JPH0471388B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image scanning light receiving device that receives light from an original image on a light receiving surface of a photomultiplier tube.

[Prior Art] A conventional input scanning unit in an image scanning recording apparatus such as a black and white scanner, a color scanner, and a facsimile for photolithography is constructed as shown in FIG.

That is, an original image 2 mounted on a rotary cylinder 1 is illuminated with a spot by a light source (not shown), and transmitted light or reflected light from the original image 2 is collected by a pick-up lens 3.
The light beam S obtained by scanning the original image 2 is made to pass through a main aperture 4 and then guided to a photomultiplier tube 5 (hereinafter referred to as photomultiplier).

By the way, when using an image scanning recording device, the line width for scanning the original image 2 (hereinafter referred to as scanning line width)
From an economic point of view, it is desirable to have as wide (coarse) as possible because scanning can be done in a short time.
On the other hand, from a quality standpoint, it is desirable to scan the original image 2 as finely as possible, and this is especially necessary when recording at a high reproduction magnification.

In this way, it is necessary to scan with the optimal scanning line width depending on the replication magnification setting, and the main aperture 4
is for adjusting the scanning line width by changing the aperture size.

Therefore, the main diaphragm 4 is a diaphragm that limits the field of view from the photographic light receiving surface 5' to the original image 2;
In other words, it functions as a field diaphragm,
The main aperture 4 is installed at a position where the image of the original image 2 is formed by the pick-up lens 3.

However, as a result, an inconvenience arises in that a blurred image is also formed on the photoreceptive surface 5' behind the main aperture 4. In other words, although the photosensitive surface 5' should have uniform sensitivity, in reality, the sensitivity differs depending on the location, and in short, the sensitivity distribution is not uniform.

Therefore, the highlight part of the blurred image formed on the photoreceptive surface 5' at a location where the scanning line straddles the boundary part where the highlight part and the shadow part are adjacent in the original image 2 is If the imaging position of the part is a relatively high-sensitivity part on the photo-receiving surface 5', this scanned part will be detected brighter than the actual one; is also detected darkly.

In this way, with conventional light receiving devices, a blurred image is formed on the photosensitive surface 5', so even if there is no problem when scanning the uniform sensitivity part of the original image 2, the outline of the image is When scanning areas with strong contrast such as
The operation became unstable and the reproducibility of recorded images deteriorated.

Therefore, as a light-receiving device that solves this inconvenience, for example, as shown in Fig.
It has been proposed that a diffuser plate 6 is installed just before the light beam S to scatter the light beam S and then guide it to the photodetector surface 5'.

[Problems to be Solved by the Invention] However, the conventional light receiving device described above has the disadvantage that it requires a very high brightness light source to illuminate the original image 2 because the diffuser plate 6 significantly reduces the amount of light. be.

In addition, in conventional light receiving devices, when the aperture size of the main aperture 4 is increased to increase the scanning line width, the area (hereinafter referred to as light receiving area (φG)) over which the luminous flux S irradiates the photosensitive surface 5' also increases. Become,
On the contrary, when the aperture size is made smaller, the light receiving area φG also becomes smaller.

Therefore, if the light-receiving area φG becomes too small, as mentioned above, the sensitivity distribution of the photo-receiving surface 5' will not be uniform, so even if the position of the photo-receptor 5 is slightly shifted due to vibration etc., the detection results will fluctuate. . Furthermore, if the required light receiving area φG is so large that it protrudes beyond the photodetecting surface 5', there is a problem that light cannot be received accurately.

Therefore, with conventional light receiving devices, it is not possible to make the scanning line width too wide so that the size of the light receiving area φG does not deviate from a good range. In some cases, this became an obstacle.

Therefore, in order to solve these inconveniences, for each of the 51 photomals, on each light receiving surface,
Consideration has been given to selecting a portion with a relatively uniform sensitivity distribution and adjusting the position of the photomultiplier 5 so that light is received in that portion. In addition, each main diaphragm 4 of each aperture size is adjusted to be offset from the optical axis by an appropriate distance, so that light is received in the part with the most uniform light receiving sensitivity in the width of each light receiving area φG. It is also being considered.

However, these adjustment operations are usually performed by trial and error, which is complicated and requires a lot of time. especially. Like a color scanner, the main diaphragm 4 with a wide replication magnification range and more than 10 different aperture sizes is selectively used, and the light beam that photoelectrically scans the original image 2 is divided into separate formats 5 for each color component signal of red, blue, and green. In an apparatus in which the light is incident on the light source and each color separation signal is obtained, such adjustment is an extremely complicated task.

The present invention has been made in order to solve the above-mentioned problems in the conventional light-receiving device, and it is possible to prevent a blurred image from being formed on the photo-receiving surface 5' and to change the scanning line width. Another object of the present invention is to provide an image scanning light-receiving device in which the light-receiving area φG hardly changes, and recording magnification can be set over a wide range.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention forms an image of the original image in an image scanning light receiving device that receives light from the original image on the light receiving surface of a photomultiplier tube. A pick-up lens, a main diaphragm installed at an imaging position where an image of the original image is formed by the pick-up lens, and a front focal point substantially aligned with the imaging position between the pick-up lens and the photomultiplier tube. and an optical system installed in the photomultiplier tube, and the photomultiplier tube is installed in the vicinity of a position where the light passing through the optical system is most converged so that the light receiving surface is in an optical conjugate relationship with the pick-up lens. has been done.

[Operation] Forms an image of the original image with the pick-up lens,
A main diaphragm is installed at the imaging position and functions as a field diaphragm to limit the field of view in the original image. Then, an optical system is installed so that the front focal point of the optical system almost coincides with the above-mentioned image forming position, and the optical system collimates the light beam passing through the main diaphragm so that it is received by the light receiving surface of the photomultiplier tube. Also,
The photomultiplier tube is installed near the position where the light passing through the optical system is most converged so that the light receiving surface is in an optically conjugate relationship with the pick-up lens.

As a result, even if the scanning line width is changed by changing the aperture size of the main aperture, the light-receiving area on the photomultiplier tube's light-receiving surface does not change, and a blurred image is formed on this light-receiving surface. There will be no more.

[Example] Hereinafter, an example of the present invention will be described based on the drawings.

FIG. 3 shows the configuration of an embodiment of the image scanning light receiving device of the present invention.

In this light receiving device, the pick-up lens 3
The main aperture 4 is a known one, and the main aperture 4 is installed at the imaging position where the image of the original image 2 is formed by the pick-up lens 3, and the main aperture 4 is set so as to limit the field of view of the original image 2. The main aperture 4 functions as a so-called field diaphragm.
By changing the mechanical dimensions of the scanning line width, the width of the scanning line can be changed.

The optical system 10 installed between the main diaphragm 4 and the photomultiplier 5 is configured to control the light flux S, as will be described in detail later.
into almost parallel light and guide it to the photo-receiving surface 5'.
Moreover, even if the aperture size of the main diaphragm 4 is changed, the light receiving area φS hardly changes. The front focal point F of this optical system 10 is installed so as to match the position of the main aperture 4, that is, the imaging position where the image of the original image 2 is formed.

However, due to the influence of lens aberrations, etc., it is impossible to make the image formation position by the pickup lens 3 and the front focal point F of the optical system 10 completely coincide with each other, so it is only necessary to make them almost coincide with each other.

Further, a known photomultiplier 5 is used, and the position on the optical axis where it is installed will be described later. Note that, as with conventional light receiving devices, it is necessary to move the photomal 5 in a direction perpendicular to the optical axis and make adjustments so that the light beam S is received in a portion of the photomal receiving surface 5' where the sensitivity distribution is as uniform as possible. There isn't.

Next, FIG. 4 shows the optical path of the light beam S up to the photo-receiving surface 5', and clarifies the relationship between the light-receiving device of the present invention and its effects.

In Fig. 4, the area between solid lines a ₁ and a ₂ is
This shows the luminous flux from point A at the end of the scanning line on the original image 2 when the aperture size of the main aperture 4 is maximized.The area between solid lines b ₁ and b ₂ is the optical axis relative to point A. It shows the light flux from point B, which is the end of the scanning line on the original image 2, which is located at a symmetrical position with the two sides in between.

In this light-receiving device, the main aperture 4 is installed at the position where the original image 2 is imaged by the pick-up lens 3, so the light flux passes through point A', the position where point A is imaged, and reaches the optical system 10. , and reaches the optical system 10 through the image-forming position B' of point B.

Further, since the imaging position of the original image 2 by the pick-up lens 3 and the front focal point F of the optical system 10 are made to match, the light flux, after passing through the optical system 10, reaches the point A' and the optical axis center O of the optical system 10. A parallel light flux A* is parallel to the straight line connecting the points, and after passing through the optical system 10, the light flux becomes a parallel light flux B* parallel to the straight line connecting points B' and O.
becomes.

The ray a* passing through the center of the parallel beam A* and the ray b* passing through the center of the parallel beam B* intersect at a point G on the optical axis of the plane 5', as shown in FIG.

By the way, compared to the distance between the pick-up lens 3 and the main aperture 4 (for example, 200 mm in this embodiment), the aperture size of the main aperture 4 is very small (about several millimeters at most).
From the position of Pick Up Lens 3, the
Point A' and point B' can be considered to be at almost the same position. Therefore, the spot diameter φ of the luminous flux and the spot diameter φ of the luminous flux are almost equal, and the spot diameter φA* of the parallel luminous flux A* and the spot diameter φ of the parallel luminous flux B* are approximately equal.
B* can be considered to be approximately equal.

As is clear from the above, the light flux and the light flux B (that is, the light fluxes A* and B*) are centered on the plane 5' perpendicular to the optical axis at the point G,
It passes with the same spot diameter φA*=φB*).

In this way, in this light receiving device, no matter where the light comes from on the scanning line, the area on which the light irradiates the plane 5' perpendicular to the optical axis at point G is the same. In addition, such G point is experimentally determined as follows.
It can be determined as the position where the light beam S is most converged after passing through the optical system 10, and the photo-receiving surface is installed at such a position. and,
This photo-receiving surface is the Pickup Lens 3.
and has an optical conjugate relationship.

Therefore, when a photodetector surface is arranged on the plane 5', the light-receiving area φG hardly changes even if the scanning line width is changed by changing the aperture size of the main aperture 4.

As a result, unlike conventional light receiving devices, when the scanning line width is reduced, the light receiving area φG becomes smaller, and the light receiving sensitivity does not fluctuate even if the position of the photoprint 5 shifts slightly due to vibration or the like. In addition, if the scanning line width is increased, the required light receiving area φG
There will be no problem such as the image becoming larger than the photo-receiving surface 5', and even if the scanning line width is varied over a fairly wide range, no problem will occur.

In this way, the light receiving device of the present invention allows the scanning line width to be changed over a wider range than the conventional light receiving device, and therefore the setting range of recording magnification can be widened.

Moreover, both the luminous flux and the optical system 10
As can be understood from the fact that after passing through the optical system 10, the light becomes parallel light, light from any position on the scanning line becomes parallel light after passing through the optical system 10, and a blurred image is formed. The light reaches the photo-receiving surface 5' in a uniform distribution.

Therefore, even when scanning a high-contrast area such as the outline of an image, unlike conventional light receiving devices, light from any point within the scanning line will not reach a specific part of the photosensitive surface 5'. There will be no problems if the image is damaged, the operation of the Photomaru 5 will be stable, and the reproducibility of recorded images can be expected to be improved.

Furthermore, in order to stabilize the operation of the photomultiplier 5, the complicated work of adjusting the installation position of the photoprinter 5 with respect to the main aperture 4, which takes a lot of time, becomes unnecessary.

Furthermore, the luminous flux S after passing through the optical system 10
Since the spot diameter does not change much, there is no problem even if the position where the photoprint is installed is slightly shifted from the above-mentioned point G, and the light-receiving area φG also hardly changes.
Therefore, it is not necessary that the photo-receiving surface 5' perfectly coincides with the above-mentioned point G, but it may be placed at or near the point G.

In particular, in devices such as color scanners that use half mirrors to distribute the light beam S into a large number of photoprints, assembly precision is not required, and there is no difference in the light receiving area φG for each photoprint, which is convenient. You can expect an improvement in balance.

In addition, although the above-mentioned Example demonstrated the case where one optical system 10 was used, it may be comprised with a plurality of lenses.

For example, in the embodiment of FIG.
It is composed of two convex lenses such as the primary lens 11 and the secondary lens 12. The focal point F is located at the main aperture 4. By configuring the optical system 10 in this way, the dimension from the main aperture 4 to the photo frame 5 can be reduced.

In addition, the seventh
A concave lens may be combined as in the embodiment shown in FIG. 8 and FIG.

In the embodiment shown in FIG. 7, the focal point f' of the convex lens 14 is arranged so as to coincide with the virtual image point of the main aperture 4 formed by the concave lens 13. In the embodiment shown in FIG. 8, the imaginary focus f'' of the concave lens 18 is placed so as to coincide with the image point of the main aperture 4 formed by the convex lens 15.

[Effects of the Invention] As detailed above, according to the image scanning light receiving device of the present invention, the main aperture is installed at the imaging position where the image of the original image is formed by the pick-up lens, and the optical system is installed at the imaging position. Install the optical system so that the front focal points of the optical system almost coincide with each other, and place a photomultiplier tube near the position where the light passing through the optical system is most convergent, so that the light-receiving surface is in an optically conjugate relationship with the pick-up lens. Because it is installed, the light-receiving area on the light-receiving surface does not change even if the scanning line width is changed using the main aperture.
The sensitivity distribution becomes uniform, and as a result, the setting range of recording magnification can be widened.

Further, since the light beam becomes parallel light after passing through the optical system, it is possible to prevent a blurred image from being formed on the light receiving surface.

Furthermore, since the light-receiving sensitivity on the light-receiving surface becomes uniform, the complicated work of adjusting the positions of the photomultiplier tube and the main aperture becomes unnecessary.

[Brief explanation of the drawing]

FIG. 1 shows a conventional light receiving device in an image scanning light receiving device, FIG. 2 shows a conventional light receiving device using a diffuser plate, and FIG. 3 shows the configuration of an embodiment of the image scanning light receiving device of the present invention. , FIGS. 4 and 5 respectively show the optical path in the above embodiment, and FIGS. 6 to 8 show other embodiments of the optical system. 1...Rotating cylinder, 2...Original image, 3...Pick-up lens, 4...Main aperture, 5...Photomar, 5'...Photomal light receiving surface, 10...Optical system, S...Luminous flux.

Claims (1)

[Scope of Claims] 1. An image scanning light-receiving device that receives light from an original image on a light-receiving surface of a photomultiplier tube, comprising: a pick-up lens that forms an image of the original image; and a lens that forms an image of the original image by the pick-up lens. a main diaphragm installed at an image position; and an optical system installed between the pick-up lens and the photomultiplier tube with a front focal point substantially matching the image formation position, and the photomultiplier An image scanning light-receiving device, characterized in that the tube is installed near a position where light passing through the optical system is most converged so that its light-receiving surface is in an optically conjugate relationship with the pick-up lens.