plates so that it can be easily corrected when the illuminance distribution is asymmetrical. The rotational position may be adjusted to the lower left or lower right relative to the other plate. In the example shown in Figs. 8 and 9, one slit plate 8br is attached to the chassis of the device, etc. on the intermediate plate 10, and as in the example shown in Fig. 5, there are vertical screws 81, longitudinal holes 84, screws 86, etc. Assemble the vertical position freely and adjust the position with the other light shielding plate 8a'? Similarly, an example is shown in which it is assembled to the intermediate plate 10 with circular arc elongated holes 87, 87 and screws 8B, 88 so that the rotation can be freely adjusted. If the light shielding plate 8a' is also a slit plate, it becomes possible to perform more delicate correction adjustment of the light amount distribution.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an example of a conventional facsimile transmitter, Fig. 2 is a front view of a slit plate as an illuminance distribution correction member interposed in the imaging optical system, and Fig. 6 are graphs of various characteristics of the optical system. FIG. 4 shows two parts constituting the illuminance distribution correction member in the present invention.
Figure 5 is a front view of the two slit plates stacked together, and Figure 6 is the distribution of transmitted light through the illuminance distribution correction member by adjusting the relative position of the two slit plates. Figure 7 is a graph showing changes in characteristics of an example of a facsimile transmitter in which an illuminance distribution correction member consisting of two slit plates d is interposed in the optical path.
FIG. 8 is a view from the slit plate side of an example of a combination of a slit plate and a light shielding plate, and FIG. 9 is a view from the Fii light plate side. 1 original document (subject), 3 light source, 6 imaging lens, 7 one-dimensional solid-state image sensor array (image receiving member). 8, 8a, and 8b are illuminance distribution correction members. Patent applicant Canon Co., Ltd.

Claims (3)

[Claims] (1) In an imaging optical system including an illuminance distribution correction member that compensates for at least the C08J power law characteristic of the imaging lens to equalize the reference illuminance distribution along the light-receiving length of the image-receiving member. A first correction in which a plurality of apertures are formed along the length of a horizontally long plate surface as an illumination distribution correction member, with the interval between adjacent openings at the center of the plate surface and the interval between adjacent openings at the left and right ends of the plate being different. A plate and a second correction plate that can completely block each part of each aperture of the first correction plate are used, and the two-layered correction plate is used as an imaging optical system. The optical path of the system is interposed in such a way that the relative position can be freely adjusted along the plate surface. An imaging optical system characterized by: (2) The illuminance distribution correction member consisting of the two correction plates,
It is placed in the optical path from the object illumination light source to the object. An imaging optical system according to claim (1). (3) The illuminance distribution correction member consisting of the two correction plates,
It was placed in the optical path between the subject and the image receiving member. An imaging optical system according to claim (1).