JPH07322010A - Color picture reader - Google Patents

Abstract

PURPOSE:To provide a color picture reader in which the same line can simultaneously be read, the spectroscopic characteristic of a main scanning direction is uniform and plural rays which are color-resolved are precisely focused at the same multiplying factor. CONSTITUTION:A first reflecting film 51 reflecting first color component light and a second reflecting film 54 reflecting specified color component light from light transmitting the first reflecting film 51 as second color component light are provided for the both surfaces of a transparent layer 52 having parallel planes. A color resolving means 5 that light-splits reflected light from the original 3, which is converged by an image-forming lens 4, into first and second color component light beams, that reflects them by the first and second reflecting films 51 and 54, and that forms image on the first and second one- dimensional-picture element strings 61 and 62 of a light-receiving element 6 is provided. The image-forming lens 4 is provided with the optical characteristic of a telecentric system, and the lengths of the optical paths of first and second color component light between the image-forming lens 4 and the light-receiving element 6 are set to be the first and second focal distances as against the first and second color component light of the image-forming lens 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image reading device, and more particularly to a reading device for reading a color image by separating it into three primary colors.

[0002]

2. Description of the Related Art Conventionally, there has been known a color original reading device in which a color image is color-separated into three primary colors and the color-separated light in each wavelength region is photoelectrically converted by a light receiving element to be read.

For example, in the apparatus shown in FIG. 6, an image forming lens 11 which uses white light including the entire desired wavelength range as a light source 1 and forms an image of reflected light from an original 3 placed on a platen glass 2. And B (blue light), G (green light), R on one chip
A color image is provided while scanning in the sub-scanning direction by including a light-receiving element 6 in which three one-dimensional pixel rows 61, 62, 63 set to have spectral sensitivity characteristics of three colors (red light) are arranged in the sub-scanning direction. Is to read.

Further, as shown in FIG. 7, white light including the entire desired wavelength range is used for the light source 1, and in the optical path between the image forming lens 11 and the light receiving element 6 for forming an image of the reflected light from the original 3, Dichroic films 81, 8 that reflect only the desired wavelength range
2. A color separation means composed of a beam splitter 8 in which a total reflection mirror 83 is laminated via a transparent layer 84 is arranged, and the reflected light is color separated by the beam splitter 8 to form a plurality of one-dimensional pixel rows 61, 62, 63. A device for making an imaging sensor integrally provided with ... receive light is also known from Japanese Patent Laid-Open No. 3-201861.

Further, as shown in FIG. 8, white light including the entire desired wavelength range is used for the light source 1, and in the optical path between the image forming lens 11 and the light receiving element 6 for forming an image of the reflected light from the original 3. As a color separation means for reflecting only a desired wavelength range, the beam splitter 9 in which dichroic films 91 and 92 and total reflection mirror 93 are laminated via a transparent layer 94, dichroic films 101 and 102, and total reflection mirror 103 are transparent. The beam splitter 10 laminated via the layer 104 is used to perform color separation into parallel rays, and the plurality of line sensors 61, 6
A configuration in which an image sensor including 2, 63 ... Is received integrally is also known from the disclosures of JP-A-1-237619 and JP-A-2-180465.

Further, as shown in FIG. 9, white light including the entire desired wavelength range is used as the light source 1, and in the optical path between the image forming lens 11 and the light receiving element 6 for forming an image of the reflected light from the original 3, A dichroic film 51 that reflects only a desired wavelength range,
54, a beam in which a total reflection mirror 55 is laminated via transparent layers 52 and 53 having a layer thickness adjusted according to the optical path length correction amount and the interval between the one-dimensional pixel rows 61, 62, 63, ... A color separation means composed of a splitter 8 is arranged at a predetermined installation angle θ, the reflected light is color separated by the beam splitter 8, and an image is integrally provided with a plurality of one-dimensional pixel rows 61, 62, 63 ... A device for allowing a sensor to receive light with accurate focus has also been proposed by the applicant of the present application and is disclosed in Japanese Patent Application No. 5-1118.
It has been filed as No. 18.

[0007]

However, the above-mentioned conventional color image reading apparatus has the following problems.

First, in the color image reading apparatus shown in FIG. 6, since the three line sensors 61, 62, 63 sequentially read, a delay memory is required to perform color processing of the color image in real time, and therefore the image is read. There is a problem that the processing becomes complicated and the cost becomes high. Further, it is difficult to obtain a clear image due to color shift due to mechanical scanning blur during sub scanning.

Further, in the color image reading apparatus shown in FIG. 7, since the light path length of the light flux of each color is different, it is necessary to use an imaging lens having a sufficiently deep depth of focus in order to obtain a clear image. There are difficulties. Further, if an attempt is made to adjust the optical path length by inclining the light receiving surface of the sensor, it is necessary to increase the angle, which causes a problem that the light receiving sensitivity is lowered.

Further, in the color image reading apparatus shown in FIG. 8, the light path lengths of the light fluxes of the respective colors are equal, but they have a complicated structure and their adjustment is difficult.

Further, in the color image reading apparatus shown in FIGS. 6, 7 and 8, it is desirable that the light beams of the three primary colors are accurately focused on the plurality of line sensors 61, 62, 63, ... Due to the influence of the chromatic aberration of the image lens 11, the rays of each color do not form an image on the same plane. As a countermeasure against this, it is conceivable to use a lens having a small chromatic aberration, but it is extremely difficult in terms of lens design and manufacturing to completely eliminate the chromatic aberration of the imaging lens 11 in a desired wavelength range.

Further, in the color image reading apparatus shown in FIG. 9, the light beams of the three primary colors are detected by a plurality of line sensors 61, 6.
It is possible to accurately focus on each of 2, 63, ... However, due to the characteristics of an ordinary imaging lens, since the optical path lengths of the light rays of the three primary colors are different, the imaging magnification for each color component is different. Differently, as a result, there is a problem that the image forming position shift in the main scanning direction occurs.

Furthermore, in the color image reading apparatus shown in FIGS. 7, 8 and 9, since the dichroic film utilizing the multilayer interference film is used as the color separation means, the color separation characteristics have angle-of-view dependency. However, it is difficult to obtain uniform spectral characteristics over the entire area in the main scanning direction.

The present invention has been made in view of the above problems, and an object of the present invention is to simultaneously read color image information on the same line, and
It is an object of the present invention to provide a color image reading device having uniform spectral characteristics in the entire area in the main scanning direction and capable of accurately focusing all of a plurality of color-separated light rays on a plurality of line sensors at the same magnification.

[0015]

A color image reading apparatus according to the present invention comprises a light source, an imaging lens for collecting reflected light from a document illuminated by the light source, and a first lens provided in parallel at a predetermined interval. A light-receiving element having one one-dimensional pixel array and a second one-dimensional pixel array; and a first reflective film that selectively reflects the first color component light on both planes of a transparent layer having parallel planes. And a second reflection film that reflects at least a part of the specific color component light as the second color component light from the light that has passed through the first reflection film, and the first reflection film and the second reflection film. The reflection film separates the reflected light from the document condensed by the imaging lens into the first color component light and the second color component light, and reflects the light.
Color separation means for forming an image on each of the first one-dimensional pixel row and the second one-dimensional pixel row of the light receiving element is provided, and the chief ray of the emitted light is parallel to the optical axis in the imaging lens. The optical characteristics of the telecentric system are set as described above, and the lengths of the respective optical paths of the first color component light and the second color component light between the imaging lens and the light receiving element are ,
A first color component of the imaging lens for the first color component light;
And a second focal length for the second color component light.

Further, in the color image reading apparatus of the present invention, the light source, the imaging lens for collecting the reflected light from the original illuminated by the light source, and the first lens provided in parallel on the plane at a predetermined interval. A light-receiving element having a one-dimensional pixel array and a second one-dimensional pixel array, and a first focal length for the first color component light of the imaging lens with respect to the optical axis of the imaging lens. And a second focal length with respect to the second color component light, which are arranged so as to form a predetermined angle based on a ratio between a distance between both focal points and a predetermined distance of the light receiving element, and which has a parallel plane. The first reflective film that selectively reflects the first color component light on both the planes and the at least a part of the specific color component light from the light that has passed through the first reflective film as the second color component light. A second reflective film that reflects light, and the thickness of the transparent layer is set to the predetermined angle. Color separation means set based on a predetermined distance of the light receiving element, and the imaging lens has telecentric system optical characteristics set such that the principal ray of the emitted light is parallel to the optical axis. The plane of the light-receiving element is arranged so as to vertically receive the reflected light from the document, which is reflected by the color separation means and is condensed by the imaging lens, and is condensed by the imaging lens. The reflected light from the original is separated into the first color component light and the second color component light, which are respectively coupled to the first one-dimensional pixel row and the second one-dimensional pixel row of the light receiving element. Characterized by the image.

[0017]

With the above arrangement, when reading a color image, the image information of the same line is simultaneously applied to each one-dimensional pixel row of the light receiving element, so that the image information of a single line with no positional deviation can be read. Further, the image information of this single line is separated by the optical means at an interval corresponding to the arrangement pitch of the line sensors arranged for each color component, and at the same time, each color ray has an optical path length different for each color component. After that, it is guided to the line sensor. At this time, the thickness of the transparent layer laminated between the dichroic films so as to offset the difference in the optical path length for each color component in the color separation means to offset the amount of focus position shift due to the longitudinal chromatic aberration of the imaging lens, the beam splitter,
By setting the installation angle of the line sensor, it is possible to accurately focus all of the plurality of color-separated light rays on the plurality of line sensors. In addition, since a telecentric system is used for the imaging lens, the spectral characteristics of color separation are uniform over the entire area in the main scanning direction, and the effect of lateral chromatic aberration, which is a problem when different optical path lengths are used for each color component, You can lose it.

[0018]

1 is an explanatory view of an optical system showing an embodiment of a color image reading apparatus of the present invention.

In the figure, reference numeral 1 is a white slit light source 1 in which the luminous flux includes almost the entire visible wavelength range, and 2 is a platen glass on which an original 3 is placed, and the white light beam emitted from the light source 1 is , Passes through the platen glass 2 and is reflected by the original 3, and the reflected light is condensed by an imaging lens 4 having a telecentric optical characteristic set so that the principal ray of the emitted light is parallel to the optical axis. It Reference numeral 5 denotes a multiple dichroic mirror as color separation means for separating the reflected light from the original 3 into information of three primary colors. The reflected light color-separated by the multiple dichroic mirror 5 enters a light receiving element 6 which is an image sensor. . The light receiving element 6 has three one-dimensional pixel rows, receives the reflected light reflected by the original 3, and outputs the image information of the original 3 as an electric signal.

Since the imaging lens 4 in this embodiment has a telecentric optical characteristic in which the principal ray of the emitted light is set parallel to the optical axis, the light ray emitted from the imaging lens 4 is It is guided to the multiple dichroic mirror 5 under the same angle condition in the range of the entire image length. Therefore, when the spectroscopic characteristics pass through the dichroic film having the reflection angle dependency, they are dispersed with the same spectroscopic characteristics in the range of the entire image length. There is no property and it becomes uniform. Further, since the principal ray from the imaging lens 4 to the light receiving element 6 is set to be parallel to the optical axis, the multiple dichroic mirror 5 forms an image on the light receiving element 6 with an optical path length different for each color component. Even in such a case, since the image magnification does not change, the image magnification of each color component becomes the same, and there is no positional deviation of the image formation in the main scanning direction.

In the multiple dichroic mirror 5 of this embodiment, a dichroic film 51 for reflecting a G (green) light component is coated on the outermost surface on the side where a light beam enters, and 2
The transparent surfaces 52 and 53 of the layers are coated with a dichroic film 54 that reflects a B (blue) light component, and R that has passed through the dichroic films 51 and 54, respectively.
A total reflection film 55 that reflects the (red) light component is formed on the back surface.

As described above, the color separation means in this embodiment is formed by laminating the two dichroic films 51 and 54 and the one total reflection film 55 via the two transparent layers 52 and 53. The multiple dichroic mirror 5.

Further, the light receiving element 6 is, as shown in FIG.
Predetermined pitches P1 and P2 on one chip, for example, 80
Three one-dimensional pixel rows 6 arranged in parallel at intervals of μm 6
In the image sensor having 1, 62 and 63, each of the B light, G light and R light of the three primary color lights color-separated by the multiple dichroic mirror 5 is a one-dimensional pixel array 61, 6 respectively.
It is arranged so that the light is condensed to 2, 63.

The chromatic aberration characteristics of a normal imaging lens designed so that the chromatic aberration as a whole becomes smaller tend to have a longer focal length in the order of green (G), blue (B), and red (R). Therefore, each one-dimensional pixel array 61, 62, 63 is
The green light reading light receiving element, the blue light reading light receiving element, and the red light reading light receiving element are arranged in this order. In addition,
A filter for removing unnecessary component light may be attached to the light receiving element of each color. Further, the intervals of the array of one-dimensional pixel columns do not necessarily have to be the same.

Here, the thickness of each layer of the multiple dichroic mirror 5 and the inclination angle θ of the imaging lens 4 with respect to the optical axis 7.
Is determined by the amount of longitudinal chromatic aberration of the imaging lens 4 and the pitches P1, P2 between the three one-dimensional pixel rows 61, 62, 63 on the light receiving element 6, and the additional amount of the optical path length of the light flux of each color component is The amount of longitudinal chromatic aberration of the imaging lens 4 is adjusted by the multiple dichroic mirror 5 which is a color separation means.

The amount of change in the optical path length of each color ray depending on the inclination angle θ of the multiple dichroic mirror 5 with respect to the optical axis 7 of the imaging lens 4, that is, the amount of shift of the image forming position due to the change in optical path length, and the interval of reflected light, ie, beam separation. Figure 3 shows the width relationship
Shown in. The horizontal axis represents the incident angle θ (see FIG. 1), and the vertical axis represents the relative value.

In FIG. 3, the multiple dichroic mirror 5 is shown.
Both of the transparent layers 52 and 53 have a refractive index of N = 1.52, a broken line A indicates a change in the shift amount of the image forming position due to a change in the optical path length, and a solid line B indicates a change in the beam separation width.

From the relationship shown in FIG. 3, the transparent layers 52 and 53 of the optimum multiple dichroic mirror 5 are optimized based on the characteristics of the imaging lens 4 and the shape and size of the light receiving element 6 that are actually used.
The thickness and the inclination angle θ to be installed were designed.

As shown in FIG. 4, the amount of deviation of the image forming position for each color component due to the longitudinal chromatic aberration of the image forming lens 4 used in this embodiment is as follows with respect to the image forming position 41 of G (green) component light. The image forming position 42 of the B (blue) component light is about 50 μm, and the image forming position 43 of the R (red) component light is about 100 μm farther from the image forming lens 4. That is, FIG. 4 shows that the position 41 is the image forming position of the G component light because the MTF (modulation transfer function) value of the imaging lens 4 is the largest at the position 41 for the G component light. It is shown that the positions 42 and 43 where the MTF value is maximum for the B component light and the R component light are the respective imaging positions.

Therefore, in the present embodiment, in order to image each color component light at the same position, the optical path length of the B component light is made longer than the optical path length of the G component light, and the optical path length of the B component light is further increased. On the other hand, the optical path length of the R component light is increased. In order to add the optical path length in this way, the multiple dichroic mirror 5
The first transparent layer 52 and the second transparent layer 53 of both are 0.11
The thickness was set to mm.

The procedure for determining the thickness of the first transparent layer 52 and the second transparent layer 53 will be described below with reference to FIG.

Transparent layer 5 of multiple dichroic mirror 5
FIG. 5 shows the relationship among the thicknesses of ₂ , 53 (refractive index n ₁ , n ₂ , film thickness t ₁ , t ₂ ), reflection angles θ ₁ , θ ₂ , beam separation width d ₁ , and optical path length difference ΔL. As shown.

Now, let us consider the G component light reflected on the uppermost surface of the multiple dichroic mirror 5 and the B component light reflected on the intermediate surface.

Of the white light incident on the point O at the angle θ ₁ on the surface of the multiple dichroic mirror, the G component light is reflected at an angle θ ₁ ′ symmetrical to the normal to the surface, while the light other than the G component light is refracted at the refraction angle θ. _It refracts at ₂ and goes to the next surface. At this time, the relationship between the angles θ ₁ and θ ₂ is expressed by the refraction formula n ₁ sin θ ₁ = n ₂
It is determined by sin θ ₂ .

Of the light refracted at the point O, the B component light is reflected at the point P at an angle θ ₂ ′ (= −θ ₂ ), and from the point Q to the refraction angle θ ₁ ′ (= −θ ₁ ). And then travels in parallel with the G component light reflected by the first surface at an interval d ₁ .

Here, d ₁ is represented by OQ · cos θ ₁ . However, OQ is the distance between the point O and the point Q. The same applies to OP, PQ, and OR described later. OQ is 2t
_{Since 1} · tan θ ₂ , d ₁ = 2 · t ₁ · tan θ
₂ × cos θ ₁ .

The effective optical path length difference between the optical path length of the G component light from the point O to the point R and the optical path length of the B component light from the point O to the point P to the point Q, that is, The optical path length difference ΔL converted into a vacuum is represented by the following equation.

ΔL = {(OP + PQ) / n ₂ }-(OR / n ₁ ) = {(2 · t ₁ ) / (n ₂ · cos θ ₂ )}-{(2 ·
t ₁ tan θ ₂ × sin θ ₁ ) / n ₁ } Therefore, when n ₁ = 1 and n ₂ = 1.525,
When θ ₁ = 58.0 degrees and t ₁ = 113 μm, d ₁ =
It can be set to 80 μm and ΔL = 50 μm.

As shown in FIG. 3, when the beam separation width: the optical path length shift amount is 80 μm: 50 μm (1.6: 1), the ray incident angle θ = 58.0 degrees, which is transparent at this time. The layer thickness is 0.11 mm. In addition, the first transparent layer 52 and the second transparent layer 53 of the multiple dichroic mirror 5
Both have a refractive index N of N = 1.52 in the visible wavelength region.
The tilt angle θ of the multiple dichroic mirror 5 with respect to the optical axis 7 of the imaging lens 4 is set to 58 degrees for the above reason.

With the above setting, the image forming position deviation of each component light G, B, R due to the aberration is offset by making the optical path length of each component light G, B, R different, and the color separation is performed. The respective component lights G, B, and R of the three primary colors are imaged on the respective one-dimensional pixel rows without defocusing.

Further, the tilt angle θ of the multiple dichroic mirror 5 with respect to the optical axis 7 of the imaging lens 4 can be easily set.
Even if the first transparent layer 52 and the second transparent layer 53 are both set to a thickness of 0.115 mm, the B (blue) component light and the R (red) component light with respect to the G (green) component light are set to 0 degrees. The optical path length differences are about 46 μm and about 92 μm, respectively, which are values close to the respective shift amounts, 50 μm and 100 μm, and the effect of adjusting the imaging position can be expected sufficiently from FIG.

In the color image reading apparatus according to the present invention, the two dichroic films 5 as the color separation means are used.
The tilt angle θ formed by the planes of the total reflection films 55 and the optical axis 7 of the imaging lens 4 is determined by the row pitch of the light receiving elements and the optical path length adjustment width as described above.
If it is less than 70 degrees, the position of the light receiving element interferes with the light beam from the imaging lens, and if it exceeds 70 degrees, the spectral reflection characteristics deteriorate due to the characteristics of the dichroic film. It is set to the range of.

The thickness of the two transparent layers 52 and 53 with the dichroic films 51 and 54 and the total reflection film 55 interposed therebetween is
The range is not limited to the above range, and is usually set in the range of 50 to 300 μm.

The image forming lens 4 is configured so that the image forming position of the blue light due to its longitudinal chromatic aberration is located approximately at the midpoint between the image forming position of the green light and the image forming position of the red light, whereby the multiple dichroic mirror is formed. The two transparent layers can have the same thickness, and the rows of the light receiving elements having the same pitch can be used.

In the color image reading apparatus of this embodiment, the optical path length difference of the color-separated G, B, and R component light is adjusted according to the chromatic aberration of the imaging lens 4, but the color separation system is reversed. G (green) component light, B (blue) component light, and R (red)
It is also possible to design the chromatic aberration of the imaging lens 4 according to the difference in the optical path length of the component light, and this method further increases the degree of freedom in design.

For example, by using an imaging lens whose optical path lengths are short in the order of B, G, and R component lights, the B component light can be reflected on the surface of the multiple dichroic mirror. Therefore, the absorption of the B component light can be reduced, and a light source with a small B component light can be effectively used.

[0047]

According to the color image reading apparatus of the present invention,
Even when an imaging lens with chromatic aberration is used, the optical path length of the color-separated light flux of each color can be canceled by the color separation means in accordance with the longitudinal chromatic aberration amount of the imaging lens, and all of the plurality of light rays can be canceled out. There is no error in magnification on each of the plurality of one-dimensional pixel rows on the light receiving element, and accurate focusing can be achieved.
Further, uniform spectral characteristics can be obtained in the entire area in the main scanning direction, the reading performance of the color image reading apparatus can be improved, and reading with less color misregistration can be performed.
Further, the design and manufacture of the imaging lens can be facilitated, and the cost of the entire device can be reduced.

[Brief description of drawings]

1A is a plan view of a color image reading apparatus showing an embodiment of the present invention, and FIG. 1B is a side view of the same.

FIG. 2 is a plan view of a light receiving element in this embodiment.

FIG. 3 is a correlation diagram showing the relationship between the tilt angle θ of the multiple dichroic mirror, the shift amount of the optical path length, and the beam separation width in the present embodiment.

FIG. 4 is a correlation diagram showing a relationship between an image formation position of GBR component light of three primary colors and an MTF value in the present embodiment.

FIG. 5 is a diagram illustrating an optical path length in a multiple dichroic mirror.

FIG. 6 is a configuration diagram of a conventional color image reading device.

FIG. 7 is another configuration diagram of a conventional color image reading device.

FIG. 8 is still another configuration diagram of a conventional color image reading device.

FIG. 9 is still another configuration diagram of the conventional color image reading device.

[Explanation of symbols]

1 ... Light source, 2 ... Platen glass, 3 ... Original, 4 ... Imaging lens, 5 ... Multiple dichroic mirror, 6 ... Light receiving element,
7 ... Optical axis, 41, 42, 43 ... Imaging position, 51, 54 ...
Dichroic film, 52, 53 ... Transparent layer, 55 ... Total reflection film, 61, 62, 63 ... One-dimensional pixel array

Claims (2)

[Claims] 1. A light source, an imaging lens for collecting reflected light from a document illuminated by the light source, a first one-dimensional pixel array and a second one-dimensional pixel arranged in parallel at a predetermined interval. At least one of a light receiving element having columns and a first reflecting film that selectively reflects the first color component light on both planes of the transparent layer having parallel planes, and at least one of the light transmitted through the first reflecting film. And a second reflection film for reflecting the specific color component light of the part as a second color component light, respectively, and the light is condensed by the imaging lens by the first reflection film and the second reflection film. The reflected light from the document is split into the first color component light and the second color component light and reflected, and is reflected by the first one-dimensional pixel row and the second one-dimensional pixel row of the light receiving element, respectively. A color separation unit for forming an image, and the image forming lens is configured such that the principal ray of the emitted light is parallel to the optical axis. Are those having the optical properties of centric system, the first between the said imaging lens and said light receiving element
The lengths of the respective optical paths of the color component light and the second color component light are respectively defined by a first focal length of the imaging lens for the first color component light and a second focal length for the second color component light. A color image reading device having a focal length. 2. A light source, an imaging lens for condensing reflected light from a document illuminated by the light source, a first one-dimensional pixel array and a second one-dimensional pixel array arranged in parallel on a plane at a predetermined interval. A light-receiving element having a one-dimensional pixel array; a first focal length for the first color component light and a second focal length for the second color component light, which the imaging lens has, with respect to the optical axis of the imaging lens; The first color is arranged on both planes of the transparent layer, which are arranged so as to form a predetermined angle based on the ratio between the distance between the two focal points and the predetermined distance between the light receiving elements, and which has parallel planes. A first reflection film that selectively reflects the component light and a second reflection film that reflects at least a part of the specific color component light as the second color component light from the light that has passed through the first reflection film.
And a color separation unit in which the thickness of the transparent layer is set based on the predetermined angle and the predetermined interval of the light receiving element, and the imaging lens is a The optical characteristic of the telecentric system is set so that the light beam is parallel to the optical axis, and the plane of the light receiving element is formed from the original document condensed by the imaging lens reflected by the color separation means. Are arranged so as to vertically receive the reflected light, and the reflected light from the document condensed by the imaging lens is combined with the first color component light and the second reflected light.
The color image reading device is characterized in that the light is separated into the color component light of and is imaged on the first one-dimensional pixel row and the second one-dimensional pixel row of the light receiving element.