JPH01269246A - Optical pick-up device - Google Patents

Abstract

PURPOSE:To prevent stray light by providing a diaphragm on a hologram element. CONSTITUTION:A diaphragm 13 is provided on a hologram element 3. By the existence of this diaphragm 13, out of an outgoing light flux 2 emitted from a light emitting element 1, it is only a normal outgoing light flux 14, which is on a line to link the light emitting element 1 and the center of a condenser lens 5, to pass through an aperture 4 and the condenser lens 5, to be reflected on an information recording carrier 6, to pass through the condenser lens 5, to be separated from the outgoing light flux on the hologram element 3 and incoming to a photo-detecting element 11. An abnormal light flux 15 not to pass through the central line even in the diaphragm 13 is not incoming to the condenser lens 5 and accordingly, the reflected light incoming to the photo- detecting element 11 can not be obtained. Namely, the stray light is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an optical pickup device for writing and reading information.

[Prior Art] Fig. 2 is a configuration diagram showing a conventional optical pickup device equipped with a hologram element. In the figure, 1 is a light emitting element, 2 is an emitted light beam from the light emitting element 1, and 3 is an emitted light and a reflected light. 4 is an aperture, 5 is a condensing lens, 6 is an information recording carrier, 7 is a focused spot formed on the information recording carrier 6, 8 is stray light generated by the hologram element 3,
9 is a focused spot of stray light 8; 10 is a reflected light beam; 11
is a light receiving element, and 12 is reflected light of stray light.

In the figure, an emitted light beam 2 emitted from a light emitting element 1 passes through a hologram element 3, is restricted by an aperture 4, and is focused onto an information recording carrier 6 by a condenser lens 5, forming a condensed spot 7. do. Next, information recording carrier 6
The light is modulated by the recorded information and reflected, and reaches the hologram element 3 via the condenser lens 5. The reflected light beam 10 separated from the emitted light beam 2 by the hologram element 3 enters the light receiving element 11 and is converted into an electrical signal, which is further utilized as an audio and video signal digital signal by a signal processing circuit (not shown).

At this time, a part of the emitted light beam 2 is bent by the hologram element 3, becomes stray light 8, enters the condenser lens 5, and forms a condensed spot 9 of the stray light on the information recording carrier 6. Furthermore, the stray light is reflected on the information recording carrier 6, becomes a reflected light beam 12 of the stray light via the condenser lens 5, and is incident on the light receiving element 11.

[Problems to be Solved by the Invention] By the way, in the above optical pickup device, the light receiving element 1
Since the presence of the stray light 8 incident on the light receiving element 1 causes deterioration of the characteristics of the light receiving element 11, there has long been a demand for a preventive measure.

The present invention has been made in order to solve the above-mentioned problems of conventional devices, and aims to provide an optical pickup device that can prevent stray light.

[Means for Solving the Problems] In order to achieve the above object, in the optical pickup device according to the present invention, the hologram element is provided with an aperture that limits the light flux.

[Function] By providing a diaphragm in the hologram element, the light beam emitted from the light emitting element will not pass through the center line of the light emitting element and the condenser lens, even if it passes through the diaphragm. Since the light beam is bent by the hologram element and does not pass through the condenser lens, generation of stray light is prevented.

[Embodiment of the Invention] FIG. 1 is a block diagram of an optical pickup device showing an embodiment of the present invention, in which numerals 1 to 11 are the same or equivalent parts as in the conventional device, and numeral 13 is an aperture.

As shown in the figure, an aperture 13 is provided on the hologram element 3. Due to the presence of this diaphragm 13, the outgoing light beam 2 emitted from the light emitting element 1 is reflected on the information recording carrier 6 via the aperture 4 and the condensing lens 5, and then passes through the condensing lens 5 again and is emitted onto the hologram element 3. What separates from the light beam and enters the light receiving element 11 is only the normal output light beam 14 located on the line connecting the centers of the light emitting element 1 and the condensing lens 5, and does not pass through the center line even if it is within the aperture 13. The abnormally emitted light beam 15 does not enter the condenser lens 5, and therefore no reflected light that enters the light receiving element 11 is obtained. In other words, no stray light is generated.

[Effects of the Invention] In the optical pickup device of the present invention, since the diaphragm is provided on the hologram element, the generation of stray light is prevented and the light receiving element can always function under optimal conditions, which is an excellent effect. Ta.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical pickup device showing an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional optical pickup device. In the figure, 1 is a light emitting element, 2 is an emitted light beam, 3 is a hologram element, 4 is an aperture, 5 is a condensing lens, 6 is an information recording carrier, 7 is a condensed spot, 8 is stray light, and 9 is a condensed spot due to stray light. , 10 is a reflected light flux, 11 is a light receiving element, 12 is a reflected stray light flux, 13 is an aperture, 14 is a normal light flux, and 15 is an abnormal light flux. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Patent Attorney Muneharu Sasaki Figure 1

Claims (1)

[Scope of Claim] An optical pickup device equipped with a hologram element, characterized in that an aperture is provided on the hologram element to prevent generation of stray light.