JPH0580380B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device that supplements the visibility of areas that are difficult for vehicle occupants to see. The present invention relates to a vehicle visibility aid device that receives light from a CCD image sensor and projects an image on a display device based on a pixel-by-pixel imaging signal output from the CCD image sensor.

[Conventional technology]

First, CCD image sensor (hereinafter simply CCD
), the interline transfer method
To explain a CCD using an example, its basic structure is as shown in FIG. 4, for example.

This CCD 10 is constructed on a semiconductor substrate such as silicon, and its basic elements include:
a photosensitive section 11 arranged in a matrix, each having a photoelectric conversion element structure such as a photodiode;
A vertical register 12 that stores accumulated charges sent out at once from the 11 rows of photosensitive sections, and each vertical register 1
2, and a horizontal register 13 for storing charges outputted in parallel from 2 and serially outputting the charges as an image pickup signal Sv in units of pixels.
The transmission of accumulated charges from the photosensitive section 11 is synchronized with the transfer clock signal CLt, the transmission of charges from the vertical register 12 is synchronized with the vertical clock signal CLv, and the video signal of each pixel is transmitted from the horizontal register 13. The output of Sv is performed in synchronization with the horizontal clock signal CLh. That is, the rate relationship of each clock signal is such that for one clock of the transfer clock signal CLt, the vertical clock signal CLv is one clock of the photosensitive section 11.
In addition, the horizontal clock signal CLh is applied to the vertical register 12 for each vertical clock signal CLv (3 clocks in this case).
(in this case, 3 clocks). The period of the transfer clock signal CLt means the charge accumulation time in the photosensitive section 11.

In addition, in Fig. 4, the photosensitive section 11 has a 3x3 matrix configuration, but in an actual CCD, it has a 300x matrix configuration.
It has a matrix configuration of about 400.

Conventionally, so-called vehicle visibility aid devices have been considered, which are devices that image the driver's blind spot using an imaging device using a CCD as described above, and display the image on a display device such as a CRT display installed inside the vehicle. (Refer to Japanese Patent Application Laid-Open No. 180346/1983, etc.). This vehicle visibility aid device uses a CCD to receive light from the blind spot area, etc.
The structure is such that an image is displayed on a display device based on an imaging signal of each pixel corresponding to each photosensitive section 11 outputted from the photosensitive section 11.

[Problem that the invention seeks to solve]

Incidentally, in order to display scenes on the display device that are difficult for vehicle occupants to see at night, it is possible to use a vehicle visibility aid device such as the one described above. When background light such as light enters the CCD directly, even if the area to be checked is illuminated,
There is a problem in that objects in the area in the image displayed on the display device become difficult to see.

This is because conventional vehicle visibility aids do not take into account the background light mentioned above.
This is because images are displayed on the display device based on all the imaging signals output from the CCD.

Therefore, it is an object of the present invention to reduce the imaging signals from the CCD that contribute to the image displayed on the display device that correspond to the background light relative to the signals that correspond to the light from the predetermined area. The goal is to be able to do this.

[Means for solving problems]

The present invention allows light from a predetermined area to be transmitted to a vehicle.
This is based on a vehicle visibility aid device that receives light with a CCD image sensor and displays an image on a display device based on the image signal of each pixel output from the CCD image sensor. , the technical means for solving the above problem includes a light source device that intermittently irradiates the region in the predetermined direction with light at a predetermined period, and sends out accumulated charges from a photosensitive section in a CCD image sensor. The cycle is set to be shorter than the light irradiation cycle of the light source device, and each time the light source device emits light, the light is emitted after a predetermined period of time has elapsed from the light irradiation time.
The present invention is equipped with a prohibition means for prohibiting the imaging signal output from the CCD image sensor from contributing to the image displayed on the display device.

[Effect]

The light source device intermittently irradiates a region of the vehicle in a predetermined direction with light at a predetermined period. In the process,
A CCD image sensor receives reflected light and background light from an object in the area, and sequentially outputs imaging signals corresponding to the reflected light and background light. However, in this CCD image sensor, the cycle of transmitting the accumulated charge from the photosensitive part is set to the light source device described above. Since the light irradiation period is set to be shorter than the light irradiation period from , the accumulated charge is sent out from the photosensitive section a plurality of times for one light irradiation in the process of outputting the image pickup signal. Then, each time light is irradiated from the light source device, after a predetermined period of time has elapsed from the irradiation time,
The prohibiting means prohibits the imaging signal output from the CCD image sensor from contributing to the image displayed on the display device. Then, since the imaging signal output from the CCD image sensor immediately after the light irradiation includes a reflected light component from the target object, many of the other imaging signals correspond to background light. Most of the imaging signals whose contribution to the image is prohibited by the above-mentioned prohibition means correspond to background light. Therefore, among the imaging signals contributing to the image displayed on the display device, those corresponding to the background are reduced relative to those corresponding to the light from the predetermined area.

[Embodiments of the invention]

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing an example of a vehicle visibility aid device according to the present invention.

In the figure, reference numeral 10 denotes a CCD having a configuration similar to that shown in FIG. It is located in Reference numeral 20 denotes a lamp that irradiates light to the area in the predetermined direction, and can also serve as a headlamp when irradiating the area in front of the vehicle.

1 is a reference oscillation circuit that outputs a reference clock signal of a predetermined period. 2 performs predetermined frequency division processing on the reference clock signal from the reference oscillation circuit 1, and outputs a clock signal (light irradiation signal) with a period T ₀ of about 1/100 sec and a duty ratio of about 1/50. A light irradiation signal generation circuit 21 operates the lamp 2 based on a clock signal from the light irradiation signal generation circuit 2.
The lamp 20 is designed to intermittently emit light in synchronization with the clock signal.

Reference numerals 3, 4, and 5 designate a transfer clock generation circuit, a horizontal clock generation circuit, and a vertical clock generation circuit for outputting a transfer clock signal CLt, a horizontal clock signal CLh, and a vertical clock signal CLv to the CCD 10, respectively. Then, each clock generation circuit 3, 4,
5 creates a clock signal with a predetermined period based on the reference clock signal from the reference oscillation circuit 1, and in particular, the period Tt of the transfer clock signal CLt from the transfer clock generation circuit 3 is determined by the light irradiation signal generation circuit 2. Furthermore, the periods Th and Tv of the horizontal clock signal CLh and vertical clock signal CLv are set to approximately 1/50 of the clock signal period _T0 from the transfer clock signal CLt and the above-mentioned CCD.
These are set based on the rate relationship of each clock signal in 10.

6 is a monostable multivibrator (hereinafter simply referred to as
MM), and the predetermined time Tg set in this MM6 is the period Tt of the transfer clock signal CLt.
It is slightly longer. Reference numeral 7 denotes a gate circuit, and this gate circuit 7 has a function of sending the image pickup signal Sv from the CCD 10 to the subsequent stage when the output of the MM 6 is at H level.

15 performs a predetermined frequency division process on the reference clock signal from the reference oscillation circuit 1 to obtain a predetermined period Ts.
A video clock signal generation circuit 16 that outputs a video clock signal of 16 stores the imaging signal via the gate circuit 7, and outputs the accumulated imaging signal to the subsequent stage every time the clock signal from the video clock signal generation circuit 15 rises. This is an image pickup signal storage circuit. 17 is a video signal generation circuit that creates a video signal based on the imaging signals sequentially output from the imaging signal storage circuit 16; 18 is a display device installed at an appropriate position in the vehicle; An image based on a video signal from the signal generation circuit 17 is displayed.

Next, the operation of the above device will be explained based on the timing chart shown in FIG.

The lamp 20 intermittently irradiates a region of the vehicle in a predetermined direction with light at a period T ₀ . Note that this irradiated light repeatedly decreases and decreases at a frequency of about 100 Hz (T ₀ is about 1/100 sec), so it appears to the human eye as continuous light. During this process, the CCD 10 receives reflected light and background light from the object in the area, and sequentially outputs image signals Sv corresponding to the reflected light and background light.

Furthermore, if we look at the operation of CCD10 in detail,
Since the relationship between the light irradiation period T ₀ of the lamp 20 and the transfer clock period Tt of the CCD 10 is approximately T ₀ =50·Tt, the light-sensitive section 11 of the CCD 10 for one irradiation of the lamp 20
repeats charge accumulation and transmission of the accumulated charge about 50 times. As the accumulated charges are sent out, the accumulated charges move in synchronization with the vertical clock signal CLv and the horizontal clock signal CLh, and the CCD 10 sequentially outputs image signals Sv in units of pixels. here,
Immediately after the lamp 20 irradiates light once, charges corresponding to the reflected light from the object in the area and the background light are accumulated in the photosensitive section 11 of the CCD 10,
Upon application of the transfer clock CLt, the accumulated charges are sent out at once from the photosensitive section 11. From then on,
Since the charge accumulated in the photosensitive section 11 of the CCD 10 corresponds to the background light until the next light irradiation, each clock signal of the transfer clock signal CLt, vertical clock signal CLv, and horizontal clock signal CLh The imaging signal Sv output from the CCD 10 by the synchronized operation based on the above corresponds to the background light. Therefore, when light is intermittently irradiated from the lamp 20 at a period T ₀ as described above, the imaging signal Sv outputted from the CCD 10 at that time is a signal from the target object only immediately after the light irradiation. It will contain components corresponding to reflected light, and from now on,
Until the next light irradiation, it corresponds to the background light (see the waveform of the imaging signal Sv in FIG. 2).

On the other hand, the output of the MM6 is at the H level for a predetermined time Tg from the light irradiation time every time the lamp 20 is irradiated with light, and the predetermined time Tg is the transfer clock period.
Since it is set to be slightly longer than Tt, the imaging signal Sv from the CCD 10 that passes through the gate circuit 7 is only the one immediately after the light irradiation. Therefore, the imaging signal storage circuit 16 receives the CCD 10 immediately after the light irradiation.
The imaging signals output from are accumulated. and,
This accumulated imaging signal is synchronized with the clock signal from the video clock signal generation circuit 15 at a predetermined period.
The signal is transferred to the video signal generation circuit 17 at every Tg, and after being converted into a predetermined video signal, an image based on the video signal is displayed on the display device 18.

In the vehicle visibility aid device of this embodiment, the CCD 10 immediately after the lamp 20 emits light.
Only the imaging signal Sv output from the , that is, the imaging signal containing a component corresponding to the reflected light from the target object contributes to the image displayed on the display device 18, and other imaging signals, that is, the background light Since most of the corresponding imaging signals no longer contribute to the image, a clearer image of the target object is obtained on the display device 18.

Note that the amount of charge accumulated in each photosensitive section 11 of the CCD 10 is proportional to (intensity of incident light) x (accumulation time), so in order to obtain a clearer image, In addition to increasing the intensity of the irradiated light, the accumulation time in each photosensitive section 11 of the CCD 10, that is, the transfer clock period Tt, is shortened, and the setting time Tg of the MM6 is also shortened accordingly. . As a result, in the imaging signal output from the CCD 10 immediately after the light irradiation from the lamp 20, the component corresponding to the background light is reduced by the shorter accumulation time, and the component corresponding to the reflected light from the target object is reduced. The reduction in this component is compensated for by increasing the amount of irradiated light. In particular, if strong light such as the headlights of an oncoming vehicle is assumed as background light, the charge accumulated in the photosensitive section 11 will normally exceed the allowable amount of the CCD 10, and there is a risk that blooming will occur in the resulting image. Therefore, in order to prevent this, it is necessary to further shorten the transfer clock period Tt.

FIG. 3 is a diagram showing measures to further reduce the influence of background light.

This is characterized in that a light shutter 30 composed of PLZT, BSO, liquid crystal, etc. is arranged in front of the CCD 10, and a drive circuit 31 switches the light shutter 30 in synchronization with the irradiation timing of the lamp 20 mentioned above.
This is used to switch between a transparent state and a non-transparent state.
As a result, the CCD 10 enters the light receiving state only when light is irradiated from the lamp 20. Therefore,
The reflected light from the object illuminated by the lamp 20 passes through the light shutter 30 as is, while the continuous background light is reduced by the operation of the light shutter 30.

In addition, in FIG. 3, 32 is a photomultiplier tube, 33,
34 is a condensing lens.

〔Effect of the invention〕

As described above, according to the present invention, regarding the imaging signals from the CCD that contribute to the image displayed on the display device, one that corresponds to the background light and one that corresponds to the reflected light from the object in the predetermined area. Therefore, it is possible to realize a vehicle visibility aid device that can more clearly project scenes in areas that are harder to see at night by eliminating the effects of background light. .

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of the vehicle visibility aid device according to the present invention, Fig. 2 is a timing chart showing the status of each part signal in Fig. 1, and Fig. 3 is a diagram showing the status of each part signal in Fig. 1. FIG. 4 is a diagram showing the basic structure of an interline transfer type CCD image sensor. 1...Reference oscillation circuit, 2...Light irradiation signal generation circuit, 3...Transfer clock generation circuit, 4...Horizontal clock generation circuit, 5...Vertical clock generation circuit,
6... Monostable multivibrator (MM), 7...
... Gate circuit, 10 ... CCD image sensor (CCD), 11 ... Photosensitive section, 12 ... Vertical register, 13 ... Horizontal register, 16 ... Imaging signal storage circuit, 18 ... Display device, 20 ... lamp,
21...Drive circuit.

Claims (1)

[Claims] 1 CCD captures light from a predetermined direction area relative to the vehicle
In a vehicle visibility aid device that receives light with an image sensor and projects an image on a display device based on an imaging signal for each pixel output from the CCD image sensor, light is emitted at a predetermined period to an area in the predetermined direction. The light source device is equipped with a light source device that emits light intermittently, and the cycle for transmitting accumulated charges from the photosensitive section in the CCD image sensor is set to be shorter than the light irradiation cycle of the light source device, so that each time the light source device emits light, A visibility aid device for a vehicle, comprising a prohibition means for prohibiting an imaging signal output from a CCD image sensor from contributing to an image displayed on a display device after a predetermined period of time has elapsed from the light irradiation time.