Apparatus and process for improving visibility of object within visual field

• US 4,692,798 A
• Filed: 01/07/1985
• Issued: 09/08/1987
• Est. Priority Date: 01/09/1984
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Seko, Yasutoshi, Abe, Yuichi
• Primary Examiner(s): Britton, Howard W.
• Assistant Examiner(s): Peng, John K.
• Time in patent office: 974 Days
• Field of Search: 340/50, 340/81 R, 340/84, 340/902, 340/904, 358/93, 358/108, 358/213, 358/228, 362/61, 362/64, 362/321, 356/23-26, 252/582, 350/330, 350/331 R
• US Class Current: 348/118
• CPC Class Codes: B60Q 1/14 having dimming means lighting power supply circuits in general H05B
• CPC Class Codes: B60R 1/00 Optical viewing arrangements house mirrors and spies A47G1/00; antiglare equipment, e.g. polarising, for windscreens or windows B60J3/00; visual aids for tractors B62D49/0614; devices per se G02B
• CPC Class Codes: B60R 2300/106 using night vision cameras
• CPC Class Codes: B60R 2300/8053 for bad weather conditions or night vision
• CPC Class Codes: H04N 5/2354 by influencing the scene brightness using illuminating means H04N5/2352 takes precedence
• CPC Class Codes: H04N 5/238 by influencing the optical part of the camera, e.g. diaphragm, intensifier, fibre bundle H04N5/2352 takes precedence

Abstract

An apparatus for improving the visibility of objects within the visual field of a vehicle driver and a process therefor are disclosed. The apparatus includes a light caster casting intense visible light toward a reflective object at a frequency no lower than critical fusion frequency, an image pickup device picking up an image of the object and outputting corresponding image data, an image data amplifier, a picture signal generator and a display. The image data are processed to yield a picture signal which yields a clear picture of the object on the display. The apparatus can give the driver of a vehicle a clear picture of the objects within forward visual field of the vehicle at night without dazzling the drivers of vehicles in the opposite lane.

Claims

1. An apparatus comprising:

means for casting visible light toward a reflective object at a frequency of no less than the critical fusion frequency;

means for picking up an image of the object and outputting image data in accordance with the picked-up image;

a light-intensity sensor monitoring the intensity of a light incident on said image pickup means and outputting a signal representing the level of the intensity of the incident light;

an optical shutter of liquid crystal filtering the incident light;

a light-intensity control circuit opening and shutting said optical shutter in accordance with the frequency of the casting of the visible light and controlling a duty cycle of said optical shutter in response to a level of said signal so as to control an effective transmissivity of said optical shutter;

means for generating a picture signal in accordance with the image data; and

means for displaying a picture of the object in response to the picture signal.

2. An apparatus as recited in claim 1, wherein said light casting means includes means for generating a flashing visible light.

3. An apparatus as recited in claim 1, wherein said display means is a raster scan-type cathode ray tube.

4. An apparatus as recited in claim 1, wherein the light-intensity control circuit includes a circuit categorizing the level of light intensity among a plurality of levels and a plurality of one-shot multivibrators which output pulses with unique widths monotonically related to the categorized light intensity, the output pulse serving to control the open period of the optical shutter.

5. An apparatus as recited in claim 1, wherein the light-intensity control circuit includes a circuit for dividing an output range of the level of light intensity among a plurality of levels and a circuit adjusting the transmissivity of the liquid crystal shutter in response to the output of the level-dividing circuit.

6. An apparatus as recited in claim 1, wherein the liquid crystal shutter is of the field-effect type.

7. An apparatus as recited in claim 1, further comprising an optical shutter for said image pickup means driven to open synchronously with the intervals of transmission of visible light and wherein said visible light casting means casts visible light stroboscopically at said frequency.

8. An apparatus as recited in claim 1, wherein said image pickup means comprises a solid state image sensor which includes a photoelectronic device.

9. An apparatus as recited in claim 8, wherein the photoelectronic device has an amplified output.

10. An apparatus as recited in claim 9, wherein the solid state image sensor is a CCD image sensor.

11. An apparatus as recited in claim 9, wherein the photoelectronic device is a phototransistor.

12. A process comprising the steps of:

casting visible light toward a reflective object at a frequency no less than the critical fusion frequency;

picking up an image of the object;

outputting image data in accordance with the image;

monitoring the intensity of an incident light in said image pickup step and outputting a signal representing the level of the intensity of the incident light;

filtering the incident light by means of an optical shutter;

opening and shutting the optical shutter in accordance with the frequency of the casting of visible light and controlling the duty cycle of said optical shutter in response to a level of said signal so as to control an effective transmissivity of said optical shutter;

generating a picture signal in accordance with the image data; and

displaying a picture of the object in response to the picture signal.

13. An apparatus for improving the visibility of an object within a visual field of a vehicle comprising:

a light caster casting visible light toward a reflective object within the visual field stroboscopically at a frequency no less than critical fusion frequency;

means for picking up an image of the object and outputting image data;

a light intensity sensor sensing the intensity of a light incident on said image pickup means and for outputting a signal representing the level of the intensity of the incident light;

an optical shutter for said image pickup means driven to open synchronously with the intervals of transmission of the strobed visible light;

a light-intensity control circuit driving said optical shutter and controlling the duty cycle of said optical shutter in response to a level of said signal so as to control an effective transmissivity of said optical shutter;

a picture signal generator outputting a picture signal in accordance with the image data; and

a display presenting a picture of the object in response to the picture signal.

14. An apparatus as recited in claim 13, wherein the optical shutter is divided into a plurality of elements arranged laterally across the vehicle.

15. An apparatus comprising:

means for casting visible light toward a reflective object at a frequency no less than the critical fusion frequency;

means for picking up an image of the object and outputting image data in accordance with the picked-up image;

a light intensity sensor monitoring the intensity of a light incident on said image pickup means and outputting a signal representing the level of the intensity of the incident light;

an optical shutter of a field-effect type liquid crystal filtering the incident light;

a light-intensity control circuit analogically controlling a drive voltage of the field-effect type liquid crystal in response to a level of said signal so as to control an instantaneous transmissivity of said optical shutter;

means for generating a picture signal in accordance with the image data; and

means for displaying a picture of the object in response to the picture signal.

16. An apparatus as recited in claim 15, wherein said light-intensity control circuit includes a circuit for dividing an output range of the level of light intensity among a plurality of levels and a circuit analogically controlling the drive voltage of the field-effect type liquid crystal in response to an output of the level-dividing circuit.