Monocular with adjustable magnification

A monocular with an adjustable magnification comprising:

• an object lens group (1), a prism group (2) and an eyepiece group (3) arranged in sequence along an optical axis direction;
• wherein the object lens group (1) comprises a first object lens (L11) with positive focal power, a second object lens (L12) with negative focal power, a third object lens (L13) with positive focal power, and a fourth object lens (L14) with negative focal power, wherein the first object lens, the second object lens, and third object lens are arranged in sequence along the optical axis direction from an object side to an observation side;
• wherein the eyepiece group (3) comprises a first eyepiece lens (L31) with negative focal power, a second eyepiece lens (L32) with positive focal power, a third eyepiece lens (L33) with negative focal power, and a fourth eyepiece lens (L34) with positive focal power, a fifth eyepiece lens (L35) with positive focal power, a sixth eyepiece lens (L36) with negative focal power, a seventh eyepiece lens (L37) with positive focal power, and an eighth eyepiece lens (L38) with negative focal power, wherein the first eyepiece lens, the second eyepiece lens, the third eyepiece lens, the fourth eyepiece lens, the fifth eyepiece lens, the sixth eyepiece lens, the seventh eyepiece lens, and the eighth eyepiece lens are arranged in sequence along the optical axis direction from the object side to the observation side;
• wherein the first eyepiece lens (L31) and the second eyepiece lens (L32) constitute an eyepiece compensation group (31);
• wherein the third eyepiece lens (L33), the fourth eyepiece lens (L34), the fifth eyepiece lens (L35), and the sixth eyepiece lens (L36) constitute an eyepiece variable magnification group (32);
• wherein the seventh eyepiece lens (L37) and the eighth eyepiece lens (L38) constitute an eyepiece fixed group (33);
• wherein focal lengths of lens groups satisfy the following formula:
• -
• 1
• .
• 4
• <
• F
• 3
• ⁢
• 1
• /
• F
• 3
• ⁢
• 2
• <
• -
• 0.9
• ;
• 1.2
• <
• F
• 3
• ⁢
• 3
• /
• F
• 3
• ⁢
• 2
• <
• 1.7
• ;
• wherein, F31 comprises a combined focal length of the eyepiece compensation group (31), F32 comprises the combined focal length of an eyepiece magnification group (32), and F33 comprises the combined focal length of an eyepiece fixed group (33);
• wherein the adjustable magnification comprises F1/F3 with a magnification relationship of 20<F1/F3<60;
• wherein F1 comprises the combined focal length of the object lens group (1), and F3 comprises the combined focal length of the eyepiece group (1);
• wherein the eyepiece magnification group (32) and the eyepiece compensation group (31) are configured to move closer to or farther from each other along the optical axis direction to achieve a continuous change of a magnification between 20 to 60 times.