A teleconverter lens consists essentially of, in order from the object side: a front group having a positive refractive power; and a rear group having a negative refractive power, wherein the front group and the rear group are separated from each other by the widest air space, the front group consists essentially of one positive lens having a convex surface toward the object side, and the rear group includes, in order from the object side, at least one negative lens having a concave surface toward the image side, and at least one positive lens having a convex surface toward the object side.

A teleconverter lens consists essentially of, in order from the object side: a front group having a positive refractive power; and a rear group having a negative refractive power, wherein the front group and the rear group are separated from each other by the widest air space, the front group consists essentially of one positive lens having a convex surface toward the object side, and the rear group includes, in order from the object side, at least one negative lens having a concave surface toward the image side, and at least one positive lens having a convex surface toward the object side.

An apparatus is disclosed. The apparatus may include a housing detachably couplable to a sighting device. The housing has a first opening and a second opening defining a viewing axis, and a sight shade disposed adjacent the first opening. The second opening is configured to engage an end of the sighting device. The viewing axis of the housing is coaxial with a viewing axis of the sighting device. The housing also includes at least one elongated member coupled with the housing and extending away from the second opening in a direction that is parallel with the viewing axis. The housing also includes a coupling device that is slidably coupled with the at least one elongated member, and configured to couple the at least one elongated member to the sighting device.

An apparatus is disclosed. The apparatus may include a housing detachably couplable to a sighting device. The housing has a first opening and a second opening defining a viewing axis, and a sight shade disposed adjacent the first opening. The second opening is configured to engage an end of the sighting device. The viewing axis of the housing is coaxial with a viewing axis of the sighting device. The housing also includes at least one elongated member coupled with the housing and extending away from the second opening in a direction that is parallel with the viewing axis. The housing also includes a coupling device that is slidably coupled with the at least one elongated member, and configured to couple the at least one elongated member to the sighting device.

A converter optical system includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; and a fifth lens having positive refractive power; wherein the first to fifth lenses are sequentially disposed in numerical order from the first lens to the fifth lens from an object side of the converter optical system to an image side of the converter optical system; and the fourth lens is bonded to either one or both of the third lens and the fifth lens.

A converter optical system includes a first lens having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; a fourth lens having negative refractive power; and a fifth lens having positive refractive power; wherein the first to fifth lenses are sequentially disposed in numerical order from the first lens to the fifth lens from an object side of the converter optical system to an image side of the converter optical system; and the fourth lens is bonded to either one or both of the third lens and the fifth lens.

An apparatus is disclosed. The apparatus may include a housing detachably coupleable to an end of a sighting device. The housing may include a channel protruding from a side of the housing. The apparatus may include a one-way mirror disposed inside the housing. The one-way mirror may be positioned to allow an image from the sighting device to pass through the one-way mirror and reflect the image from the sighting device through the channel. The apparatus may include a mounting plate coupled to the housing. The mounting plate may include one or more adjustment bars that may be engageable with a visual recording device.

An apparatus is disclosed. The apparatus may include a housing detachably coupleable to an end of a sighting device. The housing may include a channel protruding from a side of the housing. The apparatus may include a one-way mirror disposed inside the housing. The one-way mirror may be positioned to allow an image from the sighting device to pass through the one-way mirror and reflect the image from the sighting device through the channel. The apparatus may include a mounting plate coupled to the housing. The mounting plate may include one or more adjustment bars that may be engageable with a visual recording device.

This disclosure describes an afocal attachment that allows for alteration of received electromagnetic radiation (or “light”) prior to entry into the telescope. For example, a rifle scope may have a base magnification of 2x, and the afocal attachment may allow magnification of a received image at levels ranging from 2x to 4x. In this example, the entire telescope system with the afocal attachment installed will have an overall magnification of 4x to 8x. In another example, the magnification of the telescope can be increased, transforming a telescope with a 4x magnification into a telescope with a higher effective magnification. In some instances the afocal attachment's optical axis can be configured to permit independent adjustment, allowing for easy removal and reinstallation of the afocal attachment without a need to re-adjust the telescope itself.

This disclosure describes an afocal attachment that allows for alteration of received electromagnetic radiation (or “light”) prior to entry into the telescope. For example, a rifle scope may have a base magnification of 2x, and the afocal attachment may allow magnification of a received image at levels ranging from 2x to 4x. In this example, the entire telescope system with the afocal attachment installed will have an overall magnification of 4x to 8x. In another example, the magnification of the telescope can be increased, transforming a telescope with a 4x magnification into a telescope with a higher effective magnification. In some instances the afocal attachment's optical axis can be configured to permit independent adjustment, allowing for easy removal and reinstallation of the afocal attachment without a need to re-adjust the telescope itself.