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Exhibit 4.1  

 
 

AMENDMENT TO RIGHTS AGREEMENT    
  

        This Amendment (this "Amendment") to Rights Agreement (the "Rights Agreement") is effective as of May 9, 2002 by and between Quidel Corporation, a Delaware
corporation (the "Company") and American Stock Transfer & Trust Company, a New York corporation (the "Rights Agent"). Capitalized terms used herein but not defined herein shall have their
defined meanings set forth in the Rights Agreement. 

 
 

BACKGROUND    
  

        A.    The
Company and the Rights Agent entered into the Rights Agreement effective as of December 31, 1996. 

        B.    The
Rights Agreement provides that in certain circumstances the acquisition by a person of 15% or more of the shares of Common Stock will cause, in certain circumstances,
the exercisability of the Rights. 

        C.    The
parties desire to amend the terms of the Rights Agreement to permit the beneficial ownership of up to one share less than 20% of the then outstanding shares of Common
Stock by Kopp Investment Advisors, Inc. ("KIA"), LeRoy Kopp, an individual ("Kopp"), and their Affiliates (collectively, "Kopp Affiliates") under circumstances described in that certain
Standstill Agreement dated as of May 9, 2002, by and among KIA, Kopp and the Company. 

 
 

AGREEMENT    
  

        NOW, THEREFORE, the parties hereby agree as follows: 

        1.    Section 1(o)
is hereby deleted in its entirety and the following is inserted in lieu thereof: 

        (o)  "EXEMPT
PERSON" shall mean the Company, any Subsidiary of the Company, any employee benefit plan or employee stock plan of the Company or any Subsidiary of the Company,
or any person or entity organized, appointed, or established by the Company or any Subsidiary of the Company, for or pursuant to the terms of any such plan. "Exempt Person" shall also mean Kopp
Investment Advisors, Inc. ("KIA") and its Affiliates and Associates; provided, that, neither KIA nor any of its Affiliates and Associates shall be an Exempt Person at and after such time KIA,
together with its Affiliates and Associates (i) is the Beneficial Owner of 20% or more of the shares of Common Stock then outstanding, (ii) is the Beneficial Owner of 15% or more of the
shares of Common Stock then outstanding and is not permitted to file a Schedule 13G, in lieu of Schedule 13D, pursuant to the Exchange Act and the rules promulgated thereunder,
(iii) is the Beneficial Owner of less than 14% of the shares of Common Stock then outstanding at any time after once having been the Beneficial Owner of 15% or more of the shares of Common
Stock then outstanding, or (iv) is the Beneficial Owner of less than 15% of the shares of Common Stock then outstanding as of any date after August 1, 2002." 

        2.    Except
as expressly set forth in this Amendment, all other terms of the Rights Agreement shall remain in full force and effect. 

        3.    This
Amendment shall be governed by and construed in accordance with the laws of the State of Delaware applicable to contracts made and to be performed entirely within
such State. 

        4.    This
Amendment may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed to be an original, and all such counterparts
shall together constitute but one and the same instrument. 

        5.    Certification
to Rights Agent. Pursuant to the provisions of Section 27 of the Rights Agreement, in connection with this Amendment, the undersigned officer of the
Company certifies that this Amendment complies with the terms of Section 27. 

[Signature page follows]  

        IN
WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly executed as of the day and year first above written. 

	 	 	The "Company":
	

 	
 	

QUIDEL CORPORATION
	

 	
 	

By:	
 	

/s/  S. WAYNE KAY      

	 	 	Name:	 	S. Wayne Kay

	 	 	Title:	 	President & CEO

	

 	
 	

The "Rights Agent":
	

 	
 	

AMERICAN STOCK TRANSFER & TRUST COMPANY
	

 	
 	

By:	
 	

/s/  HERBERT J. LEMMER      

	 	 	Name:	 	Herbert J. Lemmer

	 	 	Title:	 	Vice President

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AMENDMENT TO RIGHTS AGREEMENT

BACKGROUND

AGREEMENTQuickLinks
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Exhibit 10.1    
  

March 14,
2002 

Mr. Douglas
Crocker II

Chief Executive Officer

Equity Residential Properties Trust

Two North Riverside Plaza

Chicago, IL 60606 

Dear
Doug, 

This
letter will outline the terms and conditions upon which I am enthusiastically prepared to join Equity Residential Properties Trust as President and a member of the Board of Trustees. My first day
of employment will be April 8, 2002. 

As
I mentioned to you, it is important to me that I fit into the Company's compensation system and that my salary, bonus and long-term incentive package be no less than Gerry Spector's for
the year 2002. Specifically, my compensation for 2002 will be as follows: 

	A.
	My annual salary shall be $550,000, and my cash bonus, payable in January 2003, shall be $750,000, or such other higher amount
approved by the Compensation Committee. Effective as of the date of this letter, I will also receive the following long-term compensation awards as a signing bonus: 41,361 options award,
8,272 restricted shares award and 4,595 performance share units award. I will also receive in January of 2003, if I am employed by the Company as of that time, at the same time as the other senior
executives receive their 2002 long term incentive grants, the following long-term compensation awards, or such other higher amounts approved by the Compensation Committee, for services
rendered in 2002: 124,083 options award, 24,816 restricted shares award and 13,787 performance share units award (collectively the "January 2003 Grants"). These awards are issued subject to the
terms of the Company's Share Option and Share Award Plan.

	B.
	The options are granted at the fair market value of the Company's common shares at the date of grant, are granted for a period of ten
years and vest over a period of three years, subject to continuous employment, at a rate of one third of such grant each year.

	C.
	I have the option to convert any portion of my restricted share award (thereby reducing that award) into an additional option award (at
a 5-1 ratio) within fifteen days of the grant date. The restricted shares vest in full on the third anniversary of the grant date, subject to continuous employment. Distributions are paid
on these restricted shares at the same rate as on unrestricted common shares. 

I
understand that my employment is subject to my signing the Company's arbitration agreement and the Company's approval of my criminal background investigation and drug test prior to my first day of
employment. My benefits package (including Change of Control Agreement, medical, vacation etc.) will be the same as yours, but excluding your Deferred Compensation Agreement and Share Distributions
Agreement. While I cannot immediately obtain the benefits of the Company's 401(k) plan matching and profit sharing contributions, I understand that I will immediately be eligible to join the Company's
deferred compensation plan known as the SERP. 

I
will assume the additional responsibility of Chief Executive Officer on or before December 31, 2002, with you becoming Vice Chairman. If I do not become CEO by that date, for any reason other
than I have left the company voluntarily, or the reasons hereafter delineated, all my stock options, restricted stock and performance units granted in 2002, as well as the January 2003 grants,
(which shall be deemed granted as of the termination of my employment) would vest, with the performance units vesting at the 100% target level. I would also receive severance pay equal to three times
my 2002 annual salary and target bonus, (prorated at 9/12) unless my employment is terminated because of my death or disability, in which case I would receive only a prorated bonus for
the year as well as any proceeds payable under the Company's standard employee life insurance and disability programs. I also 

acknowledge that any benefits due me are subject to my execution of an appropriate severance release, and upon the unlikely event of my termination of employment for Cause, as defined in the
Company's standard Change in Control Agreement, I would not be entitled to any accelerated vesting of awards or other severance payments. 

At
the time I become the CEO, the Compensation Committee will review my compensation program. As part of that review, my compensation program (salary, bonus potential and long term incentives) will be
increased to a dollar level approaching your 2002 program (excluding your extraordinary grant of 450,000 options in January 2002). The percentage of each long term incentive will be allocated
in accordance with the Company's allocation for its senior executives. In addition, a 10 year deferred compensation agreement (based on my base salary and similar in concept to your deferred
compensation agreement), will be put in place which will give credit to my start date. My new compensation program will be documented in a new employment agreement which will also contain appropriate
severance language. I will also move into your office and we will find you suitable space in the building. 

I
will become a member of the Board of Trustees as of the date the Compensation Committee signs this letter. In accordance with the Company's policy, I hereby agree to submit my resignation as Trustee
upon the termination of my employment with the Company for any reason. 

I
am currently on three for-profit boards. I will reduce this number to two by August, 2002, but will be able to maintain two directorships. 

Once
the Board has approved the terms of this letter, would you please sign in the space below. I look forward to joining the Equity Residential team and contributing to the future growth and
profitability of the Company. 

	Sincerely,	 	 
	 	 	 	 	 
	BY:	 	/s/  BRUCE W. DUNCAN      
 Bruce W. Duncan	 	 

        [Signatures follow on Next Page] 

Agreed
and Accepted this 14th day of March, 2002 

	Equity Residential Properties Trust	 	 
	 	 	 	 	 
	By:	 	/s/  DOUGLAS CROCKER II      
 Douglas Crocker II
 Chief Executive
Officer	 	 

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Exhibit 10.1

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