WO2007126288A1

WO2007126288A1 - Wide dynamic range image sensor

Info

Publication number: WO2007126288A1
Application number: PCT/KR2007/002131
Authority: WO
Inventors: Sungsu Lee; Yongduck Seo
Original assignee: Pixelplus Co Ltd
Current assignee: Pixelplus Co Ltd
Priority date: 2006-05-01
Filing date: 2007-05-01
Publication date: 2007-11-08
Anticipated expiration: 2008-11-01
Also published as: KR20070106827A; KR100785528B1

Abstract

An image sensor having a broad operation range obtains images each having a different exposure degree through a pair of pixels each having a different exposure degree, and combines the images to generate an image having a broad luminance range. The image sensor comprises a pixel array where a plurality of unit pixel groups each including a plurality of pixels each having a different exposure time are arranged in a lattice type, a row driver configured to generate a driving signal required in the operation of the pixel array, and an output circuit configured to receive a sensing signal outputted from the pixel array so as to separate signals of an even number column from those of an odd number column in each unit pixel group.

Description

WIDE DYNAMIC RANGE IMAGE SENSOR

TECHNICAL FIELD

The present invention generally relates to an image sensor having a broad operation range, and more specifically, to an image sensor that obtains images each having a different exposure degree through a pair of pixels each having a different exposure degree, and combines the images to generate an image having a broad luminance range.

BACKGROUND FO THE INVENTION Generally, an image sensor is a device to capture an image using characteristics of a semiconductor device which reacts with a light energy. A light generated from each subject for photograph)' which exists in the natural world has an original value in a wavelength. A pixel of the image sensor senses a light generated from each subject for photography to convert the light into an electric signal. That is, a pixel of the image sensor generates an electric signal depending on a wavelength of a light generated from a subject for photography. The image sensor recognizes an image of the subject for photography using the electric signal.

A general image sensor has a limit in a bandwidth of a recognizable luminance. In other words, if the image sensor photographs an image where an extremely light part and a dark part coexist, the light part is well expressed, and the dark part is blackly expressed overall. While an object of the dark part is well distinguished, an image of the light part becomes white. As a result, it is difficult for the general image sensor to obtain all information of the dark part and the light part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Technical Subject

Various embodiments of the present invention are directed at obtaining images each having a different exposure degree through a pair of pixels each having a different exposure degree, and combining the images to generate an image having a broad luminance range.

Various embodiments of the present invention are directed at combining images obtained from a pair of pixels each having a different exposure degree in each column to generate an image of a broad luminance range.

Various embodiments of the present invention are directed at combining images obtained from a pair of pixels each having a different exposure degree in each row to generate an image of a broad luminance range.

Technical Solution

According to an embodiment of the present invention, an image sensor comprises a pixel array where a plurality of unit pixel groups each including a plurality of pixels and each having a different exposure time are arranged in a lattice type, a row driver configured to generate a driving signal required in the operation of the pixel array, and an output circuit configured to receive a sensing signal outputted from the pixel array so as to separate signals of an even number column from those of an odd number column in each unit pixel group.

According to an embodiment of the present invention, an image sensor comprises a pixel array where a plurality of unit pixel groups each including a plurality of pixels each having a different exposure time are arranged in a lattice type, a row driver configured to generate a driving signal required in the operation of the pixel array, and an output circuit configured to receive a sensing signal outputted from the pixel array so as to separate signals of an even number row from those of an odd number row in each unit pixel group. According to an embodiment of the present invention, an image sensor comprising a pixel array where a plurality of unit pixel groups each including a plurality of pixels each having a different exposure time are arranged in a lattice type.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram illustrating an image sensor having a different exposure degree in each column according to an embodiment of the present invention.

Fig. 2 is a diagram illustrating an image output example of the image sensor of Fig. 1.

Fig. 3 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig. 1.

Fig. 4 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig. 1. Fig. 5 is a block diagram illustrating an image sensor having a different exposure degree in each row according to an embodiment of the present invention.

Fig. 6 is a diagram illustrating an image output example of the image sensor of Fig. 5. Fig. 7 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig.

5.

Fig. 8 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig. 5.

PREFERRED EMBODIMENTS

The present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a block diagram illustrating an image sensor having a different exposure degree in each column according to an embodiment of the present invention. An image sensor having a different exposure degree in each column comprises a row driver 10, a pixel array 20, and an output circuit 30.

The row driver 10 generates a driving signal required in the operation of the pixel array 20. The output circuit 30 receives a sensing signal outputted from the pixel array 20 to separate signals of an even number column from those of an odd number column. The even number column represents column pixels arranged in the even number column of the pixel array 20, and the odd number column represents column pixels arranged in the odd number column of the pixel array 20.

The pixel array 20 includes a plurality of unit pixels arranged in row and column directions. A unit pixel group UPGl consists of a pair of pixels Pl, P2 arranged in the row direction to recognize the same color. A unit pixel group UPG2 consists of a pair of pixels

P3, P4 to recognize a different color from that of the unit pixel group UPGl. The unit pixel groups UPGl and UPG2 which recognize different colors are arranged alternately.

If a general pixel array consists of Red (R), Green (G), and Blue (B) pixels. Each pixel of the present invention arranged in the row direction is formed with patterns such as RRGGRRGG.., GGBBGGBB... In the unit pixel group UPGl, the pixel Pl has a different exposure time from that of the pixel P2.

Although the unit pixel group UPG consists of two pixels in the embodiment of the present invention, a unit pixel group may consist of three or more pixels. In this case, each of three or more pixels has a different exposure time.

Fig. 2 is a diagram illustrating an image output example of the image sensor of Fig. 1. When the pixel array 20 consists of a pixel P of 1280*480, two images each having a pixel P of 640*480 are outputted with a different exposure degree. That is, a pixel signal of 640*480 of the even number column is separated from that of the odd number column, and outputted into the output circuit 30.

Fig. 3 is a circuit diagram illustrating a pair of pixels Pl, P2 in the pixel array 20 of Fig. 1. Fig. 3 shows a 4T-structured sensor having four transistors 110, 120, 130, 140 in one pixel P.

A pixel Pl comprises a photo diode 100, a transmission transistor 110, a reset transistor 120, a drive transistor 130, and a select transistor 140. A pixel P2 comprises a photo diode 101 , a transmission transistor 111 , a reset transistor 121 , a drive transistor 131, and a select transistor 141.

The photo diodes 100, 101 absorb an external light to generate optical charges. The transmission transistors 110, 111 transmit the optical charges from the photo diodes 100, 101 selectively into sensing nodes Nl, N2. The reset transistors 120, 121, which are connected between a power source terminal VDD and the sensing nodes Nl, N2, reset the sensing nodes Nl, N2. The drive transistors 130, 131, which are connected between the power source terminal VDD and the select transistors 140, 141, transmit and amplify electric signals corresponding to the sensing nodes Nl, N2. The select transistors 140, 141, which are connected to one terminal of the drive transistors 130, 131, output sensed signals OUTl, OUT2. A first transmission signal TXl, a second transmission signal TX2, a reset signal

RS, and a line select signal LS outputted from the row driver 10 are applied to a pair of pixels Pl, P2 as follows. That is, the first transmission signal TXl is applied to a gate of the transmission transistor 110 of the pixel Pl of the odd number column. The second transmission signal TX2 is applied to a gate of the transmission transistor 111 of the pixel P2 of the even number column.

The reset signal RS is applied in common to a gate of the reset transistors 120, 121 of the pixels Pl, P2. The line select signal LS is applied in common to a gate of the select transistors 140, 141 of the pixels Pl, P2.

Each exposure time of the pixels Pl, P2 ranges from when the reset signal RS, and the transmission signals TXl, TX2 are enabled simultaneously to when the line select signal LS is enabled and the sensed signals OUTl, 0UT2 are outputted. The line select signal LS is enabled in common in the pixels Pl, P2 of the odd number column and the even number column. As a result, when the first transmission signal TXl and the second transmission signal TX2 are enabled with a predetermined time interval while the reset signal RS is enabled, the exposure degrees of the pixels Pl, P2 of the odd number column and the even number column are differentiated corresponding to the time interval.

Fig. 4 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig. 1. Fig. 4 shows a 3T-structured sensor having three transistors 210, 220, 230 in one pixel P.

A pixel Pl comprises a photo diode 200, a reset transistor 210, a drive transistor 220, and a select transistor 230. A pixel P2 comprises a photo diode 201, a reset transistor 211 , a drive transistor 221 , and a select transistor 231.

The photo diodes 200, 201 absorb an external light to generate optical charges. The reset transistors 210, 211, which are connected between a power source terminal VDD and sensing nodes N3, N4, reset the sensing nodes N3, N4. The drive transistors 220, 221, which are connected between the power source terminal VDD and the select transistors 230, 231, transmit and amplify electric signals corresponding to the sensing nodes N3, N4. The select transistors 230, 231, which are connected to one terminal of the drive transistors 220, 221, output sensed signals OUT3, OUT4.

A first reset signal RSl, a second reset signal RS2, and a line select signal LS outputted from the row driver 10 are applied to a pair of pixels Pl, P2 as follows. That is, the first reset signal RSl is applied to a gate of the reset transistor 210 of the pixel Pl of the odd number column. The second reset signal RS2 is applied to a gate of the reset transistor 211 of the pixel P2 of the even number column. The line select signal LS is applied in common to a gate of the select transistors 230, 231 of the pixels Pl, P2.

Each exposure time of the pixels Pl, P2 ranges from when the reset signal RSl, RS2 are enabled to when the line select signal LS is enabled and the sensed signals OUT3, OUT4 are outputted.

The line select signal LS is enabled in common in the pixels Pl, P2 of the odd number column and the even number column. As a result, when the first reset signal RSl and the second reset signal RS2 are enabled with a predetermined time interval, the exposure degrees of the pixels Pl, P2 of the odd number column and the even number column are differentiated corresponding to the time interval. Fig. 5 is a block diagram illustrating an image sensor having a different exposure degree in each row according to an embodiment of the present invention.

An image sensor having a different exposure degree in each row comprises a row driver 310, a pixel array 320, and an output circuit 330.

The row driver 310 generates a driving signal required in the operation of the pixel array 320. The output circuit 330 receives a sensing signal outputted from the pixel array 320 to separate signals of an even number row from those of an odd number row.

The even number row represents column pixels arranged in the even number row of the pixel array 320, and the odd number row represents row pixels arranged in the odd number row of the pixel array 320. The pixel array 320 includes a plurality of unit pixels arranged in row and column directions. A unit pixel group UPGl consists of a pair of pixels Pl, P2 arranged in the column direction to recognize the same color. A unit pixel group UPG2 consists of a pair of pixels P3, P4 to recognize a different color from that of the unit pixel group UPGl.

The unit pixel groups UPGl and UPG2 which recognize different colors are arranged alternately.

If a general pixel array consists of Red (R), Green (G), and Blue (B) pixels.

Each pixel of the present invention arranged in the column direction is formed with patterns such as RRGGFJlGG.., GGBBGGBB... In the unit pixel group UPGl, the pixel

Pl has a different exposure time from that of the pixel P2. Although the unit pixel group UPG consists of two pixels in the embodiment of the present invention, a unit pixel group may consist of three or more pixels. In this case, each of three or more pixels has a different exposure time.

Fig. 6 is a diagram illustrating an image output example of the image sensor of

Fig. 5. When the pixel array 320 consists of a pixel P of 640*960, two images each having a pixel P of 640*480 are outputted with a different exposure degree. That is, a pixel signal of 640*480 of the even number row is separated from that of the odd number row, and outputted into the output circuit 330.

Fig. 7 is a circuit diagram illustrating a pair of pixels Pl, P2 in the pixel array 320 of Fig. 5. Fig. 7 shows a 4T-structured sensor having four transistors 410, 420, 430, 440 in one pixel P. A pixel Pl comprises a photo diode 400, a transmission transistor 410, a reset transistor 420, a drive transistor 430, and a select transistor 440. A pixel P2 comprises a photo diode 401, a transmission transistor 411, a reset transistor 421, a drive transistor 431, and a select transistor 441.

The photo diodes 400, 401 absorb an external light to generate optical charges. The transmission transistors 410, 411 transmit the optical charges from the photo diodes 400, 401 selectively into sensing nodes N5, N6. The reset transistors 420, 421, which are connected between a power source terminal VDD and the sensing nodes N5, N6, reset the sensing nodes N5, N6. The drive transistors 430, 431, which are connected between the power source terminal VDD and the select transistors 440, 441, transmit and amplify electric signals corresponding to the sensing nodes N5, N6. The select transistors 440, 441, which are connected to one terminal of the drive transistors 430, 431, output sensed signals OUT5, OUT6.

A first transmission signal TXl, a second transmission signal TX2, a first reset signal RSl, a second reset signal RS2, and a line select signal LS outputted from the row driver 310 are applied to a pair of pixels Pl, P2 as follows.

That is, the first transmission signal TXl is applied to a gate of the transmission transistor 410 of the pixel Pl of the odd number row. The second transmission signal TX2 is applied to a gate of the transmission transistor 411 of the pixel P2 of the even number row. The first reset signal RSl is applied to a gate of the reset transistor 420 of the pixel Pl of the odd number row. The second reset signal RS2 is applied to a gate of the reset transistor 421 of the pixel P2 of the even number row. The line select signal LS is applied in common to a gate of the select transistors 440, 441 of the pixels Pl, P2.

Each exposure time of the pixels Pl, P2 ranges from when the reset signal RSl, RS2, and the transmission signals TXl, TX2 are enabled simultaneously to when the line select signal LS is enabled and the sensed signals OUT5, OUT6 are outputted.

The line select signal LS is enabled in common in the pixels Pl, P2 of the odd number row and the even number row. As a result, when the first transmission signal TXl and the second transmission signal TX2 are enabled with a predetermined time interval, the exposure degrees of the pixels Pl, P2 of the odd number row and the even number row are differentiated corresponding to the time interval. Fig. 8 is a circuit diagram illustrating a pair of pixels of the image sensor of Fig.

5. Fig. 8 shows a 3T-stmctured sensor having three transistors 510, 520, 530 in one pixel P.

A pixel Pl comprises a photo diode 500, a reset transistor 510, a drive transistor 520, and a select transistor 530. A pixel P2 comprises a photo diode 501, a reset transistor 511 , a drive transistor 521, and a select transistor 531.

The photo diodes 500, 501 absorb an external light to generate optical charges. The reset transistors 510, 511, which are connected between a power source terminal VDD and sensing nodes N7, N8, reset the sensing nodes N7, N8. The drive transistors 520, 521, which are connected between the power source terminal VDD and the select transistors 530, 531, transmit and amplify electric signals corresponding to the sensing nodes N7, N8. The select transistors 530, 531, which are connected to one terminal of the drive transistors 520, 521, output sensed signals OUT7, OUT8.

A first reset signal RSl, a second reset signal RS2, and a line select signal LS outputted from the row driver 310 are applied to a pair of pixels Pl, P2 as follows. That is, the first reset signal RSl is applied to a gate of the reset transistor 510 of the pixel Pl of the odd number row. The second reset signal RS2 is applied to a gate of the reset transistor 511 of the pixel P2 of the even number row. The line select signal LS is applied in common to a gate of the select transistors 530, 531 of the pixels Pl, P2.

Each exposure time of the pixels Pl, P2 ranges from when the reset signal RSl, RS2 are enabled to when the line select signal LS is enabled and the sensed signals OUT7, OUT8 are outputted.

The line select signal LS is enabled in common in the pixels Pl, P2 of the odd number row and the even number row. As a result, when the first reset signal RSl and the second reset signal RS2 are enabled with a predetermined time interval, the exposure degrees of the pixels Pl, P2 of the odd number row and the even number row are differentiated corresponding to the time interval. INDUSTRIAL APPLICABILITY

As described above, according to an embodiment of the present invention, an image sensor having a broad operation range comprises a pixel array.

The image sensor obtains image each having a different exposure degree through a pair of pixels each having a different exposure degree, and combines the images to generate an image having a broad luminance image.

The image sensor does not require an additional frame buffer for storing several images.

While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and described in detail herein. However, it should be understood that the invention is not limited to the particular forms disclosed. Rather, the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined in the appended claims.

Claims

What is Claimed is:

1. An image sensor comprising: a pixel array where a plurality of unit pixel groups each including a plurality of pixels and each having a different exposure time are arranged in a lattice type; a row driver configured to generate a driving signal required in the operation of the pixel array; and an output circuit configured to receive a sensing signal outputted from the pixel array so as to separate signals of an even number column from those of an odd number column in each unit pixel group.

2. The image sensor according to claim 1, wherein the plurality of pixels are arranged adjacently in the same row to recognize the same color.

3. The image sensor according to claim 1, wherein the unit pixel groups are arranged alternately in row and column directions to recognize different colors.

4. The image sensor according to claim 1, wherein each of the plurality of pixels comprises: a first photo diode configured to absorb an external light so as to generate optical charges; a first transmission transistor configured to selectively transmit optical charges from the first photo diode into a sensing node; a first reset transistor connected between a power terminal and the sensing node, and configured to reset the sensing node; a first drive transistor connected to one side of the power terminal, and configured to transmit and amplify an electric signal corresponding to the sensing node; and a first select transistor connected to one end of the first drive transistor, and configured to output the sensing signal into the output circuit.

5. The image sensor according to claim 4, wherein each of the plurality of pixels regulates an enable interval of the first transmission transistor to adjust the exposure time.

6. The image sensor according to claim 4, wherein the unit pixel group consists of a pair of pixe Is, a first transmission signal is applied to a gate of a transmission transistor of the first one of the pixels, a second transmission signal is applied to a gate of a transmission transistor of the second one of the pixels, a reset signal is applied in common to gates of first and second transistors of the pixels, and a line select signal is applied in common to gates of first and second select transistors of the pixels.

7. The image sensor according to claim 1, wherein each of the plurality of pixels comprises: a second photo diode configured to absorb an external light so as to generate optical charges; a second reset transistor connected between a power source terminal and a sensing node, and configured to reset the sensing node; a second drive transistor connected to one side of the power source terminal, and configured to transmit and amplify an electric signal corresponding to the sensing node; and a second select transistor connected to one terminal of the second drive transistor, and configured to output the sensing signal into the output circuit.

8. The image sensor according to claim 7, wherein the plurality of pixels adjust an enable interval of the second reset transistor to regulate the exposure time.

9. The image sensor according to claim 7, wherein the unit pixel group consists of a pair of pixels, a first reset signal is applied to a gate of a reset transistor of the first one of the pixels, a second reset signal is applied to a gate of a reset transistor of the second one of the pixels, a line select signal is applied in common to a gate of first and second select transistors of the pixels.

10. An image sensor comprising: a pixel array where a plurality of unit pixel groups each including a plurality of pixels each having a different exposure time are arranged in a lattice type; a row driver configured to generate a driving signal required in the operation of the pixel array; and an output circuit configured to receive a sensing signal outputted from the pixel array so as to separate signals of an even number row from those of an odd number row in each unit pixel group.

11. The image sensor according to claim 10, wherein the plurality of pixels are arranged adjacently in the same column to recognize the same color.

12. The image sensor according to claim 10, wherein the unit pixel groups are arranged alternately in row and column directions to recognize different colors.

13. The image sensor according to claim 10, wherein each of the plurality of pixels comprises: a first photo diode configured to absorb an external light so as to generate optical charges; a first transmission transistor configured to selectively transmit optical charges from the first photo diode into a sensing node; a first reset transistor connected between a power terminal and the sensing node, and configured to reset the sensing node; a first drive transistor connected to one side of the power terminal, and configured to transmit and amplify an electric signal corresponding to the sensing node; and a first select transistor connected to one end of the first drive transistor, and configured to output the sensing signal into the output circuit.

14. The image sensor according to claim 13, wherein each of the plurality of pixels regulates an enable interval of the first transmission transistor to adjust the exposure time.

15. The image sensor according to claim 13, wherein the unit pixel group consists of a pair of pixels, a first transmission signal is applied to a gate of a transmission transistor of the first one of the pixels, a second transmission signal is applied to a gate of a transmission transistor of the second one of the pixels, a reset signal is applied in common to gates of first and second transistors of the pixels, and a line select signal is applied in common to gates of first and second select transistors of the pixels.

16. The image sensor according to claim 10, wherein each of the plurality of pixels comprises: a second photo diode configured to absorb an external light so as to generate optical charges; a second reset transistor connected between a power source terminal and a sensing node, and configured to reset the sensing node; a second drive transistor connected to one side of the power source terminal, and configured to transmit and amplify an electric signal corresponding to the sensing node; and a second select transistor connected to one terminal of the second drive transistor, and configured to output the sensing signal into the output circuit.

17. The image sensor according to claim 16, wherein the plurality of pixels adjust an enable interval of the second reset transistor to regulate the exposure time.

18. The image sensor according to claim 16, wherein the unit pixel group consists of a pair of pixels, a first reset signal is applied to a gate of a reset transistor of the first one of the pixels, a second reset signal is applied to a gate of a reset transistor of the second one of the pixels, a line select signal is applied in common to a gate of first and second select transistors of the pixels.

19. An image sensor comprising a pixel array where a plurality of unit pixel groups each including a plurality of pixels each having a different exposure time are arranged in a lattice type.

20. The image sensor according to claim 19, wherein the plurality of pixels of the unit pixel group are arranged adjacently in the same row.

21. The image sensor according to claim 19, wherein the plurality of pixels of the unit pixel group are arranged adjacently in the same column.