High frequency, low power light source for video camera

• US 5,010,412 A
• Filed: 12/27/1988
• Issued: 04/23/1991
• Est. Priority Date: 12/27/1988
• Status: Expired due to Term

• Current Assignee: Olympus Medical Systems Corporation (Olympus Corporation)
• Original Assignee: The Boeing Co.
• Inventors: Garriss, Gregory M.
• Primary Examiner(s): Peng, John K.
• Application Number:
  US07/290,581
• Time in Patent Office: 847 Days
• Field of Search: 358/107, 358/125, 358/212, 358/240, 358/241, 358/100, 356/23, 362/3, 362/11, 362/800, 354/129, 354/132, 354/140, 354/414
• US Class Current: 348/371
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]

Abstract

A strobe light provides uniformly intense, monochromatic illumination of an object photographed by a video camera. The strobe light includes a circuit board having a central aperture and a plurality of light-emitting diodes mounted on the circuit board and generally surrounding the aperture. The circuit board is attached to the camera with the aperture positioned in front of the camera lens such that the video camera views the object through the aperture as the diodes illuminate the object. The strobe light further includes an oscillator providing an output square wave signal of adjustable frequency and duty cycle. A transistor switch controlled by the square wave signal periodically connects a constant voltage across the diodes, thereby causing the diodes simultaneously to generate flashes of light with a frequency and duty cycle determined by the square wave signal.

Claims

1. A light source for providing illumination of an object, said light source comprising:

a diode for emitting light when energized;

means for periodically energizing said diode with an adjustable frequency and duty cycle such that said diode emits a sequence of light flashes illuminating said object; and

enabling means for selectively enabling and disabling said means for periodically energizing said diode, said enabling means being operatively responsive to a synchronization signal.

2. A light source for providing illumination of an object, said light source comprising:

a diode for emitting light when energized; and

means for periodically energizing said diode with an adjustable frequency and duty cycle such that said diode emits a sequence of light flashes illuminating said object;

wherein said means for periodically energizing said diode comprises oscillator means for providing an oscillating output signal of adjustable frequency and duty cycle with the frequency being adjusted in accordance with a magnitude of an input frequency control value and the duty cycle being adjusted in accordance with the magnitude of an input duty cycle control value, means for generating a constant supply voltage, and switch means operated by said oscillating signal for periodically coupling said supply voltage to said diode with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal, said supply voltage energizing said diode such that said diode emits said light flashes.

3. A light source for providing monochromatic illumination of an object photographed by a camera acquiring an image of the object through a lens, the light source comprising:

a plurality of diodes for emitting light when energized;

means for attaching said diodes to said camera with said diodes arranged about said lens and directed for illuminating said object, and

means for periodically energizing said diodes.

4. The apparatus in accordance with claim 3 wherein said camera is adapted to produce a synchronizing signal substantially concurrent with operation thereof, and including means controlling said energizing means and responsive to said synchronizing signal for energizing said diode when said camera is acquiring an image.

5. The apparatus in accordance with claim 3 wherein said means for energizing said diodes comprises:

oscillator means for providing an oscillating output signal of predetermined frequency and duty cycle;

means for providing a supply voltage;

switch means operated by said oscillating signal for periodically coupling said supply voltage to said diodes with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal, said supply energizing said diodes such that said diodes concurrently and periodically illuminate said object.

6. A strobe light for providing uniformly intense, monochromatic illumination of an object photographed by a video camera acquiring a sequence of images of the object through a lens and asserting a synchronizing signal indicating when it is acquiring an image, the strobe light comprising:

a plurality of diodes mounted on the video camera generally surrounding the lens, the diodes generating light of similar wavelength when energized by a supply source, the intensity of light generated by the diodes being determined by a voltage magnitude of said supply source;

oscillator means responsive to said synchronizing signal for providing an output of adjustable frequency and duty cycle when said synchronizing signal indicates said video camera is acquiring an image, the frequency being adjusted in accordance with a magnitude of an input frequency control value, and the duty cycle being adjusted in accordance with the magnitude of an input duty cycle control value;

means providing a supply source for energizing said diodes; and

switch means operated by said oscillating signal for periodically coupling said supply source to said diodes with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal to cause diodes simultaneously to generate pulses of light.

7. A strobe light for providing uniformly intense, monochromatic illumination of an object photographed by a video camera acquiring a sequence of images of the object, the video camera generating a synchronizing signal indicating when it is acquiring an image, the strobe light comprising:

a support having an aperture;

a plurality of diodes mounted on said support and generally surrounding the aperture in a pattern providing substantially uniform illumination of the object when said support is in juxtaposition with said object, the diodes generating light of similar wavelength when energized by a supply signal, the intensity of light generated by the diodes being determined by a voltage magnitude of the supply signal;

means for attaching said support to the camera such that the video camera views the object through the aperture as said diodes illuminate said object;

oscillator means responsive to said synchronizing signal for providing an oscillating output signal of adjustable frequency and duty cycle when said synchronizing signal indicates said video camera is acquiring an image, the frequency being adjusted in accordance with a magnitude of an input frequency control value, and the duty cycle being adjusted in accordance with the magnitude of an input duty cycle control value;

a voltage source for generating an output voltage signal;

means for regulating said output voltage signal to produce a said supply signal of substantially constant voltage;

switch means operated by said oscillating signal for periodically applying said supply signal to said diodes with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal, said supply signal causing said diodes to generate light simultaneously;

first means responsive to user input for generating said frequency control value; and

second means responsive to user input for generating said duty cycle control value.

8. An apparatus for photographing an object, comprising;

a camera for acquiring an image of the object through a lens when said object is illuminated;

a plurality of diodes for emitting light when energized;

means for attaching said diodes to said camera with said diodes substantially uniformly distributed about said lens, such that when energized, said diodes illuminate said object with substantially uniform light intensity; and

means for concurrently energizing said diodes.

9. The apparatus in accordance with claim 8 wherein said means for concurrently energizing said diodes comprises:

oscillator means for providing an oscillating output signal of adjustable frequency and duty cycle, the frequency being adjusted in accordance with a magnitude of an input frequency control value, and the duty cycle being adjusted in accordance with the magnitude of an input duty cycle control value;

means for generating a constant voltage supply signal; and

switch means operated by said oscillating signal for periodically coupling said supply signal to said diodes with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal, said supply signal energizing said diodes such that said diodes concurrently emit light.

10. Tho apparatus in accordance with claim 8 wherein said camera comprises a video camera including means for generating a synchronizing signal wherein said means for concurrently energizing said diodes comprises:

oscillator means responsive to said synchronizing signal for providing an output signal when said synchronizing signal indicates said video camera is acquiring said image;

means for generating a constant voltage supply; and

switch means operated by said oscillating signal for periodically coupling said supply to said diodes with a frequency and duty cycle determined by the frequency and duty cycle of the oscillator output signal.

11. A method for illuminating an object photographed by a camera acquiring an image of the object through a lens, the method comprising the steps of:

generally surrounding said lens with a plurality of diodes that emit light when energized such that said light illuminates said object; and

periodically energizing said diodes.

12. A method for providing monochromatic stroboscopic illumination of an object photographed by a video camera acquiring a sequence of images of the object through a lens, the video camera generating a synchronizing signal indicating image acquisition, the method comprising the steps of:

generally surrounding said lens with a plurality of diodes that emit light when energized by a supply signal, said diodes being positioned such that their emitted light illuminates said object, the intensity of light generated by the diodes being determined by a voltages magnitude of the supply signal;

providing an oscillating output signal of predetermined frequency and duty cycle when said synchronizing signal indicates said video camera is acquiring an image; and

applying said supply signal to said diodes in response to said oscillating output signal with a frequency and duty cycle determined by the frequency and duty cycle of the oscillating output signal, said supply signal causing said diodes to generate pulses of light.

13. A light source for providing illumination of an object, said light source comprising:

a diode for emitting light when energized;

means for periodically energizing said diode such that said diode emits a sequence of light flashes illuminating said object; and

enabling means for selectively enabling and disabling said means for periodically energizing said diode, said enabling means being operatively responsive to a camera synchronization signal.