JP3940487B2 - Contact image sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image sensor for reading an image of a document, particularly a contact image sensor, as an input device for a computer, a facsimile machine, a copying machine or the like.
[0002]
[Prior art]
Image sensors are excellent in operability and versatility as image input devices, and have been widely used in recent years in fields such as OA equipment and information equipment. In particular, in recent years, demand for household facsimile machines has increased, and a compact and easy-to-use image sensor has been demanded. Therefore, a contact type using a light emitting diode (hereinafter referred to as “LED”) array or the like as a light source. Image sensors are becoming popular. FIG. 15 is a sectional view of a conventional contact image sensor described in, for example, Japanese Patent Laid-Open No. 6-342131, and its outline will be described.
[0003]
As shown in FIG. 15, the contact-type image sensor has a light receiving element array 124 including a document reading light receiving element 121 in which a plurality of sensor pixels for photoelectric conversion are arranged, a protective film 122, and a substrate 123 on which the protective film 122 is mounted. An LED array 125 that is a linear light source that irradiates the document, a lens array 126 that forms an image of the document 129 on the light receiving element array 124 that is a light receiving unit, a transparent plate 127 on which the document 129 is placed, and the like It is comprised from the exterior case 128 which supports these members.
[0004]
In the operation of the contact type image sensor, the document surface is irradiated by the LED array 125, diffuse reflected light on the reading line of the document surface is imaged on the light receiving element array by the lens array 126, and the document which the reflected light has The light / dark information of 129, that is, the intensity of light, is converted into an electric signal by the sensor pixel of each original reading light receiving element 121 in the light receiving element array 124, and sent out for each reading line as a serial or parallel signal output. Then, the two-dimensional image information is converted into a time-series electric signal by moving the relative position between the document 129 and the sensor pixel row in the direction perpendicular to the line and repeating the data transmission for each line.
[0005]
However, the above contact image sensor has the following problems. The lens array 126 is a compound eye lens composed of a plurality of rod lenses each having a condensing property arranged in a direction perpendicular to the drawing. Therefore, an image overlap occurs on the light receiving side, and a synthetic aperture angle increases. Therefore, there is a problem that the image quality deteriorates when the depth of field is shallow, the document is folded, or the document has irregularities such as cut and paste. Further, the spread part of the book cannot be read, and the application of the image sensor is limited.
[0006]
The state of image formation in the lens array 126 using the rod lens will be described with reference to FIG. In the lens array 126 shown in FIG. 15, rod lenses 126a are aligned in the line direction, and each rod lens 126a is made of a translucent material having a refractive index distribution in a direction perpendicular to the optical axis. As shown in FIG. 16A, each rod lens 126a forms an erecting equal-magnification image on the sensor surface on which the sensor pixels are arranged in the range of the diameter X0 on the document surface. Consider a light emitting point p and its imaging q. When p is at the reference position, it is assumed that there is a light condensing point on the sensor surface, and the image formation q is not blurred. As shown in FIG. 16B, when the light emitting point p moves by x to p ′, the condensing point also moves by x behind the sensor surface, and the imaging q on the sensor surface causes a blur of the amount of H. . When the rod lens 126a is used alone, the blur amount H is approximately H = Θx and depends on the aperture angle Θ. When a plurality of rod lenses 126a are arranged as shown in FIG. 17C, the opening angle is Θ ′ larger than Θ, the amount of blur is H ′ larger than H, and substantially H ′ = Θ′x. It becomes. As the number of arrangements of the rod lenses 126a increases, the aperture angle increases due to the overlap of the imaging range X0, and the blur increases. As described above, there is a problem that the aperture angle is wide, the relative depth of field is shallow, and the ratio of the amount of blurring of the imaging q to the movement of the light emitting point p is large.
[0007]
If an attempt is made to reduce the aperture angle Θ of each individual rod lens in order to eliminate such drawbacks, the optical path length from p to q becomes long, and when used in a contact image sensor, the apparatus becomes large. Further, such a rod lens itself is expensive. JP-A-6-342131 discloses a contact image sensor shown in FIG. 17 which has been improved for the purpose of improving these drawbacks. In FIG. 17, reference numeral 110 denotes an aperture limiting member, which is disposed on the exit side corresponding to each rod lens 126a. The other points are the same as those of the image sensor shown in FIG. In this example, the aperture limiting member 110 limits the aperture angle of each rod lens 126a, limits the overlap of images between the rod lenses, and reduces the amount of blur.
[0008]
However, in this case, the positional relationship of the aperture limiting member 110 must be accurately matched to the individual rod lenses 126a, which is disadvantageous in terms of assembly. In addition, the light passing amount is limited by the aperture limiting member 110, the intensity of the incident light to the light receiving element array 126 is weakened, and the S / N ratio in the photoelectric conversion tends to decrease and the noise of the generated signal tends to increase. .
[0009]
The present invention has the above-mentioned problems in the conventional contact image sensor, that is, in general, the problem that the aperture angle is wide and the depth of field is shallow, and using a rod lens having a large depth of field in order to improve this, The problem of increasing the size of the apparatus and the like, and the provision of an aperture limiting member for the rod lens are disadvantageous in assembly, and the problem of increasing the noise of the signal of the light receiving element is a problem to be solved. The present invention solves these problems, and provides a contact image sensor that can deal with various types of originals such as bent, uneven, double-page spread, can accurately read an image of an original, and can be easily assembled. Objective.
[0010]
[Means for Solving the Problems]
  As a first means for solving the above-described problems, the present invention includes a transparent plate for placing a document, illumination means for irradiating the document surface in a line shape, and a collection for imaging reflected light from the irradiated document surface. In a contact type image sensor having a plurality of light receiving elements arranged in a line shape that receives and photoelectrically converts the imaged light, and detects image data of a document surface by light input to the light receiving element, The condensing means includes a plurality of lenses arranged in the line direction and a transparent parallel plate having a plurality of parallel planes with different thicknesses from a base surface provided to face the plurality of lenses.The transparent parallel plate is a transparent plate on which the document is placed.It is characterized by that.
[0011]
  As a second means for solving the above problems, the present invention provides:The plurality of lenses arranged in the line direction are a plurality of rod lenses arranged in the line direction, and the transparent plate on which the document is placed is a first plate comprising a surface parallel to the document placement surface. 1 Step and the second 2 A step is provided and 1 Step thickness d1 and the thickness 2 There is a relationship of d11> d12 between the thicknesses d2 of the stepped portions. 1 The boundary between the stepped portion and the second stepped portion is parallel to the arrangement direction of the rod lenses, and the transparent plate is positioned so as to be at a position substantially opposite to the diameter of each rod lens.It is characterized by being.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example which is one of the preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a contact image sensor according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG. As shown in FIG. 1, the contact image sensor of this example is a light receiving element comprising a document reading light receiving element 21 in which a plurality of sensor pixels for photoelectric conversion are arranged, a protective film 22, and a substrate 23 on which the protective film 22 is mounted. An array 24; an LED array 25 that is a linear light source that irradiates the original; a lens array 26 that forms an image of the original 29 on the light receiving element array 24 that is a light receiving portion; a transparent parallel plate 31 with a step; The frame includes a support frame 37 that holds the array 26 and the transparent parallel plate 31, a transparent plate 27 on which the document 29 is placed, and an outer case 28 that supports these members. In this example, the transparent parallel plate 31 is disposed between the lens array 26 and the light receiving element array 24.
[0016]
In the operation of the contact type image sensor, the document surface is irradiated by the LED array 25, and the diffuse reflection light on the reading line of the document surface is imaged on the light receiving element array 24 by the lens array 26 and the transparent parallel plate 31. The light and shade information of the document 29 having reflected light, that is, the intensity of light, is converted into an electric signal by the sensor pixels of the individual document reading light receiving elements 21 in the light receiving element array 24 and sent out as a serial or parallel signal output for each reading line. Then, the relative position between the document 29 and the sensor pixel array is moved in the direction perpendicular to the line, and data transmission for each line is repeated, thereby converting the two-dimensional image information into a time-series electric signal.
[0017]
As shown in FIGS. 1 and 2, the lens array 26 is composed of a plurality of rod lenses 36 arranged in a direction parallel to the reading line of the original surface, and is held by a holding frame 37. The transparent parallel plate 31 is held by a holding frame 37 so as to face the end surface of the rod lens 36 opposite to the transparent plate 27. The transparent parallel plate 31 is made of a translucent member having a refractive index n1, and a first surface 31b having a thickness from the base surface 31a to d1 and a second surface 31c having a thickness from the base surface 31a to d2 are transparent and parallel. The plates 31 are alternately provided in the longitudinal direction (arrangement direction of the rod lenses 36). The lengths of these surfaces in the longitudinal direction are both substantially equal to the diameter D of the rod lens 36, and the boundary between the surfaces is substantially in the longitudinal direction. Orthogonal. Here, there is a relationship of d1> d2 between the thickness d1 of the first surface 31b and the thickness d2 of the second surface 31c. As shown in FIG. 2, the transparent parallel plate 31 is positioned so that the boundary between the first surface 31 c and the second surface is at a position substantially opposite to the diameter orthogonal to the arrangement direction of the rod lenses 36.
[0018]
The rod lens 36 is made of a translucent material having a refractive index distribution in a direction orthogonal to the optical axis, like the conventional rod lens 126a shown in FIG. 16, and has the same function itself.
[0019]
FIG. 3 is a principle view showing a general action in condensing a parallel plate made of a translucent material. Light from a lens or the like (not shown) is incident on one surface La of the parallel plate L having a refractive index n1 and a thickness d in a direction in which the light is collected at the point B0. At this time, assuming that the incident angle with respect to the normal of the surface is θ and the refraction angle is θ1, the light ray incident at θ at the point O1 in the figure with respect to the normal becomes the angle of θ1 due to refraction inside the parallel plate L. To the point O2 ′ of the surface Lb on the exit side. From the point O2 ', the light exits at an angle of θ again with respect to the normal of the surface Lb by refraction. The emitted light beam intersects the optical axis at a point B1 that is behind the point B0 by X. Here, the relationship between θ and θ1 is sin θ = n1 · sin θ1, and when θ is small, it is considered that θ1 = (1 / n1) θ (1).
[0020]
Let O2 be the point where the straight line connecting O1 and B0 intersects the exit-side surface Lb of the parallel plate L, and let O1 'be the point where the normal at the incident point O1 of the surface La intersects the surface Lb. Assuming that the distance between O1 ′ and O2 is y, the distance between O1 ′ and O2 ′ is y1, and the distance between O1 ′ and O2 ′ is y ′, according to FIG. 3, y ′ = y−y1 = d · tan θ−d · tan θ1 (2), y ′ = X · tan θ (3). When θ is small, it is considered that tan θ = θ and tan θ1 = θ1. Therefore, from the equations (2) and (3), X = y ′ / θ = (d · (θ−θ1)) / θ. From equation (1), X = y ′ / θ = (d · (θ−θ1)) / θ = d · (1− (1 / n1)) (4). From equation (4), X is determined by the thickness d and the refractive index n1 of the parallel plate without depending on the incident angle θ. Accordingly, all of the light incident on the flat plate L is collected at approximately the point B1.
[0021]
Conversely, if there is a light spot at the point B1, the light incident on the parallel plate L from the point B1 reverses the optical path shown in FIG. 4, and from the surface La in a direction like a light beam emitted from the point B0. Exit. As described above, the light condensing point can be shifted rearward by arranging the original condensing point or a translucent parallel plate perpendicular to the optical axis before the original condensing point.
[0022]
FIG. 4 is a principle diagram showing the action of the light collecting means comprising the rod lens 36 and the transparent parallel plate 31 in this example, and (a) is a sectional view parallel to the line direction (arrangement direction of the rod lenses) showing the whole. (B) is a detailed view of part B in (a), and (c) is a CC arrow view of (b). In FIG. 4A, the light emitted from the light emitting point A0 at the reference position is incident on the rod lens 36, and the virtual condensing point B00 is formed from the end surface opposite to the incident to form an equal magnification erect image. The light is emitted toward the transparent parallel plate 31. Of this incident light, the light incident on the first surface 31b takes an optical path as exemplified by s1 and s1 ′ based on the principle already described, and is condensed at the first condensing point B11 that is X1 behind B00. To do. The light incident on the second surface 31c takes an optical path as exemplified by s2 and s2 'according to the principle already described, and is condensed at the second condensing point B12 that is X2 behind B00. Here, from equation (4), X1 = d1 · (1− (1 / n1)), X2 = d2 · (1− (1 / n1)), and since d1> d2, X1> X2. If the distance between B11 and B12 is dc, dc = (d1−d2) · (1− (1 / n1)).
[0023]
Thus, the light emitted from the one light emitting point A0 at the reference position is condensed by the condensing means on the two condensing points B11 and B12 which are separated by dc on the optical axis. S is a sensor surface on which the original reading light receiving element 21 in the light receiving element array 24 is arranged. Here, the condensing point B11 is configured to be on the sensor surface S. The opening angle at which the rod lens 36 is viewed from the light emitting point A0 (or the opening angle at which the rod lens 36 is viewed from B0) is Θ, and imaging on the sensor surface S by the passing light of the first surface 31b is q1, and the second surface 31c. If q2 is an image formed on the sensor surface S by the passing light of q, q1 and q2 are generated at overlapping positions, but the blur H1 of q1 is H1 = 0, and the blur H2 of q2 is approximately H2 = Θdc. Strictly speaking, with respect to q2, image formation occurs only in the right half surrounded by the solid line, but the distance between the optical axis and the outer edge of the image formation becomes a problem with respect to the amount of blur. The left half surrounded by the dotted line is included in the image formation and is regarded as effective image formation (hereinafter, the same applies).
[0024]
Next, FIG. 5 is a diagram showing the relationship between the movement of the light emitting point and the blur, (a) is a cross-sectional view showing the whole, (b) is an enlarged view of a portion D in (a), (c) is a diagram of (b). It is an EE arrow line view. As shown in FIG. 5 (a), when the light emitting point A0 moves to the point A0 ′ ahead by x from the reference position, the virtual condensing point B00 moves to the point B00 ′ behind this by x, and accordingly, The first condensing point B11 moves backward by x and from B00 'to the point B11' behind X1, and the second condensing point B12 also moves backward from the original position by x and from B00 '. Moves backward B12 'by X2. At this time, the blur amount H1 of the image formation q1 due to the light passing through the first surface 31b is approximately H1 = Θ | x |, and the blur amount H2 of the image formation q2 due to the light passing through the second surface 31c is approximately H2 = Θ | dc−x |.
[0025]
FIG. 6 shows the amount of movement x of the light emitting point A0 from the reference position, the amount of blur H1 of the imaging q1 due to the light passing through the first surface 31b, and the amount of blur H2 of the imaging q2 due to the passing light through the second surface 31c. It is a figure which shows a relationship. Here, if the amount of blur for any one of the images is equal to or less than a predetermined value, the document reading light receiving element 21 arranged on the light receiving surface can be operated normally.
[0026]
Therefore, the smaller one of H1 and H2 shown in FIG. 6 is taken as an effective blur amount HE, which is compared with the blur amount H of the conventional rod lens shown in FIG. A graph is shown in FIG. In the figure, a solid line indicates HE and a broken line indicates H. In the case of the condensing means comprising the rod lens 36 and the transparent parallel plate 31 of this embodiment shown in FIG. 2, the effective amount of blurring with respect to the movement of the light emitting point can be kept small over a wider range than before. For example, when x is (3/2) dc, the amount of blur can be reduced to 1/3 of the conventional one. The blur can be reduced by substantially increasing the depth of focus without reducing the aperture angle Θ. This effect is the same in a lens array in which a plurality of rod lenses 36 are aligned, and the depth of focus is substantially reduced without reducing the synthetic aperture angle corresponding to Θ ′ in FIG. Deepen to reduce blur. Therefore, in this example, there is no need to provide a member for limiting the opening, or to reduce the diameter of the rod or increase the distance between the light emitting point and the light receiving point in order to reduce the opening angle.
[0027]
In this way, by providing the transparent parallel plate 31 so as to face the rod lens 36, a bifocal lens that condenses light from one light emitting point at two different positions is configured and moved forward from the reference point. Therefore, the effective blurring of image formation can be effectively reduced. In addition, there is no limiting member as described above, and a wide opening angle can be obtained, so that the apparatus can be downsized and the light quantity on the light receiving surface can be sufficiently obtained. Thereby, in the contact image sensor according to the present embodiment shown in FIG. 1, a gap is formed between the transparent plate 27 and the document 29 due to bending or spread of the document 29, and the light emission point of the reflected light on the document surface is When the position is shifted forward from the position of the surface of the transparent plate 27, the amount of blur generated in image formation on the original reading light receiving element 21 arranged on the light receiving surface due to the shift can be significantly reduced as compared with the conventional case. In addition, in a small apparatus, the data on the original surface can be read with high accuracy by securing the amount of light on the light receiving surface.
[0028]
Hereinafter, an example which is another preferred embodiment of the present invention will be described with reference to the drawings. 8A and 8B are diagrams showing the configuration of the contact image sensor according to the present embodiment, where FIG. 8A is a cross-sectional view and FIG. 8B is a top view. In (b), the display of the document 29 is omitted. As shown in FIG. 8, the contact type image sensor of this example is a light receiving element comprising a document reading light receiving element 21 in which a plurality of sensor pixels for photoelectric conversion are arranged, a protective film 22, and a substrate 23 on which the protective film 22 is mounted. An array 24, an LED array 25 that is a linear light source that irradiates the document, a lens array 26 that forms an image of the document 29 on the light receiving element array 24 that is a light receiving unit, and a support frame 37 that holds the lens array 26. And a transparent plate 27 on which the document 29 is placed, and an outer case 28 that supports these members.
[0029]
Here, the transparent plate 27 is made of a translucent material having a refractive index n1, and is provided with a first step portion 27b and a second step portion 27c which are surfaces parallel to the document placement surface 27a. There is a relationship of d11> d12 between the thickness (distance from the document placement surface 27a) d11 of the first step portion 27b and the thickness (distance from the document placement surface 27a) d12 of the second step portion 27c. is there. In this example, the transparent parallel plate 31 such as the contact image sensor shown in FIG. 1 is not disposed between the lens array 26 and the light receiving element array 24. Instead, the transparent plate 27 has a stepped portion. Is provided.
[0030]
The lens array 26 is composed of a plurality of rod lenses 36 arranged in a direction parallel to the reading line on the document surface similar to the embodiment shown in FIG. 1 and is held by a holding frame 37. As shown in FIG. 8B, the transparent plate is such that the boundary between the first step portion 27b and the second step portion 27c is parallel to the arrangement direction of the rod lenses 36 and is substantially opposite to the diameter of each rod lens 36. 27 is positioned. The rod lens 36, the light receiving element array 24, and the LED array 25 are the same as those in the embodiment shown in FIG.
[0031]
FIG. 9 is a sectional view showing the operation of the main part of this embodiment. First, consider a case where the light emitting point A0 is on the document placement surface 27a. At this time, the optical path of the light incident on the transparent plate 27 from the light emitting point A0 is the same as that in the case where the light emitted from B1 in FIG. That is, the light emitting point A0 corresponds to B1 in FIG. 3, and the document placement surface 27a corresponds to one surface Lb of the parallel plate L in FIG. 3, but corresponds to the case where B1 is on Lb.
[0032]
Therefore, based on the reverse light principle, the light that has passed through the first step portion 27b from the light emitting point A0 to the transparent plate 27 takes the same optical path s11 as the light emitted from A01 behind the A0 by X1. The light emitted from the transparent plate 27 and passed through the second step portion 27b is emitted from the transparent plate 27 as if it took the same optical path s12 as the light emitted from A02 behind X2 by A2. Here, from equation (4), X1 = d11 · (1− (1 / n1)), X2 = d12 · (1− (1 / n1)), and since d11> d12, X1> X2. When the distance between A01 and A02 is dc1, dc1 = (d11−d12) · (1− (1 / n1)).
[0033]
The light incident on the rod lens 36 through the optical path s11 is condensed as the outgoing light of the optical path s21 at the first condensing point B01 which is at the same magnification as A01 and enters the rod lens 36 through the optical path s12. The collected light is condensed as the outgoing light of the optical path s22 at the second condensing point B02 which is at the same magnification as A02. Here, B02 is located behind dc1 by dc1. In this way, a condensing means for generating two condensing points separated from each other on the optical axis with respect to one light emitting point is constituted. Now, if the light emitting point A0 moves to A0 'ahead by x due to the float of the surface of the document 29, A01 and A02 will move forward by x, although illustration is omitted, B01 and B02 Each moves to B01 'and B02' behind by x. Therefore, also in this example, blurring of image formation on the sensor surface in the original reading light receiving element 21 can be reduced and the same effect can be obtained by the same principle as in the case of the contact image sensor shown in FIG.
[0034]
Hereinafter, an example which is another preferred embodiment of the present invention will be described with reference to the drawings. 10A and 10B are diagrams showing a configuration of a contact image sensor for color image reading according to the present example. FIG. 10A is a cross-sectional view thereof, and FIG. 10B is a cross-sectional view taken along a line DD in FIG. The contact type image sensor of this example irradiates a document with a light receiving element array 24 including a document reading light receiving element 21 in which a plurality of sensor pixels that perform photoelectric conversion are arranged, a protective film 22, and a substrate 23 on which the protective film 22 is mounted. LED array 25 which will be described later as a color linear light source, a lens array 26 which forms an image of an original 29 on the light receiving element array 24 which is a light receiving portion, and a transparent parallel with a step similar to that shown in FIG. A plate 31, a support frame 37 for holding the lens array 26 and the transparent parallel plate 31, a transparent plate 27 for placing the document 29, and an exterior case 28 for supporting these members.
[0035]
As shown in FIG. 10A, the lens array 26 is composed of a plurality of rod lenses 36 arranged in a direction parallel to the reading line on the document surface, as in the embodiment shown in FIG. Although being held, the rod lens 36 includes a rod portion 36a and a compensation portion 36b connected to the rod portion 36a and provided near the end on the transparent parallel plate 31 side.
[0036]
The rod portion 36a has the same configuration as the rod 36 shown in FIG. 2 and has the same optical characteristics. In the compensator 36b, the refractive index is distributed in a direction square to the optical axis and in a direction perpendicular to the optical axis so that the light condensing property is enhanced like a convex lens. FIG. 11 is a cross-sectional view showing the operation of the light collecting member in the present embodiment. The light emitted from the light spot A0 at the reference position is incident on the rod portion 36a of the rod lens 36 and then exits from the compensation portion 36b near the end, but the emitted light s21 is erecting at the same magnification as the light emitting point A0. The light condensing at the virtual condensing point BO1 slightly ahead of the position point BO is incident on the transparent parallel plate 31, and among the incident light, the light incident on the first surface 31b has already been described. Based on the principle, the light is condensed at the first light condensing point B011 that is X1 behind B01. The light incident on the second surface 31c is condensed on the second condensing point B012 behind the B011 by X2 based on the principle already described. Based on the principle already described, X1 = d1 · (1− (1 / n1)), X2 = d2 · (1− (1 / n1)), X1> X2, and the distance between B011 and B012 is dc Then, dc = (d1−d2) · (1− (1 / n1)).
[0037]
By the way, the refractive index n1 changes depending on the wavelength of light and becomes larger as the wavelength becomes shorter. Accordingly, the refractive index n1 for light of R, G, and B, which will be described later, is sequentially increased, and accordingly, X1 and X2 are sequentially increased. Therefore, if it remains as it is, the condensing points B011 and B012 tend to move backward as R, G, and B become. However, the position of the virtual condensing point B01 has a property of moving forward as the wavelength of light becomes shorter like the condensing effect of the convex lens due to the action of the compensation portion 36b. It tends to move. Therefore, both of these tendencies complement each other, and the spectral characteristics with respect to the wavelength are reduced by a principle similar to that of the achromatic lens, and the first condensing point B011 and the first collection corresponding to R, G, and B light described later are used. It is possible to make the light spot B012 substantially coincide with a predetermined position separated by a predetermined distance.
[0038]
The operation of the contact image sensor for color image reading shown in FIG. 10 will be described. As shown in FIG. 10B, an LED array 25 that is a linear light source for irradiating a document has an LED (R LED) 25R that emits substantially red light and an LED that emits substantially green light on an LED substrate 25c. Three types of LEDs (G LED) 25G and a substantially blue light emitting LED (B LED) 25B are mixed and arranged in a line in the direction of the reading line. These LEDs are lit in a time-sharing manner for each color when a driving voltage is applied between driving electrodes (not shown) by a light source driving circuit (not shown), and illuminate a reading line on the original surface. Each time, reflected light of the corresponding color component on the original surface is generated.
[0039]
The reflected light also enters the rod lens 36 corresponding to the reflection point in a time-sharing manner for each of R, G, and B colors. The light of each color incident on the rod lens 36 is condensed toward two points almost in a fixed position even if the color changes according to the principle already explained for each color. Therefore, in the case of this example, regarding the reading of each color of the color image of the document, the color image can be read accurately with the same operation and effect by the same principle as that of the contact image sensor shown in FIG.
[0040]
Although the embodiments of the present invention have been described above with reference to the respective examples, the present invention is not limited to these, and can be widely applied to configurations having similar effects. For example, even when the transparent parallel plate (31) as shown in FIG. 1 or the stepped transparent plate (27) as shown in FIG. 8 is brought into contact with the lens array (26), the effect of the present invention is achieved. Can be obtained. The same effect can be obtained when a transparent parallel plate (31) having a step is disposed between the transparent plate (27) having no step and the lens array (26). Further, as shown in FIG. 2, the transparent plate (27) with a step is provided with a plurality of grooves (or steps) perpendicular to the arrangement direction of the lens array (26) like the transparent parallel plate (31) as shown in FIG. When the one is used, or conversely, the transparent parallel plate (31) has a common step provided along the arrangement direction of the lens array 26) like the stepped transparent plate (27) shown in FIG. The effect of the present invention can also be obtained when a structure is used.
[0041]
Furthermore, as a preferred embodiment of the present invention, as shown in FIG. 12 or FIG. 13, the transparent parallel plate 31 includes a first surface 31b and a second surface corresponding to each rod lens 36 of the lens array 26. Some have a plurality of grooves 31d that are configured. Here, FIG. 12 is a view showing a case where the plurality of grooves 31d are orthogonal to the arrangement direction of the lens array 26, (a) is a front view, and (b) is a side view. FIG. 13 is a view showing a case where the plurality of grooves 31d are provided so as to correspond to the rod lenses 36 along the arrangement direction of the lens array 26, (a) is a front view, and (b) is a front view. It is a side view.
[0042]
Such a groove shape can also be applied to the transparent plate (27). The lens array (26) in the present invention can be constituted not only by the rod lens (36) but also by the convex lens 40 as shown in FIG.
[0043]
【The invention's effect】
As described above, according to the present invention, in the contact-type image sensor, an imaging angle of the light receiving unit due to the floating of the original is reduced without limiting the opening angle, and a small-sized and high reading accuracy apparatus is provided. Can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a configuration of a contact image sensor that is one embodiment of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA of FIG.
FIG. 3 is a principle view showing an optical action of a parallel transparent plate.
4 is a diagram illustrating an operation of the contact image sensor illustrated in FIG. 1. FIG.
FIG. 5 is a diagram illustrating an operation of the contact image sensor illustrated in FIG. 1;
6 is a diagram illustrating an operation of the contact image sensor illustrated in FIG. 1. FIG.
7 is a diagram illustrating an operation of the contact image sensor illustrated in FIG. 1. FIG.
FIGS. 8A and 8B are diagrams showing a configuration of a contact image sensor which is one embodiment of the present invention, in which FIG. 8A is a cross-sectional view and FIG. 8B is a top view.
9 is a diagram illustrating an operation of the contact image sensor illustrated in FIG.
10A and 10B are diagrams illustrating a configuration of a contact image sensor that is one embodiment of the present invention, in which FIG. 10A is a cross-sectional view, and FIG. 10B is a cross-sectional view taken along line DD in FIG.
11 is a diagram illustrating an operation of the contact image sensor illustrated in FIG. 10;
FIG. 12 is a diagram illustrating a configuration of a main part of a contact image sensor which is one embodiment of the present invention.
FIG. 13 is a diagram showing a configuration of a main part of a contact image sensor which is one embodiment of the present invention.
FIG. 14 is a diagram showing a configuration of a main part of a contact image sensor which is one embodiment of the present invention.
FIG. 15 is a cross-sectional view showing a configuration of a conventional contact image sensor.
16 is a diagram showing the action of a rod lens used in the contact image sensor shown in FIG.
FIG. 17 is a cross-sectional view showing a configuration of a conventional contact image sensor.
[Explanation of symbols]
24 Light receiving element array
25 LED array
26 Lens array
27 Transparent plate
28 Exterior case
29 Manuscript
31 Transparent parallel plate
36 Rod lens
40 Convex lens

Claims (2)

A transparent plate for placing the original, an illuminating means for irradiating the original surface in a line shape, a condensing means for forming an image of reflected light from the irradiated original surface, and receiving and photoelectrically converting the imaged light In a contact-type image sensor having a plurality of light receiving elements arranged in a line and detecting image data of a document surface by light input to the light receiving element, the light condensing means includes a plurality of lenses arranged in the line direction. have a transparent parallel plate having a plurality of parallel planes having different thicknesses from the base surface provided opposite to the plurality of lenses, and it is the transparent parallel plate is a transparent plate for placing the document Contact type image sensor characterized by The plurality of lenses arranged in the line direction are a plurality of rod lenses arranged in the line direction, and the transparent plate on which the document is placed has a first step portion and a second step formed by surfaces parallel to the document placement surface . stepped portion is provided, the thickness d1 of the first step portion between the thickness d2 of the second step portion has the relationship d11> d12, and the first step portion the boundary of the second stage portion and the rod 2. The contact image sensor according to claim 1 , wherein the transparent plate is positioned so as to be parallel to a lens arrangement direction and to be positioned substantially opposite to a diameter of each rod lens .

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