JPH0632605Y2 - Parallel beam parallelism measuring device - Google Patents

Description

The present invention relates to a parallel light flux parallelism measuring device, and more particularly to a parallel light flux parallelism measuring device generated by a light source for an optical disk.

(Prior Art) In an optical head for an optical disc, it is necessary to collimate light emitted from a laser diode into a parallel light flux by a collimator lens. When the parallelism of the parallel light flux is poor, the beam spot after passing through the objective lens is not well focused or the shape of the beam spot is distorted, and the performance of the optical head deteriorates.

The conventional adjustment method of the optical head is to measure the parallelism of the parallel light flux by observing the beam spot after passing the objective lens on the display monitor screen and adjust the positions of the laser diode and the collimator lens. .

(Problems to be solved by the invention) However, the parallelism measurement of the parallel light flux described above is extremely delicate and requires skill, and thus is not an easy method.

The present invention has been made in view of the above problems, and an object thereof is a parallelism measurement capable of accurately and easily measuring the parallelism of a light beam from a parallel light source including a laser diode and a collimator lens. It is to realize the device.

(Means for Solving the Problems) The present invention for solving the above problems includes a laser diode that generates laser light, a collimator lens that refracts laser light emitted from the laser diode, and the collimator lens that refracts the laser light. A pinhole plate having a plurality of pinholes for passing a part of the light beam from the laser diode, a two-dimensional position detecting element for detecting the coordinate position of the light beam passing through the pinhole plate, and this two-dimensional position detecting element A driving means for moving the light beam in the optical axis direction, and a computing device for computing the parallelism (opening angle) of the light beam from the coordinate position of the light beam detected before and after the movement of the two-dimensional position detecting element; The arithmetic unit is provided with a display section for displaying the calculation result, and while the opening angle of the luminous flux displayed on this display section is being observed, this opening angle becomes zero. In addition, the position of the collimator lens and the laser diode are adjusted.

(Operation) In the parallelism measuring device of the present invention, the two-dimensional position detecting element is moved in the optical axis direction to obtain the coordinate position of the light flux passing through the pinhole before and after the movement of the two-dimensional position detecting element, and the coordinates are calculated. The parallelism of the light flux is measured from the position.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration example of an embodiment of the present invention. In this figure, reference numeral 1 is a laser diode for generating a laser beam, and 2 is a collimator lens for collimating the laser beam emitted from the laser diode 1. The laser diode 1 and the collimator lens 2 constitute a parallel light source, and the laser diode 1 and the collimator lens 2
The parallelism of the light emitted from the collimator lens 2 can be adjusted by adjusting the distance between the and. 3 is a pinhole plate having a plurality of holes, and 4 is a two-dimensional position detecting element (PS) for detecting the position of the light flux passing through the pinhole plate 3.
D). The two-dimensional position detecting element 4 is configured to be movable in the optical axis direction, and is driven by the driving device 5. Reference numeral 6 is an arithmetic unit for obtaining the parallelism of the luminous flux based on the result of the position of the luminous flux detected by the two-dimensional position detecting element 4, and 7 is a display unit for displaying the arithmetic result of the arithmetic unit 6.

FIG. 2 is an explanatory diagram showing the relationship between the luminous flux passing through the pinhole plate 3 and the two-dimensional position detecting element 4. In this figure,
Reference numeral d denotes four pinholes provided on the pinhole plate 3. Further, when the two-dimensional position detecting element 4 is installed at the position A, the detection positions of the luminous flux are respectively (x ₁₁ , y ₁₁ ),
(X ₁₂ , y ₁₂ ), (x ₁₃ , y ₁₃ ), (x ₁₄ , y ₁₄ ), 2
When the dimensional position detecting element 4 is installed at a position B which is separated from the position A by a distance L in the optical axis direction, the light beam detection positions are (x ₂₁ , y ₂₁ ), (x ₂₂ , y ₂₂ ), (x ₂₃ ). , Y ₂₃ ),
(X ₂₄ , y ₂₄ ). The pinholes provided on the pinhole plate 3 can be shielded freely.

The operation of this embodiment will be described below with reference to FIGS.

The light emitted from the laser diode 1 and passing through the collimator lens 2 (substantially parallel light flux) is incident on the pinhole plate 3 provided with a plurality of (for example, four) pinholes. Each pinhole can freely pass and block the light flux, and each light flux passes through the pinhole one by one and reaches the two-dimensional position detecting element 4. For example, when measuring the light flux passing through the pinhole a, the other pinholes b, c, d are shielded. The coordinate position of the light flux passing through the pinhole a is measured by the two-dimensional position detecting element 4. The coordinate position when the two-dimensional position detecting element 4 is at the position A is (x ₁₁ , y ₁₁ ), and the coordinate position when the two-dimensional position detecting element 4 is driven by the driving device 5 and is at the position B is (x ₂₁ , y ₂₁ ). Similarly, the light fluxes passing through the pinholes b, c, and d are coordinate positions (x ₁₂ , y ₁₂ ), (x ₁₃ , y when the two-dimensional position detecting element is at the position A.
₁₃ ), (x ₁₄ , y ₁₄ ), and when the two-dimensional position detecting element is driven by the driving device 5 and is at the position B, coordinate positions (x ₂₂ , y ₂₂ ), (x ₂₃ , y ₂₃ ), ( x ₂₄ , y ₂₄ ) can be measured.

The arithmetic unit 6 obtains the parallelism of the light flux from the above measurement result,
It is displayed on the display unit 7. That is, the parallelism of the light beam from the collimator lens 2 can be represented by the opening angles ψx and ψy obtained from the coordinate points measured at the positions A and B. When this is expressed by an equation, ψx = {(x ₂₃ −x ₂₄ ) − (x ₁₃ −x ₁₄ )} / L ψy = {(y ₂₁ −y ₂₂ ) − (y ₁₁ −y ₁₂ )} / L Become.

For example, when the resolution of the two-dimensional position detecting element 4 is 25 μm and the distance L between the position A and the position B is 250 mm, the minimum angle ψ that can be obtained is ψ = (25 × 10 ⁻⁶ ) / (250 × 10 ^{− 3} ) = 1 × 10 ⁻⁴ [rad], and the parallelism of the light flux can be measured with this accuracy.

Therefore, while observing the opening angle ψ of the light flux displayed on the display unit 7, the positions of the collimator lens 2 and the laser diode 1 are adjusted so that the opening angle ψ becomes 0, and the light emitted from the collimator lens 2 becomes parallel light. Try to be.

As described above, by using the pinhole plate having a plurality of pinholes and the two-dimensional position detecting element movable along the optical axis, it is possible to accurately measure the parallelism of the parallel light flux.

Needless to say, the distance L may be set and measured in accordance with the required accuracy of parallelism.

(Effect of the Invention) As described in detail above, according to the present invention, a pinhole plate having a plurality of pinholes and a two-dimensional position detecting element movable along the optical axis are used. The divergence angle of the luminous flux is obtained from the detected positions of the luminous flux before and after the movement, and the parallelism of the luminous flux emitted from the laser diode and the collimator lens is measured based on this divergence angle. For this reason, it is possible to realize a parallelism measuring device that can accurately and easily measure the parallelism of the light flux from the light source configured by the laser diode and the collimator lens.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of an embodiment of the present invention, and FIG. 2 is an explanatory diagram for explaining a main part of the configuration of FIG. 1 ... Laser diode 2 ... Collimator lens 3 ... Pinhole plate, 4 ... Two-dimensional position detecting element 5 ... Driving device, 6 ... Computing device 7 ... Display unit

Claims (1)

[Scope of utility model registration request] 1. A laser diode for generating a laser beam,
A collimator lens for refracting the laser light emitted from the laser diode, a pinhole plate having a plurality of pinholes for passing a part of the light flux from the laser diode refracted by the collimator lens, and the pinhole plate A two-dimensional position detecting element for detecting the coordinate position of the light beam passing through, a driving means for moving the two-dimensional position detecting element in the optical axis direction, and a light beam detected before and after the movement of the two-dimensional position detecting element. Equipped with an arithmetic unit for calculating the parallelism (opening angle) of the light flux from the coordinate position of and the display unit for displaying the calculation result calculated by this arithmetic unit, while observing the opening angle of the light flux displayed on this display unit. The parallelism of the parallel light flux is characterized in that the positions of the collimator lens and the laser diode are adjusted so that the opening angle becomes zero. Constant apparatus.