JPH0691658B2 - Image sensor readout method - Google Patents

Description

The present invention relates to a photoelectric conversion unit, a vertical charge transfer unit independent of the photoelectric conversion unit, and a first horizontal charge transfer unit, and a charge storage unit. A second horizontal charge transfer unit attached to this storage unit is provided, and in this case, the vertical charge transfer unit not only transfers the charges formed in the photoelectric conversion unit but also performs photoelectric conversion by itself. A signal of two colors (for example, R and B) of the three primary colors can be formed in the photoelectric conversion unit, and a signal of the remaining one color (for example, G) can be formed in the vertical charge transfer unit. The present invention relates to a reading method of a frame interline transfer type image sensor incorporated in a camera capable of turning on and off incident light.

2. Description of the Related Art A vertical charge transfer CCD is provided separately from a photoelectric conversion unit, and a storage unit, so to speak, a frame transfer and interline transfer type image sensor is used by combining a vertical CCD with a camera having a shutter.
It is possible to perform photoelectric conversion by itself. Therefore, in comparison with an interline transfer type image sensor having the same number of photoelectric conversion elements in the same area, theoretically, twice the resolving power should be obtained.

Problems to be Solved by the Invention However, in reality, four transfer electrodes are provided for each element on the vertical CCD, and one CCD element is two photoelectric conversion elements assigned to the R signal and the B signal, respectively. It comes with. Therefore, the number of CCD elements assigned to the G signal is the same as that of the elements for R or B, respectively, and the total number of elements is only 1.5 times that of the interline image sensor.

On the other hand, since the G signal forms a luminance signal and the human eye is most sensitive to the G color region, the sensory resolution is mainly controlled by the resolution of the G signal. Therefore, the number of G signal elements is R
It is desirable that the number is larger than the number of elements of the signal or the B signal, for example, doubled.

It is an object of the present invention to provide an image sensor readout method which can make full effective use of each element of an existing frame interline transfer type image sensor and has a high resolution, particularly a sensory resolution. .

According to the invention, this object is solved by carrying out the following steps. That is, open the shutter.

The signal charges of the first color (G) formed in the vertical charge transfer unit during exposure are transferred at high speed to the storage unit.

Continuing the exposure, the signal charge of the first color (G ′) is formed in the vertical charge transfer portion.

 Close the shutter.

One of the first color (G ′) signal charges from the vertical charge transfer unit via the first horizontal charge transfer unit and the other first color from the storage unit via the second horizontal charge transfer unit. The signal charges of (G) are read out alternately.

The signal charge of the second color (for example, R) is transferred from the photoelectric conversion unit to the vertical charge transfer unit.

The signal charges of the second color (for example, R) are transferred at high speed from the vertical charge transfer unit to the storage unit.

The signal charge of the third color (for example, B) is transferred from the photoelectric conversion unit to the vertical charge transfer unit.

A signal charge of a third color (for example, B) from the vertical charge transfer unit via the first horizontal charge transfer unit, and a second color (for example, R) from the storage unit via the second horizontal charge transfer unit. The signal charges of are alternately read.

Operation The image sensor used in the method of the present invention comprises a frame transfer type storage section and an interline transfer type vertical transfer section. Since the vertical transfer section is not provided with an optical shield, it is possible to form the optical signal charge by itself. For example, a micro color filter is provided on the photoelectric conversion unit and the vertical transfer unit, each element of the photoelectric conversion unit is assigned to the color of R or B, and the vertical transfer unit outputs the G color signal. Is configured to occur.

A charge transfer electrode made of polysilicon is provided in the vertical transfer section. The vertical transfer unit includes one R photoelectric conversion element and one R photoelectric conversion element.
It has one transfer element attached to one B photoelectric conversion element. One transfer element has four transfer electrodes and transfers charges by four-phase driving. Therefore, the number of elements of each color G, B, R in one image sensor is the same. According to the image sensor reading method of the present invention, the resolution of an apparent G image can be doubled by transferring the G signal charge to the storage portion at high speed during exposure. That is, this produces the effect of doubling the number of G elements equivalently. For the above reasons, the perceptual resolution is significantly improved.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the construction of an image sensor used in carrying out the method according to the invention. In the upper part of the figure, photoelectric conversion elements R and B and a vertical charge transfer section G are shown. These symbols then represent the colors of the transmitted light of the microcolor filters arranged on the elements, each element being assigned to the color represented by the symbols R, B, G. Although not shown in detail in the drawing, a switch is provided between the photoelectric conversion elements R and B and the vertical charge transfer element G. Transparent electrodes 1 arranged in the horizontal direction to control the transfer of charges are provided on the element. These electrodes 1 are arranged in groups of four in the vertical direction and are controlled by a four-phase clock. One set of electrodes forms one vertical charge transfer element G, and as is clear from the figure, one vertical transfer element G is attached to two photoelectric conversion elements R and B.

According to the present invention, the vertical transfer element G simultaneously operates as the photoelectric conversion element G. Therefore, if this image sensor is read by the conventional method, one G signal is read corresponding to one R signal and one B signal. According to the present invention, the signal charges generated in the vertical transfer section G are transferred at high speed to the storage section 2 once during the exposure, so that the G'signal is formed again in the vertical transfer section G after the transfer, and equivalently. It is possible to obtain the effect of providing twice the transformer element G.

When reading a signal, the signal charge in the vertical charge transfer unit is read out via the first horizontal charge transfer unit HCCD1, and the signal charge in the storage unit is read out via the second horizontal charge transfer unit HCCD2.

2 and 3 show examples of post-processing of signals read from the image sensor according to the present invention. Here, the read signal is shown as being recorded on the magnetic disk.

FIG. 2A shows the first horizontal charge transfer units HCCD1 to G '.
An operation of reading a signal and a G signal from the second horizontal charge transfer unit HCCD2 is shown. Here, the switching switch 3
After reading the G ′ signal for one horizontal line period, the next 1
It is switched to read the G signal over the horizon. The read G'and G signals are recorded in the G channel of the magnetic disk 4.

FIG. 2B shows a process of reading the B signal from the first horizontal charge transfer unit HCCD1 and the R signal from the second horizontal charge transfer unit HCCD2. Similarly, when the switching switch 3 is switched, the B signal for one horizontal line is first read, and then the R signal for one horizontal line is read. The read B and R signals are recorded on the B / R channel of the magnetic disk 4.

FIG. 2 (c) schematically shows a magnetic disk device used for recording a signal. The magnetic disk device has two magnetic heads for two channels.

FIG. 3 shows a switching switch 5 for that purpose, which carries out channel switching. Further, FIG. 3 shows a schematic arrangement of the G track and the B / R track thus recorded. Since the G track and the B / R track are arranged in parallel, if these two tracks are read simultaneously by two magnetic heads, the G and B signals or the G'and R signals can be obtained at the same time. Therefore, by delaying the signal of the B / R channel by one horizontal line period, the G signal, the B signal and the R signal can be obtained at the same time. As a result, as usual, the Y signal,
RY and BY signals can be formed.

EFFECTS OF THE INVENTION According to the present invention, the signal of the first color is set to G which is the luminance main component.
In the case of a signal, the number of pixels can be maximized. Further, by alternately delaying the R signal and the B signal for each horizontal line during reading, a luminance signal and a color difference signal can be easily obtained. As a result, it is possible to provide an image with a very high resolution particularly in a sensory manner.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an image sensor used in carrying out the method of the present invention, and FIGS. 2 and 3 are diagrams for explaining the course of the method according to the present invention. 1 ... Transfer electrode, 2 ... Storage unit, 3,5 ... Switching switch, 4 ... Magnetic disk, R, B, G ... Photoelectric conversion unit, HCCD
1, HCCD2 ... Horizontal charge transfer section

Claims (1)

[Claims] 1. A photoelectric conversion part, a vertical charge transfer part independent of the photoelectric conversion part, and a first horizontal charge transfer part are provided.
In addition, a charge storage section and a second horizontal charge transfer section attached to this storage section are provided, and the vertical charge transfer section not only transfers the charge formed by the photoelectric conversion section,
It is also possible to perform photoelectric conversion by itself, form a signal of the first color (for example, G) of the three primary colors in the vertical charge transfer section, and use the remaining second and third of the three primary colors in the photoelectric conversion section.
In a method of reading a frame interline transfer type image sensor incorporated in a camera capable of blocking incident light by forming a signal of each color (for example, R and B), the shutter is opened and the shutter is opened during exposure. The signal charge of the first color formed in the vertical charge transfer unit is transferred at high speed to the storage unit, and then exposure is continued to form the first signal charge in the vertical charge transfer unit and the shutter is closed. , A signal charge of one first color from the vertical charge transfer unit via the first horizontal charge transfer unit, and a first charge of the other from the storage unit via the second horizontal charge transfer unit. Color signal charges are alternately read, then the second color signal charges are transferred from the photoelectric conversion unit to the vertical charge transfer unit, and the second color signal charges are transferred from the vertical charge transfer unit. The storage unit At a high speed, the signal charges of the third color are transferred from the photoelectric conversion unit to the vertical charge transfer unit, and are transferred from the vertical charge transfer unit to the third color through the first horizontal charge transfer unit. And the signal charges of the second color are alternately read from the storage section via the second horizontal charge transfer section.