JP2008198017A - Imaging device and optical information reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging device which can obtain an equal incident light quantity in a light receiving element disposed in a peripheral part and a light receiving element disposed in a central part in an image sensor. <P>SOLUTION: A masking plate 60 having openings 60a and 60b corresponding respectively to light receiving elements 58 of a light receiving sensor (image sensor) 23 is disposed on the light receiving elements 58. Since each opening of the masking plate 60 is formed so that the size thereof is small in the central part of the image sensor as shown in Fig.2(A) and large in the peripheral part thereof as shown in Fig.2(B), the incident light quantity in the light receiving elements 58 in the central part provided with the small openings 60a is reduced, while the incident light quantity in the light receiving elements 58 of the peripheral part provided with the large openings 60b is not reduced. Consequently, the light receiving elements 58 disposed in the central part shown in Fig.4(A) and the light receiving elements 58 disposed in the peripheral part shown in Fig.4(B) can receive equal incident light quantity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an image sensor including a plurality of light receiving elements that accumulate electric charges according to an incident light amount, an imaging device including a linear sensor, and an optical information reading device that reads an information code using the imaging device.

An imaging device including an image sensor is used in a digital camera, an optical information reader, or the like. The image sensor includes a light receiving element (photodiode) that constitutes pixels arranged in a matrix by accumulating charges according to the amount of incident light, and a plurality of light receiving elements that are provided corresponding to the light receiving elements and that collect light on the light receiving elements. Microlenses. The image is formed on the light receiving surface (light receiving element) of the image sensor through an imaging lens.

In the optical system of the imaging apparatus, the light amount in the peripheral portion of the imaging lens falls with respect to the central portion of the image sensor due to the peripheral light amount ratio and the cosine fourth law.

Further, in the optical system of the image pickup apparatus, exit pupil shading is generated by a microlens that collects light at each light receiving element. This phenomenon will be described with reference to FIG. A condensing microlens 152 is arranged on the light receiving element 158 constituting each pixel 150 of the image sensor. Here, as shown in FIG. 9A, light is emitted at an angle θ1 close to a parallel line with the central axis of the microlens 152 with respect to the microlens 152 of the light receiving element 158 disposed at the center of the image sensor. With respect to the incident light, as shown in FIG. 9B, the microlens 152 of the light receiving element 158 disposed in the peripheral portion of the image sensor has a large angle from a parallel line with the central axis of the microlens 152. Light enters at θ2. Accordingly, the light amount of the light receiving element 158 in the peripheral portion shown in FIG. 9B is reduced with respect to the light receiving element 158 in the central portion shown in FIG. 9A. Patent Documents 1 and 2 disclose an image reading device including a pudging correction unit.
JP-A-8-275003 Japanese Patent Laid-Open No. 10-255731

In order to cope with a decrease in the amount of light at the periphery of the image sensor, measures such as designing the exit pupil distance of the imaging lens to be long have been taken, but in particular, the area sensor has a horizontally long one-dimensional code such as a barcode. When reading with an optical information reader, the area sensor may reduce the amount of light at the peripheral portion and the amount of light at both ends of the barcode may be insufficient, making it impossible to read.

In the shoeing correction means disclosed in Patent Documents 1 and 2, in order to increase the amount of light at the peripheral portion, the gain of the image signal is adjusted by looking at the difference between the central luminance and the peripheral luminance. In order to realize such correction, it is necessary to mount an expensive DSP (digital signal processor) inside the image sensor, which increases the price of the image sensor, and further downsizing the optical information reader. However, the problem of increasing the size of the image sensor arises.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide the same incident between a light receiving element arranged at the peripheral portion and a light receiving element arranged at the central portion in the image sensor. An object of the present invention is to provide an imaging apparatus capable of obtaining a light amount and an optical information reading apparatus including the imaging apparatus.

In order to achieve the above object, the invention of claim 1 includes a plurality of light receiving elements 58 that constitute a pixel by accumulating charges according to the amount of incident light,
A plurality of lenses 52 respectively provided corresponding to the light receiving elements 58 and condensing on the light receiving elements 58, and sequentially reading out signals from the plurality of light receiving elements 58 in a predetermined cycle. In an imaging apparatus including the image sensor 23,
The light blocking means 60 is formed with openings 60a and 60b corresponding to the light receiving elements 58 on the light receiving element 58, respectively. The size of each opening is small in the central portion of the image sensor and large in the peripheral portion. It is a technical feature that the light blocking means 60 formed as described above is provided.

The invention according to claim 2 is configured to store a plurality of light receiving elements 58 constituting a pixel by accumulating charges according to the amount of incident light,
An image that is provided corresponding to each of the light receiving elements 58 and that has a plurality of lenses 58 that condense on the light receiving elements 58 and that sequentially outputs signals read from the plurality of light receiving elements in a predetermined cycle. In an imaging apparatus including the sensor 23,
A technical feature is that a light blocking means 60 for limiting the transmission of light is provided only in the central portion of the light receiving element 58.

In the image pickup apparatus according to the first aspect, the light blocking means having openings respectively corresponding to the light receiving elements of the image sensor is arranged on the light receiving element. Since the size of each opening of the light blocking means is small at the center of the image sensor and large at the periphery, the amount of incident light at the light receiving element in the center with a small size of the aperture is reduced, The amount of incident light at the peripheral light receiving element having a large aperture does not decrease. Thereby, the same incident light quantity can be obtained with the light receiving element arrange | positioned in a center part, and the light receiving element arrange | positioned in a peripheral part.

In the image pickup apparatus according to the second aspect, the light blocking means for restricting the transmission of light is disposed only in the central portion of the light receiving element of the image sensor. The amount of incident light at the light receiving element in the central portion where the light blocking means is provided is reduced, and the amount of incident light at the peripheral light receiving elements where the light blocking means is not provided is not reduced. Thereby, the same incident light quantity can be obtained with the light receiving element arrange | positioned in a center part, and the light receiving element arrange | positioned in a peripheral part.

According to another aspect of the present invention, the light blocking means is composed of a masking plate having openings corresponding to the light receiving elements. For this reason, the transmission of light can be reliably limited by the opening of the masking plate.

According to the fourth aspect of the present invention, since the imaging device that can obtain the same amount of incident light by the light receiving element arranged in the central part and the light receiving element arranged in the peripheral part is used, the information code is surely provided even in the peripheral part of the imaging range. In particular, even a long information code such as a barcode can be reliably read because the amount of incident light is not reduced at both ends (peripheral portions).

[First embodiment]
Hereinafter, an embodiment of an optical information reading apparatus including an imaging apparatus of the present invention will be described with reference to the drawings. First, an outline of the configuration of the optical information reading apparatus according to the first embodiment will be described with reference to the block diagram of FIG.
The optical information reader 10 that reads the barcode B is provided with a circuit unit 20. The circuit unit 20 mainly includes an optical system such as a light emitting diode 21, a condensing lens 24, a light receiving sensor 23, and an imaging lens 27, and a microcomputer such as a memory 35, a control circuit 40, an operation switch 22, and a liquid crystal display 46. (Hereinafter referred to as “microcomputer”) and a power system such as a power switch 41 and a power circuit 49.

First, the optical system will be described. The light emitting diode 21 functions as a light irradiator capable of irradiating the strip-shaped illumination light Lf, and is condensed by a condensing lens 24 in which a diffusion lens and a convex lens are combined. The light receiving sensor 23 is configured to receive the reflected light Lr irradiated and reflected on the reading object R or the two-dimensional code Q through the imaging lens 27. For example, a photodiode type C-MOS or the like is used. This corresponds to an image sensor in which light receiving elements, which are solid-state imaging elements, are arranged two-dimensionally in m rows and n columns on the order of 1 million. The imaging lens 27 functions as an imaging optical system capable of condensing incident light incident from the outside and forming an image on the light receiving surface 23a of the light receiving sensor 23. And a plurality of condensing lenses.

Next, a configuration outline of the microcomputer system will be described. The microcomputer system includes an amplification circuit 31, an A / D conversion circuit 33, a memory 35, an address generation circuit 36, a synchronization signal generation circuit 38, a control circuit 40, an operation switch 22, an LED 43, a buzzer 44, a liquid crystal display 46, and a communication interface 48. Etc. As the name suggests, this microcomputer system is composed mainly of a control circuit 40 and a memory 35 that can function as a microcomputer (information processing device). The signal can be processed by software. The control circuit 40 also performs control related to the entire system of the optical information reading apparatus 10.

An image signal (analog signal) output from the light receiving sensor 23 of the optical system is input to the amplification circuit 31 and amplified by a predetermined gain, and then input to the A / D conversion circuit 33. Converted into a digital signal. The digitized image signal, that is, image data (image information) is input to the memory 35 and stored. The synchronization signal generation circuit 38 is configured to generate a synchronization signal for the light receiving sensor 23 and the address generation circuit 36. The address generation circuit 36 is based on the synchronization signal supplied from the synchronization signal generation circuit 38. Thus, the storage address of the image data stored in the memory 35 can be generated.

The control circuit 40 is a microcomputer capable of controlling the entire optical information reading device 10 and includes a CPU, a system bus, an input / output interface, and the like. The control circuit 40 can constitute an information processing device together with the memory 35 and has an information processing function. The control circuit 40 is configured to be connectable to various input / output devices (peripheral devices) via a built-in input / output interface. In the case of this embodiment, the power switch 41, the operation switch 22, the LED 43, A buzzer 44, a liquid crystal display 46, a communication interface 48, and the like are connected.

FIG. 2 is an explanatory view of a light receiving element (photodiode) 58 constituting each pixel of the light receiving sensor 23 composed of a photodiode type C-MOS image sensor, and FIG. 3 is a masking plate 60 provided in the light receiving sensor 23. FIG.
As shown in FIG. 2, the light receiving elements 58 constituting each pixel 50 formed in a matrix in the image sensor are formed immediately below the substrate 56, and a wiring pattern 54 is formed on the upper surface of the substrate 56. Yes. A micro lens 52 is provided on the light receiving element 58 so as to face the light receiving element 58. A masking plate 60 shown in FIG. 3 is provided immediately below the microlens 52. As shown in FIG. 2A, an opening 60a having a relatively small opening diameter is provided immediately below the pixel microlens 52 provided in the center of the light receiving sensor (image sensor) 23. An opening 60b having a relatively large opening diameter is provided immediately below the microlens 52 for the pixel provided in.

In the optical information reading apparatus according to the first embodiment, the masking plate 60 formed with openings 60 a and 60 b corresponding to the light receiving elements 58 of the light receiving sensor (image sensor) 23 is disposed on the light receiving element 58. The size of each opening of the masking plate 60 is small at the center of the image sensor as shown in FIG. 2 (A) and large at the periphery as shown in FIG. 2 (B). The amount of incident light at the central light receiving element 58 provided with the small opening 60a is reduced, and the amount of incident light at the peripheral light receiving element 58 provided with the large opening 60b is not reduced. Accordingly, an equivalent amount of incident light can be obtained between the light receiving element 58 disposed in the central portion illustrated in FIG. 4A and the light receiving element 58 disposed in the peripheral portion illustrated in FIG.

Furthermore, in the optical information reading device 10 of the first embodiment, since the imaging device that can obtain the same incident light amount with the light receiving element 58 disposed in the central portion and the light receiving element 58 disposed in the peripheral portion is used, The information code can be read reliably even at the periphery of the imaging range, especially for long information codes such as barcodes, since the amount of incident light does not decrease at both ends (peripheral parts). Can do.

[Second Embodiment]
Subsequently, an imaging apparatus of the optical information reading apparatus according to the second embodiment of the present invention will be described with reference to FIGS. Since the second embodiment has the same configuration as that of the first embodiment except for the configuration of the light receiving sensor, only the configuration of the light receiving sensor will be described with reference to FIGS. 4 and 5.
FIG. 4 is an explanatory view of a light receiving element (photodiode) 58 constituting each pixel of the light receiving sensor composed of a photodiode type C-MOS image sensor, and FIG. 5 shows a masking plate 60 provided in the light receiving sensor 23. It is a top view.
As shown in FIG. 5, a masking plate 60 having an opening 60c is disposed at the center of the light receiving sensor 23. That is, as shown in FIG. 4A, an opening 60c of the masking plate 60 is provided directly below the pixel microlens 52 provided in the center of the light receiving sensor (image sensor) 23, and FIG. The masking plate 60 is not provided in the pixel microlens 52 provided in the peripheral portion shown in FIG.

In the optical information reading apparatus of the second embodiment, the masking plate 60 that restricts the transmission of light through the opening 20c is disposed only in the central portion of the light receiving element 58 of the image sensor 23. The amount of incident light at the light receiving element 58 in the central portion where the masking plate 60 shown in FIG. 4A is provided is reduced, and the light receiving element 58 in the peripheral portion where the masking plate 60 is not provided as shown in FIG. The amount of incident light is not reduced. Accordingly, an equivalent amount of incident light can be obtained between the light receiving element 58 disposed in the central portion illustrated in FIG. 4A and the light receiving element 58 disposed in the peripheral portion illustrated in FIG.

[Third embodiment]
Subsequently, an imaging apparatus of the optical information reading apparatus according to the third embodiment of the present invention will be described with reference to FIG. In the first embodiment, the size of the opening of the masking plate 60 is changed. In the third embodiment, as shown in FIG. 6, the size of the opening is adjusted by making the thickness of the grating 60 </ b> K constituting the masking plate 60 thick at the center and thin at the periphery.

[Fourth embodiment]
Next, an image pickup apparatus of an optical information reading apparatus according to the fourth embodiment of the present invention will be described with reference to FIG. In the first to third embodiments, the masking plate is used for adjusting the light amount. In contrast, in the fourth embodiment, the amount of light is adjusted by applying black printing 59 to the surface of the microlens 52. That is, the size of the opening 59a of the black print 59 is formed to be small at the center of the image sensor as shown in FIG. 7A and large at the periphery as shown in FIG. 7B. Therefore, the amount of incident light at the central light receiving element 58 provided with the small opening 59a is reduced, and the amount of incident light at the peripheral light receiving element 58 provided with the large opening 59b is not reduced. As a result, the same amount of incident light can be obtained by the light receiving element 58 arranged at the center of the image sensor shown in FIG. 7A and the light receiving element 58 arranged at the peripheral part shown in FIG. 7B. it can.

[Fifth Embodiment]
An imaging apparatus of an optical information reading apparatus according to a third embodiment of the present invention will be described with reference to FIG. In the first to third embodiments, a masking plate is applied to the image sensor. On the other hand, in the fifth embodiment, as shown in FIG. 8, a masking plate 160 is applied to a linear sensor 70 of an optical information reading apparatus that reads a one-dimensional code such as a barcode. The linear sensor 70 does not include a microlens. A masking plate 160 having an opening 160 a is provided at the center of the linear sensor 70 and limits the amount of light at the light receiving sensor 78 at the center of the linear sensor 70.

In the optical information reading apparatus of the fifth embodiment, the amount of incident light at the light receiving element 78 in the central portion where the masking plate 160 is provided is reduced, and the amount of incident light at the peripheral light receiving element 78 where the masking plate 160 is not provided. Will not decrease. Thereby, the same incident light quantity can be obtained with the light receiving element 78 arranged in the central part and the light receiving element 78 arranged in the peripheral part. As a result, the amount of incident light does not decrease at both ends of the bar code (peripheral portions of the linear sensor), so that it can be read reliably.

In the embodiment described above, the masking plate having an opening formed in a rectangular shape is illustrated, but various shapes such as a circle, an ellipse, and an oval can be applied to the opening. In the above-described embodiment, an example in which a photodiode type C-MOS image sensor is used as an image sensor is illustrated. However, the present invention is applicable to a photogate type C-MOS image sensor and other types of C-MOS image sensors. -It can be applied to MOS image sensors and also to CCDs.

It is a block diagram which shows the circuit structure of the optical information reader which concerns on 1st Embodiment of this invention. It is explanatory drawing of the light receiving element which comprises each pixel of the light receiving sensor (image sensor) of the optical information reader which concerns on 1st Embodiment, FIG. 2 (A) shows the light receiving element of the center part of an image sensor, FIG. B) shows the light receiving elements in the peripheral portion. It is a top view of the masking board provided in the light reception sensor of a 1st embodiment. It is explanatory drawing of the light receiving element which comprises each pixel of the light receiving sensor (image sensor) of the optical information reader which concerns on 2nd Embodiment, FIG. 4 (A) shows the light receiving element of the center part of an image sensor, FIG. B) shows the light receiving elements in the peripheral portion. It is a top view of the masking board provided in the light reception sensor of a 2nd embodiment. It is a top view of the masking board provided in the light reception sensor of a 3rd embodiment. It is explanatory drawing of the light receiving element which comprises each pixel of the light receiving sensor (image sensor) of the optical information reader which concerns on 4th Embodiment, FIG. 7 (A) shows the light receiving element of the center part of an image sensor, FIG. B) shows the light receiving elements in the peripheral portion. It is a top view of the masking board provided in the light reception sensor of a 5th embodiment. 9A and 9B are explanatory diagrams of a light receiving element constituting each pixel of a conventional light receiving sensor (image sensor). FIG. 9A shows a light receiving element at the center of the image sensor, and FIG. 9B shows a light receiving element at a peripheral part. Is shown.

Explanation of symbols

10 Optical information reader 23 Light receiving sensor (image sensor)
40 Control circuit B Barcode 50 Pixel 52 Micro lens 58 Light receiving sensor 60 Masking plate 60a, 60b, 60c Opening 70 Linear sensor 78 Light receiving sensor 160 Masking plate 160a Opening

Claims (4)

A plurality of light receiving elements that form a pixel by accumulating charges according to the amount of incident light; and
A plurality of lenses that are provided corresponding to the light receiving elements, respectively, and that output signals sequentially read from the plurality of light receiving elements in a predetermined cycle. In the imaging device,
A light blocking means in which openings corresponding to the light receiving elements are formed on the light receiving elements, each opening being formed such that the size of each opening is small in the central portion and large in the peripheral portion. An imaging apparatus comprising light blocking means. A plurality of light receiving elements that form a pixel by accumulating charges according to the amount of incident light; and
A plurality of lenses that are provided corresponding to the light receiving elements, respectively, and that output signals sequentially read from the plurality of light receiving elements in a predetermined cycle. In the imaging device,
An image pickup apparatus comprising a light blocking means for restricting light transmission only at a central portion of the light receiving element. 3. The image pickup apparatus according to claim 1, wherein the light blocking means includes a masking plate having openings corresponding to the light receiving elements. An optical information reading device comprising the imaging device according to claim 1.

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