JPH07115643A - On-vehicle image pickup device - Google Patents

Abstract

PURPOSE:To provide the on-vehicle image pickup device having a wide dynamic range to speedily and surely photograph an environment around a vehicle. CONSTITUTION:Light receiving elements 12 inside a CCD sensor 10 are divided into two groups, and the two groups are alternately arranged. The first group is a light receiving element group 12a to which no dark filter is attached, and the second group is a light receiving element group 12b to which the dark filter is attached. Therefore, even when the same quantity of light is made incident to the first and second groups, the quantity of received light is made different at the first and second groups and even when the quantity of incident light is more than the saturation level of the light receiving elements and an image signal from the first group is saturated, an image signal from the second group is outputted without being saturated. When it is decided that the quantity of incident light is considerably saturated, image processing is performed while storing only the image signal from the light receiving elements of the second group in a frame memory.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted image pickup device, and particularly to
The present invention relates to an imaging device having an improved dynamic range of a CD sensor.

[0002]

2. Description of the Related Art Conventionally, various devices have been developed and mounted for the purpose of improving the safety of vehicle traveling. The image capturing device captures an image of the surrounding environment of the vehicle to measure the distance between the preceding vehicle and the following vehicle. One of them is an alarm system that detects whether there is an obstacle or the like and notifies a dangerous state. When such an image pickup device is mounted on a vehicle, there is a wide dynamic range as a required specification. This is because the surrounding environment of the vehicle changes variously, and, for example, when entering a tunnel during the daytime, the amount of ambient light also widely changes accordingly. Therefore, it has been attempted to expand the dynamic range of the image pickup device.

For example, in the image input device disclosed in Japanese Patent Application Laid-Open No. 5-30424, a C having an electronic shutter function is used.
Use a CD area sensor and change the shutter time to 2
A technique is proposed in which a dynamic range is expanded by taking one image and combining these two images to create one image.

[0004]

However, in the technique for expanding the dynamic range by combining one image from two images in this way, the object to be photographed remains stationary within the time for obtaining the two images. It is premised on the fact that it can be regarded as moving or stationary, and there is a problem that it is not suitable for photographing the surrounding environment of a vehicle in which surrounding objects may move at high speed. In addition, since one image is composed from two images, it takes time to obtain a desired image, which is contrary to the request for quick image processing.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an in-vehicle image pickup device having a wide dynamic range capable of quickly and surely taking a picture of the surrounding environment of a vehicle. Especially.

[0006]

In order to achieve the above object, an on-vehicle image pickup device according to a first aspect of the present invention comprises a single CCD sensor composed of a plurality of light receiving elements arranged in a grid pattern, and this CCD sensor. In an image pickup apparatus including image processing means for processing an output image signal, the plurality of light receiving elements are composed of at least a first group and a second group having different light receiving amounts,
Determination of determining whether or not the image signal is saturated by comparing the image signal output from the light receiving element of the group having a large amount of received light among the first group and the second group with a predetermined saturation level And a control means for outputting to the image processing means only an image signal output from a light receiving element of a group having a small amount of received light when the determination means determines that the image sensor is saturated. To do.

In order to achieve the above object, the vehicle-mounted image pickup device according to a second aspect of the invention has a single CCD sensor including a plurality of light receiving elements arranged in a grid and an image output from the CCD sensor. In an image pickup apparatus including an image processing means for processing a signal, the plurality of light receiving elements are composed of at least a first group and a second group having different sensitivities, and a light receiving group of a high sensitivity of the first group and the second group is received. Determination means for determining whether or not the image signal is saturated by comparing the image signal output from the element and a predetermined saturation level,
And a control unit for outputting to the image processing unit only the image signal output from the light receiving element of the group having low sensitivity when the determination unit determines that the image sensor is saturated.

In order to achieve the above object, the vehicle-mounted image pickup device according to a third aspect is the vehicle-mounted image pickup device according to the first or second aspect, wherein the first group and the second group are alternately arranged. It is characterized by being arranged.

Further, in order to achieve the above object, the vehicle-mounted image pickup device according to a fourth aspect is the first or second aspect.
In the vehicle-mounted image pickup apparatus described above, the first group and the second group are arranged in a mosaic pattern.

[0010]

In the vehicle-mounted image pickup device according to the first aspect of the invention, the plurality of light receiving elements forming the CCD sensor are divided into at least a first group and a second group. Then, the amount of received light is made different in advance between the first group and the second group. As a means for varying the amount of received light, for example, a dark filter or the like may be attached to the light receiving element. In this way, the CCD sensor has at least two
By forming the two regions, the amounts of light received by the light receiving elements differ between the first group and the second group even when the same image is captured. Therefore, even if the surrounding environment of the vehicle is extremely bright and an excessive amount of light is incident on the light receiving element of the group that receives a large amount of light and the amount of received light is saturated, An appropriate amount of light will be incident. As a result, even when the light amount is very large, it is possible to obtain an image signal of an appropriate level that does not reach the saturation level, and it is possible to perform image processing using this image signal. On the other hand, when the environment around the vehicle is extremely dark, an image signal cannot be obtained from the light receiving element of the group receiving a small amount of light, but an image signal corresponding to the light amount of the surrounding environment is output from the light receiving element of a group receiving a large amount of light. The image signal can be processed using this image signal.

As described above, in the on-vehicle image pickup device according to the first aspect, the image signal from the group having a large amount of received light is used when the amount of light is small, and the amount of light is increased when the amount of light is greater than the saturation level. Since image processing can be performed using image signals from a small group, the dynamic range can be expanded.

Further, in the vehicle-mounted image pickup device according to the second aspect, the light-receiving elements having the same sensitivity characteristic are not used as in the vehicle-mounted image pickup device according to the first aspect, but the light-receiving elements having different sensitivity characteristics are previously provided. Used. First with different sensitivity
The light receiving elements of the second group and the second group output different image signals for the same light amount. Therefore, if the amount of light is equal to or higher than the saturation level of one group but equal to or lower than the saturation level of the other group, image processing can be performed using the image signal from this group.

Further, in the vehicle-mounted image pickup device according to the third aspect, the light receiving elements of the first group and the second group are alternately arranged in the CCD sensor. As described above, when the light amount is large, the saturation level is reached in the group having a large amount of received light or the group having a high sensitivity, and thus image processing is not performed using the image signal from this group. However, the first and second groups are CCD
By alternately arranging in the sensor, even if the image signal from one group is not used, the image signal from the other group can be processed to obtain an image in almost the entire effective area of the CCD sensor. An image of the surrounding environment can be reliably obtained.

Further, in the vehicle-mounted image pickup device according to the fourth aspect, the light receiving elements of the first group and the second group are arranged in a mosaic in the CCD sensor. By thus arranging in a mosaic pattern, even when one group reaches a saturation level and its image signal is not used for image processing when the amount of light is large, deterioration of the horizontal resolution of the CCD sensor is suppressed. While expanding the dynamic range.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of an in-vehicle image pickup device of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 shows the arrangement of a CCD sensor used in the image pickup apparatus of this embodiment. The CCD sensor 10 is configured to include a plurality of light receiving elements 12 arranged in a grid, a vertical shift register 14 and a horizontal shift register 16 for transferring the charges accumulated in these light receiving elements. Each light receiving element corresponds to one pixel of the screen. The charges accumulated in the light receiving element 12 are sequentially output to the vertical shift register 14, are further transferred from the vertical shift register 14 to the horizontal shift register 16, and are output as an image signal.

Here, the light receiving element 12 is divided into two groups, and the two groups are arranged alternately. The first group is a light receiving element group 12a without a dark filter, and the second group is a light receiving element group 12b with a dark filter.
In FIG. 1, the light receiving element with the dark filter is shown by the diagonal lines. The dark filter is, for example, an ND filter,
For example, the amount of transmitted light is about 50% over all wavelengths of incident light.
Restricted to. Therefore, even if the same amount of light is incident on the first group and the second group, the amount of received light differs between the first group and the second group, the incident light amount is equal to or higher than the saturation level of the light receiving element, and the image signal from the first group is received. , The image signal from the second group is output without being saturated.

FIG. 2 shows the arrangement of the image processing apparatus of the image pickup apparatus of this embodiment. Image signals sequentially output from the CCD sensor 10 shown in FIG. 1 are input to the A / D converter 24 and converted into digital signals. The image signal converted into a digital signal is input to and latched in the digital signal latch 26, and further stored in the frame memory 28 based on the control signal from the DMA controller 22. The image signal stored in the frame memory 28 is subjected to, for example, correlation calculation processing, and the distance to the object is detected.

On the other hand, the image signal from the CCD sensor 10 is input to the analog voltage comparator 20. Further, a predetermined saturation voltage and a transfer synchronization signal for controlling the transfer of charges of the CCD sensor 10 are input to the comparator 20. Of the image signals input using the transfer synchronization signal, the image signal from the light receiving element belonging to the first group is selected, and this image signal and the saturation voltage are compared in magnitude, and the image signal of the first group is saturated. Is determined. The comparison result of the analog voltage comparator 20 is input to the DMA controller 22. In the DMA controller 22, when the image signals from the first group of light receiving elements are below the saturation level, a control signal is supplied to the digital signal latch 26 and the frame memory 28 to store all the image signals in the frame memory 28. To do. If the image signal from the first group of light receiving elements is equal to or higher than the saturation level, the DMA controller 22 does not store the image signal from the first group of light receiving elements in the frame memory 28, and the second group of light receiving elements is not stored. The image signals from the same, that is, only the image signals that have not reached the saturation level are stored in the frame memory 28.
Therefore, the image processing performed using the image signal stored in the frame memory 28 is performed only with the image signal of an appropriate level that has not reached the saturation level, and the incident light amount of the vehicle surrounding environment is equal to or higher than the saturation level. Even if there is, image processing can be performed. When the amount of light around the vehicle is low, the image signal level from the light receiving element of the second group with the dark filter is low, but the image signal from the light receiving element of the first group without the dark filter is the amount of incident light. Since an image signal of an appropriate level according to is output, it is possible to perform image processing such as correlation calculation.

As described above, when the light quantity is below the saturation level, the image signal from the light receiving element of the first group (and the second group) is used, and when the light quantity is above the saturation level, the light receiving element of the second group is used. Since the image signal from can be used, the dynamic range of the image pickup device is significantly expanded. Further, since the light receiving elements of the first group and the second group are alternately arranged, it is not necessary to use a spectroscope for splitting the light path from the object into the first group and the second group, and the optical device can be used. It also has the effect of simplifying.

Second Embodiment FIG. 3 shows C used in the image pickup apparatus of the second embodiment of the present invention.
The configuration of the CD sensor 10 is shown. Similar to the first embodiment, the light receiving element is divided into a first group without a dark filter and a second group with a dark filter (light receiving elements shaded in the figure). The groups and the second group are arranged in a mosaic pattern. That is, the light receiving element with the dark filter and the light receiving element without the dark filter are alternately arranged in the vertical and horizontal directions. Therefore, this CCD sensor 1
From 0, the image signal from the first group and the image signal from the second group are alternately output. CCD sensor 10
The image signal output from is input to the analog voltage comparator 20 and the A / D converter 24 as in the first embodiment.
Then, the image signal from the first group is selected by the transfer synchronization signal, compared with the saturation voltage, and the comparison result is output to the DMA controller 22.

FIG. 4 shows a timing chart of this embodiment, FIG. 4 (a) is a timing chart of the transfer synchronization signal, and FIG. 4 (b) is an image from the first group and the second group. Shows the signal. The transfer synchronization signal is a periodic pulse in which Hi and Lo are repeated for each light receiving element, that is, for each pixel. Further, in this embodiment, since the light receiving elements of the first group and the second group are arranged in a mosaic pattern, the image signals of the first group and the second group are alternately output. Then, when the amount of incident light is a large amount of light equal to or higher than the saturation level, the image signal from the light receiving element of the first group becomes the saturation level as shown in FIG.
The image signal from the light receiving element of the second group has an unsaturated level. The DMA controller 22 stores only the image signal from the second group of light receiving elements in the frame memory 28.

As described above, in this embodiment, since the first group and the second group are arranged in a mosaic pattern, even when the incident light amount is above the saturation level and the image signal of the first group is not used,
Since the second group of light receiving elements can cover all the rows of the CCD sensor 10, it is possible to suppress deterioration of the horizontal resolution and reliably obtain image information of the object.

Third Embodiment FIG. 5 shows C used in the image pickup apparatus of the third embodiment of the present invention.
The configuration of the CD sensor 10 is shown. The first mentioned above,
In the second embodiment, the light receiving elements are divided into the first group and the second group, but in the present embodiment, the light receiving elements are divided into the first, second and third groups. The first group is a light receiving element group 12a to which no dark filter is attached, the second group is a light receiving element 12b with a dark filter that limits the transmitted light amount to 50% over all wavelengths of the incident light amount, and the third group Is, for example, 25%
It is a light receiving element 12c with a dark filter which is limited to. Therefore, even when the same amount of light enters the CCD sensor 10, image signals of three levels are output,
Even if the light receiving elements of the first group have reached the saturation level, the light receiving elements of the second group or the third group are not at the saturation level and can output an image signal of an appropriate level. These image signals output from the CCD sensor 10 are input to the analog voltage comparator 20 and the A / D converter 24 as in the first and second embodiments. Then, the image signals from the first group and the third group are selected by the transfer synchronization signal and compared with the saturation voltage, and the comparison result is D
Output to the MA controller 22. As a result of the comparison, when the image signal from the light receiving element of the first group is at the saturation level,
Further, it is determined whether or not the image signal from the light receiving element of the second group is at the saturation level. When the first group having a transmittance of 100% has reached the saturation level, but the second group having a transmittance of 50% has not reached the saturation level, the DMA controller 22 outputs the light from the light receiving elements of the second group and the third group. Only image signals are stored in the frame memory 28, and image processing is performed using these image signals.

In the first and second embodiments, the first group having a transmittance of 100% (that is, no dark filter) and the transmittance of 5 are used.
Only the 0% second group is provided. Therefore, for example, when the incident light amount is equal to or higher than the saturation level of the second group, further expansion of the dynamic range cannot be expected, but in this embodiment, the transmittance is further increased. Since 25% of the non-saturated image signals from the third group of light receiving elements can also be used, each group can process a light amount having a wider dynamic range, and image processing such as correlation calculation can be performed reliably. it can.

In each of the above-mentioned embodiments, the amount of light received is changed by attaching a dark filter, but since the composition is different, at least two types of light receiving elements having different sensitivities are used to form the first group and the second group. However, the same effect can be obtained even if the image signals of different levels are output even if the same amount of light is incident.

Further, for example, in the first embodiment, an electronic shutter is provided for each light receiving element row instead of the dark filter, and a different shutter speed is set for each row, so that a plurality of groups of light receiving elements having different light receiving amounts can be obtained. realizable. In this case, when the amount of incident light is equal to or less than the saturation level, it is possible to suppress an unnecessary decrease in resolution by setting the shutter speed of each column to be the same.

[0028]

As described above, according to the present invention,
It is possible to obtain an in-vehicle image pickup device having a wide dynamic range capable of quickly and surely taking a picture of the surrounding environment of the vehicle, and therefore an extremely reliable alarm system or the like can be obtained by using this image pickup device. .

[Brief description of drawings]

FIG. 1 is a configuration diagram of a CCD sensor according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an image processing apparatus of the same embodiment.

FIG. 3 is a configuration diagram of a CCD sensor according to a second embodiment of the present invention.

FIG. 4 is a timing chart of a transfer synchronization signal and an image signal of the embodiment.

FIG. 5 is a configuration diagram of a CCD sensor according to a third embodiment of the present invention.

[Explanation of symbols]

 10 CCD sensor 12 light receiving element 12a first group light receiving element 12b second group light receiving element 12c third group light receiving element 20 analog voltage comparator 22 DMA controller 24 A / D converter 26 digital signal latch 28 frame memory

Claims (4)

[Claims] 1. An image pickup apparatus comprising a single CCD sensor comprising a plurality of light receiving elements arranged in a grid pattern and an image processing means for processing an image signal output from the CCD sensor, wherein the plurality of light receiving elements are provided. Comparing an image signal output from the light receiving element of the first group and the second group having different light receiving amounts and having a large light receiving amount among the first group and the second group with a predetermined saturation level. According to the determining means for determining whether or not the image signal is saturated, only the image signal output from the light receiving element of the group having a small light receiving amount when the determining means determines that the image signal is saturated, An in-vehicle image pickup device comprising: a control unit that outputs to an image processing unit. 2. An image pickup apparatus comprising a single CCD sensor comprising a plurality of light receiving elements arranged in a grid and an image processing means for processing an image signal output from the CCD sensor, wherein the plurality of light receiving elements are provided. At least a first group and a second group having different sensitivities are included. By comparing an image signal output from a light receiving element of a group having a high sensitivity among the first group and the second group with a predetermined saturation level, Determining means for determining whether or not the image signal is saturated, and only the image signal output from the light receiving element of the group having low sensitivity when the determining means determines that the image signal is saturated, the image processing means A vehicle-mounted image pickup device, comprising: 3. The vehicle-mounted image pickup device according to claim 1 or 2, wherein the first group and the second group are alternately arranged. 4. The in-vehicle image pickup device according to claim 1 or 2, wherein the first group and the second group are arranged in a mosaic pattern.