JPH053946B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a linear image sensor that photoelectrically converts a projected image, and more particularly to a linear image sensor that prevents ghosts from occurring in output images.

[Background of the invention]

FIG. 13 is a sectional view showing a conventional linear image sensor, and FIG. 14 is a front view of the linear image sensor shown in FIG. 13, viewed from the light input information incident side. In the figure, 1 is a ceramic package, 2
is a window glass, that is, a transparent plate-like member, and is a pixel row 3, which will be described later, which is housed in a ceramic package 1.
This is to protect the element surface etc. Reference numeral 3 denotes a pixel column, which constitutes a light receiving area consisting of photoelectric conversion elements linearly arranged in the center of the recessed portion of the ceramic package 1. 4a and 4b are storage electrodes, which are connected to the pixel column 3.
The pixel row 3 and the storage electrode 4 are arranged in parallel on both sides of the
a and 4b are alternately connected by bonding wires. The electric signal photoelectrically converted by the pixel row 3, that is, the received light information, is transferred to the storage electrode 4.
The data is stored once in the storage area provided with the signals a and 4b, and then sequentially read out from a readout area such as a shift register.

In the conventional image sensor having the above structure, the electrodes 4a and 4b are light reflecting surfaces close to mirror surfaces. Therefore, when light a from a certain direction and at a certain angle enters through the window glass 2, it is reflected on the surface of the electrode 4b and becomes reflected light a ₁ , which is re-reflected on the lower surface 2b of the window glass 2 and becomes twice reflected light. a ₂
Thus, pixel row 3 is reached. In this case, the combined level of the twice-reflected light a ₂ of the incident light a and the directly incident light b will be output as information about the light b. However, the intensity of the twice reflected light a ₂ is only about 4% of the directly incident light a because it is reflected from the glass surface. Therefore, if the intensities of incident light b and incident light a are the same, the combined value of b and a ₂ will be only 4% more than b. The actual problem is that when the incident light a is strong and the incident light b is small or 0, for example in the case of a picture with high contrast, a ₂ is added to the information of b, which is originally 0 or close to 0, so the output is It will come out. In other words, a ghost phenomenon occurs in which a faintly identical image appears at a position slightly shifted from the image created by direct projection light. If an image processing device using a linear image sensor binarizes the input signal and uses it, the signal level due to the twice reflected light a ₂ is itself small and may not be affected, but the device that reproduces the gradation In this case, even a few percent of the signal is expressed on the output surface. Therefore, the device must be provided with means to prevent ghosting.

As a device for reproducing gradation, there is a "direct transmission device" that directly transmits images from 35mm photographic film (positive or negative), for example, but this device prevents ghosting from occurring when inputting transparent originals with gradation. In order to do this, it is necessary to have a complex structure in which a linear image sensor is scanned and at the same time a slit light source, which is a light source covered with a slit, is moved.

As mentioned above, conventional linear image sensors have a light reflection area with a high reflectance placed around the pixel row, that is, around the light receiving area, which causes ghosts in the output and makes it impossible to reproduce an output image that is faithful to the original image. There were flaws.

Note that this drawback is limited to linear sensors (line sensors, linear sensors). because,
In the case of a surface sensor, the electrode is installed near the periphery of the light receiving surface, so its influence is limited to the periphery of the light receiving surface.
This is because it does not significantly affect the overall image quality, so it is not a problem.

[Purpose of the invention]

This invention was made in order to solve the above-mentioned drawbacks, and provides a linear image sensor that can faithfully reproduce the original image without ghosting by blocking the light source that illuminates the light-reflecting area. The purpose is to obtain.

[Summary of the invention]

This invention provides a transparent plate-like member with a mask that blocks the light rays irradiated onto the light reflecting area.
In addition to eliminating reflections that are harmful to linear image sensors and preventing the occurrence of ghost phenomena, this method also prevents the occurrence of ghost phenomena when the light rays irradiated to the light reflection area cannot be completely blocked due to errors in the mounting position of the mask, or when the effective luminous flux is reduced. When light is blocked by a mask, by tilting the substrate on which the pixels of the linear image sensor are arranged and the transparent plate-like member with respect to the optical axis, the location where ghosts occur can be changed to a location that is less visually noticeable. , the technical point is to avoid blocking of the effective luminous flux.

〔Example〕

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, FIG. 3 is a top view showing the arrangement of elements of an image processing device using a linear image sensor, and FIG. 4, 5, and 6 are explanatory diagrams for explaining the principle of the present invention, and FIG. 7 is a first diagram showing the relationship between the mask attachment position and the ghost phenomenon.
FIG. 8 is an explanatory diagram showing the linear image sensor shown in FIG. 7 in a tilted state, and FIG.
An explanatory diagram corresponding to FIG. 7 showing an output image of information on a transparent original inputted to the image processing device shown in FIG.
FIG. 10 is an explanatory diagram that similarly shows the output image and corresponds to FIG. 8, FIG. 11 is a second explanatory diagram showing the relationship between the mask pasting position and the ghost phenomenon, and FIG.
The figure is an explanatory diagram showing a state in which the linear image sensor shown in FIG. 11 is tilted.

In FIGS. 1 and 2, 5 is the slit 5a.
with a mask having the upper surface 2a of the window glass 2.
It is pasted on. This mask 5 plays the role of blocking the incident light rays that cause the ghost phenomenon.As will be explained in detail below, this mask 5 eliminates the light rays that enter the storage electrodes 4a and 4b, so that the light rays are re-reflected by the window glass. No light rays are generated. Therefore, the occurrence of ghosts is prevented.

FIG. 3 is a top view showing the arrangement of elements of an image processing device using this linear image sensor, such as a ``direct transmission device'' that directly transmits images from 35 mm photographic film (positive or negative). In FIG. 3, 6 is an illumination lamp that is a light source, 7 is a projection lens group made up of several lenses, 8 is a transmission original, 9 is a projection lens group made up of several lenses, 10 is a projection area, and this projection area 10 is a linear image sensor 1
Scan with 1.

Transparent original 8 with gradation by this image processing device
To input the original, insert the original 8 between the projection lens group 7 and the projection lens group 9, and uniformly illuminate the original 8 with the illumination light of the lamp 6 through the projection lens group 7. The transmitted light from 8 is projected onto a projection area 10 by a projection lens group 9. Then, when the linear image sensor 11 is scanned along the projection area 10, the image information of the original 8 is converted into an electrical signal.

Next, the principle of this invention will be explained. Fourth
In the figure, reference numerals 12a and 12b indicate incident light regions where the ghost phenomenon occurs. These incident light areas 12a, 12b are limited to the incident light to the storage electrodes (hereinafter abbreviated as electrodes) 4a, 4b for the reason mentioned above, and the incident light rays 12c, 12d and 1
2e and 12f are from the light reflection side, from the pixel row 3 to the lower surface 2b of the window glass (hereinafter abbreviated as glass).
This can be obtained by knowing the distance h ₁ from the pixel row 3 to the electrodes 4a, 4b and the distances 14a, 14c, 14b, 14d from the pixel row 3 to the electrodes 4a, 4b.

Therefore, in order to eliminate the ghost phenomenon, it is sufficient to provide a mask 5 that blocks light from the incident light areas 12a and 12b where the ghost phenomenon occurs. By the way, as shown in FIG. 3, the linear image sensor 11 scans the projection area 10, but the incident light area of transmitted light necessary for image input throughout the entire scanning area is
It is limited to a certain range 13 (FIG. 4). Therefore,
When blocking the incident light 12a, 12b that causes the ghost phenomenon, it is necessary to avoid blocking this effective incident area 13. This light shielding can be performed between the illumination light source 6 and the transparent original 8, or between the projection optical system 9 and the linear image sensor 11, as shown in FIG. It is inappropriate if 6 is fixed. In the latter case, as can be seen from FIG. 4, as it moves away from the glass 2 in the direction of the transparent original 8, the effective incident area 13 and the incident light areas 12a and 12b that cause ghosting overlap and enter the effective incident area 13. . Therefore, the incident light area 12a, 1 causes a ghost phenomenon without blocking the effective incident area 13.
In order to shield 2b from light, it must be done as close as possible to the top surface of the glass 2a. That is, it is best to block light at the top surface 2a of the glass as shown in FIG.

By the way, when pasting this mask 5, the pasting accuracy differs depending on the distance from the pixel surface 3 to the glass lower surface 2b (hereinafter referred to as glass height). In FIGS. 5 and 6, similar to FIG. 4, the incident light areas where the ghost phenomenon occurs are indicated by 15a, 15b and 16a, 16b. In Fig. 5, the glass height _h2 is higher than the glass height _h1 in Fig. 4, and as a result, the incident light areas 15a and 15b that cause the ghost phenomenon are moved in the direction of the optical axis 17 compared to the case in Fig. 4. do. As a result, on the glass upper surface 2a, the effective incident light area 13 and the incident light areas 15a and 15b, which cause the ghost phenomenon, become close to each other, and the mask 5 is required to be attached with high accuracy. Conversely, as shown in FIG. 6, when the glass height h ₃ is lower than the glass h ₁ in FIG. 4, the incident light 16a, 16b causing the ghost phenomenon is
The light range changes in the direction away from the optical axis compared to a and 12b. As a result, the effective incident light area 13 and the incident light area 1 causing the ghost phenomenon are formed on the top surface 2a of the glass.
Since 6a and 16b are separated, there is no need for strict attachment accuracy of the mask 5, and accidents of blocking the effective incident light area 13 are reduced. The lower the glass height, the less mask attachment precision is required, and the incident light range that causes the ghost phenomenon moves away from the optical axis 17 direction, so the probability that light rays will be incident on this range decreases. Lower height is more advantageous.

In addition, if the glass height is low, depending on the conditions, mask 5
There are cases where this is not necessary, but cases where the glass height is low and do not require a mask will be discussed later.

Next, the relationship between the pasting position of the mask 5 and the ghost phenomenon will be explained.

FIG. 7 is a diagram showing a state in which the mask 51 is attached to the glass upper surface 2a of the linear image sensor. In this example, the central axis 18a of the slit width of the mask 51 and the optical axis 17 do not coincide with each other, and are pasted with a deviation of _e1 , so that the incident light range that causes the ghost phenomenon is not entirely blocked. Ideally, the mask 5 should be pasted with the central axis 18a of the slit width aligned with the optical axis 17, but in actual work, it is often pasted as shown in this example, although there are differences in degree. As shown in the figure, lights c and d at certain angles are incident on the linear image sensor within the incident light range that causes the ghost phenomenon. The light d is blocked by the mask 51, but the light c is not blocked by the mask 51 and reaches the reflective surface, and for the reason described above, enters the pixel 3, causing a ghost phenomenon.

In FIG. 8, the linear image sensor is tilted by θ ₁ with respect to the optical axis 17. The light c and the light d enter the linear image sensor under the same conditions as in FIG. 7, but at this time, neither the light c nor the light d reaches the light receiving area without being blocked by the mask 51. However, at this time, the light c does not reach the pixel surface 3 because it is outside the incident light area 12b that causes the ghost phenomenon, and therefore, the ghost phenomenon does not occur due to the light c. On the other hand, since the light d is a light ray that travels within the incident light area 12a that causes a ghost phenomenon, it causes a ghost phenomenon for the above-mentioned reason.

As described above, the linear image sensor is connected to the optical axis 17.
By changing the incident light that causes the ghost phenomenon,
It can be adjusted to generate ghosts in visually inconspicuous areas. This will be further explained in detail using figures.

FIG. 9 shows an image obtained by using the image processing apparatus shown in FIG. 3, with the linear image sensor 11 in the state shown in FIG. 7, inputting a transparent original with high contrast, and outputting the information. It is assumed that a ghost image f caused by light c is generated at the center of the output image. 10th
The figure shows an image obtained by setting the linear image sensor 11 to the state shown in FIG. 8 using the above-mentioned apparatus, inputting a transparent original, and outputting the information. A ghost image g caused by the light d is generated at the periphery of the output image. This is because the light d is a light ray that travels on the outside of the light c, and therefore the information of the transparent original that the light d has is on the outside, that is, the peripheral part, compared to the information that the light c has. By tilting the linear image sensor in this way, it is possible to change the incident light that causes the ghost phenomenon, and thereby the position of the ghost that occurs in the output image, making it possible to eliminate the ghost phenomenon that occurs near the center. move to the periphery,
It can be done inconspicuously.

Furthermore, as the angle θ ₁ between the optical axis 17 and the linear image sensor increases, the angle between the optical axis 17 and the incident light area 12a that causes the ghost phenomenon also increases, and the probability that light rays will be incident on the same area 12a decreases. , the ghost phenomenon will no longer occur.

FIG. 11 is a diagram showing a state in which a mask 52 is attached to the top surface 2a of the glass. The central axis 18b of the slit width of the mask 52 and the optical axis 17 do not match.
It is shifted by e ₂ and partially blocks light from the effective incident area 13.

FIG. 12 shows the linear image sensor of FIG. 11 tilted by θ ₂ so that the effective incident light area 13 is not blocked. In this way, by tilting the linear image sensor with respect to the optical axis, it is possible to correct the deviation in the attachment position of the mask 5.

As described above, since the mask 5 that blocks the light rays irradiated to the electrodes 4a and 4b is attached to the window glass 2, harmful reflections for the linear image sensor are eliminated, preventing the occurrence of ghost phenomena and improving the linear image. A sensor is obtained. Therefore, when the linear image sensor having the above structure is used in an image processing apparatus, the light source can be a fixed light source as shown in FIG.

In the above embodiment, the pixel row 3, which is a light receiving area, and the storage electrodes 4a, 4b, which are light reflecting areas, are connected by bonding wires.
b That is, it has a structure in which the light reception information once stored in the storage area is read out sequentially from the readout transfer section, but like the MOS type, the light reception area and the storage area are the same area, and the readout and transfer sections are arranged on both sides.
To prevent light from irradiating areas other than the light receiving area,
Exactly the same effect can be obtained even if the portion other than the light receiving area is shielded from light by a metal film such as aluminum.

In addition, since the light-reflecting areas are placed on both sides of the light-receiving area, a mask with slits is attached, but two strip-shaped masks may be attached with a width corresponding to the slits. It is clear that in the case where is placed only on one side, it is sufficient to paste one sheet.

Furthermore, instead of pasting a mask, the mask shape may be printed or vapor deposited directly on the glass surface.

Next, the point that a mask is not required if the glass height h satisfies a certain condition will be described in detail below.

In Figure 15, θ ₃₀ is the maximum angle of incidence, θ 20 is the distance from the light receiving part to the reflecting surface, θ ₂₀ is the critical incidence angle of the range of incident light that causes ghosting, and θ ₁₀ = π/2 - θ ₂₀ . be.

θ ₃₀ /2<θ ₂₀ =π/2−θ ₁₀ ... Here, since θ ₁₀ = tan ^-1 2h/, the formula is θ ₃₀ /2<π/2−tan ^-1 2h/ ... expressed.

Here, since tan ^-1 2h/=π/2−θ ₃₀ /2, the formula is 2h/<tan(π/2−θ ₃₀ /2) h</2tan(π/2−θ ₃₀ /2) ... However, 0° < θ ₃₀ /2 < θ _c (where θ _c is the air→glass critical angle of approximately 45°) In other words, if the glass height h satisfies the conditions of the above formula, a mask is not required. .

Of course, the incident light beam will be cut off if it hits the ceramic package 1 before θ ₃₀ /2 reaches the critical angle.

Therefore, if the effective aperture half width of the linear image sensor is m, then m<
+h/ _tanθ10 .

Here, since tanθ ₁₀ = 2h/, ∴m<+h×/2h=3/2... However, as the effective aperture half-width m becomes smaller, the ceramic package 1 comes into the effective luminous flux and becomes effective. It kills the luminous flux. To prevent this, m>h×tanθ ₃₀ /2... According to the formula, htanθ ₃₀ /2<m<3/2... In other words, if the dimensions of the ceramic package are designed to satisfy the formula, ghosts can be prevented. can be prevented.

〔Effect of the invention〕

As explained above, according to the present invention, a mask is provided on the transparent plate-like member that covers the light-receiving area and the light-reflecting area to block the light rays irradiated to the light-reflecting area, which is harmful to the linear image sensor. There will be no reflections. Therefore, even when used in an image processing apparatus that requires gradation expression, faithful image reproduction without the occurrence of ghosts is possible.

In addition, if it is not possible to completely block the light rays irradiating the light reflection area due to errors in the mounting position of the mask, etc., the substrate on which the pixels of the linear image sensor are arranged and the transparent plate-like member can be tilted with respect to the optical axis. By doing so, the location where the ghost occurs can be changed to a location where it is visually less noticeable.

In addition, if the effective light beam that should normally enter the pixel is blocked by the mask due to an error in the mounting position of the mask, it is possible to tilt the substrate and transparent plate-like member of the linear image sensor with respect to the optical axis. Therefore, blocking of the effective light beam can be avoided.

Furthermore, since ghosts do not occur even when exposed to light from various angles, it can be used in devices with fixed light sources, instead of the conventional complex structure of moving a slit light source with a slit covering the light source according to the scan of the sensor. Since this is not necessary, it is effective in simplifying the device.

[Brief explanation of the drawing]

Figure 1 is a front view showing an embodiment of the invention, Figure 2 is a front view showing an embodiment of the invention.
The figure is a sectional view of Fig. 1, Fig. 3 is a top view showing the arrangement of elements of an image processing device using a linear image sensor, and Figs. 4, 5, and 6 explain the principle of the invention. FIG. 7 is a first explanatory diagram showing the relationship between the mask attachment position and the ghost phenomenon. FIG. 8 is an explanatory diagram showing the linear image sensor shown in FIG. 7 in a tilted state. FIG. 9 is an explanatory diagram showing an output image of the information of the transparent original inputted to the image processing device shown in FIG. 3 and corresponds to FIG. 7, and FIG. 10 also shows an output image and corresponds to FIG. 8. FIG. 11 is a second explanatory diagram showing the relationship between the mask attachment position and the ghost phenomenon, FIG. 12 is an explanatory diagram showing the linear image sensor shown in FIG. 11 in a tilted state, and FIG. A cross-sectional view of a conventional image sensor, FIG. 14 is a front view of the conventional image sensor as seen from the light input information incident side, and FIG. 15 is an explanatory diagram showing the relationship between glass height and ghost phenomenon.
FIG. 16 is an explanatory diagram showing the relationship between the effective aperture half width and the ghost phenomenon. 1...Ceramic package, 2...Window glass, 2a...Top surface of window glass 2, 2b
...Bottom surface of window glass 2, 3...Pixel row, 4
a, 4b... Storage electrode, 5, 51, 52... Mask, 5a... Slit, 6... Illumination lamp, 7
. . . Projection lens group, 8 . . . Transparent original, 9 . . . Projection lens group, 10 .

Claims (1)

[Scope of Claims] 1. A light-receiving area formed by linearly arranging pixels for photoelectrically converting light rays incident through an optical system;
In a linear image sensor configured such that a surface of a substrate having a light reflecting area is covered with a transparent plate-like member, a mask is provided on the transparent plate-like member to block light rays irradiated to the light reflecting area, and the transparent plate-like member A linear image sensor characterized in that a substrate and a transparent plate-like member are configured to be tilt adjustable with respect to the optical axis of the optical system.