This invention relates to optoelectronic transceivers used in optical communication systems, and more specifically to an optical transceiver configured for transmission and reception of infrared optical signals within an asymmetrically shaped optical profile.
Some previous optical transceivers used optical profiles that were uniform or broad. Some previous transceivers used narrow optical profiles by using emitter and receiver lenses oriented in different angles aimed in different directions in relation to each other to reduce optical signal interference to improve communication. However, this increased manufacturing costs and the size of the transceiver package, as well as limiting utility.
The Infrared Data Association (IrDA) published a standard titled Infrared Data Association Serial Infrared Physical Layer Specification (V1.3, Oct. 15, 1998) which contained the Advanced Infrared (AIr) communications standard. This standard defines a physical link layer protocol having infrared (IR) detectors, such as a photodetector for detecting received infrared light, and an emitter, such as a light emitting diode (LED) for emitting light up to a transfer rate of 4 Mb/s within a predetermined asymetrically-shaped optical profile having orthogonal minor and major axes with concentric centres. Along the major axis, the half power level of the profile shape is located at the outward edges of a cone which subtends an angle of 60 degrees that straddles a line normal to the major axis, and along the minor axis, the half power level of the profile shape is located at the outward edges of a cone which subtends an angle of 15 degrees that straddles a line normal to the minor axis. The shape of the optical profile is designed to maximize the xe2x80x98reach spacexe2x80x99 along a direction orthogonal to the major axis, and minimize the xe2x80x98reach spacexe2x80x99 along a direction orthogonal to the minor axis. It was originally conceived that the major axis would be aligned in a horizontal direction relative to a floor surface so that optical communications could occur within a collaborative workplace environment.
Prior art optical transceivers have a photodetector and an LED positioned adjacent to each other on the same plane using dedicated lenses or surfaces disposed over the photodetector and the LED. The lenses typically had a circular-shaped outer perimeter. A problem with prior art devices when using a photodetector is excessive Link Turn Around Time (LTAT) which slows the communications. An LED can transmit enough light or optical rays to saturate an adjacent photodetector, thus rendering the photodetector temporarily unable to receive optical rays. The saturated photodetector requires a predetermined amount of time (i.e., LTAT) to recover and become normalized enough to then be ready to reliably detect incoming optical rays. With prior art configurations, the communication process was required to wait for the saturated photodetector to normalize each time the adjacent LED completed a transmission cycle. A familiar example of a saturated optical sensor is a human eye that is exposed to too much light. This causes the retina to become temporarily blinded (i.e., saturated). Before the eye can once again detect images, the eye must normalize during a recovery time after the light is removed.
Therefore, it is desirable to find a solution to overcome the problem of optically isolating the photodetector from the LED to avoid saturating the photodetector when the LED is adjacent to the photodetector for maintaining continued communication by eliminating the wait or idle time while the photodetector normalizes. Some prior art methods addressed this by interposing a physical barrier between the photodetector and the LED to block light or optical rays from leaving the LED and reaching the photodetector. However, this causes a transceiver to become larger and more complicated. This is undesirable for portable computers or small-sized computing devices like laptop computers or hand-held personal digital devices which require an optical transceiver of a small size or form factor. Therefore, another objective of this invention is to configure a transceiver having a small physical size for use in portable computing devices and the like.
Maurin et al in U.S. Pat. No. 5,811,798 Sealed Photoelectric Detector dated Sep. 22, 1998, along with Isaksson in WO patent 09201 6021A Optoelectronic Component dated Feb. 27, 1991, discloses using a solid barrier that is interposed between the transmitter (emitter) and receiver (photodetector) for preventing the transmitter from radiating light or optical rays into the adjacent receiver when using the transceiver in free-space condition. Apparently, there is no concern or regard to the overall physical size of the transceiver which is an important issue if the transceiver is to be used with small-sized electronic systems nor the optical profile.
Johnson et al in U.S. Pat. No. 5,359,446 Wide-angle, High-speed, Free-space Optical Communications System dated Oct. 25, 1994 discloses using an interposing solid barrier for preventing a transmitter (emitter) from radiating light into an adjacent receiver (photodetector). This appears to be designed for a limited-space condition that is isolated from true free space by a shroud in order to achieve full duplex mode communications in which the receiver and the adjacent transmitter operate simultaneously or asynchronously. It does not address optical profiles nor appear to be capable of operation in free field conditions. It appears that the asynchronous communication occurs in a limited space within the boundaries of an opaque shroud, and does not occur within true free space or unrestricted space.
Rosenberg in U.S. Pat. No. 5,506,445 Optical Transceiver Module dated Apr. 9, 1996 discloses a structure for an ordinary optical transceiver, and does not disclose a structure that can satisfy the AIr communications standard.
The above listed prior art does not suggest how to prevent degrading a transceiver""s communication performance while satisfying limitations on size for use with a portable PC, especially when the transceiver communicates within an asymmetrically shaped optical profile. The transceiver""s communication ability may be degraded by several factors that are not addressed in combination by the prior art, such as:
(a) optical rays from an LED lens that enters into the photodetector lens because of the relative positions of the lenses with respect to each other;
(b) an LED saturating an adjacent photodetector that causes communication delays; and
(c) a photodetector lens that partially blocks the optical rays emitting from the LED lens thus creating a shadow that blocks optical rays being emitted from the LED.
To overcome these problems, the lenses could be separated further apart to keep the profiles of the emitter (LED) and receiver lenses from interfering with each other; however, the transceiver size will then be larger and thus less desirable for use in a portable PC.
Therefore, a solution should address, balance, and satisfy several technical problems in combination, such as:
(a) isolating the specific optical profiles for optimum condition of transmission and reception of optical rays;
(b) preventing a photodetector from becoming saturated by an adjacent LED, thus not allowing the communication process to idle unnecessarily;
(c) minimizing the transceiver""s package size; and
(d) communicating optical rays freely within the specified optical profiles.
The prior art does not suggest a solution for simultaneously addressing the above-mentioned problems in combination.
A lens may be used with an emitter (such as an LED) and a detector (such as a photodetector) to define the shape of the optical profile of light being emitted from or received by those devices. The profile resembles a spatial conduit having a non-contact, non-reflecting boundary in which the optical rays of communication are spatially confined while being directed to and from the emitter and detector. This spatial conduit is also called the Field-of-View (FOV). Asymmetrically shaped optical profiles were not used by computers (PCs) communicating with each other in prior art. The AIr communications standard requires the photodetector to receive optical rays and the LED to transmit optical rays within the asymmetrically shaped profile.
As will be known by those skilled in the art, an optical profile represents a spatial pathway having defined spatial boundaries which can advantageously be useful for optical communications. For example, a flashlight having an internal reflector outwardly projects a cone-shaped light beam or profile, and the space inside the cone has a density of light rays while the space outside the cone the density of light rays is much less. In reality, the transition from one region to the other is not abrupt, but rather assumes a Gaussian-shaped transition.
The present invention addresses the problems related with shadows that are created by adjacently located lenses, and saturation of the photodetector, while providing an optical transceiver configured for applications that demand a very small package size or form factor, and providing fast, reliable communication within an asymmetrically shaped optical profile.
One aspect of the present invention provides a transceiver having lenses positioned and aligned to allow the transceiver to be placed in a small-sized package, while giving the advantageous optical responsiveness for use in a limited space or footprint within computing or communication platforms, where the transceiver typically operates in half duplex mode, while maintaining capability to operatexe2x80x94without requiring further physical modificationsxe2x80x94in communication systems that operate in full duplex mode.
Another aspect of the present invention provides an optical transceiver that communicates within an asymmetrically shaped optical profile by using ellipsoidally-shaped lenses. The emitter and receiver lenses are spatially positioned with their major axes staggered so that the optical profiles of lenses do not optically interfere with each other.
Yet another aspect of the present invention provides a transceiver for receiving and transmitting optical signals within an asymmetrically shaped optical profile including:
(a) an emitter group having at least one emitter module, the emitter module having:
(i) at least one emitter element for emitting an output optical signal in response to an output electrical signal;
(ii) an emitter lens element having orthogonal major and minor axes disposed in relation to the emitter element to confine light emitted from the emitter element within the profile;
(b) a receiver group having at least one receiver module, the receiver module having:
(i) at least one receiver element for producing an input electrical signal in response to receiving an input optical signal;
(ii) a receiver lens element having orthogonal major and minor axes disposed in relation to the receiver element to confine light received by the receiver lens within the profile onto the receiver element;
(c) the emitter and receiver modules disposed on the transceiver in staggered parallel spaced relation to each other with respect to their minor axes.
Another aspect of the present invention provides a transceiver in which:
(a) the emitter group includes a number of spaced emitter modules aligned in a column along their minor axes;
(b) the receiver group includes a number of spaced receiving modules aligned in a column along their minor axes;
(c) the columns of the modules are disposed in parallel spaced relationship with each other; and
(d) the emitter modules are staggered with respect to the receiver modules in their respective columns.
Yet another aspect of the present invention provides a transceiver in which:
(a) the emitter group includes two spaced emitter modules aligned in a column along their minor axes, and the receiver group includes one receiver module; and
(b) the receiver module is staggered with respect to the emitter modules and offset therebetween.
Still another aspect of the present invention provides a communication system for receiving and transmitting optical signals within an asymmetrically shaped optical profile including:
(a) an emitter group having at least one emitter module, the emitter module including:
(i) at least one emitter element for emitting an output optical signal in response to an output electrical signal;
(ii) an emitter lens element having orthogonal major and minor axes disposed in relation to the emitter element to confine light emitted from the emitter element within the profile;
(b) a receiver group having at least one receiver module, the receiver module including:
(i) at least one receiver element for producing an input electrical signal in response to receiving an input optical signal;
(ii) a receiver lens element having orthogonal major and minor axes disposed in relation to the receiver element to confine light received by the lens within the profile onto the receiver element;
(c) the emitter and receiver modules are disposed on the transceiver in staggered parallel spaced relation to each other with respect to their minor axes.
Preferably, the present invention can be configured so that the asymmetrically shaped profile has an oblong shape when viewed in a plane parallel to the major and minor axes of the lenses, the oblong shape having an oblong major axis corresponding to the major axes of the lenses, and an oblong minor axis corresponding to the minor axes of the lenses.