Abstract: A method and apparatus for detecting the presence of artificial illumination in a scene powered by alternating current by sampling the light in a scene at a periodic rate.

Abstract: A camera adjusts its strobe energy to achieve proper exposure of a photograph. The adjustment method uses two trial exposures of the scene to be photographed. One trial exposure is taken without the camera strobe using only ambient illumination. The other trial exposure is taken using the camera strobe at a pre-set energy level. Pixels that appear as saturated in the ambient-only trial exposure are discounted in the determination of the strobe energy for the final photograph. This method properly exposes scenes which themselves contain bright light sources such as lamps or light fixtures.

Abstract: A camera adjusts its strobe energy to achieve proper exposure of a photograph. The adjustment method uses two trial exposures of the scene to be photographed. One trial exposure is taken without the camera strobe using only ambient illumination. The other trial exposure is taken using the camera strobe at a pre-set energy level. Pixels that appear as saturated in the ambient-only trial exposure are discounted in the determination of the strobe energy for the final photograph. This method properly exposes scenes which themselves contain bright light sources such as lamps or light fixtures.

Abstract: A method and device for improving the generation of the focus signal in the auto-focus system of a camera.

Abstract: An imaging device includes a lens system with a plurality of lenses, and a zoom and focus controller. The lenses include a zoom lens and a focusing lens. The zoom and focus controller controls the positions of the zoom lens and the focusing lens. The zoom and focus controller includes a plurality of focusing curves including a zoom curve and an infinity focusing curve. The zoom and focus controller is responsive to a zoom operation by determining a zoom position of the plurality of lenses, adjusting the focusing lens along the infinity focusing curve for the determined zoom position, and offsetting the focusing lens according to a difference between an actual focusing distance and an infinity focusing distance.

Abstract: A focus lens and a zoom lens group having a first zoom lens and a second zoom lens are controlled separately from one another in an internal-focus camera. The positions of the focus lens and the second zoom lens in the zoom lens group are tracked, and are controlled to approach no closer to one another than a minimum safe distance to avert collisions between the focus lens and the second zoom lens.

Abstract: An imaging device includes an image lens, an image sensor, and a brightness control element. The imaging device receives an image through the image lens in the optical pathway and detects the image at the image sensor. Brightness of the light impinging on the image sensor is adjusted using the brightness control element. In one automatic focus technique, the brightness control element controls luminous flux diameter. In another automatic focus technique, the brightness control element controls light transmittance without changing the luminous flux diameter. During detection of the auto-focus (AF) signal for a bright image, a brightness controller leaves the luminous flux diameter open and inserts a neutral-density (ND) filter into the optical path to avoid saturation of the signal from the image sensor. When the neutral density filter is inserted, an auto-focus controller moves the focusing lens to the best focus position independent of the auto-focus (AF) and an automatic-exposure (AE) signals.

Abstract: An optical disk drive system having a means for detecting off-track conditions with high reliability under conditions causing the objective lens to deviate from optimal focus, such as in the presence of external mechanical shocks. As the lens travels out of focus, the ability to resolve features decreases due to the lose of image contrast, causing a loss of tracking error signal (TES) gain. A digital signal processor (DSP) compensates for this loss by continuously determining an adjustable TES threshold representing the same desired percentage off track and same percentage of TES amplitude. A straight line approximation of this ideal adjustable threshold is used as a threshold to determine if the beam is within the desired amount off track. Alternatively, the DSP amplifies the TES by an amplification function to maintain the TES at a constant value while the objective lens travels out of focus. The TES amplification function is a straight line approximation of an ideal amplification function.

Abstract: An optical disk drive system having a means for detecting off-track conditions with high reliability under conditions causing the objective lens to deviate from optimal focus, such as in the presence of external mechanical shocks. As the lens travels out of focus, the ability to resolve features decreases due to the loss of image contrast, causing a loss of tracking error signal (TES) gain. A digital signal processor (DSP) compensates for this loss by continuously determining an adjustable TES threshold representing the same desired percentage off track and same percentage of TES amplitude. A straight line approximation of this ideal adjustable threshold is used as a threshold to determine if the beam is within the desired amount off track. Alternatively, the DSP amplifies the TES by an amplification function to maintain the TES at a constant value while the objective lens travels out of focus. The TES amplification function is a straight line approximation of an ideal amplification function.

Abstract: An apparatus for attenuating optical crosstalk induced components of a focus error signal in an optical disk drive of the type having a grooved optical disk with servo tracks and tracking and focus servo systems controlled by a digital signal processor. A calibration operation is performed whenever a new disk is inserted into the track. During the calibration operation, the disk is scanned about a tracking axis at a track crossing frequency greater than the focus servo system bandwidth. The focus error signals produced when the disk is scanned are filtered about a pass band including the track crossing frequency. Crosstalk values equal to values of the filtered focus error signals are determined as a function of corresponding values of the tracking error signals, and are stored in memory. A correction operation is performed while reading and writing data on the disk.

Abstract: A method for obtaining focus capture in an optical disk drive having a focus servo system with a servo loop and operable in open and closed loop modes, including: opening the servo loop and operating the servo system in the open-loop mode; scanning an objective lens about a focus axis with respect to an optical disk at a calibration velocity; peak detecting focus error signals produced while the lens is scanned at the calibration velocity to determine a peak focus error signal value; storing a calibration threshold value as a function of the peak focus error signal value; scanning the objective lens about the focus axis at a focus capture velocity; comparing the focus error signal values produced while the lens is scanned at the focus capture velocity to the calibration threshold value; and closing the servo loop and operating the focus servo system in the closed-loop mode when the focus error signal values reach the calibration threshold value.

Abstract: A method for operating a programmable digital signal processor in an optical disk drive to compensate tracking and/or focus servo system gain each time a new disk is inserted. The digital signal processor receives a servo error signal and outputs a servo control signal. Data characteristic of a desired servo system gain at a predetermined test frequency is stored in memory. The digital signal processor generates a test signal at the test frequency and sums the test signal with the servo error signal. Servo system gain at the test frequency is determined by computing the ratio of the amplitude of the servo error signal before it is summed with the test signal and the amplitude of the summed servo error signal and test signal. A corrected gain factor is computed as a function of the current servo system gain, the desired servo system gain and current gain factor. The corrected gain factor is stored in memory.

Abstract: A system and method for maintaining focus of a laser beam on the surface of an erasable magneto-optic disk during erase operations is disclosed. The laser beam exhibits beam farfield shift during erase operations, complicating the maintenance of optimal focus. An optical detector is exposed to laser light reflected to the disk to generate signals governing operation of a focusing lens' servo system. A digital signal processor is included in the servo system and is programmed to compensate for beam farfield shift by generation of an offset correction signal during periods of erase power operation. The offset correction signal is generated by the digital signal processor by comparison of optical detector output signals generated during operation of the laser source where no beam farfield shift occurs and the output signals generated where beam farfield shift is occurring, but the system is known to be in focus.

Abstract: An optical disk recording system including a record medium is disclosed for providing an accurate track crossing count and an accurate track following signal. A first embodiment utilizes off-centered wobbled areas located in the headers of the record medium. The high frequency content of a first signal is combined with the low frequency content of a second signal, which is generated using the wobbled areas. In another embodiment, light-reflective discontinuities are provided in the header areas of the record medium. A qualifier and an AGC are utilized in providing a corrected track following signal. In still another embodiment, reflective discontinuities are located in the servo areas of the record medium. In such an embodiment, it is preferred that there is a fixed gain adjustment to a radial push-pull signal.

Abstract: An objective lens velocity control system for use in an optical data storage system. The optical data storage system includes an optical disk with servo tracks for storing data, an objective lens, and a tracking drive for driving the objective lens along the tracking axis in response to tracking drive signals. The tracking error detector is responsive to the objective lens and produces tracking error signals representative of the position of the objective lens along the tacking axis. The tracking error signal also defines measurement periods which are representative of an actual velocity of the objective lens. A velocity control is responsive to the tracking error detector and produces the tracking drive signals in a form tending to cause the objective lens to have a desired velocity. For each measurement period, the tracking control produces a first tracking drive signal during a first portion but for no longer than a time duration which is a function of the desired velocity.