JPH0348510Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a target incorporated into an optical radius of curvature measuring machine for measuring the base curve of a contact lens.

[Conventional technology]

In general, a contact lens curvature radius measuring machine uses an optical system in which the image plane of the target T formed by the objective lens Lo coincides with the eyepiece focal plane f, as shown in FIG. The base curve of a contact lens is measured by aligning the optical axis of a contact lens C with the reflected image of a target T, and as shown in FIG. There are two types of real images: a surface image T ₁ formed on the surface of the lens C and an spatial image T ₂ formed on the spherical surface of the contact lens C, so move the contact lens C up and down along the axis S of the optical system. The points at which the above two types of real images are obtained are visually determined, and the distance t between these two points is defined as the base curve r (also referred to as the "radius of curvature r") of the contact lens. In Figure 3, Le is the eyepiece lens, Lo is the objective lens,
E is the eye of the measurer, and Li is the illumination system.

Conventional contact lens radius of curvature measurement machines use radiation images (also called octagonal ray images) and concentric circular images as images of the target T, but when this target is used, the following images can be obtained. There's a problem.

[Problem that the invention attempts to solve]

Conventionally, the base curve of a contact lens has been measured manually by placing each contact lens on a lens holder and manually adjusting the center of the lens to approximately coincide with the center of the target image. We are positioning and observing for measurements.

However, when attempting to automate the measurement of such a base curve, a contrast detection sensor is provided at the eyepiece focal plane f instead of the observer's observing eye along the X and Y coordinate axes with the origin at the center of the focal plane f. On the other hand, it is necessary to provide a transport positioning mechanism for automatically feeding and ejecting the contact lenses to be measured to and from the lens holder in sequence, and to automate the vertical movement of the lens holder in order to create the two types of target images mentioned above.

However, in this case, if the target image of the measuring device is a radiation image or a concentric circle image as in the prior art, a problem arises in that the positioning accuracy of the contact lens must be extremely high.

This problem occurs when the center of the contact lens that is automatically transported and supplied to the lens holder deviates from the center of the target image, or when the lens is placed at an angle, causing the contact lens to move up and down for measurement. When the object actually passes through the imaging position, this position cannot be detected or becomes difficult to detect, making it difficult to maintain or improve measurement accuracy or measurement efficiency. It is.

That is, as shown in Fig. 5 A and B, if the positioning of the contact lens is inaccurate, the center Tc of the target image and the sensors S arranged along the coordinate axis
Since the origin So and the center So of the contact lens C do not match, it may be difficult or impossible to clearly detect the imaging position. In other words, the measuring device detects the contrast of the central image of the target image at the origin of the sensor group, so if the center of the lens deviates from this origin,
It is difficult to make accurate measurements.

[Means for solving problems]

Therefore, with this invention, even if there is a slight deviation between the center of the target image used in the contact lens curvature radius measuring machine and the center of the contact lens to be measured, it is possible to accurately measure the base curve in that state. The purpose of this device was to provide a target with a pattern that would make the object more visible, and its configuration was such that a contrast detection sensor was provided at the focal plane of the eyepiece along the XY coordinate axes with the origin at the center of the focal plane. A contact lens automatic radius of curvature measuring machine which sequentially feeds and discharges contact lenses into a lens holder, characterized in that the pattern of the target is arranged in a lattice-like manner on the XY coordinates. It is.

[Operation] Since the target pattern is in the form of a grid, even if the center of the pattern and the center of the contact lens do not coincide, there is no change in the arrangement of the pattern with respect to the center of the contact lens.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view showing an example of the pattern of the target of the present invention. In this figure, reference numeral 1 denotes the target body, which is formed into a disk shape from a light-transmissive plate, for example, a glass plate. 2 is a pattern drawn by printing etc. on the upper surface of this main body 1. Here, vertical and horizontal linear thin lines lx and ly are used as pattern elements, and these are arranged to form a lattice shape with equal pitch both vertically and horizontally. This constitutes an example of the target of the present invention.

In addition to the above example, this pattern may be one in which appropriate pattern elements such as dots, small circles, and small rectangles are arranged on a grid of elements.

In the target shown in Fig. 1 above, the center of the pattern is To, but even if the center Co of the contact lens C to be measured is set offset from this center To as shown in Fig. 2, the center of the pattern is To. The image of the pattern projected onto is virtually unchanged.

This means that the deviation of the center position has little effect on the electrical output due to the target image produced on the contrast sensor.

[Effect of idea]

Therefore, if the target of the present invention is used as a target for a contact lens radius of curvature measurement device,
The positioning accuracy of the contact lens to be measured can be greatly relaxed, and even in measurement with the contact lens to be measured set in place due to this relaxed accuracy, the bottom of the sensitivity of the contrast sensor, that is, a decrease in the output does not occur.

Therefore, in the target of the present invention, when the contact lens is automatically positioned to be supplied and this position is automatically moved up and down on the axis of the optical system, the distance between the reflected image of the target by the lens and the imaging position of the aerial image can be adjusted. It is extremely useful as a target for an automatic contact lens radius of curvature measuring machine that automatically measures and determines the contrast of a formed target image using an array of contrast sensors.

Of course, this target can also be used in a manual contact lens curvature radius measuring machine to obtain the same effect as described above.

As described above, the present invention is extremely useful as a target for a contact lens radius of curvature measuring device.

[Brief explanation of the drawing]

Fig. 1 is a plan view of an example of the target of the present invention, Fig. 2 is a plan view showing an example of the misaligned positional relationship between the target of the present invention and a contact lens, and Fig. 3 is an example of a conventional contact lens radius of curvature measuring device. Fig. 4 is a front view showing the optical system of the contact lens, Fig. 3 is a front view illustrating the image forming position in the contact lens radius of curvature measuring machine, and Fig. 5 A and B are the front views of the conventional contact lens curvature radius measuring machine. FIG. 3 is a plan view showing an example of misalignment between a target pattern and a contact lens. 1...Target body, 2...Pattern.

Claims (1)

[Scope of utility model registration request] An automatic radius of curvature measuring machine for contact lenses, in which a contrast detection sensor is provided on the eyepiece focal plane along an XY coordinate axis with the origin at the center of the focal plane, and contact lenses to be measured are sequentially fed and ejected into a lens holder. A target for a contact lens radius of curvature measuring machine, characterized in that the pattern of the target is arranged in a grid pattern on XY coordinates.