Optical: systems and elements – Lens – Including a nonspherical surface
Reexamination Certificate
2000-03-27
2001-05-22
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
Including a nonspherical surface
C359S457000, C359S618000, C359S622000
Reexamination Certificate
active
06236520
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a device for picture recording with a lighting device, having a laser light source and an optical element illuminated by this laser light source for forming the laser light, and wherein the optical element is illuminated by a dispersing lens arranged between the laser light source and the optical element the preamble to patent claim
1
.
The invention is used with image sensors in the field of robotics, navigational systems and monitoring systems. A semiconductor laser, preferably expanded in one direction, is the preferred light source for such sensors. The camera used is preferably a charge-coupled device (CCD) camera with an electronically controlled shutter. Optical filters, installed in front of the camera objective, will filter out the light reflected by the illuminated object from the surrounding visible and infrared light, so that it is essentially the laser light that is processed into an image in the camera.
If a laser is used as a light source, the regulations for preventing accidents caused by laser radiation must be observed. Given the expanded radiation of the laser light and a wavelength of 750-850 nm, e.g., for a GaAs laser, these regulations only permit a laser output of 50-100 mW in order to stay within the maximum permissible radiation for laser light affecting the eye retina.
An arrangement for recording pictures is described in the German Unexamined Published Patent application No. P43 35 244. The laser output for this arrangement is distributed such that a point image of the laser light source cannot be formed with an optical system that is located in the illumination range, e.g., the human eye, if applicable with auxiliary means. This does not detract from the illumination characteristics of the lighting device, e.g. through generating a fan-shaped light bundle. In addition, the US 4 971 415 A and JP 60 193 140 disclose circular-arc type arrangements of several semiconductor lasers.
It is the object of the invention to provide a lighting device for recording pictures, which makes it possible to maintain the maximum permissible radiation for laser outputs exceeding 1 W over the total illumination range, has good spatial resolution characteristics and a high picture frequency, and can be produced with a compact design.
SUMMARY OF THE INVENTION
The above object generally is achieved according to the present invention by a lighting device for recording pictures, which comprises a laser light source and an optical element illuminated by the light source for forming the laser light, with the illumination of the optical element occurring via a dispersive lens that is arranged between the laser light source and the optical element; and wherein: the laser light source comprises several electrically serially connected lasers that are arranged in a circular arc shape such that the center point of the circular arc is located on the optical axis of the dispersive lens; the optical element is configured with several cylindrical lenses, with the cylindrical lens arranged on the side facing the laser light source being a converging lens, with converging lens being followed by additional cylindrical lenses, and with these cylindrical lenses have a plurality of tightly joined, planar microlenses on the side facing away from the laser. Advantageous embodiments and/or modifications additionally are described.
The invention has the advantage that by changing a point-shaped laser light source, into an expanded light source and by having a square light output surface for the lighting device, optimum conditions are created for the maximum permissible irradiation of the eye retina (see also IEC 825/1). In order to obtain an optimum illumination of a square surface area with a laser having a directional divergence, several individual lasers are arranged in a circular-arc shape, so that the laser light strikes a dispersing lens directly, without significant emission losses on the side, and is expanded in such a way that an optical element located at the output of the lighting device is illuminated to the maximum degree. It is furthermore advantageous if several individual lasers are connected in series, thereby generating the same laser light output (e.g., 0.8 W/A per laser), but with less electrical current. A further increase in the laser output of up to 200 W can be achieved with a pulsed operation of the laser light source and pulse lengths, ranging from a few nanoseconds up to several hundred nanoseconds. The pulse duty factor is approximately 1% and the number of pulses for a picture is between 1000 and 4000.
A further advantage of the invention is the shortest possible, low-inductance connection between the individual lasers and the connection between laser and laser driver for the lasers. Owing to the bond-wire connection of adjacent lasers and the use of ribbon-type conductors to connect the laser and the laser driver, a low-loss and interference-free connection is obtained within the lighting device.
The invention is described below with the aid of an exemplary embodiment and by referring to schematic drawings.
REFERENCES:
patent: 4971415 (1990-11-01), Hara et al.
patent: 5206761 (1993-04-01), Ogino
patent: 5631754 (1997-05-01), Jannson et al.
patent: 8902905 (1990-05-01), None
patent: 41 00 654 C2 (1992-07-01), None
patent: 43 35 244 A1 (1995-06-01), None
patent: 57-11247 (1982-07-01), None
patent: 60-193140 (1985-10-01), None
patent: 63-087780 (1988-04-01), None
Daimler-Chrysler AG
Kunitz Norman N.
Sugarman Scott J.
Thompson Timothy J
Venable
LandOfFree
Lighting device for picture recording does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lighting device for picture recording, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lighting device for picture recording will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2508300