JPH03213817A - Imaging element - Google Patents

Abstract

PURPOSE:To decrease the unequalness on an imaging plane by setting the unequalness of the imaging performance periodically formed in accordance with the arranging pitch of the lenses of a lens array and the unequalness of the imaging light quantity of an imaging plane in such a manner as to have different phases. CONSTITUTION:This imaging element has a roof mirror array 5 continuously formed with many pieces of optical path separating mirrors 2 and roof mirrors 6 to a straight line shape at a specified arranging pitch and the lenses 4 formed in correspondence to the arranging pitch of the roof mirrors 6. The unequalness of the imaging performance (MTF) periodically formed in accordance with the arranging pitch of the lenses 4 of the lens array 3 and the unequalness of the imaging light quantity of the imaging plane 7 are so set as to be shifted from each other by, for example, 1/2 phase. The fluctuation in the intensity by each of the respective dots generated by the unequalness A of the MTF is, therefore, set in the form of offsetting the unequalness of the light quantity of the imaging plane 7. The unequalness of the MTF characteristic on the imaging plane is decreased in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an imaging element used in an imaging optical system of a document reading section of a copying machine, facsimile machine, or image scanner.

2. Description of the Related Art An example of a conventional imaging element (roof mirror lens array) will be described with reference to FIG. The light from the object surface 1 is reflected by the reflective surface 2a formed on the upper side of the optical path separation mirror 2, passes through the lenses 4 formed with a constant arrangement pitch P in the lens array 3, and is reflected to the roof mirror array 5. The light enters and is reflected once by each of the two roof mirrors 6 formed in a roof shape that face each other on the left and right (2 reflections in total).
After passing through the lens array 3 again, this time,
By being reflected by the reflecting surface 2b formed on the lower side of the optical path separation mirror 2, an image is formed on an image forming surface (image surface) 7 that is in a conjugate positional relationship with the object surface 1, thereby making it possible to read the image. It will be done. Note that a diaphragm plate 8 (see FIG. 10) for blocking stray light is provided between the lens array 3 and the roof mirror array 5, and the arrangement pitch of the lens array 3, roof mirror array 5, and diaphragm plate 8 is P is in a matched state.

In this case, if the lens 4 has a rectangular shape, the light intensity distribution in the arrangement direction (Y direction) is approximated to an isosceles triangular shape symmetrical with respect to its tip axis, as shown in FIG. It has characteristics. That is, Fig. 8(a)(b)(c)
), when viewed from the rectangular opening of a certain lens 4, the light intensity distribution Ls of a single lens in the arrangement direction
The relationship is that the amount of light near the optical axis is large when Y=O, but when Y=0.5, Y=1. The amount of light gradually decreases as it moves away from O and the optical axis. Therefore, if we further look at this relationship when a plurality of lenses 4 are superimposed, the single light intensity distribution Ls will overlap with each other, and the combined light intensity distribution Lt will be a mountain, as shown in FIG. This results in a state where unevenness in the amount of light occurs.

Such a composite light amount distribution Lt is, as shown in FIG.
There is a relationship in which the unevenness of the amount of light disappears only when the value of the degree of overlap m (m=X/Da, where X: radius of field of view of the lens, Da: width of the lens in the array direction) approaches an integral multiple. Therefore, in the past, in order to eliminate the unevenness of the composite light amount distribution Lt as described above, the shape of the diaphragm plate 8 on the side closer to the roof mirror array 5 is changed to the shape on the side closer to the lens array 3, as shown in FIG. Form larger than the shape,
Thereby, by forming the aperture a on the side closer to the roof mirror array 5 of the aperture plate 8 to be narrower than the aperture a on the side closer to the lens array 3, the combined light amount distribution Lt is made uniform.

Problems to be Solved by the Invention Regarding the above-described apparatus, first, a first conventional example will be described. FIG. 5(a) shows the relationship between unevenness A in the imaging performance (MTF) that appears periodically in correspondence with the arrangement pitch of the roof mirrors 6 of the roof mirror array 5 and unevenness B in the light amount distribution on the imaging surface 7. This shows that. Also, Fig. 5(b)
shows the emission intensity distribution of phosphor dots when combined with a phosphor dot array. Furthermore, Fig. 5(c)
6 shows the dot intensity distribution on the imaging plane 7 when an image is formed using the imaging element (see FIG. 6). Further, FIG. 5(d) shows the density distribution of dots when a visible image is obtained using an electrophotographic process.

As can be seen from Figure 5(a), the MTF unevenness B
The distribution of and the distribution of the unevenness A of the light amount distribution on the imaging plane 7 are in the same phase. In this case, since the amount of blur for each dot differs depending on the size of the MTF, a difference occurs in the intensity for each dot (at the same time, the size of the dot also changes slightly due to the blur). In addition, since the unevenness B in the light intensity distribution of the imaging element is in the same phase, it is further amplified and the difference in intensity distribution increases (this situation can be seen in the dot intensity distribution on the imaging plane in Figure 5 (C)). ).

Now, an optical print head having such an intensity distribution is applied to an electrophotographic process as shown in FIG. section 13, static eliminating section 14, and charging section 1
5 is combined to obtain a visible image,
As shown in FIG. 5(d), there are periodic density differences in the arrangement direction. Therefore, in conventional imaging elements, although consideration has been given to controlling the light intensity distribution on the imaging surface, there is a problem in that the relationship with unevenness in imaging performance has not been considered. .

Next, the second problem with the conventional device described above will be described. FIG. 13 shows the arrangement pitch P of the lens array 3.
MTF characteristic characteristic ray that changes periodically in response to MT
F-characteristic characteristic (also referred to as light ray) and light quantity distribution characteristic b (dashed line, also referred to as unevenness of the light quantity distribution characteristic of the optical system) at the image plane 7.

However, here, only the optical system is shown), and their phases are shifted by P/2 from each other. In this case, the amount of light is large at the position of each lens optical axis 16, and the amount of light is small at the position of the midpoint of the lens optical axis 16.
The F-characteristic light intensity distribution characteristic has a shape opposite to that of the light intensity distribution characteristic.

In this way, the reason why the light phase of the MTF characteristic and the phase of the light intensity distribution characteristic are shifted by P/2 is to reduce these two types of unevenness as much as possible and correct the unevenness of the imaged light intensity on the imaging plane. It's for a reason.

However, the light source used in the conventional imaging element (here,
In the phosphor dot array), as shown in FIG. 13, the dot areas of the individual light sources 17 arranged in the array are all equal. Therefore, the light amount distribution when an image is formed on the image plane (actual image plane) is the same as the light amount distribution shown by the broken line described above. Furthermore, due to the MTF characteristics, the imaged dot area 18 on the imaging plane differs depending on the location, and it is not possible to correct and reduce the unevenness of the MTF characteristic light beam or the light amount distribution characteristic of the optical system. As a result, a problem arises in that a high-quality image cannot be obtained.

Means for Solving the Problem Therefore, in order to solve such problems, claim 1
The described invention includes an optical path separating mirror, a roof mirror array in which a plurality of roof mirrors are continuously formed in a straight line at a constant arrangement pitch, and a roof mirror array located between the roof mirror array and the optical path separating mirror, In an imaging element comprising a lens array having lenses formed corresponding to an array pitch, and an aperture plate located between this lens array and the roof mirror array to block stray light, the arrangement of the lenses of the lens array is It is set so that the unevenness in imaging performance, which is periodically formed in correspondence with the pitch, and the unevenness in the amount of imaged light on the imaging plane have different phases.

The invention as set forth in claim 2 is provided with a light source arranged in a 7-dot array, and in which the lenses are arranged in a constant array. blood.

a roof mirror array in which a large number of roof-shaped reflective surfaces are arranged corresponding to the arrangement pitch P of the lens array; and a roof mirror array provided between the roof mirror array and the lens array. The phase of the imaging characteristic, which changes periodically corresponding to the arrangement pitch P of the lens array, and the phase of the light quantity distribution characteristic of the image plane are mutually P/2. In the staggered imaging elements, the dot area of the light source is set to be large at a position where the value of the imaging characteristic is high, and the dot area of the light source is set to be small at a position where the value of the imaging characteristic is low.

Effects According to the invention described in claim 1, by using a configuration in which the phase due to unevenness in imaging performance and the phase due to unevenness in the amount of imaged light on the imaging surface are superimposed as opposite phases, an image forming element can be used. The intensity unevenness of the imaged tod can be corrected and flattened.

According to the invention as claimed in claim 2, the size of the dot area of the light source is changed in accordance with the unevenness of the imaging characteristic, that is, the MTF characteristic, and the unevenness of the light quantity distribution characteristic of the image plane, that is, the unevenness of the light quantity distribution characteristic of the optical system. Accordingly, it is possible to reduce the unevenness by simultaneously correcting the unevenness of the MTF characteristics on the actual imaging plane and the unevenness of the light amount distribution characteristic of the optical system, thereby making it possible to obtain a high-quality image.

Embodiment An embodiment of the invention set forth in claim 1 will be described based on FIG. The overall configuration of the imaging element has been described in the prior art (see FIG. 6), so its explanation will be omitted, and the same parts will be denoted by the same reference numerals.

As shown in FIG. 6, an optical path separating mirror 2, a roof mirror array 5 in which a large number of roof mirrors 6 are continuously formed linearly at a constant pitch, and a combination of the roof mirror array 5 and the optical path separating mirror 2. a lens array 3 having lenses 4 located therebetween and formed corresponding to the arrangement pitch of the roof mirrors 6; and an aperture plate 8 located between the lens array 3 and the roof mirror array 5 to block stray light. (
In this embodiment, in an imaging element consisting of an imaging surface (see FIG. The unevenness in the amount of image light on the image plane 7 is set to be shifted by 1/2 phase from each other. Therefore, the reason why the phase of the light amount distribution is shifted by l/2 will be described below using a specific example.

Figures 1 (a) to (d) are similar to Figure 5 (a) described in the prior art.
) to (d), respectively. in this case,
As can be seen from Fig. 1(a), the MTF unevenness A and the unevenness B of the imaging light amount on the imaging surface 7 are set with a phase shift of about 1/2, so the MTF unevenness A The generated intensity variation for each dot cancels out the variation in the unevenness of the light amount on the imaging surface 7, and the difference in dot intensity distribution on the imaging surface 7 is significantly improved as shown in FIG. 1(c). It turns out. When this is combined with the electrophotographic process used in the conventional example (see Figure 12) to obtain a visible image, Figure 1 (d
), it is no longer necessary to consider the density difference between each dot separately and it can be almost ignored, making it possible to obtain a clear image without density unevenness depending on the location.

A first embodiment of the invention as claimed in claim 2 will be described based on FIG. The overall configuration of the imaging element has been described in the prior art (see FIG. 6), so a detailed explanation will be omitted here, and the same parts will be denoted by the same reference numerals.

As shown in FIG. 2, the imaging element has an unevenness a in imaging characteristics (hereinafter referred to as an unevenness a in MTF characteristics) that periodically changes in accordance with the arrangement pitch P of the lens array 3 (see FIG. 6). call)
The phase of the light intensity distribution characteristic b of the image plane 7 (hereinafter referred to as unevenness b of the light intensity distribution) is shifted by P/2 from each other.

In this case, the dots C of the phosphor dot array tube 19 serving as a light source are set to be large at a position where the MTF characteristic a is high (the midpoint of the lens optical axis 16), and are set to be small at a position where the MTF characteristic a is low (the lens optical axis 16). It is set to be. In other words, the dots C of the phosphor dot array tube 19 are formed small at positions where the amount of light is high (lens optical axis 16), and are formed large at positions where the amount of light is low (midpoint of the lens optical axis 16). Further, in the area between the maximum and minimum areas, the dot area is set based on a similar relationship.

In this way, by changing the shape of the dots C of the phosphor dot array tube 19 in response to the unevenness of the MTF characteristic a and the unevenness of the light intensity distribution, the light intensity distribution d on the image forming plane (actual image plane) can be changed. , are almost uniform (linear) as shown in FIG. 2, and as a result, the dot areas e on the imaging plane are all equal. Therefore, it is possible to simultaneously correct the unevenness of the MTF characteristic a on the imaging plane and the unevenness of the light intensity distribution characteristic of the optical system, thereby reducing the unevenness of the light intensity, resulting in a much higher quality image than before. can be obtained.

Next, a second embodiment of the invention as claimed in claim 2 will be described based on FIG. In this embodiment, as in the first embodiment, the shape of the phosphor dot array tube 19 as a light source is changed in accordance with the unevenness of the MTF characteristics and the unevenness of the light amount distribution. Since the MTF characteristics in the sub-scanning direction X, which is orthogonal to
The shapes of the dots C are all the same, and the shape of the dots C is changed only in the lens arrangement direction Y, which is the main scanning direction.

In addition, the relationship between the unevenness of the MTF characteristic a and the unevenness of the light amount distribution is determined by shifting the phase by approximately P/2 from each other.
The maximum position of the unevenness of the TF characteristic a and the unevenness of the light amount distribution is different from the first embodiment, and is set so that the unevenness of the MTF characteristic a becomes maximum at the position of the lens optical axis 16.

Here, an example of comparing the light intensity distribution of a single lens system and a composite lens system with respect to the degree of overlap m of the imaging elements is shown in Figure 9 (
Shown in a) and (b). In this figure, the vertical axis represents the amount of light, and the horizontal axis represents the lens arrangement direction. Furthermore, FIGS. 10 and 11 are shown in Japanese Patent Application No. 63-1430 filed by the present applicant.
This is described in the application filed as No. 86, and shows a correction method that can make the combined light amount distribution uniform by changing the aperture shape of the diaphragm plate 8. Therefore, it can be seen that it is possible to easily shift the phase of the MTF characteristic a and the phase of the light amount distribution by P/2.

Next, a third embodiment of the invention set forth in claim 2 will be described based on FIG. 4. In this embodiment, an electrophotographic recording apparatus 20 is constructed using the phosphor dot array tube 19 as a light source for an optical printer described in the two embodiments described above. The photoreceptor 21 rotates in the direction of the arrow, and a charger 22 is placed around it.
, developing section 23, transfer charger 24, cleaning section 2
5. A static elimination lamp 26 is arranged. The imaging element including the phosphor dot array tube 19 is located between the charger 22 and the developing section 23.

Therefore, by changing the shape of the dots C of the phosphor dot array tube 19 in accordance with the unevenness of the MTF characteristic a and the unevenness of the light amount distribution, the photoreceptor 21 and the transfer charger 2
4, it is possible to obtain a clear, high-quality image with reduced unevenness in the MTF characteristic a and unevenness in the light amount distribution.

Although the case where the phosphor dot array tube 19 is used as a light source has been described, in addition to this, an LED array, an LCS
(Liquid crystal shutter) array etc. can also be used. However, LCS is not self-luminous and requires a separate light source.
Since the shutter function of the liquid crystal is used to turn on and off the light, this is equivalent to changing the aperture shape of one dot of the liquid crystal.

Effects of the Invention The invention according to claim 1 provides an optical path separating mirror, a roof mirror array in which a large number of roof mirrors are continuously formed in a straight line at a constant arrangement pitch, and between this roof mirror array and the optical path separating mirror. An imaging element comprising a lens array having lenses arranged in correspondence with the array pitch of the roof mirrors, and an aperture plate located between the lens array and the roof mirror array to block stray light, The unevenness in imaging performance, which is periodically formed in accordance with the arrangement pitch of the lenses in the lens array, and the unevenness in the amount of light formed on the imaging surface are set to have different phases, so that the unevenness in imaging performance can be reduced. By adopting a configuration in which the phase and the phase of unevenness in the amount of imaged light on the imaging plane are superimposed as opposite phases, it is possible to correct and flatten the intensity unevenness of the tod imaged using the imaging element. This eliminates the unevenness of density that occurs in the conventional method and makes it possible to obtain clear images.

The invention as claimed in claim 2 provides a lens array including light sources arranged in a dot array shape, a lens array in which a large number of lenses are arranged at a constant arrangement pitch P, and a roof-type reflector corresponding to the arrangement pitch P of this lens array. It consists of a roof mirror array in which a large number of surfaces are arranged, a diaphragm plate provided between the roof mirror array and the lens array, and an optical path separation mirror, and the arrangement pitch P of the lens array is
In an imaging element in which the phase of an imaging characteristic that changes periodically in response to the image plane and the phase of the light amount distribution characteristic of the image plane are shifted from each other by P/2, the Since the dot area of the light source is set large and the dot area of the light source is set small at the position where the value of the imaging characteristic is low, the unevenness of the imaging characteristic, that is, the MTF characteristic, and the light intensity distribution characteristic of the image plane, that is, By changing the size of the dot area of the light source in accordance with the unevenness of the light intensity distribution characteristics of the optical system, these MTFs on the actual image forming plane can be adjusted.
It is possible to reduce the unevenness by simultaneously correcting the unevenness in the characteristics and the unevenness in the light amount distribution characteristic of the optical system, thereby making it possible to obtain a high-quality image.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing how light intensity unevenness is corrected according to an embodiment of the invention as claimed in claim I, FIG. 2 is an explanatory diagram showing a first embodiment of the invention as claimed in claim 2, and FIG. The figure is an explanatory diagram showing a second embodiment of the invention as claimed in claim 2, FIG. 4 is an explanatory diagram showing a third embodiment of the invention as claimed in claim 2, and FIG. 5 is an explanatory diagram showing a third embodiment of the invention as claimed in claim 2. 6 is a perspective view showing the structure of the imaging element, FIGS. 7 and 8 are explanatory diagrams showing how the light amount distribution changes depending on the lens aperture shape, and FIG. 9 is an explanatory diagram showing the overlapping An explanatory diagram showing the state of the light quantity distribution of a single lens system and a composite lens system with respect to the power, Fig. 10 is an explanatory diagram showing the state of the light quantity change in the arrangement direction when multiple lenses are connected, and Fig. 11 is an explanatory diagram showing the state of the light quantity distribution in the arrangement direction when multiple lenses are connected. Fig. 12 is an explanatory diagram showing how unevenness in light amount is adjusted by changing the shape of the end of the diaphragm plate, Fig. 12 is a configuration diagram showing the state when the imaging element is combined with the electrophotographic process, and Fig. 13 is FIG. 2 is an explanatory diagram showing a conventional light amount distribution. 2... Optical path separation mirror 3... Lens array, 4...
... Lens, 5... Roof mirror array, 6... Roof mirror, 7... Image forming surface, 8... Aperture plate, A...
・Unevenness in imaging performance, B...Unevenness in imaging light amount, a...
Imaging characteristics, b... light intensity distribution characteristics, C... dots, e
... Dottsu Area Applicant Riko Co., Ltd. (d) Dora l - Fuju - House ■■■■■■■ Cabinet ■■■ Intestine ■ Hitoshi - Otori's first breath: A>B>C,>D 1 Figure i Figure 37 Rumi L Kushite (a) (b) に) Read diagram (a) See-shitsusu°5 ((b) Kinzoku Shinzue, 3. JO diagram t 7-ho) Figure [shi J) JZ diagram-2

Claims (1)

[Scope of Claims] 1. An optical path separating mirror, a roof mirror array in which a large number of roof mirrors are continuously formed in a straight line at a constant arrangement pitch, and an optical path separating mirror located between the roof mirror array and the optical path separating mirror; An imaging element comprising a lens array having lenses formed corresponding to the arrangement pitch of the roof mirrors, and a diaphragm plate positioned between the lens array and the roof mirror array to block stray light, the lens array An imaging element characterized in that the unevenness in imaging performance, which is periodically formed in accordance with the array pitch of the lenses, and the unevenness in the amount of imaged light on the imaging surface are set to have different phases. 2. A lens array including a light source arranged in a dot array, in which a large number of lenses are arranged at a constant arrangement pitch P, and a large number of roof-shaped reflective surfaces arranged in correspondence with the arrangement pitch P of this lens array. a roof mirror array, a diaphragm plate provided between the roof mirror array and the lens array, and an optical path separation mirror,
In the imaging element, the imaging element is provided such that the phase of the imaging characteristic that changes periodically corresponding to the arrangement pitch P of the lens array and the phase of the light amount distribution characteristic of the image plane are shifted by P/2 from each other. An imaging element characterized in that a dot area of the light source is set large at a position where the value of the imaging characteristic is high, and a dot area of the light source is set small at a position where the value of the imaging characteristic is low.